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Protein Arginine Methyltransferase 4 (PRMT4) mediates lymphopenia in experimental sepsis. Yandong Lai 1# , Xiuying Li 2# , Tiao Li 1 , Yan Chen 3 , Chen Long 4 , Toru Nyunoya 2 , Kong Chen 1 , Georgios D. Kitsios 1 , Seyed Mehdi Nouraie 1 , Yingze Zhang 1 , Bryan J. McVerry 5 , Janet S. Lee 6 , Rama K. Mallampalli 7# , and Chunbin Zou 8# *. 1: Division of Pulmonary, Allergy, Critical Care Medicine, Department of Medicine, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA. 2: Division of Pulmonary, Allergy, Critical Care Medicine, Department of Medicine, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA; Veterans Affairs Pittsburgh Healthcare System, Pittsburgh, PA, USA. 3: Division of Pulmonary, Asthma, Critical Care Medicine, Department of Medicine, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA; Current address: Department of Respiratory diseases, The Second Xiangya Hospital, Central South University, Changsha, Hunan, China. 4. Division of Pulmonary, Asthma, Critical Care Medicine, Department of Medicine, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA; Current address: Department of Minimally Invasive Surgery, The Second Xiangya Hospital, Central South University, Changsha, Hunan, China. 5: Division of Pulmonary, Allergy, Critical Care Medicine, Department of Medicine; Vascular Medicine Institute, School of Medicine; Department of Environmental and Occupational Health, Graduate School of Public Health, University of Pittsburgh; Pittsburgh, PA; 6: Division of Pulmonary, Allergy, Critical Care Medicine; Vascular Medicine Institute, University of Pittsburgh, Pittsburgh, PA, USA 7: Division of Pulmonary, Allergy, Critical Care Medicine, Department of Medicine, University of Pittsburgh School of Medicine, Pittsburgh, PA; Department of Medicine, Ohio State University College of Medicine, Columbus, OH, USA. 8: Division of Pulmonary, Allergy, Critical Care Medicine, Department of Medicine, School of Medicine; Department of Environmental and Occupational Health, Graduate School of Public Health, University of Pittsburgh; Veterans Affairs Pittsburgh Healthcare System, Pittsburgh, PA, USA. #: those authors equally contributed to the study. *: To whom correspondence should be addressed: Chunbin Zou, MD, PhD., Pulmonary, Allergy and Critical Care Medicine, Montefiore UH NW628, 3459 Fifth Avenue, The University of Pittsburgh, Pittsburgh, PA 15213 Tel.: (412)-624-4404; E-mail: [email protected]

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  • Protein Arginine Methyltransferase 4 (PRMT4) mediates lymphopenia in experimental sepsis.

    Yandong Lai1#, Xiuying Li2#, Tiao Li1, Yan Chen3, Chen Long4, Toru Nyunoya2, Kong Chen1, Georgios D.

    Kitsios1, Seyed Mehdi Nouraie1, Yingze Zhang1, Bryan J. McVerry5, Janet S. Lee6, Rama K. Mallampalli7#,

    and Chunbin Zou8#*.

    1: Division of Pulmonary, Allergy, Critical Care Medicine, Department of Medicine, University of

    Pittsburgh School of Medicine, Pittsburgh, PA, USA.

    2: Division of Pulmonary, Allergy, Critical Care Medicine, Department of Medicine, University of

    Pittsburgh School of Medicine, Pittsburgh, PA, USA; Veterans Affairs Pittsburgh Healthcare System,

    Pittsburgh, PA, USA.

    3: Division of Pulmonary, Asthma, Critical Care Medicine, Department of Medicine, University of

    Pittsburgh School of Medicine, Pittsburgh, PA, USA; Current address: Department of Respiratory

    diseases, The Second Xiangya Hospital, Central South University, Changsha, Hunan, China.

    4. Division of Pulmonary, Asthma, Critical Care Medicine, Department of Medicine, University of

    Pittsburgh School of Medicine, Pittsburgh, PA, USA; Current address: Department of Minimally Invasive

    Surgery, The Second Xiangya Hospital, Central South University, Changsha, Hunan, China.

    5: Division of Pulmonary, Allergy, Critical Care Medicine, Department of Medicine; Vascular Medicine

    Institute, School of Medicine; Department of Environmental and Occupational Health, Graduate School

    of Public Health, University of Pittsburgh; Pittsburgh, PA;

    6: Division of Pulmonary, Allergy, Critical Care Medicine; Vascular Medicine Institute, University of

    Pittsburgh, Pittsburgh, PA, USA

    7: Division of Pulmonary, Allergy, Critical Care Medicine, Department of Medicine, University of

    Pittsburgh School of Medicine, Pittsburgh, PA; Department of Medicine, Ohio State University College of

    Medicine, Columbus, OH, USA.

    8: Division of Pulmonary, Allergy, Critical Care Medicine, Department of Medicine, School of Medicine;

    Department of Environmental and Occupational Health, Graduate School of Public Health, University of

    Pittsburgh; Veterans Affairs Pittsburgh Healthcare System, Pittsburgh, PA, USA.

    #: those authors equally contributed to the study.

    *: To whom correspondence should be addressed:

    Chunbin Zou, MD, PhD., Pulmonary, Allergy and Critical Care Medicine, Montefiore UH NW628, 3459

    Fifth Avenue, The University of Pittsburgh, Pittsburgh, PA 15213 Tel.: (412)-624-4404; E-mail:

    [email protected]

    mailto:[email protected]

  • The authors declare no interest conflict with this manuscript.

    Key words: T cell, cell death, PRMT4, FBXO9, ubiquitin proteasome degradation, immunosuppression,


    Running title: Impaired PRMT4 stability causes T cell death.

  • Abstract

    One hallmark of sepsis is a reduced number of lymphocytes, termed lymphopenia, that occurs from

    decreased lymphocyte proliferation or increased cell death contributing to immune suppression.

    Histone modification enzymes regulate immunity by epigenetically modulating chromatin architecture,

    however, the role of these enzymes in lymphopenia remains elusive. In this study, we identified that a

    chromatin modulator Protein Arginine N-methyltransferase 4/Coactivator-Associated Arginine

    Methyltransferase 1 (PRMT4/ CARM1) that is elevated systemically in septic patients and experimental

    sepsis, and is crucial for inducing T-lymphocyte apoptosis. An E3 ubiquitin ligase SCFFBXO9 docks on

    PRMT4 via a phosphodegron to ubiquitinate the protein at K228 for ubiquitin proteasomal degradation.

    High PRMT4 expression resulted from reduced levels of SCFFBXO9 that led to increased lymphocyte cell

    death after Escherichia coli or lipopolysaccharide (LPS) exposure. Ectopic expression of PRMT4 protein

    caused substantial lymphocyte death via caspase 3 mediated cell death signaling, and knockout of

    PRMT4 abolished LPS mediated lymphocyte cell death. PRMT4 inhibition with a small molecule

    compound attenuated lymphocyte death in complementary models of sepsis. These findings

    demonstrate a previously uncharacterized role of a key chromatin modulator in lymphocyte survival that

    may shed light on devising unique therapeutic modalities to lessen severity of septic


  • Introduction

    Immunosuppression, i.e. “immune paralysis”, is one sepsis hallmark characterized by inhibited immune

    responses to microbial infection that also occurs in chronic infection and cancer. Typical features of

    immunosuppression include a reduced population of immune cells, exhaustion and dysfunction of cell

    immunity, suppression of pro-inflammatory factor release, or an increase in anti-proinflammatory factor

    release (1-5). Immunosuppression is clinically manifested in patients by chronic or recurrent bacterial

    and viral infections, or acute infections with opportunistic pathogens leading to sepsis (6-10).

