ClC-2 contributes to native chloride secretion by a human intestinal cell line, Caco-2.
It has been previously determined that ClC-2, a member of the ClC chloride channel superfamily, is expressed in certain epithelial tissues. These findings fueled speculation that ClC-2 can compensate for impaired chloride transport in epithelial tissues affected by cystic fibrosis and lacking the cystic fibrosis transmembrane conductance regulator. However, direct evidence linking ClC-2 channel expression to epithelial chloride secretion was lacking. In the present studies, we show that ClC-2 transcripts and protein are present endogenously in the Caco-2 cell line, a cell line that models the human small intestine. Using an antisense strategy we show that ClC-2 contributes to native chloride currents in Caco-2 cells measured by patch clamp electrophysiology. Antisense ClC-2-transfected monolayers of Caco-2 cells exhibited less chloride secretion (monitored as iodide efflux) than did mock transfected monolayers, providing the first direct molecular evidence that ClC-2 can contribute to chloride secretion by the human intestinal epithelium. Further, examination of ClC-2 localization by confocal microscopy revealed that ClC-2 contributes to secretion from a unique location in this epithelium, from the apical aspect of the tight junction complex. Hence, these studies provide the necessary rationale for considering ClC-2 as a possible therapeutic target for diseases affecting intestinal chloride secretion such as cystic fibrosis.
Mohammad-Panah
R
R
Programme in Cell Biology and Genetics at the Hospital for Sick Children and the Departments of Physiology and Molecular Genetics at the University of Toronto, Toronto, M5G 1X8 Ontario, Canada.
Gyomorey
K
K
Rommens
J
J
Choudhury
M
M
Li
C
C
Wang
Y
Y
Bear
C E
CE
D018938:Caco-2 Cells; D002462:Cell Membrane / Q000737:chemistry; D016764:Cell Polarity; D018118:Chloride Channels / Q000032:analysis / Q000235:genetics / Q000502:physiology*; D002712:Chlorides / Q000378:metabolism*; D006801:Humans; D018408:Patch-Clamp Techniques; D019108:Tight Junctions / Q000502:physiology
D018118:Chloride Channels; D002712:Chlorides