Discovery of a Novel Functional Leptin Protein (LEP) in Zebra Finches: Evidence for the Existence of an Authentic Avian Leptin Gene Predominantly Expressed in the Brain and Pituitary
Discovery of a Novel Functional Leptin Protein (LEP) in Zebra Finches: Evidence for the Existence of an Authentic Avian Leptin Gene Predominantly Expressed in the Brain and Pituitary
复制标题
在斑胸草雀中发现一种新型功能性瘦素蛋白（LEP）：证明存在主要在大脑和垂体中表达的真正鸟类瘦素基因的证据。
DOI：
10.1210/en.2014-1084
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发表时间：
2014-09-01
期刊：
影响因子：
4.8
通讯作者：
Wang, Yajun
中科院分区：
文献类型：
--
作者：
Huang, Guian;Li, Juan;Wang, Yajun
瘦素（Leptin，LEP）在脊椎动物（包括鸟类）的能量平衡中起重要作用。然而，它仍然是一个悬而未决的问题，是否真正的“LEP基因”存在于鸟类和功能。在这里，我们确定和特点的LEP基因（斑胸草雀LEP [zbLEP]）编码一个172个氨基酸的前体在斑胸草雀。尽管zbLEP与人和小鼠LEP显示有限的氨基酸序列同一性（26%-29%），但同线性分析证明zbLEP与哺乳动物LEP是直向同源的。利用pAH 32荧光素酶报告系统和Western blot分析，我们证明了重组zbLEP蛋白可以有效地激活雀和鸡LEP受体（zbLEPR; cLEPR）在人胚肾293细胞中表达，并增强信号转导和转录激活因子3磷酸化，进一步表明zbLEP是鸟类LEPR的功能配体。有趣的是，定量实时RT-PCR显示，zbLEP mRNA几乎只在垂体和各种脑区表达，但在脂肪组织和肝脏中检测不到，而zbLEPR mRNA在成年雀组织中广泛表达，在垂体中有丰富的表达，这意味着与哺乳动物LEP不同，雀LEP可能不作为脂肪细胞来源的信号来控制能量平衡。与雀类一样，在虎皮鹦鹉基因组中也发现了与zbLEP高度同源的LEP。引人注目的是，雀类和虎皮鹦鹉LEPs与先前报道的鸡LEP（cLEP）几乎没有同源性，这表明所谓的cLEP是不正确的。总的来说，我们的数据提供了令人信服的证据，存在一个真实的功能LEP在鸟类物种，并建议脑和垂体衍生LEP在脊椎动物中发挥的重要作用。
Leptin (LEP) is reported to play important roles in controlling energy balance in vertebrates, including birds. However, it remains an open question whether an authentic "LEP gene" exists and functions in birds. Here, we identified and characterized a LEP gene (zebra finch LEP [zbLEP]) encoding a 172-amino acid precursor in zebra finches. Despite zbLEP showing limited amino acid sequence identity (26%-29%) to human and mouse LEPs, synteny analysis proved that zbLEP is orthologous to mammalian LEP. Using a pAH32 luciferase reporter system and Western blot analysis, we demonstrated that the recombinant zbLEP protein could potently activate finch and chicken LEP receptors (zbLEPR; cLEPR) expressed in human embryonic kidney 293 cells and enhance signal transducer and activator of transcription 3 phosphorylation, further indicating that zbLEP is a functional ligand for avian LEPRs. Interestingly, quantitative real-time RT-PCR revealed that zbLEP mRNA is expressed nearly exclusively in the pituitary and various brain regions but undetectable in adipose tissue and liver, whereas zbLEPR mRNA is widely expressed in adult finch tissues examined with abundant expression noted in pituitary, implying that unlike mammalian LEP, finch LEP may not act as an adipocyte-derived signal to control energy balance. As in finches, a LEP highly homologous to zbLEP was also identified in budgerigar genome. Strikingly, finch and budgerigar LEPs show little homology with chicken LEP (cLEP) previously reported, suggesting that the so-called cLEP is incorrect. Collectively, our data provide convincing evidence for the existence of an authentic functional LEP in avian species and suggest an important role of brain- and pituitary-derived LEP played in vertebrates.