Figure 2. Antigen-induced entry of Sr2+ and Ca2+ via a STIM1/Orai1/TRPC complex.

Figure 2

Antigen-induced entry of Sr2+ and Ca2+ via a STIM1/Orai1/TRPC complex. Changes in cytosolic Ca2+ and Sr2+ were monitored by single cell imaging of fura 2-loaded RBL-2H3 cells. Cells were stimulated with antigen (Ag) in Ca2+-free medium except for the periods indicated by the bars when either 3 mM Sr2+ or 1 mM Ca2+ were included in the medium. The trace reflects release of Ca2+ from intracellular stores (1st peak), entry of Sr2+ (2nd peak) and of Ca2+ (3rd peak). The model proposed is that on depletion of ER stores and dissociation of Ca2+ from STIM1, STIM1 ologomerizes, translocates to ER/plasma membrane junctions and interacts with a TRPC5 and Orai1 complex to activate entry of Sr2+ (via TRPC5) and Ca2+ (via TRPC5 and Orai1).49 Similar results have been obtained in BMMC and human mast cells derived from peripheral blood.

From: REGULATORS OF CA2+ SIGNALING IN MAST CELLS Potential Targets for Treatment of Mast-Cell Related Diseases?

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