THE GUINEA-PIG COCHLEAR AE2 ANION-EXCHANGER - CDNA CLONING AND IN-SITU LOCALIZATION WITHIN THE COCHLEA

This study has characterized the repertoire of the anion exchanger (AE ) family members expressed within the guinea pig organ of Corti, the a uditory neuroepithelia. Both AE2 and AE3 cDNAs were present, but AE1 c DNA was not detected. The more abundant AE2 was sequenced and its expr ession characterized in the cochlea. The 3888 base pairs (bp) AE2 sequ ence, compiled from multiple clones, includes 150 bp of upstream non-c oding sequence and 3717 bp of open reading frame encoding a protein of 1238 amino acids. Immunoblot of cochlear homogenate revealed a single AE2-immunoreactive band of M-r 180 kDa. In situ hybridization and imm unohistochemical analysis localized AE2 expression to several tissues and cell types within the guinea pig inner ear, including superior hal f of the spiral ligament and within the interdental cells lining the s piral limbus. However, AE2 was not clearly detected in the outer hair cells (OHC) of the organ of Corti by either immunohistochemistry or in situ hybridization. The results of these studies imply a physiologic role of AE2 in the cochlear homeostasis, but do not support its role a s a potential 'motor protein' in mediating the in vitro-observed volta ge-gated, ATP-independent OHC motility. (C) 1998 Elsevier Science B.V. All rights reserved.