Recent developments in intestinal magnesium absorption.

PURPOSE OF REVIEW: Recent identification and characterization of novel Mg transporters have clarified our understanding of intestinal magnesium absorption. The predominant Mg transporters include TRPM6 and TRPM7, members of the transient receptor potential melastatin family of cation channels. Mutations of TRPM6 result in a primary disorder termed hypomagnesemia with secondary hypocalcemia.

RECENT FINDINGS: Both TRPM6 and TRPM7 channels possess an atypical alpha-kinase domain. Recent studies have shown that TRPM7 channel activity is regulated by intracellular Mg and magnesium-nucleotides and modulated via this phosphotransferase kinase. TRPM6 channel function and intestinal magnesium absorption is altered by a variety of hormones and factors. Although it is apparent that TRPM6 and TRPM7 form heteromeric ion channels, controversy surrounds the nature of this interaction. Some studies show that TRPM6 may function on its own whereas other research concludes that TRPM7 is required for effective trafficking of TRPM6 to the plasma membrane. Finally, a number of other Mg transporters have been identified in intestinal epithelial cells but the role of these proteins is unclear.

SUMMARY: The recent developments in intestinal magnesium absorption and cellular magnesium homeostasis provide a basis for understanding magnesium deficiency disorders and provide a platform for future investigations.