Genetic dissection reveals unexpected influence of β subunits on KCNQ1 K⁺ channel polarized trafficking in vivo

Targeted deletion of the Kcne2 potassium channel β subunit gene ablates gastric acid secretion and predisposes to gastric neoplasia in mice. Here, we discovered that Kcne2 deletion basolaterally reroutes the Kcnq1 α subunit in vivo in parietal cells (PCs), in which the normally apical location of the Kcnq1-Kcne2 channel facilitates its essential role in gastric acid secretion. Quantitative RT-PCR and Western blotting revealed that Kcne2 deletion remodeled fundic Kcne3 (2.9±0.8-fold mRNA increase, n=10; 5.3±0.4-fold protein increase, n=7) but not Kcne1, 4, or 5, and resulted in basolateral Kcnq1-Kcne3 complex formation in Kcne2^-/- PCs. Concomitant targeted deletion of Kcne3 (creating Kcne2^-/-Kcne3 ^-/- mice) restored PC apical Kcnq1 localization without Kcne1, 4, or 5 remodeling (assessed by quantitative RT-PCR; n=5-10), indicating Kcne3 actively, basolaterally rerouted Kcnq1 in Kcne2^-/- PCs. Despite this, Kcne3 deletion exacerbated gastric hyperplasia in Kcne2^-/- mice, and both hypochlorhydria and hyperplasia in Kcne2^+/- mice, suggesting that Kcne3 up-regulation was beneficial in Kcne2-depleted PCs. The findings reveal, in vivo, Kcne-dependent α subunit polarized trafficking and the existence and consequences of potassium channel β subunit remodeling.