Figure 3.

Interplay of rogue and clustered RyRs in a JSR. Snapshots of Ca²⁺ release events in a region of 5 µm × 5 µm are taken at 10, 20 and 40 ms from left to right when three rogue RyRs are fired at the same time. There are three distinct modes. Schematic interplay of Ca²⁺ release events is plotted below the snapshots. Clustered and rogue RyRs are distinguished by blue and red colours similar to figure 1c. Cytoplasmic Ca²⁺ is displayed by pink colour. Arrows denote that Ca²⁺ diffuses and activates neighbour clustered and rogue RyRs in the cytoplasm. SR, sarcoplasmic reticulum; TT, T-tubule. (a) No activated Ca²⁺ spark. Neighbour rogue RyRs are activated by Ca²⁺ quarks. (b) A Ca²⁺ spark with one quantal unit. One CRU of clustered RyRs is initiated by Ca²⁺ quarks. Then Ca²⁺ spark from the CRU of clustered RyRs contributes to activation of neighbour rogue RyRs. (c) A Ca²⁺ spark with two quantal units. Two CRUs of clustered RyRs are triggered and then activate neighbour rogue RyRs.