Tmem174 of 243 aas and 2 adjacent N-terminal TMSs. Tmem174 is localized in the renal proximal tubules and interacts with NaPi2a, but not NaPi2c. In Tmem174-knockout (KO) mice, the serum FGF23 concentration was markedly increased. Tmem174-KO mice exhibit reduced NaPi2a responsiveness to FGF23 and PTH administration (see family description). A dietary Pi load caused marked hyperphosphatemia and abnormal NaPi2a regulation in Tmem174-KO mice. Thus, Tmem174 is thought to be associated with FGF23 induction in bones and the regulation of NaPi2a to prevent an increase in the plasma Pi concentration due to a high Pi load and kidney injury (Sasaki et al. 2022).