Grant: Travel Awards - Institute Community Support

Regulator of G protein signalling protein 2 (RGS2) attenuates G Protein Coupled Receptor (GPCR) signaling by promoting the hydrolysis of GTP in the activated Galpha subunit to GDP, thereby governing many physiological and pathophysiological signals. RGS2 has four initiation sites (at residues 1, 5, 16 and 33), resulting in the existence of four distinct N-terminal variants. Additionally there are naturally occurring mutations in this region at residues 5 (RGS2M5V) and 23 (RGS2 G23D), the latter of which is associated with borderline IQ, hirsutism, increased bone alkaline phosphatase, and decreased platelet Gs function. It is possible that differences in the N-terminal region of RGS2 may affect its activity at least in part by altering degradation and thereby influencing its cellular abundance. It has been shown that RGS2 homologues, RGS4 and RGS5, are rapidly degraded via amino acid triggers near their N termini. RGS2 degradation has never been closely investigated, but we hypothesize that it is degraded in a proteasomal fashion due to specific amino acids in the N-terminus. Changes in band density and electrophoretic mobility after MG132 (proteasome inhibitor) treatment suggest that a proteasomal degradation pathway is followed for RGS2. Our present findings also suggest that the M5V mutation leads to an increased cellular RGS2 level relative to that of the wild type protein. We have also mutated other amino acids at positions 1, 16, and 33, and found that these can also alter RGS2 protein turnover. Considering the importance of RGS2 in pathophysiological processes, altered degradation associated with mutant isoforms or initiation variants could have differential effects on GPCR signaling and thus contribute to such processes.