Term
| glycogenolysis results from |
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Definition
| activation of glycogen phosphorylase in response to catecholamines (external cell stimulus - epi) |
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Term
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Definition
| Mg2+-ATP by adenylyl cyclase. 2 terminal phosphates are removed, generating pyrophosphate. a link is formed between 5'hydroxymethyl group and 3'phosphate, hence 3'5'cAMP. |
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Term
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Definition
| hydrolysis, catalyzed by phosphodiesterases (which may be hormone sensitive - for instance, activated by insulin). process yields AMP. |
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Term
| cAMP synthesis/degradation reversible? |
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Definition
| yes to both, but for both the forward reaction is favored greatly. |
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Term
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Definition
| interacts with beta-adrenergic receptor, causing it to dissociate from its ligand, epi. binds gtp (nucleotide exchange of gdp for gtp, which is then hydrolyzable). activates adenylate cyclase, dependent on gtp. turns itself off by hydrolyzing gtp. |
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Term
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Definition
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Term
| non-hydrolyzable GTP analogues |
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Definition
| very potent activators of adenylyl cyclase |
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Term
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Definition
| alpha, beta and gamma subunits |
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Term
| alpha subunit of g protein (2) |
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Definition
| Gs alpha and Gi alpha: stimulate/inhibit adenylate cyclase |
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Term
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Definition
| receptor binds hormone, GDP bound by alpha is replaced by GTP, GTP-bound alpha releases from beta-gamma and activates an effector, alpha hydrolyzes the GTP (returning it to the GDP-bound state) |
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Term
| heterotrimeric G proteins relay signals from ____ receptors |
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Definition
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Term
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Definition
| catalyzes the ADP-ribosylation of Gs alpha, which inhibits GTPase acitivity in gut lumen (never gets into the blood stream); = always on. NAD+ is the ADP donor. |
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Term
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Definition
| lymphocytosis, impaired cilia function in lungs and hypoglycemia + cough. pertussis toxin catalyzes adp-ribosylation of Gi alpha via NAD+ donor. blocks Gi alpha's ability to exchange GDP for GTP, so the subunit doesn't work and there's no inhibition of adenylate cyclase = always on. systemic. |
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Term
| rhodopsin-transducin system / toxic effects |
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Definition
| rhodopsin (receptor in rods in the retina) "captures" a photon, causing isomerization. transducin is the g-protein (t-alpha subunit!!!). nucleotide exchange > alpha subunit dissociates >>> phosphodiesterase is the effector; it hydrolyzes cGMP. sodium channels close due to low levels of cGMP. hyperpolarization = vision. TRANSDUCIN IS A SUBSTRATE FOR CTX and PTX. |
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Term
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Definition
| activated by chemoreceptors in the cribiform plate. cAMP > opening of sodium channel |
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Term
| adenylate cyclase is activated how |
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Definition
| INdirectly by hormones/GTP; directly by forming a complex with Gs alpha. |
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Term
| biological actions of cAMP are mediated by |
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Definition
| PKA (cAMP dependent protein kinase) |
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Term
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Definition
| serine/threonine kinase. inactive form is heterotetramer: R2-C2. R = regulatory, binds cAMP. C = catalytic kinase, catalyzes ATP > ADP + protein-P. /// 2 Rs form a complex with cAMP, leaving the Cs and activating them. |
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Term
| while bound to R, cAMP is ____ from ____. dissociation of cAMP from R is ____ |
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Definition
| protected from hydrolysis. readily reversible. |
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Term
| PKA can phosphorylate and regulate |
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Definition
| enzymes, receptors, ion channels, transporters and transcription factors. FBPase2, phosphorylase kinase, acetyl coa carboxylase |
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Term
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Definition
| cAMP response element binding protein; contains 4 leucine zipper regions. |
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Term
| phosphorylation by PKA in response to cAMP activates |
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Definition
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Term
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Definition
| 60% same between yeast and humans. one of the "small G-proteins". activation of GAP induces GTPase activity (the off switch). mutations in ras most often cause loss of GTPase activity in growth hormone receptors- lung, colon, pancreas cancers |
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Term
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Definition
| GTPase Activating Protein in ras |
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Term
| altered g-protein signaling is involved in ... (3) |
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Definition
| infectious diseases, cancer, endocrine disorders (adenomas, autonomous end-organ function, hormone resistance) |
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Term
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Definition
| Gs alpha defect: mutation = truncated protein. results in short stature, obesity, no knuckles, migratory subcutaneous ossification, resistance to PTH, TSH, LH (all cAMP-mediated hormones) (elevated PTH), hypocalcemia (because PTH regulates serum calcium) |
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Term
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Definition
| autonomous endocrine gland activity due to a mutation that activates Gs alpha. = pseudohypopara (inactivating at 37C) + testitoxicosis. mutation is activating at 33C = hypergonadism (precocious puberty). presents with pituitary adenomas, sometimes essential hypertension and sometimes night blindness |
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Term
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Definition
| like longterm dating. come together easily and stay together long time |
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Term
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Definition
| GTPase activity shuts it off |
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Term
| Albright's hereditary osteodystrophy |
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Definition
| pseudohypoparathyroidism. gene that encodes Gs alpha is tissue-specific such that maternally inherited mutations cause hormone resistance but paternally inherited mutations ONLY cause osteodystrophy. |
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