Signal Transduction II

1. Signal Transduction II Transduction Proteins & Second Messengers

2. Major Signaling Highways • Growth Factor/Cytokine/Adhesion • RTK • RS/TK • JAK • FAKs • Steroid Hormone • Intracellular DNA binding proteins • Virtually everything else • 7-pass TM receptors

3. Typical Iconic Domain Representations and Family Groupings Non-Receptor Receptor Non-Receptor Receptor

4. It's All About Phosphorylation • RTKs and RS/TK directly phosphorylate each other and substrates upon ligand binding • Ligand activates linked TKs indirectly • 7TM receptors activate non-receptor S/T kinases

5. What goes on must come off • Phosphatase Families

6. Signal Transduction Downstream of Receptor Kinases & Receptor-Linked Kinases Adaptors, Small GTPases, MAPKs

7. RTK Signal Transduction Components • The Receptor • Adaptors, GAPs, GEFs, • All contain SH2 (and usually SH3) domains (bind P-Y) • Adaptors • Shc, Grb2, Nck, Crk • GAPs • Ras-GAP, p120GAP • GEFs • Vav, SOS • Recruit/activate p21 GTPase family members – (Ras family) • Ras, Rho, Cdc42, Rac • PI3K, PLC, • Generate 2nd messengers • PI3K – phosphoinositols (PIP2, PIP3) • PLC - diacylglycerol (DAG)+ inositol phosphate (IP2, IP3)

8. Signal Transduction Paths Downstream of Tyrosine Kinases

9. GEF GAP Grb2,Shc GEF like Sos RTK- Ras - MAPK Pathway

10. Generalized Transcriptional Activation by RTK Signaling Fig 29-6

11. Insulin Triggers Uptake of Glucose – How? Fig 29-7

12. Src – The Prototypical Non-Receptor Tyrosine Kinase • SH1 – tyrosine kinase domain • SH2 – phosphotyrosine binding domain • SH3 – polyproline binding domain • SH2 and 3 domains have been found in many other signal transduction proteins and all have a conserved structure and functionality • SH1 domain found in all tyrosine kinases Fig27-3E

13. polyproline binding domains phosphotyrosine binding domains Adaptors: Masters of their Domains Fig 27-12 Fig 27-11

14. Fig 27-11

15. Small Monomeric GTPases • Dramatically different conformations of proteins depending on ligand • GTP vs GDP • All have MW ~21KDa • p21 • Ras Family • Ras, Rho, Cdc42 • Rab family • Rab, Arf, Sar • See Table 27-3 for others Fig 27-7

16. Activation Cycle of GTPase Fig27-8

17. GAPs & GEFs • Have adaptor domains (SH2, SH3, PH, PTB) • GEF – stimulate release of GDP from GTPase • GAP – stimulate hydrolysis of GTP by GTPase Fig 27-12

18. Activated Ras Triggers MAP Kinase Cascade • MAPK = Mitogen Activated Protein Kinases • ERK1, ERK2, etc = Extracellular signal Regulated Kinase • MAPK is activated by a kinase called variably MAPK Kinase (MAPKK) or MEK (MAPK/ERK Kinase) • MEK is activated by a kinase called Raf (Ras activated factor) (or MAPK Kinase Kinase) • Raf is activated by Ras – not clear how yet

19. MAP Kinase Cascades Lead to Changes in Gene Expression Fig 29-5

20. TK-Linked Signal Transduction Components • Receptor • Non-receptor tyrosine kinases • JAKs • Activate STATs (signal transducers and activators of transcription) • Src family members • Src, Yes, Fyn, Lck • Activated by T-cell receptors, focal adhesion kinases, and RTKs

21. T-cell-Receptor-Mediated Lymphocyte Activation Fig29-8

22. Cytokines Activate JAK-STAT Pathway Fig 29-9

23. RS/TK Signal Transduction Components • Receptors • RII receptor binds ligand 1st & phosphorylates RI upon heterodimerization • RI in turn phosphorylates smads • Regulatory smads • Require phosphorylation by RI receptor • Interact with co-smad & translocate to nucleus • Inhibitory smads • Bind to regulatory smads and block heterodimerization with co-smads • Co-smads • Do not require phosphorylation

24. Ligands of TGF- Superfamily Activate Smad Pathway Fig 29-10