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Browsing by Author "Ostrowski, M."

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  • Rab27a and Rab27b control different steps of the exosome secretion pathway
    Publication . Ostrowski, M.; Carmo, NB.; Krumeich, S.; Fanget, I.; Raposo, G.; Savina, A.; Moita, CF.; Schauer, K.; Hume, AN.; Freitas, RP.; Goud, B.; Benaroch, P.; Hachoen, N.; Fukuda, M.; Desnos, C.; Seabra, MC.; Darchen, F.; Amigorena, S.; Moita, LF.; Thery, C.
    Exosomes are secreted membrane vesicles that share structural and biochemical characteristics with intraluminal vesicles of multivesicular endosomes (MVEs). Exosomes could be involved in intercellular communication and in the pathogenesis of infectious and degenerative diseases. The molecular mechanisms of exosome biogenesis and secretion are, however, poorly understood. Using an RNA interference (RNAi) screen, we identified five Rab GTPases that promote exosome secretion in HeLa cells. Among these, Rab27a and Rab27b were found to function in MVE docking at the plasma membrane. The size of MVEs was strongly increased by Rab27a silencing, whereas MVEs were redistributed towards the perinuclear region upon Rab27b silencing. Thus, the two Rab27 isoforms have different roles in the exosomal pathway. In addition, silencing two known Rab27 effectors, Slp4 (also known as SYTL4, synaptotagmin-like 4) and Slac2b (also known as EXPH5, exophilin 5), inhibited exosome secretion and phenocopied silencing of Rab27a and Rab27b, respectively. Our results therefore strengthen the link between MVEs and exosomes, and introduce ways of manipulating exosome secretion in vivo.
    2010-01Journal article Open access Show more
  • Rab27a controls HIV-1 assembly by regulating plasma membrane levels of phosphatidylinositol 4,5-bisphosphate
    Publication . Gerber, P. P.; Cabrini, M.; Jancic, C.; Paoletti, L.; Banchio, C.; von Bilderling, C.; Sigaut, L.; Pietrasanta, L. I.; Duette, G.; Freed, E. O.; de Saint Basile, G.; Moita, C. F.; Moita, L. F.; Amigorena, S.; Benaroch, P.; Geffner, J.; Ostrowski, M.
    During the late stages of the HIV-1 replication cycle, the viral polyprotein Pr55(Gag) is recruited to the plasma membrane (PM), where it binds phosphatidylinositol 4,5-bisphosphate (PI(4,5)P2) and directs HIV-1 assembly. We show that Rab27a controls the trafficking of late endosomes carrying phosphatidylinositol 4-kinase type 2 α (PI4KIIα) toward the PM of CD4(+) T cells. Hence, Rab27a promotes high levels of PM phosphatidylinositol 4-phosphate and the localized production of PI(4,5)P2, therefore controlling Pr55(Gag) membrane association. Rab27a also controls PI(4,5)P2 levels at the virus-containing compartments of macrophages. By screening Rab27a effectors, we identified that Slp2a, Slp3, and Slac2b are required for the association of Pr55(Gag) with the PM and that Slp2a cooperates with Rab27a in the recruitment of PI4KIIα to the PM. We conclude that by directing the trafficking of PI4KIIα-positive endosomes toward the PM, Rab27a controls PI(4,5)P2 production and, consequently, HIV-1 replication.
    2015-05-11Journal article Open access Show more