(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
Pages: 24
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.