TY - JOUR T1 - Gα<sub>12</sub> Structural Determinants of Hsp90 Interaction are Necessary for Serum Response Element-mediated Transcriptional Activation JF - Molecular Pharmacology JO - Mol Pharmacol DO - 10.1124/mol.113.088443 SP - mol.113.088443 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 - 2014/01/01 UR - http://molpharm.aspetjournals.org/content/early/2014/01/16/mol.113.088443.abstract N2 - The G12/13 class of heterotrimeric G proteins, comprised of 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 have been reported. To identify Gα12 determinants that mediate specific protein interactions, we utilized 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 siRNA-mediated lowering of Hsp90 levels resulted in greater down-regulation 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 -