Phylogenetic relationships of methionine aminopeptidase 2 among Encephalitozoon species and genotypes of microsporidia

Establishment and application of a loop-mediated isothermal amplification method based on MetAP2 gene for the detection of Nosema bombycis in silkworms (Bombyx mori)

Pebrine, caused by Nosema bombycis, is a devastating disease of silkworms that causes huge economic losses to the sericulture farmers. Although pebrine is a quarantine disease, currently the development of effective molecular diagnostic or therapeutic tools for its management is still a lagging hotspot in sericulture research. In the present study, a highly specific, sensitive, and field-applicable LAMP assay targeting MetAp2 gene was developed. LM1 primer set produced better results, with fluorescence (amplification) signals appearing in ~50 min. The reaction temperature of 60.9°C and outer primer to inner primer ratio of 1:8 were found to be optimal, with the shortest amplification time and strongest fluorescence intensity. The LAMP assay showed high specificity for the DNA of Nosema bombycis spores, as the templates of other common microorganisms of silkworms showed no amplification. The LAMP assay detected pMD-19T-met positive plasmid at the lowest concentration of 103 copies, with a detection time of ~80 min. The practicality test showed that the LAMP assay can detect Nosema bombycis spore DNA at the lowest concentration of 10-3 ng/μL. At concentration of 1.2 ng/μL, the real-time fluorescence signals appeared in ~60 min. The LAMP assay detected Nosema bombycis at all life stages of untreated silkworms. In fumagillin treated silkworms, no real-time fluorescence amplification was observed at 90 h and later, indicating the reliability of LAMP in detecting Nosema bombycis, and effectiveness of fumagillin, to some degree, in treating pebrine infection. The developed LAMP assay holds good promise for its application as a specific and field-applicable tool for the detection/control of pebrine in the field settings.

Methionine aminopeptidases: Potential therapeutic target for microsporidia and other microbes

Methionine aminopeptidases (MetAPs) have emerged as a target for medicinal chemists in the quest for novel therapeutic agents for treating cancer, obesity, and other disorders. Methionine aminopeptidase is a metalloenzyme with two structurally distinct forms in humans, MetAP-1 and MetAP-2. The MetAP2 inhibitor fumagillin, which was used as an amebicide in the 1950s, has been used for the successful treatment of microsporidiosis in humans; however, it is no longer commercially available. Despite significant efforts and investments by many pharmaceutical companies, no new MetAP inhibitors have been approved for the clinic. Several lead compounds have been designed and synthesized by researchers as potential inhibitors of MetAP and evaluated for their potential activity in a wide range of diseases. MetAP inhibitors such as fumagillin, TNP-470, beloranib, and reversible inhibitors and their analogs guide new prospects for MetAP inhibitor development in the ongoing quest for new pharmacological indications. This perspective provides insights into recent advances related to MetAP, as a potential therapeutic target in drug discovery, bioactive small molecule MetAP2 inhibitors, and data on the role of MetAP-2 as a therapeutic target for microsporidiosis.

Molecular characterization and phylogenetic analyses of MetAP2 gene and protein of Nosema bombycis isolated from Guangdong, China

Background

Pebrine, caused by microsporidium Nosema bombycis, is a devastating disease that causes serious economic damages to the sericulture industry. Studies on development of therapeutic and diagnostic options for managing pebrine in silkworms are very limited. Methionine aminopeptidase type 2 (MetAP2) of microsporidia is an essential gene for their survival and has been exploited as the cellular target of drugs such as fumagillin and its analogues in several microsporidia spp., including Nosema of honeybees.

Methods

In the present study, using molecular and bioinformatics tools, we performed in-depth characterization and phylogenetic analyses of MetAP2 of Nosema bombycis isolated from Guangdong province of China.

Results

The full length of MetAP2 gene sequence of Nosema bombycis (Guangdong isolate) was found to be 1278 base pairs (bp), including an open reading frame of 1,077 bp, encoding a total of 358 amino acids. The bioinformatics analyses predicted the presence of typical alpha-helix structural elements, and absence of transmembrane domains and signal peptides. Additionally, other characteristics of a stable protein were also predicted. The homology-based 3D models of MetAP2 of Nosema bombycis (Guangdong isolate) with high accuracy and reliability were developed. The MetAP2 protein was expressed and purified. The observed molecular weight of MetAP2 protein was found to be ~43-45 kDa. The phylogenetic analyses showed that MetAP2 gene and amino acids sequences of Nosema bombycis (Guangdong isolate) shared a close evolutionary relationship with Nosema spp. of wild silkworms, but it was divergent from microsporidian spp. of other insects, Aspergillus spp., Saccharomyces cerevisiae, and higher animals including humans. These analyses indicated that the conservation and evolutionary relationships of MetAP2 are closely linked to the species relationships.

