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 pla y a key role in aqueous humor formation. We isolated a cDNA clone from a lambda Uni-ZAP cDNA library of human nonpigmented ciliary epithelia l (NPE) cells encoding the swelling-induced chloride channel/channel r egulator PICln The human clone contains an open reading frame of 237 a mino acids (M(r) 26,293). The deduced human amino-acid sequence shows 90.2% and 92.7% identity with counterparts isolated from rat kidney an d the canine kidney epithelial cell line MDCK. Human NPE cell lines ex hibited significant levels of pI(Cln) transcripts. Complementary perfo rated-patch, whole-cell patch clamping demonstrated that swelling acti vates Cl- channels of the NPE cells, as suggested by ruptured-patch me asurements. The results document the molecular isolation and identific ation of a human cDNA clone of a Cl- conductance regulator from ocular cells displaying volume-activated Cl(-)channels.