Related Experiment Video
Updated: Aug 8, 2026
A Microfluidic Chip for the Versatile Chemical Analysis of Single Cells
Published on: October 16, 2013
Analysis of mGluR1a constitutive internalization using a pulse-chase enzyme-linked immuno-sorbant assay (ELISA)
Giordano Pula1, Stuart J Mundell, Peter J Roberts
1Department of Pharmacology, School of Medical Sciences, University of Bristol, Bristol BS8 1TD, United Kingdom. g.pula@bristol.ac.uk
Insights
A new pulse-chase ELISA method effectively measures constitutive internalization of metabotropic glutamate receptor 1a (mGluR1a). This method reveals arrestin- and clathrin-dependent mGluR1a internalization, offering insights into receptor regulation.
Area of Science:
- Neuroscience
- Cell Biology
- Biochemistry
Background:
- G protein-coupled receptor (GPCR) surface expression is modulated by internalization.
- Constitutive internalization, occurring without agonist stimulation, is a known regulatory mechanism for many GPCRs.
- The constitutive internalization of metabotropic glutamate receptor 1a (mGluR1a) is recognized but underexplored.
Purpose of the Study:
- To develop and validate a novel pulse-chase ELISA method for investigating mGluR1a constitutive internalization.
- To elucidate the molecular mechanisms underlying mGluR1a constitutive internalization.
- To assess constitutive internalization in mGluR1b splice variants and mGluR1a mutants.
Main Methods:
- Development of a pulse-chase ELISA assay to quantify mGluR1a internalization.
- Utilizing dominant-negative arrestin-2 and Eps-15 constructs to probe internalization pathways.
- Employing confocal microscopy for validating receptor localization.
- Testing mGluR1b and mGluR1a COOH-terminal deletion mutants (DMI, DMII) in the assay.
Main Results:
- The pulse-chase ELISA demonstrated that mGluR1a constitutive internalization is dependent on arrestin-2 and clathrin.
- Confocal microscopy confirmed the validity of the pulse-chase labelling procedure.
- mGluR1b exhibited minimal constitutive internalization, while the mGluR1a mutant DMII showed significant internalization, implicating the Arg847-Arg868 region in trafficking regulation.
Conclusions:
- The pulse-chase ELISA is an efficient and reliable tool for analyzing GPCR constitutive internalization.
- mGluR1a constitutive internalization is an arrestin- and clathrin-dependent process.
- Specific regions of the mGluR1a C-terminus play a critical role in regulating its constitutive trafficking.
Abstract:
The surface expression of G protein-coupled receptors is regulated by internalization. For many receptors, a constitutive level of internalization in the absence of agonist has been reported. The constitutive internalization of metabotropic glutamate receptor 1a (mGluR1a) has been described, but in general little attention has been dedicated to this important aspect of receptor regulation. Here we describe a pulse-chase ELISA method that allows the investigation of mGluR1a constitutive internalization. When investigated by pulse-chase ELISA, the constitutive internalization of mGluR1a was inhibited by dominant negative mutant constructs of arrestin-2 or Eps-15. This observation, besides indicating the arrestin- and clathrin-dependence of mGluR1a constitutive internalization, also confirmed the physiological relevance of the method described in this article. Confocal microscopy experiments to study receptor localization further validated the pulse-chase labelling procedure. The application of the pulse-chase ELISA to mGluR1b, revealed that this splice variant undergoes marginal constitutive internalization. Two COOH-terminal deletion mutants of mGluR1a, DMI (Arg847stop) and DMII (Arg868stop), were also tested for constitutive internalization. Interestingly, only DMII underwent significant constitutive internalization, suggesting that the region between Arg847 and Arg868 might play a regulatory role in mGluR1a trafficking. Taken together, the pulse-chase ELISA appears to be an efficient tool to analyze the constitutive internalization of different mGluR1 splice variants.
