Mg, Zn and Cu Transport Proteins: A Brief Overview from Physiological and Molecular Perspectives

Essential major and trace elements, including magnesium (Mg), zinc (Zn) and copper (Cu), are involved in numerous physiological processes. These elements are important components for maintaining proper protein structure and function. They are also used as catalytic cofactors for enzymes and as mediators in signaling cascades. Thus, systemic homeostasis of these metals is sophisticatedly regulated at a molecular level. A balance between absorption and excretion of these metals is critical, and transport proteins play a key role in this balance. In particular, transport proteins in intestinal epithelial cells are indispensable and ensure adequate metal absorption. Regulation of the expression and activity of these proteins is complicated. Thus, dysfunction of these proteins causes an imbalance in the systemic homeostasis of corresponding metals, and thus likely links to disease pathogenesis. In this review, we briefly describe the importance of mammalian metal transport proteins, including Mg channels, and Zn and Cu transporters, focusing on their roles in the absorption process in intestinal epithelial cells. Specifically, TRPM6 channels in Mg absorption, ZIP4 and ZnT1 transporters for Zn absorption, and CTR1 and ATP7A for Cu absorption are overviewed.