Protein kinase c-dependent phosphorylation of the na+,k+-atpase
[alpha]-subunit in rat kidney cortical tubules.
Carranza, Maria Luisa, Eric F[acute]eraille, and Herv[acute]e Favre.
Division de N[acute]ephrologie, H[circumflex]opital Cantonal
Universitaire, Rue Micheli du Crest, 24, CH-1211 Gen[grave]eve 14,
Switzerland
APStracts 3:0011C, 1996.
We have previously shown that in oxygenated rat kidney proximal
convoluted tubules (PCT), activation of protein kinase C (PKC) by
phorbol 12,13-dibutyrate (PDBu) directly stimulates Na+,K+-ATPase
activity. PKC modulation of Na+,K+-ATPase activity by phosphorylation
of its [alpha]-subunit was the postulated mechanism. The present
study was therefore designed to investigate the relationship between
PKC-mediated phosphorylation of the catalytic [alpha]-subunit and the
cation transport activity of the Na+,K+-ATPase. In a suspension of
rat kidney cortical tubules, activation of PKC by 10-7 M PDBu
increased the level of phosphorylation of the Na+,K+-ATPase [alpha]
-subunit and stimulated the ouabain-sensitive 86Rb uptake by 47 and 42
%, respectively. Time courses and dose-dependencies of the PDBu
-induced increase in Na+,K+-ATPase activity and phosphorylation were
strongly linearly correlated. The effects of PDBu on phosphorylation
and activity of Na+,K+-ATPase were prevented by GF109203X, a specific
PKC inhibitor, whereas H89, a specific PKA inhibitor, was
ineffective. These results demonstrate that PKC activation induces
phosphorylation of the catalytic [alpha]-subunit of Na+,K+-ATPase
which may participate to the stimulation of its cation transport
activity in the rat PCT.
Received 6 November 1995; accepted in final form 21 December
1995.
APS Manuscript Number C667-5.
Article publication pending Am. J. Physiol. (Cell Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 22 January 96