G protein coupling to M1 and M3 muscarinic receptors in sublingual glands.
G protein coupling to M1 and M3 muscarinic receptors in sublingual glands.
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DOI：
10.1152/ajpcell.2001.280.4.c884
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发表时间：
2001-04
期刊：
影响因子：
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通讯作者：
W. Luo;L. Latchney;D. Culp
中科院分区：
文献类型：
--
作者：
W. Luo;L. Latchney;D. Culp
Rat sublingual gland M2 and M3 muscarinic receptors each directly activate exocrine secretion. To investigate the functional role of coreceptor expression, we determined receptor-G protein coupling. Although membrane proteins of 40 and 41 kDa are ADP-ribosylated by pertussis toxin (PTX), and 44 kDa proteins by cholera toxin (CTX), both carbachol-stimulated high-affinity GTPase activity and the GTP-induced shift in agonist binding are insensitive to CTX or PTX. Carbachol enhances photoaffinity labeling ([alpha-(32)P]GTP-azidoaniline) of only 42-kDa proteins that are subsequently tractable to immunoprecipitation by antibodies specific for Galpha(q) or Galpha(11) but not Galpha(12) or Galpha(13). Carbachol-stimulated photoaffinity labeling as well as phosphatidylinositol 4,5-bisphosphate (PIP2) hydrolysis is reduced 55% and 60%, respectively, by M1 receptor blockade with m1-toxin. Galpha(q/11)-specific antibody blocks carbachol-stimulated PIP2 hydrolysis. We also provide estimates of the molar ratios of receptors to Galpha(q) and Galpha(11). Although simultaneous activation of M1 and M3 receptors is required for a maximal response, both receptor subtypes are coupled to Galpha(q) and Galpha(11) to stimulate exocrine secretion via redundant mechanisms.
