A novel α/β T-cell subpopulation defined by recognition of EPCR

Abstract

T-cell self-recognition of antigen presenting molecules is led by antigen-dependent or independent mechanisms. The endothelial protein C receptor (EPCR) shares remarkable similarity with CD1d, including a lipid binding cavity. We identified EPCR-specific α/β T-cells in human peripheral blood of healthy donors. The average frequency in the CD3+ leukocyte pool is comparable to other autoreactive T-cell subsets that specifically bind MHC-like receptors. Alteration of the EPCR lipid cargo, revealed by X-ray diffraction studies, points to a prevalent, yet not exclusive, lipid-independent self-recognition. In addition, we solve the EPCR lipidome, and detect species not yet described as EPCR ligands. These studies report, for the first time, novel recognition by circulating α/β T-cells and provide grounds for EPCR and lipid mediated T-cell restriction.

Structure of EPCR in a non-canonical conformation

“…The question remains whether this novel folding arrangement represents a structural binding motif for other EPCR ligands, and which could determine relevant yet unknown roles of EPCR. In this line, recent works suggest EPCR-dependent T cell 11–13 and antibody 14 recruitment, which indicates that EPCR can interact with a broad variety of protein molecules.…”

“…Protein was eluted with 20 mM Hepes 7.4 supplemented with 150 mM NaCl and 200 mM imidazole. Purified protein was digested overnight with in-house made 3C protease 13 after imidazole removal. The tag-free protein was again loaded into the NiNTA Agarose cartridge and the flow through recovered.…”

Structural vulnerability in EPCR suggests functional modulation

“…The question remains whether this novel folding arrangement represents a structural binding motif for other EPCR ligands, and which could determine relevant yet unknown roles of EPCR. In this line, recent works suggest EPCR-dependent T cell 14 – 16 and antibody 17 recruitment, which indicates that EPCR can interact with a broad variety of protein molecules. Collectively, and in view of the results presented herein, the EPCR interactome and molecular plasticity is larger than originally expected, and further research is needed to address the molecular interaction potential of this receptor.…”