Complement c5b-9 activates cytosolic phospholipase a2 in glomerular
epithelial cells.
Cybulsky, Andrey V., Juan Carlos Monge, Joan Papillon, and Alison J.
McTavish.
Department of Medicine, Royal Victoria Hospital, McGill University,
Montreal, Quebec, Canada H3A 1A1
APStracts 2:0113F, 1995.
In rat membranous nephropathy, complement C5b-9 induces glomerular
epithelial cell (GEC) injury and proteinuria, which in some models is
partially mediated by eicosanoids. By analogy, sublytic C5b-9 injures
plasma membranes and releases arachidonic acid (AA) and eicosanoids
in cultured rat GEC. In this study, we demonstrate that in GEC,
sublytic C5b-9 stably increased the activity of a high molecular mass
cytosolic phospholipase A2 (PLA2), which we identified as
"cPLA2". This increase was abolished with inhibitors of
protein kinase C. C5b-9 did not affect low molecular mass membrane
-associated, or secretory PLA2 activities. In GEC that stably
overexpress cPLA2 activity and protein (produced by transfection of
cPLA2 cDNA), immunoblot analysis showed that sublytic C5b-9 induced a
decreased mobility of cPLA2, consistent with cPLA2 phosphorylation.
Incubation of cPLA2-transfected GEC with sublytic C5b-9 significantly
increased production of free AA and prostaglandin E2, while in
control GEC, the C5b-9-induced changes in free AA and prostaglandin
E2 were small. Furthermore, both C5b-9-dependent sublytic
cytotoxicity and cytolysis were enhanced in GEC overexpressing cPLA2,
as compared to control cells. Thus, C5b-9 increased cPLA2 activity,
probably via phosphorylation involving a protein kinase C-dependent
pathway. Phospholipid hydrolysis by cPLA2 resulted in release of
substrate for eicosanoid synthesis and in enhancement of C5b-9
-dependent GEC injury. Both processes may facilitate glomerular damage
in membranous nephropathy.
Received 10 November 1994; accepted in final form 6 June 1995
APS Manuscript Number F0404-4.
Article publication pending Am. J. Physiol. (Renal Fluid Electrolyte
Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 18 July 1995.