Expression of K⁺ Channels by Human Corneal Limbal Epithelial Cells

Abstract

Purpose : We have previously reported that UVB-induced K⁺ currents in human corneal limbal epithelial (HCLE) cells are partially blocked (50-60%) by the K_v3.4 blocker, BDS-1, and completely blocked by Ba²⁺ (Singleton et al. Exp Eye Res. 89:140, 2009; Glupker et al. Ocular Surf. 14:401, 2016). This suggests that HCLE cells express K⁺ channels in addition to K_v3.4. The goal of this study was to identify K⁺ channels in HCLE cells and determine whether these channels are activated by UVB.

Methods : HCLE cells were screened for K⁺ channel expression using a Human Neuronal Ion Channels RT² Profiler PCR Array (Qiagen). Expression of channels for which the C_T was < 33 on the PCR arrays was confirmed by immunofluorescence microscopy using appropriate antibodies. Activation of K⁺ currents was measured by whole-cell patch-clamp recording after exposure of cells to 80 mJ/cm² UVB. Specific blockers (if available) for channels detected by immunofluorescence were used to determine whether these channels were activated by UVB.

Results : PCR gave evidence for expression of the genes for K_v1.2, K_v2.1, K_v2.2, K_v4.2, K_v11.1, K_v12.2, MaxiK and K_2p1.1 channels. Immunofluorescence confirmed the presence of K_v2.1, K_v2.2, K_v3.4, K_v4.2, Kv11.1, MaxiK and K_2p1.1 channels, while relatively weak signals were detected for K_v1.2 and K_v12.2. Heteropodatoxin-2, a K_v4.2 channel blocker, ergtoxin-1, a K_v11.1 channel blocker and iberiotoxin, which blocks MaxiK channels, had no effect on UVB-induced K⁺ currents.

Conclusions : The data show that HCLE cells express a large number of K⁺ channels which may be involved in cell volume regulation, responses to environmental stimuli and regulation of intracellular signaling pathways. The lack of effect of blockers of K_v4.2, K_v11.1 and MaxiK channels on UVB-induced currents suggests that K_v3.4 channels strongly dominate the response of HCLE cells to UVB, although involvement of channels for which specific blockers are not available cannot be ruled out.

This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.