Molecular Biology of THE CELL 4 th edition Chapter 15 Cell Communication

1. Molecular Biology of THE CELL 4th edition Chapter 15 Cell Communication

2. Cell Communication Single cell Multicellular organism

3. GENERAL PRINCIPLES OF CELL COMMUNICATION Extracellular signal molecules bind to specific receptors

4. Extracellular signal molecules can act over either short or long distance

5. Autocrine signaling can coordinate decision by groups of identical cells “Community effect” in early development In tumor biology---cancer cells stimulate their own proliferation

6. Gap junctions allow signaling information to be shared by neighboring cells Ca2+, cAMP etc. but not for proteins or nucleic acids Intracellular electrodes, small water-soluble dyes Connexin 43 deficiency --- abnormal heart development

7. Each cell is programmed to respond to specific combinations of extracellular signal molecules

8. Different cells can respond differently to the same extracellular signal molecules

9. The concentration of a molecule can be adjusted quickly only if the lifetime of the molecule is short

10. Nitric oxide gas signals by binding directly to an enzyme inside the target cell Nitroglycerine --- angina Viagra --- PDE inhibitor CO

11. Nuclear receptors are ligand-activated gene regulatory proteins

12. Ligand-binding domain

14. The three largest classes of cell-surface receptor proteins are ion-channel-linked, G-proteins-linked, and enzyme-linked receptors

15. Most activated cell-surface receptors relay signals via small molecules and a network of intracellular signaling proteins SCIENCE 281, 1671-1674 (1998) A Mammalian Scaffold Complex That Selectively Mediates MAP Kinase Activation (JNK interacting protein-1. JIP-1) Alan J. Whitmarsh, Julie Cavanagh, Cathy Tournier, Jun Yasuda, Roger J. Davis*

16. Some intracellular signaling proteins act as molecular switches Monomeric GTPase Trimeric GTPase ~2% of human genes (576 kinases in human genome)

17. Signal integration by protein phosphorylation

18. Intracellular signaling complexes enhance the speed, efficiency, and specificity of the response

19. Complex forms transiently

20. Interactions between intracellular signaling proteins are mediated by modular binding domains

21. SCIENCE 278, 2075-2080 (1997) Signaling Through Scaffold, Anchoring, and Adaptor Proteins Tony Pawson and John D. Scott

22. www.cellsignal.com PDZ Domain Domain binding and function:PDZ domains bind to the C-terminal 4–5 residues of their target proteins, frequently transmembrane receptors or ion channels. These interactions can be of high affinity (nM Kd). The consensus binding sequence contains a hydrophobic residue, commonly Val or Ile, at the very C-terminus. Residues at the –2 and –3 positions are important in determining specificity. PDZ domains can also heterodimerize with PDZ domains of different proteins, potentially regulating intracellular signaling. In addition to engaging in protein-protein interactions, several PDZ domains including those of syntenin, CASK, Tiam1 and FAP are capable of binding to the phosphoinositide PIP2. PIP2-PDZ domain binding is thought to control the association of PDZ domain-containing proteins with the plasma membrane. Structure Reference: Doyle, D.A. et al. (1996) Cell 85(7), 1067–1076. The third PDZ domain from PSD-95.

23. Cells can respond abruptly to a gradually increasing concentration of an extracellular signal effector/target : 1~16 Chicken oviduct cells Stimulated by estradiol maximal activation

24. One type of signaling mechanism expected to show a steep threshold-like response

25. A cell can remember the effect of some signals Signals trigger muscle cell determination

26. Cells can adjust their sensitivity to a signal

27. SIGNALING THROUGH G-PROTEIN-LINKED CELL-SURFACE RECEPTORS 1. The largest family of cell-surface receptors 2. 5% of the C. elegans genes 3. Signal molecules: hormones, neurotransmitters and local medicators 4. Rhodopsin-light receptor 5. Genome sequencing --- vast numbers of new family members 6. Major targets for drug discovery

28. Trimeric G proteins disassemble to relay signals from G-protein-linked receptors Transducin-G protein in visual transduction

29. The disassembly of a activated G-protein into two signaling components

30. The switching off of the G-protein a subunit by the hydrolysis of its bound GTP RGS proteins --- regulators of G protein signaling, act as a subunit-specific GTPase activating proteins (GAPs) ~25 RGS proteins in the human genome

31. Some G-proteins signal by regulating the production of cyclic AMP ~5 X 10-8 M >10-6 M Nerve cell culture, preloaded with a fluorescent protein that changes its fluorescence when it binds to cAMP. (Science 260:222-226, 1993)

32. cAMP-dependent protein kinase (PKA) mediate most of the effects of cyclic AMP Role of cAMP, PKA in glycogen metabolism

33. How gene transcription is activated by a rise in cAMP concentration (CRE, cAMP response element) Role of protein phosphatases?

34. Some G-proteins activate the inositol phospholipid signaling pathway by activating phospholipase C-b (<1% of total phospholipids)

36. The two branches of the inositol phospholipid pathway

37. Ca2+ functions as a ubiquitous intracellular messenger Ca2+ signaling in fertilization of starfish, detected by Ca2+-sensitive fluorescence dye

38. The main ways eucaryotic cells maintain a very low concentration of free Ca2+ in their cytosol

39. The frequency of Ca2+ oscillations influences a cell’s response In a liver cell

40. Ca2+/calmodulin-dependent protein kinases (CaM-kinases) mediate many of the actions of Ca2+ in animal cells A peptide derived from CaM-Kinase II The structure of Ca2+/calmodulin

41. The activation of CaM-kinases II ~2% of total mass in some brain regions, especially in synapses • It can function as a molecular memory device --- • Learning defect (where things are in space) in mutant mice that • lack the brain-specific subunit of CaM-kinase II • (2) Same defect also observed in mutant mice that • have their CaM-kinase II mutated at the autophosphorylation site

42. CaM-kinase II is immobilized on a solid surface +a brain protein phosphatase +repetitive pulse of Ca2+/calmodulin at different frequency Kinase activity assay CaM-kinases II as a frequency decoder of Ca2+ oscillations [Science. 1998 Jan 9;279(5348):227-30.]

43. Smell and vision depend on G-protein-linked receptors that regulate cyclic-nucleotide-gated ion channels

44. Cyclic GMP A rod photoreceptor cell

45. The response of a rod photoreceptor cell to light

46. Extracellular signals are greatly amplified by the use of small intracellular mediators and enzymatic cascades Amplification in the light-induced catalytic cascade in vertebrate rods

47. G-protein-linked receptors desensitization depends on receptor phosphorylation

48. SIGNALING THROUGH ENZYME-LINKED CELL-SURFACE RECEPTORS Six classes: 1. Receptor tyrosine kinases 2. Tyrosine kinase-associated receptors 3. Receptorlike tyrosine phosphatases 4. Receptor serine/threonine kinases 5. Receptor guanylyl cyclases 6. Histidine-kinase-associated receptors

49. Activated tyrosine kinases phosphorylate themselves angiogenesis cell/axon migration

50. Three ways in which signaling proteins can cross-link receptor chains Monomeric vs. dimeric ligand