The homotypic fusion and protein sorting (HOPS) tethering complex of the yeast vacuole is involved in multiple fusion reactions. We demonstrate that HOPS has two binding sites for SNAREs and that binding to the minimal SNARE complex is necessary for HOPS-stimulated fusion. Our data highlight the dual role of HOPS in Rab-mediated tethering and SNARE-driven fusion.
Membrane fusion within the endomembrane system follows a defined order of events: membrane tethering, mediated by Rabs and tethers, assembly of soluble N-ethylmaleimide-sensitive factor (NSF) attachment protein receptor (SNARE) complexes, and lipid bilayer mixing. Here we present evidence that the vacuolar HOPS tethering complex controls fusion through specific interactions with the vacuolar SNARE complex (consisting of Vam3, Vam7, Vti1, and Nyv1) and the N-terminal domains of Vam7 and Vam3. We show that homotypic fusion and protein sorting (HOPS) binds Vam7 via its subunits Vps16 and Vps18. In addition, we observed that Vps16, Vps18, and the Sec1/Munc18 protein Vps33, which is also part of the HOPS complex, bind to the Q-SNARE complex. In agreement with this observation, HOPS-stimulated fusion was inhibited if HOPS was preincubated with the minimal Q-SNARE complex. Importantly, artificial targeting of Vam7 without its PX domain to membranes rescued vacuole morphology in vivo, but resulted in a cytokinesis defect if the N-terminal domain of Vam3 was also removed. Our data thus support a model of HOPS-controlled membrane fusion by recognizing different elements of the SNARE complex.
See how this article has been cited at scite.ai
scite shows how a scientific paper has been cited by providing the context of the citation, a classification describing whether it supports, mentions, or contrasts the cited claim, and a label indicating in which section the citation was made.