Two Highly Homologous Members of the ClC Chloride Channel Family in both Rat and Human Kidney

• Published in: Proceedings of the National Academy of Sciences - PNAS 1994-07, Vol.91 (15), p.6943-6947
• Main Authors: Kieferle, Stefanie, Fong, Peying, Bens, Marcelle, Vandewalle, Alain, Jentsch, Thomas J.
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence; Amino acids; Anatomy & physiology; Animals; Base Sequence; chloride channels; Chloride Channels - chemistry; Chloride Channels - metabolism; Cloning, Molecular; Complementary DNA; Complementary RNA; DNA; Genetics; Glycosylation; hClC-Ka gene; Humans; kidney; Kidney - metabolism; Kidneys; man; Molecular Sequence Data; Mutagenesis, Site-Directed; Nephrons; nucleotide sequence; Oocytes; Polymerase chain reaction; prediction; Proteins; Rats; Reverse transcriptase polymerase chain reaction; RNA; Rodents; Sequence Homology, Amino Acid; Tissue Distribution
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.91.15.6943

We have cloned two closely related putative Cl-channels from both rat kidney (designated rClC-K1 and rClC-K2) and human kidney (hClC-Ka and hClC-Kb) by sequence homology to the ClC family of voltage-gated Cl-channels. While rClC-K1 is nearly identical to ClC-K1, a channel recently isolated by a similar strategy, rClC-K2 is 80% identical to rClC-K1 and is encoded by a different gene. hClC-Ka and hClC-Kb show ≈ 90% identity, while being ≈ 80% identical to the rat proteins. All ClC-K gene products are expressed predominantly in the kidney. While rClC-K1 is expressed strongly in the cortical thick ascending limb and the distal convoluted tubule, with minor expression in the S3 segment of the proximal tubule and the cortical collecting tubule, rClC-K2 is expressed in all segments of the nephron examined, including the glomerulus. Since they are related more closely to each other than to the rat proteins, hClC-Ka and hClC-Kb cannot be regarded as strict homologs of rClC-K1 or rClC-K2. After injection of ClC-K cRNAs into oocytes, corresponding proteins were made and glycosylated, though no additional Cl-currents were detectable. Glycosylation occurs between domains D8 and D9, leading to a revision of the transmembrane topology model for ClC channels.