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John L Ubels, Mark P Schotanus, Peter M. Boersma, Loren D Haarsma; Expression of K+ Channels by Human Corneal Limbal Epithelial Cells. Invest. Ophthalmol. Vis. Sci. 2017;58(8):2629.
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We have previously reported that UVB-induced K+ currents in human corneal limbal epithelial (HCLE) cells are partially blocked (50-60%) by the Kv3.4 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 Kv3.4. The goal of this study was to identify K+ channels in HCLE cells and determine whether these channels are activated by UVB.
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 CT 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.
PCR gave evidence for expression of the genes for Kv1.2, Kv2.1, Kv2.2, Kv4.2, Kv11.1, Kv12.2, MaxiK and K2p1.1 channels. Immunofluorescence confirmed the presence of Kv2.1, Kv2.2, Kv3.4, Kv4.2, Kv11.1, MaxiK and K2p1.1 channels, while relatively weak signals were detected for Kv1.2 and Kv12.2. Heteropodatoxin-2, a Kv4.2 channel blocker, ergtoxin-1, a Kv11.1 channel blocker and iberiotoxin, which blocks MaxiK channels, had no effect on UVB-induced K+ currents.
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 Kv4.2, Kv11.1 and MaxiK channels on UVB-induced currents suggests that Kv3.4 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.
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