The Origin and Evolution of Antistasin-like Proteins in Leeches (Hirudinida, Clitellata)

Abstract

Bloodfeeding is employed by many parasitic animals and requires specific innovations for efficient feeding. Some of these innovations are molecular features that are related to the inhibition of hemostasis. For example, bloodfeeding insects, bats and leeches release proteins with anticoagulatory activity through their salivary secretions. The antistasin-like protein family, composed of serine protease inhibitors with one or more antistasin-like domains, is tightly linked to inhibition of hemostasis in leeches. However, this protein family has been recorded also in non-bloodfeeding invertebrates, such as cnidarians, molluscs, polychaetes and oligochaetes. The present study aims to: (1) root the antistasin-like gene tree and delimit the major orthologous groups, (2) identify potential independent origins of salivary proteins secreted by leeches and (3) identify major changes in domain and/or motif structure within each orthologous group. Five clades containing leech antistasin-like proteins are distinguishable through rigorous phylogenetic analyses based on nine new transcriptomes and a diverse set of comparative data: the trypsin + leukocyte elastase inhibitors clade, the antistasin clade, the therostasin clade and two additional, unnamed clades. The antistasin-like gene tree supports multiple origins of leech antistasin-like proteins due to the presence of both leech and non-leech sequences in one of the unnamed clades, but a single origin of factor Xa and trypsin + leukocyte elastase inhibitors. This is further supported by three sequence motifs that are exclusive to antistasins, the trypsin + leukocyte elastase inhibitor clade and the therostasin clade, respectively. We discuss the implications of our findings for the evolution of this diverse family of leech anticoagulants.

Evolution, Expression Patterns, and Distribution of Novel Ribbon Worm Predatory and Defensive Toxins

“…These proteins have been reported to mediate several biological functions associated with envenomation including platelet aggregation and inflammation, as well as mitogenic, chemotactic, and cytotoxic activities ( Edo et al 2012 ; Sartim and Sampaio 2015 ). We also identified putative predatory toxins with antistasin-like domains ( table 1 , supplementary file S4, Supplementary Material online), which are common anticoagulants in leech saliva and have been also recorded from other nonblood-feeding invertebrates such as cnidarians and mollusks where they may act as modulators of the immune response ( Iwama et al 2021 ). To provide more evidence about the toxic nature and potential predatory role of these putative toxins, we looked at their spatial distribution within the A. valida proboscis tissue by MALDI-IMS.…”

Venomous Noodles: evolution of toxins in Nemertea through positive selection and gene duplication

“…, no anticoagulant motifs (obtained from Iwama et al 2021) were found on the Antistasin sequences. In non-blood-feeding invertebrates, antistasin and proteins with similar domains are thought to have a role in immune responses, though their role remains unclear (Iwama et al 2021).…”

“…, no anticoagulant motifs (obtained from Iwama et al 2021) were found on the Antistasin sequences. In non-blood-feeding invertebrates, antistasin and proteins with similar domains are thought to have a role in immune responses, though their role remains unclear (Iwama et al 2021). Verdes et al (2022) found antistasin in the proboscis of the hoplonemertean Antarctonemertes valida, in which it likely is a predation toxin.…”

Let’s end taxonomic blank slates with molecular morphology

“…Even more proteins have been assayed for their functionality. Protein functionality is often as distinctive as morphology, such as for leech anticoagulants that are often highly distinctive for species or lineages (Iwama et al, 2021(Iwama et al, , 2022.…”