Kawada Tsuyoshi, Sekiguchi Toshio, Sakai Tsubasa, Aoyama Masato, Satake Honoo
Suntory Institute for Bioorganic Research, 1-1-1 Wakayamadai, Shimamoto, Mishima, Osaka 618-8503, Japan.
Zoolog Sci. 2010 Feb;27(2):134-53. doi: 10.2108/zsj.27.134.
The critical phylogenetic position of ascidians leads to the presumption that neuropeptides and hormones in vertebrates are highly likely to be evolutionarily conserved in ascidians, and the cosmopolitan species Ciona intestinalis is expected to be an excellent deuterostome Invertebrate model for studies on neuropeptides and hormones. Nevertheless, molecular and functional characterization of Ciona neuropeptides and hormone peptides was restricted to a few peptides such as a cholecystokinin (CCK)/gastrin peptide, cionin, and gonadotropin-releasing hormones (GnRHs). In the past few years, mass spectrometric analyses and database searches have detected Ciona orthologs or prototypes of vertebrate peptides and their receptors, including tachykinin, insulin/relaxin, calcitonin, and vasopressin. Furthermore, studies have shown that several Ciona peptides, including vasopressin and a novel GnRH-related peptide, have acquired ascidian-specific molecular forms and/or biological functions. These findings provided indisputable evidence that ascidians, unlike other invertebrates (including the traditional protostome model animals), possess neuropeptides and hormone peptides structurally and functionally related to vertebrate counterparts, and that several peptides have uniquely diverged in ascidian evolutionary lineages. Moreover, recent functional analyses of Ciona tachykinin in the ovary substantiated the novel tachykininergic protease-assoclated oocyte growth pathway, which could not have been revealed in studies on vertebrates. These findings confirm the outstanding advantages of ascidians in understanding the neuroscience, endocrinology, and evolution of vertebrate neuropeptides and hormone peptides. This article provides an overview of basic findings and reviews new knowledge on ascidian neuropeptides and hormone peptides.
海鞘关键的系统发育地位使得人们推测，脊椎动物中的神经肽和激素极有可能在海鞘中进化保守，而世界性物种玻璃海鞘有望成为研究神经肽和激素的优秀后口动物无脊椎动物模型。然而，玻璃海鞘神经肽和激素肽的分子及功能特征研究仅限于少数几种肽，如胆囊收缩素（CCK）/胃泌素肽、海鞘素和促性腺激素释放激素（GnRHs）。在过去几年中，质谱分析和数据库搜索已检测到玻璃海鞘中脊椎动物肽及其受体的直系同源物或原型，包括速激肽、胰岛素/松弛素、降钙素和血管加压素。此外，研究表明，包括血管加压素和一种新型GnRH相关肽在内的几种玻璃海鞘肽已获得了海鞘特有的分子形式和/或生物学功能。这些发现提供了无可争议的证据，表明与其他无脊椎动物（包括传统的原口动物模式动物）不同，海鞘拥有在结构和功能上与脊椎动物对应物相关的神经肽和激素肽，并且几种肽在海鞘进化谱系中发生了独特的分化。此外，最近对玻璃海鞘卵巢中速激肽的功能分析证实了新型速激肽能蛋白酶相关的卵母细胞生长途径，这在脊椎动物研究中无法揭示。这些发现证实了海鞘在理解脊椎动物神经肽和激素肽神经科学、内分泌学及进化方面的突出优势。本文概述了关于海鞘神经肽和激素肽的基本发现，并综述了新知识。