    Lymphopenia has emerged as a prominent feature in septic patients that renders a poor prognosis. So

    far, studies have revealed that multichannel signal pathways including programmed cell death 1 (PD1),

    tumor necrosis factor receptor (TNFR), IL-7, and IL-10 may be important factors in septic

    immunosuppression (1, 3, 6, 11-15). Gram-negative bacteria derived LPS can induce apoptosis in NK

    cells, B cells, T cells, and dendritic progenitor cells (16). Further, LPS-tolerance remarkably contributes

    to mortality in polymicrobial septic models (17, 18). In addition, selective reprogramming of gene

    expression substantially affects survival rates in the LPS tolerance model (19-21). Yet, the underlying

    molecular mechanism(s) in septic immunosuppression remains to be defined.

    Epigenetics governs DNA accessibility and concomitantly coordinates with transcriptional factors to

    control lymphocyte development, lineage differentiation, and maturation (22-27). Epigenetic alterations

    occur in multi-organ failure, animal models of sepsis, and in critically ill patients (28-32). Bacterial

    infection regulates behavior of epigenetic enzymes to reprogram host immune defenses (33-36).

    Although epigenetics is crucial to the pathogenesis of immunosuppression as blockade of programmed

    cell death protein 1 (PD1) does not reverse the epigenetic changes in exhausted T cells in chronic viral

    infection animal models suggesting a role for other effectors that may be linked to the pathobiology of

    immunosuppression (37). Interestingly, mRNA levels of several histone deacetylases are increased in

    preclinical sepsis models (38). Histone H3K27 methylation has been previously implicated as an

    epigenetic mark in septic immunosuppression (39). Nevertheless, our understanding of epigenetic

    regulation in sepsis is limited as mechanisms are poorly described.

    PRMT4, a type I methyltransferase enzyme belonging to at least eleven members in the protein arginine

    methyltransferase family, regulates crucial life processes including gene transcription, proliferation, RNA

    splicing, and development (40-44). PRMT4 catalyzes the addition of mono- or asymmetric arginine

    residues to the guanidino nitrogens of arginyl residues in histones and non-histone protein substrates.

    Coordination with the action of histone acetyltransferases p300 and p160, PRMT4 dependent

    asymmetric dimethylation of histone H3 at Arg-17 (H3R17me2a) results in transcriptional activation

    (45). PRMT4 proteins are aberrantly expressed in a number of cancer cells including breast, colorectal,

    and prostate cancers, and its high level is correlated with a poor prognosis in breast cancer patients (46).

    PRMT4 promotes cellular proliferation by binding to the promoter region to enhance cell cycle related

    CDK2 gene transcription in breast and prostate cancer cells (47). PRMT4 catalyzes methylation of a

    range of non-histone proteins including p300 to exert its diverse biological functions in NF-B mediated

    inflammation, in p53 related signal transduction, and in the mRNA maturation process (41). A recent

    study revealed that PRMT4 catalyzes methylation of more than 130 substrates in breast cancer cells

  • (48). Knockout of PRMT4 in mice leads to neonatal death and developmental defects in the respiratory

    system, reduced percentage of CD4-CD8 double negative T cells, and a block of thymocyte development

    in mice (49-51). However, how bacterial pathogens reprogram PRMT4 at the protein level to regulate

    lymphocytes is not fully understood.

    The ubiquitin proteasome system degrades most cellular proteins in living cells, and at times in

    coordination with the gene transcriptional machinery. Ubiquitination proceeds in an enzymatic cascade,

    in which the final step involves an E3 ubiquitin ligase that recognizes a protein substrate to catalyze

    ligation of ubiquitin to the substrate. This process often results in substrate disposal within the

    proteasome. Among E3 ubiquitin ligases, a family of SCF (Skp1-Cullin1-Fbox) E3 proteins have been

    linked to bacterial infection and host defense (26, 34, 35, 52-54). Interestingly, the F-box protein FBXO9,

    a component of SCF-FBXO9 E3 ligase complex, was identified in a pooled RNAi screen as LPS-responsive in

    the context of IL-6 production to regulate innate immunity (55). FBXO9 may be associated with patient

    survival in multiple myeloma, is linked to adipocyte development, and targets peroxisome proliferator-

    activated receptor gamma for degradation (56-59). Aside from these studies, our understanding of this

    E3 ligase subunit is limited, particularly as it relates to sepsis.

    In this study, we identified that microbial factors (i.e. endotoxin) increase PRMT4 expression, by

    extending its cellular protein lifespan thereby inducing lymphocyte death and modulate host survival in

    experimental sepsis. Our data show that bacterial pathogens down-regulate expression of an E3

    ubiquitin ligase, SCF-FBXO9 that targets PRMT4 for its elimination in cells. Further, we observe that PRMT4

    exerts an undescribed function by triggering lymphocyte death and by screening putative small molecule

    inhibitors of PRMT4, we identified that one compound, TP064, specifically attenuates lymphocyte cell

    death and protects mice after LPS lung injury and in polymicrobial sepsis.


    Gram-negative bacterial derived endotoxin increases PRMT4 protein expression.

    We identified that E. coli derived LPS increased PRMT4 protein levels in human lymphoma Jurkat T cells

    (Fig. 1A). LPS-mediated PRMT4 accumulation appeared in a concentration-dependent manner in the

    cells. PRMT4 mRNA levels as assayed by quantitative reverse transcription- polymerase chain reaction

    (qRT-PCR) showed no remarkable differences in LPS treated and untreated Jurkat cells (Fig. 1B). Live E.

    coli increased PRMT4 cellular concentrations in Jurkat cells (Fig. 1C). To assess clinical relevance, we

    observed that PRMT4 was barely detected in the de-identified human lung tissue samples, but protein

    levels were higher in infected lung tissue samples (Fig. 1D). Further, when we conducted PRMT4

    immunoblotting in human peripheral blood leukocytes, PRMT4 protein levels from septic patients were

    substantially higher compared to that of normal leukocytes (Fig. 1E). Prmt4 protein levels were

    remarkably higher in polymicrobial infected mouse sera as compared to that of untreated control mice

    (Fig. 1F). Finally, PRMT4 protein levels were substantially higher in plasma from septic patients as

    compared to that without sepsis (Fig. 1G, Table 1). Hence, these data suggest that PRMT4 expression is

    induced in human lymphoma Jurkat cells in response to bacterial pathogen and PRMT4 levels are

  • increased during sepsis in vivo. In addition, bacteria elevate PRMT4 protein levels possibly by impairing

    its native pathway for protein degradation.

    PRMT4 is a labile protein degraded by the SCFFBXO9 E3 ubiquitin ligase.

