COMPARISON OF MESSENGER-RNA EXPRESSION OF 2 REGULATORS OF G-PROTEIN SIGNALING, RGS1 BL34/1R20 AND RGS2/G0S8, IN CULTURED HUMAN BLOOD MONONUCLEAR-CELLS/

RGS1 and RGS2 are members of a new class of regulators of G-protein si gnaling identified by their selective mRNA expression either in phorbo l ester (TPA)-stimulated human B lymphocytes (RGS1/1R20/BL34) or in bl ood mononuclear cells treated with the T-cell lectin concanavalin A (C onA) and cycloheximide (RGS2/G0S8), The RGS1 gene shows low basal mRNA expression in freshly purified blood mononuclear cells, which increas es upon incubation for a day, In contrast, RGS2 initially shows high b asal levels of mRNA expression, which subsequently decrease, Expressio n of both genes increases in response to ConA, with RGS2 mRNA levels i ncreasing briskly to a maximum between 0.5 and 1 hr and decreasing to baseline by 6 hr, whereas the RGSI mRNA increase is delayed reaching a maximum between 1 and 2 hr. PGS1 mRNA levels increase much more in re sponse to a protein kinase C activator (TPA), than to a calcium ionoph ore (ionomycin), whereas the opposite is true for RGS2, We suggest tha t ConA elevates RGS2 on the basis of its ability to increase intracell ular calcium, and that RGS2 may be involved in the regulation of intra cellular calcium. The distinction between RGS1 and RGS2 is further emp hasized by studies indicating that recombinant RGS2 does not bind in v itro to two members of the G(i) subfamily of G-protein alpha-subunits for which recombinant RGS1 has high affinity.