N-Terminal Modification of a G Protein gamma Subunit

Medical University Of South Carolina, Charleston SC

Investigators

Abstract

The precise, alpha, beta, and gamma subunits which constitute a give G- protein heterotrimer are crucial determinants of the signal which is transduced from an extracellular stimulus to downstream effectors within a cell. This laboratory has previously identified significant variation in post-translational processing events at the amino terminus of gamma subunits, suggesting that the amino terminus of these isoforms plays a crucial role in the regulation of G-protein signaling events. Specifically, we hypothesize that several gamma isoforms have altered stability within a cell as a direct result of the variation at the amino terminus. Using a combination of in vitro and cellular assays, we aim to evaluate the ability of N-terminal gamma2 targets substrates for ubiquitinated and degraded by the N-end rule pathway, a regulatory pathway which targets substrates for ubiquitin-dependent degradation of gamma2, and/or its associated subunits, will be explored by analysis of its effect upon known betagamma mediated responses. Finally, we propose to characterize upstream processing activities in particular, a proteolytic activity which is likely to be a requisite upstream event prior to the presentation of a destabilizing amino acid at the amino terminus of a subset of gamma isoforms. Such experiments evaluating the functional consequence of post-translational modification of gamma subunits have the potential to elucidate novel determinants in the regulation of G- protein subunit availability and the resulting heterotrimer activity.