Association with {beta}-COP regulates the trafficking of the newly synthesized Na,K-ATPase.

ABSTRACT: Plasma membrane expression of the Na,K-ATPase requires assembly of its ?- and ?-subunits. Using a novel labeling technique to identify Na,K-ATPase partner proteins, we detected an interaction between the Na,K-ATPase ?-subunit and the coat protein, ?-COP, a component of the COP-I complex. When expressed in the absence of the Na,K-ATPase ?-subunit, the Na,K-ATPase ?-subunit interacts with ?-COP, is retained in the endoplasmic reticulum, and is targeted for degradation. In the presence of the Na,K-ATPase ?-subunit, the ?-subunit does not interact with ?-COP and traffics to the plasma membrane. Pulse-chase experiments demonstrate that in cells expressing both the Na,K-ATPase ?- and ?-subunits, newly synthesized ?-subunit associates with ?-COP immediately after its synthesis but that this interaction does not constitute an obligate intermediate in the assembly of the ?- and ?-subunits to form the pump holoenzyme. The interaction with ?-COP was reduced by mutating a dibasic motif at Lys(54) in the Na,K-ATPase ?-subunit. This mutant ?-subunit is not retained in the endoplasmic reticulum and reaches the plasma membrane, even in the absence of Na,K-ATPase ?-subunit expression. Although the Lys(54) ?-subunit reaches the cell surface without need for ?-subunit assembly, it is only functional as an ion-transporting ATPase in the presence of the ?-subunit.

SUBMITTER: Morton MJ 

PROVIDER: S-EPMC2962472 | biostudies-literature | 2010 Oct

REPOSITORIES: biostudies-literature