Endothelin-1 induced mesangial cell contraction involves activation
of protein kinase c -[alpha], -[delta] and -[epsilon].
Dlugosz, John A., Snezana Munk, Xiaopeng Zhou, and Catharine I.
Whiteside.
MRC Group in Membrane Biology, University of Toronto, Toronto,
Ontario, Canada M5S 1A8
APStracts 5:0115F, 1998.
In endothlin-1 (ET-1)-stimulated mesangial cells, to identify the
independent roles of calcium and PKC causing contraction, the change
in planar surface area in response to ET-1, ionomycin (IONO), or
phorbol 12-myristate 13-acetate (PMA) were compared. ET-1, PMA and
IONO reduced planar area to 49 +/- 3%, 56 +/- 3% and 78 +/- 2% of
basal (mean +/- SE, n=40-50 cells), respectively. ET-1 or IONO
increased cytosolic calcium from 80 +/- 7 to 220 +/- 30 nM or 97 +/-
10 to 192 +/- 10 nM, respectively. The myosin light chain kinase
inhibitor, ML-7, blunted ET-1, but not PMA-stimulated contraction (82
+/- 3% and 48_+/- 6% of basal respectively). Cells pretreated with 10
uM chelerythrine for 1 h, or PMA for 24 h, failed to contract to
either ET-1 or PMA. To identify the specific PKC isoform response to
ET-1, cytosolic, membrane and particulate fractions of mesangial cell
lysates were immunoblotted with PKC isoform-specific polyclonal
antibodies. ET-1 increased membrane PKC-a, -d, -e to 173 +/- 30%, 162
+/- 26% and 166 +/- 11% of basal (p<0.05 vs basal), respectively,
and decreased PKC-[delta] and PKC-[epsilon] in the cytosol to 56 +/-
11% and 37 +/- 6% of basal, respectively (p<0.05). ET-1 increased
particulate PKC-[delta] and PKC-[epsilon] to 172 +/- 15% and 187 +/-
33% of basal (p<0.05) respectively. PKC-[alpha] in the cytosol and
particulate fractions was not altered by ET-1, but translocation to
the nucleus and cell periphery was observed by confocal
immunofluorescence imaging. IONO did not change PKC isoform
distribution. PKC-z was expressed but unaltered by ET-1. Therefore,
mesangial cell ET-1-stimulated contraction not only involves a
calcium-dependent pathway, but also includes the activation of one or
more PKC-a, -d and -[epsilon], but not PKC-z.
Received 19 February 1998; accepted in final form 18 June 1998.
APS Manuscript Number F38-8.
Article publication pending Am. J. Physiol. (Renal Physiology).
ISSN 1080-4757 Copyright 1998 The American Physiological Society.
Published in APStracts on 30 July 1998