1. A role for cAMP

2. Desensitization from persistent signal

3. Other second messengers Phospholipase C cleaves membrane lipid phosphatidylinositol 4,5 bisphospate into two messengers diacylgllycerol and inositol 1,4,5 trisphosphate (IP3) IP3 in turn activates release of calcium ions that act as a messenger and activate protein kinase C (numerous isozymes with tissue specific roles, for instance in cell division)

4. PLC mediated signal transduction

5. Regulation of cell cycle by protein kinases

6. Cyclin-dependent protein kinases control cell cycle By phosphorylating specific proteins at precise time intervals these kinases orchestrate the metabolic activities of the cell for cell division Heterodimers – one regulatory subunit (cyclin) and one catalytic subunit (cyclin- dependent protein kinase [CDK])_

7. Post-translational regulation through phosphorylation and proteolysis

8. Four mechanisms to control CDK activity Phosphorylation –Phosphorylate tyrosine prevents ATP binding –Removal of phosphate from tyrosine and phosphorylation of threonine allows substrate binding Controlled degradation –Feedback loop involving DBRP Regulated synthesis of CDKs and cyclins –MAPK mediated activation of Jun and Fos Inhibition of CDK –Specific proteins such as p21 bind and inactivate CDK

9. Observe variations in the activities of specific CDKs during cell cycle

10. Whither MAPK?

11. Regulation of passage from G1 to S

12. Neuron function and signal transduction Voltage- and ligand-gated ion channels

13. Allosteric effectors of protein structure/function

14. Glutamate receptor http://www.ibcp.fr/GGMM/Nimes/O11.html

15. Forming memories http://users.rcn.com/jkimball.ma.ultranet/Bi ologyPages/L/LTP.htmlhttp://users.rcn.com/jkimball.ma.ultranet/Bi ologyPages/L/LTP.html Mini-review handout http://www.ncbi.nlm.nih.gov/entrez/query.f cgi?cmd=Retrieve&db=PubMed&list_uids= 11807168&dopt=Abstracthttp://www.ncbi.nlm.nih.gov/entrez/query.f cgi?cmd=Retrieve&db=PubMed&list_uids= 11807168&dopt=Abstract

16. Integrating circuits Circuits exhibit synergy within a cellular context Bhalla and Iyengar modeling signal transduction in the brain and long-term potentiation (LTP) (Fig 8.15) http://doqcs.ncbs.res.in/~bhalla/doqcs/template.ph p?x=home&y=indexhttp://doqcs.ncbs.res.in/~bhalla/doqcs/template.ph p?x=home&y=index PKC activates MAPK, while MAPK helps activate PKC (Figure 8.16)

17. Why does it take 100 minutes of 5 nM EGF to reach LTP? 10 min at 5 nM or 100 min at 2 nM EGF is insufficient for LTP (Fig 8.18) Fig 8.19 result of determining concentration dependence of MAPK activation of PKC and the converse Three intersection points – MM 8.2 “Cobweb” –A indicates high activity for both enzymes –B indicates low activity for both –T is threshold stimulation, if EGF is sufficient to activate either PKC or MAPK above T – both will reach A (T serves as a switch between A and B)

18. Turning off LTP Use a phosphatase to knock MAPK below threshold AA (arachidonic acid) generated by PLA2 persists, which makes it hard to turn off Takes awhile to de-phosphatase

19. Integrating more circuits Start with MAPK circuit Add calcium activation, etc. Result in Figure 8.23 –PKC –MAPK –cAMP –Calcium

20. Discovery questions Chapter 8 31-35