Rickettsia parkeri hypothetical protein RPATATE_1266, a homolog of exopolyphosphatase/guanosine pentaphosphate phosphohydrolase, regulates tick cell apoptosis
ABSTRACT Rickettsia parkeri, an intracellular bacterium transmitted by Amblyomma maculatum ticks, causes a febrile illness associated with eschar formation in humans. As a less virulent member of the spotted fever group within the Rickettsia genus, R. parkeri serves as an ideal model for studying in...
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American Society for Microbiology
2025-08-01
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| Series: | Microbiology Spectrum |
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| Online Access: | https://journals.asm.org/doi/10.1128/spectrum.00151-25 |
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| author | Dattatray V. Sawant Nicole Y. Burkhardt Haritha Katasani Benjamin Cull Ulrike G. Munderloh Xin-Ru Wang |
| author_facet | Dattatray V. Sawant Nicole Y. Burkhardt Haritha Katasani Benjamin Cull Ulrike G. Munderloh Xin-Ru Wang |
| author_sort | Dattatray V. Sawant |
| collection | DOAJ |
| description | ABSTRACT Rickettsia parkeri, an intracellular bacterium transmitted by Amblyomma maculatum ticks, causes a febrile illness associated with eschar formation in humans. As a less virulent member of the spotted fever group within the Rickettsia genus, R. parkeri serves as an ideal model for studying interactions between rickettsial pathogens, their vectors, and hosts. Our previous research showed that R. parkeri modulates mitochondrial-dependent apoptosis in tick cells, enhancing its intracellular survival and replication; however, the underlying mechanisms remain unclear. To investigate further, we employed a Himar1-based transposon mutagenesis system to identify R. parkeri genes involved in apoptosis. Using the modified plasmid pLoxHimar, we introduced a transposon into the R. parkeri Tate’s Hell strain and selected a mutant with an insertion in RPATATE_1266, a hypothetical protein with homology to exopolyphosphatase/guanosine pentaphosphate phosphohydrolase (Ppx/Gppa) family proteins, using mCherry fluorescence and spectinomycin/streptomycin resistance. The mutant genotype and single insertion site were confirmed by insertion site sequencing and inverse PCR. We found that the RPATATE_1266 mutant had reduced infection rates, growth, and plaque formation compared to wild-type R. parkeri in tick and mammalian cells. Moreover, the mutant showed upregulation of genes associated with ppx/gppa gene regulation networks (GRNs) and exhibited a marked inhibition of apoptosis in tick cells, including decreased expression of apoptosis-related genes, reduced mitochondrial membrane potential, and less DNA fragmentation. Restoration of RPATATE_1266 resulted in significant recovery of later-phase apoptosis, as measured by Caspase 3/7 activity. These findings suggest that RPATATE_1266 is a critical regulator of apoptosis in tick cells and could be a potential target for controlling R. parkeri infection and replication. This research enhances our understanding of how vector responses to pathogen infection influence pathogen replication and transmission.IMPORTANCERickettsia parkeri infections, though less severe than other rickettsioses, are becoming increasingly significant due to the expanding geographic range of their tick vector and their role in shaping our understanding of rickettsial biology. Advancing knowledge of the molecular mechanisms that regulate R. parkeri infection and replication is important for the field of vector-pathogen interactions. This study identifies the RPATATE_1266 gene (a hypothetical protein with homology to exopolyphosphatase/guanosine pentaphosphate phosphohydrolase [Ppx/Gppa] family proteins) as a key regulator of mitochondrial-dependent apoptosis in tick cells, a process critical for rickettsial intracellular survival. By elucidating the role of this gene, we provide new insights into the molecular interactions between rickettsial pathogens and their vectors. These findings not only enhance our understanding of pathogen-vector dynamics but also highlight potential directions for developing future strategies to manage rickettsial diseases beyond those caused by R. parkeri. |
| format | Article |
| id | doaj-art-cca8b80d2181493dbc2e67743eb18efc |
| institution | Kabale University |
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| language | English |
| publishDate | 2025-08-01 |
