Calmodulin proteins are vital for both the assembly and regulation of auditory KCNQ channels. Although there are many informative high resolution structures of calmodulin bound to peptide fragments derived from ion channels, the location of calmodulin on functioning channels and the calcium-induced structural changes responsible for physiological function have remained elusive for all ion channels. This proposal outlines an innovative new approach that detects KCNQ-bound calmodulin and its distance from the ion conduction pathway. Using these experimentally determined distance restraints and the many high resolution structures of potassium channels and calmodulin bound to peptides, we will generate quaternary structures of the differently calcified KCNQ4- and KCNQ1/KCNE1-calmodulin complexes. These quaternary structures combined with the proposed functional studies will provide unprecedented molecular insight into calcium-regulated potassium recycling in the ear.
KCNQ potassium (K+) channel-calmodulin complexes are essential for potassium recycling in the inner ear. Mutations that disrupt the KCNQ-calmodulin interaction or reduce calcium-regulated potassium fluxes cause two auditory diseases: Jervell and Lange-Nielsen syndrome (JLNS) and non-syndromic, autosomal-dominant progressive high-frequency hearing loss (DFNA2). In this grant, we propose to build quaternary structures of KCNQ-calmodulin complexes from existing crystal structures using distance constraints generated from a novel intracellular, inverse-demand tethered blocker approach. By generating the differently calcified KCNQ-calmodulin complexes, we will provide new insight on how to use calmodulin to manipulate and control vestibular and cochlear K+ flux to treat JLNS and DFNA2 as well as Meni?re's Disease, endolymphatic hydrops, and chronic tinnitus.