An ortholog of Plasmodium falciparum chloroquine resistance transporter (PfCRT) plays a key role in maintaining the integrity of the endolysosomal system in Toxoplasma gondii to facilitate host invasion.

Publisher: Public Library of Science Country of Publication: United States NLM ID: 101238921 Publication Model: eCollection Cited Medium: Internet ISSN: 1553-7374 (Electronic) Linking ISSN: 15537366 NLM ISO Abbreviation: PLoS Pathog Subsets: MEDLINE

Original Publication: San Francisco, CA : Public Library of Science, c2005-

Endosomes*/metabolism ; Endosomes*/parasitology ; Lysosomes*/metabolism ; Lysosomes*/parasitology ; Membrane Transport Proteins*/genetics ; Membrane Transport Proteins*/metabolism ; Plasmodium falciparum*/genetics ; Plasmodium falciparum*/metabolism ; Plasmodium falciparum*/pathogenicity ; Protozoan Proteins*/genetics ; Protozoan Proteins*/metabolism ; Toxoplasma*/genetics ; Toxoplasma*/metabolism ; Toxoplasma*/pathogenicity ; Toxoplasmosis*/genetics ; Toxoplasmosis*/metabolism ; Toxoplasmosis*/pathology; Chloroquine/*pharmacology; Cell Line ; Humans

Toxoplasma gondii is an apicomplexan parasite with the ability to use foodborne, zoonotic, and congenital routes of transmission that causes severe disease in immunocompromised patients. The parasites harbor a lysosome-like organelle, termed the "Vacuolar Compartment/Plant-Like Vacuole" (VAC/PLV), which plays an important role in maintaining the lytic cycle and virulence of T. gondii. The VAC supplies proteolytic enzymes that contribute to the maturation of invasion effectors and that digest autophagosomes and endocytosed host proteins. Previous work identified a T. gondii ortholog of the Plasmodium falciparum chloroquine resistance transporter (PfCRT) that localized to the VAC. Here, we show that TgCRT is a membrane transporter that is functionally similar to PfCRT. We also genetically ablate TgCRT and reveal that the TgCRT protein plays a key role in maintaining the integrity of the parasite's endolysosomal system by controlling morphology of the VAC. When TgCRT is absent, the VAC dramatically increases in volume by ~15-fold and overlaps with adjacent endosome-like compartments. Presumably to reduce aberrant swelling, transcription and translation of endolysosomal proteases are decreased in ΔTgCRT parasites. Expression of subtilisin protease 1 is significantly reduced, which impedes trimming of microneme proteins, and significantly decreases parasite invasion. Chemical or genetic inhibition of proteolysis within the VAC reverses these effects, reducing VAC size and partially restoring integrity of the endolysosomal system, microneme protein trimming, and invasion. Taken together, these findings reveal for the first time a physiological role of TgCRT in substrate transport that impacts VAC volume and the integrity of the endolysosomal system in T. gondii.
Competing Interests: The authors have declared that no competing interests exist.

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R01 AI096836 United States AI NIAID NIH HHS; T32 AI060546 United States AI NIAID NIH HHS; P20 GM109094 United States GM NIGMS NIH HHS; R01 AI111962 United States AI NIAID NIH HHS; R01 AI056312 United States AI NIAID NIH HHS; R01 AI143707 United States AI NIAID NIH HHS

0 (Membrane Transport Proteins)
0 (PfCRT protein, Plasmodium falciparum)
0 (Protozoan Proteins)
886U3H6UFF (Chloroquine)

Date Created: 20190607 Date Completed: 20191203 Latest Revision: 20201214

20231215

PMC6553793

10.1371/journal.ppat.1007775

31170269