Identification and characterization of a putative C-elegans potassium channel gene (Ce-slo-2) distantly related to Ca2+-activated K+ channels

Two putative homologues of large conductance Ca2+-activated KI channel alph a-subunit gene (slowpoke or slo) were revealed by C. elegans genome sequenc ing. One of the two genes, F08B12.3 (Ce-slo-2), shows a relatively low amin o acid sequence similarity to other Slo sequences and lacks key functional motifs, which are important for calcium and voltage sensing. However, its o verall structure and regions of homology, which are conserved in all Slo pr oteins, suggest that Ce-SLO-2 should belong to the Slo channel family. We h ave cloned a full-length cDNA of the Ce-slo-2, which encodes a protein cont aining six putative transmembrane segments with a K+-selective pore and a l arge C-terminal cytosolic domain. Green fluorescent protein (GFP) and whole -mount immunostaining analyses revealed that Ce-slo-2 is specifically expre ssed in neuronal cells at the nerve ring, at the ventral nerve cord of the mid-body, and at the tail region. We have also identified a putative human counterpart of Ce-slo-2 from a human brain EST database, which shows a stre tch of highly conserved amino acid residues. Northern blot and mRNA dot blo t analyses revealed a strong and specific expression in brain and skeletal muscle. Taken together, our data suggest that Ce-slo-2 may constitute an ev olutionarily conserved gene encoding a potassium channel that has specific functions in neuronal cells. (C) 1999 Elsevier Science B.V. All rights rese rved.