Purpose of review
Na,K-ATPase is an oligomeric protein composed of α subunits, β subunits and FXYD proteins. The catalytic α subunit hydrolyzes ATP and transports the cations. Increasing experimental evidence suggest that β subunits and FXYD proteins essentially contribute to the variable physiological needs of Na,K-ATPase function in different tissues.
Beta subunits have a crucial role in the structural and functional maturation of Na,K-ATPase and modulate its transport properties. The chaperone function of the β subunit is essential, for example, in the formation of tight junctions and cell polarity. Recent studies suggest that β subunits also have inherent functions, which are independent of Na,K-ATPase activity and which may be involved in cell–cell adhesiveness and in suppression of cell motility. As for FXYD proteins, they modulate Na,K-ATPase activity in a tissue-specific way, in some cases in close cooperation with posttranslational modifications such as phosphorylation.
A better understanding of the multiple functional roles of the accessory subunits of Na,K-ATPase is crucial to appraise their influence on physiological processes and their implication in pathophysiological states.