IDENTIFICATION OF A PROTEIN THAT CONFERS CALCITONIN-GENE-RELATED PEPTIDE RESPONSIVENESS TO OOCYTES BY USING A CYSTIC-FIBROSIS TRANSMEMBRANECONDUCTANCE REGULATOR ASSAY

An expression-cloning strategy was used to isolate a cDNA that encodes a protein that confers calcitonin gene-related peptide (CGRP) respons iveness to Xenopus laevis oocytes, A guinea pig organ of Corti (the ma mmalian hearing organ) cDNA library was screened by using an assay bas ed on the cystic fibrosis transmembrane conductance regulator (CFTR), The CFTR is a chloride channel that is activated upon phosphorylation; this channel activity was used as a sensor for CGRP-induced activatio n of intracellular kinases, A cDNA library from guinea pig organ of Co rti was screened by using this oocyte-CFTR assay, A cDNA was identifie d that contained an open reading frame coding for a small hydrophilic protein that is presumed to be either a CGRP receptor or a component o f a CGRP receptor complex. This CGRP receptor component protein confer s CGRP-specific activation to the CFTR assay, as no activation was det ected upon application of calcitonin, amylin, neuropeptide Y, vasoacti ve intestinal peptide, or beta-endorphin, In situ hybridization demons trated that the CGRP receptor component protein is expressed in outer hair cells of the organ of Corti and is colocalized with CGRP-containi ng efferent nerve terminals.