Figure 5. The RyR2-E4146K mutaton abolishes store-overload induced Ca²⁺ release (SOICR) in HEK293 cells.

Stable, inducible HEK293 cells expressing RyR2 WT or E4146K were loaded with 5 μM Fura-2 AM in KRH buffer. The cells were then perfused continuously with KRH buffer containing increasing levels of extracellular Ca²⁺ (0–2 mM) to induce SOICR. Fura-2 ratios of representative RyR2 WT (A) and E4146K (B) cells were recorded using single cell Ca²⁺ imaging. (C) The percentages of RyR2 WT (691 cells) and E4146K (466) cells that display Ca²⁺ oscillations at various extracellular Ca²⁺ concentrations. Note that no SOICR was detected in HEK293 cells expressing the E4146K mutant. (D) ER store Ca²⁺ content in RyR2 WT or E4146K mutant expressing HEK293 cells estimated by measuring the amplitude of caffeine (10 mM) induced Ca²⁺ release. Data shown are mean ± SEM (n=3–5, *P<0.05 vs. WT).