title: SPE-39 family proteins interact with the HOPS complex and function in lysosomal delivery.
abstract: Yeast and animal homotypic fusion and vacuole protein sorting (HOPS) complexes contain conserved subunits, but HOPS-mediated traffic in animals might require additional proteins. Here, we demonstrate that SPE-39 homologues, which are found only in animals, are present in RAB5-, RAB7-, and RAB11-positive endosomes where they play a conserved role in lysosomal delivery and probably function via their interaction with the core HOPS complex. Although Caenorhabditis elegans spe-39 mutants were initially identified as having abnormal vesicular biogenesis during spermatogenesis, we show that these mutants also have disrupted processing of endocytosed proteins in oocytes and coelomocytes. C. elegans SPE-39 interacts in vitro with both VPS33A and VPS33B, whereas RNA interference of VPS33B causes spe-39-like spermatogenesis defects. The human SPE-39 orthologue C14orf133 also interacts with VPS33 homologues and both coimmunoprecipitates and cosediments with other HOPS subunits. SPE-39 knockdown in cultured human cells altered the morphology of syntaxin 7-, syntaxin 8-, and syntaxin 13-positive endosomes. These effects occurred concomitantly with delayed mannose 6-phosphate receptor-mediated cathepsin D delivery and degradation of internalized epidermal growth factor receptors. Our findings establish that SPE-39 proteins are a previously unrecognized regulator of lysosomal delivery and that C. elegans spermatogenesis is an experimental system useful for identifying conserved regulators of metazoan lysosomal biogenesis.
authors.affiliation: Graduate Program in Biochemistry, Cell, and Developmental Biology, Departments of *Biology and Cell Biology, and Department of Neurology, Center for Neurodegenerative Disease, Emory University, Atlanta, GA 30322.
authors.forename: Guang-dan
authors.initials: GD
authors.lastname: Zhu
authors.forename: Gloria
authors.initials: G
authors.lastname: Salazar
authors.forename: Stephanie A
authors.initials: SA
authors.lastname: Zlatic
authors.forename: Babar
authors.initials: B
authors.lastname: Fiza
authors.forename: Michele M
authors.initials: MM
authors.lastname: Doucette
authors.forename: Craig J
authors.initials: CJ
authors.lastname: Heilman
authors.forename: Allan I
authors.initials: AI
authors.lastname: Levey
authors.forename: Victor
authors.initials: V
authors.lastname: Faundez
authors.forename: Steven W
authors.initials: SW
authors.lastname: L'hernault
mesh_terms: D000818:Animals; D017173:Caenorhabditis elegans / Q000378:metabolism* / Q000648:ultrastructure; D029742:Caenorhabditis elegans Proteins / Q000378:metabolism*; D002352:Carrier Proteins / Q000378:metabolism*; D004705:Endocytosis; D011992:Endosomes / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D008247:Lysosomes / Q000378:metabolism*; D008297:Male; D051379:Mice; D046912:Multiprotein Complexes / Q000378:metabolism*; D011485:Protein Binding; D011499:Protein Processing, Post-Translational; D021381:Protein Transport; D034741:RNA, Small Interfering / Q000378:metabolism; D017527:Receptor, IGF Type 2 / Q000378:metabolism; D013090:Spermatocytes / Q000648:ultrastructure; D013091:Spermatogenesis; D033921:Vesicular Transport Proteins / Q000378:metabolism
chemical_list: D029742:Caenorhabditis elegans Proteins; D002352:Carrier Proteins; D046912:Multiprotein Complexes; D034741:RNA, Small Interfering; D017527:Receptor, IGF Type 2; C539710:Spe-39 protein, C elegans; C539711:VIPAS39 protein, human; C424440:VPS33A protein, human; C411584:VPS33B protein, human; D033921:Vesicular Transport Proteins