Modulation of volume regulated anion current by I(Cln).
I(Cln), a cytosolic protein associated with a nucleotide-sensitive chloride current, may be involved in the regulation of a volume-regulated anion current (VRAC) associated with hypotonic cell swelling. We have determined the nucleic acid sequences of I(Cln) from human tsA201a, colonic (T84) and myeloma (RPMI 8826) cell lines. The amino acid sequences are highly homologous (>/=99%) to each other but less homologous to I(Cln) protein from other species. Using the whole-cell patch clamp technique, we examined the effect of I(Cln) protein expression levels on VRAC properties during a hyposmotic challenge. Overexpression of T84 or RPMI 8226-derived I(Cln) protein in tsA201a cells results in a more than 9-fold increase in the rate of VRAC activation over control values, while having no effect on VRAC inactivation properties. Underexpression of endogenous I(Cln) protein in tsA201a cells using antisense oligonucleotides results in a more than 180-fold decrease in VRAC activation rate as compared to control values. These results indicate that I(Cln) protein expression modulates VRAC activation but not inactivation.
Hubert
M D
MD
Department of Physiology and Biophysics, Finch University of Health Sciences, The Chicago Medical School, North Chicago, IL 60064-3095, USA.
Levitan
I
I
Hoffman
M M
MM
Zraggen
M
M
Hofreiter
M E
ME
Garber
S S
SS
D000595:Amino Acid Sequence; D000818:Animals; D000838:Anions; D001483:Base Sequence; D018118:Chloride Channels / Q000096:biosynthesis* / Q000235:genetics; D018076:DNA, Complementary; D004285:Dogs; D004594:Electrophysiology; D015870:Gene Expression; D006801:Humans; D007473:Ion Channels / Q000502:physiology*; D008969:Molecular Sequence Data; D051381:Rats; D017386:Sequence Homology, Amino Acid; D014407:Tumor Cells, Cultured
D000838:Anions; C410035:CLNS1A protein, human; D018118:Chloride Channels; C498729:Clns1a protein, rat; D018076:DNA, Complementary; D007473:Ion Channels