    The availability of a specific protein in the cells is the result of dynamic homeostasis between its gene

    transcription rate, translational efficiency, and rate of protein decay. Our published studies show that

    PRMT4 is a labile protein (t½ ≈ 3.5 h) degraded via the ubiquitin proteasomal pathway in lung epithelial

    cells (60). However, little is known about the molecular mechanism of PRMT4 protein degradation.

    Results show that the half-life of PRMT4 protein is approximately 3.5 h in Jurkat T cells (Fig. 2A, B).

    PRMT4 degradation was via the proteasome, but not the lysosome, as the proteasome inhibitor MG132

    but not the lysosome inhibitor leupeptin accumulated PRMT4. Proteins degraded via the proteasome

    are in general poly-ubiquitinated and ubiquitin could be a limiting factor for protein degradation in a

    specified cellular compartment. Ectopic expression of ubiquitin accelerated PRMT4 turnover in a

    ubiquitin-dependent manner (Fig.2C). As shown before in epithelia (60), results from

    immunoprecipitation (IP) studies showed that PRMT4 was also poly-ubiquitinated in lymphocytes (Fig.

    2D, upper panel). By screening a library of SCF-E3 ubiquitin ligases, we identified that SCFFBXO9 specifically

    degrades PRMT4 (Fig. 2E). Further, PRMT4 protein was degraded in an FBXO9 plasmid concentration

    dependent manner (Fig. 2F, upper panels). As a control, FBXO24, another F-box protein, did not degrade

    PRMT4 (Fig. 2F, lower panels). IP studies showed that FBXO9 protein associates with PRMT4, as do the

    SCF complex components Skp1 and Cullin1 (Fig. 2G). Moreover, knockdown (Kd) of FBXO9 with small

    hairpin RNA (shRNA) stabilized PRMT4 as compared with that of a scramble shRNA control (Fig. 2H).

    Overall, these data indicate that PRMT4 is specifically targeted for its cellular disposal by the SCFFBXO9

    ubiquitin proteasomal machinery.

    SCFFBXO9 ubiquitinates PRMT4 at K228.

    We next fine mapped the ubiquitination site (s) within PRMT4. We generated and expressed truncated

    PRMT4 constructs in cells to examine protein degradation of the truncations (Fig. 3A). Cellular

    expression of constructs harboring carboxyl terminal deletions resulted in PRMT4 accumulation

    suggesting that molecular signatures that mediate protein disposal are not localized within the

    fragments (Fig. 3B, left panels). In contrast, deletion of the NH2-terminal 150 amino acids (aa) resulted in

    lack of PRMT4 accumulation (Fig. 3B, right panels), suggesting that aa100-150 contains a degradation

    element. We analyzed the sequence and found that there was no ubiquitin acceptor lysine residue in

    the aa100-150, but a nearby lysine residue K228 resided in the truncation mutant containing aa100-608.

    We tested if K228 is a ubiquitin acceptor site. As compared with that of wild type (WT) PRMT4 and other

    mutants, a K228A mutant was stable from proteasomal degradation (Fig. 3C, D). The K228A mutant was less

    ubiquitinated as compared with that of WT PRMT4 (Fig. 3E). In addition, mutation of K228 abrogated

    FBXO9 mediated PRMT4 degradation (Fig. 3F). These data suggest that K228 may be one authentic

    SCFFBXO9 catalyzed ubiquitin acceptor site.

    SCFFBXO9 recognizes a PRMT4 phosphodegron

  • As SCF E3 ubiquitin ligases often interact with phosphorylated substrates, we next studied the FBXO9

    docking site within PRMT4. We focused on the NH2-terminus because the above studies suggested that

    aa100-150 contains a degradation element, possibly an E3 ligase docking site. Results from in vitro pull-

    down assays showed that deletion of NH2-terminal 150 aa impairs PRMT4 and FBXO9 binding (Fig. 4A).

    We further fine mapped the docking site for FBXO9 within PRMT4 by pull-down assays (Fig. 4B, C). Pull

    down results showed that amino acids after aa131 were critical for FBXO9 binding. We analyzed the

    sequence and identified a phosphorylation motif in this region: 132-TxxxS (Fig. 4D, upper panel, x

    donates any amino acid). To test if this motif is a potential phosphodegron, we substituted T132 and S136

    with a cysteine to mimic dephosphorylation or introduced an aspartic acid at T132 to mimic a

    phosphorylation site. Pull down results suggest that a dephosphorylated T132 and phosphorylated S136

    sites constituted an optimal FBXO9 binding motif constituting a phosphodegron for E3 SCF ligase

    interaction (Fig. 4D, E). Consistent with these observations, our recent published study showed that

    glycogen synthase kinase beta (GSK-3β)-mediated T132 phosphorylation stabilized PRMT4 (60). We

    further tested the protein stability with these mutations. T132C and S136D mutants degraded faster than

    that of WT PRMT4. A S136C mutant displayed greater protein stability. T132D and T132AS136A double mutants

    completely stabilized the protein from degradation. However, a T132CS136D PRMT4 variant when

    expressed in cells degraded most rapidly (Fig. 4F, G). In all, these data indicate that SCFFBXO9 engages a

    phosphodegron 132-TdxxxSp to ubiquitinate PRMT4 at K228.

    LPS induced PRMT4 promotes caspase 3 activation in lymphocytes.

    We next assessed a potential pathophysiological role for elevated PRMT4 after bacterial infection.

    PRMT4 appeared to be endotoxin-responsive, as LPS increased PRMT4 protein levels in T cell-like Jurkat

    cells, in human infected lung tissues, and in human peripheral blood leukocytes and plasma from septic

    patients (Fig. 1). PRMT family members regulate apoptosis as PRMT2 inhibits NF-B signaling and

    promotes apoptosis in mouse embryo fibroblasts (61). PRMT4 expression induced by high-glucose

    loading triggers apoptosis of human retinal pigment epithelial cells via H3R17 dimethylation (62) Thus,

    we tested if actions of LPS on lymphocyte death are mediated by PRMT4 through its E3 ligase, SCFFBXO9.

    We first studied cell death using activated caspase 3 as a marker in a variety of cell types including Jurkat

    cells, mouse splenic T cells, and human peripheral blood pan-T cells after 6 h of LPS stimulation. As

    predicted, caspase 3 was activated in all of these cells, and its activation occurred in an LPS

    concentration dependent manner (Fig. 5A-C, second upper panels). Notably, LPS down-regulated FBXO9

    protein variably in all the tested cells, suggesting a widespread (shared) mechanism whereby LPS

    stabilizes PRMT4 in cells via depletion of SCFFBXO9 E3 ubiquitin ligase (Fig. 5A-C, second lower panels). To

    understand the potential role(s) of PRMT4 in caspase 3 cleavage in T cells, we ectopically expressed

    PRMT4 in Jurkat cells. Immunoblotting results showed that PRMT4 ectopic expression was sufficient to

    activate caspase 3 in Jurkat cells (Fig. 5D). Caspase 3 activation occurred in a PRMT4 plasmid

    concentration-dependent manner. We then generated PRMT4 knockout (KO) Jurkat cells using

    CRISPR/Cas9 to test our observations. Immunoblotting results showed that PRMT4 was completely

    depleted in stable KO cells (Fig. 5E). KO of PRMT4 blocked LPS-mediated caspase 3 activation to baseline

    levels (Fig. 5F). In contrast, ectopic expression of PRMT4 promoted LPS-induced caspase 3 activation

    (Fig. 5G). Results from immunoblotting analysis of the isolated mouse splenic T-cells showed that

    expression of PRMT4 promotes LPS-induced caspase 3 activation, and depletion of PRMT4 by shRNA

    substantially blocks LPS-induced caspase 3 activation (Fig. 5H). To confirm the role of FBXO9 in PRMT4













  • mediated caspase 3 activation, we depleted FBXO9 in Jurkat cells by shRNA. Immunoblotting results

    showed that depletion of FBXO9 increased PRMT4 mediated caspase 3 activation and this activation is

    ablated in PRMT4 KO cells (Fig. 5I). Thus, these data suggest that LPS increases PRMT4 expression

    possibly via down-regulation of FBXO9, thereby facilitating the methyltransferase to trigger caspase 3

    signaling in lymphocytes.

