Sodium-phosphate symporter which seems to play a fundamental housekeeping role in phosphate transport by absorbing phosphate from interstitial fluid for normal cellular functions such as cellular metabolism, signal transduction, and nucleic acid and lipid synthesis. In vitro, sodium-dependent phosphate uptake is not significantly affected by acidic and alkaline conditions, however sodium-independent phosphate uptake occurs at acidic conditions. May play a role in extracellular matrix, cartilage calcification and vascular calcification (By similarity). Functions as a retroviral receptor for feline leukemia virus subgroup B (FeLV-B). Homodimer. Belongs to the inorganic phosphate transporter (PiT) (TC 2.A.20) family.