KCNQ and KCNE potassium channel subunit expression in bovine retinal pigment epithelium

•The expression of KCNQ and KCNE K+ channel subunits in native bovine RPE was investigated.•Transcripts for KCNQ1, Q4, and Q5 and KCNE1, E2, E3, and E4 were found to be present.•KCNQ5, KCNE1, and KCNE2 were detected in RPE plasma membrane proteins.•KCNE1 was localized in the RPE apical and basal membranes and in the neural retina.•KCNE1 β-subunits may contribute to KCNQ and other K+ channels in the RPE and retina.

Human, monkey, and bovine retinal pigment epithelial (RPE) cells exhibit an M-type K+ current, which in many other cell types is mediated by channels composed of KCNQ α-subunits and KCNE auxiliary subunits. Recently, we demonstrated the expression of KCNQ1, KCNQ4, and KCNQ5 in the monkey RPE. Here, we investigated the expression of KCNQ and KCNE subunits in native bovine RPE. RT-PCR analysis revealed the expression of KCNQ1, KCNQ4, and KCNQ5 transcripts in the RPE, but, in Western blot analysis of RPE plasma membranes, only KCNQ5 was detected. Among the five members of the KCNE gene family, transcripts for KCNE1, KCNE2, KCNE3, and KCNE4 were detected in bovine RPE, but only KCNE1 and KCNE2 proteins were detected. Immunohistochemistry of frozen bovine retinal sections revealed KCNE1 expression near the apical and basal membranes of the RPE, in cone outer segments, in the outer nuclear layer, and throughout the inner retina. The localization of KCNE1 in the RPE basal membrane, where KCNQ5 was previously found to be present, suggests that this β-subunit may contribute to M-type K+ channels in this membrane.