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Updated: May 26, 2025
Single Cell Measurements of Vacuolar Rupture Caused by Intracellular Pathogens
Published on: June 12, 2013
Real-time visualization reveals Mycobacterium tuberculosis ESAT-6 disrupts phagosome-like compartment via
Debraj Koiri1, Mintu Nandi2, Abik Hameem P M1
1School of Biological Sciences, National Institute of Science Education & Research (NISER), Bhubaneshwar, India; Homi Bhabha National Institute (HBNI), Mumbai, India.
Abstract:
Mycobacterium tuberculosis (Mtb) evades host defense by hijacking and rupturing the phagosome. ESAT-6, a secreted virulence protein of Mtb, is known to be critical for phagosome rupture. However, the mechanism of ESAT-6-mediated disruption of the phagosomal membrane remains unknown. Using in vitro reconstitution, live-cell imaging, and numerical simulations, we discover that ESAT-6 polymerization forces remodeling and vesiculation of the phagosome-like compartment both in vitro and in vivo. Shallow insertion of ESAT-6 leads to tubular and bud-like deformations on the membrane facilitated by a reduction in membrane tension. Growing fibrils generate both radial and tangential forces causing local remodeling and shape transition of the membrane into buds. The ESAT-6-bound tensed membrane undergoes local changes in membrane curvature and lipid phase separation that assist the subsequent fission. Overall, the findings provide mechanistic insights into the long-standing question of phagosome disruption by Mtb for its escape.
Insights
Mycobacterium tuberculosis uses ESAT-6 protein to rupture phagosomes. ESAT-6 polymerization remodels the membrane, causing vesiculation and escape from host defenses.
Area of Science:
- Microbiology
- Cell Biology
- Biophysics
Background:
- Mycobacterium tuberculosis (Mtb) evades host immune responses by disrupting the phagosome, a key cellular compartment.
- The secreted virulence protein ESAT-6 is implicated in Mtb-induced phagosome rupture, but the underlying mechanism is unclear.
Purpose of the Study:
- To elucidate the molecular mechanism by which ESAT-6 disrupts the phagosomal membrane.
- To understand how ESAT-6 facilitates Mycobacterium tuberculosis escape from host cells.
Main Methods:
- In vitro reconstitution assays to study ESAT-6-membrane interactions.
- Live-cell imaging to visualize phagosome dynamics in real-time.
- Numerical simulations to model the physical forces involved in membrane disruption.
Main Results:
- ESAT-6 polymerization drives phagosome-like membrane remodeling and vesiculation.
- Shallow ESAT-6 insertion reduces membrane tension, inducing tubular and bud-like deformations.
- ESAT-6 fibrils generate forces that promote membrane shape transitions and fission.
Conclusions:
- ESAT-6 polymerization is a key driver of phagosome rupture by Mycobacterium tuberculosis.
- The study reveals the biophysical mechanisms of ESAT-6-mediated membrane disruption.
- Findings offer insights into bacterial pathogenesis and host-pathogen interactions.
