N-terminal pyroglutamate in CD47 is involved in SIRPα interactions

ABSTRACT: T-cell immune checkpoint inhibitors have revolutionized cancer immunotherapy. In addition to T cells, immune checkpoint molecules have also been described for myeloid cells, with CD47 on tumor cells and Signal Regulatory Protein α (SIRPα) on effector cells being the most established example (Maute et al. Immunooncol Technol. 2022). Blockade of this checkpoint by CD47 or SIRPα targeting molecules has been demonstrated to enhance the efficacy of therapeutic antibodies in many preclinical tumor models (Müller et al. Blood. 2022, Schewe et al. Hemasphere. 2024). Next to CD47/SIRPα blocking molecules, inhibition of Glutaminyl-Peptide Cyclotransferase-Like (QPCTL) - the enzyme that catalyzes functionally relevant pyroglutamate (pGlu) formation on many peptides and proteins including CD47 - was shown to modify the myeloid tumor cell infiltrate (Barreira et al. Nat Immunol. 2022) and to improve antibody-dependent cellular phagocytosis (ADCP) and antibody-dependent cellular cytotoxicity (ADCC) against tumor cells (Logtenberg et al. Nat Med. 2019, Wu et al. Cell Res. 2019, Baumann et al. Front Immunol. 2021). Crystallographic analyses of CD47 in complex with SIRPα revealed that the CD47 binding pocket for SIRPα contains pGlu at the N-terminus (Hatherley et al. Mol Cell. 2008). However, on cellular level the direct involvement of pGlu in the CD47/SIRPα interaction has not been confirmed yet. We generated human CD47 Fc proteins, that contain either a native CD47 ectodomain with N-terminal pGlu (CD47-wt) or a mutated version with alanine at the N-terminus (CD47-Q1A), which was confirmed by mass spectrometry. Differential binding of CD47-wt and CD47-Q1A revealed that pGlu on CD47 is essential for binding to SIRPα on macrophages, supporting that inhibition of QPCTL is a good therapeutic option for enhanced tumor cell killing through CD47/SIRPα interference.

INSTRUMENT(S):

ORGANISM(S): Homo Sapiens (human) Cricetulus Griseus (chinese Hamster) (cricetulus Barabensis Griseus)

SUBMITTER: Oliver Valerius  

LAB HEAD: Thomas Valerius

PROVIDER: PXD066444 | Pride | 2026-05-19

REPOSITORIES: Pride