Molecular characterization and functional analysis of the Schistosoma mekongi Ca2+-dependent cysteine protease (calpain)

Abstract

Background Schistosoma mekongi , which causes schistosomiasis in humans, is an important public health issue in Southeast Asia. Treatment with praziquantel is the primary method of control but emergence of praziquantel resistance requires the development of alternative drugs and vaccines. Calcium-dependent cysteine protease (calpain) is a novel vaccine candidate that has been studied in S. mansoni , S. japonicum , and protozoans including malaria, leishmania and trypanosomes. However, limited information is available on the properties and functions of calpain in other Schistosoma spp., including S. mekongi . In this study, we functionally characterized calpain 1 of S. mekongi (SmeCalp1). Results Calpain 1 of S. mekongi was obtained from transcriptomic analysis of S. mekongi ; it had the highest expression level of all isoforms tested and was predominantly expressed in the adult male. SmeCalp1 cDNA is 2274 bp long and encodes 758 amino acids, with 85% to 90% homology with calpains in other Schistosoma species. Recombinant SmeCalp1 (rSmeCalp1), with a molecular weight of approximately 86.7 kDa, was expressed in bacteria and stimulated a marked antibody response in mice. Native SmeCalp1 was detected in crude worm extract and excretory-secretory product, and it was mainly localized in the tegument of the adult male; less signal was detected in the adult female worm. Thus, SmeCalp1 may play a role in surface membrane synthesis or host–parasite interaction. We assessed the protease activity of rSmeCalp1 and demonstrated that rSmeCalp1 could cleave the calpain substrate N -succinyl-Leu-Leu-Val-Tyr-7-amino-4-methylcoumarin, that was inhibited by calpain inhibitors (MDL28170 and E64c). Additionally, rSmeCalp1 could degrade the biological substrates fibronectin (blood clotting protein) and human complement C3, indicating important roles in the intravascular system and in host immune evasion. Conclusions SmeCalp1 is expressed on the tegumental surface of the parasite and can cleave host defense molecules; thus, it might participate in growth, development and survival during the entire life-cycle of S. mekongi . Information on the properties and functions of SmeCalp1 reported herein will be advantageous in the development of effective drugs and vaccines against S. mekongi and other schistosomes. Electronic supplementary material The online version of this article (10.1186/s13071-019-3639-9) contains supplementary material, which is available to authorized users.

Eudiplozoon nipponicum (Monogenea, Diplozoidae) and its adaptation to haematophagy as revealed by transcriptome and secretome profiling

“…Supporting the protein degradation role played by the proteasome, our analysis shows that genes associated with the metallo peptidase family M67, which plays a critical role in deubiquitination of proteins, are also highly transcribed. Abundant transcription of genes associated with families Serine S1 (chymotrypsin family; PA clan) and Cysteine C2 (calpain family; CA clan) similarly support critical processes such as development and digestion [ 36 ] (family Serine S1), as well as signal transduction, cellular differentiation, cytoskeletal remodelling, and vesicular trafficking (family Cysteine C2) [ 37 ].…”

“…We also found a number of transcripts encoding calcium-dependent, non-lysosomal calpain-like proteases ( n = 10; 354.97 TPM), which cleave the blood-clotting fibronectin and thereby facilitate parasite feeding [ 37 , 51 ]. Cathepsin D aspartic endopeptidase ( n = 5; 314.49 TPM) and aminopeptidases that use a metal ligand within their active site ( n = 12; 103.12 TPM), such as aminopeptidase P3 (also known as Xaa-Pro aminopeptidase) and aminopeptidase A (or glutamyl aminopeptidase), also probably play a role in blood digestion, although not to the same extent as similar molecules in other haematophagous ectoparasites, such as ticks.…”

Scoping review of distribution models for selected Amblyomma ticks and rickettsial group pathogens

“…For vector-borne disease SDMs, records of vector or pathogen presence (either the vector, the pathogen, the vector and pathogen, or even simply human case data) are often used as proxies for risk of exposure, and therefore transmission. Species distribution models have been used in a risk mapping capacity for many vector-borne disease systems, spanning a range of pathogens vectored by arthropods including mosquitoes, gnats, phlebotomine flies, fleas, triatomine bugs, and ticks ( Carvalho et al, 2015 ; Lippi et al, 2019 ; Peterson et al, 2002 ; Crkvencic & Šlapeta, 2019 ; Sloyer et al, 2019 ). This framework is particularly useful in determining species limits for vectored transmission owing to the very close relationships between ectotherm life histories, pathogen replication, and environmental drivers such a temperature.…”

In silico characterisation of the complete Ly6 protein family in Fasciola gigantica supported through transcriptomics of the newly-excysted juveniles

“…Also represented among the EF-hand domain proteins are the calpains, a family of cysteine proteases which have been highlighted as potential vaccine candidates in schistosomes. 50,57 Two calpains of F. hepatica have previously been identified using 'omics data, while F. gigantica orthologues remain formally unidentified. 18 While EF-hand domains are not exclusive to these two families, putative annotation of the 109 EF-hand transcripts revealed the presence of 13 tegument antigens and 5 calpains, indicating the potential for family expansion and isoform discovery in F. gigantica using this transcriptome.…”