Mechanisms of peptide hormone secretion

According to the classical view, peptide hormones are stored in large dense-core vesicles that release all of their cargo rapidly and completely when they fuse with and flatten into the plasma membrane. However, recent imaging studies suggest that this view is too simple. Even after vesicles fuse with the plasma membrane, cells might control the rate of dispersal of vesicle cargo – either by modulating the properties of the fusion pore that connects the vesicle lumen to the extracellular solution or by storing cargo in states that disperse slowly in the extracellular space. Understanding these mechanisms is important, owing to the increasing prevalence of diseases, such as type 2 diabetes mellitus, which arise from insufficient secretion of peptide hormones.