title: Tyrosine kinase activation by the angiotensin II receptor in the absence of calcium signaling.
abstract: The angiotensin II type 1 (AT(1)) receptor signals via heterotrimeric G-proteins and intracellular tyrosine kinases. Here, we investigate a modified AT(1) receptor, termed M5, where the last five tyrosines (residues 292, 302, 312, 319, and 339) within the intracellular carboxyl tail have been mutated to phenylalanine. This receptor did not elevate cytosolic free calcium or inositol phosphate production in response to angiotensin II, suggesting an uncoupling of the receptor from G-protein activation. Despite this, the M5 receptor still activated tyrosine kinases, induced STAT1 tyrosine phosphorylation, and stimulated cell proliferation. We also studied another AT(1) mutant receptor, D74E, stably expressed in Chinese hamster ovarian cells and a fibroblast cell line from mice with a genetic inactivation of Galpha(q/11). Both cell lines have a deficit in calcium signaling and in G-protein activation, and yet in both cell lines, angiotensin II induced the time-dependent tyrosine phosphorylation of STAT1. These studies are the first to show the ability of a seven-transmembrane receptor to activate intracellular tyrosine kinase pathways in the absence of a G-protein-coupled rise in intracellular calcium.
authors.affiliation: Department of Pathology and Laboratory Medicine, Emory University School of Medicine, Atlanta, Georgia 30322, USA.
authors.forename: T N
authors.initials: TN
authors.lastname: Doan
authors.forename: M S
authors.initials: MS
authors.lastname: Ali
authors.forename: K E
authors.initials: KE
authors.lastname: Bernstein
mesh_terms: D000255:Adenosine Triphosphate / Q000494:pharmacology; D019943:Amino Acid Substitution; D000804:Angiotensin II / Q000494:pharmacology*; D000818:Animals; D016466:CHO Cells; D002118:Calcium / Q000378:metabolism; D020013:Calcium Signaling / Q000187:drug effects / Q000502:physiology*; D002460:Cell Line; D006224:Cricetinae; D004268:DNA-Binding Proteins / Q000378:metabolism; D004789:Enzyme Activation; D005347:Fibroblasts; D043802:GTP-Binding Protein alpha Subunits, Gq-G11; D020962:Heterotrimeric GTP-Binding Proteins / Q000172:deficiency / Q000378:metabolism; D051379:Mice; D018345:Mice, Knockout; D016297:Mutagenesis, Site-Directed; D019000:Phosphotyrosine / Q000378:metabolism; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D044140:Receptor, Angiotensin, Type 1; D044139:Receptor, Angiotensin, Type 2; D011945:Receptors, Angiotensin / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D050794:STAT1 Transcription Factor; D015534:Trans-Activators / Q000378:metabolism; D014162:Transfection; D014443:Tyrosine
chemical_list: D004268:DNA-Binding Proteins; D044140:Receptor, Angiotensin, Type 1; D044139:Receptor, Angiotensin, Type 2; D011945:Receptors, Angiotensin; D011994:Recombinant Proteins; D050794:STAT1 Transcription Factor; C494080:Stat1 protein, mouse; D015534:Trans-Activators; D000804:Angiotensin II; D019000:Phosphotyrosine; D014443:Tyrosine; D000255:Adenosine Triphosphate; D011505:Protein-Tyrosine Kinases; D043802:GTP-Binding Protein alpha Subunits, Gq-G11; D020962:Heterotrimeric GTP-Binding Proteins; D002118:Calcium