Intracellular Vesicle Fusion Requires a Membrane-Destabilizing Peptide Located at the Juxtamembrane Region of the v-SNARE

Rathore, Shailendra S.; Liu, Yinghui; Yu, Haijia; Wan, Chun; Lee, MyeongSeon; Yin, Qian; Stowell, Michael H.B.; Shen, Jingshi

Although the cytoplasmic domains of SNAREs and their interactions with SM proteins have been well characterized, little has been known about protein-membrane interactions in the vesicle fusion reaction. In this work, we discovered that the membrane-embedded juxtamembrane motif of VAMP2 promotes membrane fusion by destabilizing the lipid bilayer. This membrane-destabilizing function is supported by three lines of evidence: (1) mutations or deletions of the lipid-binding residues in the juxtamembrane motif inhibit SNARE-Munc18-1-mediated membrane fusion; (2) the juxtamembrane motif is intrinsically capable of disrupting lipid bilayer structures; and (3) an unrelated membrane-disrupting peptide can replace the juxtamembrane motif in promoting membrane fusion. Because the juxtamembrane motif is conserved among v-SNAREs, we anticipate that its membranedestabilizing function is required for all vesicle fusion pathways. With the discovery of a membrane-destabilizing peptide in intracellular vesicle fusion, we suggest that biological membrane fusion pathways, although driven by disparate proteins, are governed by a common principle: assembly or refolding of membrane fusion proteins brings two lipid bilayers into close proximity, followed by local disruption of the bilayer structure by membrane-destabilizing peptides.