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Transporter Information:
Name: solute carrier family 22 (organic cation transporter), member 5
Symbol: SLC22A5
TC: 2.A.1.19.3
Locations: 5q31
Aliases: OCTN2, SCD
GenBank: AF057164
Swiss-Prot: O76082
Accession Number: NM_003060
PubMed (9618255): Wu X, Prasad PD, Leibach FH, Ganapathy V. cDNA sequence, transport function, and genomic organization of human OCTN2, anew member of the organic cation transporter family.Biochem Biophys Res Commun. 1998 May 29;246(3):589-95. PMID: 9618255 [PubMed - indexed for MEDLINE]

We have cloned OCTN2, a new member of the organic cation transporter family, from a human placental trophoblast cell line. The hOCTN2 cDNA codes for a protein of 557 amino acids with twelve putative transmembrane domains. The octn2 gene, located on human chromosome 5q31, consists of ten exons. The OCTN2-specific transcript, 3.5 kb in size, is expressed widely in human tissues and in cell lines of human origin. At the level of amino acid sequence, OCTN2 is more closely related to OCTN1 than to OCT1, OCT2 and OCT3. When expressed heterologously in HeLa cells, OCTN2 mediates the transport of tetraethylammonium, a prototypical organic cation, in a pH-dependent manner. Several organic cations, including the neurotoxins 1-methyl-4-phenylpyridinium, 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine, and methamphetamine, compete for the OCTN2-mediated transport process.

PubMed (9916797): Nezu J, Tamai I, Oku A, Ohashi R, Yabuuchi H, Hashimoto N, Nikaido H, Sai Y,Koizumi A, Shoji Y, Takada G, Matsuishi T, Yoshino M, Kato H, Ohura T, TsujimotoG, Hayakawa J, Shimane M, Tsuji A. Primary systemic carnitine deficiency is caused by mutations in a gene encodingsodium ion-dependent carnitine transporter.Nat Genet. 1999 Jan;21(1):91-4. PMID: 9916797 [PubMed - indexed for MEDLINE]

Primary systemic carnitine deficiency (SCD; OMIM 212140) is an autosomal recessive disorder characterized by progressive cardiomyopathy, skeletal myopathy, hypoglycaemia and hyperammonaemia. SCD has also been linked to sudden infant death syndrome. Membrane-physiological studies have suggested a defect of the carnitine transport system in the plasma membrane in SCD patients and in the mouse model, juvenile visceral steatosis. Although the responsible loci have been mapped in both human and mouse, the underlying gene has not yet been identified. Recently, we cloned and analysed the function of a novel transporter protein termed OCTN2. Our observation that OCTN2 has the ability to transport carnitine in a sodium-dependent manner prompted us to search for mutations in the gene encoding OCTN2, SLC22A5. Initially, we analysed the mouse gene and found a missense mutation in Slc22a5 in jvs mice. Biochemical analysis revealed that this mutation abrogates carnitine transport. Subsequent analysis of the human gene identified four mutations in three SCD pedigrees. Affected individuals in one family were homozygous for the deletion of a 113-bp region containing the start codon. In the second pedigree, the affected individual was shown to be a compound heterozygote for two mutations that cause a frameshift and a premature stop codon, respectively. In an affected individual belonging to a third family, we found a homozygous splice-site mutation also resulting in a premature stop codon. These mutations provide the first evidence that loss of OCTN2 function causes SCD.

>sp|O76082|OCN2_HUMAN Organic cation/carnitine transporter 2 (Solute carrier family 22, member 5) (High-affinity sodium-dependent carnitine cotransporter) - Homo sapiens (Human).