Figure 4. SOICR in HEK-293 cells co-expressing RyR2 and FKBP12.6.

HEK-293 cells expressing both RyR2 and FKBP12.6 were grown on glass coverslips. The cells were induced with tetracycline for 30 h and loaded with 5 μM fura 2/AM in KRH buffer for 20 min at room temperature. The cells were continuously perfused with KRH buffer with 1.0 mM CaCl₂ in the presence or absence of various concentrations of K201 or 10 mM caffeine. Fura 2 ratios of representative cells determined using single-cell Ca²⁺ imaging are shown (A, B). (C) Percentage of SOICR activity at various concentrations of K201. Results shown are means±S.E.M. (n=117 cells) from three separate experiments. (D) Western blots of RyR2 and FKBP12.6 immunoprecipitated with the anti-RyR antibody from lysate of the co-expressing HEK-293 cells treated with 0, 1 and 2 μM FK506. (E) Percentage of SOICR activity in cells treated with (n=73) or without 2 μM FK506 (n=42) in the presence of 30 μM K201. Results shown are means±S.E.M.