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This Article Full Text Full Text (PDF) All Versions of this Article: 291/4/E704    most recent 00048.2006v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Lenard, N. R. Articles by Gettys, T. W. Search for Related Content PubMed PubMed Citation Articles by Lenard, N. R. Articles by Gettys, T. W.

Differential coupling of _3A- and _3B-adrenergic receptors to endogenous and chimeric Gs and Gi

Laboratories of ¹Adipocyte Signaling and ²Autonomic Neuroscience, Pennington Biomedical Research Center, Baton Rouge, Louisiana

Submitted 1 February 2006 ; accepted in final form 8 May 2006

Chimeric G proteins made by replacing the COOH-terminal heptapeptide of Gq with the COOH-terminal heptapeptide of Gs or Gi were used to assess the relative coupling of ₃-adrenergic receptor (₃-AR) splice variants (_3A and _3B) to Gs and Gi. The Gq/s and Gq/i chimeras transformed the response to receptor activation from regulation of adenylyl cyclase to mobilization of intracellular calcium (Ca²⁺_i). Complementary high-throughput and single-cell approaches were used to evaluate agonist-induced coupling of the receptor to the G protein chimeras. In cells stably transformed with rat ₃-AR, transfected with the G protein chimeras, and evaluated using a scanning fluorometer, ₃-AR-induced coupling to Gq/s produced a rapid eightfold increase in Ca²⁺_i followed by a slow decay to levels 25% above baseline. Gq/i also linked rat ₃-AR to mobilization of Ca²⁺_i in a similar time- and agonist-dependent manner, but the net 2.5-fold increase in Ca²⁺_i was only 30% of the response obtained with Gq/s. Activation of the rat ₃-AR also increased GTP binding to endogenous Gi threefold in membranes from CHO cells stably transformed with the receptor. A complementary single-cell imaging approach was used to assess the relative coupling of mouse _3A- and _3B-AR to Gi under conditions established to produce equivalent agonist-dependent coupling of the receptor splice variants to Gq/s and to increases in intracellular cAMP through endogenous Gs. The _3A- and _3B-AR coupled equivalently to Gq/i, but the temporal patterns of Ca²⁺_i mobilization indicated that coupling was significantly less efficient than coupling to Gq/s. Collectively, these findings indicate less efficient but equivalent coupling of _3A- and _3B-AR to Gi vs. Gs and suggest that differential expression of the splice variants would not produce local differences in signaling networks linked to ₃-AR activation.

-adrenergic receptor; G proteins; cyclic adenosine monophosphate; signaling plasticity