Stimulation of phospholipase C-beta2 by the Rho GTPases Cdc42Hs and Rac1.

Neutrophils contain a soluble guanine-nucleotidebinding protein, made up of two components with molecular masses of 23 and 26 kDa, that mediates stimulation of phospholipase C-beta2 (PLCbeta2). We have identified the two components of the stimulatory heterodimer by amino acid sequencing as a Rho GTPase and the Rho guanine nucleotide dissociation inhibitor LyGDI. Using recombinant Rho GTPases and LyGDI, we demonstrate that PLCbeta2 is stimulated by guanosine 5'-O-(3-thiotriphosphate) (GTP[S])-activated Cdc42HsxLyGDI, but not by RhoAxLyGDI.

Characterization and purification from bovine neutrophils of a soluble guanine-nucleotide-binding protein that mediates isozyme-specific stimulation of phospholipase C beta2.

Members of the beta isozyme subfamily of phosphatidylinositol-specific phospholipase C (PLC) are stimulated by alpha subunits and betagamma dimers of heterotrimeric guanine-nucleotide-binding proteins (G proteins). Myeloid differentiated human HL-60 granulocytes and bovine neutrophils contain a soluble phospholipase C, which is stimulated by the metabolically stable GTP analogue guanosine (5'-->O)-3-thiotriphosphate (GTP[S]). To identify the component(s) involved in mediating this stimulation, the relevant polypeptide(s) was resolved from endogenous phospholipase C and purified from bovine neutrophil cytosol by measuring its ability to confer GTP[S] stimulation to exogenous recombinant PLCbeta2.