Na,K-ATPase Abundance and Activity in HeLa Cells Transfected with Rat α Isoforms

Abstract

Since Na,K-ATPase is a heterodimer of an α catalytic subunit and a ß glycoprotein subunit assembled in a 1:1 stoichiometry, synthesis of αß heterodimers depends on the rate of synthesis of both α and ß subunits. We have previously demonstrated that ß is synthesized in excess over a subunits in two renal epithelial cell lines: LLC-PK₁ cells, where ß is synthesized in 3-fold excess over α (4), and MDCK cells where ß is synthesized in 5 fold excess (8). In both cell lines there is a component of degradation of nascent ß, presumably the excess unassembled subunits, during the first 30–60 min after synthesis. There is no detectable degradation of nascent α during this period, and subsequently there is coordinate degradation of α and ß, presumably αß heterodimers, with a t_1/2 of 10–12 hr (4).