Identification and functional characterization of first alpha‐2‐macroglobulin in sea cucumbers

Abstract

The broad‐spectrum protease inhibitor alpha‐2‐macroglobulin (α2M) is widely found in vertebrates and invertebrates. However, no research regarding α2M has been described in sea cucumbers to date. In this study, the first sea cucumber α2M named Stmα2M was identified from Stichopus monotuberculatus, a tropical species with high edible and economic values in Southern China. The Stmα2M cDNA is 5276 bp in length, containing a 5′‐untranslated region (UTR) of 279 bp, a 3′‐UTR of 344 bp and an open reading frame of 4653 bp that encodes a protein of 1550 amino acids. The Stmα2M possesses all the three characteristics of known α2M proteins, including the bait region domain, thioester domain and receptor‐binding domain. Higher levels of mRNA expression were noticed in intestine, respiratory tree, coelomocytes and tentacle of S. monotuberculatus. Transcriptional expression of Stmα2M showed the strongest response to lipopolysaccharides (LPS, 8.19‐fold up‐regulation) after 6 h post‐challenge in coelomocytes. In addition, the α2M activity was detected in S. monotuberculatus and protein activity of α2M increased remarkably at 6 h after LPS stimulation. As a whole, this study indicated that Stmα2M is an important immune‐related molecule, and the study on functions of Stmα2M may provide some new and valuable ideas for preventing and controlling diseases of cultured sea cucumbers.

Transcriptomic analysis of sea cucumber (Holothuria leucospilota) coelomocytes revealed the echinoderm cytokine response during immune challenge

“…The innate immunity of sea cucumber includes multiple immunerelated factors, such as, antimicrobial peptides (e.g. lectins, lysozyme, clotting protein and complement) [4,5], antimicrobial reactive oxygen species [6], pattern recognition receptors, apoptosis [7,8] and immune cytokines [9]. Sea cucumber has a cavity between its digestive tract and body wall that is filled with coelomic fluid and suspended coelomocytes that are similar to the hematocyts of vertebrates.…”

Comparative Characterization of Sequence Structure, Gene Expression, and Enzyme Activity of Alpha‐2‐macroglobulin between Stichopus monotuberculatus (Stichopodidae) and Holothuria atra (Holothuriidae)

“…LPS and Poly (I:C) are immunostimulants in previous studies (Ren et al 2015). According to our previous results, the highest expression of A 2 M mRNA was found in the intestine of S. monotuberculatus (Qian et al 2016a) while in the coelomocytes of H. atra (Qian et al 2016b). Thus, the changes of A 2 M transcript in the intestine of S. monotuberculatus and in the coelomocytes of H. atra were selected for challenge-induced expression analysis.…”

“…In our previous studies, LPS challenge caused a striking increase of A 2 M activity in the coelomic fluids of S. monotuberculatus (Qian et al 2016a), while a significant decrease of A 2 M activity was caused by Poly (I:C) in the coelomic fluids of H. atra (Qian et al 2016b). In order to gain more insights into the immune response of A 2 M, further studies on changes in activity levels of StmA 2 M and HaA 2 M were carried out by treatment of either Poly (I:C) or LPS, respectively.…”

“…According to our previous results, the highest expression of A 2 M mRNA was found in the intestine of S . monotuberculatus (Qian et al ) while in the coelomocytes of H . atra (Qian et al ).…”

“…In our previous studies, LPS challenge caused a striking increase of A 2 M activity in the coelomic fluids of S . monotuberculatus (Qian et al ), while a significant decrease of A 2 M activity was caused by Poly (I:C) in the coelomic fluids of H . atra (Qian et al ).…”