Gi alpha 1 selectively couples somatostatin receptors to adenylyl cyclase in pituitary-derived AtT-20 cells.
Somatostatin (SRIF) receptors are coupled to the catalytic subunit of adenylyl cyclase via pertussis toxin-sensitive guanine nucleotide-binding regulatory proteins (G proteins). To identify which G proteins link SRIF receptors to adenylyl cyclase, G(o) alpha, Gi alpha, and its different subtypes were individually blocked in AtT-20 cell membranes with G alpha subtype-selective antisera. Antiserum directed against the carboxyl-terminal region of Gi alpha blocked SRIF inhibition of forskolin-stimulated adenylyl cyclase activity, and this effect was prevented by the peptide to which the antiserum was generated. However, antiserum directed against the carboxyl-terminal region of G(o) alpha did not affect SRIF inhibition of adenylyl cyclase activity, indicating that Gi alpha couples SRIF receptors to adenylyl cyclase but G(o) alpha does not. Peptide-directed antisera against Gi alpha 1 completely blocked SRIF inhibition of adenylyl cyclase activity. In contrast, antisera directed against either Gi alpha 2 or Gi alpha 3 did not affect the actions of SRIF. The results of these studies indicate that Gi alpha 1 selectively couples SRIF receptors to the catalytic subunit of adenylyl cyclase in AtT-20 cell membranes. Because previous studies have shown that SRIF receptors are able to couple to Gi alpha 1, Gi alpha 3, and G(o) alpha, the results suggest that different G proteins may specify the coupling of SRIF receptors to distinct cellular effector systems.
Tallent
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Department of Pharmacology, University of Pennsylvania School of Medicine, Philadelphia 19104.
Reisine
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D037361:Adenylate Cyclase Toxin; D000262:Adenylyl Cyclases / Q000378:metabolism*; D000595:Amino Acid Sequence; D000818:Animals; D015153:Blotting, Western; D002462:Cell Membrane / Q000201:enzymology; D002478:Cells, Cultured; D005576:Colforsin / Q000494:pharmacology; D004591:Electrophoresis, Polyacrylamide Gel; D019204:GTP-Binding Proteins / Q000378:metabolism*; D051379:Mice; D008969:Molecular Sequence Data; D037342:Pertussis Toxin; D010902:Pituitary Gland / Q000166:cytology / Q000201:enzymology*; D051381:Rats; D017981:Receptors, Neurotransmitter / Q000378:metabolism*; D017481:Receptors, Somatostatin; D013004:Somatostatin / Q000378:metabolism*; D010566:Virulence Factors, Bordetella / Q000494:pharmacology
D037361:Adenylate Cyclase Toxin; D017981:Receptors, Neurotransmitter; D017481:Receptors, Somatostatin; D010566:Virulence Factors, Bordetella; D005576:Colforsin; D013004:Somatostatin; D037342:Pertussis Toxin; D019204:GTP-Binding Proteins; D000262:Adenylyl Cyclases