Molecular mechanisms mediating stiffening in the mechanically adaptable connective tissues of sea cucumbers

Marie Bonneel,Elise Hennebert,A Sesilja Aranko,Dong Soo Hwang,Mathilde Lefevre,Valentine Pommier,Ruddy Wattiez,Jérôme Delroisse,Patrick Flammang

doi:10.1016/j.matbio.2022.02.006

Marie Bonneel, Elise Hennebert + Show 7 more

Open Access

https://doi.org/10.1016/j.matbio.2022.02.006

Copy DOI

Abstract

Mutable collagenous tissues (MCTs) from echinoderms (e.g., sea stars, sea urchins) possess the remarkable ability to change their mechanical properties rapidly and reversibly thanks to the release of effector molecules regulating the number of cross-links between collagen fibrils. Among these effector molecules, tensilin has been identified as a stiffening factor in sea cucumber MCTs. Since its discovery and description twenty years ago, tensilin orthologs have been identified in a few sea cucumber species but no novel information about its molecular mode of action has been reported. In this study, using a combination of in silico analyses, we identified the tensilin present in the dermis of Holothuria forskali, Hf-(D)Tensilin. Anti-peptide antibodies showed that this protein is localised in the secretory granules of type 2 juxtaligamental-like cells, a MCT specific cell type. We then used the bacterium E. coli to produce recombinantly Hf-(D)Tensilin and confirmed its stiffening effect on pieces of the dermis and its aggregation effect on collagen fibrils extracted from the sea cucumber dermis. To investigate how tensilin can cross-bridge collagen fibrils, truncated recombinant tensilins were also produced and used in combination with various compounds. Results suggest that two types of interactions contribute to the aggregation effect of tensilin on the fibrils: (1) the N-terminal NTR TIMP like domain of the protein interacts strongly with sulfated GAGs attached to the surface of the collagen fibrils, and (2) the C-terminal part of the protein is involved in its dimerisation/oligomerisation through ionic but possibly also cation-π and hydrophobic interactions.

Highlights

Most structural materials from living organisms are composites made up of stiff fibres embedded in a softer non-fibrous matrix
Using the published protein sequences of tensilins from A. japonicus, from the dermis of C. frondosa, and from the Cuvierian tubules of H. forskali, a tBLASTn search was performed in the body wall transcriptome of H. forskali 26 to look for transcripts encoding tensilin-like proteins
We performed a multiple amino acid alignment and maximum-likelihood phylogenetic analyses with the sequences from this group as well as with other A. japonicus sequences used in the CLANS analysis (A. japonicus being the only sea cucumber species with an available annotated genome, it gives an overview of the diversity of genes coding for Tissue inhibitors of metalloproteinases (TIMPs)-like proteins in sea cucumbers)

Summary

Introduction

Most structural materials from living organisms (e.g., the cell-wall in plants, the cuticle in insects, and the tendons and ligaments in mammals) are composites made up of stiff fibres embedded in a softer non-fibrous matrix In bilaterian animals, this structural function is generally accomplished by connective tissues, which are complex fibre-reinforced composite structures [1,2]. The proportions of the different ECM components as well as the length, density and orientation of the fibres determine the mechanical properties of the connective tissues (e.g., skin and artery are more pliant, tendons are stronger, etc.) 1-3 In adult tissues, these properties are constant and stable except in case of pathology or ageing [3,4,5]

Methods

Results

Conclusion