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This Article Full Text Full Text (PDF) All Versions of this Article: 553/2/387    most recent jphysiol.2003.055335v1 Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Bakowski, D. Articles by Parekh, A. B. Search for Related Content PubMed PubMed Citation Articles by Bakowski, D. Articles by Parekh, A. B.

Activation of the store-operated calcium current I_CRAC can be dissociated from regulated exocytosis in rat basophilic leukaemia (RBL-1) cells

Daniel Bakowski, Robert D. Burgoyne* and Anant B. Parekh

In many cell types, the emptying of intracellular Ca²⁺ stores results in the opening of store-operated Ca²⁺ channels in the plasma membrane. However, the nature of the signal that couples store content to the opening of these Ca²⁺ channels is unclear. One model proposes that the Ca²⁺ channels are initially stored in cytoplasmic vesicles but inserted into the plasma membrane upon store depletion via a regulated exocytoytic mechanism (vesicular fusion model). Using the whole-cell patch-clamp technique to measure the store-operated Ca²⁺ current I_CRAC and the capacitance method to monitor vesicular fusion, an indicator of exocytosis, we have investigated the effects of interfering with regulated exocytosis on the ability of I_CRAC to activate. We find that the recombinant protein -SNAP^1-285, an inhibitor of exocytosis in many systems, suppresses such fusion but has no impact on the activation of I_CRAC. A variety of other manoeuvres that interfere with vesicle trafficking and exocytosis were also without effect on I_CRAC. Impairing constitutive exocytosis with brefeldin A reduced the extent of I_CRAC, but this effect was less pronounced when current density was considered instead. Activation of I_CRAC can therefore be clearly dissociated from an exocytotic mechanism, a finding that is not easily reconcilable with the vesicular fusion model.

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