Endocytosis: Kiss and Run

Kiss-and-run refers to a prevailing hypothesis on the way in which secretory vesicle fusion and retrieval are coupled. According to the kiss-and-run hypothesis, following fusion with the plasma membrane secretory vesicles retain their curvature and release chemical substances through a restricted fusion pore. During this process, proteins originally resident within the vesicle membrane do not laterally diffuse onto the plasma membrane, thus allowing vesicles to preserve their identity during endocytosis. In this way, vesicles can be rapidly retrieved following fusion in a form of endocytosis that does not require vesicle reassembly. A key aspect of this model is the potential for postfusion regulation of chemical substance diffusion from the vesicle lumen through regulation of fusion pore opening duration and diameter. Kiss-and-run-type exocytosis-endocytosis coupling has been observed in multiple secretory systems that include mast cells, adrenal chromaffin cells, and pancreatic zymogen granules; however, the prevalence of this pathway for synaptic vesicle fusion and neurotransmitter release is a matter of intense debate.