title: Contrasting signaling pathways of alpha1A- and alpha1B-adrenergic receptor subtype activation of phosphatidylinositol 3-kinase and Ras in transfected NIH3T3 cells.
abstract: Activation of protein kinases is an important intermediate step in signaling pathways of many G protein-coupled receptors including alpha1-adrenergic receptors. The present study was designed to investigate the capacity of the three cloned subtypes of human alpha1-receptors, namely, alpha1A, alpha1B and alpha1D to activate phosphatidylinositol 3-kinase (PI 3-kinase) and p21ras in transfected NIH3T3 cells. Norepinephrine activated PI 3-kinase in cells expressing human alpha1A and alpha1B via pertussis toxin-insensitive G proteins; alpha1D-receptors did not detectably activate this kinase. Transient transfection of NIH 3T3 cells with the alpha-subunit of the G protein transducin (alpha(t)) a scavenger of betagamma-subunits released from activated G proteins, inhibited alpha1B-receptor but not alpha1A-receptor-stimulated PI 3-kinase activity. Stimulation of both alpha1A- and alpha1B-receptors activated p21ras and stimulated guanine nucleotide exchange on Ras protein. Overexpression of a dominant negative mutant of p21ras attenuated alpha1B-receptor but not alpha1A-receptor activation of PI 3-kinase. Overexpression of a dominant negative mutant of PI 3-kinase attenuated alpha1A- but not alpha1B-receptor-stimulated mitogen-activated protein kinase activity. These results demonstrate the capacity for heterologous signaling of the alpha1-adrenergic receptor subtypes in promoting cellular responses in NIH3T3 cells.
authors.affiliation: Geriatric Research, Education and Clinical Center, Veterans Affairs Palo Alto Health Care System, California 94304, USA.
authors.forename: Z W
authors.initials: ZW
authors.lastname: Hu
authors.forename: X Y
authors.initials: XY
authors.lastname: Shi
authors.forename: R Z
authors.initials: RZ
authors.lastname: Lin
authors.forename: B B
authors.initials: BB
authors.lastname: Hoffman
mesh_terms: D016475:3T3 Cells / Q000187:drug effects / Q000378:metabolism; D000316:Adrenergic alpha-Agonists / Q000494:pharmacology; D000818:Animals; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000187:drug effects / Q000378:metabolism; D017868:Cyclic AMP-Dependent Protein Kinases / Q000235:genetics / Q000378:metabolism; D004789:Enzyme Activation / Q000187:drug effects; D019204:GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism; D006801:Humans; D051379:Mice; D009154:Mutation; D009638:Norepinephrine / Q000494:pharmacology; D037342:Pertussis Toxin; D019869:Phosphatidylinositol 3-Kinases / Q000187:drug effects / Q000378:metabolism*; D016283:Proto-Oncogene Proteins p21(ras) / Q000235:genetics / Q000378:metabolism*; D018340:Receptors, Adrenergic, alpha-1 / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction; D014162:Transfection; D010566:Virulence Factors, Bordetella / Q000494:pharmacology; D051552:beta-Adrenergic Receptor Kinases
chemical_list: C547713:ADRA1A protein, human; C547716:ADRA1B protein, human; C547719:ADRA1D protein, human; C547714:Adra1a protein, mouse; C547717:Adra1b protein, mouse; C547720:Adra1d protein, mouse; D000316:Adrenergic alpha-Agonists; D018340:Receptors, Adrenergic, alpha-1; D011994:Recombinant Proteins; D010566:Virulence Factors, Bordetella; D037342:Pertussis Toxin; D019869:Phosphatidylinositol 3-Kinases; D017868:Cyclic AMP-Dependent Protein Kinases; D051552:beta-Adrenergic Receptor Kinases; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D019204:GTP-Binding Proteins; C501009:HRAS protein, human; D016283:Proto-Oncogene Proteins p21(ras); D009638:Norepinephrine