Inhibition of the Plasma-Membrane-Associated Serine Protease Cathepsin G by Mycobacterium tuberculosis Rv3364c Suppresses Caspase-1 and Pyroptosis in Macrophages

Abstract

Tuberculosis is a disease associated with the infection of a great part of the world’s population and is responsible for the death of two to three million people annually. Mycobacterium tuberculosis infects macrophages and subverts its mechanisms of killing. The pathogen suppresses macrophage apoptosis by many different mechanisms. We describe that, upon uptake by macrophages, M. tuberculosis overexpresses an operon Rv3361c-Rv3365c and secretes Rv3364c. The Rv3365c knockout strain is deficient in apoptosis inhibition. The Rv3364c protein binds to the serine protease cathepsin G on the membrane, inhibiting its enzymatic activity and the downstream activation of caspase-1-dependent apoptosis. In summary, M. tuberculosis prevents macrophage pyroptosis by a novel mechanism involving cytoplasmic surveillance proteins.

The innate immune response in human tuberculosis

“…Mtb induces necrosis, a death modality defined by cell lysis, and inhibits apoptosis, a form of death that maintains an intact plasma membrane and that enables control of bacterial replication. Several Mtb proteins inhibit apoptosis in human cells such as the serine/threonine kinase PknE (Jayakumar et al ., 2008) and the Rv3364c protein (Danelishvili et al ., 2011). Moreover, the Mtb proteins SecA2 and NuoG suppress THP‐1 macrophage apoptosis (Hinchey et al ., 2007; Velmurugan et al ., 2007; Miller et al ., 2010).…”

Interaction of Mycobacterium tuberculosis with Host Cell Death Pathways

“…The consequence of this interaction is that there are lower levels of caspase 8 in cells infected with wild-type Mtb compared with a Rv3654c deletion mutant (Danelishvili et al 2010). The other antiapoptotic operon is Rv3361c-Rv3365c, which is implicated in the inhibition of cell death dependent on the inflammatory caspase 1 (Danelishvili et al 2011). After Mtb infection, Rv3364c enters the host cell cytosol and binds to and inactivates the host cell protease cathepsin G (Danelishvili et al 2011).…”

“…One report shows that this activation of NLRP3 leads to the induction of necroptosis (Wong and Jacobs 2011). The Mtb Rv3364c protein is an inhibitor of host cell cathepsin G and this inhibition led to less caspase 1-dependent pyroptosis (Danelishvili et al 2011). The ESX-5 system has also been implicated in the induction of host cell necrosis and inflammasome activation (Abdallah et al 2011).…”

“…The other antiapoptotic operon is Rv3361c-Rv3365c, which is implicated in the inhibition of cell death dependent on the inflammatory caspase 1 (Danelishvili et al 2011). After Mtb infection, Rv3364c enters the host cell cytosol and binds to and inactivates the host cell protease cathepsin G (Danelishvili et al 2011). How cathepsin G regulates caspase 1 activity is not known but it was hypothesized that the effect might be mediated via cathepsin G cleavage and activation of the protease activated receptor-4, which then can induce caspase 1 activation via a NOD (nucleotide-binding oligomerization domain)-dependent pathway (Danelishvili et al 2011) (for a detailed review, see Briken 2013).…”

The Environment of “Mycobacterium avium subsp. hominissuis” Microaggregates Induces Synthesis of Small Proteins Associated with Efficient Infection of Respiratory Epithelial Cells

“…To create an MBP-1 overexpression construct, the gene was amplified using FideliTaq PCR master mix (Affymetrix, Santa Clara, CA), and the PCR-generated fragment was fused to a red fluorescent protein (RFP) and cloned into Escherichia coli-Mycobacterium shuttle vector pMV261-5HRFP, encoding kanamycin resistance (27). The resulting plasmid was propagated in E. coli DH10B and then electroporated into Mycobacterium smegmatis mc 2 155.…”