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

• Published in: American Journal of Physiology: Cell Physiology Vol. 274; no. 3; p. C715
• Main Authors: Singer, Thomas D, Tucker, Stephen J, Marshall, William S, Higgins, Christopher F
• Format: Journal Article
• Language: English
• Published: United States 01.03.1998
• Subjects: gill; osmoregulation; chloride channel; Xenopusexpression; cystic fibrosis; cystic fibrosis transmembrane conductance regulator; killifish; Fundulus heteroclitus

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.