Mutants of a Temperature-Sensitive Two-P Domain Potassium Channel

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Abstract
Within theCaenorhabditis elegansgenome there exist at least 42 genes encoding TWK (two-P domain K+) channels, potassium channel subunits that contain two pore regions and four transmembrane domains. We now report the first functional characterization of a TWK channel fromC. elegans. Although potassium channels have been reported to be activated by a variety of factors, TWK-18 currents increase dramatically with increases in temperature. Two mutant alleles of thetwk-18gene confer uncoordinated movement and paralysis inC. elegans. Expression of wild-type and mutant TWK-18 channels inXenopusoocytes showed that mutant channels express much larger potassium currents than wild-type channels. Promoter–green fluorescent protein fusion experiments indicate that TWK-18 is expressed in body wall muscle. Our genetic and physiological data suggest that the movement defects observed in mutanttwk-18animals may be explained by an increased activity of the mutant TWK-18 channels.