Conclusion

This study provides solid foundational information that could be helpful in optimization and development of diagnostic and treatment options for managing the threat of Nosema bombycis infection in sericulture industry of China.

Molecular characterization of Nosema bombycis methionine aminopeptidase 2 (MetAP2) gene and evaluation of anti-microsporidian activity of Fumagilin-B in silkworm Bombyx mori

Nosema bombycis is a spore-forming parasite causing microsporidiosis in silkworm Bombyx mori. Methionine aminopeptidase 2 (MetAP2), an essential gene of N. bombycis, is a target for the anti-microsporidian drug Fumagillin, an antibiotic derived from Aspergillus fumigatus. In this study, a 1077 bp full-length cDNA of the MetAP2 gene of N. bombycis was cloned and characterized. Furthermore, the expression study of the MetAP2 gene revealed a ubiquitous expression during all the developmental stages of the silkworm B. mori. The phylogenetic analysis of the MetAP2 gene of N. bombycis revealed the MetAP2 gene sequences to be highly conserved in nature. The present study also includes the validation of the anti-microsporidian drug Fumagillin against the MetAP2 gene of N. bombycis. The findings revealed that Fumagilin-B could also suppress the N. bombycis multiplication in the silkworm B. mori, thereby proving the therapeutic role of Fumagillin against microsporidian infection. This is the first-ever report regarding the characterization of the MetAP2 gene in the Indian isolate of N. bombycis and also towards the usage of Fumagillin in the control of microsporidiosis in B. mori.

Molecular testing for clinical diagnosis and epidemiological investigations of intestinal parasitic infections

Over the past few decades, nucleic acid-based methods have been developed for the diagnosis of intestinal parasitic infections. Advantages of nucleic acid-based methods are numerous; typically, these include increased sensitivity and specificity and simpler standardization of diagnostic procedures. DNA samples can also be stored and used for genetic characterization and molecular typing, providing a valuable tool for surveys and surveillance studies. A variety of technologies have been applied, and some specific and general pitfalls and limitations have been identified. This review provides an overview of the multitude of methods that have been reported for the detection of intestinal parasites and offers some guidance in applying these methods in the clinical laboratory and in epidemiological studies.

Phylogenetic characterization of Encephalitozoon romaleae (Microsporidia) from a grasshopper host: relationship to Encephalitozoon spp. infecting humans

Encephalitozoon species are the most common microsporidian pathogens of humans and domesticated animals. We recently discovered a new microsporidium, Encephalitozoon romaleae, infecting the eastern lubber grasshopper Romalea microptera. To understand its evolutionary relationships, we compared partial gene sequences of alpha- and beta-tubulin and methionine aminopeptidase 2 enzyme from this and related species. We also analyzed the rRNA internal transcribed spacer. Based on tubulin and MetAP-2 gene phylogenetic analysis, E. romaleae clustered with the Encephalitzoon group with strong bootstrap support (>99%). Within the Encephalitozoon clade, E. romaleae clustered with Encephalitozoon hellem for both the beta-tubulin and MetAP-2 phylogenies based on ML tree. The alpha-tubulin based ML tree, however, placed the new microsporidium closer to Encephalitozoon cuniculi. The rRNA internal transcribed spacer region of E. romaleae has 91% homology with E. hellem.

ESTs from the microsporidian Edhazardia aedis

Background

Microsporidia are a group of parasites related to fungi that infect a wide variety of animals and have gained recognition from the medical community in the past 20 years due to their ability to infect immuno-compromised humans. Microsporidian genomes range in size from 2.3 to 19.5 Mbp, but almost all of our knowledge comes from species that have small genomes (primarily from the human parasite Encephalitozoon cuniculi and the locust parasite Antonospora locustae). We have conducted an EST survey of the mosquito parasite Edhazardia aedis, which has an estimated genome size several times that of more well-studied species. The only other microsporidian EST project is from A. locustae, and serves as a basis for comparison with E. aedis.

Results

The spore transcriptomes of A. locustae and E. aedis were compared and the numbers of unique transcripts that belong to each COG (Clusters of Orthologous Groups of proteins) category differ by at most 5%. The transcripts themselves have widely varying start sites and encode a number of proteins that have not been found in other microsporidia examined to date. However, E. aedis seems to lack the multi-gene transcripts present in A. locustae and E. cuniculi. We also present the first documented case of transcription of a transposable element in microsporidia.

Conclusion

Although E. aedis and A. locustae are distantly related, have very disparate life cycles and contain genomes estimated to be vastly different sizes, their patterns of transcription are similar. The architecture of the ancestral microsporidian genome is unknown, but the presence of genes in E. aedis that have not been found in other microsporidia suggests that extreme genome reduction and compaction is lineage specific and not typical of all microsporidia.