Endocrinology

Biography

Biography: Robert Zorec

Abstract

Edocrine Hormone release engages regulated exocytosis, a multistage process involving the merger between the vesicle and the plasma membranes. This leads to the formation of a fusion pore, a channel, through which secretions are released from the vesicle lumen to the cell exterior. A stimulus may influence the pore by either dilating it completely (full-fusion exocytosis) or mediating a reversible closure (transient exocytosis). In neurons, these transitions are short-lived and not accessible for experimentation. However, in some endocrine and gliocrine cells, initial fusion pores may reopen several hundred times, indicating their stability. Moreover, these pores are too narrow to pass luminal molecules to the extracellular space, but their diameter can dilate upon stimulation. To explain the stability of the initial narrow fusion pores, anisotropic membrane constituents with non-axisymmetrical shape were proposed to accumulate in the fusion pore membrane. Although the nature of these is unclear, they may consist of lipids and proteins, including SNAREs, which may facilitate and regulate the pre- and post-fusion stages of exocytosis and the release of vesicle hormone cargo into the extracellular space.