Targeted protein degradation via NEDD8 conjugation does not enhance direct MHC class I antigen presentation.

Abstract

Abstract Knowledge of different pathways contributing to peptide generation for direct MHC class I antigen presentation is important to the field of immunotherapy. Here we investigated the role of the ubiquitin-like protein NEDD8 in antigen presentation. We show that proteins tagged N-terminally with NEDD8 undergo rapid degradation via the proteasomal, and autophagy-lysosomal pathways. To determine if protein NEDDylation increased peptide presentation, we fused NEDD8 to the N-terminus of a cytosolic form of ovalbumin (OVA) and measured presentation of the SIINFEKL peptide via the murine MHC class I molecule K b , and compared the results to ovalbumin N-terminally modified with ubiquitin. While NEDD8-OVA was processed for degradation via the proteasomal and autophagosomal pathway Ub-OVA was only degraded via the proteasome. Peptide presentation from NEDD8-OVA was dependent on NEDD8-ultimate buster 1 (NUB1), while autophagy did not contribute peptides antigen presentation. Overall, we found that N-terminal Ub conjugation was far more effective at generating antigenic peptides than N-terminal NEDD8 conjugation. However, upon inhibition of NEDDYylation by treatment with MLN4924, we did detect a decrease in peptide presentation from a model antigen used specifically to track Defective Ribosomal Product (DRiP) presentation. These data demonstrate that while NEDD8 can cause the rapid degradation of substrates it is not as efficient as Ubiquitin for generating antigenic peptides. Our data provides a basis for understanding the role of NEDD8 in protein degradation and antigen presentation, especially in conditions of NEDD8 dysregulation, such as in some cancers and protein folding pathologies.