(full paper is archived in the Miller Library)
Title: Ca2+ Influx through the mTRPM7 channel is inhibited by
Mg2+ and Gd3+
Student Author(s): Ta, Jenny
Faculty Advisor(s): Thompson, Stuart
Location: Final papers Biology 176H
Date: June 2004
Abstract: The family of TRP ion channels constitutes a fairly recent set of cation channels found in almost all cell types, with diverse roles ranging from mediating responses of nerve growth factors to regulation of temperature and vasorelaxation of blood vessels. Such a plethora of functions also reflect diverse permeability to ions. In this study, the specific member TRPM7 is tested to understand its role in calcium regulation. As an initial test of the possibility that TRPM7 channels contribute to regulation of Ca2+ influx, [Ca2+]i was measured by the fluorescent Ca2+ indicator, Fluo-3-AM, using confocal laser microscopy. In cells in which TRPM7 channel expression was induced and the cells were perfused with Ca2+ - free solution, restoration of extracellular Ca2+ (2mM) caused marked increases in [Ca2+]i; whereas non-induced cells did not show much change in [Ca2+]i. From the proportion of Ca2+ that is taken into the cell, it is plausible that TRPM7 is a vital mode of Ca2+ entry. a second test looked at the effects of Gd3+ (20uM) on Ca2+ influx. The introduction Gd2+ quenched fluo-3 fluorescence, indicating that Gd3+ blocked conductance of Ca2+ through the TRPM7 channel. A final experiment was conducted to analyze the effects of adding Mg2+. Results indicate that the addition of extracellular Mg2+ (2mM) reduces Ca2+ influx. This shows an interaction of both internal and external Mg2+ in the regulation of TRPMY in clocking Ca2+ influx and in allowing Mg2+ influx. Importance of magnesium regulation is indicative of a role for TRPM7 in magnesium homeostasis.