The process of HIV-1 particle production is a multi-step process directed by the viral structural protein Gag. As Gag is the only viral protein required to form virus-like particles, it presents a viable target for anti-viral therapeutics of which there are currently none. Although the functions of Gag during the particle assembly process have been well characterized, one of the least known parts of the assembly process is how Gag is targeted to the site of virus assembly. Two main virus assembly sites have been identified in cells that support HIV-1 replication: the plasma membrane or multivesicular bodies (MVBs). However the mechanism by which Gag is targeted to either of these sites remains unknown. The δ subunit of Adaptor Protein Complex 3 has previously been identified as a cellular co-factor for HIV-1 Gag and was reported to mediate Gag trafficking to MVBs, providing a mechanism for Gag targeting to this assembly site. Additionally, AP-3δ was reported to be required for HIV-1 production, suggesting that Gag to MVB targeting is also required for HIV-1 production. The work presented in this thesis further investigates the role of AP-3δ in Gag trafficking to MVBs and its role in HIV-1 production in previously unexplored host environments. Through the use of RNA interference-mediated depletion of AP-3δ, we determined that AP-3δ is dispensible for virus replication in infected HeLa cells, chronically infected HeLa-LAV cells and infected primary human monocyte-derived macrophages. We concomitantly disrupted AP-3 function by disrupting its association with membranes and observed no effect on virus production. Collectively, these results demonstrate that AP-3δ is not required for HIV-1 replication. However, AP-3δ was demonstrated to be required for Gag targeting to MVBs thus presenting a new model for the function of AP-3δ in the context of HIV-1 replication.

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L’autophagie est une voie catabolique durant laquelle des constituants cytoplasmiques sont engloutis dans des vésicules à double membrane nommées autophagosomes. Elle sert à éliminer les protéines mal repliées ou les agrégats protéiques, à détruire les organites défectueux comme les mitochondries, le réticulum endoplasmique et les peroxysomes mais aussi des pathogènes intracellulaires. Le matériel séquestré dans les autophagosomes est ensuite envoyé, pour dégradation, vers le lysosome. La dégradation du matériel séquestré génère des nucléotides, des acides aminés et des acides gras qui seront recyclés en vue de la synthèse de macromolécules et de la génération d’ATP.Dans cette étude nous explorons l’aspect cellulaire et fonctionnel de la voie de l’autophagie chez Caenorhabditis elegans. Nous montrons que le génome du nématode contient deux homologues du gène autophagique de levure Atg8. Ces homologues codent pour les protéines LGG-1 et LGG-2 qui sont des protéines des membranes des autophagosomes. Ces protéines agissent de façon synergique dans les processus physiologiques impliquant l’autophagie, en l’occurrence, la longévité et la formation des larves dauer.Nous montrons également que l’autophagie est impliquée dans le maintien de l’homéostasie cellulaire chez les mutants ESCRT. Les complexes ESCRT sont impliqués dans l’adressage des protéines ubiquitinées vers les corps multi vésiculaires pour les dégrader. Les mutants ESCRT se caractérisent par des altérations cellulaires et développementales. Nos résultats indiquent que l’inactivation des ESCRT cause une augmentation du flux autophagique. L’inactivation de l’autophagie dans ces mutants exacerbe les défauts cellulaires alors que son induction protège de la dégradation. / Macroautophgagy is a catabolic process involved in the clearance of cellular components in the lysosome when cells face starvation conditions. This eukaryotic process requires the formation of double membrane vesicles named autophagosomes. Autophagy is implicated in the elimination of misfolded proteins, protein aggregates and long-lived or damaged organelles such as mitochondria, endoplasmic reticulum and peroxysomes. It is alos required for the clearance of intracellular pathogens. The material enclosed inside autophagososmes in degraded in the lysosome: nucleotides, amino-acids and fatty-acids are generated and reused for neosynthesis of macromolecules and ATP.In the present study, we are exploring the cellular and functional aspects of the autophagic pathway in Caenorhabditis elegans. We show that the genome of the worm contain two homologues of the Yeast autophagic gene, Atg8. These homlogues encode for two proteins namely, LGG-1 and LGG-2, which localize to the autophagosomal membranes. We have shown that this two proteins act synergistically in dauer formation and longevity.We have also shown that autophagy play an important role in maintaining cell homeostasis in endosomal maturation mutans. These latter mutants show defects in the ESCRT coplexes (Endosomal Sorting Complex Required for Transport). ESCRT complexes are required the recycling of cell surface receptors and for the sorting of ubiquitinated prtoteins into the multivesicular bodies. Mutations in the ESCRTs cause cellular et developmental defects. In our study, we show that autophagy is induced in these mutants and play a beneficial role in correcting cellular defects.