The Complement System in Sea Urchins and the Evolution of the Vertebrate Complement Cascades

摘要本研究旨在了解紫海胆（Strongylocentrotus purpuratus）这一古老而原始的生物的补体系统，以阐明高等脊椎动物补体级联的起源和演化。研究者在海胆的免疫细胞中发现了两种可能的补体成分。一个基因编码的蛋白质（SpC3）与脊椎动物补体C3（高等脊椎动物补体级联的核心成分）具有显著的相似性，另一个基因编码的蛋白质（SpCR）具有相似的结构域或功能模块，这些功能模块是补体受体或补体调节蛋白的特征。本课题的研究旨在了解这一补体系统。完成sp3和SpCr基因的序列分析，并由此推断编码蛋白序列。这两个基因在海胆细胞和组织中的表达模式将被确定。还将检查体腔细胞对免疫挑战的基因和蛋白质表达的变化。实验将观察sp3是否作为调理蛋白，SpCR是否作为补体受体或补体调节蛋白。本提案旨在通过调查新发现的海胆补体系统来解决后口免疫的进化。该系统将进一步加深我们对海胆免疫反应机制的理解，并将有助于确定在高等脊椎动物中仍在运作的原始功能。＊＊＊

Abstract 9603086 Smith The aim of this investigation is to understand the complement system of the purple sea urchin, Strongylocentrotus purpuratus, an ancient and primitive organism, that may elucidate the origin and evolution of the complement cascade in higher vertebrates. This investigator has identified, in the immune cells of this sea urchin, two putative complement components. One is a gene encoding a protein (SpC3) with significant similarity to the vertebrate complement C3, the central component of the complement cascades in higher vertebrates, and the other gene codes for a protein (SpCR) with similar domains or functional modules that are characteristic of complement receptors or complement regulatory proteins. The research in this proposal is aimed at understanding this complement system. The sequence analysis of SpC3 and SpCr genes will be completed and from this the encoded protein sequences deduced. The expression patterns of these two genes in sea urchin cells and tissues will be determined. Changes in gene and protein expression in coelomocytes responding to immune challenges will also be examined. Experiments will be done to see whether SpC3 functions as an opsonin and SpCR functions as a complement receptor or a complement regulatory protein. This proposal is designed to address the evolution of deuterostome immunity through investigations of the newly identified sea urchin complement system. This system will further our understanding of the mechanisms involved in the sea urchin immune response and will help define the primitive functions that still operate in higher vertebrates. ***