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Shpakov AO, Korol'kov VI, Plesneva SA, Kuznetsova LA, Pertseva MN: Effects of the C-terminal peptide of the alphaS subunit of the G protein on the regulation of adenylyl cyclase and protein kinase A activities by biogenic amines and glucagon in mollusk and rat muscles. Neurosci Behav Physiol. 2005 Feb;35(2):177-86.
The C-terminal parts of the a subunits of heteromeric G proteins play an important role in the functional linkage of G proteins with receptors of the serpentine type. The present report describes studies of the effects of the C-terminal octapeptide 387-394 of the alphaS subunit of the mammalian G protein on the transmission of the hormonal signal via the hormone-sensitive adenylyl cyclase signal system, whose major components are receptors of the serpentine type, G proteins, and the enzymes adenylyl cyclase and protein kinase A. The peptide synthesized here, 387-394 amide (10 (-7) - 10 (-4) M), dose-dependently decreased adenylyl cyclase and protein kinase A activities stimulated by serotonin and glucagon in smooth muscle from the freshwater bivalve mollusk Anodonta cygnea and by the beta agonist isoproterenol in rat skeletal muscle. At a concentration as low as 10 (-7) M, the peptide released potentiation of the stimulatory effects of hormones on adenylyl cyclase activity due to the non-hydrolyzable guanine nucleotide analog Gpp [NH] p. At the same time, it had almost no effect on the stimulation of adenylyl cyclase activity by non-hormonal agents (NaF, Gpp [NH] p, and forskolin). The inhibitory effects of hormones on adenylyl cyclase and protein kinase A activities persisted in the presence of the peptide. Our data demonstrate the importance of the C-terminal part of the alphaS subunit of the stimulatory G protein for its functional linkage with receptors of the serpentine type and throw light on the molecular mechanisms of the interactions between G proteins and receptors. |
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