Regulation of Kv2.1 biogenesis and gating by candidate disease-linked Kv6.1 variants

Silent voltage-gated potassium channel subunits are enigmatic ion channels in the Kv5, Kv6, Kv8, and Kv9 families, which do not generate functional homomers, but instead assemble and modify the function of Kv2 family channels. While these biophysical consequences have been recognized, knowledge on physiological roles and pathologies associated with silent voltage-gated potassium channel subunits is not well developed. In this study, we investigated the functional effects of two Kv6.1 variants identified in either a pediatric patient (Kv6.1[L284P]), or a calf (Kv6.1[W416C]), which exhibited anatomical abnormalities. Kv2.1 current was reduced significantly when coexpressed with either Kv6.1 or Kv6.1[L284P], and even more dramatically with Kv6.1[W416C], which led to nearly complete suppression of Kv2.1 current. These mutants also attenuated Kv6.1-mediated effects on inactivation of Kv2.1. Interestingly, protein expression levels of Kv6.1 variants are not significantly affected when subunits are expressed alone. However, coexpression with Kv2.1 decreases expression of both Kv2.1 and Kv6.1 (and variants), and this effect is particularly powerful for Kv6.1[W416C]. Additionally, we report that Kv2.1 promotes phosphorylation of Kv6.1, but this is largely absent in the Kv6.1[W416C] mutant. Overall, effects of Kv6.1[W416C] are prominent, while Kv6.1[L284P]-mediated effects are much weaker and often difficult to distinguish from WT Kv6.1, and a direct causal link to anatomical abnormalities will require further investigation. Our findings highlight that Kv6.1 and variants influence expression and gating properties of Kv2.1, and also that coassembly with Kv2.1 leads to previously unrecognized posttranslational modifications of Kv6.1.