MOLECULAR-CLONING OF THE HUMAN VOLUME-SENSITIVE CHLORIDE CONDUCTANCE REGULATORY PROTEIN, PICLN, FROM OCULAR CILIARY EPITHELIUM

Chloride channels in the ocular ciliary epithelium are believed to play a key role in aqueous humor formation. We isolated a cDNA clone from a lambda Uni-ZAP cDNA library of human nonpigmented ciliary epithelial (NPE) cells encoding the swelling-induced chloride channel/channel regulator PICln The human clone contains an open reading frame of 237 amino acids (M(r) 26,293). The deduced human amino-acid sequence shows 90.2% and 92.7% identity with counterparts isolated from rat kidney and the canine kidney epithelial cell line MDCK. Human NPE cell lines exhibited significant levels of pI(Cln) transcripts. Complementary perforated-patch, whole-cell patch clamping demonstrated that swelling activates Cl- channels of the NPE cells, as suggested by ruptured-patch measurements. The results document the molecular isolation and identification of a human cDNA clone of a Cl- conductance regulator from ocular cells displaying volume-activated Cl(-)channels.