de la Fuente Mercedes, Novo Marta
Departamento de Ciencias y Técnicas Fisicoquímicas, Universidad Nacional de Educación a Distancia (UNED), Las Rozas, Spain.
Faculty of Biology, Biodiversity, Ecology and Evolution Department, Complutense University of Madrid, Madrid, Spain.
Front Physiol. 2022 Apr 13;13:817272. doi: 10.3389/fphys.2022.817272. eCollection 2022.
Small heat shock proteins (sHsps) are oligomeric stress proteins characterized by an α-crystallin domain (ACD). These proteins are localized in different subcellular compartments and play critical roles in the stress physiology of tissues, organs, and whole multicellular eukaryotes. They are ubiquitous proteins found in all living organisms, from bacteria to mammals, but they have never been studied in annelids. Here, a data set of 23 species spanning the annelid tree of life, including mostly transcriptomes but also two genomes, was interrogated and 228 novel putative sHsps were identified and manually curated. The analysis revealed very high protein diversity and showed that a significant number of sHsps have a particular dimeric architecture consisting of two tandemly repeated ACDs. The phylogenetic analysis distinguished three main clusters, two of them containing both monomeric sHsps, and ACDs located downstream in the dimeric sHsps, and the other one comprising the upstream ACDs from those dimeric forms. Our results support an evolutionary history of these proteins based on duplication events prior to the Spiralia split. Monomeric sHsps 76) were further divided into five subclusters. Physicochemical properties, subcellular location predictions, and sequence conservation analyses provided insights into the differentiating elements of these putative functional groups. Strikingly, three of those subclusters included sHsps with features typical of metazoans, while the other two presented characteristics resembling non-metazoan proteins. This study provides a solid background for further research on the diversity, evolution, and function in the family of the sHsps. The characterized annelid sHsps are disclosed as essential for improving our understanding of this important family of proteins and their pleotropic functions. The features and the great diversity of annelid sHsps position them as potential powerful molecular biomarkers of environmental stress for acting as prognostic tool in a diverse range of environments.
小分子热休克蛋白（sHsps）是一类以α-晶状体蛋白结构域（ACD）为特征的寡聚应激蛋白。这些蛋白定位于不同的亚细胞区室，在组织、器官和整个多细胞真核生物的应激生理学中发挥关键作用。它们是在从细菌到哺乳动物的所有生物体中都能找到的普遍存在的蛋白，但从未在环节动物中进行过研究。在此，对一个涵盖环节动物生命树的23个物种的数据集进行了分析，该数据集主要包括转录组，但也有两个基因组，共鉴定出228个新的假定sHsps并进行了人工整理。分析揭示了非常高的蛋白质多样性，并表明大量的sHsps具有由两个串联重复的ACD组成的特殊二聚体结构。系统发育分析区分出三个主要簇，其中两个簇既包含单体sHsps，也包含二聚体sHsps中位于下游的ACD，另一个簇包含那些二聚体形式中位于上游的ACD。我们的结果支持了基于螺旋动物门分化之前的复制事件的这些蛋白的进化历史。单体sHsps进一步分为五个亚簇。物理化学性质、亚细胞定位预测和序列保守性分析为这些假定功能组的区分要素提供了见解。引人注目的是，其中三个亚簇包含具有后生动物典型特征的sHsps，而另外两个亚簇呈现出类似于非后生动物蛋白的特征。这项研究为进一步研究sHsps家族的多样性、进化和功能提供了坚实的背景。已鉴定的环节动物sHsps对于增进我们对这个重要蛋白家族及其多效性功能的理解至关重要。环节动物sHsps的特征和巨大多样性使其成为环境应激潜在的强大分子生物标志物，可在各种环境中用作预后工具。
