mGluR3

The metabotropic glutamate receptor 3 (mGluR3) is a Group II G-protein-coupled receptor that regulates glutamate neurotransmission and synaptic plasticity^[1][2]. Mechanistically, mGluR3 is expressed on both glial cells and neurons, with a predominantly presynaptic localization, acting as an inhibitory autoreceptor and heteroceptor^[1][2][3]. In contrast to its close isoform mGluR2, mGluR3 contributes specifically to long-term depression and glial-mediated neuroprotection^[1][3]. Activation of mGluR3 modulates downstream signaling pathways involved in neurotrophic factor production, including TGF-β, GDNF, NGF, and BDNF, which are critical for neuronal survival in experimental neurodegenerative models. Genetic studies link GRM3 polymorphisms to schizophrenia-related endophenotypes, such as impaired cognition and altered cortical activation, highlighting disease relevance^[1][2]. Pharmacologically, selective mGluR3 agonists and positive allosteric modulators promote neuroprotection and modulate presynaptic glutamate release, whereas non-selective Group II ligands affect both mGluR2 and mGluR3^[3]. Compared with mGluR2, mGluR3 exhibits distinct presynaptic inhibitory functions and glial involvement, offering unique experimental and therapeutic opportunities^[3][4]. Recent studies also explore mGluR3 antagonists in glioblastoma models, where blockade induces astroglial differentiation and enhances cytotoxic chemotherapy efficacy^[5]. Collectively, these findings establish mGluR3 as a critical modulator of glutamatergic signaling, neuroprotection, and disease-specific pathways, distinct from other Group II metabotropic glutamate receptors^[1][2][3][5].