1.A.2.1.8
The inward rectifier potassium channel 13, Kir 7.1, Kir1.4, or KCNJ13, of 360 aas and 2 TMSs. A splice variant expressed in mouse tissues shares organisational and functional properties with human leber amaurosis-causing mutations of this channel (Vera et al. 2019). In fact, mutations in KCNJ13 are associated with two retinal disorders; Leber congenital amaurosis (LCA) and snowflake vitreoretinal degeneration (SVD) (Toms et al. 2019). Pinacidil is a channel opener (Sun et al. 2019). It may play a role in the control of polyamine-mediated channel gating and in the blocking by intracellular magnesium. A Kir7.1 disease mutant T153I within the inner pore affects K⁺ conduction (Beverley et al. 2022). Kir7.1 exhibits small unitary conductance and low dependence on external potassium. Kir7.1 channels also show a phosphatidylinositol 4,5-bisphosphate (PIP(2)) dependence for opening (Hernandez et al. 2023). Retinopathy- associated Kir7.1 mutations map at the binding site for PIP(2), resulting in channel gating defects, leading to channelopathies such as snowflake vitreoretinal degeneration and Leber congenital amaurosis in blind patients. These properties may be due to its unusual structure (Hernandez et al. 2023).