Cell Signaling, Wound Repair, and ATP Receptors

1. Cell Signaling, Wound Repair, and ATP Receptors Kevin Quirke and Alex Knobloch

2. Cell Signaling Overview • typical cell exposed to numbers of different signal molecules • selective response according to cell function • cellular response dictated by: • unique sets of cell surface receptors • cell-specific intracellular targets

3. Cell Signaling Overview altered metabolism altered gene expression altered cell shape or movement expression Essential Cell Biology, 2nd Edition (Alberts et al., 2004)

4. Examples of Cell Signals • growth/mitotic signaling: epidermal growth factor (EFG) EFG-receptor (EGFR) EFG-receptor (EGFR) Essential Cell Biology, 2nd Edition (Alberts et al., 2004)

5. Examples of Cell Signals • growth/mitotic signaling: EFG activated EFG-receptor (EGFR) Essential Cell Biology, 2nd Edition (Alberts et al., 2004)

6. Examples of Cell Signals • growth/mitotic signaling: active Ras protein phosphorylation cascade activation of transcription factors for pro-mitotic genes Essential Cell Biology, 2nd Edition (Alberts et al., 2004)

7. Process Where Cell Signaling is Important=Wound Repair

8. Wound Repair Inflammatory Proliferative Remodeling • Tissue repair following injury • Three phases6:

9. Examples of Signals in Inflammatory Phase • PAMPs • DAMPs

10. PAMPs Pathogen-associated molecular patterns (PAMPs) Microbial molecules targeted by macrophages Bacterial Cell Teichoic acid

11. Innate Immune Response to PAMPs PAMP bacterium Receptor Inflammation cytokines macrophage

12. DAMPs Damage-associated molecular-patterns (DAMPs) Intracellular molecules Released by cells undergoing stress or death Initiate immune response

13. Extracellular DNA as a DAMP Extracellular Space

14. Extracellular DNA as a DAMP Receptor Inflammation cytokines Extracellular Space macrophage

15. Key Recipient and Producer of Inflammatory Phase Signals = Monocytes

16. Monocyte White blood cell Produced in boned marrow Differentiates in tissues Participate in wound repair University of New England Phagocytes Bone Marrow Stem Cell Blood Monocyte Tissue Macrophage Abbas et al., 2009

17. Monocyte’s Role in Wound Repair • Three phases: • Inflammatory • Proliferative • Remodeling

18. Monocyte’s Role in Wound Repair Pro-angiogenic factors cytokines monocyte monocyte monocyte • Produce inflammatory mediators • Produce pro-angiogenic factors • Phagocytose cellular debris

19. VEGF Vascular endothelial growth factor (VEGF) Chemical signal Pro-angiogenic factor Promotes wound repair

20. VEGF’s Role in Wound Repair • Three phases: • Inflammatory • Proliferative • Remodeling

21. VEGF’s Role in Wound Repair • Promotes: Endothelial cell • New blood vessel formation (angiogenesis) • Endothelial cell proliferation • Oxygen supply to tissues www.evgn.org

22. VEGF Triggers of VEGF production: • Hypoxia • Oncogenes • Other growth factors and cytokines • Cellular receptors

23. VEGF Cell signal monocyte • Trigger: Cellular receptor • Target: Endothelial cellVEGF Receptor VEGF VEGF receptor Blood Vessel

24. ATP = one signal molecule to which monocytes respond

25. ATP as an Extracellular Signal • roles as signal molecule: • DAMP • inflammatory response1, pain sensation2 • synaptic signaling (neurotransmitter)2,3 • neuron-glia signaling4 • muscle contraction5 adenosine-5'-triphosphate (ATP)

26. P2 Nucleotide Receptors • family of nucleotide cell surface receptors • two major subfamilies P2Y Receptors - G-protein coupled1 - bind ATP, ADP, UTP, and UDP1 Essential Cell Biology, 2nd Edition (Alberts et al., 2004)

27. P2 Nucleotide Receptors • family of nucleotide cell surface receptors • two major subfamilies P2Y Receptors - G-protein coupled1 - bind ATP, ADP, UTP, and UDP1 P2X Receptors - ionotrophic (ligand-gated)1 - bind ATP1 wikipedia.org

28. P2X Subfamily • ligand-gated ion channels • cation selective2 • equal permeability to K+ and Na+ • significant permeability to Ca2+ • seven members (P2X1-7)

29. P2X7 • aka P2RX7

30. P2X7 • aka P2RX7 Zebrafish P2X4 (Kawate et al., 2009)

31. P2X7 • aka P2RX7 wikipedia.org

32. P2X7 • ligand-gated ion channel ATP Essential Cell Biology, 2nd Edition (Alberts et al., 2004)

33. P2X7 • requires high concentrations (mM) of ATP for activation1 • sensitive to synthetic ATP analog BzATP1 3′-0-(4-benzoyl) benzoyl ATP (BzATP) adenosine-5'-triphosphate (ATP)

34. P2X7 • requires high concentrations (mM) of ATP for activation1 • sensitive to synthetic ATP analog BzATP1 3′-0-(4-benzoyl) benzoyl ATP (BzATP) adenosine-5'-triphosphate (ATP)

35. P2X7 • major immune modulator • activation in monocytes production of pro-inflammatory molecules nitric oxide synthase ROS IL-1β (Lenertz et al., 2009)

36. The Hill et al. paper suggests a role for ATP and P2X7 in the proliferative phase of wound repair • Counterintuitive considering its role in the inflammatory phase…

37. P2RX7 monocyte ATP Cell Angiogenesis VEGF

38. References 1. Lenertz, L.Y., M.L. Gavala, L.M. Hill, and P.J. Bertics. 2009. Cell signaling via the P2X7 nucleotide receptor: linkage to ROS production, gene transcription, and receptor trafficking. Purinergic Signal 5: 175-187. 2. Khakh, B.S. 2001. Molecular physiology of P2X receptors and ATP signalling at synapses. Nat. Rev. Neurosci. 2: 165-174. 3. Khakh, B.S., and R.A North. 2006. P2X receptors as cell-surface ATP sensors in health and disease. Nature 442: 527-532. 4. Fields, R.D., and G. Burnstock. 2006. Purinergic signalling in neuron-glia interactions. Nat. Rev. Neurosci. 7: 423-436. 5. Vassort, G. 2001. Adenosine 5′-triphosphate: a P2-purinergic agonist in the myocardium. Physiol. Rev. 81: 767-806. 6. Kirsner, R.S., and W.H. Eaglstein. 1993. The wound healing process. Dermatol. Clin. 11: 629-640. 7. Abbas, A.K., and A.H. Lichtman. 2009. Basic immunology: functions and disorders of the immune system. Saunders: Philadelphia, pp. 24-29.