title: The role of beta(1)Pix/caveolin-1 interaction in endothelin signaling through Galpha subunits.
abstract: Endothelin-1 (ET-1) is a potent mitogen that transmits signals through its cognate G protein-coupled receptors to stimulate extracellular signal-regulated kinase Erk1/2. Endothelin-1 receptors (ET-Rs) are known to interact with caveolin-1 and co-localize in caveolae which integrate different receptor and signaling proteins. We have recently shown that beta(1)Pix binds specifically to ET-Rs. Here, we show that beta(1)Pix binding to caveolin-1 is dependent on heterotrimeric G proteins activation state. beta(1)Pix interaction with different G proteins is increased in the presence of the G protein activator AMF. Moreover, extraction of cholesterol with methyl-beta-cyclodextrin disrupts the binding of beta(1)Pix to Galpha(q), Galpha(12) and phospho-Erk1/2 but not the binding of beta(1)Pix to G(beta1). The disruption of beta(1)Pix dimerization strongly reduced the binding of caveolin-1, Galpha(q) and Galpha(12). Constitutively active mutants of Galpha(q) and Galpha(12) increased Cdc42 activation when co-expressed with beta(1)Pix but not in the presence of beta(1)Pix dimerization deficient mutant beta(1)PixDelta (602-611). ET-1 stimulation increased the binding of phosphorylated Erk1/2 to beta(1)Pix but not to beta(1)PixDelta (602-611). RGS3 decreased ET-1-induced Cdc42 activation. These results strongly suggest that the activation of ET-Rs leads to the compartmentalization and the binding of Galpha(q) to beta(1)Pix in caveolae, where dimeric beta(1)Pix acts as platform to facilitate the binding and the activation of Erk1/2.
authors.affiliation: Division of Nephrology and Kidney Disease Center, Department of Medicine, Medical College of Wisconsin, Milwaukee, WI 53226, United States.
authors.forename: Ahmed
authors.initials: A
authors.lastname: Chahdi
authors.forename: Andrey
authors.initials: A
authors.lastname: Sorokin
mesh_terms: D051242:Caveolin 1 / Q000378:metabolism*; D002478:Cells, Cultured; D019332:Endothelin-1 / Q000378:metabolism*; D044365:GTP-Binding Protein alpha Subunits, G12-G13 / Q000378:metabolism; D043802:GTP-Binding Protein alpha Subunits, Gq-G11 / Q000378:metabolism*; D019204:GTP-Binding Proteins / Q000378:metabolism; D020690:GTPase-Activating Proteins / Q000378:metabolism; D020662:Guanine Nucleotide Exchange Factors / Q000378:metabolism*; D006801:Humans; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism; D055503:Protein Multimerization; D020710:RGS Proteins; D064067:Rho Guanine Nucleotide Exchange Factors; D015398:Signal Transduction; D020764:cdc42 GTP-Binding Protein / Q000378:metabolism
chemical_list: C495540:CAV1 protein, human; D051242:Caveolin 1; D019332:Endothelin-1; D020690:GTPase-Activating Proteins; D020662:Guanine Nucleotide Exchange Factors; D020710:RGS Proteins; C485898:RGS3 protein, human; D064067:Rho Guanine Nucleotide Exchange Factors; D048052:Mitogen-Activated Protein Kinase 3; D019204:GTP-Binding Proteins; D044365:GTP-Binding Protein alpha Subunits, G12-G13; D043802:GTP-Binding Protein alpha Subunits, Gq-G11; D020764:cdc42 GTP-Binding Protein