A G?12-specific Binding Domain in AKAP-Lbc and p114RhoGEF.

ABSTRACT: AKAP-Lbc is a Rho-activating guanine nucleotide exchange factor (RhoGEF) important in heart development and pro-fibrotic signaling in cardiomyocytes. Heterotrimeric G proteins of the G12/13 subfamily, comprising G?12 and G?13, are well characterized as stimulating a specialized group of RhoGEFs through interaction with their RGS-homology (RH) domain. Despite lacking an RH domain, AKAP-Lbc is bound by G?12 through an unknown mechanism to activate Rho signaling. We identified a G?12-binding region near the C-terminus of AKAP-Lbc, closely homologous to a region of p114RhoGEF that we also discovered to interact with G?12. This binding mechanism is distinct from the well-studied interface between RH-RhoGEFs and G12/13 ? subunits, as demonstrated by G?12 mutants selectively impaired in binding either this AKAP-Lbc/p114RhoGEF region or RH-RhoGEFs. AKAP-Lbc and p114RhoGEF showed high specificity for binding G?12 in comparison to G?13, and experiments using chimeric G12/13 ? subunits mapped determinants of this selectivity to the N-terminal region of G?12. In cultured cells expressing constitutively GDP-bound G?12 or G?13, the G?12 construct was more potent in exerting a dominant-negative effect on serum-mediated signaling to p114RhoGEF, demonstrating coupling of these signaling proteins in a cellular pathway. In addition, charge-reversal of conserved residues in AKAP-Lbc and p114RhoGEF disrupted G?12 binding for both proteins, suggesting they harbor a common structural mechanism for interaction with this ? subunit. Our results provide the first evidence of p114RhoGEF as a G?12 signaling effector, and define a novel region conserved between AKAP-Lbc and p114RhoGEF that allows G?12 signaling input to these non-RH RhoGEFs.

SUBMITTER: Martin JW 

PROVIDER: S-EPMC5345129 | biostudies-literature | 2016 Sep

REPOSITORIES: biostudies-literature