These tools will no longer be maintained as of December 31, 2024. Archived website can be found here. PubMed4Hh GitHub repository can be found here. Contact NLM Customer Service if you have questions.


Pubmed for Handhelds

PUBMED FOR HANDHELDS

Search MEDLINE/PubMed

  • Title: Activation of phospholipase C isozymes by G protein beta gamma subunits.
    Author: Park D, Jhon DY, Lee CW, Lee KH, Rhee SG.
    Journal: J Biol Chem; 1993 Mar 05; 268(7):4573-6. PubMed ID: 8383116.
    Abstract:
    The beta gamma subunits of guanine nucleotide-binding proteins (G proteins) have been shown to activate unidentified phospholipase C (PLC) isozymes (Camps, M., Hou, C., Sidiropoulos, D., Stock, J. B., Jakobs, K. H., and Gierschik, P. (1992) Eur. J. Biochem. 206, 821-831; Blank, J. L., Brattain, K. A., and Exton, J. H. (1992) J. Biol. Chem. 267, 23069-23075). To identify these target PLC isozymes, we measured the effect of bovine brain G protein beta gamma subunits on PLC-beta 1, PLC-beta 2, PLC-beta 3, PLC-gamma 1, and PLC-delta 1 activity by reconstituting purified protein components with lipid vesicles containing [3H]phosphatidylinositol 4,5-bisphosphate (PtdIns 4,5-P2). A nearly saturating concentration of beta gamma produced 2.5-, 4-, 8.5-, and 2-fold increases in PLC-beta 1, PLC-beta 2, PLC-beta 3, and PLC-delta 1 activity, respectively, and no activation of PLC-gamma 1, in the presence of 0.2 microM free Ca2+. The beta gamma-dependent activation of the PLC-beta isozymes does not appear to be the result of increased affinity of the enzymes for Ca2+. The beta gamma-dependent PLC activation could be reversed by addition of the GDP-bound form of the alpha subunit of G(o). The alpha subunits of Gq class G proteins have been shown to activate PLC-beta isozymes in the order of PLC-beta 1 > or = PLC-beta 3 >> PLC-beta 2, which differs from the order of PLC-beta 3 > PLC-beta 2 > PLC-beta 1 for beta gamma-dependent activation. Furthermore, the half-maximal concentration of beta gamma (25 nM) required to activate PLC-beta 3 is much higher than that of Gq alpha subunits (0.6 nM) required to activate PLC-beta 1. These results suggest that the extracellular signals that induce the dissociation of G(o) or Gi, the heterotrimeric G proteins abundant in brain, should enhance the hydrolysis of PtdIns 4,5-P2 in brain primarily through activation of PLC-beta 3 (PLC-beta 2 is not detectable in brain). However, signals that activate the less abundant Gq class heterotrimers should result in the activation primarily of PLC-beta 1 and PLC-beta 3 by the corresponding alpha subunits.
    [Abstract] [Full Text] [Related] [New Search]