SNAREmediated

SNARE-mediated membrane fusion is the cellular process by which SNARE proteins drive the merger of lipid bilayers, such as a transport vesicle with its target membrane. The core event is the formation of a SNARE complex, a four-helix bundle assembled from a vesicle-associated v-SNARE and one or more target-membrane t-SNAREs. In vertebrate cells, a well-studied neuronal example involves the v-SNARE synaptobrevin/VAMP and the t-SNAREs syntaxin-1 and SNAP-25, though many organelles use related SNARE pairs with compatible interfaces.

The SNARE complex forms through progressive interactions that zipper from the distal (membrane-proximal) regions toward the fusion site, pulling the vesicle and target membranes into close contact and facilitating pore formation. The energy released during this zippering is thought to overcome barriers to lipid bilayer fusion, enabling exocytosis or other vesicular trafficking steps.

Fusion is tightly regulated by accessory proteins. Calcium influx is sensed by proteins such as synaptotagmin, which accelerates fusion in neurons and secretory cells. SM ( Sec1/Munc18-like) proteins, including Munc18-1, assist in SNARE complex assembly and vesicle priming. After fusion, the SNARE complex is disassembled by NSF (N-ethylmaleimide-sensitive factor) together with α-SNAP, allowing SNARE components to be recycled for subsequent rounds of fusion.

SNARE-mediated fusion occurs across diverse trafficking pathways, including neurotransmitter and hormone release, ER-to-Golgi transport, and endosome-lysosome fusion. Disruptions in SNARE regulation or expression are linked to various diseases, underscoring the essential role of SNARE-mediated fusion in cellular physiology.