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- Title
Dissociation of the store-operated calcium current I<sub>CRAC</sub> and the Mg-nucleotide-regulated metal ion current MagNuM.
- Authors
Hermosura, Meredith C.; Monteilh-Zoller, Mahealani K.; Scharenberg, Andrew M.; Penner, Reinhold; Fleig, Andrea
- Abstract
Rat basophilic leukaemia cells (RBL-2H3-M1) were used to study the characteristics of the store-operated Ca2+ release-activated Ca2+ current ( ICRAC) and the magnesium-nucleotide-regulated metal cation current (MagNuM) (which is conducted by the LTRPC7 channel). Pipette solutions containing 10 m m BAPTA and no added ATP induced both currents in the same cell, but the time to half-maximal activation for MagNuM was about two to three times slower than that of ICRAC. Differential suppression of ICRAC was achieved by buffering free [Ca2+]i to 90 n m and selective inhibition of MagNuM was accomplished by intracellular solutions containing 6 m m Mg.ATP, 1.2 m m free [Mg2+]i or 100 μ m GTP-γ-S, allowing investigations on these currents in relative isolation. Removal of extracellular Ca2+ and Mg2+ caused both currents to be carried significantly by monovalent ions. In the absence or presence of free [Mg2+]i, ICRAC carried by monovalent ions inactivated more rapidly and more completely than MagNuM carried by monovalent ions. Since several studies have used divalent-free solutions on either side of the membrane to study selectivity and single-channel behaviour of ICRAC, these experimental conditions would have favoured the contribution of MagNuM to monovalent conductance and call for caution in interpreting results where both ICRAC and MagNuM are activated.
- Publication
Journal of Physiology, 2002, Vol 539, Issue 2, p445
- ISSN
0022-3751
- Publication type
Article
- DOI
10.1113/jphysiol.2001.013361