Involved in actively transporting phosphate into cells via Na(+) cotransport in the renal brush border membrane (PubMed:8327470, PubMed:9058191, PubMed:10198426, PubMed:10370077, PubMed:10926678). The cotransport has a Na(+):Pi stoichiometry of 3:1 and is electrogenic (PubMed:10198426). 3 Na(+)(out) + phosphate(out) = 3 Na(+)(in) + phosphate(in) Transport activity is significantly increased in response to dietary phosphate deprivation. Optimum pH is 8.0. Interacts via its C-terminal region with PDZK2. Interacts with SLC9A3R1. =Localized at the brush border membranes of the proximal tubules. Kidney. Up-regulated by a low-phosphate diet (PubMed:9058191). Down-regulated by PTH at brush border membrane of proximal tubules (PubMed:8691716). Belongs to the SLC34A transporter family.