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Capacitative Ca2+ Entry Is Closely Linked to the Filling State of Internal Ca2+ Stores: A Study Using Simultaneous Measurements of I CRAC and Intraluminal [ Ca2+]

Aldebaran M. Hofer, Cristina Fasolato and Tullio Pozzan
The Journal of Cell Biology
Vol. 140, No. 2 (Jan. 26, 1998), pp. 325-334
Stable URL: http://www.jstor.org/stable/1618507
Page Count: 10
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Capacitative  Ca2+ Entry Is Closely Linked to the Filling State of Internal  Ca2+ Stores: A Study Using Simultaneous Measurements of  I CRAC and Intraluminal [ Ca2+]
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Abstract

I CRAC (the best characterized Ca2+ current activated by store depletion) was monitored concurrently for the first time with [ Ca2+] changes in internal stores. To establish the quantitative and kinetic relationship between these two parameters, we have developed a novel means to clamp [ Ca2+] within stores of intact cells at any level. The advantage of this approach, which is based on the membrane-permeant low-affinity Ca2+ chelator N,N,N′,N′-tetrakis (2-pyridylmethyl)ethylene diamine (TPEN), is that [ Ca2+] within the ER can be lowered and restored to its original level within 10-15 s without modifications of Ca2+ pumps or release channels. Using these new tools, we demonstrate here that Ca2+ release-activated Ca2+ current ( I CRAC) is activated (a) solely by reduction of free [ Ca2+] within the ER and (b) by any measurable decrease in [ Ca2+] ER. We also demonstrate that the intrinsic kinetics of inactivation are relatively slow and possibly dependent on soluble factors that are lost during the whole-cell recording.

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