SLC29A1 encodes equilibrative nucleoside transporter 1 (ENT1), a sodium-independent membrane transporter that facilitates the bidirectional transport of nucleosides and nucleobases across cell membranes 1. The protein transports various substrates including adenosine, guanosine, inosine, uridine, thymidine, cytidine, and purine/pyrimidine nucleobases, as well as nicotinamide, a key NAD+ precursor 2. ENT1 plays critical roles in cellular metabolism by regulating nucleoside homeostasis and maintaining NAD+ pools, which impacts cellular respiration, energy production, and senescence 2. In brown adipose tissue, ENT1 regulates extracellular inosine levels, controlling thermogenic capacity and energy expenditure, with ENT1 deficiency enhancing thermogenesis and protecting against diet-induced obesity 1. The transporter has significant therapeutic implications in cancer, where it mediates gemcitabine uptake and its expression affects treatment response 3. Additionally, ENT1 modulates immune responses by regulating adenosine-mediated immunosuppression and T-cell function, with ENT1 inhibition enhancing antitumor immunity and potentiating PD-1 blockade therapy 4. ENT1 also represents a potential target for non-opioid pain management through adenosine A1 receptor pathway modulation 5.