Article

The PX-BAR membrane-remodeling unit of sorting nexin 9.

Department of Physical Biochemistry, Max-Planck-Institute for Molecular Physiology, Dortmund, Germany.
The EMBO Journal (Impact Factor: 10.75). 12/2007; 26(22):4788-800. DOI: 10.1038/sj.emboj.7601889
Source: PubMed

ABSTRACT Sorting nexins (SNXs) form a family of proteins known to interact with components in the endosomal system and to regulate various steps of vesicle transport. Sorting nexin 9 (SNX9) is involved in the late stages of clathrin-mediated endocytosis in non-neuronal cells, where together with the GTPase dynamin, it participates in the formation and scission of the vesicle neck. We report here crystal structures of the functional membrane-remodeling unit of SNX9 and show that it efficiently tubulates lipid membranes in vivo and in vitro. Elucidation of the protein superdomain structure, together with mutational analysis and biochemical and cell biological experiments, demonstrated how the SNX9 PX and BAR domains work in concert in targeting and tubulation of phosphoinositide-containing membranes. The study provides insights into the SNX9-induced membrane modulation mechanism.

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    • "As CCPs mature, BAR domain proteins of increasing curvature are recruited. These include FBP17, with a curvature preference for a membrane sphere of 70 nm in diameter (Shimada et al., 2007), substantially larger than FCHo and SNX9, which can adopt two different conformations that yield different membrane curvatures (Pylypenko et al., 2007), possibly facilitating constriction (Posor et al., 2013). Finally, amphiphysin and endophilin, N-BAR proteins with a preference for highly bent membranes of about 25–30 nm in diameter, are recruited (Gallop et al., 2006; Peter et al., 2004). "
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    ABSTRACT: Biological membranes undergo constant remodeling by membrane fission and fusion to change their shape and to exchange material between subcellular compartments. During clathrin-mediated endocytosis, the dynamic assembly and disassembly of protein scaffolds comprising members of the bin-amphiphysin-rvs (BAR) domain protein superfamily constrain the membrane into distinct shapes as the pathway progresses toward fission by the GTPase dynamin. In this Review, we discuss how BAR domain protein assembly and disassembly are controlled in space and time and which structural and biochemical features allow the tight regulation of their shape and function to enable dynamin-mediated membrane fission.
    Cell 02/2014; 156(5):882-892. DOI:10.1016/j.cell.2014.02.017 · 33.12 Impact Factor
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    • "Overall, these data established that all SNX-BARs contain AHs that are functionally required for the generation of liposome tubules in vitro and in vivo. Hence, the BAR domains present in most of the SNXs can be functionally reclassified as being N-BAR domains, with SNX9, SNX18 and SNX33 being considered 'N-BAR domain-like' as the AH lies N-terminally to the PX domain (Peter et al, 2004; Gallop et al, 2006; Pylypenko et al, 2007). "
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    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.
    The EMBO Journal 10/2012; 31(23). DOI:10.1038/emboj.2012.283 · 10.75 Impact Factor
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    • "(A)Structure of human sorting nexin 9 (PDB ID: 2RAI) (Pylypenko et al., 2007). Two SNX9 monomers are shown, coloured orange and khaki. "
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    ABSTRACT: Intracellular trafficking and protein sorting are mediated by various protein complexes, with the retromer complex being primarily involved in retrograde traffic from the endosome or lysosome to the Golgi complex. Here, comparative genomics, cell biology and phylogenetics were used to probe the early evolution of retromer and its function. Retromer subunits Vps26, Vps29 and Vps35 are near universal, and, by inference, the complex was an ancient feature of eukaryotic cells. Surprisingly, we found DSCR3, a Vps26 paralogue in humans associated with Down's syndrome, in at least four eukaryotic supergroups, implying a more ancient origin than previously suspected. By contrast, retromer cargo proteins showed considerable interlineage variability, with lineage-specific and broadly conserved examples found. Vps10 trafficking probably represents an ancestral role for the complex. Vps5, the BAR-domain-containing membrane-deformation subunit, was found in diverse eukaryotes, including in the divergent eukaryote Trypanosoma brucei, where it is the first example of a BAR-domain protein. To determine functional conservation, an initial characterisation of retromer was performed in T. brucei; the endosomal localisation and its role in endosomal targeting are conserved. Therefore retromer is identified as a further feature of the sophisticated intracellular trafficking machinery of the last eukaryotic common ancestor, with BAR domains representing a possible third independent mechanism of membrane-deformation arising in early eukaryotes.
    Journal of Cell Science 05/2011; 124(Pt 9):1496-509. DOI:10.1242/jcs.081596 · 5.33 Impact Factor