A divergent CFTR homologue: highly regulated salt transport in the euryhaline teleost F. heteroclitus

• DOI: 10.1152/ajpcell.1998.274.3.c715
• Publication Date: 2017-12-24T16:46:05Z
• Authors: Thomas D. Singer; Stephen J. Tucker; William S. Marshall; Christopher F. Hi...
• Keywords: 0303 health sciences; DNA, Complementary; Killifishes; Xenopus; Molecular Sequence Data; Cystic Fibrosis Transmembrane Conductance Regulator; Gene Expression; Water-Electrolyte Balance; Adaptation, Physiological; 03 medical and health sciences; Cyclic AMP; Animals; Humans; Amino Acid Sequence; Calcium Channels; 14. Life underwater; Sequence Alignment

The killifish, Fundulus heteroclitus, is a euryhaline teleost fish capable of adapting rapidly to transfer from freshwater (FW) to four times seawater (SW). To investigate osmoregulation at a molecular level, a 5.7-kilobase cDNA homologous to human cystic fibrosis transmembrane conductance regulator (hCFTR) was isolated from a gill cDNA library from SW-adapted killifish. This cDNA encodes a protein product (kfCFTR) that is 59% identical to hCFTR, the most divergent form of CFTR characterized to date. Expression of kfCFTR in Xenopus oocytes generated adenosine 3′,5′-cyclic monophosphate-activated, Cl−-selective currents similar to those generated by hCFTR. In SW-adapted killifish, kfCFTR was expressed at high levels in the gill, opercular epithelium, and intestine. After abrupt exposure of FW-adapted killifish to SW, kfCFTR expression in the gill increased severalfold, suggesting a role for kfCFTR in salinity adaptation. Under similar conditions, plasma Na+levels rose significantly after 8 h and then fell, although it is not known whether these changes are directly responsible for the changes in kfCFTR expression. The killifish provides a unique opportunity to understand teleost osmoregulation and the role of CFTR.