Brain Modulator of Na,K-ATPase

Abstract

The Na,K-ATPases (adenosine triphosphatases) are regulated by interactions with a family of membrane proteins known as FXYD proteins, so named because of a shared sequence motif. Béguin et al. characterized a new member of the family called FXYD7. Of the rat tissues sampled, FXYD was expressed only in brain and was present in both neurons and glial cells. Like other FXYD proteins, FXYD7 interacted with the Na,K-ATPase and could alter the function of that enzyme. Na,K-ATPases are dimers composed of combinations of four α and three β isoforms. FXYD7 appeared to interact only with α1-β1 isozymes. Studies in injected oocytes showed that unlike other FXYD proteins, such as CHIF (corticosteroid hormone-induced factor), FXYD7 did not alter activation of the Na,K-ATPase by Na+. Rather, FXYD7 decreased the apparent affinity of the Na,K-ATPase for K+. The authors suggest that such modulation of the affinity of the Na,K-ATPase for K+ might be important for response to high concentrations of K+ that occur after intense neuronal activity.P. Béguin, G. Crambert, F. Monnet-Tschudi, M. Uldry, J.-D. Horisberger, H. Garty, K. Geering, FXYD7 is a brain-specific regulator of Na,K-ATPaseα1-ß isozymes. EMBO J. 21, 3264-3273 (2002). [Abstract] [Full Text]