title: t-SNARE protein conformations patterned by the lipid microenvironment.
abstract: The spatial distribution of the target (t-)SNARE proteins (syntaxin and SNAP-25) on the plasma membrane has been extensively characterized. However, the protein conformations and interactions of the two t-SNAREs in situ remain poorly defined. By using super-resolution optical techniques and fluorescence lifetime imaging microscopy, we observed that within the t-SNARE clusters syntaxin and SNAP-25 molecules interact, forming two distinct conformations of the t-SNARE binary intermediate. These are spatially segregated on the plasma membrane with each cluster exhibiting predominantly one of the two conformations, representing the two- and three-helical forms previously observed in vitro. We sought to explain why these two t-SNARE intermediate conformations exist in spatially distinct clusters on the plasma membrane. By disrupting plasma membrane lipid order, we found that all of the t-SNARE clusters now adopted a single conformational state corresponding to the three helical t-SNARE intermediates. Together, our results define spatially distinct t-SNARE intermediate states on the plasma membrane and how the conformation adopted can be patterned by the underlying lipid environment.
authors.affiliation: Centre for Integrative Physiology, School of Informatics, University of Edinburgh, Edinburgh EH8 9XD, Scotland, United Kingdom.
authors.forename: Colin
authors.initials: C
authors.lastname: Rickman
authors.forename: Claire N
authors.initials: CN
authors.lastname: Medine
authors.forename: Alison R
authors.initials: AR
authors.lastname: Dun
authors.forename: David J
authors.initials: DJ
authors.lastname: Moulton
authors.forename: Ondrej
authors.initials: O
authors.lastname: Mandula
authors.forename: Nagaraj D
authors.initials: ND
authors.lastname: Halemani
authors.forename: Silvio O
authors.initials: SO
authors.lastname: Rizzoli
authors.forename: Luke H
authors.initials: LH
authors.lastname: Chamberlain
authors.forename: Rory R
authors.initials: RR
authors.lastname: Duncan
mesh_terms: D000818:Animals; D002462:Cell Membrane / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D008563:Membrane Lipids / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D016716:PC12 Cells; D020836:Protein Structure, Quaternary; D017433:Protein Structure, Secondary; D050765:Qa-SNARE Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D051381:Rats; D050825:Synaptosomal-Associated Protein 25 / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism
chemical_list: D008563:Membrane Lipids; D050765:Qa-SNARE Proteins; C494210:Snap25 protein, rat; D050825:Synaptosomal-Associated Protein 25