title: DDX3 DEAD-box RNA helicase plays a central role in mitochondrial protein quality control in Leishmania.
abstract: DDX3 is a highly conserved member of ATP-dependent DEAD-box RNA helicases with multiple functions in RNA metabolism and cellular signaling. Here, we describe a novel function for DDX3 in regulating the mitochondrial stress response in the parasitic protozoan Leishmania. We show that genetic inactivation of DDX3 leads to the accumulation of mitochondrial reactive oxygen species (ROS) associated with a defect in hydrogen peroxide detoxification. Upon stress, ROS production is greatly enhanced, causing mitochondrial membrane potential loss, mitochondrial fragmentation, and cell death. Importantly, this phenotype is exacerbated upon oxidative stress in parasites forced to use the mitochondrial oxidative respiratory machinery. Furthermore, we show that in the absence of DDX3, levels of major components of the unfolded protein response as well as of polyubiquitinated proteins increase in the parasite, particularly in the mitochondrion, as an indicator of mitochondrial protein damage. Consistent with these findings, immunoprecipitation and mass-spectrometry studies revealed potential interactions of DDX3 with key components of the cellular stress response, particularly the antioxidant response, the unfolded protein response, and the AAA-ATPase p97/VCP/Cdc48, which is essential in mitochondrial protein quality control by driving proteosomal degradation of polyubiquitinated proteins. Complementation studies using DDX3 deletion mutants lacking conserved motifs within the helicase core support that binding of DDX3 to ATP is essential for DDX3's function in mitochondrial proteostasis. As a result of the inability of DDX3-depleted Leishmania to recover from ROS damage and to survive various stresses in the host macrophage, parasite intracellular development was impaired. Collectively, these observations support a central role for the Leishmania DDX3 homolog in preventing ROS-mediated damage and in maintaining mitochondrial protein quality control.
authors.affiliation: Research Center in Infectious Diseases, CHU de Quebec Research Center-University Laval and Department of Microbiology, Infectious Disease and Immunology, Faculty of Medicine, University Laval, Quebec, QC, Canada.
authors.forename: Prasad Kottayil
authors.initials: PK
authors.lastname: Padmanabhan
authors.affiliation: Research Center in Infectious Diseases, CHU de Quebec Research Center-University Laval and Department of Microbiology, Infectious Disease and Immunology, Faculty of Medicine, University Laval, Quebec, QC, Canada.
authors.forename: Ouafa
authors.initials: O
authors.lastname: Zghidi-Abouzid
authors.affiliation: Department of Zoology, Kumaun University, Almora, Uttarakhand, India.
authors.forename: Mukesh
authors.initials: M
authors.lastname: Samant
authors.affiliation: Research Center in Infectious Diseases, CHU de Quebec Research Center-University Laval and Department of Microbiology, Infectious Disease and Immunology, Faculty of Medicine, University Laval, Quebec, QC, Canada.
authors.forename: Carole
authors.initials: C
authors.lastname: Dumas
authors.affiliation: Research Center in Infectious Diseases, CHU de Quebec Research Center-University Laval and Department of Microbiology, Infectious Disease and Immunology, Faculty of Medicine, University Laval, Quebec, QC, Canada.
authors.forename: Bruno Guedes
authors.initials: BG
authors.lastname: Aguiar
authors.affiliation: Research Center in Infectious Diseases, CHU de Quebec Research Center-University Laval and Department of Microbiology, Infectious Disease and Immunology, Faculty of Medicine, University Laval, Quebec, QC, Canada.|CNRS FR3636, Université Paris Descartes, Paris, France.
authors.forename: Jerome
authors.initials: J
authors.lastname: Estaquier
authors.affiliation: Research Center in Infectious Diseases, CHU de Quebec Research Center-University Laval and Department of Microbiology, Infectious Disease and Immunology, Faculty of Medicine, University Laval, Quebec, QC, Canada.
authors.forename: Barbara
authors.initials: B
authors.lastname: Papadopoulou
mesh_terms: D016923:Cell Death; D002454:Cell Differentiation; D053487:DEAD-box RNA Helicases / Q000378:metabolism*; D006861:Hydrogen Peroxide / Q000378:metabolism; D007891:Leishmania / Q000166:cytology* / Q000201:enzymology*; D053078:Membrane Potential, Mitochondrial; D024101:Mitochondrial Proteins / Q000378:metabolism*; D018384:Oxidative Stress; D025821:Polyubiquitin / Q000378:metabolism; D011485:Protein Binding; D015800:Protozoan Proteins / Q000378:metabolism*; D013312:Stress, Physiological; D054875:Ubiquitination; D056811:Unfolded Protein Response
chemical_list: D024101:Mitochondrial Proteins; D015800:Protozoan Proteins; D025821:Polyubiquitin; D006861:Hydrogen Peroxide; D053487:DEAD-box RNA Helicases