PE_PGRS3 ofMycobacterium tuberculosisis specifically expressed at low phosphate concentration, and its arginine-rich C-terminal domain mediates adhesion and persistence in host tissues when expressed inMycobacterium smegmatis

Abstract

PE_PGRSs of Mycobacterium tuberculosis (Mtb) represent a family of complex and peculiar proteins whose role and function remain elusive. In this study, we investigated PE_PGRS3 and PE_PGRS4, two highly homologous PE_PGRSs encoded by two contiguous genes in the Mtb genome. Using a gene-reporter system in Mycobacterium smegmatis (Ms) and transcriptional analysis in Mtb, we show that PE_PGRS3, but not PE_PGRS4, is specifically expressed under low phosphate concentrations. Interestingly, PE_PGRS3, but not PE_PGRS4, has a unique, arginine-rich C-terminal domain of unknown function. Heterologous expression of PE_PGRS3 in Ms was used to demonstrate cellular localisation of the protein on the mycobacterial surface, where it significantly affects net surface charge. Moreover, expression of full-length PE_PGRS3 enhanced adhesion of Ms to murine macrophages and human epithelial cells and improved bacterial persistence in spleen tissue following infection in mice. Expression of the PE_PGRS3 functional deletion mutant lacking the C-terminal domain in Ms did not enhance adhesion to host cells, showing a phenotype similar to the Ms parental strain. Interestingly, enhanced persistence of Ms expressing PE_PGRS3 did not correlate with increased concentrations of inflammatory cytokines. These results point to a critical role for the ≈ 80 amino acids long, arginine-rich C-terminal domain of PE_PGRS3 in tuberculosis pathogenesis.

Graphene oxide prevents mycobacteria entry into macrophages through extracellular entrapment

“…37 Aggregation masks the GO blades and cations act as "bridges" between the negatively charged GO surface and the mycobacterial surface, which is also negatively charged. 38 In a series of experiments, we also showed that treatment with GO impairs mycobacterial entry into macrophages. Interestingly, GO was able to reduce the intracellular mycobacterial load as demonstrated by CFU analysis and confocal microscopy by trapping extracellular mycobacteria.…”

“…Six hours post incubation colony forming units (CFUs) were determined by plating serial dilutions of the suspensions on 7H11 solid medium (Difco) supplemented with 10% Oleic Albumin Dextrose Catalase (OADC) (Sigma-Aldrich). 38 To measure the GO trapping effect, suspensions of mycobacteria/GO were sonicated in a water bath (Becton Dickinson, output puissance 100 W to 42 kHz AE6%) for different time points (5 0 and 20 0 ) and the CFU was determined as above.…”

“…Finally, the chamber slides were washed with PBS and analysed by confocal microscopy. 38 Images were collected by using an inverted confocal microscope (DMIRE2, Leica Microsystems, Wetzlar, Germany) equipped with a 63Â oil immersion objective. For GFP excitation a He/Ne laser at 476 nm was used.…”

Deciphering Within-Host Microevolution of Mycobacterium tuberculosis through Whole-Genome Sequencing: the Phenotypic Impact and Way Forward

“…Farhat et al detected four different variants in PE-PGRS9 appearing and disappearing over time (25), while the variant T320A emerged over the time of 9 months in another study (51). PE-PGRS3 has been found to be specifically expressed at low phosphate concentrations, and its unique, arginine-rich C-terminal domain was suggested to enhance adhesion and to be involved in tuberculosis pathogenesis (66).…”

Molecular Basis Underlying Host Immunity Subversion by Mycobacterium tuberculosis PE/PPE Family Molecules

“…PPE37 was induced under low-iron conditions through the course of infection (Ahmad et al, 2018). PE_PGRS3 is specifically expressed under low phosphate concentrations (De Maio et al, 2018). In contrast, transcriptome data revealed that PE35 was significantly reduced under persistence conditions (Boshoff et al, 2004).…”