Sodium-phosphate symporter which plays a fundamental housekeeping role in phosphate transport, such as absorbing phosphate from interstitial fluid for normal cellular functions such as cellular metabolism, signal transduction, and nucleic acid and lipid synthesis. May play a role in extracellular matrix and cartilage calcification as well as in vascular calcification. (Microbial infection) May function as a retroviral receptor as it confers human cells susceptibility to infection to Gibbon Ape Leukemia Virus (GaLV), Simian sarcoma-associated virus (SSAV) and Feline leukemia virus subgroup B (FeLV-B) as well as 10A1 murine leukemia virus (10A1 MLV). With an increase in pH, a decrease in phosphate uptake is observed. Optimum pH is 6.5 and 7.5. Ubiquitously expressed. By phosphate deprivation as well as by IL8/interleukin-8 in hypertrophic chondrocytes. Region A confers human cells susceptibility to infection by Gibbon Ape Leukemia Virus (GaLV) and Feline leukemia virus subgroup B (FeLV-B). Substitution of Human SLC20A1 region A by region A of murine SLC20A1 prevents viral infection. Belongs to the inorganic phosphate transporter (PiT) (TC 2.A.20) family.