title: Size-dependent mechanism of cargo sorting during lysosome-phagosome fusion is controlled by Rab34.
abstract: Phagosome maturation is an essential part of the innate and adaptive immune response. Although it is well established that several Ras-related proteins in brain (Rab) proteins become associated to phagosomes, little is known about how these phagosomal Rab proteins influence phagosome maturation. Here, we show a specific role for Rab34 and mammalian uncoordinated 13-2 (Munc13-2) in phagolysosome biogenesis and cargo delivery. Rab34 knockdown impaired the fusion of phagosomes with late endosomes/lysosomes and high levels of active Rab34 promoted this process. We demonstrate that Rab34 enhances phagosome maturation independently of Rab7 and coordinates phagolysosome biogenesis through size-selective transfer of late endosomal/lysosomal cargo into phagosomes. More importantly, we show that Rab34 mediates phagosome maturation through the recruitment of the protein Munc13-2. Finally, we report that the alternative maturation pathway controlled by Rab34 is critical for mycobacterial killing because Rab34 silencing resulted in mycobacterial survival, and Rab34 expression led to mycobacterial killing. Altogether, our studies uncover Rab34/Munc13-2 as a critical part of an alternative Rab7-independent phagosome maturation machinery and lysosome-mediated killing of mycobacteria.
authors.affiliation: Research Group Phagosome Biology,  Helmholtz Centre for Infection Research, 38124 Braunschweig,  Germany.
authors.forename: Bahram
authors.initials: B
authors.lastname: Kasmapour
authors.forename: Achim
authors.initials: A
authors.lastname: Gronow
authors.forename: Christopher K E
authors.initials: CK
authors.lastname: Bleck
authors.forename: Wanjin
authors.initials: W
authors.lastname: Hong
authors.forename: Maximiliano Gabriel
authors.initials: MG
authors.lastname: Gutierrez
mesh_terms: D000818:Animals; D001483:Base Sequence; D002460:Cell Line; D055785:Gene Knockdown Techniques; D047908:Intracellular Signaling Peptides and Proteins / Q000502:physiology; D008247:Lysosomes / Q000502:physiology*; D008264:Macrophages / Q000382:microbiology / Q000502:physiology; D008561:Membrane Fusion / Q000502:physiology; D051379:Mice; D008954:Models, Biological; D008970:Molecular Weight; D009154:Mutation; D009163:Mycobacterium bovis / Q000472:pathogenicity; D009419:Nerve Tissue Proteins / Q000502:physiology; D010588:Phagosomes / Q000382:microbiology / Q000502:physiology*; D034741:RNA, Small Interfering / Q000235:genetics; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D020691:rab GTP-Binding Proteins / Q000172:deficiency / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D000090802:rab7 GTP-Binding Proteins
chemical_list: D047908:Intracellular Signaling Peptides and Proteins; D009419:Nerve Tissue Proteins; D034741:RNA, Small Interfering; D011993:Recombinant Fusion Proteins; C485549:Unc13b protein, mouse; D000090802:rab7 GTP-Binding Proteins; C000716465:rab7 GTP-binding proteins, mouse; C475889:Rab34 protein, mouse; D020691:rab GTP-Binding Proteins