Intercellular communication

Intracellular signals

Gene regulation

Ligand

Surfacereceptor

Gene

cell

nucleus

Signal transduction: receptor gene

3

21

1- TF activation via signalling cascades2- TF activation at the receptor3- TF activation by membrane soluble ligands

(TF: transcription factor)

Intracellular receptor

Receptor Tyr-Kinases:VEGFRs, Tie-Rs, EphRs (neovascularization)

Receptor Ser/Thr-Kinasen:TGF-betaRs (growth inhibition,

pleiotropic effects)

Rezeptor-Guanylylcyclases:ANP-R (Salt- und water balance, relaxation)

Trimeric Receptors:TNFRs (inflammation, apoptosis)

Receptors with signalling cascades including Proteolytic cleavages:WNT-R (embryonal development, adult stem cells)

Enzym-domäne

Receptors with enzyme function

Rezeptors with enzyme domains

Rezeptor-Tyrosine kinasesRezeptor-Serine/Threonine kinases Rezeptor-Tyrosine phosphatases Rezeptor-Guanylyl cyklases

Receptors associated with enzymes(direct or via adaptors)

Tyrosine kinasesSerine/Threonine kinasesPhosphatases

Cell membrane

Ligands

EnzymEnzyme

Adaptor

Kinases - Phosphorylation

Phosphatasen - Dephosphorylation

Tyrosine-OH Tyr-Kinases

Serine-OH Ser/Thr-KinasesThreonine-OH

„dual specificity“ Kinases

Families of receptor tyrosine kinases

Surface receptors with enzyme domains

Receptor tyrosine kinases:(Receptors for growth, differentiation factors and a peptide hormone)

EGF-R: triggers proliferation of many different cell types (epidermal growth factor receptor)

Insulin-R: triggers carbohydrate metabolism, protein synthesis

IGF-R: triggers growth and survival(insulin-like growth factor receptor)

NGF-R: triggers survival and growth of neurons(nerve growth factor receptor)

PDGF-R: triggers survival, growth, proliferation of different cell types

(platelet-derived growth factor receptor),

M-CSF-R: triggers proliferation and differentiation of monocytes/macrophages (macrophage colony stimulating factor receptor)

FGF-R: triggers proliferation of different cell types, triggering signal in

(fibroblast growth factor receptor) embryonal development

VEGF-R: triggers Angiogenesis Example 1 (vascular endothelial cell growth factor)

Tie-R: function in angiogenesis und vessel formation

Eph-R: triggers angiogenesis, directs cell and axon migration Ephrin receptor

VEGF/VEGFR

Example of growth factor receptor with specific activitz onEndothelial cells (cells of the blood vessel wall)Recptor only (mainly) expressed in endothelial cells

Induces proliferation, filopodia extension, sprouting and aSpecific function of endothelial cells, i.e. tube formation,formation of capillaries

VEGF-R Familievascular endothelial cell growth factor receptor

VEGFs and VEGF-Rs are important for angiogenesis(blood vessel formation by sprouting from existing vessels)and lymphangiogenesis (lymph vessel formation)

Important for wound healing

Tumor angiogenesis: many tumors produce VEGF, leads to high vascularizationand good blood supply for tumordissemination of metastasis via blood and lymph vessels

Blood vessels in the cornea

3 important signalingcascades are induced:

- Ras

- PLC-(Phospholipase C-

- PI3-Kinase(Phosphoinositol 3-Kinase)

Docking of proteins viaSH2 (Src-homology) domainsbind P-Tyr and neighbouring amino acidsInitially described for intracellular tyr-kinase c-Src(Oncogene of Rous Sarcoma Virus)

Grb-2 adaptor: SH2- Domain

SOS is Ras-GEF (guanine nucleotide exchange factor)

Ras: GTP-binding protein (Oncogene detected in rat-sarcoma)

SOS

Ras activates MAP-Kinase pathway:1- MAPKKK2- MAPKK3- MAPK

MAPK: Mitogen-activated Kinase

(there are 3 parallel MAP-Kinase cascades:MEK/ERKP38JNK)

Raf

MEK

ERK

3 important signalingcascades are induced:

- Ras

- PLC-(Phospholipase C-

- PI3-Kinase(Phosphoinositol 3-Kinase)

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PLC- pathway induced by tyrosine kinase receptors

VEGF

PLC- Ca++ gene regulation

PKC

10-7 M

10-3 M

„Second messenger“DAG, IP3 and Ca++

activated PLC-

PKCPhosphorylates many substrates,can activate MAP-kinase pathway,gene regulation

Ca++

Calmodulin/CalcineurinNFAT- transcription factor

PLC- signaling pathway

Ca++

Calmodulin

Calcineurin

NFAT

PI

Ca++ pathway - gene regulation

The phosphatasecalcineurindephosphorylatesNFAT

NFAT translocatesinto the nucleus

NFAT= transcription factor(nuclear factoractivated T cell)

nucleus

P

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gene regulation

proliferationvasculogenesisangiogenesis

Y799

Y820

Y925

Y936

Y951Y994

Y1006

Y1052Y1057

Y1080Y1104

Y1128Y1134

Y1175Y1212Y1221

Y1303Y1307

Y1317

Src (vascular leakage)

TSAd (migration)

PI-3 kinase (survival)

PLC-

VEGFR2

Sakurai et al.PNAS 2005

EC “specific” factors/receptors:

VEGFR1 VEGF-A, PlGF

VEGFR2 VEGF-AVEGFR3 VEGF-C

TIE1TIE2 ANG1,2

VEGF

PIP2

Ca 2+

CAM

IP3- R

End.Ret.

IP3

NFAT

DAG

PKCCa

2+

MEK1/2

ERK1/2

+

CN

VEGF responsive genes

R-TykPLC-

VEGF vs. EGF signaling

Raf

EGR-1P

R-Tyk

EGF

Ras

phosphorylated MAPK ERK is transprted into the nucleus,where it phosphorylates the transcription factor TCF

ERK: extracellular signal regulated kinaseTCF: ternary complex factorSRF: serum response factorSRE: serum response element

(DNA binding sequence for TCF and SRF in promoter of several genes)

genes forcell cycle/proliferation

PKB, PDK:(PDK: PI-dependenmt kinase)

Ser/Thr kinases

PI-3 Kinase Pathway and Survival

Unterlagen:

http://mailbox.univie.ac.at/erhard.hoferStudent point, Vorlesungsunterlagen

erhard.hofer@univie.ac.at