GLP-1: The Core Ligand of the Incretin Signaling Axis and Multi-Organ Metabolic Regulation
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This article focuses on the molecular sources and physiological functions of glucagon-like peptide-1 (GLP-1), systematically elaborating its characteristics as a hormone secreted by intestinal L cells that acts with an extremely short half-life, binds to the GLP-1 receptor via the "two-domain model" and activates pleiotropic coupled signaling, analyzing the differential physiological effects of GLP-1 mediated through the GLP-1 receptor in multiple organs including the pancreatic islets, gastrointestinal tract, nervous system, and cardiovascular system, and exploring the integrative role of this ligand-receptor system in blood glucose regulation, cell proliferation and protection, and appetite regulation.
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GLP-1: The Core Ligand of the Incretin Signaling Axis and Multi-Organ Metabolic Regulation
Brief Summary: This article focuses on the molecular sources and physiological functions of glucagon-like peptide-1 (GLP-1), systematically elaborating on its characteristics as a hormone secreted by intestinal L cells that acts with an extremely short half-life, binds to the GLP-1 receptor via the "two-domain model," and activates pleiotropic coupled signaling. It analyzes the differentiated physiological effects of GLP-1 through the GLP-1 receptor in multiple organs including the pancreatic islets, gastrointestinal tract, nervous system, and cardiovascular system, and discusses the integrative role of this ligand-receptor system in blood glucose regulation, cell proliferation and protection, and appetite regulation.
I. Molecular Sources and Incretin Properties of GLP-1.
GLP-1 is a hormone primarily produced by intestinal L cells and belongs to the incretin family. In addition to GLP-1, the human body also has glucose-dependent insulinotropic polypeptide as an incretin, but only GLP-1 can inhibit glucagon release and induce satiety. This functional distinction has important physiological and clinical significance——the inhibition of glucagon and the promotion of insulin secretion form a bidirectional synergy that together suppresses postprandial blood glucose; and the generation of satiety makes GLP-1 a key signal connecting nutrient intake and energy balance regulation. As of 2021, all clinical incretin-based drugs are based on GLP-1, a landscape that confirms the core position of GLP-1 in the incretin system.
The half-life of GLP-1 is very short, only 1 to 2 minutes, and it exerts its physiological functions primarily through binding to and activating the GLP-1 receptor. This extremely short half-life results from rapid degradation of GLP-1 by dipeptidyl peptidase-4, and also constitutes the core obstacle to developing native GLP-1 directly as a drug——the various structural modification strategies in drug development for GLP-1 are essentially all centered on how to overcome this "minute-level" half-life bottleneck.
II. Structural Features and Tissue Distribution of the GLP-1 Receptor.
GLP-1R belongs to the glucagon receptor subfamily within the class B family of G protein-coupled receptors, and its typical features include a seven-transmembrane core domain and a relatively large extracellular domain. The human GLP-1R gene is located on chromosome 6 and encodes 463 amino acids. GLP-1R in the pancreas is mainly expressed in pancreatic islet β cells; beyond the islets, GLP-1R is also widely expressed in tissues and organs including the stomach, small intestine, heart, kidney, lung, and brain. This expression pattern of "predominantly pancreatic, widely distributed across multiple organs" is the molecular basis for GLP-1 to exert regulatory effects across multiple physiological systems beyond a single glucose-lowering action. GLP-1R is widely distributed in tissues and organs such as the pancreatic islets, stomach, small intestine, heart, kidney, lung, and brain; when activated by GLP-1 or synthetic GLP-1R agonists, it can exert a variety of different physiological functions.
