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Updated: Jul 11, 2026

Purification of the Membrane Compartment for Endoplasmic Reticulum-associated Degradation of Exogenous Antigens in Cross-presentation
Published on: August 21, 2017
A novel cytosolic class I antigen-processing pathway for endoplasmic-reticulum-targeted proteins
Eva Schlosser1, Carolina Otero, Christine Wuensch
1Division of Immunology, Department of Biology, Postbox M661, Universitatstrasse 10, University of Constance, Konstanz D-78457, Germany.
Signal peptidase cleavage prevents T-cell recognition of prostate stem cell antigen epitopes. This study reveals a novel pathway for generating major histocompatibility complex class I epitopes from ER-targeted proteins that fail to reach the ER.
Area of Science:
- Immunology
- Molecular Biology
- Cell Biology
Background:
- Proteins with endoplasmic reticulum (ER) leaders are processed for T-cell recognition after proteasomal degradation and retrotranslocation.
- Major histocompatibility complex (MHC) class I-restricted T-cell epitopes are typically generated from cytosolic proteins.
Purpose of the Study:
- To investigate the processing of prostate stem cell antigen (PSCA) and its impact on T-cell epitope generation.
- To elucidate a novel pathway for MHC class I antigen processing.
Main Methods:
- Analysis of PSCA processing by ER signal peptidase.
- Assessment of HLA-A(*)0201 binding to PSCA cleavage products.
- T-cell recognition assays.
- Investigation of proteasome and transporter associated with antigen processing (TAP) involvement.
Main Results:
- The HLA-A(*)0201-restricted epitope of PSCA contains the ER signal peptidase cleavage site.
- Cleavage by signal peptidase results in products that do not bind to HLA-A(*)0201 and are not recognized by T lymphocytes.
- This processing occurs during co-translational insertion, before proteins reach the ER.
- Epitope generation depends on the proteasome and TAP, indicating processing of ER-targeted proteins that fail to enter the ER.
Conclusions:
- Signal peptidase processing of PSCA interferes with the generation of a relevant T-cell epitope.
- A novel MHC class I processing pathway exists for ER-targeted proteins that are prematurely processed and do not reach their intended cellular compartment.
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