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. Ubiquitously expressed. By 1,25-dihydroxyvitamin D3 and phosphate deprivation. Belongs to the inorganic phosphate transporter (PiT) (TC 2.A.20) family.