The proposed project is the study and characterization of CIC-Ka and ClC&#8209;Kb channels, plus CIC-Kb mutants associated with Banter's syndrome by an integrated approach utilizing electrophysiological, molecular biology and immunocytochemistry techniques. The uptake of NaCl by the thick ascending limb of the loop of Henle is crucial for the maintenance of body salt and fluid balance. The key role of ClC-Kb in this process is underscored by the observations that mutations in this gene are associated with the salt-wasting disorder Banter's syndrome. Prior attempts by other investigators to express recombinant CIC-Kb have been unsuccessful leading some to suggest the requirement for an, as yet unidentified, accessory subunit. We recently have made the remarkable discovery that co-expression of CIC-Kb with the previously recognized K plus channel subunit KCNE1 (minK) leads to functional Cl- channels in a heterologous mammalian cell system. We proposeto characterize ClC-Kb with members of this subunit family and use this approach to characterize Banter's syndrome mutations. These studies will expand our knowledge of the role CIC-K channels play on renal Cl- transport and help elucidate the role of ClC-Kb under normal and pathophysiological conditions. Our tactic of using an accessory protein to induce functional expression of ClC-Kb provides a novel approach for studying CIC channel function. Moreover, the observation that an accessory protein (i.e., KCNE1) modulates two different kinds of channels offers new outlooks for formulating questions to understand the complexity of membrane transport and its regulation. This award will enable the candidate to complete rigorous research training in a multidisciplinary environment. The sponsor has a strong and extensive record on expressing and characterizing ion channels, and on identifying and functionally characterizing disease-producing point mutations in human voltage-dependent channels and providing molecular and biophysical explanations for the observed phenotypes. The training program will include formal classes, lectures, seminars, and the supervision and guidance by a Career Development Committee consisting of senior faculty with broad expertise relevant to the research training. In summary, this award will greatly improve the applicant's chances of reaching his career goal of becoming a successful independent investigator by broadening his training and smoothing the transition from a mentored researcher to the independent investigation of CIC channels, a relatively new and exciting field with many questions still unanswered.