Signal Transduction, Second Messenger Systems Dr Miklós Geiszt 10.092009 Pathways of signal transmission between cells Pathways of signal transmission between molecules Complexity of signaling pathways (illustration) Principles of receptor function I. Principles of receptor function II. Structure of G-protein coupled receptors Activation of trimeric G proteins Production of cAMP Effect of cAMP on gene transcription Structure of Phosphatidylinositol (PI)action of PI-kinases Phospholipases Phospholipase C mediated hydrolysis of PIP2