Evidence for early endosome-like fusion of recently endocytosed synaptic vesicles.

Early endosomes are well-established acceptor compartments of endocytic vesicles in many cell types. Little evidence of their existence or function has been obtained in synapses, and it is generally believed that synaptic vesicles recycle without passing through an endosomal intermediate. We show here that the early endosomal SNARE proteins are enriched in synaptic vesicles.

Homotypic fusion of early endosomes: SNAREs do not determine fusion specificity.

Membrane fusion in the secretory pathway is mediated by soluble N-ethylmaleimide-sensitive factor attachment receptor (SNARE) proteins. Different fusion steps are thought to be effected by independent sets of SNAREs, but it is unclear whether specificity is determined by an intrinsic specificity of SNARE pairing or by upstream factors. Using a newly developed microscopy-based assay, we have investigated the SNARE specificity of homotypic early endosomal fusion.