    PRMT4 depletion or chemical inhibition reduces lymphocyte cell death.

    To explore the function of LPS-mediated PRMT4 elevation and subsequent caspase 3 activation, we

    measured lymphocyte apoptosis. We conducted Annexin V flow-cytometry to confirm the role of PRMT4

    in LPS-mediated early stage T cell death. Flow-cytometry results showed that the baseline levels of cell

    death were similar in PRMT4 KO Jurkat cells (8.19% and 8.03%) as compared to that of non-targeted

    cells (7.86%). LPS treatment substantially promoted cell death in non-targeted cells (26.65%) but not in

    PRMT4 KO cells (10.47% and 8. 31%). Interestingly, PRMT4 overexpression promoted Jurkat cell death

    (19.75%) and augmented LPS-induced cell death (41.78%) (Fig. 6A, B). To confirm this observation, we

    determined the cell viability in LPS treated mouse splenic lymphocytes. As predicted, LPS did not affect

    cell survival in PRMT4 depleted mouse splenic T-cells but remarkably reduced cell survival in PRMT4

    overexpressed mouse splenic T-cells (Fig. 6C). Since LPS increases PRMT4 protein levels that induces T

    cell death, we assessed if a PRMT4 small molecule inhibitor(s) might suppress T cell death. We first

    screened commercially available PRMT4 inhibitors in LPS treated Jurkat cells to test if the inhibitor(s)

    might inhibit caspase 3 activation. Among the inhibitors screened, a selective and cell active PRMT4

    inhibitor TP064 (MedKoo Biosciences, Inc. Cat#: 407418) efficiently and most consistently inhibited

    caspase 3 activation at a concentration of ~40 nM (Fig. 6D); TP064 concentration of ~ 10 nM effectively

    inhibited PRMT4 mediated histone H3 arginine methylation data not shown). Further, experimental

    results suggest that TP064 can block LPS mediated caspase 3 activation at both 25 nM and 50 nM in

    mouse splenic T cells (Fig. 6E). These studies link PRMT4 to endotoxin-induced lymphocyte death and

    showcase the ability of a PRMT4 specific small molecule inhibitor to effectively antagonize endotoxin-

    induced lymphocyte death signaling.

    PRMT4 mediates splenic lymphocyte death in experimental acute lung injury.

    To test our hypothesis in animal models, we assessed PRMT4 in an LPS lung injury mice model. We

    overexpressed PRMT4 or knocked down PRMT4 using lentiviral constructs (1×107 cfu/mouse,

    intratracheal [i.t.] administration) in mice (C57BL/6J) for 14 d. LPS (5 mg/kg, i.t. in PBS buffer) was

    administrated (i.t.) into mice for 24 h. Prior to the lentivirus administration, we administered a droplet

    of lysoPC (20 L, diluted 10 times in PBS, i.t.) to facilitate lentiviral particle migration through the

    surfactant layer and cell membrane and promote efficiency of gene transfer. Results from histological

    studies showed that administration of LPS caused lung inflammation with inflammatory cell infiltration.

    Overexpression of PRMT4 enhanced lung inflammation and knockdown of PRMT4 or application of

    PRMT4 inhibitor attenuated lung inflammation (Fig. 7A, upper panels). Results from TUNEL staining

    showed that LPS caused cell death in lung tissues, in which, overexpression of PRMT4 enhanced cell

    death and knockdown of PRMT4 or application of PRMT4 inhibitor attenuated cell death in the lung (Fig.

    7A, lower panels, Fig. 7B). Immunoblotting results from lung indicated that i.t. administration of LPS or

  • lentiviral particles did modulate PRMT4 protein levels in lung tissue (Fig. 7C). Surprisingly, we observed

    that LPS induced substantial cell death in the spleen as evidenced by TUNEL staining. Splenic cell death

    occurred in the white pulp, a zone that T cells reside (Fig. 7D, E). Further, overexpression of PRMT4

    markedly enhanced LPS-induced lymphocyte death whereas silencing of PRMT4 by shRNA significantly

    diminished cell death. TP064 partially protected splenic lymphocytes from death. Lung infection can

    serve as a reservoir of microbial products that can disseminate systemically. Thus, we speculated that i.t.

    administration of LPS might access the systemic circulation to disseminate to major organs such as the

    spleen. We analyzed splenic cell death with flow cytometry and identified that overexpressed PRMT4

    enhanced cell death in CD4+ T cells (Fig. 7F, G). In addition, results from survival studies indicated that

    PRMT4 overexpressed mice showed a significantly lower survival rate. Depletion of PRMT4 by shRNA or

    application of TP064 remarkably improved mouse survival (Fig. 7H). These data suggest that LPS-

    enhanced PRMT4 protein expression promotes lymphocyte death and targeting on PRMT4 improves

    survival in a LPS mouse lung injury model.

    PRMT4 mediates splenic lymphocyte death in a polymicrobial sepsis model.

    We next tested our hypothesis in a well characterized polymicrobial septic mouse model, Cecal ligation

    and puncture (CLP). Mice were subjected to lenti-PRMT4 overexpression and lenti-shRNA as above, CLP

    procedure were followed to induce sepsis (63) in animals. One group of mice receiving lenti-vector only

    were given TP064 (0.2 g/mouse) intravenously following CLP. Consistent with above observations,

    results from TUNEL staining of the splenic tissues showed that CLP was sufficient to cause splenic T cell

    death (Fig. 8A, B). Flow cytometric data confirmed these observations (Fig. 8C, D). Moreover, PRMT4

    overexpression mediated splenic CD4+ T cell death in this model whereas silencing of PRMT4 by shRNA

    or administration of TP064 attenuated splenic T cell death. Lenti-PRMT4 overexpression during CLP

    increased IL-1ra, IL-6, IL-10, IL-17, CCL1-, CXCL1, CXCL9, and CXCL10 levels in mouse sera when

    compared to the CLP group (p

  • stabilized PRMT4 that mediates lymphocyte apoptosis; and (iii) chemical inhibition or genetic depletion

    of PRMT4 attenuates lymphocyte death and protects mice after endotoxin-induced lung injury and

    polymicrobial sepsis (Fig. 9). Dysregulation of PRMT4 has been reported in many pathophysiological

    settings. PRMT4 is aberrantly expressed in breast, prostate, and colorectal cancers that is associated

    with a poor prognosis by promoting tumor progress and cancer metastasis. Consistent with these

    observations, we identified that PRMT4 expression is increased in sepsis. PRMT4 protein was

    upregulated in cellular and mouse septic models, in human infected lung tissue samples, and in

    peripheral blood leukocytes from septic patients. Increased PRMT4 protein caused lymphocyte

    apoptosis and this finding may be one mechanism underlying the pathogenesis of septic

    immunosuppression, as apoptosis of T lymphocytes is a key feature of sepsis-induced

    immunosuppression (64) and lymphopenia that develops during sepsis predicts early and late mortality


    PRMT4 is crucial in lymphocyte lineage differentiation and maturation (49-51). Knockout of PRMT4 in

    mice results in less CD4+/CD8+ cells and prevents thymocyte development (provide citation here).

