Figure 5. JPH2-derived small peptide stabilizes RyR2-mediated SR Ca²⁺ leak in atrial myocytes from JPH2 knockdown mice.

A, Representative confocal line scan images showing spontaneous Ca²⁺ sparks recorded from permeabilized atrial myocytes treated with vehicle only (upper left), JPH2 peptide at 1 μM (upper right), JPH2 peptide at 10 μM (bottom left), and scrambled control peptide (10 μM, bottom right). B, Bar graph showing Ca²⁺ spark frequency (CaSpF), which was significantly decreased by JPH2-derived peptide but not by scrambled control peptides. **P<0.01, ***P<0.001. Numbers indicate number of cells (number of mice). C, Representative planar lipid bilayer RyR2 single channel tracings from Mer-Cre-Mer (Control) and JPH2 knockdown (JPH2-KD) mice at baseline (top) and with the addition of JPH2 peptide (bottom). D, Bar graph showing significant increase in RyR2 open probability (Po) in JPH2-KD vs control and significant reduction in RyR2 Po with the addition of JPH2 peptide in JPH2-KD mice. P <0.05