30 - Desensitization Epinephrine receptorcontinuous...

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30.1 Signal Transduction Purpose—regulate cellular responses to extracellular signals Single cell organisms respond to food mostly Glucose Starvation Chemotaxis Multicellular organisms: cells must communicate with each other
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30.2 Cells communicate in different ways Receptor types: Steroid hormone receptors Heterotrimeric G-protein coupled receptors Tyrosine kinase receptors
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30.3
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Heterotrimeric G protein coupled receptors Include receptors for epinephrine, prostaglandins ~1000 different receptors in this family in humans In the absence of hormone, heterotrimeric G protein binds GDP (inactive) Hormone receptor complex stimulates exchange for GTP Activates target (adenylate cyclase here) (signal amplification) GTP slowly hydrolyzed to GDP (molecular clock) limits response Inhibitory G proteins too that work with different receptors (integration of response to multiple hormones) 30.4 Receptor (serpentine receptor) 7 transmembrane helices
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Unformatted text preview: Desensitization Epinephrine receptorcontinuous exposure leads to phosphorylation at a set residuedecreases the influence of hormone on heterotrimeric G protein. Phosphorylated receptors can be endocytotically sequestered Receptor Tyrosine Kinases (RTK) Phosphorylate specific tyrosine residues in target proteins Hormone binds to extracellular domain Many RTKs are activated by dimerization when bind cognate hormone Tyrosine kinase domains cross phosphorylate opposing receptor Activated receptor can bind cellular proteins that are part of signaling cascade SH2 domain Can also phosphorylate tyrosines on other target proteins 30.5 30.6 Insulin RTJ Oncogenic mutants of Ras are Gap insensitive 30.7 Ca ++ , Inositol trisphosphate and Diacylglycerol can serve as second messengers...
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This note was uploaded on 02/23/2011 for the course CHEM 4731 taught by Professor Mchenry during the Spring '08 term at Colorado.

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30 - Desensitization Epinephrine receptorcontinuous...

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