Functional Dissection of Toxoplasma gondii Perforin-like Protein 1 Reveals a Dual Domain Mode of Membrane Binding for Cytolysis and Parasite Egress

Pathogenic microbes rely on environmental cues to initiate key events during infection such as differentiation, motility, egress and invasion of cells or tissues. Earlier investigations showed that an acidic environment activates motility of the protozoan parasite T. gondii. Conversely, potassium ions, which are abundant in the intracellular milieu that bathes immotile replicating parasites, suppress motility. Since motility is required for efficient parasite cell invasion and egress we sought to better understand its regulation by environmental cues. We found that low pH stimulates motility by triggering Ca2+-dependent secretion of apical micronemes, and that this cue is sufficient to overcome suppression by potassium ions and drive parasite motility, cell invasion and egress. We also discovered that acidification promotes membrane binding and cytolytic activity of perforin-like protein 1 (PLP1), a pore-forming protein required for efficient egress. Agents that neutralize pH reduce the efficiency of PLP1-dependent perforation of host membranes and compromise egress. Finally, although low pH stimulation of microneme secretion promotes cell invasion, it also causes PLP1-dependent damage to host cells, suggesting a mechanism by which neutral extracellular pH subdues PLP1 activity to allow cell invasion without overt damage to the target cell. These findings implicate acidification as a signal to activate microneme secretion and confine cytolytic activity to egress without compromising the viability of the next cell infected.

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“…The slide was incubated at 37°C for 3 min, fixed with 8% formaldehyde and occupied vacuoles were enumerated as previously described [25].…”

Section: Methodsmentioning

confidence: 99%

Acidification Activates Toxoplasma gondii Motility and Egress by Enhancing Protein Secretion and Cytolytic Activity

2014

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“…Like a Plasmodium merozoite, surface antigens aid in the interaction between the tachyzoite and the host cell. One antigen known to have membrane-binding activity is Perforinlike Protein 1 (PLP-1), forming pores in the host cell membrane after binding and as well as playing a role in egress[194]. The parasite then re-orients its position such that the apical end has contact with the host cell.…”

Section: Mechanisms Of Host Cell Invasion By Apicomplexan Parasitesmentioning

confidence: 99%

Mechanisms of cellular invasion by intracellular parasites

Walker

Oghumu

Gupta

et al. 2013

Cell. Mol. Life Sci.

146

108

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Numerous disease-causing parasites must invade host cells to prosper. Collectively, such pathogens are responsible for a staggering amount of human sickness and death throughout the world. Leishmaniasis, Chagas disease, toxoplasmosis, and malaria are neglected diseases and therefore are linked to socio-economical and geographical factors, affecting well-over half the world's population.Such obligate intracellular parasites have co-evolved with humans to establish a complexity of specific molecular parasite-host cell interactions, forming the basis of the parasite's cellular tropism. They make use of such interactions to invade host cells as a means to migrate through various tissues, to evade the host immune system, and to undergo intracellular replication. These cellular migration and invasion events are absolutely essential for the completion of the lifecycles of these parasites and lead to their for disease pathogenesis.This review is an overview of the molecular mechanisms of protozoan parasite invasion of host cells and discussion of therapeutic strategies, which could be developed by targeting these invasion pathways. Specifically, we focus on four species of protozoan parasites

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“…Pore formation and hemolytic activity by recombinant TgPLP1 (purified from Escherichia coli ) was demonstrated recently by Roiko and Carruthers [**17]. TgPLP1 exhibited significantly reduced specific activity compared to the CDC listeriolysin O.…”

Section: The Apimacpf Pore-forming Mechanismmentioning

confidence: 88%

“…The pore complex size varies depending on the specific CDC or MACPF: the CDC pore is typically comprised of 35-40 monomers with an estimated pore diameter of 250-300Å (reviewed in [8]), whereas MACPFs contain 13-20 monomers with a pore diameter of 80-200Å [2,*14]. The size(s) of the various ApiMACPFs pore is unknown, but gel analysis of oligomeric complexes of the T gondii TgPLP1 suggest >22 monomers comprise its pore complex [**17]. …”

Section: Overview Of the Cdc/macpf Domain And Pore Formationmentioning

confidence: 99%

The Apicomplexan CDC/MACPF-like pore-forming proteins

Wade

Tweten

2015

Current Opinion in Microbiology

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Pore-forming proteins (PFPs) encompass a broad family of proteins that are used for virulence or immune defense. Members of the cholesterol-dependent cytolysins (CDCs) and membrane attack complex/perforin (MACPF) family of PFPs form large β-barrel pores in the membrane. The CDC/MACPF proteins contain a characteristic 4-stranded β-sheet that is flanked by two α-helical bundles, which unfold to form two transmembrane β-hairpins. Apicomplexan eukaryotic parasites express CDC/MACPFs termed perforin-like proteins (PLPs). Here we review recent studies that provide key insights into the assembly and regulation of the Apicomplexan PLP (ApiMACPF) molecular pore-forming mechanisms, which are necessary for the osmotically driven rupture of the parasitophorous vacuole and host cell membrane, and cell traversal by these parasites.

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Functional Dissection of Toxoplasma gondii Perforin-like Protein 1 Reveals a Dual Domain Mode of Membrane Binding for Cytolysis and Parasite Egress

Cited by 51 publications

References 51 publications

Acidification Activates Toxoplasma gondii Motility and Egress by Enhancing Protein Secretion and Cytolytic Activity

Acidification Activates Toxoplasma gondii Motility and Egress by Enhancing Protein Secretion and Cytolytic Activity

Mechanisms of cellular invasion by intracellular parasites

The Apicomplexan CDC/MACPF-like pore-forming proteins

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