Sodium-phosphate symporter which preferentially transports the monovalent form of phosphate with a stoichiometry of two sodium ions per phosphate ion (PubMed:11009570, PubMed:16790504, PubMed:17494632, PubMed:19726692, PubMed:7929240, PubMed:8041748). May play a role in extracellular matrix and cartilage calcification as well as in vascular calcification (PubMed:11009570). Essential for cell proliferation but this function is independent of its phosphate transporter activity (PubMed:19726692). {ECO:0000269|PubMed:11009570, ECO:0000269|PubMed:16790504, ECO:0000269|PubMed:17494632, ECO:0000269|PubMed:19726692, ECO:0000269|PubMed:7929240, ECO:0000269|PubMed:8041748}. (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). {ECO:0000269|PubMed:12097582, ECO:0000269|PubMed:1309898, ECO:0000269|PubMed:2078500, ECO:0000269|PubMed:7966619}. This is the function of SLC20A1 (solute carrier family 20 member 1, Ensembl gene identifier ENSG00000144136).