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The retina is a complex network of interconnected neurons necessary for processing visual information. In a recent study, it has been shown that potassium voltage-gated channel subfamily E member 2 (KCNE2), an evolutionary conserved ion-channel ancillary subunit is predominantly expressed in the dendritic tips of the rod ON-bipolar cells (rod-OBC) where a TRPM1-dependent signal transduction machinery is present and essential for processing scotopic vision. Mutations in various genes encoding for proteins involved in this signal transduction cascade lead to congenital stationary night blindness. The functional role of KCNE2 within this pathway remains elusive. In this thesis, we question if KCNE2 might modulate TRPM1 utilizing a combination of single-cell RNA sequencing dataset, immunocytochemistry, western blot, co-immunoprecipitation and cell viability assay. Transcriptomic analysis exhibited a robust correlation between TRPM1 and KCNE2 expression in rod-OBC at single-cell level. In heterologous expression systems, we observed that co-transfection of TRPM1 and KCNE2 reduced cell viability compared to single transfections and the deleterious effect of TRPM1 + KCNE2 co-expression seemed to be so pronounced that no simultaneous expression of both TRPM1 and KCNE2 proteins could be detected by immunocytochemistry in a single cell. In contrast, upon co-transfection of KCNE2 with a TRPM1 pore mutant (E1058Q), a subset of cells was observed to be expressing both proteins, with line profile analysis indicating their co-localization at the plasma membrane. Consistently, co-transfection with TRPM1E1058Q significantly enhanced cell viability, and yielded co-immunoprecipitation, indicating co-assembly into a single protein complex. Collectively, these findings provide first evidence of interaction between TRPM1 and KCNE2 and offer insights into the modulatory role of KCNE2 on TRPM1.
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