Red-spotted grouper (Epinephelus akaara) is one of the high economic value grouper species, however, the knowledge regarding its growth is limited. In this study, full-length cDNAs of growth hormone (gh) and its receptors (ghr1 and ghr2) were cloned from the pituitary and liver of red-spotted grouper, respectively. Tissue distribution analysis showed that gh mRNA was predominantly expressed in the pituitary. ghr1 mRNA was highly expressed in the liver, muscle, fat and gonad, while ghr2 mRNA expression was ubiquitously high in the peripheral tissues. However, the mRNA expression of both ghr isoforms was relatively low in the central nervous system. Secretory recombinant grouper GH (rgGH) was expressed in yeast Pichia pastoris and verified. HEK293T cells transiently transfected with the GHR isoforms were used to elucidate the receptor-mediated signaling pathways related to growth regulation. rgGH activated rapid phosphorylation of Janus kinase 2, signal transducer and activator of transcription 5 (STAT5) and extracellular signal-regulated protein kinase 1/2 through GHR1, but only STAT5 was phosphorylated via GHR2. rgGH strongly activated STAT5 phosphorylation and significantly stimulated ghr1, ghr2 and insulin-like growth factor (igf1, igf2) mRNA expression in primary cultured hepatocytes. Data showed that the recombinant protein rgGH played effects on igf1/2 mRNA expression via GHR-mediated signaling pathways. Our findings provide essential information about GH and GHRs characteristics in red-spotted grouper.

红斑石斑鱼（Epinephelus akaara）是具有较高经济价值的石斑鱼种类之一，但是，有关其生长的知识有限。在这项研究中，分别从红斑石斑鱼的垂体和肝脏中克隆了生长激素（gh）及其受体（ghr1和ghr2）的全长cDNA 。组织分布分析表明，gh mRNA主要在垂体中表达。ghr1 mRNA在肝脏，肌肉，脂肪和性腺中高表达，而ghr2 mRNA在周围组织中普遍高表达。然而，两个ghr的mRNA表达中枢神经系统的亚型相对较低。分泌重组石斑鱼GH（rgGH）在酵母毕赤酵母中表达并得到验证。用GHR亚型瞬时转染的HEK293T细胞用于阐明与生长调节相关的受体介导的信号通路。rgGH通过GHR1激活了Janus激酶2的快速磷酸化，信号转导和转录激活剂5（STAT5）和细胞外信号调节蛋白激酶1/2通过GHR1进行了磷酸化，但只有STAT5通过GHR2进行了磷酸化。rgGH强烈激活STAT5磷酸化并显着刺激ghr1，ghr2和胰岛素样生长因子（igf1，igf2）在原代培养的肝细胞中的mRNA表达。数据显示重组蛋白rgGH通过GHR介导的信号通路对igf1 / 2 mRNA表达产生影响。我们的发现提供了有关红斑石斑鱼GH和GHRs特征的重要信息。