title: Molecular basis for SNX-BAR-mediated assembly of distinct endosomal sorting tubules.
abstract: Sorting nexins (SNXs) are regulators of endosomal sorting. For the SNX-BAR subgroup, a Bin/Amphiphysin/Rvs (BAR) domain is vital for formation/stabilization of tubular subdomains that mediate cargo recycling. Here, by analysing the in vitro membrane remodelling properties of all 12 human SNX-BARs, we report that some, but not all, can elicit the formation of tubules with diameters that resemble sorting tubules observed in cells. We reveal that SNX-BARs display a restricted pattern of BAR domain-mediated dimerization, and by resolving a 2.8 Å structure of a SNX1-BAR domain homodimer, establish that dimerization is achieved in part through neutralization of charged residues in the hydrophobic BAR-dimerization interface. Membrane remodelling also requires functional amphipathic helices, predicted to be present in all SNX-BARs, and the formation of high order SNX-BAR oligomers through selective 'tip-loop' interactions. Overall, the restricted and selective nature of these interactions provide a molecular explanation for how distinct SNX-BAR-decorated tubules are nucleated from the same endosomal vacuole, as observed in living cells. Our data provide insight into the molecular mechanism that generates and organizes the tubular endosomal network.
authors.affiliation: The Henry Wellcome Integrated Signalling Laboratories, School of Biochemistry, University of Bristol, Bristol, UK.
authors.forename: Jan R T
authors.initials: JR
authors.lastname: van Weering
authors.forename: Richard B
authors.initials: RB
authors.lastname: Sessions
authors.forename: Colin J
authors.initials: CJ
authors.lastname: Traer
authors.forename: Daniel P
authors.initials: DP
authors.lastname: Kloer
authors.forename: Vikram K
authors.initials: VK
authors.lastname: Bhatia
authors.forename: Dimitrios
authors.initials: D
authors.lastname: Stamou
authors.forename: Sven R
authors.initials: SR
authors.lastname: Carlsson
authors.forename: James H
authors.initials: JH
authors.lastname: Hurley
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Cullen
mesh_terms: D001483:Base Sequence; D019295:Computational Biology / Q000379:methods; D018360:Crystallography, X-Ray / Q000379:methods; D019281:Dimerization; D011992:Endosomes / Q000378:metabolism*; D057809:HEK293 Cells; D006367:HeLa Cells; D006801:Humans; D008954:Models, Biological; D008969:Molecular Sequence Data; D010957:Plasmids / Q000378:metabolism; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D021381:Protein Transport; D011994:Recombinant Proteins / Q000737:chemistry; D058305:Sorting Nexins / Q000378:metabolism*; D033921:Vesicular Transport Proteins / Q000378:metabolism
chemical_list: D011994:Recombinant Proteins; D058305:Sorting Nexins; C419573:VPS35 protein, human; D033921:Vesicular Transport Proteins