CaTAr2 inhibits Ca ²⁺ tunneling. (A) Localization of CaTAr2 relative to STIM1-CFP before (Ctr) and after store depletion (CPA). Colocalization analysis using either intensity plots along the white line or PCC measurements confirms that CaTAr2 localizes in a similar fashion to CaTAr1 and MAPPER relative to STIM1 clusters (n = 5–10; unpaired t test). (B) Colocalization of MAPPER–GFP and CaTAr2 at the whole cell level. (C) Localization and PCC between CaTAr2 and IP₃R1–GFP. The colocalization of CatAr2 with MAPPER was used as a reference value for the PCC analysis (n = 6–14; unpaired t test). (D) Confocal images of HeLa cells expressing CaTAr2 and loaded with Fluo4-AM. The numbered cells refer to the traces in E and F. (E) Ca²⁺ tunneling traces obtained after store depletion with CPA indicate that cells expressing CaTAr2 have a lower tunneling capacity. The bar chart on the right summarizes the inhibition of Ca²⁺ tunneling by CaTAr2. (F) Ca²⁺ release traces were obtained on the same cells as in E by applying histamine (His, 100 μM) after store refilling. The bar chart on the right summarizes the effect of CaTAr2 on Ca²⁺ release (n = 42–342; unpaired t test).