Endothelin 1 stimulates beta1Pix-dependent activation of Cdc42 through the G(salpha) pathway.
Beta1Pix (PAK-interacting exchange factor) is a recently identified guanine nucleotide exchange factor (GEF) for the Rho family small G protein Cdc42/Rac. On stimulation with extracellular signals, GEFs induce the exchange of guanosine diphosphate to guanosine triphosphate, resulting in the activation of the small guanosine 5C-triphosphatases. This activation enables the signal to propagate to downstream effectors. Herein, we show that G(salpha) stimulation by cholera toxin increased Cdc42 activation by endothelin-1 (ET-1), whereas pertussis toxin had no effect. H-89, a protein kinase A (PKA) inhibitor, strongly inhibited Cdc42 activation by ET-1. Moreover, the overexpression of beta1Pix enhanced ET-1-induced Cdc42 activation. The essential role of beta1Pix in ET-1-induced Cdc42 activation was evidenced by the blocking of Cdc42 activation in cells expressing beta1Pix mutant lacking the ability to bind PAK (beta1Pix SH3m[W43K]) or mutant lacking GEF activity (beta1PixdeltaDH). The overexpression of mutant lacking the pleckstrin homology domain beta1PixdeltaPH, which is unable to bind phospholipids, had no effect on Cdc42 activation. These results demonstrate that beta1Pix, along with PKA, plays a crucial role in the regulation of Cdc42 activation by ET-1.
Chahdi
Ahmed
A
Division of Nephrology, Department of Medicine, Kidney Disease Center, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, Wisconsin 53226, USA.
Sorokin
Andrey
A
D018797:Cell Cycle Proteins / Q000378:metabolism*; D002461:Cell Line, Transformed; D002472:Cell Transformation, Viral; D002772:Cholera Toxin / Q000494:pharmacology; D019332:Endothelin-1 / Q000494:pharmacology*; D019205:GTP-Binding Protein alpha Subunits, Gs / Q000378:metabolism*; D020662:Guanine Nucleotide Exchange Factors / Q000378:metabolism*; D006801:Humans; D050527:Mesangial Cells / Q000166:cytology* / Q000821:virology*; D064067:Rho Guanine Nucleotide Exchange Factors; D020764:cdc42 GTP-Binding Protein / Q000032:analysis / Q000378:metabolism*
D018797:Cell Cycle Proteins; D019332:Endothelin-1; D020662:Guanine Nucleotide Exchange Factors; D064067:Rho Guanine Nucleotide Exchange Factors; D002772:Cholera Toxin; D019205:GTP-Binding Protein alpha Subunits, Gs; D020764:cdc42 GTP-Binding Protein