Distribution of ClC-2 chloride channel in rat and human epithelial tissues

Abstract

The ubiquitous ClC-2 Cl(-) channel is thought to contribute to epithelial Cl(-) secretion, but the distribution of the ClC-2 protein in human epithelia has not been investigated. We have studied the distribution of ClC-2 in adult human and rat intestine and airways by immunoblotting and confocal microscopy. In the rat, ClC-2 was present in the lateral membranes of villus enterocytes and was predominant at the basolateral membranes of luminal colon enterocytes. The expression pattern of ClC-2 in the human intestine differed significantly, because ClC-2 was mainly detected in a supranuclear compartment of colon cells. We found significant expression of ClC-2 at the apex of ciliated cells in both rat and human airways. These results show that the distribution of ClC-2 in airways is consistent with participation of ClC-2 channels in Cl(-) secretion and indicate that extrapolation of results from studies of ClC-2 function in rat intestine to human intestine is not straightforward.

Basolateral localization of native ClC-2 chloride channels in absorptive intestinal epithelial cells and basolateral sorting encoded by a CBS-2 domain di-leucine motif

“…An apical localization and function in fluid secretion is also postulated for ClC-2 in lung epithelium (Blaisdell et al, 2000). In contrast with these results, we and others have shown ClC-2 transcript in surface epithelium of guinea pig distal colon, identified a basolateral membrane localization of ClC-2 in surface epithelium and demonstrated a functional Cl -conductance with rectification and selectivity properties consistent with this subcellular distribution of ClC-2 (Catalán et al, 2002;Lipecka et al, 2002;Catalán et al, 2004). ClC-2 knockout mouse models present blindness and male infertility and, it has been argued, transepithelial transport defects could be responsible for these alterations (Bösl et al, 2001;Nehrke et al, 2002).…”

“…In the last two studies ClC-2 was co-localized with the tight junctions, where it was speculated to mediate Cl -efflux into the lumen. More recent experiments, however, report expression of ClC-2 at the basolateral membranes of surface colonic and small intestinal cells (Lipecka et al, 2002; Catalán -channel based on a high resolution X-ray diffraction study of a ClC from Salmonella typhimurium (Dutzler et al, 2003). The extracellular side is up.…”

“…In particular, CFTR, is solely expressed in the crypt epithelium (Trezise et al, 1992). Therefore, if ClC-2 is expressed in villi of small intestine and surface epithelium in the colon (Catalán et al, 2002;Lipecka et al, 2002;Catalán et al, 2004), and if involved in transepithelial transport, it would appear that it should participate in an absorptive rather than a secretory process.…”

Additional Disruption of the ClC-2 Cl- Channel Does Not Exacerbate the Cystic Fibrosis Phenotype of Cystic Fibrosis Transmembrane Conductance Regulator Mouse Models

“…Furthermore, several studies suggested that ClC-2 may be present in apical membranes of lung (18) and intestinal (19,33) epithelia, although others obtained conflicting results (34,35). Finally, the testicular and retinal degeneration observed in Clcn2 Ϫ/Ϫ mice was suggested to result from a defect in transepithelial transport across the Sertoli cell and retinal pigment epithelium, respectively (24).…”

An unexpected effect of TNF-α on F508del-CFTR maturation and function

“…Sample preparation protocols are described in detail elsewhere 12,13 . Briefly, cells were washed on ice twice with phosphate-buffered saline (PBS) solution containing 0.1mM CaCl 2 and 1mM MgCl 2 .…”