SLO-2, a K+ channel with an unusual Cl- dependence

The gating of different potassium channels depends on many diverse factors. We now report a unique example of a K+ channel with a Cl- dependence. The slo-2 gene was cloned from Caenorhabditis elegans and is widely expressed i n both neurons and muscles; it was highly abundant, as suggested by its hig h representation in the C. elegans EST database. SLO-2, like its paralogue, SLO-1, was also dependent on Ca2+. We show by site-directed mutagenesis th at its requirements for both Cl- and Ca2+ are synergistic and associated wi th the same functional domain. SLO-2's dependence on Cl- implies that intra cellular Cl- homeostasis may be important in regulating cellular excitabili ty through this unusual K+ channel.