Snareeiwitten

SNARE eiwitten, or SNARE proteins, are a family of membrane proteins that mediate vesicle fusion in most eukaryotic cells. They bring the vesicle and target membranes into close apposition and provide the energy needed for lipid bilayer fusion.

SNAREs are typically categorized as v-SNAREs, on vesicles, and t-SNAREs, on target membranes. In many cases the functional complex contains one R-SNARE and two or three Q-SNAREs. Classic examples include the R-SNARE synaptobrevin/VAMP and the Q-SNAREs syntaxin-1 and SNAP-25 on the plasma membrane, which assemble into a four-helix bundle that drives fusion.

Formation of the SNARE complex is tightly regulated. The four-helix bundle brings membranes together and overcomes repulsion. Regulation involves Rab GTPases, SM proteins such as Munc18, and factors like complexin. After fusion, the SNAREs are disassembled by the ATPase NSF with α-SNAP to recycle them.

SNARE proteins are essential for neurotransmitter release at synapses and for general secretory pathways, including hormone release and autophagic processes. They are conserved across eukaryotes, with organism-specific sets coordinating fusion events such as ER-to-Golgi transport, vacuolar fusion in yeast, and pollen tube growth in plants.

Disruption of SNARE function can have serious consequences. Botulinum and tetanus neurotoxins cleave SNAREs, blocking synaptic transmission. The SNARE hypothesis, proposed in the 1990s, helped establish the field of vesicle trafficking and was recognized with Nobel Prizes in 2013 to Thomas Südhof, James Rothman, and Randy Schekman.