The metabotropic Glutamate receptor-1 is a glutamatergic checkpoint that integrates with TCR to augment anti-tumor CD8⁺ T cell activation, metabolism and effector function
Presenter: Salvador Gonzalez Ochoa, PhD Session: Adaptive Immunity in Cancer Time: 4/21/2026 9:00:00 AM → 4/21/2026 12:00:00 PM
Authors
Salvador Gonzalez Ochoa 1 , Maria Teresa P. de Aquino 1 , Thomas W. Hodo 1 , Thanigaivelan Kanagasabai 1 , Muna A. Mohammed 2 , Jane Tonello 1 , Alla Ivanova 1 , Anil Shanker 3 1 Department of Biochemistry, Cancer Biology, Neuroscience and Pharmacology, Meharry Medical College, Nashville, TN, 2 Department of Biomedical Sciences, Meharry Medical College School of Graduate Studies, Meharry Medical College, Nashville, TN, 3 The Office for Research and Innovation, Meharry Medical College, Nashville, TN
Abstract
Background: Glutamate receptors (GluRs), classically linked to neuronal signaling, are also recognized as key immunomodulators. T cell activation requires precise coordination of TCR-driven signaling microclusters and calcium-dependent pathways that shape T cell effector function. Emerging evidence shows that glutamatergic cues influence T cell metabolism, activation, and fate, yet their role within TCR signaling remains poorly defined. Here, we show how GluR-TCR interactions govern CD8⁺ T cell activation and function, particularly within the metabolic and functional constraints of the tumor microenvironment. Methods: Tumors and lymphoid tissue single-cell suspensions were analyzed for the expression of ionotropic (GluA3, NR1, NR2B) and metabotropic (mGluR1, mGluR5) receptors on CD4⁺ and CD8⁺ TILs by flow cytometry. CD8⁺ T cells were activated with anti-CD3/CD28 or PMA/ionomycin ± IL-2 in the presence or absence of NBQX (GluA3) and CPCCOEt (mGluR1) inhibitors. Expression of glutamate transporters, viability, and extracellular glutamate were assessed by fluorometric assays. CPCCOEt-treated cells were analyzed for mGluR1-TCR colocalization and phosphorylation of TCR-signaling proteins by confocal microscopy and flow cytometry. Metabolic activity was measured by Seahorse XF96 (OCR/ECAR). Intracellular Ca²⁺ dynamics were evaluated using Fura-2 AM ratiometric imaging. CD8⁺ T cell proliferation was assessed by CFSE, and cytotoxicity was tested in vitro and in vivo using a pulmonary metastasis model; activated CD8⁺ T cells ± antagonists were transferred retro-orbitally. Results: We found that mGluR1 and GluA3 are expressed at higher levels in T cells compared with other immune cell lineages, and their expression increases during CD8⁺ T cell activation. Conversely, pharmacologic inhibition with CPCCOEt significantly impaired CD8⁺ T cell activation, disrupting mGluR1 colocalization with the TCR-Vβ8.1 in the cell membrane and reducing phosphorylation of key proteins involved in TCR-driven signaling, metabolic pathways, inducing a pronounced dysregulation of Ca²⁺ flux. Functionally, CPCCOEt-treated CD8⁺ T cells showed a reduction in proliferation to levels resembling naïve T cells and a marked decrease in cytotoxic activity. In vivo, these impairments translated into an increased burden of secondary metastatic pulmonary nodules, highlighting the essential role of mGluR1 signaling in sustaining effector CD8⁺ T cell function and antitumor immunity. Conclusion: These findings identify mGluR1 as a critical glutamatergic checkpoint that integrates with the TCR to augment CD8⁺ T cell activation, metabolism, and effector function. Its disruption collapses signaling strength, Ca²⁺ responses, and cytotoxic competence, revealing a potential target to boost T cell potency in solid tumor microenvironments.
Disclosure
S. Gonzalez Ochoa, None.. M. P. de Aquino, None.. T. W. Hodo, None.. T. Kanagasabai, None.. M. A. Mohammed, None.. J. Tonello, None.. A. Ivanova, None.. A. Shanker, None.
Cited in
Control: 6742 · Presentation Id: 1313 · Meeting 21436