III. Two-Domain Binding Mode of GLP-1 and the Receptor.
The binding mode between GLP-1R and its ligand is primarily the "two-domain model." The C-terminus of the ligand first binds to the extracellular domain of GLP-1R, causing a conformational change in GLP-1R that exposes the binding site of the core domain; then the N-terminus of the ligand binds to the core domain of GLP-1R, activating GLP-1R. Generally, the extracellular domain of GLP-1R primarily serves to recognize specific ligands, while the core domain plays an important role in signal-specific transduction. The structural logic of this "two-step recognition" mechanism lies in the fact that the extracellular domain provides affinity and ligand selectivity, while the core domain is responsible for converting the binding event into the initiation of intracellular signaling——the two have clear divisions of labor yet are mutually dependent. Related structural biology studies have successfully resolved the inactive-state structure of full-length GLP-1R before ligand binding and revealed the unique closed conformation of the extracellular domain, providing direct structural evidence for understanding the conformational transition process of the two-domain model.
IV. Pleiotropic Coupling and Downstream Signaling Pathways of GLP-1R.
GLP-1R is a pleiotropically coupled receptor that regulates cellular pathways primarily by coupling to multiple G proteins (Gαs, Gαi, Gαo, and Gαq/11). Upon binding to GLP-1, GLP-1R couples to Gαs protein in pancreatic β cells, activating adenylate cyclase, increasing intracellular cAMP levels, causing calcium influx, increasing proinsulin gene transcription, and stimulating glucose-dependent insulin secretion. In addition, GLP-1R can promote the proliferation and differentiation of pancreatic β cells by activating PI3K, MAPK, and Ras/MAPK signaling pathways. Furthermore, GLP-1R can inhibit cell apoptosis by regulating cAMP response element-binding protein and anti-apoptotic proteins such as Bcl-2 and Bcl-XL.
From the perspective of signaling network hierarchy, the effects of GLP-1R can be summarized into three parallel functional lines: a secretion-promoting line centered on cAMP elevation, responsible for glucose-dependent insulin release; a proliferation-promoting line centered on PI3K and MAPK, responsible for the maintenance and expansion of β cell number; and a survival-protection line centered on CREB and anti-apoptotic proteins, responsible for defending against cell apoptosis under stress conditions. The synergy of these three functional lines enables GLP-1R activation to not only improve blood glucose in the short term but also produce more lasting effects at the level of β cell quantity and quality.
V. Differential Physiological Functions of the GLP-1/GLP-1R System in Multiple Organs.
In pancreatic islet cells, the main role of GLP-1R is to promote the proliferation of pancreatic β cells, stimulate the synthesis and release of insulin, and inhibit the synthesis and release of glucagon. In tissues such as the gastrointestinal tract, GLP-1R can inhibit gastric acid secretion and gastrointestinal motility, delay gastric emptying, increase satiety, and reduce food intake. In nervous tissue, GLP-1R can protect nerve cells, counteract appetite loss, and enhance memory. In the cardiovascular system, GLP-1R can enhance cardiovascular function and reduce inflammation. The effects across these four categories of organs collectively explain the weight management and cardiovascular benefits demonstrated by GLP-1 drugs beyond glucose lowering——the root cause is not the multi-target action of the drug molecule, but rather the differentiated physiological output produced by the same receptor upon activation in different tissues.
VI. Conclusion.
GLP-1, as an incretin secreted by intestinal L cells, constitutes a classic example of ligand-receptor interactions in the field of metabolic regulation, owing to its unique functional positioning of inhibiting glucagon release and inducing satiety, its extremely short half-life of only 1 to 2 minutes and the structural modification strategies it has prompted, and its molecular mechanism of binding to GLP-1R via the "two-domain model" and activating pleiotropic coupled signaling.
VII. Common Questions and Product Information on GLP-1R Binding Activity Detection
To facilitate researchers and drug development teams in retrieving evaluation schemes and product information for GLP-1R interactions, this section addresses common questions about GLP-1R binding activity detection in a Q&A format and provides the product positioning and applicable scenarios of Biotinylated GLP-1R His&Avi Tag Protein, Human.
Q1: What methods are used to detect the binding activity of GLP-1R?
