Abstract：
Growth hormone-releasing hormone (GHRH) has been widely shown to stimulate growth hormone (GH) production via binding to GHRH receptor GHRHR in various species of vertebrates, but information regarding the functional roles of GHRH and GHRHR in the protochordate amphioxus remains rather scarce. We showed here that two mature peptides, BjGHRH-1 and BjGHRH-2, encoded by BjGHRH precursor, and a single BjGHRHR protein were identified in the amphioxus Branchiostoma. japonicum. Like the distribution profiles of vertebrate GHRHs and GHRHRs, both the genes Bjghrh and Bjghrhr were widely expressed in the different tissues of amphioxus, including in the cerebral vesicle, Hatschek\'s pit, neural tube, gill, hepatic caecum, notochord, testis and ovary. Moreover, both BjGHRH-1 and BjGHRH-2 interacted with BjGHRHR, and triggered the cAMP/PKA signal pathway in a dose-dependent manner. Importantly, BjGHRH-1 and BjGHRH-2 were both able to activate the expression of GH-like gene in the cells of Hatschek\'s pit. These indicate that a functional vertebrate-like GHRH-GHRHR axis had already emerged in amphioxus, which is a seminal innovation making physiological divergence including reproduction, growth, metabolism, stress and osmoregulation possible during the early evolution of vertebrates.
摘要：
生长激素释放激素（GHRH）已被广泛证明可以通过与各种脊椎动物的GHRH受体GHRHR结合来刺激生长激素（GH）的产生。但是有关GHRH和GHRHR在原索文昌鱼中的功能作用的信息仍然很少。我们在这里展示了两种成熟的肽，BjGHRH-1和BjGHRH-2，由BjGHRH前体编码，并在文昌鱼Branchiostoma中鉴定出单个BjGHRHR蛋白。日本。像脊椎动物GHRHs和GHRHRs的分布特征一样，Bjghrh和Bjghrhr基因在文昌鱼的不同组织中广泛表达，包括在脑囊泡中，Hatschek的坑,神经管,吉尔,肝盲肠,脊索,睾丸和卵巢。此外，BjGHRH-1和BjGHRH-2都与BjGHRHR相互作用，并以剂量依赖性方式触发cAMP/PKA信号通路。重要的是,BjGHRH-1和BjGHRH-2均能够激活Hatschek坑细胞中GH样基因的表达。这些表明，在文昌鱼中已经出现了功能性脊椎动物状的GHRH-GHRHR轴，这是一项开创性的创新，使得包括生殖在内的生理差异，增长,新陈代谢，脊椎动物早期进化过程中可能存在的压力和渗透调节。
