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Analyses of ESX-1 mediated inflammasome activation and cell death in mycobacterial infection

Alamiri, Feiruz (2015) MOBN01 20142
Degree Projects in Molecular Biology
Popular Abstract
Mycobacterium tuberculosis- invades to kill

Tuberculosis is a leading cause of death globally. The causative agent, Mycobacterium tuberculosis, resides primarily in so-called macrophages, a type of immune cell that normally serves to kill invading bacteria. The mycobacterial ESX-1 type VII secretion system is critical for ability of the bacterium to survive and grow in these cells. Moreover, ESX-1 is known to induce secretion of proinflammatory cytokines, including IL-1ß, as well as cell death to infected cells. Because these functions may have important roles during infection, this project aimed to gain insight into mechanistic basis for ESX-1-induced IL-1 ß secretion and cell death, respectively.

To study these processes we... (More)
Mycobacterium tuberculosis- invades to kill

Tuberculosis is a leading cause of death globally. The causative agent, Mycobacterium tuberculosis, resides primarily in so-called macrophages, a type of immune cell that normally serves to kill invading bacteria. The mycobacterial ESX-1 type VII secretion system is critical for ability of the bacterium to survive and grow in these cells. Moreover, ESX-1 is known to induce secretion of proinflammatory cytokines, including IL-1ß, as well as cell death to infected cells. Because these functions may have important roles during infection, this project aimed to gain insight into mechanistic basis for ESX-1-induced IL-1 ß secretion and cell death, respectively.

To study these processes we employed genetically modified macrophages and Mycobacterium marinum (Mm) – a close genetic relative of M. tuberculosis – that were analyzed in experimental infections in vitro. The extent of IL-1 ß secretion and cell death in infected macrophages was determined by measuring the amount of a cell death marker (the protein lactate dehydrogenase, LDH) and IL-1β in the culture medium.

ESX-1 dependent IL-1β secretion
Mm infection of macrophages lacking key components of the inflammasome system (responsible for secretion of IL-1 ß) revealed a significant ESX-1 dependent IL-1β secretion via the inflammasome proteins Caspase-1 and ASC. As has not been pointed out before, Caspase-11 was shown not to be involved in this ESX-1 regulated secretion.

CYPD-dependent cell death
CYPD dependent cell death by ESX-1
The Cyclophillin D (CYPD) protein is involved in a specific type of cell death called CYPD-dependent necrosis. This cell death is characterized by CYPD regulated pore formation in the outer mitochondrion layer (the cellular energy providing machinery) resulting in loss of cell balance, cellular swelling and burst.


Treatment of macrophages with titrated amounts of CYPD inhibitor (Cyclosporin A, CsA) resulted in a dose-dependent inhibition of ESX-1-mediated cell death. These results indicate that ESX-1 induce cell death via CYPD-dependent processes, and imply a previously unrecognized functional interaction between ESX-1 and the host cell mitochondria.

Advisor: Fredric Carlsson
Degree project 45 credits in microbial immunology 2015
Department of immunology, Lund University (Less)
Please use this url to cite or link to this publication:
author
Alamiri, Feiruz
supervisor
organization
course
MOBN01 20142
year
type
H2 - Master's Degree (Two Years)
subject
language
English
id
7363808
date added to LUP
2015-06-17 10:12:00
date last changed
2015-06-18 14:04:28
@misc{7363808,
  author       = {Alamiri, Feiruz},
  language     = {eng},
  note         = {Student Paper},
  title        = {Analyses of ESX-1 mediated inflammasome activation and cell death in mycobacterial infection},
  year         = {2015},
}