Actin filaments stimulate the na+,k+-atpase.
Cantiello, Horacio F.
Renal Unit, Massachusetts General Hospital East, and Department of
Medicine, Harvard Medical School
APStracts 2:0070F, 1995.
In this report, the functional role of actin on Na+,K+-ATPase activity
was explored. The Na+ and K+-dependent, ouabain-sensitive ATP
hydrolysis mediated by rat kidney Na+,K+-ATPase increased by 74% in
the presence of previously unpolymerized actin (24 [mu]M), while
addition of polymerized actin was without effect. Addition of actin
was associated instead with an increase in the affinity of the
Na+,K+-ATPase for Na+ but not other enzymatic substrates. A maximal
stimulatory effect (296%) was observed either at a Na+,K+
-ATPase:actin ratio of 1:50,000, or at lower ratios (1:625) by
shifting from the E2 (K+-selective) to the E1 (Na+-selective)
conformation of the enzyme. Immunoblotting of actin to the purified
Na+,K+-ATPase suggested that this interaction may be linked to
binding of actin to the enzyme, which was further supported by
sequence analysis indicating putative actin-binding domains in the
[alpha] subunit of the enzyme. The interaction between actin and the
Na+,K+-ATPase may imply a novel functional role of the cytoskeleton
in the control of ion transport.
Received 28 December 1994; accepted in final form 24 April 1995.
APS Manuscript Number F460-4.
Article publication pending Am. J. Physiol. (Renal Fluid Electrolyte
Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 2 May 1995.