The Gao Fu team of the Chinese Academy of Sciences Institute of Microbiology has made important progress in the research of GITR/GITRL recognition mechanism

Tumor necrosis factor superfamily (tumor necrosis factor superfamily, TNF superfamily) related molecules are the key to natural/acquired immune regulation and function.
Many members of this family are drug targets for tumor immunotherapy and anti-inflammatory drug development
.

Active immune checkpoint molecules such as 4-1BB and GITR are members of the TNF receptor (TNFR) superfamily that have attracted much attention in recent years.
There are many antibody drugs in the clinical verification stage around the world, and their ligand binding mechanism and antibody drug effects Mechanism research has important reference value for the development of new immunotherapy strategies
.

In the previous research, the Gao Fu team clarified the molecular basis of the action of 4-1BB and its ligands and activated antibodies, which is of great significance for understanding the molecular basis of 4-1BB activation and the development of antibody drugs (Li Y.
, et al.
, 2018.
Cell Reports)
.

The team recently reported on the "atypical" interaction mechanism between the costimulatory receptor glucocorticoid-induced tumor necrosis factor receptor family-related protein (GITR) and its ligand GITRL.
The results of the study were published in the journal Cell Reports
.

The structure of the GITR/GITRL complex and the “DIV/KFS” motif that determines the binding specificity of GITR.
GITR is an immune checkpoint molecule involved in the regulation of T cell responses.
Activated monoclonal antibodies targeting GITR have shown good results in clinical studies.
The drug tolerance and significant tumor suppressor activity
.

GITR and its ligand GITRL are important members of the TNF/TNFR superfamily
.

Previous studies generally believe that the receptor-ligand binding mode in the TNF/TNFR superfamily is highly conserved.
The receptor molecule and the trimer ligand combine in a ratio of 1:1 to form a "3+3" complex.
The TNFR molecule is generally Combining with the side fissure region formed by two adjacent TNF molecules, receptor cross-linking mediated by trimer ligands is considered to be the basic mode of receptor signal activation
.

Through the analysis of the mouse-derived GITR/GITRL complex crystal structure and a series of cell/protein level experiments, it was found that two monomeric GITR molecules and the two-body GITRL form a "2+2" complex, and GITR binds to GITRL through its CRD2 domain.
The binding surface between the two is completely different from the classic TNF/TNFR superfamily molecules.
N149 located in GITRL and D93-I94-V95 located in GITR determine the main interaction between receptor/ligand, indicating that GITR/GITRL Different from the "atypical" interaction mode of the classic TNF/TNFR superfamily
.

The phenomenon that a single domain of GITR mediates its binding to ligand suggests that this unique mode of action may be an older binding mode in the evolution of the TNF/TNFR superfamily, while other TNFR superfamily member molecules and ligands Binding has often evolved into two different domains mediated binding specificity and high affinity
.

The study also found that the D93-I94-V95 (DIV) in mouse GITR and the corresponding K105-F106-S107 (KFS) region in human GITR determine the species specificity of the binding of the receptor to its ligand
.

Although mouse-derived and human-derived GITR/GITRL cannot be cross-recognized, mouse GITR ligand binding key sites "DIV" to "KFS" mutations lead to cross-recognition with human GITRL, and in the NFAT-Luc-Jurkat T cell signaling model Induces T cell activation signals
.

The GITR/GITRL discovered in this study is different from the "atypical" interaction mode of the classic TNF/TNFR superfamily, which not only expands our understanding of the molecular interaction mode of the TNF/TNFR superfamily, but is also based on the GITR/GITRL interaction.
The drug design provides a theoretical basis
.


In recent years, the team has carried out a series of research work on the ligand recognition mechanism of immune checkpoint receptor molecules and the mechanism of antibody drug action.
The research results have been published in "Cell Research", "PNAS", "Nature Communications", "Cell Reports", and EMBO Reports, etc.
, provide an important theoretical basis for understanding the T cell immune regulation mechanism and the development of drugs based on immune checkpoint molecules
.

Zhao Min, an assistant researcher at the Institute of Microbiology, Chinese Academy of Sciences, and Fu Lijun, a postgraduate student jointly trained by Jiangxi Science and Technology Normal University, are the co-first authors of the study.
Academician Gao Fu and associate researcher Tan Shuguang of the Institute of Microbiology are the co-corresponding authors
.

The research was supported by the pilot project of the Chinese Academy of Sciences and the major special project of the Ministry of Science and Technology
.

Link to the paper: https://