IMMUNO-RQC · Role of Listerin ubiquitin ligase in MHC-I antigen presentation
Horizon 2020 — Marie Skłodowska-Curie Actions
- Duration
- 2017-05-01 → 2019-04-30
- EU contribution
- €159,461
- Participants
- 1
- Scheme
- MSCA-IF-EF-ST
Lines connect the coordinator with its partners.
Results in brief
Role of Listerin ubiquitin ligase in MHC-I antigen presentation
Mammalian cells present their proteome content to the adaptive immune system through the display of peptides on MHC-I complexes. This allows for CD8+ T cells to selectively recognize and kill cells that present non-self antigens, for example due to viral infection or cancer transformation. The MHC-I peptides originate from protein degradation by the ubiquitin proteasome system, implicating that optimally-folding, long-lived proteins could be difficult to monitor in a timely fashion. To explain the kinetic discrepancy between protein half-life and MHC-I presentation, Defective Ribosomal Products (DRiPs) have been proposed to act as a significant source of self and viral peptides. Accordingly, cells exploit DRiP degradation for efficient processing of antigenic peptides. However, the underlying protein quality control pathways responsible for the efficient presentation of newly synthesized proteins remain elusive. The main goal of this project was to investigate the role of the Ribosomal Quality Control (RQC) pathway in sampling peptides for antigen presentation. The project therefore addresses a fundamental question in the field of immunology: how do cells ensure timely presentation of newly synthesized proteins. Understanding how this basic process works could potentially aid the development of new therapies, for example, for improving the immune-response to viral infections and cancers, or for attenuating auto-immune diseases. In the course of the action we showed that the RQC machinery generates antigenic peptides from nascent chains encoded by defective mRNA molecules, and that this is independent of folding efficiency. Furthermore, we demonstrated that RQC degradation substantially contributes to the composition of the immunopeptidome. The RQC contribution is especially pronounced for folding-efficient proteins where sampling might be difficult, as is expected to be the case for many viral proteins. Our analysis also provides the first dataset of natural RQC degradation substrates in human cells, providing new insights into this still largely uncharacterized degradation pathway.
Data: CORDIS, © European Union
Project objective
Mammalian cells present a fingerprint of their proteome through the display of endogenous peptides on MHC-I complexes. This allows for CD8+ T cells to recognize and kill cells infected with viruses or other intracellular parasites, or cells accumulating aberrant proteins resulting from malignant transformation. The MHC-I peptides originate from protein degradation by the ubiquitin proteasome system, which is responsible for controlled protein turnover. This would mean that viral proteins, which are typically very stable, would escape monitoring. Nevertheless, cells are able to mount an MHC-I immune response minutes after viral infection. Most MHC-I presented peptides are therefore thought to originate from newly synthesized, defective ribosomal products (DRiPs), rather than proteins at the end of their lifespan. Although there is a growing body of evidence showing that antigen presentation is better correlated with protein synthesis rather than protein stability, characterization of the underlying cellular pathway is lacking. Recently, the E3 ubiquitin ligase Listerin has been shown to mark nascent polypeptides resulting from defective mRNAs for degradation. Here we test the hypothesis that this pathway contributes to the production of peptides for MHC-I loading. Our major aim is therefore to investigate the involvement of Listerin in antigen presentation, using 3 different approaches: I) proof-of-principle experiments analyzing the rate of MHC-I presentation of a model protein, comparing the efficiency of its presentation when expressed from an intact or defective mRNA, and when expressed in WT or Listerin knock-out cells; II) global characterization of the MHC-I peptidome of WT and Listerin knock-out cells using mass spectrometry; III) quantitative analysis of the fraction of newly-synthesized proteins undergoing the RQC pathway, and of its possible correlation with the MHC-I peptidome.
Original text from CORDIS.
Participants
- MAX-PLANCK-GESELLSCHAFT ZUR FORDERUNG DER WISSENSCHAFTEN EV · MUNCHENCoordinatorGermany
Links
Data: CORDIS, © European Union