SLC29A2 encodes equilibrative nucleoside transporter 2 (ENT2), a membrane protein mediating bidirectional transport of nucleosides and nucleobases across cell membranes 1. ENT2 functions as a facilitative diffusion transporter with broad substrate selectivity, transporting adenosine (Ki 2.6 μM), hypoxanthine, inosine, cytidine, uridine, and guanine 12. Recently, SLC29A2 was identified as a cellular transporter of nicotinamide (NAM), a key NAD+ precursor, regulating NAD+ pool levels and cellular respiration 3. ENT2 also facilitates transport of the thyroid hormone analog TRIAC and urate, the purine metabolite, suggesting broader physiological roles 42. In renal epithelia, ENT2 localizes to basolateral membranes, participating in nucleoside reabsorption 5. Clinically, SLC29A2 expression varies heterogeneously in colorectal cancer cell lines, with lower expression in metastatic versus primary tumors, potentially affecting chemotherapy response to nucleoside analogs 6. ENT2 expression in endothelial cells modulates adenosine bioavailability and NO metabolism, with altered expression associated with gestational diabetes pathophysiology 7. This multifunctional transporter integrates nucleoside, metabolite, and drug transport with cellular bioenergetics and signaling.