CBNS 101 lecture14

CBNS 101 lecture14 - O v e r v ie w o f s ig n a l tr a n s...

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Overview of signal transduction through cell surface receptors
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β α γ α - subunit: • binds to GDP when inactive, GTP when active • has low GTPase activity (acts as a timer to eventually inactivate itself) • can have binding site for another protein (such as adenylyl cyclase) that is masked when bound with the βγ subunits. βγ subunits: • regulatory subunits, keep the α subunit inactive when complexed together. • can have binding site for another protein - site hidden by α binding. Heterotrimeric G - proteins G-protein-coupled receptors act through heterotrimeric G-protein s.
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Here’s how it works . conformation altered conformation altered, GDP exchanged for GTP activated α , βγ subunits split receptor still active. . signal molecule binds receptor
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How is signaling through G-protein coupled receptors shut down?
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……. .which in turn produce secondary messenger molecules that amplify and distribute the signal. Cyclic AMP ( cAMP ) Inositol Triphosphate / Diacylglycerol Ca 2+ Ions Activated α , βγ subunits remain associated with the plasma membrane and activate a variety of effector enzymes…. .
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Phospholipase C- β is a major target of the activated α subunit
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The two branches of the inositol phospholipid pathway
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Troponin A-actinin Gelsolin Ca ++ ATPase Villin Regulated exocytosis PKC CaM Kinases-many substrates Blood platelets Serotonin release Mast Cells Histamine release Adrenal Medulla Epinephrine secretion Pancreas Insulin secretion Pituitary cells LH and GH secretion Thyroid Calcitonin secretion Testes Testosterone secretion Neurons Dopamine release Smooth muscle Increased contractility Liver Glycogen hydrolysis Adipose tissue Fat synthesis Intracellular Ca ++ targets PKC Controlled Responses
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Synthesized from ATP by adenylyl cyclase Destroyed by cyclic AMP phosphodiesterase ATP cAMP 5’-AMP Adenylyl Cyclase is another major target of the activated α subunit Concentration of cyclic AMP in an unstimulated cells is very low (~ 10 -7 M)
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This note was uploaded on 05/26/2011 for the course CBNS 101 taught by Professor - during the Spring '08 term at UC Riverside.

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CBNS 101 lecture14 - O v e r v ie w o f s ig n a l tr a n s...

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