Two Phosphoglucomutase Paralogs Facilitate Ionophore-Triggered Secretion of the <italic toggle="yes">Toxoplasma</italic> Micronemes
ABSTRACT Paralogs of the widely prevalent phosphoglucomutase (PGM) protein called parafusin function in calcium (Ca2+)-mediated exocytosis across eukaryotes. In Toxoplasma gondii, the parafusin-related protein 1 (PRP1) has been associated with Ca2+-dependent microneme organelle secretion required fo...
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| Format: | Article |
| Language: | English |
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American Society for Microbiology
2017-12-01
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| Series: | mSphere |
| Subjects: | |
| Online Access: | https://journals.asm.org/doi/10.1128/mSphere.00521-17 |
| _version_ | 1818836550249611264 |
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| author | Sudeshna Saha Bradley I. Coleman Rashmi Dubey Ira J. Blader Marc-Jan Gubbels |
| author_facet | Sudeshna Saha Bradley I. Coleman Rashmi Dubey Ira J. Blader Marc-Jan Gubbels |
| author_sort | Sudeshna Saha |
| collection | DOAJ |
| description | ABSTRACT Paralogs of the widely prevalent phosphoglucomutase (PGM) protein called parafusin function in calcium (Ca2+)-mediated exocytosis across eukaryotes. In Toxoplasma gondii, the parafusin-related protein 1 (PRP1) has been associated with Ca2+-dependent microneme organelle secretion required for essential processes like host cell invasion and egress. Using reverse genetics, we observed PRP1 to be dispensable for completion of the lytic cycle, including host cell invasion and egress by the parasite. However, the absence of the gene affected increased microneme release triggered by A23187, a Ca2+ ionophore used to raise the cytoplasmic Ca2+ concentration mimicking the physiological role of Ca2+ during invasion and egress. The basal levels of constitutive microneme release in extracellular parasites and phosphatidic acid-triggered microneme secretion were unaffected in the mutant. The phenotype of the deletion mutant of the second PGM-encoding gene in Toxoplasma, PGM2, was similar to the phenotype of the PRP1 deletion mutant. Furthermore, the ability of the tachyzoites to induce acute infection in the mice remained normal in the absence of both PGM paralogs. Our data thus reveal that the microneme secretion upon high Ca2+ flux is facilitated by the Toxoplasma PGM paralogs, PRP1 and PGM2. However, this protein-mediated release is neither essential for lytic cycle completion nor for acute virulence of the parasite. IMPORTANCE Ca2+-dependent exocytosis is essential for the life cycle of apicomplexan parasites. Toxoplasma gondii harbors a phosphoglucomutase (PGM) ortholog, PRP1, previously associated with Ca2+-dependent microneme secretion. Here it is shown that genetic deletion of either PRP1, its PGM2 ortholog, or both genes is dispensable for the parasite’s lytic cycle, including host cell egress and invasion. Depletion of the proteins abrogated high Ca2+-mediated microneme secretion induced by the ionophore A23187; however, the constitutive and phosphatidic acid-mediated release remained unaffected. Secretion mediated by the former pathway is not essential for tachyzoite survival or acute in vivo infection in the mice. |
| first_indexed | 2024-12-19T03:08:23Z |
| format | Article |
| id | doaj.art-6092f150a9ed466da7694063c9ed69f2 |
| institution | Directory Open Access Journal |
| issn | 2379-5042 |
| language | English |
| last_indexed | 2024-12-19T03:08:23Z |
| publishDate | 2017-12-01 |
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| series | mSphere |
