A role for adaptor protein-3 complex in the organization of the endocytic pathway in Dictyostelium.
Dictyostelium discoideum cells continuously internalize extracellular material, which accumulates in well-characterized endocytic vacuoles. In this study, we describe a new endocytic compartment identified by the presence of a specific marker, the p25 protein. This compartment presents features reminiscent of mammalian recycling endosomes: it is localized in the pericentrosomal region but distinct from the Golgi apparatus. It specifically contains surface proteins that are continuously endocytosed but rapidly recycled to the cell surface and thus absent from maturing endocytic compartments. We evaluated the importance of each clathrin-associated adaptor complex in establishing a compartmentalized endocytic system by studying the phenotype of the corresponding mutants. In knockout cells for mu3, a subunit of the AP-3 clathrin-associated complex, membrane proteins normally restricted to p25-positive endosomes were mislocalized to late endocytic compartments. Our results suggest that AP-3 plays an essential role in the compartmentalization of the endocytic pathway in Dictyostelium.
Charette
Steve J
SJ
Université de Genève, Centre Médical Universitaire, Département de Physiologie Cellulaire et Métabolisme, 1 rue Michel Servet, CH-1211 Genève 4, Switzerland. steve.charette@medecine.unige.ch
Mercanti
Valentina
V
Letourneur
François
F
Bennett
Nelly
N
Cosson
Pierre
P
D033963:Adaptor Protein Complex 3 / Q000502:physiology*; D033983:Adaptor Protein Complex mu Subunits / Q000172:deficiency / Q000235:genetics; D033942:Adaptor Proteins, Vesicular Transport / Q000235:genetics; D000818:Animals; D015815:Cell Adhesion Molecules / Q000235:genetics / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism; D004023:Dictyostelium / Q000235:genetics / Q000502:physiology*; D004705:Endocytosis / Q000502:physiology*; D011992:Endosomes / Q000378:metabolism; D017353:Gene Deletion; D008565:Membrane Proteins / Q000276:immunology / Q000378:metabolism; D008954:Models, Biological; D021381:Protein Transport / Q000502:physiology; D015800:Protozoan Proteins / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D025262:Vacuolar Proton-Translocating ATPases / Q000378:metabolism
D033963:Adaptor Protein Complex 3; D033983:Adaptor Protein Complex mu Subunits; D033942:Adaptor Proteins, Vesicular Transport; D015815:Cell Adhesion Molecules; D008565:Membrane Proteins; D015800:Protozoan Proteins; C052291:cell cohesion molecule, Dictyostelium; D025262:Vacuolar Proton-Translocating ATPases