title: Distribution, molecular structure and functional analysis of carnitine transporter (SLC22A5) in canine lens epithelial cells.
abstract: While carnitine has been reported to have an anti-oxidative role on the ocular surface, there has been no report on the existence of a carnitine transporter (SLC22A5) in the lens. Therefore, we investigated the carnitine transport activity of canine lens epithelial cells (LEC) and determined the molecular structure of canine SLC22A5. The carnitine transport activity was 7.16 ± 0.48 pmol/mg protein/30 min. Butyrobetaine, the analogue of carnitine, reduced 30% of the activity at 50 µM. A coding sequence of canine carnitine transporter was 1694 bp long and was predicted to encode 557 amino acid polypeptides. The deduced amino acid sequence of canine carnitine transporter showed >80% similarity to that of mouse and human. Western blot analysis detected the band at 60 kDa in the membrane of lens epithelial cells. The high content of carnitine in the lens is possibly transported from aqueous humor by SLC22A5.
authors.affiliation: Research Institute of Biosciences, Azabu University, 1-17-71 Fuchinobe, Chuo-ku, Sagamihara, Kanagawa 252-5201, Japan.
authors.forename: Hideharu
authors.initials: H
authors.lastname: Ochiai
authors.forename: Nobuyuki
authors.initials: N
authors.lastname: Kanemaki
authors.forename: Reiichiro
authors.initials: R
authors.lastname: Sato
authors.forename: Ken
authors.initials: K
authors.lastname: Onda
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001082:Aqueous Humor / Q000378:metabolism; D001483:Base Sequence; D001622:Betaine / Q000031:analogs & derivatives / Q000378:metabolism; D002331:Carnitine / Q000378:metabolism; D002460:Cell Line; D004285:Dogs; D004847:Epithelial Cells / Q000378:metabolism*; D006801:Humans; D007908:Lens, Crystalline / Q000166:cytology*; D008297:Male; D051379:Mice; D027701:Organic Cation Transport Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D021381:Protein Transport; D000074058:Solute Carrier Family 22 Member 5
chemical_list: D027701:Organic Cation Transport Proteins; C492020:SLC22A5 protein, human; D000074058:Solute Carrier Family 22 Member 5; D001622:Betaine; C002889:gamma-butyrobetaine; D002331:Carnitine