Abstract
Mycobacterium tuberculosis (Mtb) kills infected macrophages by inhibiting apoptosis and promoting necrosis. The tuberculosis necrotizing toxin (TNT) is a secreted nicotinamide adenine dinucleotide (NAD+) glycohydrolase that induces necrosis in infected macrophages. Here, we show that NAD+ depletion by TNT activates RIPK3 and MLKL, key mediators of necroptosis. Notably, Mtb bypasses the canonical necroptosis pathway since neither TNF-α nor RIPK1 are required for macrophage death. Macrophage necroptosis is associated with depolarized mitochondria and impaired ATP synthesis, known hallmarks of Mtb-induced cell death. These results identify TNT as the main trigger of necroptosis in Mtb-infected macrophages. Surprisingly, NAD+ depletion itself was sufficient to trigger necroptosis in a RIPK3- and MLKL-dependent manner by inhibiting the NAD+ salvage pathway in THP-1 cells or by TNT expression in Jurkat T cells. These findings suggest avenues for host-directed therapies to treat tuberculosis and other infectious and age-related diseases in which NAD+ deficiency is a pathological factor.
Original language | English (US) |
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Pages (from-to) | 429-440 |
Number of pages | 12 |
Journal | Cell Reports |
Volume | 24 |
Issue number | 2 |
DOIs | |
State | Published - Jul 10 2018 |
Keywords
- MLKL
- NAD
- RIPK3
- TNT
- cell death
- mitochondria
- necroptosis
- toxin
- tuberculosis
ASJC Scopus subject areas
- Biochemistry, Genetics and Molecular Biology(all)