PTPA and dilated cardiomyopathy: Transgenic mice that express a dominant negative version of PP2A (A delta 5) succumb to dilated cardiomyopathy [111] and increased activity of PP2A in mice that are deficient for its regulatory subunit B56alpha lead to a decrease in heart rate and conduction defects as well as increased sensitivity to isoproterenol, a beta-adrenergic receptor agonist [112].