block a: membrane biology & biochemistry lipid signalling ... fileblock a: membrane biology...

Block A: Membrane Biology & Biochemistry

Lipid signalling and sphingolipid function

02.-06.11.2015

Gerhild van Echten-Deckert

Tel. 73 2703E-mail: g.echten.deckert@uni-bonn.de

Programme of the weekMonday Monday - General discussion: cellular signalling- Phosphoinositids as signalling moleculesp g g- Bioactive fatty acid derivatives: eicosanoids (and endocannabinoids)- Sphingolipids: structure and function

T d Tuesday - Sphingosine-1-phosphate and neurodegeneration (Morbus Alzheimer) - Neural-targeted deletion of SPL and its impact on cognitive skillsNeural targeted deletion of SPL and its impact on cognitive skills

Thursday- The amyloid cascade hypothesis: pros and cons

- Sphingolipids: Critical Players in Alzheimer’s Disease

Friday- General discussion: what did you learn?- Take home messages

- QuestionsQuestions

Phosphoinositides as Signal Transducersp g

- Phospholipase C: different isoforms are activated by different signalsthat bind either GPCR or RTK

- PI-3 kinase pathway

Signal transduction from GPCRs to effector proteins

Lodish et al. Molecular Biology of the Cell

Signal transduction from RTKs to effector proteins

Lodish et al. Molecular Biology of the Cell

Intracellular signallingb h h i itidby phosphoinositids

Nature has used several possible variations of theinositol head group to createinositol head group to createhighly specific docking sites for lipid binding proteins

Wymann & Schneiter, Nature, 2008

Modification of a common phospholipid precursor generates several d h i f D G d IPsecond messengers: synthesis of DAG and IP3

Lodish et al. Molecular Biology of the Cell

Phospholipase C Isoforms

Berg, Tymoczko, Stryer: Biochemistry, 2002

PLC-induced release of Ca2+ from the ER is mediated by IP3

Löffler, Petrides, Biochemie und Pathobiochemie

PLC is an effector targeted by GPCRs

Short term effects on cell metabolism and movementLong term effects on gene expression

PLC1 is an effector targeted by RTKs1  g y

The activated EGF receptor recruits the cytosolic phospholipase C The activated EGF-receptor recruits the cytosolic phospholipase C-1(substrate PIP2) via its SH2-domain and activates the enzyme by phosphorylation.

Phosphatases terminate this process.

Proteinkinase C

Berg, Tymoczko, Stryer: Biochemistry,

PI 3-phosphates recruit and activate protein kinase B (PKB)

PH: pleckstrin homologyPDK: PI‐dependent kinase

PI-3 kinase generates phosphatidylinositol 3-p p yphosphates, which arebinding sites for varioussignal-transduction proteins,usually triggering survival.

PTEN: the first tumour suppressor with phosphatase activity

PTEN phosphatase has ab d f b broad specificity but its major function in cells isto reverse the PI-3 kinase

t l d ti catalyzed reaction.

PTEN is deleted or mutatedin multiple types of humanin multiple types of humancancer (glioblastoma, prostate cancer, endometrial tumour)endometrial tumour).

Overexpression of PTENpromotes apoptosis in promotes apoptosis in cultured mammalian cells.

www.ncbi.nlm.nih.gov/bookshelf/picrender.fcgi...

Wymann & Schneiter, Nature, 2008

Arachidonic acid

Prostaglandines:derivatives of the hypothetic ypprostanoic acid

Ulf von Euler 1930Ulf von Euler, 1930(in human seminal fluid)

Regulate physiological processes:Regulate physiological processes:‐ platelet aggregation‐ uterine contractions

i i (f )‐ pain, pyrexia (fever)‐ inflammation‐ secretion of mucins that protect thegastric mucosa from acid and proteasesin the stomach 

Voet, Voet: Biochemistry

Metabolism of arachidonic acid

Berg, Tymoczko, Stryer: Biochemistry

The cyclic fate of arachidonic acid

Voet, Voet: Biochemistry

Benjamin Wäschle - comment 2012

The effects of cyclic endoperoxidases (facilitated by COX1 and COX2)

COX1 Stomach (PGE1) Mucous membrane production Acid productionKidney (PGE2) Perfusion Water excretiony ( 2)Thrombocytes (TxA2) Aggregation Vasoconstriction

COX2 Uterus Tone (labor pains, period pain)V l (PGI ) V dil i P biliVessels (PGI2) Vasodilation PermeabilityThrombocytes (PGI2) AggregationNociceptors SensitivityNociceptors SensitivityFever (PGE2) Thermoregulation hypothalamus

Benjamin Wäschle - comment 2012

What is the problem of selective COX2 inhibitors? ...

Benjamin Wäschle - comment 2012

Inhibition of COX2 facilitated prostacyclin biosynthesis and no interference with thromboxan A2 biosynthesis leads to:‐ Higher thrombocyte aggregation  thrombosis

myocardial infarction

... They kill you. And make cute girls cry.

X-ray structure of PGH synthase (PGHS) from sheep seminal vesicles in complex with flurbiprofen which

Diagram of the left PGHS subunit (green).van der Waals surface of active site channel

seminal vesicles in complex with flurbiprofen which forms an ion pair with Arg120

HemeHeme

TTyr

Ser 530

Tyr385

Arg 120

Page

964

Arg

g

P

Voet, Voet: Biochemistry (4.ed)

PGH2-Synthase has 2 catalytic activities:2 catalytic activities:

Cyclooxygenase (COX)

The various effects of Aspirin are based on the inhibition of COX activity

Peroxidase

Voet, Voet: Biochemistry

Some nonsteroidal anti-inflammatory drugs (NSAIDs).( id ff d i hibi i f b h i f COX)(side effects due to inhibition of both isoenzymes of COX)

Page

965

P

Voet, Voet: Biochemistry (4.ed)

Selective COX-2 inhibitors (coxibs).

Withd f h ti l k tWithdrawn from pharmaceutical marketdue to unanticipated cardiac side effectsarising from attenuation of PGI2 formation!

Page

966

P

(to large to enter COX-1 active site channel, th t i 20 % ll i l th th t f COX 2)

Voet, Voet: Biochemistry (4.ed)

that is 20 % smaller in volume than that of COX-2)

Metabolism of the endocannabinoid anandamide

Kendall & Nicolaou, Prog Lipid Res, 2013

Metabolism of the endocannabinoid arachidonoyl glycerol

Kendall & Nicolaou, Prog Lipid Res, 2013

Mode of action of the nuclear receptor superfamily PPAR

L: fatty acids and d i ti derivatives

PPAR: peroxisomeproliferator-

PPAR, liver & adipose tissue, turns on genes proliferator

activated receptor

RXR: retinoid X receptor

for lipid synthesis, differentiation of fibroblasts into adipocytes

PPAR, hepatocytes,turns on genes for FA - PPAR, liver & muscle

i

adipocytes.

turns on genes for F oxidation and ketone body formation duringfasting.

tissue, turns on genes for -oxidation and for energy dissipation through uncoupling of

.through uncoupling ofmitochondria (prevents obesity).

Diet regulates the expression of genes central to maintaining body mass

Metabolic integration by PPAR isoforms

General mechanism by which lipophilic compounds regulate gene expression

Lipophilic ligands:steroid hormones thyroid hormones,retinoids (vit. A) vitamin D

Nelson, Cox: Lehninger Biochemistry,