Guanylate binding proteins directly attack Toxoplasma gondii via supramolecular complexes

Abstract

GBPs are essential for immunity against intracellular pathogens, especially for Toxoplasma gondii control. Here, the molecular interactions of murine GBPs (mGBP1/2/3/5/6), homo- and hetero-multimerization properties of mGBP2 and its function in parasite killing were investigated by mutational, Multiparameter Fluorescence Image Spectroscopy, and live cell microscopy methodologies. Control of T. gondii replication by mGBP2 requires GTP hydrolysis and isoprenylation thus, enabling reversible oligomerization in vesicle-like structures. mGBP2 undergoes structural transitions between monomeric, dimeric and oligomeric states visualized by quantitative FRET analysis. mGBPs reside in at least two discrete subcellular reservoirs and attack the parasitophorous vacuole membrane (PVM) as orchestrated, supramolecular complexes forming large, densely packed multimers comprising up to several thousand monomers. This dramatic mGBP enrichment results in the loss of PVM integrity, followed by a direct assault of mGBP2 upon the plasma membrane of the parasite. These discoveries provide vital dynamic and molecular perceptions into cell-autonomous immunity.DOI: http://dx.doi.org/10.7554/eLife.11479.001

Interferon-Inducible GTPases in Host Resistance, Inflammation and Disease

“…Together these results suggest a model where different GBPs have variations in either target selection or effector mechanisms during antimicrobial responses. This model is further supported by the recent finding that specific subsets of mGBPs cluster together as supramolecular complexes in vesicle-like structure (VLS) [102]. These clusters may organize mGBPs into groups, which share synergistic or cooperative functions.…”

“…Similar to IRGs, GBPs colocalize with membranous vesicles shed from PVs suggesting they have a role in the disruption of these structures [56, 103]. In uninfected cells stimulated with IFNγ, GBPs have been found to associate with VLS throughout the cytoplasm [102, 104]. Upon pathogen infection of murine cells, however, the distribution of these proteins changes as they relocate to the sites of infection.…”

“…In contrast, mGBP3 did associate with T. gondii PVs, which were in turn devoid of mGBP5 [96]. Furthermore, mGBP2 may be unique in its ability to enter the PV space and associate directly with the plasma membrane of the parasite [102]. These data suggest that specific host or pathogen features modulate the targeting of a subset of mouse GBPs although the specifics of these phenotypes have yet to be explained.…”

Nucleotide-dependent farnesyl switch orchestrates polymerization and membrane binding of human guanylate-binding protein 1

“…For both functions, the ability to interact with cellular membranes is a prerequisite. In the case of hGBP1 and murine GBP2 (mGBP2), abolishing the C-terminal lipid modification results in biologically inactive proteins (26)(27)(28)33). To understand the function and mechanism of hGBP1 on a molecular level, it is therefore of critical importance to study the protein in the lipid modified state.…”

Inflammasomes: mechanism of assembly, regulation and signalling

“…GBPs have so far mainly been shown to function in cellautonomous immunity and they restrict the replication of intracellular bacterial and protozoan pathogens 121 . They control antimicrobial processes ranging from oxidative and autophagy-based defences, to the destabilization of pathogen-containing vacuoles and direct killing of the pathogen 121,122 . Among the 11 mouse GBPs, GBP2 and GBP5 were shown to be required for F. novicidainduced AIM2 activation and GBP2 was required for caspase 11 activation by Gram-negative bacteria, but not for inflammasome activation in response to the purified ligands (such as poly(dA:dT) and LPS) 117,119,120 .…”