Sperm motility is dependent on a unique isoform of the Na,K-ATPase

Abstract

The Na,K-ATPase, a member of the P-type ATPases, is composed of two subunits, α and β, and is responsible for translocating Na+ out of the cell and K+ into the cell using the energy of hydrolysis of one molecule of ATP. The electrochemical gradient it generates is necessary for many cellular functions, including establishment of the plasma membrane potential and transport of sugars and ions in and out of the cell. Families of isoforms for both the α and β subunits have been identified, and specific functional roles for individual isoforms are just beginning to emerge. The α4 isoform is the most recently identified Na,K-ATPase α isoform, and its expression has been found only in testis. Here we show that expression of the α4 isoform in testis is localized to spermatozoa and that inhibition of this isoform alone eliminates sperm motility. These data describe for the first time a biological function for the α4 isoform of the Na,KATPase, revealing a critical role for this isoform in sperm motility.