Cell Signaling. Bruno Sopko

Transcription

1 Cell Signaling Bruno Sopko

2 Content Signal Transduction Pathways Organization Signals Receptors Soluble Receptors Transmembrane Receptors Enzyme Coupled Receptors G-Protein Coupled Receptors Ion-Channel Coupled Receptors Second Messengers, Amplifiers, Integrators Response Changes to Signals Inhibitors

3 Signal Transduction Pathways

4 Signal Transduction Pathways

5 Signals

6 Receptors Soluble Receptors Transmembrane Receptors Enzyme Coupled Receptors G-Protein Coupled Receptors Ion-Channel Coupled Receptors

7 Soluble Receptors - The steroid/thyroid Hormone Superfamily of receptors Cortisol (glucocortikoid) Androsteron (steroid) 3,3',5-trijodo-L-thyronine (thyroid) All-trans retinol acid (retinoid) Vitamin D 2

8 Soluble Receptors - The steroid/thyroid Hormone Superfamily of receptors

9 Soluble Receptors - The steroid/thyroid Hormone Superfamily of receptors

10 Transmembrane Receptors - Enzyme Coupled Receptors Tyrosine kinases phosphorylate protein tyrosine residues using ATP. Phospholipase C cleaves PIP 2 into IP 3 and DAG.

11 Tyrosine kinases / RAS MAP kinases

12 Tyrosine kinases / RAS MAP kinases

13 Tyrosine kinases / RAS MAP kinases

14 Tyrosine kinases / RAS MAP kinases

15 Tyrosine kinases / RAS MAP kinases

16 Tyrosine kinases / RAS MAP kinases

17 Tyrosine kinases / RAS MAP kinases

18 Tyrosine kinases / RAS MAP kinases

19 Tyrosine kinases / RAS MAP kinases

20 Tyrosine kinases / Insuline receptor

21 Tyrosine kinases / JAK-STAT receptors JAK Janus Kinase STAT Signal Transducer and Activator of Transcription

22 Tyrosin kinases / Receptors of Serin- Threonin Kinases Cytokins mostly

23 Transmembrane Receptors / G-Protein Coupled Receptors Charakteristic receptor structure Heptahelical receptors (7 transmembrane α- helixes)

24 Transmembrane Receptors / G-Protein Coupled Receptors

25 Transmembrane Receptors / Ion Channel Coupled Receptors

26 Second messengers camp cgmp Phospholipids and Ca 2+ PI 3 kinase/akt and mtor MAP kinase pathway

27 camp

28 camp

29 camp

30 cgmp

31 Phosholipids and Ca 2+

32 Phospholipids and Ca 2+

33 Phospholipase C

34 Phosholipids and Ca2+

35 PI 3 kinase/akt and mtor

36 MAP kinase pathway

37 Signalling molecules vesicle stored and released SNAP-SNARE proteins

38 Signalling molecules directly synthesized (Eicosanoids...) compounds containing a 20-carbon core Members of this group: prostaglandins prostacyclines tromboxanes leukotrienes lipoxins hydroxyeicosatetraenoic acids (HETE) hepoxilins

39 Eicosanoids biosynthesis A path in metabolism of polyunsaturated fatty acids (PUFAs), mainly linoleic and arachidonic acid arachidonic acid is (in humans) synthesized from linoleic acid:!!! it is not possible to synthesise de novo Most animals cannot form double bonds behind position 9 linoleic and linolenic acids are essential: must be taken from food (plant oils, peanuts, soya beans, maize)

40 Eicosanoids biosynthesis - overview

41 Main eicosanoid production sites Endothelial cells Leukocytes Platelets Kidneys Unlike e.g. histamin, eicosanoids are not synthesized in advance and stored in granules In case of an emergent need, these are rapidly produced from a released arachidonate Eicosanoids biosynthesis takes place in every cell type except red blood cells

42 Main steps of eicosanoids production 1) Activation of phospholipase A 2 (PLA2) 2) Release of arachidonate into cytosol from membrane phospholipids by PLA2 3) Eicosanoids synthesis from arachidonate COX or LO pathway + further modifications by synthases/isomerases (PGH 2 conversion to other prostanoids, LTA 4 conversion..) depending on cell type

43 1) Activation of phospholipase A2 Ca 2+ dependent PLA 2 expression / activity stimulate: interleukin-1 angiotensin II bradykinin thrombin epinephrine PLA 2 expression / activity block: dexamethasone (synthetic corticoid) annexin 1 (lipocortin) protein inducible by glucocorticoids caspase-3 dexamethasone

44 2) Arachidonate mobilization for eicosanoid synthesis From membrane phospholipids mostly by the action of phospholipase A 2 : Release of arachidonate from phospholipids is blocked by anti-inflammatory steroids!