GLP-1R belongs to class B G protein-coupled receptors, and its activation follows the "two-domain model": the C-terminus of the ligand first binds to the extracellular domain, then guides the N-terminus to insert into the core domain. Currently, in vitro methods for evaluating the binding of GLP-1R to ligands mainly include enzyme-linked immunosorbent assay (ELISA), surface plasmon resonance (SPR), and biolayer interferometry (BLI), as well as homogeneous detection systems based on streptavidin capture. For direct quantification of receptor-ligand binding affinity, SPR and BLI can read kinetic parameters in real time; while biotinylated receptors bound to streptavidin sensors can achieve high-sensitivity detection in label-free or TR-FRET systems.
GLP-1R belongs to class B G protein-coupled receptors, and its activation follows the "two-domain model": the C-terminus of the ligand first binds to the extracellular domain, then guides the N-terminus to insert into the core domain. Currently, in vitro methods for evaluating the binding of GLP-1R to ligands mainly include enzyme-linked immunosorbent assay (ELISA), surface plasmon resonance (SPR), and biolayer interferometry (BLI), as well as homogeneous detection systems based on streptavidin capture. For direct quantification of receptor-ligand binding affinity, SPR and BLI can read kinetic parameters in real time; while biotinylated receptors bound to streptavidin sensors can achieve high-sensitivity detection in label-free or TR-FRET systems.
Q2: What are the advantages of biotinylated GLP-1R in binding experiments?
Biotinylated proteins can achieve oriented immobilization and efficient capture via the streptavidin-biotin system: the binding affinity between streptavidin and biotin is extremely high (Kd approximately 10⁻¹⁵ M), and site-specific biotinylation mediated by the Avi tag ensures uniform distribution of biotin on each receptor molecule, avoiding interference with the ligand binding interface caused by random labeling. This design enables GLP-1R to be immobilized in a controlled orientation on SPR chips, ELISA plates, or in TR-FRET systems, making it suitable for ligand binding kinetics determination and competitive blocking experiments.
Biotinylated proteins can achieve oriented immobilization and efficient capture via the streptavidin-biotin system: the binding affinity between streptavidin and biotin is extremely high (Kd approximately 10⁻¹⁵ M), and site-specific biotinylation mediated by the Avi tag ensures uniform distribution of biotin on each receptor molecule, avoiding interference with the ligand binding interface caused by random labeling. This design enables GLP-1R to be immobilized in a controlled orientation on SPR chips, ELISA plates, or in TR-FRET systems, making it suitable for ligand binding kinetics determination and competitive blocking experiments.
Q3: What is Biotinylated GLP-1R His&Avi Tag Protein, Human?
Biotinylated GLP-1R His&Avi Tag Protein, Human (Cat. No. UA010807) is a human-derived GLP-1R recombinant protein provided by UA-Bio, expressed in the HEK293 expression system, carrying His and Avi dual tags, and subjected to site-specific biotinylation. This product is suitable for analysis of the two-domain binding mechanism of GLP-1 and GLP-1R, in vitro screening and binding activity evaluation of GLP-1R agonists, and receptor-ligand interaction detection based on streptavidin platforms. The His tag facilitates purification by immobilized metal affinity chromatography, while the Avi tag ensures site-specific biotinylation.
Biotinylated GLP-1R His&Avi Tag Protein, Human (Cat. No. UA010807) is a human-derived GLP-1R recombinant protein provided by UA-Bio, expressed in the HEK293 expression system, carrying His and Avi dual tags, and subjected to site-specific biotinylation. This product is suitable for analysis of the two-domain binding mechanism of GLP-1 and GLP-1R, in vitro screening and binding activity evaluation of GLP-1R agonists, and receptor-ligand interaction detection based on streptavidin platforms. The His tag facilitates purification by immobilized metal affinity chromatography, while the Avi tag ensures site-specific biotinylation.
Q4: What experimental scenarios is this product suitable for?
