Signal Transduction Pathways

1. Signal Transduction Pathways • An introduction to Information metabolism • Chapter 15 Stryer Biochemistry

6. Signal Transduction • 1) Membrane receptors transfer information • 2) Second messengers relay information from the receptor ligand complex. • 3) Protein phosphorylation is a common means of information transfer

7. Protein Phosphorylation

8. 7TM helix receptors • The 7TM helix receptors change conformation upon binding of ligand and activate a G-Protein • Rhodopsin • Β-adrenergenic receptor

20. Activated G-Protein transmits signal by binding to other proteins G-Protein binding to adenylate cyclase increases the catalytic efficiency of the adenylate cyclase and increases the synthesis of cAMP inside the cell

22. G-Proteins spontaneously reset themselves Resetting the G-Protein

23. Receptor resetting

24. cAMP stimulates the phosphorylation of many target proteins by activating PKA • 1) Glycogen metabolism • 2) Expression of specific genes (CREB) • 3) Synaptic transmission • Serotonin binds to a 7TM helix receptor • cAMP activates PKA • PKA facilitates the closing of K channels by phosphorylation

25. Hydrolysis of Phosphatidyl inositol Bisphosphate

29. What are the biochemical effects of IP3? • IP3 causes the rapid release of Ca from intracellular stores (ER, SR) • Causes smooth muscle contration • Glycogen breakdown • Vesicle release

31. Diacylglycerol activates PKC

35. Ca2+ Ion is a ubiquitous cytosolic messenger

41. Ca activates the regulatory protein Calmodulin

43. Regulation of Calmodulin of Calmodulin kinase

47. Receptor dimerisation