Autophagy Is a Defense Mechanism Inhibiting BCG and Mycobacterium tuberculosis Survival in Infected Macrophages

Authors:
Gutierrez MG, Master SS, Singh SB, Taylor GA, Colombo MI and Deretic V
In:
Source: Cell
Publication Date: (2004)
Issue: 119(6): 753-766
Research Area:
Immunotherapy / Hematology
Cells used in publication:
RAW 264.7
Species: mouse
Tissue Origin: blood
Platform:
Nucleofectorâ„¢ I/II/2b
Experiment
Cells from the mouse macrophage-like cell line RAW264.7 were nucleofected with several different expression plasmids coding for EGFP-fusions of wild-type and mutant LC3 (an elongation factor in autophagosome formation), coding for a GFP fusion of LRG-47 (a downstream effector of Interferon IFN-gamma), or coding for a FLAG-tagged Beclin-1.
Abstract
Mycobacterium tuberculosis is an intracellular pathogen persisting within phagosomes through interference with phagolysosome biogenesis. Here we show that stimulation of autophagic pathways in macrophages causes mycobacterial phagosomes to mature into phagolysosomes. Physiological induction of autophagy or its pharmacological stimulation by rapamycin resulted in mycobacterial phagosome colocalization with the autophagy effector LC3, an elongation factor in autophagosome formation. Autophagy stimulation increased phagosomal colocalization with Beclin-1, a subunit of the phosphatidylinositol 3-kinase hVPS34, necessary for autophagy and a target for mycobacterial phagosome maturation arrest. Induction of autophagy suppressed intracellular survival of mycobacteria. IFN-gamma induced autophagy in macrophages, and so did transfection with LRG-47, an effector of IFN-gamma required for antimycobacterial action. These findings demonstrate that autophagic pathways can overcome the trafficking block imposed by M. tuberculosis. Autophagy, which is a hormonally, developmentally, and, as shown here, immunologically regulated process, represents an underappreciated innate defense mechanism for control of intracellular pathogens.