TY - JOUR T1 - G<em>α</em><sub>12</sub> Structural Determinants of Hsp90 Interaction Are Necessary for Serum Response Element–Mediated Transcriptional Activation JF - Molecular Pharmacology JO - Mol Pharmacol SP - 586 LP - 597 DO - 10.1124/mol.113.088443 VL - 85 IS - 4 AU - Ellyn R. Montgomery AU - Brenda R. S. Temple AU - Kimberly A. Peters AU - Caitlin E. Tolbert AU - Brandon K. Booker AU - Joseph W. Martin AU - Tyler P. Hamilton AU - Alicia C. Tagliatela AU - William C. Smolski AU - Stephen L. Rogers AU - Alan M. Jones AU - Thomas E. Meigs Y1 - 2014/04/01 UR - http://molpharm.aspetjournals.org/content/85/4/586.abstract N2 - The G12/13 class of heterotrimeric G proteins, comprising the α-subunits Gα12 and Gα13, regulates multiple aspects of cellular behavior, including proliferation and cytoskeletal rearrangements. Although guanine nucleotide exchange factors for the monomeric G protein Rho (RhoGEFs) are well characterized as effectors of this G protein class, a variety of other downstream targets has been reported. To identify Gα12 determinants that mediate specific protein interactions, we used a structural and evolutionary comparison between the G12/13, Gs, Gi, and Gq classes to identify “class-distinctive” residues in Gα12 and Gα13. Mutation of these residues in Gα12 to their deduced ancestral forms revealed a subset necessary for activation of serum response element (SRE)–mediated transcription, a G12/13-stimulated pathway implicated in cell proliferative signaling. Unexpectedly, this subset of Gα12 mutants showed impaired binding to heat-shock protein 90 (Hsp90) while retaining binding to RhoGEFs. Corresponding mutants of Gα13 exhibited robust SRE activation, suggesting a Gα12-specific mechanism, and inhibition of Hsp90 by geldanamycin or small interfering RNA–mediated lowering of Hsp90 levels resulted in greater downregulation of Gα12 than Gα13 signaling in SRE activation experiments. Furthermore, the Drosophila G12/13 homolog Concertina was unable to signal to SRE in mammalian cells, and Gα12:Concertina chimeras revealed Gα12-specific determinants of SRE activation within the switch regions and a C-terminal region. These findings identify Gα12 determinants of SRE activation, implicate Gα12:Hsp90 interaction in this signaling mechanism, and illuminate structural features that arose during evolution of Gα12 and Gα13 to allow bifurcated mechanisms of signaling to a common cell proliferative pathway. ER -