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8 Cards in this Set
- Front
- Back
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GPCR structure |
-7 TMDs; ligand binding site is within the PM --> interactions with the TMDs -N-terminal outside that is impt for some NTs; C-terminal cytosolic that is site of G-protein binding/activation -at rest alpha is bound to beta and gamma and GDP; when GPCR is activated it releases the alpha from beta gamma (still at PM) and also releases GDP, picking up GTP; alpha-GTP has effects -several genes for alpha, beta, gamma, and receptor; creates a lot of complexity! -gamma is prenylated --> holds beta-gamma to membrane -activation is terminated by phosphorylation by a GPCR receptor kinase (GRK) |
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heterotrimeric G-protein signaling to adenylate cyclase |
-typical downstream response from beta adrenergic receptors -activation operates through alpha-s subunit -inhibition through alpha-i subunit |
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heterotrimeric G-protein signaling to phospholipases |
-activation of phospholipase C which will cleave PIP2 into diacylglycerol (DAG) and inositol triphosphate (IP3) -protein kinase C is activated by DAG and increased intracellular Ca++ release by IP3 -typically initiated by alpha-q or alpha-p |
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heterotrimeric G-protein signaling to phosphodiesterases |
-e.g. light system -opsin (GPCR) activates transducin (GP) -transducin activates phosphodiesterase which reduced cGMP and causes c-GMP gated (nonspecific) cation channels to close -leads to hyperpolarizing the cell -reduce Ca++ flow into the cell and thus neurotransmitter release |
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GRKs |
GPC receptor kinase -phosphorylates GPCR to terminate signal -only 7 genes (2 hogged by visual system) -3 classes: rhodopsin kinase (GRK1) and cone kinase (GRK7) (visual system); beta-adrenergic receptor kinases (GRK 2, 3); GRKs 4,5,6 |
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arrestins |
-binds and internalizes phospho-GPCR -can also have downstream actions once pulled into the cell, mostly on kinases -only 4 genes: 2 visual and beta-arrestins 1 and 2 |
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Rhodopsin |
-light flash causes hyperpolarization (in a graded respone: bright flash causes more hyperpolarization) -hyperpolarization stops nuerotransmitter release -11-cis retinal is bound within the opsin |
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GPCR function |
-ligand binding activates adjacent alpha-beta-gamma complex -alpha-GTP has downstream effects by interacting with a variety of effectors -causes amplification of the signal -activation is terminated by phosphorylation by a GPCR receptor kinase (GRK) -phospho-GPCR is then bound and internalized by an arrestin -phospho-GPCRs are then either recycled to the cell surface or degraded |
