title: Defective lysosome maturation and Legionella pneumophila replication in Dictyostelium cells mutant for the Arf GAP ACAP-A.
abstract: Dictyostelium discoideum ACAP-A is an Arf GTPase-activating protein (GAP) involved in cytokinesis, cell migration and actin cytoskeleton dynamics. In mammalian cells, ACAP family members regulate endocytic protein trafficking. Here, we explored the function of ACAP-A in the endocytic pathway of D. discoideum. In the absence of ACAP-A, the efficiency of fusion between post-lysosomes and the plasma membrane was reduced, resulting in the accumulation of post-lysosomes. Moreover, internalized fluid-phase markers showed extended intracellular transit times, and the transfer kinetics of phagocyted particles from lysosomes to post-lysosomes was reduced. Neutralization of lysosomal pH, one essential step in lysosome maturation, was also delayed. Whereas expression of ACAP-A-GFP in acapA(-) cells restored normal particle transport kinetics, a mutant ACAP-A protein with no GAP activity towards the small GTPase ArfA failed to complement this defect. Taken together, these data support a role for ACAP-A in maturation of lysosomes into post-lysosomes through an ArfA-dependent mechanism. In addition, we reveal that ACAP-A is required for efficient intracellular growth of Legionella pneumophila, a pathogen known to subvert the endocytic host cell machinery for replication. This further emphasizes the role of ACAP-A in the endocytic pathway.
authors.affiliation: CIRI, International Centre for Infectiology Research, Legionella pathogenesis group, Université de Lyon, 69364 Lyon Cedex 07, France Inserm, U1111, 69342 Lyon Cedex 07, France Ecole Normale Supérieure de Lyon, 69007 Lyon, France Université Lyon 1, Centre International de Recherche en Infectiologie, 69364 Lyon Cedex 07, France CNRS, UMR5308, 69007 Lyon, France.
authors.forename: Nathalie
authors.initials: N
authors.lastname: Baïlo
authors.affiliation: Département de Physiologie Cellulaire et Métabolisme, Centre Médical Universitaire, 1 rue Michel Servet, 1211 Geneva 4, Switzerland.
authors.forename: Pierre
authors.initials: P
authors.lastname: Cosson
authors.affiliation: Institut de Biologie Intégrative et des Systèmes, Université Laval, Québec, QC G1V 0A6, Canada Département de Biochimie, de Microbiologie et de Bio-informatique, Université Laval, Québec, G1V 0A6, Canada Centre de Recherche de L'institut Universitaire de Cardiologie et de Pneumologie de Québec, Québec, QC G1V 4G5, Canada.
authors.forename: Steve J
authors.initials: SJ
authors.lastname: Charette
authors.affiliation: Institut de Biologie Intégrative et des Systèmes, Université Laval, Québec, QC G1V 0A6, Canada Département de Biochimie, de Microbiologie et de Bio-informatique, Université Laval, Québec, G1V 0A6, Canada Centre de Recherche de L'institut Universitaire de Cardiologie et de Pneumologie de Québec, Québec, QC G1V 4G5, Canada.
authors.forename: Valérie E
authors.initials: VE
authors.lastname: Paquet
authors.affiliation: CIRI, International Centre for Infectiology Research, Legionella pathogenesis group, Université de Lyon, 69364 Lyon Cedex 07, France Inserm, U1111, 69342 Lyon Cedex 07, France Ecole Normale Supérieure de Lyon, 69007 Lyon, France Université Lyon 1, Centre International de Recherche en Infectiologie, 69364 Lyon Cedex 07, France CNRS, UMR5308, 69007 Lyon, France.
authors.forename: Patricia
authors.initials: P
authors.lastname: Doublet
authors.affiliation: Laboratoire de Dynamique des Interactions Membranaires Normales et Pathologiques, Universités de Montpellier II et I, CNRS, UMR 5235, Place Eugène Bataillon, 34095 Montpellier Cedex 05, France francois.letourneur@univ-montp2.fr.
authors.forename: François
authors.initials: F
authors.lastname: Letourneur
mesh_terms: D004023:Dictyostelium / Q000378:metabolism* / Q000382:microbiology*; D054884:Host-Pathogen Interactions; D016952:Legionella pneumophila / Q000502:physiology*; D008247:Lysosomes / Q000378:metabolism*
keywords: Arf GAP; D. discoideum; Host-pathogen interaction; Legionella pneumophila; Lysosome; Membrane trafficking