J. Biol. Chem., Vol. 265, Issue 14, 7920-7926, May, 1990
Guanine nucleotide-dependent inhibition of phospholipase C in human endothelial cells
C Van Geet, H Deckmyn, J Kienast, C Wittevrongel and J Vermylen
Center for Thrombosis and Vascular Research, Katholieke Universiteit Leuven, Belgium.
Treatment of intact human umbilical vein endothelial cells with NaF results
in a dose-dependent biphasic response in both prostacyclin and inositol
phosphate production: the stimulation observed with 10-20 mM NaF decreases
with higher concentrations. High concentrations of NaF furthermore reduce
thrombin- or A23187-stimulated prostacyclin production. Direct assay of
phospholipase C activity in cell homogenates shows a similar biphasic
response to NaF, also after chelation of Ca2+; addition of AlCl3 shifts the
inhibition toward lower NaF concentrations. Guanosine
5'-O-(3-thiotriphosphate) (GTP gamma S) also causes a dose-dependent
biphasic response in inositol phosphate formation in permeabilized cells
and homogenates; a higher inhibitory concentration of GTP gamma S abolishes
the stimulation of inositol phosphate production by low NaF concentrations.
A high concentration of NaF furthermore inhibits the
non-G-protein-dependent activation of phospholipase C by deoxycholate. NaF
also induces a dose-dependent biphasic response in cyclic AMP formation in
intact cells, indicating that the inhibition of phospholipase C at higher
NaF concentrations does not result from a rise in cyclic AMP. The data are
compatible with the existence of a guanine nucleotide-dependent, cyclic
AMP- independent, phospholipase C-inhibitory pathway in endothelial cells.