Peptidylglycine α-amidating monooxygenase is required for atrial secretory granule formation
Nils Bäck, Raj Luxmi, Kathryn G. Powers, Richard E. Mains, Betty Eipper
Abstract
Significance Transmission electron microscopy of atrial cardiomyocytes revealed dense granules resembling those in endocrine cells and neurons, leading to the discovery of the natriuretic peptides stored in these granules. Subsequent studies revealed features unique to atrial granules, including high-level expression of peptidylglycine α-amidating monooxygenase (PAM), an enzyme required for the synthesis of many neuropeptides, but not for the synthesis of natriuretic peptides. The discovery that atrial myocytes lacking PAM are unable to produce granules and that PAM lacking its monooxygenase activity can rescue granule formation provides new information about the proANP secretory pathway. A better understanding of the unique features of atrial cell biology should provide insight into atrial fibrillation, the most common cardiac arrhythmia, atrial amyloidosis, and heart failure.