Regulation of RhoA Signaling by the cAMP-dependent Phosphorylation of RhoGDIα

• Published in: The Journal of biological chemistry Vol. 287; no. 46; pp. 38705 - 38715
• Main Authors: Oishi, Atsuro, Makita, Noriko, Sato, Junichiro, Iiri, Taroh
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 09.11.2012; American Society for Biochemistry and Molecular Biology
• Subjects: Animals; cAMP; Cattle; Cell Biology; Cell Line; Cell Rounding; Cellular Regulation; Chlorocebus aethiops; COS Cells; Cyclic AMP - metabolism; G Protein-coupled Receptors (GPCR); G Proteins; GTP-Binding Proteins - metabolism; HEK293 Cells; Humans; Phosphorylation; Protein Binding; Rats; Rho; rho Guanine Nucleotide Dissociation Inhibitor alpha - metabolism; RhoA; rhoA GTP-Binding Protein - metabolism; RhoGDIa; RNA, Small Interfering - metabolism; Signal Transduction; G Protein-coupled Receptors (GPCR); Phosphorylation; G Proteins; Rho; Cellular Regulation; RhoGDIa; cAMP; Cell Rounding; RhoA
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M112.401547

RhoA plays a pivotal role in regulating cell shape and movement. Protein kinase A (PKA) inhibits RhoA signaling and thereby induces a characteristic morphological change, cell rounding. This has been considered to result from cAMP-induced phosphorylation of RhoA at Ser-188, which induces a stable RhoA-GTP-RhoGDIα complex and sequesters RhoA to the cytosol. However, few groups have shown RhoA phosphorylation in intact cells. Here we show that phosphorylation of RhoGDIα but not RhoA plays an essential role in the PKA-induced inhibition of RhoA signaling and in the morphological changes using cardiac fibroblasts. The knockdown of RhoGDIα by siRNA blocks cAMP-induced cell rounding, which is recovered by RhoGDIα-WT expression but not when a RhoGDIα-S174A mutant is expressed. PKA phosphorylates RhoGDIα at Ser-174 and the phosphorylation of RhoGDIα is likely to induce the formation of a active RhoA-RhoGDIα complex. Our present results thus reveal a principal molecular mechanism underlying Gs/cAMP-induced cross-talk with Gq/G13/RhoA signaling. Background: cAMP-induced phosphorylation of RhoA has been considered to inhibit RhoA signaling, causing cell rounding. Results: Knockdown of RhoGDIα blocks cAMP-induced cell rounding, and RhoGDIα-WT expression but not RhoGDIα-S174A expression recovers. Conclusion: Phosphorylation of RhoGDIα likely inhibits RhoA by stabilizing a active RhoA-RhoGDIα complex. Significance: This may underlie Gs/cAMP-induced cross-talk with Gq/G13/RhoA signaling.