α1T can support NA',K'-atpase NA pump functions in expression systems

We have isolated a truncated form of the α1 subunit of the Na pump (α1T) which lacks ∼30% of the carboxy terminus (MW-66kD). Specific membrane association characteristics of α1T appears to vary between different tissues. We have used two expression systems to determine if α1T can support Na⁺,K⁺-ATPase and NaK pump functions. When co-expressed in Sf-9 cells with the proper β subunit, α1T complexes with the β subunit, localizes to the membrane and supports Na⁺,K⁺-ATPase activity. We have co-expressed rat α1T and β1 in HeLa cells, taking advantage of the rat α1T subunit's resistance to ouabain. Successful transfection was monitored by Northern and Western blots. The transfected cells grew successfully in 10^-7 M ouabain, a concentration which kills control cells. The sensitivity of ⁸⁶Rb uptake to ouabain was also significantly decreased in the α1T transfected cells. These data suggest that despite lacking 30% of the COOH terminus of the protein, α1T can support Na pump function.