title: Endosomal maturation by Rab conversion in Aspergillus nidulans is coupled to dynein-mediated basipetal movement.
abstract: We exploit the ease with which highly motile early endosomes are distinguished from static late endosomes in order to study Aspergillus nidulans endosomal traffic. RabS(Rab7) mediates homotypic fusion of late endosomes/vacuoles in a homotypic fusion- and vacuole protein sorting/Vps41-dependent manner. Progression across the endocytic pathway involves endosomal maturation because the end products of the pathway in the absence of RabS(Rab7) are minivacuoles that are competent in multivesicular body sorting and cargo degradation but retain early endosomal features, such as the ability to undergo long-distance movement and propensity to accumulate in the tip region if dynein function is impaired. Without RabS(Rab7), early endosomal Rab5s-RabA and RabB-reach minivacuoles, in agreement with the view that Rab7 homologues facilitate the release of Rab5 homologues from endosomes. RabS(Rab7) is recruited to membranes already at the stage of late endosomes still lacking vacuolar morphology, but the transition between early and late endosomes is sharp, as only in a minor proportion of examples are RabA/RabB and RabS(Rab7) detectable in the same-frequently the less motile-structures. This early-to-late endosome/vacuole transition is coupled to dynein-dependent movement away from the tip, resembling the periphery-to-center traffic of endosomes accompanying mammalian cell endosomal maturation. Genetic studies establish that endosomal maturation is essential, whereas homotypic vacuolar fusion is not.
authors.affiliation: Departamento de Medicina Molecular y Celular, Centro de Investigaciones Biológicas del Consejo Superior de Investigaciones Cientificas, 28040 Madrid, Spain.
authors.forename: Juan F
authors.initials: JF
authors.lastname: Abenza
authors.forename: Antonio
authors.initials: A
authors.lastname: Galindo
authors.forename: Mario
authors.initials: M
authors.lastname: Pinar
authors.forename: Areti
authors.initials: A
authors.lastname: Pantazopoulou
authors.forename: Vivian
authors.initials: V
authors.lastname: de los Ríos
authors.forename: Miguel A
authors.initials: MA
authors.lastname: Peñalva
mesh_terms: D001233:Aspergillus nidulans / Q000378:metabolism* / Q000502:physiology / Q000648:ultrastructure; D001692:Biological Transport; D004398:Dyneins / Q000378:metabolism*; D004705:Endocytosis; D011992:Endosomes / Q000378:metabolism* / Q000648:ultrastructure; D005656:Fungal Proteins / Q000378:metabolism*; D055786:Gene Knockout Techniques; D049452:Green Fluorescent Proteins / Q000378:metabolism; D025301:Hyphae / Q000254:growth & development / Q000378:metabolism; D007425:Intracellular Membranes / Q000378:metabolism; D008561:Membrane Fusion; D011485:Protein Binding; D059748:Proteolysis; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D050600:SNARE Proteins / Q000378:metabolism; D013172:Spores, Fungal / Q000254:growth & development / Q000378:metabolism; D059008:Time-Lapse Imaging; D014617:Vacuoles / Q000378:metabolism / Q000648:ultrastructure; D033921:Vesicular Transport Proteins / Q000378:metabolism; D020691:rab GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D005656:Fungal Proteins; D011993:Recombinant Fusion Proteins; D050600:SNARE Proteins; D033921:Vesicular Transport Proteins; D049452:Green Fluorescent Proteins; D004398:Dyneins; D020691:rab GTP-Binding Proteins