Activation of polyphosphoinositide phospholipase C by fluoride in WRK1 cell membranes

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Abstract
Partially purified plasma membranes prepared from myo-[3H]inositol-prelabeled WRK1 cells exhibit a phosphatidylinositol 4,5-bisphosphate (PIP2) phospholipase C activity sensitive to NaF. NaF increased the production of IP2 and IP3 in a time- and concentration-dependent manner. The maximal increase in IP2 and IP3 production rates represented 400 ± 18 and 360 ± 40% of the basal production rate, respectively. Half-maximum stimulation was reached with 2–4 mM NaF. The observed effect was specific for F−. Aluminium potentiated fluoride-induced IP3 and IP2, accumulation in a concentration-dependent manner. The effect of fluoride on the PIP2 phospholipase C from WRK1 cell membranes appears to be similar to the well-documented effect of F− on the well-characterized Ns. Ni and transducin GTP-binding proteins. This observation constitutes an additional argument to suggest that a GTP-binding protein is involved in the process of receptor-mediated activation of PIP2 phospholipase C.