SLC5A12 encodes SMCT2 (sodium-coupled monocarboxylate transporter 2), a low-affinity, electroneutral sodium-dependent transporter that mediates cellular uptake of monocarboxylates 1. The transporter catalyzes Na+-coupled transport of various substrates including lactate, pyruvate, nicotinate, propionate, butyrate, and β-D-hydroxybutyrate with 1:1 stoichiometry 21. SLC5A12 is predominantly expressed in the apical membrane of renal proximal tubule cells throughout the S1/S2/S3 segments and in the proximal intestine, where it likely mediates reabsorption of diet-derived monocarboxylates rather than bacterial fermentation products 12. In disease contexts, SLC5A12 plays a pathological role by facilitating lactate uptake in CD4+ T cells at inflammatory sites, promoting IL-17 production and T cell retention that perpetuates chr11 inflammation in conditions like rheumatoid arthritis 34. The transporter also contributes to ectopic lymphoid structure formation in autoimmune diseases 5 and promotes gastric cancer progression 6. Therapeutically, SLC5A12 blockade shows promise for treating chr11 inflammatory disorders by promoting immune cell egress from inflamed tissues 45.