Key result
A novel inward rectifier K+ channel (eKir) was identified and found to be highly expressed in the chloride cells of seawater eel gills, suggesting a role in osmoregulation.
Identifies a novel hypertonicity-inducible inward rectifier potassium channel (eKir) in eels, suggesting a role in osmoregulation.
Hypothesis-generating for epithelial Kir channels; leaves open relevance to human cardiac electrophysiology.
By using differential mRNA display to monitor the molecular alterations associated with adaptation of euryhaline eels to different salinities, we identified a cDNA fragment strongly induced in seawater eel gills. Cloning of a full-length cDNA and its expression in COS-7 cells indicated that the clone codes for an inward rectifier K+ channel (eKir) of 372 amino acid residues, which has two transmembrane segments and a typical pore-forming region (H5). Only low sequence similarities are present, except the H5 region, compared with other members of the inward rectifier K+ channel family (Kir). Consistent with this divergence in the amino acid sequence, a phylogenetic analysis indicated early divergence and independent evolution of eKir from other members; it is only distantly related to the Kir5.0 subfamily members. RNase protection analysis showed that eKir is highly expressed in the seawater eel gill, kidney, and posterior intestine but very weakly in freshwater eels. Immunohistochemistry of gill sections revealed dense localization of eKir in the chloride cells. Immunoelectron microscopy indicated that eKir is mainly present in the microtubular system in the chloride cell. This location and its salt-inducible nature suggest that the eKir channel cloned here is a novel member of the Kir5.0 subfamily of the Kir family and is implicated in osmoregulation.
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Suzuki et al. (1999) studied Osmoregulation in euryhaline eels. Seawater adaptation vs. Freshwater adaptation was evaluated on Identification and expression of eKir. A novel inward rectifier K+ channel (eKir) was identified and found to be highly expressed in the chloride cells of seawater eel gills, suggesting a role in osmoregulation.
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