Targeting GLP-1 receptor trafficking to improve agonist efficacy

Glucagon-like peptide-1 receptor (GLP-1R) activation promotes insulin secretion from pancreatic beta cells, causes weight loss, and is an important pharmacological target in type 2 diabetes (T2D). Like other G protein-coupled receptors, the GLP-1R undergoes agonist-mediated endocytosis, but the functional and therapeutic consequences of modulating GLP-1R endocytic trafficking have not been clearly defined. Here, we investigate a series of biased GLP-1R agonists with variable propensities for GLP-1R internalization and recycling. Compared to a panel of FDA-approved GLP-1 mimetics, compounds that retain GLP-1R at the plasma membrane produce greater long-term insulin release, which is dependent on a reduction in β-arrestin recruitment and faster agonist dissociation rates. Such molecules elicit glycemic benefits in mice without concomitant increases in signs of nausea, a common side effect of GLP-1 therapies. Our study identifies a set of agents with specific GLP-1R trafficking profiles and the potential for greater efficacy and tolerability as T2D treatments

Conditional and Reversible Activation of Class A and B G Protein-Coupled Receptors Using Tethered Pharmacology

Understanding the activation and internalization of G protein-coupled receptors (GPCRs) using conditional approaches is paramount to developing new therapeutic strategies. Here, we describe the design, synthesis, and testing of ExONatide, a benzylguanine-linked peptide agonist of the glucagon-like peptide-1 receptor (GLP-1R), a class B GPCR required for maintenance of glucose levels in humans. ExONatide covalently binds to SNAP-tagged GLP-1R-expressing cells, leading to prolonged cAMP generation, Ca2+ rises, and intracellular retention of the receptor. These effects were readily switched OFF following cleavage of the introduced disulfide bridge using the cell-permeable reducing agent beta-mercaptoethanol (BME). A similar approach could be extended to a class A GPCR using GhrelON, a benzylguanine-linked peptide agonist of the growth hormone secretagogue receptor 1a (GHS-R1a), which is involved in food intake and growth. Thus, ExONatide and GhrelON allow SNAP-tag-directed activation of class A and B GPCRs involved in gut hormone signaling in a reversible manner. This tactic, termed reductively cleavable agONist (RECON), may be useful for understanding GLP-1R and GHS-R1a function both in vitro and in vivo, with applicability across GPCRs

Agonist-induced membrane nanodomain clustering drives GLP-1 receptor responses in pancreatic beta cells

The glucagon-like peptide-1 receptor (GLP-1R), a key pharmacological target in type 2 diabetes (T2D) and obesity, undergoes rapid endocytosis after stimulation by endogenous and therapeutic agonists. We have previously highlighted the relevance of this process in fine-tuning GLP-1R responses in pancreatic beta cells to control insulin secretion. In the present study, we demonstrate an important role for the translocation of active GLP-1Rs into liquid-ordered plasma membrane nanodomains, which act as hotspots for optimal coordination of intracellular signaling and clathrin-mediated endocytosis. This process is dynamically regulated by agonist binding through palmitoylation of the GLP-1R at its carboxyl-terminal tail. Biased GLP-1R agonists and small molecule allosteric modulation both influence GLP-1R palmitoylation, clustering, nanodomain signaling, and internalization. Downstream effects on insulin secretion from pancreatic beta cells indicate that these processes are relevant to GLP-1R physiological actions and might be therapeutically targetable

Agonist-induced membrane nanodomain clustering drives GLP-1 receptor responses in pancreatic beta cells

The glucagon-like peptide-1 receptor (GLP-1R), a key pharmacological target in type 2 diabetes (T2D) and obesity, undergoes rapid endocytosis after stimulation by endogenous and therapeutic agonists. We have previously highlighted the relevance of this process in fine-tuning GLP-1R responses in pancreatic beta cells to control insulin secretion. In the present study, we demonstrate an important role for the translocation of active GLP-1Rs into liquid-ordered plasma membrane nanodomains, which act as hotspots for optimal coordination of intracellular signaling and clathrin-mediated endocytosis. This process is dynamically regulated by agonist binding through palmitoylation of the GLP-1R at its carboxyl-terminal tail. Biased GLP-1R agonists and small molecule allosteric modulation both influence GLP-1R palmitoylation, clustering, nanodomain signaling, and internalization. Downstream effects on insulin secretion from pancreatic beta cells indicate that these processes are relevant to GLP-1R physiological actions and might be therapeutically targetable

Regulation of GLP-1R signalling by endocytic membrane trafficking and its significance for pancreatic beta-cell insulin secretion

