Deciphering the role of PE_PGRS45 (Rv2615c) protein of Mycobacterium
tuberculosis in host macrophage apoptosis: Possible effector for
persistence
Abstract
Mycobacterium tuberculosis has co-evolved with its host to evade
and modulate host cellular processes. Few PE/PPE proteins of
Mycobacterium have been reported to modulate cell death pathways
and determine the infection outcome. This study investigates role of one
such uncharacterized protein PE_PGRS45/Rv2615c in host cell death and
immuno-modulation. In-silico analysis predicted similarity of
Rv2615c with APAF1-apoptosome and involvement in Cysteine-type
endo-peptidase activation during apoptosis. In-vitro experiments
with THP-1 macrophages confirmed the Caspase-dependent apoptosis
inducing potential of Rv2615c. Several PE_PGRS proteins have been
reported to be TLR-agonist. Docking showed preferential binding of
Rv2615c with TLR4 than TLR2. Up-regulation of
TLR4-HLA-DR-MyD88-NF-ƙB-TNF‐α in Rv2615c-stimulated THP-1 macrophages
was observed. To investigate the mechanism underpinning the apoptotic
function, a thorough sequence scan of Rv2615c revealed the presence of
eukaryotic CARD-like domain in it. In-silico studies showed
binding affinity of Rv2615c’s CARD-like domain with APAF1-CARD and
Caspase9-CARD, attributing Rv2615c’s role in apoptosis. Since, Rv2615c
is reported to be upregulated in dormancy which suggest that it may be
one of the unexplored effectors employed by Mtb for its persistence via
silent cell-to-cell spread of infection by inducing macrophage
apoptosis. Additionally, Rv2615c’s interaction with TLR4 implicates its
engagement in host-pathogen interaction.