Abstract

Background: ClC-3, a member of the ClC family, is predicted to have six isoforms, ClC-3a to -3f, with distinct N- and C-terminal amino acid sequences. There have been conflicting reports on the properties of ClC-3a (also known as the N-terminal short form of ClC-3) and ClC-3b (the N-terminal long form of ClC-3) as plasmalemmal Cl<sup>-</sup> channels. Meanwhile, little is known about other isoforms. The amino acid sequence of ClC-3d (a C-terminal variant of the short form) listed in the NCBI database was derived from the genomic sequence, but there has been no experimental evidence for the mRNA. Methods: PCR-cloning was made to obtain the full coding region of ClC-3d from mouse liver. Its molecular expression on the plasma membrane was microscopically examined in HEK293T cells transfected with GFP-tagged ClC-3d. Its functional plasmalemmal expression and the properties of currents were studies by whole-cell recordings in the cells transfected with ClC-3d. Results: The cloned ClC-3d was found to be the only isoform which has an N-terminal amino acid sequence identical to ClC-3a. When introduced into HEK293T cells, a minor fraction of exogenous ClC-3d proteins was detected at the plasma membrane, and activation of anion currents was observed at neutral pH under normotonic conditions. The properties of ClC-3d currents were found to be shared by ClC-3a-mediated currents. Also, both ClC-3d and -3a currents were found to be sensitive to Cd<sup>2+</sup>. ClC-3d overexpression never affected the endogenous activity of acid- or swelling-activated anion channels. Conclusion: We thus conclude that plasmalemmal ClC-3d, like ClC-3a, mediates Cd<sup>2+</sup>-sensitive outwardly rectifying anion currents and that ClC-3d is distinct from the molecular entities of acid- and volume-sensitive anion channels.

Talk to us

Join us for a 30 min session where you can share your feedback and ask us any queries you have

Schedule a call

Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.