The G protein-coupled glucagon-like peptide-1 receptor (GLP-1R) regulates glucose homeostasis by potentiating pancreatic insulin secretion, representing a key target for type 2 diabetes (T2D) treatment. Upon agonist-induced GLP-1R plasma membrane signalling, the GLP-1R enters the endocytic pathway where it is sorted to recycling and/or degradative compartments in a regulated manner. Since the endocytic pathway tightly regulates GPCR activity, understanding the mechanisms that control agonist-mediated GLP-1R trafficking might lead to identification of new T2D therapeutic targets and/or development of improved GLP-1R agonists. Herein, we have screened an siRNA library of GPCR trafficking regulators with the aim of identifying factors capable of controlling GLP-1R activity and pancreatic -cell responses. Based on their effect on exendin-4-induced insulin secretion, we have identified five factors [clathrin, dynamin1, AP2, and sorting nexins (SNXs) SNX27 and SNX1] that negatively regulate, and four [huntingtin-interacting protein 1 (HIP1), HIP14, G protein-coupled receptor associated sorting protein-1 (GASP-1), and Neural Precursor Cell Expressed, Developmentally Down-Regulated 4 (Nedd4)], that enhance GLP-1R activity. Amongst these, we selected three candidates (HIP1, SNX1 and SNX27) for further characterisation. HIP1 was found to modulate GLP-1R G protein coupling while concomitantly controlling GLP-1R internalisation, while the two SNXs were shown to control GLP-1R endosomal sorting, affecting GLP-1R recycling versus degradation rates and determining endosomal and cell surface responses. In parallel, we investigated the role of the plasma membrane lipid composition on GLP-1R signalling and trafficking. Upon ligand binding, GLP-1R was shown to undergo palmitoylation and partitioning into specific cholesterol-enriched plasma membrane nanodomains, leading to GLP-1R signal transduction and cholesterol-dependent internalisation. This process was controlled by specific agonist binding kinetics and positive allosteric modulation. We have therefore identified key endocytic factors that determine GLP-1R activity and -cell incretin responses. Furthermore, we have demonstrated that both GLP-1R activity and trafficking are modulated by interactions with the surrounding lipid bilayer.Open Acces

Convenio de Alianza Integral entre AIESEC en Ecuador y Universidad de Cuenca

Españo

El trabajo infantil, del capitalismo pesado al capatilismo liviano

This article aims at recognizing childhood labor as a current issue in the history of work, specifically within the history of the working class of the industrial capitalism to that of today’s post-industrial capitalism, highlighting how such an issue has become worse by the childhood condition (and within it, the condition of genre) and by the perceptions people have had on this issue throughout history.  The author makes an effort at looking some moments of the working class in order to show the changes and the persistences of childhood labor, but it does not aim at being a historical reconstruction of the issueEl presente artículo pretende entonces, reconocer al trabajo infantil como una problemática  presente en la historia del trabajo, específicamente dentro de la historia de la clase obrera del capitalismo industrial hasta la del capitalismo posindustrial de hoy, resaltando como dicha problemática ha sido agravada por la condición de niñez (y dentro de esta la condición de género) y por las percepciones que de esta se ha tenido a lo largo de la historia. Se hace un esfuerzo en mirar algunos momentos de la historia de la clase obrera para ilustrar los cambios y las persistencias del fenómeno del trabajo infantil, más no pretende ser una reconstrucción histórica del mism

On Catalan numbers

This paper provides problems on generating Catalan numbers and some of its applications for readers to be familiar with the sequence. The articles entitled Catalan Strikes Again! How Likely Is A Function To Be Convex? written by Roger B. Eggleton and Richard K. Guy and Mathematical Games by Martin Gardner were the bases for this paper. The concepts used are basically related to such fields as Combinatorics, Probabilities and College Algebra. The problem Is the probability of the function (0, fo), (1, f1),... (n, fn) with n+1 points and within the interval [0,1] convex? was considered to generate the formula cn/(n!)2

Síndrome del túnel del tarso: normalización de una técnica diagnóstica electrofisiológica

EI síndrome del túnel del tarso es una entidad frecuente en la población adulta, pero infrecuentemente documentada. En su diagnóstico los estudios de neuroconducción han demostrado ser importantes para confirmar su presencia y evaluar su severidad. La presente investigación, hace un análisis prospectivo de los hallazgos de neuroconducción motora de los nervios plantares interno y externo, encontrados en 32 individuos asintomáticos. Se verifica con el objeto de estandarizar valores de referencia para nuestro medio, aplicando la técnica de Felsenthal, para discriminar entre una lesión a nivel del túnel del tarso, lesiones aisladas de los nervios plantares o neuropatías distales por otra causa. Los resultados obtenidos mostraron una latencia motora promedio a través del túnel para el nervio plantar interno de 2.35 ms (rango O.64ms - 4.09ms) y para el nervio plantar externo de 2.32ms (rango O.29ms - 3.77ms), también se establecieron velocidades de conducción proximal del nervio tibial para descartar anormalidades en su trayecto a través de la pierna, que pudieran invalidar los datos obtenidos distalmente