|
|
|
Bioactive Apela/ELABELA/Toddler peptide |
|
activator of APJ/Apelin receptor signaling, promotes gestrulation movements |
ELABELA (ELA) is a novel hormone consisting of 32 amino acid peptides found in humans as well as other vertebrates and is considered to play an important role in the circulatory system through the apelin receptor (APJ). However, whether ELA also acts in the central nervous system remains unknown. Here, we show that ELA functions as an anorexigenic hormone in adult mouse brain. An intracerebroventricular injection of ELA reduces food intake and activates arginine vasopressin (AVP) and corticotropin-releasing hormone (CRH) neurons in the paraventricular nucleus (PVN), a hypothalamic region that regulates food intake. Cytosolic calcium ([Ca]i) measurement shows that ELA dose dependently increases [Ca]i in single AVP and CRH-immunoreactive neurons isolated from the PVN. Our data suggest that ELA functions as an anorexigenic hormone through activation of AVP and CRH neurons in the PVN.
Neuroreport. 2015 Sep 30;26(14):820-6. doi: 10.1097/WNR.0000000000000431.
We report here the discovery and characterization of a gene, ELABELA (ELA), encoding a conserved hormone of 32 amino acids. Present in human embryonic stem cells, ELA is expressed at the onset of zebrafish zygotic transcription and is ubiquitous in the naive ectodermal cells of the embryo. Using zinc-finger-nuclease-mediated gene inactivation in zebrafish, we created an allelic series of ela mutants. ela null embryos have impaired endoderm differentiation potential marked by reduced gata5 and sox17 expression. Loss of Ela causes embryos to develop with a rudimentary heart or no heart at all, surprisingly phenocopying the loss of the apelin receptor (aplnr), which we show serves as Ela's cognate G protein-coupled receptor. Our results reveal the existence of a peptide hormone, ELA, which, together with APLNR, forms an essential signaling axis for early cardiovascular development.
Chng SC., et. al., Developmental Cell, 27, 1-9; 2013
ELABELA (ELA) was recently discovered as a novel endogenous ligand of the apelin receptor (APJ), a G protein-coupled receptor. ELA signaling was demonstrated to be crucial for normal heart and vasculature development during embryogenesis. We delineate here ELA's structure-activity relationships and report the identification of analogue 3 (ELA(19-32)), a fragment of ELA that binds to APJ, activates the Gαi1 and β-arrestin-2 signaling pathways and induces receptor internalization similarly to its parent endogenous peptide. An alanine scan performed on 3 revealed that the C-terminal residues are critical for binding to APJ and signaling. Finally, using isolated-perfused hearts and in vivo hemodynamic and echocardiographic measurements, we demonstrate that ELA and 3 both reduce arterial pressure and exert positive inotropic effects on the heart. Altogether, these results present ELA and 3 as potential therapeutic options in managing cardiovascular diseases.
Murza A, Sainsily X, Coquerel D et al., J Med Chem. 2016 Mar 17. [Epub ahead of print]
The G protein-coupled apelin receptor regulates important processes of the cardiovascular homeostasis, including cardiac development, cardiac contractility, and vascular tone. Most recently, a novel endogenous peptide ligand for the apelin receptor was identified in zebrafish, and it was named apela/elabela/toddler. The peptide was originally considered as an exclusively embryonic regulator, and so far its function in the adult organism remains elusive. We show here that apela is predominantly expressed in the non-cardiomyocyte fraction in the adult rodent heart. We also provide evidence that apela binds to apelin receptors in the heart. Using isolated adult rat hearts, we demonstrate, that just like the fellow receptor agonist apelin, apela increases cardiac contractility and induces coronary vasodilation already in the nanomolar level. The inotropic effect, as revealed by Western blot analysis, is accompanied by a significant increase in extracellular signal-regulated kinase (ERK) 1/2 phosphorylation. Pharmacological inhibition of ERK1/2 activation markedly attenuates the apela-induced inotropy. Analysis of samples from infarcted mouse hearts showed that expression of both apela and apelin receptor is induced in failing mouse hearts and correlate with left ventricular ejection fraction. Hence, we conclude that apela is present in the adult heart, is upregulated in post-infarction cardiac remodeling, and increases cardiac contractility in an ERK1/2-dependent manner.
Apelin and its G protein-coupled receptor (GPCR) have emerged as a key signalling pathway in the cardiovascular system. The peptide is a potent inotropic agent and vasodilator. Remarkably, a peptide, Elabela/Toddler, that has little sequence similarity to apelin, has been proposed as a second endogenous apelin receptor ligand and is encoded by a gene from a region of the genome previously classified as 'non-coding'. Apelin is downregulated in pulmonary arterial hypertension and heart failure. To replace the missing endogenous peptide, 'biased' apelin agonists have been designed that preferentially activate G protein pathways, resulting in reduced β-arrestin recruitment and receptor internalisation, with the additional benefit of attenuating detrimental β-arrestin signalling. Proof-of-concept studies support the clinical potential for apelin receptor biased agonists.
