Human ClC-3 is not the swelling-activated chloride channel involved in cell volume regulation.
Volume regulation is essential for normal cell function. A key component of the cells' response to volume changes is the activation of a channel, which elicits characteristic chloride currents (I(Cl, Swell)). The molecular identity of this channel has been controversial. Most recently, ClC-3, a protein highly homologous to the ClC-4 and ClC-5 channel proteins, has been proposed as being responsible for I(Cl, Swell). Subsequently, however, other reports have suggested that ClC-3 may generate chloride currents with characteristics clearly distinct from I(Cl, Swell). Significantly different tissue distributions for ClC-3 have also been reported, and it has been suggested that two isoforms of ClC-3 may be expressed with differing functions. In this study we generated a series of cell lines expressing variants of ClC-3 to rigorously address the question of whether or not ClC-3 is responsible for I(Cl, Swell). The data demonstrate that ClC-3 is not responsible for I(Cl, Swell) and has no role in regulatory volume decrease, furthermore, ClC-3 is not activated by intracellular calcium and fails to elicit chloride currents under any conditions tested. Expression of ClC-3 was shown to be relatively tissue-specific, with high levels in the central nervous system and kidney, and in contrast to previous reports, is essentially absent from heart. This distribution is also inconsistent with the previous proposed role in cell volume regulation.
Medical Research Council Clinical Sciences Centre, Imperial College School of Medicine, Hammersmith Hospital Campus, Du Cane Rd., London W12 0NN, United Kingdom.
K H
KH
Weylandt
M A
MA
Valverde
M
M
Nobles
S
S
Raguz
J S
JS
Amey
M
M
Diaz
C
C
Nastrucci
C F
CF
Higgins
A
A
Sardini
D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D000906:Antibodies; D000001:Calcimycin / Q000494:pharmacology; D002118:Calcium / Q000502:physiology; D002460:Cell Line; D002462:Cell Membrane / Q000502:physiology; D048429:Cell Size / Q000502:physiology*; D018118:Chloride Channels / Q000187:drug effects / Q000235:genetics / Q000502:physiology*; D000939:Epitopes / Q000737:chemistry; D049452:Green Fluorescent Proteins; D006706:Homeostasis; D006801:Humans; D007038:Hypotonic Solutions; D008164:Luminescent Proteins / Q000032:analysis; D018613:Microscopy, Confocal; D008969:Molecular Sequence Data; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D011994:Recombinant Proteins / Q000032:analysis / Q000187:drug effects / Q000378:metabolism; D017384:Sequence Deletion; D014162:Transfection
D000906:Antibodies; C097503:CLC-5 chloride channel; D018118:Chloride Channels; C115376:ClC-3 channel; D000939:Epitopes; D007038:Hypotonic Solutions; D008164:Luminescent Proteins; D011993:Recombinant Fusion Proteins; D011994:Recombinant Proteins; D049452:Green Fluorescent Proteins; D000001:Calcimycin; D002118:Calcium