title: Phosphoinositide binding by the SNX27 FERM domain regulates  its localization at the immune synapse of activated T-cells.
abstract: Sorting nexin 27 (SNX27) controls the endosomal-to-cell-surface recycling of diverse transmembrane protein cargos. Crucial to this function is the recruitment of SNX27 to endosomes which is mediated by the binding of phosphatidylinositol-3-phosphate (PtdIns3P) by its phox homology (PX) domain. In T-cells, SNX27 localizes to the immunological synapse in an activation-dependent manner, but the molecular mechanisms underlying SNX27 translocation remain to be clarified. Here, we examined the phosphoinositide-lipid-binding capabilities of full-length SNX27, and discovered a new PtdInsP-binding site within the C-terminal 4.1, ezrin, radixin, moesin (FERM) domain. This binding site showed a clear preference for bi- and tri-phosphorylated phophoinositides, and the interaction was confirmed through biophysical, mutagenesis and modeling approaches. At the immunological synapse of activated T-cells, cell signaling regulates phosphoinositide dynamics, and we find that perturbing phosphoinositide binding by the SNX27 FERM domain alters the SNX27 distribution in both endosomal recycling compartments and PtdIns(3,4,5)P3-enriched domains of the plasma membrane during synapse formation. Our results suggest that SNX27 undergoes dynamic partitioning between different membrane domains during immunological synapse assembly, and underscore the contribution of unique lipid interactions for SNX27 orchestration of cargo trafficking.
authors.forename: Rajesh
authors.initials: R
authors.lastname: Ghai
authors.forename: Maria
authors.initials: M
authors.lastname: Tello-Lafoz
authors.forename: Suzanne J
authors.initials: SJ
authors.lastname: Norwood
authors.forename: Zhe
authors.initials: Z
authors.lastname: Yang
authors.forename: Thomas
authors.initials: T
authors.lastname: Clairfeuille
authors.forename: Rohan D
authors.initials: RD
authors.lastname: Teasdale
authors.forename: Isabel
authors.initials: I
authors.lastname: Mérida
authors.forename: Brett M
authors.initials: BM
authors.lastname: Collins
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D045744:Cell Line, Tumor; D002462:Cell Membrane / Q000378:metabolism; D011992:Endosomes / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D054992:Immunological Synapses / Q000378:metabolism*; D019169:Jurkat Cells; D008213:Lymphocyte Activation / Q000276:immunology*; D051379:Mice; D018129:Phosphatidylinositol Phosphates / Q000378:metabolism*; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D021381:Protein Transport; D016415:Sequence Alignment; D015398:Signal Transduction; D058305:Sorting Nexins / Q000378:metabolism*; D013601:T-Lymphocytes / Q000276:immunology*
chemical_list: D018129:Phosphatidylinositol Phosphates; C522885:SNX27 protein, human; D058305:Sorting Nexins; C055525:phosphatidylinositol 3-phosphate