We used primary mouse corneal epithelial cells (pMCE) to examine the role of Kcnj10 in determining membrane K(+) conductance and cell membrane potential and in regulating EGF/TGFA release. Western blot, immunostaining, and RT-PCR detected the expression of Kcnj10 in mouse cornea. The single channel recording identified the 20-pS inwardly rectifying K(+) channels in pMCE of WT mice, but these channels were absent in Kcnj10(-/-). Moreover, the whole cell recording demonstrates that deletion of Kcnj10 largely abolished the inward K(+) currents and depolarized the cell membrane K(+) reversal potential (an index of the cell membrane potential). This suggests that Kcnj10 is a main contributor to the cell K(+) conductance and it is pivotal in generating membrane potential in cornea. Furthermore, to test the hypothesis that Kcnj10 expression plays a key role in the stimulation of growth factors release, we employed an immortalized human corneal epithelial cell line (HCE) transfected with siRNA-Kcnj10 or siRNA-control. Levels of TGFA and EGF secreted in the medium were measured by ELISA. Coimmunoprecipitation, biotinylation, and pull-down assay were used to examine the expression of EGFR and the GTP bound form of Rac1 (active Rac1). Downregulation of Kcnj10 activated Rac1 and enhanced EGF/TGFA release, which further contributed to the upregulation of EGFR phosphorylation and surface expression. We conclude that Kcnj10 is a main K(+) channel expressed in corneal epithelial cells and the inhibition of Kcnj10 resulted in depolarization, which in turn induced an EGF-like effect.
Keywords: EGFR signaling; Kir4.1; Rac1; corneal epithelial cells membrane potential.
Copyright © 2014 the American Physiological Society.