Identification of an acid-activated Cl(-) channel from human skeletal muscles.
ClC-4 gene was isolated as a putative Cl(-) channel. Due to a lack of functional expression of ClC-4, its physiological role remains unknown. We isolated a human ClC-4 clone (hClC-4sk) from human skeletal muscles and stably transfected it to Chinese hamster ovary cells. Whole cell patch-clamp studies showed that the hClC-4sk channel was activated by external acidic pH and inhibited by DIDS. It passed a strong outward Cl(-) current with a permeability sequence of I(-) > Cl(-) > F(-). The hClC-4sk has consensus sites for phosphorylation by protein kinase A (PKA); however, stimulation of PKA had no effect on the currents. hClC-4sk mRNA was expressed in excitable tissues, such as heart, brain, and skeletal muscle. These functional characteristics of hClC-4sk provide a clue to its physiological role in excitable cells.
Kawasaki
M
M
Second Department of Internal Medicine, Tokyo Medical and Dental University, Tokyo 113-8519, Japan.
Fukuma
T
T
Yamauchi
K
K
Sakamoto
H
H
Marumo
F
F
Sasaki
S
S
D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid / Q000494:pharmacology; D000143:Acids / Q000494:pharmacology*; D000595:Amino Acid Sequence; D000818:Animals; D016466:CHO Cells; D018118:Chloride Channels / Q000235:genetics* / Q000378:metabolism; D002712:Chlorides / Q000378:metabolism; D003001:Cloning, Molecular; D005576:Colforsin / Q000494:pharmacology; D006224:Cricetinae; D018076:DNA, Complementary / Q000302:isolation & purification; D005110:Extracellular Space / Q000378:metabolism; D015870:Gene Expression / Q000502:physiology; D006801:Humans; D006863:Hydrogen-Ion Concentration; D015640:Ion Channel Gating / Q000187:drug effects*; D008647:Mesocricetus; D008969:Molecular Sequence Data; D018482:Muscle, Skeletal / Q000737:chemistry* / Q000502:physiology; D018408:Patch-Clamp Techniques; D014162:Transfection
D000143:Acids; C484312:CLCN4 protein, human; D018118:Chloride Channels; D002712:Chlorides; D018076:DNA, Complementary; D005576:Colforsin; D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid