title: Expression and localization of organic cation/carnitine transporter OCTN2 in Caco-2 cells.
abstract: l-Carnitine is derived both from dietary sources and biosynthesis. Dietary carnitine is absorbed in the small intestine and then distributed to other organs. Previous studies using Caco-2 cells demonstrated that the transport of l-carnitine in the intestine involves a carrier-mediated system. The purpose of this study was to determine whether the uptake of l-carnitine in Caco-2 cells is mediated by the recently identified organic cation/carnitine transporter (OCTN2). Kinetics of l-[(3)H]carnitine uptake were investigated with or without specific inhibitors. l-Carnitine uptake in mature cells was sodium dependent and linear with time. K(m) and V(max) values for saturable uptake were 14.07 +/- 1.70 micro M and 26.3 +/- 0.80 pmol. mg protein(-1). 6 min(-1), respectively. l-carnitine uptake was inhibited (P < 0.05-0.01) by valproate and other organic cations. Anti-OCTN2 antibodies recognized a protein in the brush-border membrane (BBM) of Caco-2 cells with an apparent molecular mass of 60 kDa. The OCTN2 expression was confirmed by double immunostaining. Our results demonstrate that l-carnitine uptake in differentiated Caco-2 cells is primarily mediated by OCTN2, located on the BBM.
authors.affiliation: Divisions of Medical Genetics and Gastroenterology, Research Center, Hôpital Sainte-Justine, Department of Pediatrics, Université de Montréal, Montreal, Quebec, Canada H3T 1C5.
authors.forename: Ihsan
authors.initials: I
authors.lastname: Elimrani
authors.forename: Karim
authors.initials: K
authors.lastname: Lahjouji
authors.forename: Ernest
authors.initials: E
authors.lastname: Seidman
authors.forename: Marie-Josee
authors.initials: MJ
authors.lastname: Roy
authors.forename: Grant A
authors.initials: GA
authors.lastname: Mitchell
authors.forename: Ijaz
authors.initials: I
authors.lastname: Qureshi
mesh_terms: D001693:Biological Transport, Active / Q000187:drug effects; D015153:Blotting, Western; D018938:Caco-2 Cells; D002331:Carnitine / Q000378:metabolism*; D002352:Carrier Proteins / Q000032:analysis / Q000378:metabolism*; D002412:Cations / Q000494:pharmacology; D002454:Cell Differentiation; D005455:Fluorescent Antibody Technique; D020869:Gene Expression Profiling; D006801:Humans; D008565:Membrane Proteins / Q000032:analysis / Q000378:metabolism*; D008871:Microvilli / Q000378:metabolism; D027701:Organic Cation Transport Proteins; D000074058:Solute Carrier Family 22 Member 5
chemical_list: D002352:Carrier Proteins; D002412:Cations; D008565:Membrane Proteins; D027701:Organic Cation Transport Proteins; C492020:SLC22A5 protein, human; D000074058:Solute Carrier Family 22 Member 5; D002331:Carnitine