Adducin point mutations are associated with genetic hypertension in Milan hypertensive strain (MHS) rats and in humans. In transfected cells, adducin affects actin cytoskeleton organization and increases the Na+-K+- pump rate. The present study has investigated whether rat and human adducin polymorphisms differently modulate rat renal Na+-K+ATPase in vitro. We report the following. 1) Both rat and human adducins stimulate Na+-K+- ATPase activity, with apparent affinity in tens of nanomolar concentrations. 2) MHS and Milan normotensive strain (MNS) adducins raise the apparent ATP affinity for Na+-K+-ATPase. 3) The mechanism of action of adducin appears to involve a selective acceleration of the rate of the conformational change E2 (K)- E1 (Na) or E2(K). ATP → E1Na·ATP. 4) Apparent affinities for mutant rat and human adducins are significantly higher than those for wild types. 5) Recombinant human α- and β-adducins stimulate Na+-K+-ATPase activity, as do the COOH-terminal tails, and the mutant proteins display higher affinities than the wild types. 6) The cytoskeletal protein ankyrin, which is known to bind to Na+-K+-ATPase, also stimulates enzyme activity, whereas BSA is without effect; the effects of adducin and ankyrin when acting together are not additive. 7) Pig kidney medulla microsomes appear to contain endogenous adducin; in contrast with purified pig kidney Na+-K+ATPase, which does not contain adducin, added adducin stimulates the Na+-K+-ATPase activity of microsomes only about one-half as much as that of purified Na+- K+-ATPase. Our findings strongly imply the existence of a direct and specific interaction between adducin and Na+-K+-ATPase in vitro and also suggest the possibility of such an interaction in intact renal membranes.
|Journal||American Journal of Physiology - Heart and Circulatory Physiology|
|Issue number||4 46-4|
|Publication status||Published - Oct 1999|
- Blood pressure
ASJC Scopus subject areas
- Physiology (medical)