Ca2+ leak via
ryanodine receptor type 2 (
RyR2) can cause potentially fatal arrhythmias in a variety of
heart diseases and has also been implicated in neurodegenerative and
seizure disorders, making
RyR2 an attractive therapeutic target for
drug development. Here we synthesized and investigated the fungal
natural product and known insect RyR antagonist (-)-
verticilide and several congeners to determine their activity against mammalian
RyR2. Although the cyclooligomeric
depsipeptide natural product (-)-
verticilide had no effect, its nonnatural enantiomer [ent-(+)-
verticilide] significantly reduced RyR2-mediated spontaneous Ca2+ leak both in cardiomyocytes from wild-type mouse and from a gene-targeted mouse model of Ca2+ leak-induced arrhythmias (Casq2-/-). ent-(+)-
verticilide selectively inhibited RyR2-mediated Ca2+ leak and exhibited higher potency and a distinct mechanism of action compared with the pan-RyR inhibitors
dantrolene and
tetracaine and the
antiarrhythmic drug flecainide. ent-(+)-
verticilide prevented arrhythmogenic membrane depolarizations in cardiomyocytes without significant effects on the cardiac action potential and attenuated ventricular
arrhythmia in
catecholamine-challenged Casq2-/- mice. These findings indicate that ent-(+)-
verticilide is a potent and selective inhibitor of RyR2-mediated diastolic Ca2+ leak, making it a molecular tool to investigate the therapeutic potential of targeting
RyR2 hyperactivity in heart and brain pathologies. The enantiomer-specific activity and straightforward chemical synthesis of (unnatural) ent-(+)-
verticilide provides a compelling argument to prioritize ent-
natural product synthesis. Despite their general absence in nature, the enantiomers of natural products may harbor unprecedented activity, thereby leading to new scaffolds for probe and therapeutic development.