    However, these global defects in lymphocyte development prevent assessment of PRMT4 function

    during pathophysiologic states when PRMT4 may achieve a high level beyond a physiologic threshold,

    and where the gene product may exert functions other than uncovered in a knockout mouse model. It is

    not uncommon to observe that some proteins display unexpected functions in the context of aberrant

    expression, or low concentrations, or total cellular depletion. For instance, both knockdown and

    overexpressed acyl-CoA:lysocardiolipin acyltransferase-1 harms mitochondrial function, with distinct

    mechanisms (66). While the significance of the aberrantly expressed PRMT4 in specific disorders has

    not been fully characterized, PRMT4 expression in breast cancer is associated with poor prognosis by

    promoting tumor progression and cancer metastasis (67). Thus, reduced tumor free survival in breast

    cancer may be linked to a similar function posited for the methyltransferase in immunosuppression.

    Our studies uncover a unique role for PRMT4 in cell death linked to sepsis. Increased cell death has long

    been noticed as a key pathway in sepsis-induced immunosuppression but the factors leading to this

    increased cell death has not been fully defined. Immune checkpoint proteins including PD1/PDL1 are

    believed to be one of the major pathways that contribute to septic immunosuppression (68). However,

    efficacy of anti-PD-L1 application is limited to a portion of patients of whom PD1/PD-L1 signaling is

    positive and the efficacy of anti-PDL1 application in septic models remains to be determined. Further,

    PD-L1 antibody administration does not reverse the epigenetic changes of immunosuppression in animal

    models. Our findings here add a novel mechanism of immunosuppression at the epigenetic level: the

    potential for a pathogen-derived product to induce cellular concentrations of chromatin modulator,

    PRMT4, that in turn mediates lymphocyte death via caspase 3 related apoptosis, thus serving as a

    potential modulator in sepsis. Further studies are indicated to elucidate the molecular mechanisms

    whereby PRMT4 regulates apoptosis, epigenetically or via its methylation function driving post-

    translational modifications of key regulatory proteins that dictate cellular lifespan. Recent mass

    spectrometric studies uncovered more than 130 PRMT4 modified protein substrates in breast cancer

    cell lines (69). These targets might be suitable candidates for interrogation of post-translational

    modifications by PRMT4 associated with T-cell immunosuppression.

  • Here we identified a new molecular target of FBXO9 in its control of PRMT4 protein stability that

    regulates immune responses through control of T cell lifespan. Before PRMT4 is targeted for

    ubiquitination and subsequent degradation, PRMT4 is recognized by the E3 ubiquitin ligase SCFFBXO9

    through a phosphodegron. In this motif (132-TdxxxSp), the phosphorylation status of serine and

    threonine residues appear to be differentially modified for optimal FBXO9 binding and subsequent

    ubiquitination. Phosphodegrons have been widely cited in governing the stability of crucial molecules in

    the pathogenesis of diseases. In this regard, we previously identified that oxidative stress reduces

    PRMT4 levels via downregulation of a protein kinase GSK3. GSK3 phosphorylates T132 that is crucial

    in regulating the affinity between the phosphodegron and the E3 ubiquitin ligase (60). Interestingly, in

    the present study, we observed that LPS downregulates the E3 ubiquitin ligase component FBXO9 at the

    protein level to promote PRMT4 protein stability.

    We observed higher plasma PRMT4 levels in septic patients compared to non-septic patients. PRMT4 is

    a protein arginine methyltransferase located in both the cytoplasmic and nuclear compartments (cite

    references here). Our results suggest that PRMT4 is highly expressed in leukocytes isolated from septic

    patients and PRMT4 is detectable in mouse sera and human plasma. Considering the fact that high levels

    of PRMT4 are cytotoxic, we speculate that PRMT4 in plasma of septic patients may originate from dying

    or dead cells. In addition, we identified that plasma PRMT4 protein levels were positively correlated

    with IL-6 (r=0.37, p=0.006) in septic patients (Fig. 8G). This is consistent with our observation in the

    polymicrobial infection mouse model with PRMT4 overexpression, in which IL-6 expression is increased.

    Interestingly, FBXO9 is known to control IL-6 production to regulate innate immunity in a LPS cellular

    model (55). PRMT4-mediated histone arginine methylation is a transcriptional activation epigenetic

    marker (please cite reference). Our data invites the possibility that PRMT4 may enhance IL-6 secretion

    possibly through loss of FBXO9 control during endotoxin-mediated cellular stress. Interestingly,

    inhibition of PRMT4 by shRNA or with the small molecule inhibitor improved mice survival in both the

    LPS lung injury and CLP mouse models, suggesting that lymphocyte death may be a critical factor

    underlying the pathogenesis of endotoxin-mediated injury. Therefore, pharmaceutical targeting of

    PRMT4 may be a potential alternative therapeutic approach in septic patients with significantly low T

    cell counts and immunosuppression.

    Materials and Methods

    Cell lines and reagents. Human lymphoma Jurkat cells (ATCC) and human primary pan-T cells (StemCell)

    were cultured with RPMI1640 (Gibco) containing 10% FBS. Cells were maintained in a 37 °C incubator in

    the presence of 5% CO2. V5 antibody, pcDNA3.1D-His-V5-TOPO cloning kit (Cat#: K490001) and

    Escherichia coli Top10 competent cells (Cat#: C404006) were from Invitrogen (St. Louis, MO). PRMT4

    (Cat#:12495) and Hemagglutinin (HA) tag (Cat#: 3724S, lot: 5) antibody were from Cell Signaling

    (Danvers, MA). Ubiquitin (Cat#: sc-166553, lot: A2710) antibody was from Santa Cruz Biotechnology

    (Santa Cruz, CA). FBXO9 (Cat#: PA5-23474) antibody was from Thermo (Rockford, IL). Alexa Fluor 647 Rat

    Anti-Mouse CD8a and BV421 Rat Anti-Mouse CD45R/B220 were from BD Biosciences (San Jose, CA). The

    PRMT4 shRNA was from Origene (Rockville, MD). Cycloheximide (Cat#: ALX-380-269-G001, lot:

  • 01061518), E64D (Cat#: BML-PI107-0001, lot: 08181537), and Ubiquitin aldehyde (Cat#: BML-UW8450-

    0050, lot: 07021447) were from Enzo Life Sciences (Farmingdale, NY). β-actin (Cat#: A3853) antibody,

    bacterial lipopolysaccharide (LPS) from E. coli O111:B4 (Cat#: L4391, lot: 115M4090V) and L-α-

    Lysophosphatidylcholine (lysoPC, Cat#: L-5254) were from Sigma (Carlsbad, CA). MG132 (Cat#: F1101,

    lot: F11052079) was from UBPBio (Aurora, CO). TP064 (Cat#: 6008) was from Tocris Bioscience (Ellisville,

    MO). QuickChange II XL site-directed mutagenesis kits (Cat#: 200522) were from Agilent Technologies

    (Santa Clara, CA). TnT Quick Coupled Transcription/Translation Systems (Cat#: L1170) were from

    Promega (Madison, WI). Immobilized protein A/G Agarose beads (Cat#: 20421) were from Pierce

    (Rockford, IL). All other reagents were of the highest grade available commercially.