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| spelling | doaj-art-cca8b80d2181493dbc2e67743eb18efc2025-08-20T03:44:01ZengAmerican Society for MicrobiologyMicrobiology Spectrum2165-04972025-08-0113810.1128/spectrum.00151-25Rickettsia parkeri hypothetical protein RPATATE_1266, a homolog of exopolyphosphatase/guanosine pentaphosphate phosphohydrolase, regulates tick cell apoptosisDattatray V. Sawant0Nicole Y. Burkhardt1Haritha Katasani2Benjamin Cull3Ulrike G. Munderloh4Xin-Ru Wang5Department of Microbiology and Immunology, Upstate Medical University, Syracuse, New York, USADepartment of Entomology, University of Minnesota, St. Paul, Minnesota, USADepartment of Microbiology and Immunology, Upstate Medical University, Syracuse, New York, USADepartment of Entomology, University of Minnesota, St. Paul, Minnesota, USADepartment of Entomology, University of Minnesota, St. Paul, Minnesota, USADepartment of Microbiology and Immunology, Upstate Medical University, Syracuse, New York, USAABSTRACT Rickettsia parkeri, an intracellular bacterium transmitted by Amblyomma maculatum ticks, causes a febrile illness associated with eschar formation in humans. As a less virulent member of the spotted fever group within the Rickettsia genus, R. parkeri serves as an ideal model for studying interactions between rickettsial pathogens, their vectors, and hosts. Our previous research showed that R. parkeri modulates mitochondrial-dependent apoptosis in tick cells, enhancing its intracellular survival and replication; however, the underlying mechanisms remain unclear. To investigate further, we employed a Himar1-based transposon mutagenesis system to identify R. parkeri genes involved in apoptosis. Using the modified plasmid pLoxHimar, we introduced a transposon into the R. parkeri Tate’s Hell strain and selected a mutant with an insertion in RPATATE_1266, a hypothetical protein with homology to exopolyphosphatase/guanosine pentaphosphate phosphohydrolase (Ppx/Gppa) family proteins, using mCherry fluorescence and spectinomycin/streptomycin resistance. The mutant genotype and single insertion site were confirmed by insertion site sequencing and inverse PCR. We found that the RPATATE_1266 mutant had reduced infection rates, growth, and plaque formation compared to wild-type R. parkeri in tick and mammalian cells. Moreover, the mutant showed upregulation of genes associated with ppx/gppa gene regulation networks (GRNs) and exhibited a marked inhibition of apoptosis in tick cells, including decreased expression of apoptosis-related genes, reduced mitochondrial membrane potential, and less DNA fragmentation. Restoration of RPATATE_1266 resulted in significant recovery of later-phase apoptosis, as measured by Caspase 3/7 activity. These findings suggest that RPATATE_1266 is a critical regulator of apoptosis in tick cells and could be a potential target for controlling R. parkeri infection and replication. This research enhances our understanding of how vector responses to pathogen infection influence pathogen replication and transmission.IMPORTANCERickettsia parkeri infections, though less severe than other rickettsioses, are becoming increasingly significant due to the expanding geographic range of their tick vector and their role in shaping our understanding of rickettsial biology. Advancing knowledge of the molecular mechanisms that regulate R. parkeri infection and replication is important for the field of vector-pathogen interactions. This study identifies the RPATATE_1266 gene (a hypothetical protein with homology to exopolyphosphatase/guanosine pentaphosphate phosphohydrolase [Ppx/Gppa] family proteins) as a key regulator of mitochondrial-dependent apoptosis in tick cells, a process critical for rickettsial intracellular survival. By elucidating the role of this gene, we provide new insights into the molecular interactions between rickettsial pathogens and their vectors. These findings not only enhance our understanding of pathogen-vector dynamics but also highlight potential directions for developing future strategies to manage rickettsial diseases beyond those caused by R. parkeri.https://journals.asm.org/doi/10.1128/spectrum.00151-25Rickettsia parkeriapoptosisRPATATE_1266 mutant rickettsia |
| spellingShingle | Dattatray V. Sawant Nicole Y. Burkhardt Haritha Katasani Benjamin Cull Ulrike G. Munderloh Xin-Ru Wang Rickettsia parkeri hypothetical protein RPATATE_1266, a homolog of exopolyphosphatase/guanosine pentaphosphate phosphohydrolase, regulates tick cell apoptosis Microbiology Spectrum Rickettsia parkeri apoptosis RPATATE_1266 mutant rickettsia |
| title | Rickettsia parkeri hypothetical protein RPATATE_1266, a homolog of exopolyphosphatase/guanosine pentaphosphate phosphohydrolase, regulates tick cell apoptosis |
| title_full | Rickettsia parkeri hypothetical protein RPATATE_1266, a homolog of exopolyphosphatase/guanosine pentaphosphate phosphohydrolase, regulates tick cell apoptosis |
| title_fullStr | Rickettsia parkeri hypothetical protein RPATATE_1266, a homolog of exopolyphosphatase/guanosine pentaphosphate phosphohydrolase, regulates tick cell apoptosis |
| title_full_unstemmed | Rickettsia parkeri hypothetical protein RPATATE_1266, a homolog of exopolyphosphatase/guanosine pentaphosphate phosphohydrolase, regulates tick cell apoptosis |
| title_short | Rickettsia parkeri hypothetical protein RPATATE_1266, a homolog of exopolyphosphatase/guanosine pentaphosphate phosphohydrolase, regulates tick cell apoptosis |
| title_sort | rickettsia parkeri hypothetical protein rpatate 1266 a homolog of exopolyphosphatase guanosine pentaphosphate phosphohydrolase regulates tick cell apoptosis |
| topic | Rickettsia parkeri apoptosis RPATATE_1266 mutant rickettsia |
| url | https://journals.asm.org/doi/10.1128/spectrum.00151-25 |
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