title: Up-regulation of the angiotensin II type 1 receptor by the MAS proto-oncogene is due to constitutive activation of Gq/G11 by MAS.
abstract: Coexpression of the MAS proto-oncogene with the angiotensin II type 1 (AT(1)) receptor in CHO-K1 cells has been reported to increase the number of [(3)H]angiotensin II-binding sites, although MAS does not bind [(3)H]angiotensin II. In HEK293 cells stably expressing AT(1) receptor-cyan fluorescent protein (CFP), MAS-yellow fluorescent protein (YFP) expression from an inducible locus caused strong up-regulation of AT(1) receptor-CFP amounts and [(3)H]angiotensin II binding levels. The time course of AT(1) receptor-CFP up-regulation was also markedly slower than that of induction of MAS expression. These effects were not mimicked by induced expression of I138D MAS-YFP, a mutant unable to cause constitutive loading of [(35)S]guanosine 5'-O-(thiotriphosphate) onto the phospholipase Cbeta-linked G protein Galpha(11). Protein kinase C (PKC) inhibitors and the selective Galpha(q)/Galpha(11) inhibitor YM-254890 fully blocked MAS-induced up-regulation of AT(1) receptor-CFP amounts, whereas the PKC activator phorbol 12-myristate 13-acetate produced strong up-regulation of AT(1) receptor-CFP without induction of MAS-YFP expression and in the presence of I138D MAS-YFP. The C-terminal tail of the AT(1) receptor is a known target for PKC-mediated phosphorylation. In cells stably expressing a C-terminally truncated version of the AT receptor, induction of MAS expression did not up-regulate the truncated construct levels. These data demonstrate that the ability of MAS to up-regulate AT(1) receptor levels reflects the constitutive capacity of MAS to activate Galpha(q)/Galpha(11) and hence stimulate PKC-dependent phosphorylation of the AT(1) receptor.
authors.affiliation: Division of Biochemistry and Molecular Biology, Institute of Biomedical and Life Sciences, University of Glasgow, Glasgow G12 8QQ, Scotland, United Kingdom.
authors.forename: Meritxell
authors.initials: M
authors.lastname: Canals
authors.forename: Laura
authors.initials: L
authors.lastname: Jenkins
authors.forename: Elaine
authors.initials: E
authors.lastname: Kellett
authors.forename: Graeme
authors.initials: G
authors.lastname: Milligan
mesh_terms: D000818:Animals; D019921:Biotinylation; D016466:CHO Cells; D002460:Cell Line; D006224:Cricetinae; D004797:Enzyme-Linked Immunosorbent Assay; D043802:GTP-Binding Protein alpha Subunits, Gq-G11 / Q000378:metabolism*; D006801:Humans; D008856:Microscopy, Fluorescence; D011493:Protein Kinase C / Q000378:metabolism; D000090063:Proto-Oncogene Mas; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D044140:Receptor, Angiotensin, Type 1 / Q000378:metabolism*; D043562:Receptors, G-Protein-Coupled / Q000378:metabolism*; D015854:Up-Regulation
chemical_list: C000715470:MAS1 protein, human; D000090063:Proto-Oncogene Mas; D011518:Proto-Oncogene Proteins; D044140:Receptor, Angiotensin, Type 1; D043562:Receptors, G-Protein-Coupled; D011493:Protein Kinase C; D043802:GTP-Binding Protein alpha Subunits, Gq-G11