Roles of Metal Transporters in Cellular Cadmium Transport in Mammals

The mechanisms underlying tissue cadmium (Cd) accumulation in mammals have long been investigated with a focus on the roles of metallothionein, a high-affinity Cd-binding protein. However, the precise mechanisms underlying the influx and efflux of Cd at the cell membrane have remained unclear. As Cd is not an essential element, the transport pathways for essential elements are thought to be utilized for Cd transport, especially for entry into cells. Recently, the roles of metal transporters for iron, calcium, zinc, and manganese in cellular Cd transport have begun to be elucidated. The expression and roles of these transporters vary depending on the tissue or cell types and the nutritional statuses of the elements. Consequently, the usage of metal transporters for Cd transport is also altered depending on the tissue and nutritional status of an element. In this chapter, recent advances in understanding the mechanisms underlying cellular Cd transport from the standpoint of the roles of metal transporters are discussed.