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.
The Cl- channel ClC-2 is expressed in transporting epithelia and has been proposed as an alternative route for Cl- efflux that might compensate for the malfunction of CFTR in cystic fibrosis. There is controversy concerning the cellular and membrane location of ClC-2, particularly in intestinal tissue. The aim of this paper is to resolve this controversy by immunolocalization studies using tissues from ClC-2 knockout animals as control, ascertaining the sorting of ClC-2 in model epithelial cells and exploring the possible molecular signals involved in ClC-2 targeting. ClC-2 was exclusively localized at the basolateral membranes of surface colonic cells or villus duodenal enterocytes. ClC-2 was sorted to the basolateral membranes in MDCK, Caco-2 and LLC-PK1-mu1B, but not in LLC-PK1-mu1A cells. Mutating a di-leucine motif (L812L813) to a di-alanine changed the basolateral targeting of ClC-2 to an apical location. The basolateral membrane localization of ClC-2 in absorptive cells of the duodenum and the colon is compatible with an absorptive function for this Cl- channel. Basolateral targeting information is contained in a di-leucine motif (L812L813) within CBS-2 domain at the C-terminus of ClC-2. It is speculated that ClC-2 also contains an apical sorting signal masked by L812L813. The proposal that CBS domains in ClC channels might behave as regulatory sites sensing intracellular signals opens an opportunity for pharmacological modulation of ClC-2 targeting.
Peña-Münzenmayer
Gaspar
G
Centro de Estudios Científicos (CECS), Av. Arturo Prat 514, Valdivia, Casilla 1469, Chile.
Catalán
Marcelo
M
Cornejo
Isabel
I
Figueroa
Carlos D
CD
Melvin
James E
JE
Niemeyer
María I
MI
Cid
L Pablo
LP
Sepúlveda
Francisco V
FV
D020816:Amino Acid Motifs; D000818:Animals; D000090007:CLC-2 Chloride Channels; D018938:Caco-2 Cells; D002478:Cells, Cultured; D018118:Chloride Channels / Q000096:biosynthesis* / Q000235:genetics / Q000378:metabolism; D004285:Dogs; D004386:Duodenum / Q000166:cytology / Q000378:metabolism; D020895:Enterocytes / Q000378:metabolism; D006801:Humans; D007408:Intestinal Absorption; D007413:Intestinal Mucosa / Q000166:cytology / Q000378:metabolism*; D007930:Leucine / Q000378:metabolism; D051379:Mice; D018345:Mice, Knockout; D017434:Protein Structure, Tertiary; D051381:Rats; D013552:Swine; D014018:Tissue Distribution; D014162:Transfection
D000090007:CLC-2 Chloride Channels; D018118:Chloride Channels; D007930:Leucine