45 Eicosanoids biosynthesis 3 pathways: A) cyclooxygenase produces prostaglandins and thromboxanes B) lipoxygenase produces leukotrienes, lipoxins, hepoxilins and 12- and 15-HETE (hydroxyeicosatetraenoic acids) C) cytochrome P450 enzymes (monooxygenases) produces HETE, e.g. 20-HETE; it is a main pathway in kidney proximal tubules

46 Products of COX pathway (prostacyclin) (thromboxane) (thromboxane)

47 Inhibition of COX pathway Aspirin inhibits cyclooxygenase activity of PGHS-1 i PGHS-2 (by acetylation of enzyme serine) Other non-steroidal anti-inflammatory drugs inhibit cyclooxygenase activity (ibuprofen competes with arachidonate) Anti-inflammatory corticosteroids block PGHS-2 transcription Corticosteroids

48 Lipooxygenase pathway 12-lipoxygenase Hepoxilins (HXA 3 ) 5-lipoxygenase 15-lipoxygenase 5-lipoxygenase 3 different lipoxygenases indroduce oxygen to position 5, 12 or 15 in arachidonate; a primary product is hydroperoxyeicosatetraenoic acid (HPETE) Only 15-lipoxygenase 5-lipoxygenase produces leukotrienes; it requires protein FLAP Gly Cys Glu -Glu Leukotriene D 4 Leukotriene E 4 -Gly peptidoleukotrienes

49 Synthesis of eicosanoids by enzymes CYP 450 cytochrome P450 enzymes monooxygenases: RH + O 2 + NADPH + H + ROH + H 2 O + NADP + Two types of compounds are produced: epoxygenases - catalyse production of epoxyeicosatrienoic acids (EETs) which are metabolized by epoxid-hydrolases into almost inactive dihydroxyeicosatrienoic acids (DiHETEs) hydroxylases - catalyse production of HETEs (20-HETE, 13-HETE etc.)

50 Eicosanoids - list CYP450 arachidonic acid cyklooxygenases lipoxygenases EETs (epoxides) DiHETEs 19-, 20-, 8-, 9-, 10-, 11-, 12-, 13-, 15-, 16-, 17-, 18-HETE prostacyklins tromboxanes prostaglandins leukotrienes lipoxins hepoxilins 5-, 8-, 12-, 15-HETE

51 Cytokines Group of proteins and peptides (glycopeptides) Influence cell growth (growth factors) Signal transmission from a cell to another cell Important group - lymphokines (also interleukins), proteins released from activated cells of immune system which coordinate immune response of the organism

52 Cytokine nomenclature Lymphokines - produced by activated T- lymphocytes, they control the response of immune system by signalization between immunocompetent cells Interleukins (IL) - target cells for IL are leukocytes Chemokines - specific class, mediating chemotaxis between cells; stimulate leukocyte movement and regulate their migration from blood into tissues Monokines - produced mainly by mononuclear cells, such as macrophages

53 Main function of cytokines Hematopoiesis (e.g. CSF - colony stimulating factor) Inflammatory reactions (e.g. IL1 - interleukin, TNF - tumor necrosis factor) Chemotaxis (e.g. IL8, MIP1- macrophage inflammatory protein 1, BLC B-lymphocyte chemoatractant) Imunostimulation (e.g. IL12, IFNg - interferon) Imunosupression (e.g. IL10) Angiogenesis (e.g. VEGF- vascular endothelial growth factor) Embryogenesis (e.g. TGF-, LT lymphotoxin)

54 Signal termination The chemical messenger itself (acetylcholine esterase, insulin degradation in liver) The reaction itself (when GTP in G-protein is used, G-protein GDP complex forms the original structure) Degradation of second messenger (phosphodiesterase cleavage of camp) Phosphatases

55 Response Changes to Signals Intracellular Phosphorylation sites Receptor number downregulation Hormone-receptor complex taken into cell by endocytis Degradation and recyclation of receptors Number of available receptors can be altered by other hormones

56 Response Changes to Signals

57 Literature R.K. Murray et al.: Harper's Illustrated Biochemistry, twenty-sixth edition, McGraw-Hill Companies, 2003 Allan D. Marks, MD: Basic Medical Biochemistry a Clinical Approach, Lippincott Williams & Wilkins, 2009 Ernst J. M. Helmreich, The Biochemistry of Cell Signalling, Oxford University Press, USA, 2001 Geoffrey M. Cooper, Robert E. Hausman, The Cell: A Molecular Approach, Fourth Edition, Sinauer Associates, Inc., 2006 Michael J. Berridge, Peter Lipp and Martin D. Bootman, The versatility and universality of calcium signalling, Nature Reviews Molecular Cell Biology (1), 2000