CD63 interacts with the carboxy terminus of the colonic H+-K+-ATPase to increase plasma membrane localization and 86Rb+ uptake.

The carboxy terminus (CT) of the colonic H⁺-K⁺-ATPase is required for stable assembly with the β-subunit, translocation to the plasma membrane, and efficient function of the transporter. To identify protein-protein inter- actions involved in the localization and function of HKα₂, we selected 84 amino acids in the CT of the α-subunit of mouse colonic H⁺-K⁺- ATPase (CT-HKα₂) as the bait in a yeast two-hybrid screen of a mouse kidney cDNA library. The longest identified clone was CD63. To characterize the interaction of CT-HKα₂ with CD63, recombinant CT-HKα₂ and CD63 were synthesized in vitro and incubated, and complexes were immunoprecipitated. CT-HKα₂ protein (but not CT-HKα₁) coprecipitated with CD63, confirming stable assembly of HKα₂ with CD63. In HEK-293 transfected with HKα₂ plus β₁-Na⁺-K⁺-ATPase, suppression of CD63 by RNA interference increased cell surface expression of HKα₂/NKα₁ and ⁸⁶Rb⁺ uptake. These studies demonstrate that CD63 participates in the regulation of the abundance of the HKα₂-NKβ₁ complex in the cell membrane. [ABSTRACT FROM AUTHOR]