Carnitine transporter 1 (OCTN2)

The principal **carnitine transporter in human tissues is Carnitine transporter 1 (OCTN2, SLC22A5)**. This transporter is a member of the solute carrier (SLC22) family and is found ubiquitously across tissues, including the heart, skeletal muscle, kidneys, placenta, and brain[4][2][8]. Its essential function is to mediate the high-affinity, sodium-dependent uptake of L-carnitine into cells, where carnitine is then used to transport long-chain fatty acids across the mitochondrial membrane for β-oxidation (the "carnitine shuttle"), ultimately supporting fatty acid metabolism and energy production[1][2][6][4]. OCTN2 also plays a critical role in detoxification, regulation of metabolic flexibility (by influencing the ratio of acyl-CoA to CoA), and protecting cells against oxidative stress[6][9]. Loss of function mutations in SLC22A5 result in **primary carnitine deficiency** (systemic carnitine deficiency), a rare but potentially fatal inborn error of metabolism, typically presenting with hypoglycemia, cardiomyopathy, skeletal muscle weakness, and, in some cases, sudden death[10][4]. OCTN2 also mediates the transport of certain drugs, including oxaliplatin and other chemotherapeutics. This means changes to transporter function can influence both therapeutic efficacy and off-target toxicity for these drugs[8]. Additional carnitine transporters include **carnitine transporter 2 (CT2, SLC22A16)**, which appears to play a role in reproductive tissues and has been implicated in some cancers, and **SLC6A14**, which is another plasma membrane carnitine transporter with distinct tissue distribution[7][5][8]. The effectiveness of L-carnitine supplementation and the monitoring of therapy or deficiency can be supported by plasma carnitine measurements and acylcarnitine/carnitine ratios, which serve as biomarkers for transporter function or disease state. Defects or altered regulation of carnitine transporters are implicated in metabolic disorders, cardiovascular and liver disease, certain cancers, and male infertility due to their central role in energy metabolism and cellular homeostasis[2][3][4][5][7][8].

Other names

SLC22A5Organic cation transporter novel type 2CT1OCTN2

Facilitates cellular uptake of L-carnitine (Na^+-dependent and high affinity transport), Transports carnitine across plasma membrane for mitochondrial fatty acid entry, Influences drug disposition (notably some chemotherapeutics such as oxaliplatin)