Yang P, Maguire JJ, Davenport AP, Trends Pharmacol Sci. 2015 Jul 1. pii: S0165-6147(15)00117-0. doi: 10.1016/j.tips.2015.06.002. [Epub ahead of print]
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=0.51nM) 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 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.
This article used Phoenix's ELA products.
Deng C, Chen H, Yang N et al., J Biol Chem. 2015 May 20. pii: jbc.M115.648238. [Epub ahead of print]
A key step in the de novo formation of the embryonic vasculature is the migration of endothelial precursors, the angioblasts, to the position of the future vessels. To form the first axial vessels, angioblasts migrate towards the midline and coalesce underneath the notochord. Vascular endothelial growth factor (Vegf) has been proposed to serve as a chemoattractant for the angioblasts and to regulate this medial migration. Here we challenge this model and instead demonstrate that angioblasts rely on their intrinsic expression of Apelin receptors (Aplr, APJ) for their migration to the midline. We further show that during this angioblast migration Apelin receptor signaling is mainly triggered by the recently discovered ligand Elabela (Ela). As neither of the ligands Ela or Apelin (Apln) nor their receptors have previously been implicated in regulating angioblast migration, we hereby provide a novel mechanism for regulating vasculogenesis, with direct relevance to physiological and pathological angiogenesis.
Helker CS, Schuermann A, Pollmann C et al., Elife. 2015 May 27;4. doi: 10.7554/eLife.06726. [Epub ahead of print]
Introduction: ELABELA/Toddler (ELA) (a.k.a. Ende/APELA), a recently identified peptide from a previously designated non-coding region, is expressed in human stem cells and is reported to regulate zebrafish cardiac development. Hearts fail to develop after ELA gene deletion, phenocopying apelin receptor knock-outs. Dibasic cleavage sites predict the expression of 3 isoforms; ELA-32, ELA-21 and ELA-11. Binding of ELA to the human apelin receptor, expression of ELA in the human cardiovascular system, and the functional role of ELA in vivo have not been determined.
Hypothesis: We hypothesised ELA is a ligand for the apelin receptor, endogenously expressed in adult human heart and vessels, and attenuates AngII induced pressor responses.
Methods: Peptides were tested in [125I]apelin-13 competition assays. RT-qPCR and immunocytochemistry with selective antisera were performed in adult human normal cardiovascular tissues (IRB approval). The attenuation of AngII (1μg/kg iv)-induced rise in blood pressure by ELA-32 (176μg/kg iv) or apelin-13 (100μg/kg iv) was compared in anesthetised male C57BL/6 mice.
Results: ELA-32 and ELA-21 competed with IC50 values comparable to apelin-13 (~of 2nM), whereas ELA-11 was 60nM (n=4). ELA mRNA and immunoreactivity were detected in human heart and vessels (n=3-9) with ELA immunoreactivity localised to endothelium. ELA (8.4±0.6mmHg) and apelin (6.1±0.8mmHg) (n=4 each) attenuated the rise in systolic blood pressure caused by AngII, significantly more than the reduction between consecutive AngII doses (2.3±0.4mmHg, 3 repeats) (Fig. 1).
Conclusions: This is the first report of ELA expression in human cardiovascular tissues, high affinity binding to the apelin receptor and action on blood pressure regulation in vivo. These findings demonstrate that novel peptide mediators from previously designated non-coding regions may contribute to human cardiovascular physiology.
Peiran Yang, Janet J Maguire, Rhoda E Kuc et al., Circulation, Nov 2014; 130: A15352
Over the past decade, high-throughput studies have identified many novel transcripts. While their existence is undisputed, their coding potential and functionality have remained controversial. Recent computational approaches guided by ribosome profiling have indicated that translation is far more pervasive than anticipated and takes place on many transcripts previously assumed to be non-coding. Some of these newly discovered translated transcripts encode short, functional proteins that had been missed in prior screens. Other transcripts are translated, but it might be the process of translation rather than the resulting peptides that serves a function. Here, we review annotation studies in zebrafish to discuss the challenges of placing RNAs onto the continuum that ranges from functional protein-encoding mRNAs to potentially non-functional peptide-producing RNAs to non-coding RNAs. As highlighted by the discovery of the novel signaling peptide Apela/ELABELA/Toddler, accurate annotations can give rise to exciting opportunities to identify the functions of previously uncharacterized transcripts.
