Involved in actively transporting phosphate into cells via Na(+) cotransport in the renal brush border membrane (PubMed:8070635, PubMed:7478940). The cotransport has a Na(+):Pi stoichiometry of 3:1 and is electrogenic (By similarity). 3 Na(+)(out) + phosphate(out) = 3 Na(+)(in) + phosphate(in) Interacts via its C-terminal region with PDZK2 (PubMed:11950846). Interacts with SLC9A3R1 (By similarity). Localized at the brush border membranes of the proximal tubules. Kidney. Up-regulated by low-phosphate diet. Belongs to the SLC34A transporter family. Extended N-terminus.