Cytoplasmic ATP-sensing domains regulate gating of skeletal muscle ClC-1 chloride channels.
ClC proteins are a family of chloride channels and transporters that are found in a wide variety of prokaryotic and eukaryotic cell types. The mammalian voltage-gated chloride channel ClC-1 is important for controlling the electrical excitability of skeletal muscle. Reduced excitability of muscle cells during metabolic stress can protect cells from metabolic exhaustion and is thought to be a major factor in fatigue. Here we identify a novel mechanism linking excitability to metabolic state by showing that ClC-1 channels are modulated by ATP. The high concentration of ATP in resting muscle effectively inhibits ClC-1 activity by shifting the voltage gating to more positive potentials. ADP and AMP had similar effects to ATP, but IMP had no effect, indicating that the inhibition of ClC-1 would only be relieved under anaerobic conditions such as intense muscle activity or ischemia, when depleted ATP accumulates as IMP. The resulting increase in ClC-1 activity under these conditions would reduce muscle excitability, thus contributing to fatigue. We show further that the modulation by ATP is mediated by cystathionine beta-synthase-related domains in the cytoplasmic C terminus of ClC-1. This defines a function for these domains as gating-modulatory domains sensitive to intracellular ligands, such as nucleotides, a function that is likely to be conserved in other ClC proteins.
Bennetts
Brett
B
St. Vincent's Institute, Victoria, Australia.
Rychkov
Grigori Y
GY
Ng
Hooi-Ling
HL
Morton
Craig J
CJ
Stapleton
David
D
Parker
Michael W
MW
Cromer
Brett A
BA
D000244:Adenosine Diphosphate / Q000737:chemistry; D000249:Adenosine Monophosphate / Q000737:chemistry; D000255:Adenosine Triphosphate / Q000737:chemistry*; D000595:Amino Acid Sequence; D000818:Animals; D018118:Chloride Channels / Q000737:chemistry* / Q000378:metabolism; D003541:Cystathionine beta-Synthase / Q000737:chemistry; D003593:Cytoplasm / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D006801:Humans; D047468:Immunoprecipitation; D015640:Ion Channel Gating; D008024:Ligands; D008958:Models, Molecular; D008969:Molecular Sequence Data; D018482:Muscle, Skeletal / Q000378:metabolism*; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D017386:Sequence Homology, Amino Acid; D012984:Software
C086321:CLC-1 channel; D018118:Chloride Channels; D008024:Ligands; D000249:Adenosine Monophosphate; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate; D003541:Cystathionine beta-Synthase