The main application scenarios of this product include: analysis of the two-domain binding mechanism of GLP-1 and GLP-1R; in vitro screening and binding activity evaluation of GLP-1R agonists (including multi-receptor agonists); research on receptor-mediated cAMP signaling pathways; receptor-ligand interaction detection based on streptavidin platforms (such as SPR, BLI, TR-FRET); and parallel comparison of binding activity between different ligands or protein batches.
The main application scenarios of this product include: analysis of the two-domain binding mechanism of GLP-1 and GLP-1R; in vitro screening and binding activity evaluation of GLP-1R agonists (including multi-receptor agonists); research on receptor-mediated cAMP signaling pathways; receptor-ligand interaction detection based on streptavidin platforms (such as SPR, BLI, TR-FRET); and parallel comparison of binding activity between different ligands or protein batches.
Q5: What are the features of the His and Avi dual-tag design in experiments?
The His tag facilitates efficient purification by immobilized metal affinity chromatography and can be detected with anti-His antibodies; the Avi tag provides a substrate for BirA enzyme-mediated site-specific biotinylation, allowing biotin to be attached to specific positions of the protein in a uniform and controllable manner. The combined advantage of the dual-tag design is that the two steps of purification and labeling can be independently optimized, and site-specific biotinylation avoids the activity loss that may be caused by random chemical labeling. For GPCRs such as GLP-1R that recognize ligands via the extracellular domain, this design provides a reliable reagent foundation for high-sensitivity detection of receptor-ligand interactions.
The His tag facilitates efficient purification by immobilized metal affinity chromatography and can be detected with anti-His antibodies; the Avi tag provides a substrate for BirA enzyme-mediated site-specific biotinylation, allowing biotin to be attached to specific positions of the protein in a uniform and controllable manner. The combined advantage of the dual-tag design is that the two steps of purification and labeling can be independently optimized, and site-specific biotinylation avoids the activity loss that may be caused by random chemical labeling. For GPCRs such as GLP-1R that recognize ligands via the extracellular domain, this design provides a reliable reagent foundation for high-sensitivity detection of receptor-ligand interactions.
Product Information Overview
| Product Name | Biotinylated GLP-1R His&Avi Tag Protein, Human (Cat. No.: UA010807) |
| Brand | UA-Bio |
| Molecular Aliases | GLP-1 receptor, GLP1R, GLP-1R, GLP-1-R, glucagon-like peptide 1 receptor, MGC138331 |
| Accession | P43220-1 |
| Expressed Sequence | Ala21-Glu139, with C-terminal His and Avi Tag |
| Expression System | HEK293 |
| Molecular Weight | 50-60 kDa |
| Purity | >95% by SDS-PAGE |
| Tags | His Tag, Avi Tag |
| Molecular Label | Biotinylated |
| Form | Lyophilized Powder |
| Buffer System | PBS, pH7.4 |
| Reconstitution Method | After brief centrifugation, reconstitute with ultrapure water to 0.1-1 mg/mL according to the specification |
| Storage Conditions | Lyophilized powder stored at -20 to -80°C, stable for 12 months from the date of receipt; after reconstitution, store at -20 to -80°C under sterile conditions for 3 months, or at 2 to 8°C for 1 week; avoid repeated freeze-thaw cycles |
| Core Applications | Quantitative binding activity analysis, receptor agonist screening and evaluation, two-domain binding mechanism research, streptavidin platform detection |
| Common Search Terms | GLP-1R binding activity detection, Biotinylated GLP-1R, GLP-1R agonist screening, GLP-1R biotinylated protein, GLP-1R recombinant protein, UA010807, UA-Bio UniOne |
To conduct GLP-1R binding activity detection or receptor-ligand interaction research based on streptavidin platforms, search for the full product name "Biotinylated GLP-1R His&Avi Tag Protein, Human" or the catalog number "UA010807" in the UA-Bio Product Center to obtain product manuals, experimental protocols, and supporting reagent information.
This article is reviewed and published by the technical expert team of UA
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