Structures of mouse and human GITR\u2013GITRL complexes reveal unique TNF superfamily interactions

Feng Wang,Barbara Aguilar,Flavio Schwarz,Pavel Strop,Bryant Chau,Sean M West,Arvind Rajpal,Christopher R Kimberlin,Christine Bee,Gavin Dollinger,Minhua Han,Winse Morishige,Fei Cao

doi:10.1038/s41467-021-21563-z

Abstract

Glucocorticoid-induced tumor necrosis factor receptor-related protein (GITR) and GITR ligand (GITRL) are members of the tumor necrosis superfamily that play a role in immune cell signaling, activation, and survival. GITR is a therapeutic target for directly activating effector CD4 and CD8 T cells, or depleting GITR-expressing regulatory T cells (Tregs), thereby promoting anti-tumor immune responses. GITR activation through its native ligand is important for understanding immune signaling, but GITR structure has not been reported. Here we present structures of human and mouse GITR receptors bound to their cognate ligands. Both species share a receptor–ligand interface and receptor–receptor interface; the unique C-terminal receptor–receptor enables higher order structures on the membrane. Human GITR–GITRL has potential to form a hexameric network of membrane complexes, while murine GITR–GITRL complex forms a linear chain due to dimeric interactions. Mutations at the receptor–receptor interface in human GITR reduce cell signaling with in vitro ligand binding assays and minimize higher order membrane structures when bound by fluorescently labeled ligand in cell imaging experiments.

Highlights

Glucocorticoid-induced tumor necrosis factor receptor-related protein (GITR) and GITR ligand (GITRL) are members of the tumor necrosis superfamily that play a role in immune cell signaling, activation, and survival
We expressed mouse GITRL and determined the 3.2 Å structure of the dimeric murine GITR (mGITR)–murine GITRL (mGITRL) complex to compare with the human complex (Table 1, Fig. S2)
We describe the structure of GITR bound to its native ligand

Summary

Introduction

Glucocorticoid-induced tumor necrosis factor receptor-related protein (GITR) and GITR ligand (GITRL) are members of the tumor necrosis superfamily that play a role in immune cell signaling, activation, and survival. The tumor necrosis factor (TNF) superfamily of ligands and receptors (TNFSF and TNFRSF) play an important role in cell signaling, activation, and survival. Reported crystal structures of human GITR ligand (hGITRL) revealed oligomerization interface with little sequence conservation to other TNF ligands. This interface is similar to other ligands with aromatic/hydrophobic residues packing at the interface and with a characteristic β-sandwich “jelly roll” topology that self-assembles into homotrimers[15,16], which may mediate the 3:3 ligand/receptor complex formation found in other TNF members. The C-terminal receptor–receptor interactions may play an important role mediating GITR–GITRL complex clustering and GITR network formation on the cell surface

Methods

Results

Conclusion