Evidence for an interaction between adducin and Na + -K + -ATPase: relation to genetic hypertension

• Published in: American journal of physiology. Heart and circulatory physiology 1999-10, Vol.277 (4), p.H1338
• Main Authors: Ferrandi, Mara, Salardi, Sergio, Tripodi, Grazia, Barassi, Paolo, Rivera, Rodolfo, Manunta, Paolo, Goldshleger, Rivka, Ferrari, Patrizia, Bianchi, Giuseppe, Karlish, Steven J D
• Format: Article
• Language: English
• ISSN: 1522-1539
• DOI: 10.1152/ajpheart.1999.277.4.H1338

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 E (K) → E (Na) or E (K) ⋅ ATP → E Na ⋅ 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.