Deng Cheng, Chen Haidi, Yang Na, Feng Yi, Hsueh Aaron J W
From the Jiangsu Key Laboratory for Biodiversity and Biotechnology, College of Life Sciences, Nanjing Normal University, Nanjing 210023, China and Program of Reproductive and Stem Cell Biology, Department of Ob/Gyn, Stanford University School of Medicine, Stanford, California 94305-5317.
From the Jiangsu Key Laboratory for Biodiversity and Biotechnology, College of Life Sciences, Nanjing Normal University, Nanjing 210023, China and.
J Biol Chem. 2015 Jul 24;290(30):18261-8. doi: 10.1074/jbc.M115.648238. Epub 2015 May 20.
Apela (APJ early endogenous ligand, also known as elabela or toddler) is a recently discovered peptide hormone. Based on genetic studies in zebrafish, apela was found to be important for endoderm differentiation and heart development during embryogenesis. Although common phenotypes of apela and APJ-null zebrafish during embryonic development suggested that apela interacts with the APJ receptor, kinetics of apela binding to APJ and intracellular signaling pathways for apela remain unknown. The role of apela in adults is also uncertain. Using a chimeric apela ligand, we showed direct binding of apela to APJ with high affinity (Kd = 0.51 nm) and the ability of apelin, the known peptide ligand for APJ, to compete for apela binding. Apela, similar to apelin, acts through the inhibitory G protein pathway by inhibiting forskolin-stimulated cAMP production and by inducing ERK1/2 phosphorylation. In adult rats, apela is expressed exclusively in the kidney, unlike the wide tissue distribution of apelin. In vivo studies demonstrated the ability of apela to regulate fluid homeostasis by increasing diuresis and water intake. Dose-response studies further indicated that apela induces 2- and 5-fold higher maximal responses than apelin in ERK1/2 phosphorylation and diuresis/water intake, respectively. After designing an apela antagonist, we further demonstrated the role of endogenous ligand(s) in regulating APJ-mediated fluid homeostasis. Our results identified apela as a potent peptide hormone capable of regulating fluid homeostasis in adult kidney through coupling to the APJ-mediated Gi signaling pathway.
Apela（APJ早期内源性配体，也称为elabela或toddler）是一种最近发现的肽类激素。基于斑马鱼的遗传学研究，发现Apela在胚胎发生过程中对内胚层分化和心脏发育很重要。尽管在胚胎发育过程中Apela和APJ基因敲除斑马鱼的常见表型表明Apela与APJ受体相互作用，但Apela与APJ的结合动力学以及Apela的细胞内信号通路仍不清楚。Apela在成体中的作用也不确定。使用嵌合Apela配体，我们证明了Apela与APJ具有高亲和力的直接结合（解离常数Kd = 0.51纳米），以及已知的APJ肽配体apelin竞争Apela结合的能力。与apelin类似，Apela通过抑制福斯高林刺激的环磷酸腺苷（cAMP）产生和诱导细胞外信号调节激酶1/2（ERK1/2）磷酸化，通过抑制性G蛋白途径发挥作用。在成年大鼠中，与apelin广泛的组织分布不同，Apela仅在肾脏中表达。体内研究证明了Apela通过增加利尿和水摄入来调节液体稳态的能力。剂量反应研究进一步表明，在ERK1/2磷酸化和利尿/水摄入方面，Apela分别比apelin诱导的最大反应高2倍和5倍。在设计出一种Apela拮抗剂后，我们进一步证明了内源性配体在调节APJ介导的液体稳态中的作用。我们的结果确定Apela是一种有效的肽类激素，能够通过与APJ介导的Gi信号通路偶联来调节成年肾脏中的液体稳态。
