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Interaction between CFTR and prestin (SLC26A5)
Authors:Kazuaki Homma  Charles T Anderson  Guo-Guang Du  MaryAnn Cheatham  Jing Zheng
Institution:a Department of Communication Sciences and Disorders, The Hugh Knowles Center, Northwestern University, Evanston, IL 60208, USA
b Department of Neurobiology and Physiology, Northwestern University, Evanston, IL 60208, USA
c Department of Otolaryngology, Feinberg School of Medicine, Northwestern University, 303 East Chicago Avenue, Chicago, IL 60611, USA
Abstract:Cystic fibrosis transmembrane conductance regulator (CFTR) is a cAMP-activated chloride channel that is present in a variety of epithelial cell types, and usually expressed in the luminal membrane. In contrast, prestin (SLC26A5) is a voltage-dependent motor protein, which is present in the basolateral membrane of cochlear outer hair cells (OHCs), and plays an important role in the frequency selectivity and sensitivity of mammalian hearing. By using in situ hybridization and immunofluorescence, we found that both mRNA and protein of CFTR are present in OHCs, and that CFTR localizes in both the apical and the lateral membranes. CFTR was not detected in the lateral membrane of inner hair cells (IHCs) or in that of OHCs derived from prestin-knockout mice, i.e., in instances where prestin is not expressed. These results suggest that prestin may interact physically with CFTR in the lateral membrane of OHCs. Immunoprecipitation experiments confirmed a prestin-CFTR interaction. Because chloride is important for prestin function and for the efferent-mediated inhibition of cochlear output, the prestin-directed localization of CFTR to the lateral membrane of OHCs has a potential physiological significance. Aside from its role as a chloride channel, CFTR is known as a regulator of multiple protein functions, including those of the solute carrier family 26 (SLC26). Because prestin is in the SLC26 family, several members of which interact with CFTR, we explored the potential modulatory relationship associated with a direct, physical interaction between prestin and CFTR. Electrophysiological experiments demonstrated that cAMP-activated CFTR is capable of enhancing voltage-dependent charge displacement, a signature of OHC motility, whereas prestin does not affect the chloride conductance of CFTR.
Keywords:CFTR  cystic fibrosis transmembrane conductance regulator  Fsk  forskolin  IBMX  3-isobutyl-1-methylxanthine  IHC  inner hair cell  NLC  nonlinear capacitance  OHC  outer hair cell  SLC26  solute carrier protein 26
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