Mapping of the complement C1q binding site on Trichinella spiralis paramyosin

Abstract

BackgroundTrichinella spiralis is a tissue-dwelling parasite has developed the ability to evade the host immune attack to establish parasitism in a host. One of the strategies evolved by the nematode is to produce proteins that immunomodulate the host immune system. TsPmy is a paramyosin secreted by T. spiralis on the surface of larvae and adult worms that can interact with complement components C1q and C8/C9 to compromise their activation and functions. To better understand the mechanism of TsPmy involved in the C1q inactivation and immune evasion, the C1q-binding site on TsPmy was investigated.MethodsThe TsPmy C1q-binding site was investigated by sequential narrow-down fragment expression in bacteria and peptide binding screening. C1q binding activity was identified by Far-Western blotting and ELISA assays.ResultsAfter several runs of sequential fragment expression, the C1q binding site was narrowed down to fragments of N-terminal TsPmy226-280aa and TsPmy231-315aa, suggesting the final C1q binding site is probably located to TsPmy231-280aa. A total of nine peptides covering different amino acid sequences within TsPmy231-280aa were synthesized. The binding assay to C1q determined that only P2 peptide covering TsPmy241-280aa binds to C1q, indicating that the C1q binding domain may need both the linearized sequence and conformational structure required for binding to C1q. The binding of peptide P2 to C1q significantly inhibited both C1q-initiated complement classical activation and C1q-induced macrophage chemotaxis.ConclusionsThis study identifies the C1q binding site within TsPmy which provides helpful information for developing a vaccine against trichinellosis by targeting the C1q-binding activity of TsPmy.

Trichinella spiralis Paramyosin Induces Colonic Regulatory T Cells to Mitigate Inflammatory Bowel Disease

“…The adult worm extracts of T. spiralis also stimulated regulatory cytokines and reduced OVA-induced airway inflammation (Yuan et al, 2019). In an effort to identify the effective components in the nematode-secreted proteins that play immunomodulatory functions in host immune systems, it was found that paramyosin as a structural protein expressed on the surface and secreted products of T. spiralis larval and adult worms (TsPmy) is one of the major proteins involved in the immunomodulation of the host immune response through binding to human complement C1q (Sun et al, 2015;Wang et al, 2018) and C8/C9 (Zhang et al, 2011;Zhao et al, 2014) to inhibit complement response. The C9 binding domain of rTsPmy coupled with a membrane-bound signal reduced complement-related arthritis in a mouse model (Chen et al, 2020).…”

iTRAQ-based comparative proteomic analysis in different developmental stages ofEchinococcus granulosus

“…Paramyosin, also known as tropomyosin A, is the muscle constituent protein of invertebrates such as molluscs and annelids [ 9 ]. Studies have shown that paramyosin is expressed in the epidermis, subcutaneous tissues and organs of many parasites, and can also be secreted in vitro [ 60 ]. Pearce et al [ 44 ] obtained paramyosin from soluble adult worm antigen of Schistosoma mansoni by affinity chromatography, and preliminarily elucidated the cellular immune mechanism of this protein.…”

Identification of the complement 9‐binding protein in Setaria equina excretory‐secretory products

“…In H contortus and B malayi , the C3‐ and C1q‐binding proteins were identified as glyceraldehyde‐3‐phosphate dehydrogenase and calreticulin, respectively. Nevertheless, paramyosin which is located on the outer surface of Trichinella spiralis was found as C1q‐ and C9‐binding proteins . Generally, secretory products of parasitic helminthes had been known as anti‐inflammatory products .…”

“…Among the complement‐evasion strategies to escape the host immune attack, the capture of host complement components by the parasite proteins and then inactivating their functions is an evasion mechanism that is frequently adopted by many parasites during the establishment of parasitism . Paramyosin was found previously in Trichinella spiralis to bind C1q and C9 and inhibit the formation of membrane attack complex (MAC) . Furthermore, Brugia malayi calreticulin had been found to prevent classical complement pathway activation via its interaction with the first component C1q of the human host …”