Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P61278 (somatostatin)
 22,083 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Guanine nucleotide binding (G) proteins are heterotrimers that couple a wide range of receptors to ionic channels. The coupling may be indirect, via cytoplasmic agents, or direct, as has been shown for two K+ channels and two Ca2+ channels. One example of direct G protein gating is the atrial muscarinic K+ channel K+[ACh], an inwardly rectifying K+ channel with a slope conductance of 40 pS in symmetrical isotonic K+ solutions and a mean open lifetime of 1.4 ms at potentials between -40 and -100 mV. Another is the clonal GH3 muscarinic or somatostatin K+ channel, also inwardly rectifying but with a slope conductance of 55 pS. A G protein, Gk, purified from human red blood cells (hRBC) activates K+ [ACh] channels at subpicomolar concentrations; its alpha subunit is equipotent. Except for being irreversible, their effects on gating precisely mimic physiological gating produced by muscarinic agonists. The alpha k effects are general and are similar in atria from adult guinea pig, neonatal rat, and chick embryo. The hydrophilic beta gamma from transducin has no effect while hydrophobic beta gamma from brain, hRBCs, or retina has effects at nanomolar concentrations which in our hands cannot be dissociated from detergent effects. An anti-alpha k monoclonal antibody blocks muscarinic activation, supporting the concept that the physiological mediator is the alpha subunit not the beta gamma dimer. The techniques of molecular biology are now being used to specify G protein gating. A "bacterial" alpha i-3 expressed in Escherichia coli using a pT7 expression system mimics the gating produced by hRBC alpha k.
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PMID:Roles of G proteins in coupling of receptors to ionic channels and other effector systems. 217 76

Somatostatin, localized throughout the central and peripheral nervous systems, has been found in neurons of the vagal inhibitory pathway of the heart and has been shown to have negative inotopic effects in cardiac tissue. Using patch clamp techniques we show that somatostatin activates an inwardly rectifying K+ channel in rat atrial cells. Loss of somatostatin-induced K+ channel activity in excised inside-out patches is restored by the addition of GTP to the bath. Pertussis toxin pretreatment blocked GTP-dependent somatostatin activation of the inwardly rectifying K+ channel. This K+ channel has a conductance of 34 pS and a mean open time of approximately 1 ms. It is apparently the same K+ channel activated by muscarinic and adenosine receptors in atrial and cardiac pacemaker cells. Thus, atrial cells have at least three receptors which act via pertussis toxin-sensitive G proteins to activate the same class of K+ channels.
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PMID:Somatostatin activates an inwardly rectifying K+ channel in neonatal rat atrial cells. 257 74