Cellubrevin Alterations and Mycobacterium tuberculosis Phagosome Maturation Arrest

Abstract

The intracellular trafficking processes controlling phagosomal maturation remain to be fully delineated. Mycobacterium tuberculosis var. bovis BCG, an organism that causes phagosomal maturation arrest, has emerged as a tool for dissection of critical phagosome biogenesis events. In this work, we report that cellubrevin, a v-SNARE functioning in endosomal recycling and implicated in endosomal interactions with post-Golgi compartments, plays a role in phagosomal maturation and that it is altered on mycobacterial phagosomes. Both mycobacterial phagosomes, which undergo maturation arrest, and model phagosomes containing latex beads, which follow the normal pathway of maturation into phagolysosomes, acquired cellubrevin. However, the mycobacterial and model phagosomes differed, as a discrete proteolytic degradation of this SNARE was detected on mycobacterial phagosomes. The observed cellubrevin alteration on mycobacterial phagosomes was not a passive event secondary to a maturation arrest at another checkpoint of the phagosome maturation pathway, since pharmacological inhibitors of phagosomal/ endosomal pathways blocking phagosomal maturation did not cause cellubrevin degradation on model phagosomes. Cellubrevin status on phagosomes had consequences on phagosomal membrane and lumenal content trafficking, involving plasma membrane marker recycling and delivery of lysosomal enzymes. These results suggest that cellubrevin plays a role in phagosomal maturation and that it is a target for modification by mycobacteria or by infection-induced processes in the host cell.

Constrained Intracellular Survival ofMycobacterium tuberculosisin Human Dendritic Cells

“…The ATPase NSF, together with soluble NSF attachment protein, is required in a broad range of vesicular docking and fusion events (43), and NSF was recently shown on M. bovis BCG phagosomes in J774 M-like cells (24,32). Consistent with these results, the ATPase NSF was continuously retained on the phagosome membrane in Ms, but the mycobacterial vacuoles in DCs were deficient of this marker (Fig.…”

“…Thus, despite its limited fusogenicity towards organelles of the deep endocytic pathway, the mycobacterial phagosome appears to be very dynamic indeed. This feature correlates with the continuous presence of various fusion and docking factors, such as the ATPase N-ethylmaleimide-sensitive factor (NSF), onto the phagosomal membrane, whereas these factors are rapidly lost by phagolysosomes containing inert particles (24,32).…”

Cutting Edge: Mycobacterium tuberculosis Blocks Ca2+ Signaling and Phagosome Maturation in Human Macrophages Via Specific Inhibition of Sphingosine Kinase

“…Within the last decade, significant advances have been made in our understanding of Mtb-induced alterations in MP signal transduction pathways that may contribute to the organism's intracellular persistence. These include inhibition of phagosomal localization of the vacuolar H ϩ /ATPase that normally acidifies the phagolysosome (3), alterations of regulatory GTPases of the Rab family and its effector early endosomal Ag 1 (4,5), and modulation of the vesicular soluble N-ethylmaleimide attachment protein receptor cellubrevin (6). In these studies, comparisons between live and killed Mtb have provided valuable information and confirmed that inhibition of MP signaling is restricted to live bacilli.…”

Exclusion of synaptotagmin V at the phagocytic cup by Leishmania donovani lipophosphoglycan results in decreased promastigote internalization

“…Consistently, several SNAREs, including VAMP3, syntaxin 4 and syntaxin 13, are recruited to the nascent phagocytic cup to mediate the membrane fusion events involved in exocytosis (Bajno et al, 2000;Collins et al, 2002;Fratti et al, 2002;Murray et al, 2005). Similar to Syt V , intact lipid microdomains are required for the recruitment of syntaxin 4 and VAMP3 to phagosomes (Kay et al, 2006).…”