INRAE, Université de Tours, BOA, Nouzilly, France.
Department of Innovation in Medical Education, Faculty of Medicine, University of Ottawa, Ottawa, ON, Canada.
Front Immunol. 2022 Jul 27;13:946428. doi: 10.3389/fimmu.2022.946428. eCollection 2022.
The calcitic avian eggshell provides physical protection for the embryo during its development, but also regulates water and gaseous exchange, and is a calcium source for bone mineralization. The calcified eggshell has been extensively investigated in the chicken. It is characterized by an inventory of more than 900 matrix proteins. In addition to proteins involved in shell mineralization and regulation of its microstructure, the shell also contains numerous antimicrobial proteins and peptides (AMPPs) including lectin-like proteins, Bacterial Permeability Increasing/Lipopolysaccharide Binding Protein/PLUNC family proteins, defensins, antiproteases, and chelators, which contribute to the innate immune protection of the egg. In parallel, some of these proteins are thought to be crucial determinants of the eggshell texture and its resulting mechanical properties. During the progressive solubilization of the inner mineralized eggshell during embryonic development (to provide calcium to the embryo), some antimicrobials may be released simultaneously to reinforce egg defense and protect the egg from contamination by external pathogens, through a weakened eggshell. This review provides a comprehensive overview of the diversity of avian eggshell AMPPs, their three-dimensional structures and their mechanism of antimicrobial activity. The published chicken eggshell proteome databases are integrated for a comprehensive inventory of its AMPPs. Their biochemical features, potential dual function as antimicrobials and as regulators of eggshell biomineralization, and their phylogenetic evolution will be described and discussed with regard to their three-dimensional structural characteristics. Finally, the repertoire of chicken eggshell AMPPs are compared to orthologs identified in other avian and non-avian eggshells. This approach sheds light on the similarities and differences exhibited by AMPPs, depending on bird species, and leads to a better understanding of their sequential or dual role in biomineralization and innate immunity.
碳酸钙质的禽类蛋壳在胚胎发育过程中为胚胎提供物理保护，但也调节水和气体交换，并且是骨骼矿化的钙源。钙化蛋壳在鸡中已被广泛研究。其特征是含有超过 900 种基质蛋白。除了参与壳矿化和调节其微观结构的蛋白质外，壳还含有许多抗菌蛋白和肽（AMPPs），包括凝集素样蛋白、细菌通透性增加/脂多糖结合蛋白/PLUNC 家族蛋白、防御素、抗蛋白酶和螯合剂，有助于鸡蛋的先天免疫保护。平行地，其中一些蛋白质被认为是蛋壳质地及其机械性能的关键决定因素。在胚胎发育过程中，内部矿化蛋壳逐渐溶解（为胚胎提供钙）的同时，一些抗菌物质可能同时释放出来，通过削弱蛋壳来加强鸡蛋的防御能力并保护鸡蛋免受外部病原体的污染。这篇综述全面概述了禽类蛋壳 AMPPs 的多样性、它们的三维结构及其抗菌活性的机制。整合了已发表的鸡蛋壳蛋白质组数据库，以全面盘点其 AMPPs。描述和讨论了它们的生化特征、作为抗菌剂和蛋壳生物矿化调节剂的潜在双重功能，以及它们的系统发育进化，同时考虑到它们的三维结构特征。最后，将鸡蛋壳 AMPPs 的特征与在其他禽类和非禽类蛋壳中鉴定的同源物进行了比较。这种方法揭示了 AMPPs 取决于鸟类物种而表现出的相似性和差异性，并使我们更好地理解它们在生物矿化和先天免疫中的顺序或双重作用。
