Specificity and Structural Requirements of Phospholipase C-β Stimulation by Rho GTPases Versus G Protein βγ Dimers

• Published in: The Journal of biological chemistry Vol. 278; no. 5; p. 3006
• Main Authors: Daria Illenberger, Claudia Walliser, Bernd Nürnberg, Maria Diaz Lorente, Peter Gierschik
• Format: Journal Article
• Language: English
• Published: American Society for Biochemistry and Molecular Biology 31-01-2003
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M208282200

Phospholipase C-β 2 (PLCβ 2 ) is activated both by heterotrimeric G protein α- and βγ- subunits and by Rho GTPases. In this study, activated Rho GTPases
are shown to stimulate PLCβ isozymes with the rank order of PLCβ 2 > PLCβ 3 ≥ PLCβ 1 . The sensitivity of PLCβ isozymes to Rho GTPases was clearly different from that observed for G protein βγ dimers, which
decreased in the following order: PLCβ 3 > PLCβ 2 > PLCβ 1 for β 1 γ 1/2 and PLCβ 2 > PLCβ 1 >>> PLCβ 3 for β 5 γ 2 . Rac1 and Rac2 were found to be more potent and efficacious activators of PLCβ 2 than was Cdc42Hs. The stimulation of PLCβ 2 by Rho GTPases and G protein βγ dimers was additive, suggesting that PLCβ 2 activation can be augmented by independent regulation of the enzyme by the two stimuli. Using chimeric PLCβ 1 -PLCβ 2 enzymes, βγ dimers, and Rho GTPases are shown to require different regions of PLCβ 2 to mediate efficient stimulation of the enzyme. Although the catalytic subdomains X and Y of PLCβ 2 were sufficient for efficient stimulation by βγ, the presence of the putative pleckstrin homology domain of PLCβ 2 was absolutely required for the stimulation of the enzyme by Rho GTPases. Taken together, these results identify Rho GTPases
as novel PLCβ regulators, which mediate PLCβ isozyme-specific stimulation and are potentially involved in coordinating the
activation of PLCβ 2 by extracellular mediators in intact cells.