The Na+-K+-ATPase is understood to function as a hetero-oligomer of α- and β-subunits, but a third subunit, γ, has been proposed to influence the enzyme’s catalytic function. Recently, two variants of the γ-subunit have been described in kidney, raising the possibility of multiple γ-subunits with diverse functions. We now report the cloning and sequencing of the mouse γ-subunit gene ( Fxyd2). Analysis of the structure of the gene shows that it encodes three mRNAs that have distinct NH2-terminal (extracellular) encoding sequences but common transmembrane and COOH-terminal-encoding sequences resulting from differential splicing and, probably, alternate promoter usage. The three mRNAs have tissue-specific expression patterns. The existence of three different extracellular domains of the γ-variants and how they may interact with the sodium pump to alter its cation transport properties must now be taken into account for future understanding of the modulation of the Na+-K+-ATPase by its γ-subunit.
Alternate promoter usage generates two subpopulations of the neuronal RhoGEF Kalirin-7
