Phosphorylation of S955 at the protein kinase A consensus promotes maturation of the α subunit of the colonic H+,K +-ATPase

Abstract

All the α subunits of the Na+,K+-ATPases and H+,K+-ATPases have a protein kinase A (PKA) consensus sequence near or in the ninth transmembrane domain. The role of this domain in influencing α subunit synthesis/degradation, plasma membrane localization, and 86Rb+ uptake has not been established for the α subunit of the colonic H+,K+-ATPase. This study examined the effect of mutating S955 (within the PKA consensus site of the α subunit of the colonic H+,K+-ATPase [HKα2]) to alanine (S955/A) or aspartic acid (S 955/D) on α subunit expression and function. The results demonstrate that a negatively charged amino acid at position 955 of HKα2 promotes higher expression levels of both whole-cell and plasma membrane-localized HKα2. Moreover, inhibition of PKA reduced expression of wild-type HKα2 and associated 86Rb+ uptake. Last, the activity of the HKα2 S955/A was rescued by treatment with 4-phenylbutyric acid, a compound that was shown previously to restore function to the cystic fibrosis transmembrane conductance regulator. Copyright © 2006 by the American Society of Nephrology.