A role for guanyl nucleotide-binding regulatory protein beta- and gamma-subunits in the expression of the adrenocorticotropin receptor.
Mutant Y1 mouse adrenocortical tumor cells, isolated on the basis of their resistance to the growth-inhibitory effects of forskolin, arise from single mutational events. These mutants present complex phenotypes in which the activity of Gbeta/gamma is impaired, ACTH receptor gene expression is markedly diminished, and ACTH-responsive adenylyl cyclase activity is lost. In this study, we have tested the hypothesis that the impairment in Gbeta/gamma activity is responsible for the loss of ACTH receptor gene expression and ACTH-responsive adenylyl cyclase activity. Transfection of one of the mutant clones with expression vectors encoding either Gbeta1 or Gbeta2 together with Ggamma2 increased ACTH receptor expression and restored ACTH-responsive adenylyl cyclase activity. Interestingly, either Gbeta2 or Ggamma2 alone was effective. These results thus support the hypothesis that the impairment in Gbeta/gamma activity is responsible for the loss of ACTH receptor expression. A luciferase reporter plasmid driven by the proximal promoter region of the mouse ACTH receptor gene was expressed poorly in the mutants compared with parental Y1 cells, suggesting that the Gbeta/gamma defect compromised transcriptional activity at the proximal promoter region of the ACTH receptor gene.
Qiu
R
R
Banting and Best Department of Medical Research, University of Toronto, Ontario, Canada.
Frigeri
C
C
Schimmer
B P
BP
D000262:Adenylyl Cyclases / Q000378:metabolism; D000324:Adrenocorticotropic Hormone / Q000494:pharmacology; D000818:Animals; D002417:Cattle; D000242:Cyclic AMP / Q000378:metabolism; D019204:GTP-Binding Proteins / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D015870:Gene Expression; D005822:Genetic Vectors; D006801:Humans; D008156:Luciferases / Q000235:genetics; D051379:Mice; D008969:Molecular Sequence Data; D009154:Mutation; D011401:Promoter Regions, Genetic; D012333:RNA, Messenger / Q000032:analysis; D018043:Receptors, Corticotropin / Q000235:genetics* / Q000502:physiology; D014162:Transfection
D012333:RNA, Messenger; D018043:Receptors, Corticotropin; D000324:Adrenocorticotropic Hormone; D000242:Cyclic AMP; D008156:Luciferases; D019204:GTP-Binding Proteins; D000262:Adenylyl Cyclases