Organic cation transporter novel 1 (OCTN1): beyond an ergothioneine transporter

In this review we comprehensively discuss organic cation transporter novel 1 (OCTN1), encoded by the SLC22A4 gene as a member in the solute carrier 22 (SLC22) family, which facilitates the cellular transport of diverse cationic and zwitterionic substrates. OCTN1 is highly expressed in many vital organs in humans, where it facilitates absorption and distribution of both endogenous compounds and therapeutic drugs. Among its substrates, ergothioneine (EGT) serves as the primary antioxidant and anti-inflammatory molecule, underscoring the essential role of OCTN1 in cellular defense and inflammation control. Genetic polymorphisms in SLC22A4 significantly alter OCTN1 expression, substrate affinity, and drug pharmacokinetics, with strong associations to susceptibility and treatment outcomes in human diseases. Insights from knockout models revealed that OCTN1 deficiency leads to reduced EGT availability, heightened oxidative stress, and aggravated inflammation, particularly in the tissues such as intestine, liver and lung. Moreover, OCTN1 activity is dynamically regulated by epigenetic modifications, cytokines, and hormones, linking it to immune modulation and disease progression. Put together, OCTN1 plays a defined role via high-affinity EGT transport, while its broader transport capacity and pharmacological relevance remain under investigation, with possible - though not yet established - implications for inflammation-associated biomarker development.