Neurochemistry – Intracellular Signalling

question

Where do cells receive signals?
answer

Environment beyond the membrane
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Name the types of receptors
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1. GCPR: epnephrin receptor 2. Enzyme-linked receptors: insulin 3. Ligan-gated ion channels: nicotinic ACh receptor 4. nuclear receptors: steroids 5. other: integrin receptors
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what are typical ligands?
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– small ions: ferric ions – organic molecules: adrenalin – polysaccharides – peptides: insulin – proteins: VEGF receptor
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What is Kd?
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similar to the Km value
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name a hormone that has a nuclear receptor
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steroids: estrogen
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How many helical segments does a GPCR have?
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7-transmembrane helical segments
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How many types of G proteins exist?
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2: heterotrimeric and small g protein `
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Heterotrimeric proteins
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involved in trans-membrane signalling system (GPCR) – 3 distinct subunits: alpha, beta, and gamma
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small g proteins
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large superfamily proteins, bind GTP and GDP, possess GTPase activity – fxn as molecular switches (ras, rab)
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What are the three distinct subunits of hetertrimeric G proteins?
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alpha, beta, gamma
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Explain how g proteins cause biological actions.
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domino effect, chain reaction – ligan binds to receptor > receptor releases alpha and beta/gamma complex > complexes go off to turn on other channels (AC)
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What isincreased in the cell when adenylate cyclase is activated by G proteins?
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cAMP
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What degrades cAMP?
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phosphodiesterase (PDE)
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What is the most important inhibition mechanism for G protein signaling?
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lowering AC activity
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What is the roll of the Beta-gamma dimer?
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activate GRK …lots of stuff
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Name proteins that regulate G proteins
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serine/threonine kinases
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what is the small G protein involved in membrane vesicle trafficking?
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rab(3)
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which toxins cause ADP-ribosylation of G proteins?
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cholera and pertussis bacterial toxins ARF: implicating in controlling membrane vesicle trafficking
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which small g protein mutation is found in 30% of human cancers?
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mutation of one of the three ras genes
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neurological d/o’s associated with g protein abnormality
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autism spectrum, epilepsy and macrophelogy

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