The gamma subunit of the Na,K-ATPase induces cation channel activity

The gamma subunit of the Na,K-ATPase is a hydrophobic protein of approximately 10 kDa. The gamma subunit was expressed in Sf-9 insect cells and Xenopus oocytes to ascertain its role in Na,K-ATPase function. Immunoblotting has shown that the gamma subunit is expressed in Sf-9 cells infected with recombinant baculovirus containing the cDNA for the human gamma subunit. Confocal microscopy demonstrates that the gamma subunit fan be delivered to the plasma membrane of Sf-9 cells independently of the other Na,K-ATPase subunits and that gamma colocalizes with alpha 1 when these proteins are coexpressed. When Sf-9 cells were coinfected with alpha 1 and gamma, antibodies to the gamma subunit were able to coimmunoprecipitate the alpha 1 subunit, suggesting that gamma is able to associate with alpha 1. The gamma subunit is a member of a family of single-pass transmembrane proteins that induces ion fluxes in Xenopus oocytes. Evidence that the gamma subunit is a functional component was supported by experiments showing gamma-induced cation channel activity when expressed in oocytes and increases in Na+ and K+ uptake when expressed in Sf-9 cells.