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Encephalitozoon cuniculi and Vittaforma corneae (Phylum Microsporidia) inhibit staurosporine-induced apoptosis in human THP-1 macrophages in vitro.

ABSTRACT: Obligately intracellular microsporidia regulate their host cell life cycles, including apoptosis, but this has not been evaluated in phagocytic host cells such as macrophages that can facilitate infection but also can be activated to kill microsporidia. We examined two biologically dissimilar human-infecting microsporidia species, Encephalitozoon cuniculi and Vittaforma corneae, for their effects on staurosporine-induced apoptosis in the human macrophage-differentiated cell line, THP1. Apoptosis was measured after exposure of THP-1 cells to live and dead mature organisms via direct fluorometric measurement of Caspase 3, colorimetric and fluorometric TUNEL assays, and mRNA gene expression profiles using Apoptosis RT2 Profiler PCR Array. Both species of microsporidia modulated the intrinsic apoptosis pathway. In particular, live E. cuniculi spores inhibited staurosporine-induced apoptosis as well as suppressed pro-apoptosis genes and upregulated anti-apoptosis genes more broadly than V. corneae. Exposure to dead spores induced an opposite effect. Vittaforma corneae, however, also induced inflammasome activation via Caspases 1 and 4. Of the 84 apoptosis-related genes assayed, 42 (i.e. 23 pro-apoptosis, nine anti-apoptosis, and 10 regulatory) genes were more affected including those encoding members of the Bcl2 family, caspases and their regulators, and members of the tumour necrosis factor (TNF)/TNF receptor R superfamily.

SUBMITTER: Sokolova YY

PROVIDER: S-EPMC6435431 | biostudies-literature | 2019 Apr

REPOSITORIES: biostudies-literature

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Project description:BACKGROUND: Microsporidia are obligate intracellular eukaryotic parasites with genomes ranging in size from 2.3 Mbp to more than 20 Mbp. The extremely small (2.9 Mbp) and highly compact (approximately 1 gene/kb) genome of the human parasite Encephalitozoon cuniculi has been fully sequenced. The aim of this study was to characterize noncoding motifs that could be involved in regulation of gene expression in E. cuniculi and to show whether these motifs are conserved among the phylum Microsporidia. RESULTS: To identify such signals, 5' and 3'RACE-PCR experiments were performed on different E. cuniculi mRNAs. This analysis confirmed that transcription overrun occurs in E. cuniculi and may result from stochastic recognition of the AAUAAA polyadenylation signal. Such experiments also showed highly reduced 5'UTR's (<7 nts). Most of the E. cuniculi genes presented a CCC-like motif immediately upstream from the coding start. To characterize other signals involved in differential transcriptional regulation, we then focused our attention on the gene family coding for ribosomal proteins. An AAATTT-like signal was identified upstream from the CCC-like motif. In rare cases the cytosine triplet was shown to be substituted by a GGG-like motif. Comparative genomic studies confirmed that these different signals are also located upstream from genes encoding ribosomal proteins in other microsporidian species including Antonospora locustae, Enterocytozoon bieneusi, Anncaliia algerae (syn. Brachiola algerae) and Nosema ceranae. Based on these results a systematic analysis of the approximately 2000 E. cuniculi coding DNA sequences was then performed and brings to highlight that 364 translation initiation codons (18.29% of total CDSs) had been badly predicted. CONCLUSION: We identified various signals involved in the maturation of E. cuniculi mRNAs. Presence of such signals, in phylogenetically distant microsporidian species, suggests that a common regulatory mechanism exists among the microsporidia. Furthermore, 5'UTRs being strongly reduced, these signals can be used to ensure the accurate prediction of translation initiation codons for microsporidian genes and to improve microsporidian genome annotation.

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Encephalitozoon cuniculi and Vittaforma corneae (Phylum Microsporidia) inhibit staurosporine-induced apoptosis in human THP-1 macrophages in vitro.

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