    Cloning and mutagenesis. V5-tagged PRMT4 truncations were cloned into pcDNA3.1D-His-V5-TOPO

    plasmid using PCR-based approaches as previously described (70). Mutagenesis was introduced by using

    a QuickChange II XL site-directed mutagenesis kits according to the manufacturer’s instructions. The

    accuracy of the mutagenesis was confirmed by sequencing. The primers used in the construction of

    PRMT4 truncations and site-directed mutagenesis were listed in Table 3.

    Plasmid transfection. All plasmids were introduced into cells using electroporation executed with a

    nuclear transfection apparatus (Amaxa Biosystems, Gaithersburg, MD) with a preset program (X-001 for

    Jurkat cells), following the manufacturer’s instructions as previously described (66). Briefly, one million

    cells in 100 μL of transfection buffer (20mM Hepes in PBS buffer) were mixed with 3 μg of plasmids

    (including expression and shRNA constructs). After electroporation, the cells were cultured with 2 mL

    conditional medium in 6 well plates for 24 h for further analyses.

    Immunoblotting and co-Immunoprecipitation. Immunoblotting and co-immunoprecipitation were

    conducted as previously described (66). Briefly, for immunoblotting, whole cell extracts (normalized to

    total protein concentration) were resolved by SDS-PAGE and transferred to membranes by

    electroblotting. The membranes were blocked with 5% (w/v) non-fat milk in Tris-buffered saline and

    probed with primary antibodies as indicated. Membranes were developed by an enhanced

    chemiluminescence (ECL) system. For immunoprecipitation, 1 mg of cell lysates (in PBS with 0.5% Tween

    20 plus protease inhibitors) were incubated with specific primary antibodies for 2 h at room

    temperature. The mixture was added with 35 µl of protein A/G-agarose beads for an additional 2 h at

    room temperature. The precipitated complex was washed for three times with 0.5% Tween 20 in PBS

    and analyzed by immunoblotting with ECL system.

    Human study and PRMT4 ELISA assays. Subjects with or without sepsis were selected from a cohort of

    mechanically-ventilated patients at the University of Pittsburgh Medical Center (UPMC). Eligible

    patients were 18 years or older with acute respiratory failure requiring mechanical ventilation via

    endotracheal intubation with sepsis as defined by the presence or suspicion of infection and two or

    more systemic inflammatory response syndrome (SIRS) criteria. Control patients were intubated and

    mechanically ventilated for airway protection without sepsis. Deidentified baseline clinical data

  • (including demographics, comorbidities, physiologic and laboratory variables), severity of illness

    (modified sequential organ failure assessment (SOFA) scores), and clinical outcomes: 30- and 90-day

    mortality, duration of ICU stay, incidence of acute kidney injury (defined as elevation of 0.3 mg/dL or

    more from baseline creatinine) or shock (defined as need for vasopressors) within 7-days from

    intubation (10) were extracted from the registry database (Table 2). Deidentified human infectious lung

    samples and normal controls were as described previously (71).

    Deidentified cytokine data were extracted from the registry database, and deidentified plasma provided

    for assay of PRMT4 expression. PRMT4 levels were determined using PRMT4 ELISA kit (Cat#

    MBS3244080 for human PRMT4, and Cat# MBS9339704 for mouse Prmt4, Mybiosource, San Diego, SC,

    USA) as directed by the manufacturer. Briefly, the plates, reagents and samples were brought to room

    temperature. Plasma samples with a volume of 50 μl and 100 μl HRP-Conjugate Reagent were added to

    each well of the 96-well plate. The plate was incubated at 37°C for 60 min and washed with Wash

    Solution for 4 times. The results were visualized with addition of 50 μl Chromogen Solution A and B and

    incubation of the plate at 37°C for another 15 min. The color reaction was stopped with 50 μl of Stop

    Solution and the optical density (OD) was read at 450 nm within 15 min.

    Real‐Time Polymerase Chain Reaction (RT‐PCR). Total RNA from cells was isolated with RNeasy Mini

    Kit (Qiagen, Valencia, CA, USA), and reverse‐transcribed by using High-Capacity RNA-to-cDNA Kit

    (Applied Biosystems, Foster City, CA, USA) following the manufacturer's manual instructions. Single

    stranded cDNA was then amplified by RT‐PCR with specific primers of PRMT4 and GAPDH. RT‐PCR

    was performed on an ABI Prism 7000 thermocycler (Applied Biosystems, Thermo-Fisher Scientific,

    Waltham, MA, USA) with SYBR Green PCR Master Mix (Roche, Basel, Switzerland). For each experiment,

    samples (n = 3) were run in triplicate. Relative gene expression was calculated using the comparative CT


    in vitro Pull-down assay. We conducted in vitro binding assays to identify the FBXO9 binding domain

    within PRMT4. V5-tagged PRMT4 truncated or site directed mutant proteins were in vitro expressed

    using a TnT coupled reticulocyte system. Endogenous FBXO9 protein was obtained by FBXO9

    immunoprecipitation from Jurkat cell lysate. FBXO9-precipitated protein A/G-agarose beads were

    incubated with a variety of PRMT4 truncations or mutants for 2 h. The beads were washed extensively

    with 0.5% Tween 20 in PBS and analyzed by V5 and FBXO9 immunoblotting.

    Lentivirus production. Lentiviruses were generated by Lenti-X Packaging Single Shots VSV-G (Cat#:

    631276, Clontech, CA, USA) according to the manufacturer’s procedures. Lentivirus-containing

    supernatants were concentrated using Lenti-X Concentrator (Cat#: 631231). Concentrated lentiviruses

    were resuspended in PBS and titrated by Lenti-X GoStix (Cat#: 631280). The samples were aliquoted and

    stored at -80°C.

  • Mouse splenic T cell isolation, flowcytometry, and annexin V apoptosis assay. Mouse spleen were

    disrupted in PBS containing 2% FBS. The aggregates and debris were removed by passing suspension

    through Falcon 70-μm cell strainer (BD, NJ, USA). Mouse splenic T cells were isolated using EasySep

    Mouse T Cell Isolation Kit (Cat#: P19851, Stemcell Technologies, Vancouver, Canada) with EasySep

    Magnets (Cat#: 18000) according to the instructions. Above isolated mouse splenic T cells were also

    stained with anti-CD4, CD8a or CD45R antibodies combined. The cells were incubated for 15 - 30 min at

    room temperature in the dark. After adding 400 μl Annexin V binding buffer, the samples were acquired

    on the LSRII flow cytometers (BD Biosciences, MI, USA). All cells were analyzed with Flowjo software

    (Tree Star, OR, USA).

