The effects of coexpressing TRIC-A or TRIC-B with RyR2 on the response of RyR2 channels to increasing cytosolic [Ca ²⁺ ]. Typical gating behavior of RyR2 is shown from the HEK293 cells expressing RyR2-only (left), RyR2+TRIC-A (middle), and RyR2+TRIC-B (right) at −30 mV in symmetrical 210 mM KPIPES, at the indicated free [Ca²⁺]. In symmetrical 210 mM KPIPES and 10 µM cytosolic Ca²⁺, RyR single-channel conductance from the RyR2-only, RyR2+TRIC-A, and RyR2+TRIC-B cells was 735.7 ± 12.7 pS, 735.0 ± 19.2 pS, and 726.3 ± 9.0 pS, respectively. When cytosolic Ca²⁺ was raised to 1 mM, RyR conductance decreased to 544 ± 22 pS, 549 ± 34 pS, and 557 ± 10 pS for RyR2-only, RyR2+TRIC-A, and RyR2+TRIC-B cells, respectively (n_RyR2 = 10, n_RyR2+TRIC-A = 7, n_RyR2+TRIC-B = 10). The Po (measured over 2 min) is shown above each trace. The zero current level is indicated by C and the fully open channel levels by O1 and O2. The red asterisk highlights subconductance events.