Guanylate-binding protein 1 (GBP1) contributes to the immunity of human mesenchymal stromal cells against Toxoplasma gondii

Abstract

Mesenchymal stromal cells (MSCs) have recently been shown to play important roles in mammalian host defenses against intracellular pathogens, but the molecular mechanism still needs to be clarified. We confirmed that human MSCs (hMSCs) prestimulated with IFN-γ showed a significant and dose-dependent ability to inhibit the growth of two types of Toxoplasma gondii [type I RH strain with green fluorescent proteins (RH/GFP) or type II PLK strain with red fluorescent proteins (PLK/RED)]. However, in contrast to previous reports, the anti-T. gondii activity of hMSCs was not mediated by indoleamine 2,3-dioxygenase (IDO). Genome-wide RNA sequencing (RNA-seq) analysis revealed that IFN-γ increased the expression of the p65 family of human guanylate-binding proteins (hGBPs) in hMSCs, especially hGBP1. To analyze the functional role of hGBPs, stable knockdowns of hGBP1, -2, and -5 in hMSCs were established using a lentiviral transfection system. hGBP1 knockdown in hMSCs resulted in a significant loss of the anti-T. gondii host defense property, compared with hMSCs infected with nontargeted control sequences. hGBP2 and -5 knockdowns had no effect. Moreover, the hGBP1 accumulation on the parasitophorous vacuole (PV) membranes of IFN-γ-stimulated hMSCs might protect against T. gondii infection. Taken together, our results suggest that hGBP1 plays a pivotal role in anti-T. gondii protection of hMSCs and may shed new light on clarifying the mechanism of host defense properties of hMSCs.human stem cells | parasitic protozoan | innate immunity | in vitro cultivation

Human GBP1 differentially targetsSalmonellaandToxoplasmato license recognition of microbial ligands and caspase-mediated death

“…Results obtained are consistent with similar GBP1 recruitment to Tg-containing vacuoles and phagosomes (Qin et al, 2017;Shydlovskyi et al, 2017;Fisch et al, 2019a). Our single-cell assays conclusively reveal that GBP1 decorates two distinct intracellular populations of Tg within the same cell -those formed by host-mediated phagocytosis or those formed by Tg invasion.…”

Sensing of invading pathogens by GBPs: At the crossroads between cell-autonomous and innate immunity

“…Recent findings show that, in mesenchymal stromal cells, hGBP1 localizes to the PCV membrane and inhibits parasite replication. This antimicrobial effect was, however, not observed for hGBP2 or hGBP5 . A different study performed in A549 lung epithelial cells suggested that hGBP1 does not associate with the T. gondii PCV .…”

“…This antimicrobial effect was, however, not observed for hGBP2 or hGBP5. 29 A different study performed in A549 lung epithelial cells suggested that hGBP1 does not associate with the T. gondii PCV. 30 Furthermore, in IFN-stimulated human fibroblasts T. gondii replication is controlled independently of hGBP1 and hGBP2, 31 and in HeLa cells, parasite growth is restricted by noncanonical autophagy.…”

ToxoplasmaGRA15 limits parasite growth in IFNγ-activated fibroblasts through TRAF ubiquitin ligases

“…To counter the host defense mechanisms, Toxoplasma secretes ROP and GRA effector proteins into the host cell from organelles called rhoptries and dense granules, respectively. In both murine and human cells, the type II strain is more susceptible to IFNγ-mediated growth inhibition than the type I strain Haldar et al, 2015;Qin et al, 2017;Selleck et al, 2015). Resistance of type I strains in murine cells is determined primarily by polymorphic ROP5 and ROP18, which, together with ROP17 and GRA7, cooperatively block IRG and GBP loading on the PVM and subsequent events (Behnke et al, 2015;Etheridge et al, 2014;Fleckenstein et al, 2012;Haldar et al, 2015;Niedelman et al, 2012;Steinfeldt et al, 2010;Khaminets et al, 2010).…”