Flores Rachel L, Livingston Brian T
Department of Biological Sciences, California State University, 1250 Bellflower Blvd, Long Beach, CA, 90840, USA.
BMC Evol Biol. 2017 Jun 5;17(1):125. doi: 10.1186/s12862-017-0978-z.
Proteomic studies of skeletal proteins have revealed large, complex mixtures of proteins occluded within the mineral. Many skeletal proteomes contain rapidly evolving proteins with repetitive domains, further complicating our understanding. In echinoderms, proteomic analysis of the skeletal proteomes of mineralized tissues of the sea urchin Strongylocentrotus purpuratus prominently featured spicule matrix proteins with repetitive sequences linked to a C-type lectin domain. A comparative study of the brittle star Ophiocoma wendtii skeletal proteome revealed an order of magnitude fewer proteins containing C-type lectin domains. A number of other proteins conserved in the skeletons of the two groups were identified. Here we report the complete skeletal proteome of the sea star Patiria miniata and compare it to that of the other echinoderm groups.
We have identified eighty-five proteins in the P. miniata skeletal proteome. Forty-two percent of the proteins were determined to be homologous to proteins found in the S. purpuratus skeletal proteomes. An additional 34 % were from similar functional classes as proteins in the urchin proteomes. Thirteen percent of the P. miniata proteins had homologues in the O. wendtii skeletal proteome with an additional 29% showing similarity to brittle star skeletal proteins. The P. miniata skeletal proteome did not contain any proteins with C-lectin domains or with acidic repetitive regions similar to the sea urchin or brittle star spicule matrix proteins. MSP130 proteins were also not found. We did identify a number of proteins homologous between the three groups. Some of the highly conserved proteins found in echinoderm skeletons have also been identified in vertebrate skeletons.
The presence of proteins conserved in the skeleton in three different echinoderm groups indicates these proteins are important in skeleton formation. That a number of these proteins are involved in skeleton formation in vertebrates suggests a common origin for some of the fundamental processes co-opted for skeleton formation in deuterostomes. The proteins we identify suggest transport of proteins and calcium via endosomes was co-opted to this function in a convergent fashion. Our data also indicate that modifications to the process of skeleton formation can occur through independent co-option of proteins following species divergence as well as through domain shuffling.
对骨骼蛋白的蛋白质组学研究揭示了矿化组织中存在大量复杂的蛋白质混合物。许多骨骼蛋白质组包含具有重复结构域的快速进化的蛋白质，这进一步加深了我们理解的难度。在棘皮动物中，对紫海胆（Strongylocentrotus purpuratus）矿化组织的骨骼蛋白质组进行蛋白质组学分析，结果显示其骨针基质蛋白具有与C型凝集素结构域相连的重复序列。对脆星（Ophiocoma wendtii）骨骼蛋白质组的一项比较研究表明，含有C型凝集素结构域的蛋白质数量减少了一个数量级。还鉴定出了两组骨骼中保守的许多其他蛋白质。在此，我们报告了海星（Patiria miniata）的完整骨骼蛋白质组，并将其与其他棘皮动物群体的蛋白质组进行比较。
我们在小海星（P. miniata）的骨骼蛋白质组中鉴定出了85种蛋白质。其中42%的蛋白质被确定与在紫海胆（S. purpuratus）骨骼蛋白质组中发现的蛋白质同源。另外34%与海胆蛋白质组中的蛋白质属于相似的功能类别。小海星（P. miniata）的13%的蛋白质在脆星（O. wendtii）的骨骼蛋白质组中有同源物，另外29%与脆星的骨骼蛋白质相似。小海星（P. miniata）的骨骼蛋白质组不包含任何具有C型凝集素结构域或与海胆或脆星骨针基质蛋白相似的酸性重复区域的蛋白质。也未发现MSP130蛋白。我们确实鉴定出了三组之间的许多同源蛋白质。在棘皮动物骨骼中发现的一些高度保守的蛋白质在脊椎动物骨骼中也已被鉴定出来。
在三种不同的棘皮动物群体的骨骼中存在保守蛋白质，这表明这些蛋白质在骨骼形成中很重要。其中许多蛋白质参与脊椎动物的骨骼形成，这表明在脊椎动物中，一些被用于骨骼形成过程的基本过程有着共同的起源。我们鉴定出的蛋白质表明，通过内体运输蛋白质和钙以趋同的方式被用于这一功能。我们的数据还表明，骨骼形成过程的改变可以通过物种分化后蛋白质的独立选择以及结构域改组来实现。