    FITC Annexin V Apoptosis Detection Kit with Propidium Iodide (PI) (Cat#: 640914, BioLegend, CA, USA)

    was employed to detect apoptotic cells. Jurkat cells were harvest and washed twice with cold BioLend

    Cell Staining Buffer and resuspend in annexin V binding buffer with cell density about 2.5 ~ 10 × 106

    cells/ml. After 100 μl of cells were transferred to a 5ml test tube, 5 μl of FITC annexin V and 10 μl of PI

    were added. The cells were gently vortexed and incubated for 15 min at room temperature in the dark.

    After adding 400 μl Annexin V Binding Buffer, the samples were analyzed through BD Accuri C6 flow

    cytometry (BD Biosciences, MI, USA).

    Cytokine proteome profiler array assay. Cytokine proteome profile of mouse sera were measured using

    Mouse XL Cytokine Array Kit (Cat#: ARY028, R&D system, MN, USA) according to the manufacturer’s

    instructions. Briefly, mouse serum samples were incubated overnight with the membrane. The

    membrane was washed to remove unbound material followed by incubation with a cocktail of

    biotinylated detection antibodies. Streptavidin-HRP and chemiluminescent detection reagents were

    then applied, and a signal is produced at each capture spot corresponding to the amount of protein


    Mouse LPS-induced lung Injury and Cecal ligation and puncture (CLP )procedures. LPS-

    induced lung Injury model was conducted as previously described. Briefly, C57BL/6J mice at the age of

    10 weeks were anesthetized by injecting intraperitoneally a solution of 1:1 ketamine (75mg/kg) and

    xylazine (15mg/kg) throughout the experiment. LPS (7mg/kg) were intratreackally administrated and the

    mice were observed for 48 h. Polymicrobial sepsis was induced in mice by cecal ligation and

    puncture(72). Briefly, mice were anesthetized throughout the experiment. The abdomen was shaved,

    and wiped with 70% alcohol. A 1 to 2 cm midline abdominal incision was performed. The cecum was

    exposed and ligated with a sterile silk suture 1 cm from the tip and double punctured with a 19-gauge

    needle. The cecum was gently squeezed to extrude a small amount of fecal material and was returned

    to the peritoneal cavity. The incision was closed with silk sutures. Mice were resuscitated with i.p.

    injection of 1 ml of pre-warmed 0.9% saline solution. Mice were then monitored every 12 hours for

    survival or euthanized at different time points for analysis of different parameters.

    CRISPR/Cas9 PRMT4 Knock-out cell line. Jurkat cells were co-transfected with PRMT4 CRISPR/Cas9 KO

    Plasmid (Cat#: sc-404087-KO-2) and HDR Plasmid (Cat#: sc-404087-HDR-2) using UltraCruz Transfection

  • Reagent (Cat#: sc-395739). Stable KO cells were selected by puromycin following the instruction from

    the CRSPR/Cas9 manufacturer. PRMT4 knockout was confirmed by immnoblotting.

    Statistics. The data represent the Mean + standard deviation in the graphs depicting the error bars or as

    specifically indicated. Prism 7 (GraphPad software, San Diego, CA) was used to determine statistical

    significance. Comparisons between groups were made using unpaired, two-tailed Student’s t-test (two

    groups) and one-way analysis of variance (ANOVA) with post-hoc Tukey HSD or Bonferroni and Holm

    multiple comparisons. Kaplan Meier estimate was used for survival analysis in mouse septic models.


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  • Figure and legends

    Fig. 1. LPS and bacteria increase PRMT4 protein in human lymphoma Jurkat cells. A. Jurkat cells were

    treated with LPS as indicated, cell lysates were immunoblotted with PRMT4 and β-actin antibodies. B.

    PRMT4 mRNA levels were determined by qRT-PCR in LPS treated lymphocytes, Student T-test were

    conducted. C. Jurkat cells were treated with live E. coli (MOI=10) as indicated, cell lysates were

    immunoblotted with PRMT4 and β-actin antibodies. D, E. Lung tissue lysates from deidentified human

    lung samples (D) and peripheral blood leukocytes from septic patients (E) were analyzed for PRMT4 and

    β-actin by immunoblotting. Experiments n=3. F. C57BL/6J mice were subjected to CLP procedures. At 48

    h, mice sera were collected from untreated control group (n=5) and cecal ligation puncture (CLP) group

    (n=10) for Prmt4 ELISA analysis. G. PRMT4 protein levels (log transformed) were determined by ELISA

    from blood plasma from septic patients (n=53) and non-septic control patients (n=53). Lines indicate the

    median and IQR, Mann-Whitney U test, p=0.0004.

  • Fig. 2. PRMT4 is a labile protein degraded via the SCFFBXO9 E3 ligase machinery in lymphocytes. A. Cells

    were treated with cycloheximide (CHX), leupeptin or MG132 as indicated. Cell lysates were

    immunoblotted with PRMT4 and β-actin antibodies. B. Densitometry results in A were plotted. C.

    Ubiquitin overexpression reduces PRMT4 protein in a concentration dependent manner. D. PRMT4 is

    ubiquitinated as shown by co-immunoprecipitation (Co-IP) of precipitates analyzed with ubiquitin and

    PRMT4 antibodies. E. Screen of F-box family members revealed that overexpression of FBXO9 degrades

    PRMT4. F. FBXO9 degrades PRMT4 in a concentration dependent manner. G. Co-IP studies showing that

    PRMT4 interacts with SCFFBXO9. H. Knockdown of FBXO9 stabilizes PRMT4. Experiments n=3.

  • Fig. 3. SCFFBXO9 ubiquitinates PRMT4 at K228. A. schematic presentation of PRMT4 truncation constructs.

    B. Fragment 150-608 does not accumulate after MG132 treatment. C. K228A point mutant does not

    accumulate after MG132 treatment. D. K228 mutant is stable after CHX treatment. E. K228A mutant is

    less ubiquitinated compared to WT PRMT4. F. K228A is not degraded after FBXO9 overexpression.

    Experiments n=3.

  • Fig. 4. FBXO9 docks on a phosphodegron 132TxxxS within PRMT4. A. Pull-down assays suggest that

    aa100-150 of PRMT4 is important for FBXO9 binding. B, C. Fine mapping the FBXO9 binding sites with

    pull-down assays indicate that a phosphodegron 132TxxxS is critical for FBXO9 binding. D, E. Pull-down

    assays with phosphorylation/ dephosphorylation mimics indicate that T132 dephosphorylation and S136

    phosphorylation promote the degron binding to FBXO9. F. T132 dephosphorylation and S136

    phosphorylation accelerate PRMT4 degradation using cycloheximide (CHX). G. Densitometry results of F

    were plotted. Experiments n=1.

  • Fig. 5. LPS reduces FBXO9 levels leading to PRMT4 accumulation and caspase 3 activation in

    lymphocytes cells. A-C. Jurkat cells, mouse splenic lymphocytes, and human peripheral blood T cells

    were treated with LPS as indicated. Cell lysates were analyzed by PRMT4, cleaved caspase 3, FBXO9, and

    β-actin immunoblotting. D. Over-expression of PRMT4 increases cleaved caspase 3 baseline levels in

    Jurkat cells. E. Knockout of PRMT4 in Jurkat cells with the CRISPR-Cas9 technique. F, G. KO of PRMT4

    represses LPS-induced caspase 3 activation (F) and overexpression of PRMT4 enhances LPS-induced

    caspase 3 activation in Jurkat cells (G). H. Lentiviral expression of PRMT4 enhances LPS-mediated

    caspase 3 activation and depletion of PRMT4 by lenti-shPRMT4 reduces cleaved caspase 3 in mouse

    splenic lymphocytes. I. Depletion of FBXO9 by shRNA increases caspase 3 activation and this activation is

    ablated in PRMT4 KO cells. Experiments n=3.

