Solute carrier family 22 member 5 (OCTN2) (OCTN2)

Solute carrier family 22 member 5 (SLC22A5), commonly known as OCTN2, is the principal transporter responsible for the renal reabsorption of levocarnitine (L-carnitine) from the glomerular filtrate [1, 17]. Located on the apical membrane of renal proximal tubule cells, it functions as a high-affinity, sodium-dependent symporter that recovers over 95% of filtered carnitine to maintain systemic homeostasis [5, 15]. This process is vital for cellular energy production, as carnitine is required to shuttle long-chain fatty acids into the mitochondria for beta-oxidation [4, 23]. Mutations in the SLC22A5 gene lead to primary systemic carnitine deficiency, a condition characterized by life-threatening cardiomyopathy, skeletal muscle weakness, and hypoketotic hypoglycemia [6, 8]. Beyond its physiological role, OCTN2 acts as a polyspecific transporter for various drugs, including certain antibiotics and chemotherapeutics like etoposide and oxaliplatin [1, 12]. Pharmacological inhibition or downregulation of OCTN2 by drugs such as valproic acid or cisplatin can lead to secondary carnitine deficiency and associated toxicities [7, 10, 13]. Consequently, OCTN2 is a significant factor in drug disposition and a key target for managing metabolic and drug-induced carnitine imbalances [12, 24].

Other names

Organic cation/carnitine transporter 2OCTN2Carnitine transporter 1CT1CDSPSystemic carnitine deficiency proteinSLC22A5

Sodium-dependent high-affinity symport of L-carnitine across the apical membrane of renal proximal tubule cells, coupled with the transport of sodium ions in a 1:1 stoichiometry [5, 8]. It also functions as a sodium-independent organic cation transporter, facilitating the secretion of various xenobiotics [1, 21].