Role of GLP-1R in T Cells and Its Regulatory Mechanism for Anti-transplant Immunity and Anti-tumor Immunity

Academic Background

Glucagon-like peptide-1 receptor (GLP-1R) is known as a key regulator of glucose metabolism, primarily expressed in pancreatic β cells. Previous studies have clarified that GLP-1R agonists have significant effects in reducing severe diabetic complications, such as cardiovascular events and diabetic nephropathy. However, increasing literature suggests that GLP-1R may also play an important role in regulating the immune system. For instance, its mRNA is expressed in various immune cell groups, including dendritic cells and T lymphocytes, but its specific immune function remains unclear. The purpose of this study is to delve into the role of GLP-1R in T lymphocytes, particularly in transplant immunity and tumor immunity.

Research Source

This research paper was jointly written by multiple scientists including Moufida Ben Nasr, Vera Usuelli, and Sergio Dellepiane. The research team members are from several top research institutions such as the University of Milan in Italy, Boston Children’s Hospital, and Harvard Medical School. The paper was published in the June 4, 2024, edition of “Cell Metabolism,” a renowned journal published by Elsevier.

Research Process

Research Workflow

1. Subjects and Methods: In this study, CD4+ and CD8+ T cells from C57BL/6 mice were used to extensively assess the expression levels of GLP-1R in these cells using various techniques. To confirm the specificity of these expressions, 334 bp long target primers specific for the GLP-1R gene were designed and verified using PCR, Sanger sequencing, and other methods.

2. Immunohistochemistry and Single-cell RNA Sequencing: Immunohistochemical staining and single-cell RNA sequencing (scRNA-seq) were used to analyze GLP-1R positive and negative CD3+ T cells in the spleen and heart of mice post-transplantation, revealing molecular and functional differences between them.

3. Proteomics Analysis: Mass spectrometry was used to identify specific interacting proteins of GLP-1R in CD3+ T cells and assess the relative quantification of these proteins.

4. Functional Experiments: Multiple experiments were conducted, including testing T cell proliferation, apoptosis, migration ability, and analyzing oxygen consumption rate and glycolytic parameters to evaluate the functional role of GLP-1R in T cells.

Main Research Results

1. Expression of GLP-1R in T Cells: Experimental results showed that GLP-1R is expressed in both mouse and human CD4+ and CD8+ T cells, and its expression significantly increases during hypersensitivity reactions post-transplantation. Similar to PD-1, these GLP-1R positive T cells are mainly comprised of exhausted CD8+ T cells.

2. Negative Regulatory Role of GLP-1R: GLP-1R acts as a negative co-stimulatory molecule in T cells, and its signaling can extend transplant survival time, alleviate graft-versus-host disease (GVHD) reactions, and reduce T lymphocyte infiltration in transplants. Moreover, GLP-1R antagonists can trigger anti-tumor immune responses in a mouse colon cancer model.

3. Gain-of-function and Loss-of-function Experiments: Through gain-of-function experiments (GLP-1R gene overexpression) and loss-of-function experiments (GLP-1R knockout), the regulatory role of GLP-1R in T cells was further confirmed. Loss-of-function experiments indicated that GLP-1R deficiency accelerated cardiac transplant rejection and increased the infiltration and fibrosis of CD3+ and CD8+ T cells.

Conclusion

This study systematically revealed for the first time the regulatory role of GLP-1R in T cells, identifying it as a negative co-stimulatory molecule. GLP-1R signaling demonstrates significant immunoregulatory effects by extending transplant survival time and alleviating graft-versus-host reactions. Additionally, its antagonists exhibited potential anti-tumor immune activation abilities. These findings lay the groundwork for the clinical application of GLP-1R antagonists as immune checkpoint inhibitors to stimulate anti-tumor immunity, and they also offer new perspectives on the application of GLP-1R agonists in transplant immunity.

Research Highlights

1. Immunomodulatory Function of GLP-1R: This study highlights the crucial role of GLP-1R not only in metabolic regulation but also in the immune system.

2. Technological Applications: Extensive use of cutting-edge technologies such as single-cell RNA sequencing, immunohistochemistry, and mass spectrometry provides strong support for the accuracy and reliability of the results.

3. Clinical Application Potential: The research findings provide evidence for the potential application of GLP-1R antagonists in cancer immunotherapy, while also revealing the possible application of GLP-1R agonists in transplant immune regulation.

Limitations of the Study

Although the study reveals the critical regulatory role of GLP-1R in T cells, due to the widespread tissue expression of GLP-1R, some observed effects might not be entirely attributable to T cells. Also, in tumor models, only one type of mouse cancer model was tested, requiring further verification of its applicability and reproducibility in other cancer types.

Conclusion

Through comprehensive experiments and diverse technological approaches, this study thoroughly analyzed the expression and function of GLP-1R in T cells, revealing its important role as a negative co-stimulatory molecule in regulating immune responses. This provides new perspectives for the future clinical application of GLP-1R-related drugs in immunotherapy.