| spelling | doaj.art-6092f150a9ed466da7694063c9ed69f22022-12-21T20:38:04ZengAmerican Society for MicrobiologymSphere2379-50422017-12-012610.1128/mSphere.00521-17Two Phosphoglucomutase Paralogs Facilitate Ionophore-Triggered Secretion of the <italic toggle="yes">Toxoplasma</italic> MicronemesSudeshna Saha0Bradley I. Coleman1Rashmi Dubey2Ira J. Blader3Marc-Jan Gubbels4Department of Biology, Boston College, Chestnut Hill, Massachusetts, USADepartment of Biology, Boston College, Chestnut Hill, Massachusetts, USADepartment of Biology, Boston College, Chestnut Hill, Massachusetts, USADepartment of Microbiology and Immunology, University at Buffalo School of Medicine, Buffalo, New York, USADepartment of Biology, Boston College, Chestnut Hill, Massachusetts, USAABSTRACT Paralogs of the widely prevalent phosphoglucomutase (PGM) protein called parafusin function in calcium (Ca2+)-mediated exocytosis across eukaryotes. In Toxoplasma gondii, the parafusin-related protein 1 (PRP1) has been associated with Ca2+-dependent microneme organelle secretion required for essential processes like host cell invasion and egress. Using reverse genetics, we observed PRP1 to be dispensable for completion of the lytic cycle, including host cell invasion and egress by the parasite. However, the absence of the gene affected increased microneme release triggered by A23187, a Ca2+ ionophore used to raise the cytoplasmic Ca2+ concentration mimicking the physiological role of Ca2+ during invasion and egress. The basal levels of constitutive microneme release in extracellular parasites and phosphatidic acid-triggered microneme secretion were unaffected in the mutant. The phenotype of the deletion mutant of the second PGM-encoding gene in Toxoplasma, PGM2, was similar to the phenotype of the PRP1 deletion mutant. Furthermore, the ability of the tachyzoites to induce acute infection in the mice remained normal in the absence of both PGM paralogs. Our data thus reveal that the microneme secretion upon high Ca2+ flux is facilitated by the Toxoplasma PGM paralogs, PRP1 and PGM2. However, this protein-mediated release is neither essential for lytic cycle completion nor for acute virulence of the parasite. IMPORTANCE Ca2+-dependent exocytosis is essential for the life cycle of apicomplexan parasites. Toxoplasma gondii harbors a phosphoglucomutase (PGM) ortholog, PRP1, previously associated with Ca2+-dependent microneme secretion. Here it is shown that genetic deletion of either PRP1, its PGM2 ortholog, or both genes is dispensable for the parasite’s lytic cycle, including host cell egress and invasion. Depletion of the proteins abrogated high Ca2+-mediated microneme secretion induced by the ionophore A23187; however, the constitutive and phosphatidic acid-mediated release remained unaffected. Secretion mediated by the former pathway is not essential for tachyzoite survival or acute in vivo infection in the mice.https://journals.asm.org/doi/10.1128/mSphere.00521-17PRP1Toxoplasma gondiicalciummicronemesparafusinphosphoglucomutase |
| spellingShingle | Sudeshna Saha Bradley I. Coleman Rashmi Dubey Ira J. Blader Marc-Jan Gubbels Two Phosphoglucomutase Paralogs Facilitate Ionophore-Triggered Secretion of the <italic toggle="yes">Toxoplasma</italic> Micronemes mSphere PRP1 Toxoplasma gondii calcium micronemes parafusin phosphoglucomutase |
| title | Two Phosphoglucomutase Paralogs Facilitate Ionophore-Triggered Secretion of the <italic toggle="yes">Toxoplasma</italic> Micronemes |
| title_full | Two Phosphoglucomutase Paralogs Facilitate Ionophore-Triggered Secretion of the <italic toggle="yes">Toxoplasma</italic> Micronemes |
| title_fullStr | Two Phosphoglucomutase Paralogs Facilitate Ionophore-Triggered Secretion of the <italic toggle="yes">Toxoplasma</italic> Micronemes |
| title_full_unstemmed | Two Phosphoglucomutase Paralogs Facilitate Ionophore-Triggered Secretion of the <italic toggle="yes">Toxoplasma</italic> Micronemes |
| title_short | Two Phosphoglucomutase Paralogs Facilitate Ionophore-Triggered Secretion of the <italic toggle="yes">Toxoplasma</italic> Micronemes |
| title_sort | two phosphoglucomutase paralogs facilitate ionophore triggered secretion of the italic toggle yes toxoplasma italic micronemes |
| topic | PRP1 Toxoplasma gondii calcium micronemes parafusin phosphoglucomutase |
| url | https://journals.asm.org/doi/10.1128/mSphere.00521-17 |
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