Pauli A, Valen E, Schier AF. Bioessays. 2014 Oct 24. doi: 10.1002/bies.201400103. [Epub ahead of print]
The identification of molecules controlling embryonic patterning and their functional analysis has revolutionized the fields of Developmental and Cell Biology. The use of new sequence information and modern bioinformatics tools has enriched the list of proteins that could potentially play a role in regulating cell behavior and function during early development. The recent application of efficient methods for gene knockout in zebrafish has accelerated the functional analysis of many proteins, some of which have been overlooked due to their small size. Two recent publications report on the identification of one such protein and its role in zebrafish embryogenesis. The protein, currently designated Apela, was shown to act as a secreted protein whose absence adversely affected various early developmental processes. Additional signaling proteins that have been identified in one of the studies are likely to open the way to unraveling hitherto unknown developmental pathways and have the potential to provide a more comprehensive understanding of known developmental processes.
Reichman-Fried M, Raz E. Bioessays. 2014 Aug;36(8):741-5. doi: 10.1002/bies.201400048. Epub 2014 Jun 13.
The secreted signals and signaling pathways that specify cell fate and pattern the body axes of early vertebrate embryos are generally well characterized, but the signals that trigger gastrulation, a major morphogenetic movement that internalizes the endoderm and mesoderm, remain largely uncharacterized. Pauli et al. identified Toddler (Tdl) as a secreted short peptide that is required for gastrulation in zebrafish embryos. The tdl transcript was present throughout the embryo during late blastula and early gastrula stages and was required only during these stages for proper gastrulation. Loss-of-function mutants had various endodermal and mesodermal defects, and the endodermal cells in these mutants migrated more slowly and shorter distances than endodermal cells in gastrulating wild-type embryos. Injection of 2 pg of tdl mRNA rescued the loss-of-function phenotype, but injection of 10 pg or more partially phenocopied loss-of-function mutations, indicating that the precise amount of Tdl activity was important for proper gastrulation. The Apelin receptor (APJ), a G protein–coupled receptor (GPCR) that is activated by the peptide Apelin, was present in mesendodermal cells, and its abundance peaked during gastrulation. Embryos lacking Apelin receptors phenocopied tdl mutants, and injection of Apelin mRNA, which is not normally present during gastrulation, rescued the tdl mutant phenotype. GPCRs are typically internalized upon activation, and expressing tdl in clones of cells in pregastrula embryos caused internalization of a fluorescently tagged version of the Apelin receptor in neighboring cells. This study identifies Tdl as an endogenous ligand for the Apelin receptor, activation of which is required for proper cell movements during zebrafish gastrulation. Human and mouse homologs of tdl were also identified, suggesting that this peptide may also function as a ligand for Apelin receptors in other species. Tdl (also called Elabela) was recently independently reported by Chng et al. to act as a ligand for the Apelin receptor during heart development in zebrafish.
Annalisa M. VanHook, Science Signaling, February 18 2014 Vol. 7, Issue 313, p. ec46
It has been assumed that most if not all signals regulating early development have been identified. Contrary to this expectation, we identified 28 candidate signaling proteins expressed during zebrafish embryogenesis, including Toddler, a short, conserved, and secreted peptide. Both absence and over-production of Toddler reduce the movement of mesendodermal cells during zebrafish gastrulation. Local and ubiquitous production of Toddler promote cell movement, suggesting that Toddler is neither an attractant nor a repellent but acts globally as a motogen. Toddler drives internalization of G-protein-coupled APJ/Apelin receptors, and activation of APJ/Apelin signaling rescues toddler mutants. These results indicate that Toddler is an activator of APJ/Apelin receptor signaling, promotes gastrulation movements, and might be the first in a series of uncharacterized developmental signals.
Evidence indicates that ELA is expressed in human embryonic stem cells and adult human prostate and kidney. ELA may have cardioprotective and/or vasodilatory properties in humans and may play a role in cancer.
Pauli A, Megan L. Norris et al., Science DOI: 10.1126/science.1248636. Published Online January 9 2014
Sequences of apelin and Elabela/Toddler peptides, apelin-36, [Pyr1]apelin-13, Elabela/Toddler-32; Elabela/Toddler-21, Elabela/Toddler-11. Three-letter codes of amino acid residues are shown. pGlu, pyroglutamate; yellow lines represent disulfide bridges. Modified Figure from : Yang P el al. Trends Pharmacol Sci. 2015 Jul 1. pii: S0165-6147(15)00117-0. doi: 10.1016/j.tips.2015.06.002
ELA encodes a conserved vertebrate protein of 54 aa consisting of a secretory signal and a mature 32 aa peptide. The carboxy terminus is invariant. White arrowhead: predicted signal peptide cleavage site between G22 and Q33. Black double arrowheads: possible furin cleavage sites after conserved di-arginines R31R32 and R42R43 motifs. The N- and C-terminal epitopes chosen for α N and α C antibody production are noted.
Chng SC., et. al., Developmental Cell, 27, 1-9; 2013
Tips: See More Research Abstracts and Sequences by clicking the tabs on the top.
|
|
|
%ELA-32%;%ELA-21%;%Prepro-ELA%
|
|
|