  • Fig. 6. PRMT4 causes lymphocyte death. A, B. FACS analysis of apoptosis in PRMT4 KO or overexpressed

    Jurkat cells with or without LPS treatment. Data of A were quantitated and analyzed with One-way

    ENOVA in B (n=3). C, Empty vector (Vec), Lenti-PRMT4 (OE), or shRNA (sh) particles were delivered

    intratracheally into the mouse for 14 d. Mouse splenic T cells were isolated and treated with LPS for 18

    h, viable cells were counted and analyzed with One-way ENOVA (n=3). D. Jurkat cells were treated with

    LPS and a range of PRMT4 inhibitors as indicated for 3 h. Cell lysates were analyzed for cleaved caspase

    3. E. Isolated mouse splenic T cells were treated with LPS and TP064, cleaved caspase 3 was

    immunoblotting analyzed. Experiments n=3.

  • Fig. 7. Inhibition of PRMT4 suppresses splenic lymphocyte death in a LPS lung injury model. A-D.

    PRMT4 was knocked down (kd) or overexpressed by i.t. administrated lentiviral constructs for 14 d. Mice

    were given (i.t.) LPS or PRMT4 inhibitor as indicated for 24 h (n=8). Lung tissues were stained with

    Hematoxylin Eosin (H&E) staining (A, upper panels) and TUNEL (A, lower panels). TUNEL positive cells in

    lung tissues were quantitated and analyzed with One-way ENOVA (B) (n=3). C. PRMT4 overexpression

    and knockdown in lung tissues were analyzed by immunoblotting. D. Splenic tissues from above PRMT4

  • knockdown or overexpression experiments (A) were stained with TUNEL. E. TUNEL positive cells in

    splenic tissues were quantitated and analyzed with One-way ENOVA (n=3). F, G. Isolated splenic T cells

    were analyzed with flow cytometry. CD4 was used as a T cell marker. The data from E were plotted in F

    and analyzed with One-way ENOVA (n=3). H. Survival studies were conducted in the LPS lung injury

    model, mice were observed for 48 h (n=10). “*” indicates p

  • observed for 5 days, (n=10). G. The correlation of plasma PRMT4 and IL-6 is analyzed and plotted in

    septic patients with lung injury (n=53). Pearson correlation analysis was conducted with the natural log

    transformation and Partial after adjusting for age. “*” indicates p

  • Table 1 – Patient Characteristics

    Control Sepsis

    N 53 53

    PRMT4, mean (SD, ng/mL) 7.8 (11.0) 18.4 (28.6)


    Age, mean (SD) 55(15.0) 55 (17.5)

    Male, n (%) 31 (58.5) 24 (45.3)

    BMI, mean (SD) 28.8 (9.1) 30.9 (9.4)

    Comorbidities, n (%)

    Diabetes 16 (30.2) 22 (41.5)

    COPD 6 (11.3) 11 (20.7)

    Immunosuppression 9 (17) 9 (17)

    Chronic Cardiac Failure 3 (5.7) 7 (13.2)

    Chronic Kidney Disease 6 (11.3) 5 (9.4)

    Pulmonary Fibrosis 0 (0) 2 (3.8)

    Active Neoplasm 3 (5.7) 3 (5.7)

    Chronic Liver Disease 9 (17) 6 (11.3)

    Alcohol Use 13 (24.5) 8 (15.1)

    Severity of Illness

    SOFA score1, mean (SD) 5.2 (2.4) 7.4 (2.6)

    PaO2:FiO2 ratio, mean (SD) 224 (152) 196 (88)

    Shock, n (%) 10 (18.9) 34 (64.2)

    Acute Kidney Injury, n (%) 22 (41.5) 40 (75.5)

    ICU LOS, days, mean (SD) 8.5 (9.4) 13.4 (9.8)

    30-day mortality, n (%) 6 (11.3) 12 (22.6)

    90-day mortality, n (%) 7 (13.2) 13 (24.5)

    BMI - body mass index, COPD - chronic obstructive lung disease, SOFA - sequential organ failure assessment, PaO2 - arterial partial pressure of oxygen, FiO2 - fraction of inspired oxygen, ICU - intensive care unit, LOS - length of stay 1 modified SOFA excludes neurologic score

  • Table 2. The study of association between PRMT4* and cytokines in septic and non-septic


    Group 1 (Sepsis) Crude Adjusted for


    OR (95%CI)

    30 day mortality 1.27 (0.72-2.24) 1.23 (0.67-


    90 day mortality 1.27 (0.73-2.21) 1.23 (0.69-


    Use of vasopressor 1.70 (0.97-2.99) 1.79 (1.00-


    Hyperinflammatory phenotype 1.43 (0.85-2.39) 1.42 (0.84-


    Correlation (P value)

    Ang2* 0.37 (0.007) 0.37 (0.007)

    IL8* 0.28 (0.048) 0.27 (0.052)

    IL6* 0.37 (0.006) 0.37 (0.007)

    Procalcitonin* 0.12 (0.40) 0.14 (0.34)

    St2* 0.15 (0.28) 0.15 (0.31)

    Fractalkine* 0.05 (0.76) 0.02 (0.92)

    IL10* 0.17 (0.23) 0.18 (0.22)

    Pentraxin3* 0.23 (0.16) 0.22 (0.19)

    Rage* -0.03 (0.85) -0.02 (0.92)

    TNFr1* 0.27 (0.052) 0.27 (0.059)

    * Natural log transformation

    Group 2 (Control) Crude Adjusted for


    OR (95%CI)

    30 day mortality 0.75 (0.37-1.53) 0.62 (0.31-1.24)

    90 day mortality 0.89 (0.46-1.72) 0.72 (0.38-1.37)

    Use of vasopressor 0.95 (0.51-1.77) 1.00 (0.51-1.98)

    Hyperinflammatory phenotype 3.01 (1.29-7.02)1 2.29 (0.95-5.51)

    Correlation (P value)

    Ang2* 0.04 (0.80) -0.03 (0.83)

    IL8* 0.10 (0.49) 0.03 (0.83)

    IL6* 0.25 (0.07) 0.20 (0.16)

    Procalcitonin* 0.24 (0.08) 0.22 (0.12)

    St2* 0.03 (0.82) 0.02 (0.89)

    Fractalkine* 0.31 (0.035) 0.31 (0.037)

    IL10* -0.08 (0.56) -0.12 (0.41)

    Pentraxin3* 0.22 (0.14) 0.18 (0.23)

  • Rage* 0.21 (0.13) 0.17 (0.23)

    TNFr1* 0.12 (0.39) 0.06 (0.67)

    * Natural log transformation 1 P = 0.011

  • Table 3. Primers used in the study


















































    The orientation of the all primers are in 5’ to 3’ direction.