Ca2+ release from the sarcoplasmic reticulum mediated by the cardiac ryanodine 
receptor (RyR2) is a fundamental event in cardiac muscle contraction. RyR2 
mutations suggested to cause defective Ca2+ channel function have recently been 
identified in catecholaminergic polymorphic ventricular tachycardia (CPVT) and 
arrhythmogenic right ventricular dysplasia (ARVD) affected individuals. We 
report expression of three CPVT-linked human RyR2 (hRyR2) mutations (S2246L, 
N4104K, and R4497C) in HL-1 cardiomyocytes displaying correct targeting to the 
endoplasmic reticulum. N4104K also localized to the Golgi apparatus. Phenotypic 
characteristics including intracellular Ca2+ handling, proliferation, viability, 
RyR2:FKBP12.6 interaction, and beat rate in resting HL-1 cells expressing mutant 
hRyR2 were indistinguishable from wild-type (WT) hRyR2. However, Ca2+ release 
was augmented in cells expressing mutant hRyR2 after RyR activation (caffeine 
and 4-chloro-m-cresol) or beta-adrenergic stimulation (isoproterenol). 
RyR2:FKBP12.6 interaction remained intact after caffeine or 4-CMC activation, 
but was dramatically disrupted by isoproterenol or forskolin, an activator of 
adenylate cyclase. Isoproterenol and forskolin elevated cyclic-AMP to similar 
magnitudes in all cells and were associated with equivalent hyperphosphorylation 
of mutant and WT hRyR2. CPVT-linked mutations in hRyR2 did not alter resting 
cardiomyocyte phenotype but mediated augmented Ca2+ release on RyR-agonist or 
beta-AR stimulation. Furthermore, equivalent interaction between mutant and WT 
hRyR2 and FKBP12.6 was demonstrated.