Regulation of the orphan G-protein–coupled receptor GPRC5B by MLC1 and the cell adhesion molecule GlialCAM in megalencephalic leukoencephalopathy

Sep 30, 2026

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Megalencephalic leukoencephalopathy with subcortical cyst (MLC) is a rare leukodystrophy driven by pathogenic variants in MLC1 and GlialCAM. The study identifies the orphan GPCR GPRC5B as an interactor of both proteins and demonstrates constitutive GPCR activity inhibited by MLC1, likely via effects on GPRC5B oligomerization. GlialCAM enhances β-arrestin 2 recruitment but causes its mislocalization from cell–cell junctions, while MLC-linked GPRC5B mutants show increased plasma membrane stability and higher GlialCAM affinity. The data support a tuned signaling model and provide biochemical evidence that GlialCAM and MLC1 modulate GPRC5B activity, explaining gain-of-function phenotypes and suggesting GPRC5B as a therapeutic target.

LanguageEnglish

CategoryHealthcare

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Reading Time40 min

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Megalencephalic leukoencephalopathy and molecular basis

Roles of MLC1 and GlialCAM in astrocyte homeostasis

GPRC5B signaling in leukodystrophy mutants

RESEARCH ARTICLE Regulation of the orphan G-protein–coupled receptor GPRC5B by MLC1 and the cell adhesion molecule GlialCAM in megalencephalic leukoencephalopathy Received for publication, July 2, 2025, and in revised form, November 18, 2025 Published, Papers in Press, November 27, 2025 [https://doi.org/10.1016/j.jbc.2025.1](https://doi.org/10.1016/j.jbc.2025.1)10987 Guillem Pont-Espinós 1,‡, Adrià Pla-Casillanis 1,‡, Laura Ferigle 1,‡, Marta Alonso-Gardón 1, Marc González-Subías 1, Xabier Elorza-Vidal 1, Héctor Gaitán-Peñas 1, Ekaitz Errasti-Murugarren2,3, Andy Chevigne4, Tania López-Hernández 1, Francisco Ciruela5, and Raúl Estévez 1,3,* From the 1Physiology Unit, Department of Physiological Sciences, School of Medicine and Health Sciences, Institute of Neurosciences, University of Barcelona, Neuroscience Program, Physiology and Pathology of the Functional Relationship Between Glia and Neurons-IDIBELL, L’Hospitalet de Llobregat, Spain; 2Genetic Unit, Department of Physiological Sciences, School of Medicine and Health Sciences, Institute of Neurosciences, University of Barcelona, Neuroscience Program, Physiology and Pathology of the Functional Relationship Between Glia and Neurons-IDIBELL, L’Hospitalet de Llobregat, Spain; 3Centro de Investigación en Red de Enfermedades Raras (CIBERER), Instituto de Salud Carlos III, Madrid, Spain; 4Department of Infection and Immunity, Immuno-Pharmacology and Interactomics, Luxembourg Institute of Health (LIH), Esch-sur-Alzette, Luxembourg; and 5Pharmacology Unit, Department of Pathology and Experimental Therapeutics, School of Medicine and Health Sciences, Institute of Neurosciences, University of Barcelona, Neuropharmacology & Pain Group, Neuroscience Program, Bellvitge Institute for Biomedical Research, L’Hospitalet de Llobregat, Spain Reviewed by members of the JBC Editorial Board. Edited by Kirill Martemyanov Megalencephalic leukoencephalopathy with subcortical cyst (MLC) is a rare leukodystrophy primarily caused by mutations in two genes: MLC1, encoding a membrane protein of unknown function, and GlialCAM, a cell adhesion molecule. Although MLC1 has been implicated in downregulating signaling pathways, its molecular mechanisms remain elusive. Recently, the orphan G-protein–coupled receptor GPRC5B was identified as a novel interactor of both GlialCAM and MLC1, with dominant heterozygous mutations found in MLC patients, suggesting that GlialCAM and MLC1 may regulate cell signaling via GPRC5B. Here, we show that GPRC5B exhibits constitutive activity, which is inhibited by MLC1, likely through interference with GPRC5B oligomerization. Conversely, GlialCAM enhances β-arrestin 2 recruitment, leading to its own mislocalization from cell–cell junctions. MLC-associated GPRC5B mutants show enhanced maturation and increased stability at the plasma membrane, retain normal constitutive activity and responsiveness to MLC1 and GlialCAM but display increased affinity for GlialCAM and localize to cell–cell junctions in its presence. Notably, coexpression of GlialCAM with these mutants does not induce GlialCAM mislocalization. We propose a model in which finely tuned interactions among GPRC5B, GlialCAM, and MLC1 regulate receptor signaling. These findings provide the first biochemical evidence of GlialCAM and MLC1 modulating GPRC5B activity, suggesting a biochemical explanation for the gain-offunction phenotype observed in GPRC5B MLC mutants. ‡ These authors contributed equally to this work. * For correspondence: Raúl Estévez, [restevez@ub.edu](restevez@ub.edu). Importantly, our work supports the potential of targeting GPRC5B as a therapeutic strategy in MLC. Megalencephalic leukoencephalopathy with subcortical cyst (MLC) is a rare leukodystrophy primarily characterized by vacuolization of myelin and astrocytes (1). Clinically, MLC manifests with early onset macrocephaly, progressive motor impairment, including ataxia and spasticity, epileptic seizures, and cognitive decline (2).

FAQs

What is the role of GPRC5B in MLC according to the study?

The study reports that the orphan GPCR GPRC5B interacts with both GlialCAM and MLC1 and is involved in receptor signaling relevant to MLC pathology.

How does MLC1 affect GPRC5B activity?

GPRC5B shows constitutive activity that is inhibited by MLC1, likely through interference with GPRC5B oligomerization.

How does GlialCAM influence β-arrestin 2 recruitment and localization?

GlialCAM enhances β-arrestin 2 recruitment, leading to its mislocalization away from cell–cell junctions.

Sep 30, 2026

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