PDZK1 is PDZ domain-containing scaffolding protein with a 519 amino acid protein. PDZK1 mediates the localization of cell surface proteins and plays a critical role in cholesterol metabolism by regulating the HDL receptor, scavenger receptor class B type 1. This protein is expressed in the kidney, pancreas, liver, gastrointestinal tract, and adrenal cortex. In situ hybridization experiments showed that the expression of PDZK1 was limited to epithelial cells. In addition, PDZK1 was overexpressed in selected tumors of epithelial origin.