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Class I molecules retained in the endoplasmic reticulum bind antigenic peptides
C K Lapham1, I Bacík, J W Yewdell
1Laboratory of Viral Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland 20892.
The Journal of Experimental Medicine
|June 1, 1993
Summary
Researchers found that viral peptides bind to major histocompatibility complex (MHC) class I molecules within an early cellular compartment, before the molecules are exported from the cell. This occurs even when the normal export pathway is blocked.
Area of Science:
- Immunology
- Virology
- Cell Biology
Background:
- Major histocompatibility complex (MHC) class I molecules present viral peptides to cytotoxic T lymphocytes, initiating an immune response.
- The precise intracellular location and timing of peptide loading onto MHC class I molecules remain incompletely understood.
Purpose of the Study:
- To investigate the intracellular site of peptide association with MHC class I molecules during viral infection.
- To determine if peptide loading occurs before or after MHC class I molecules enter the standard secretory pathway.
Main Methods:
- Infection of cells with influenza virus in the presence of brefeldin A to block protein export.
- Isolation of MHC-specific viral peptides from treated cells.
- Expression of engineered MHC class I molecules with a substituted cytoplasmic domain, retained in an intracellular compartment.
- Immunocytochemical and biochemical analyses to confirm protein localization.
Main Results:
- MHC class I-specific viral peptides were successfully isolated from influenza virus-infected cells treated with brefeldin A.
- Engineered MHC class I molecules, retained in a pre-Golgi compartment, were found to associate with viral peptides.
- Intracellular association of peptides with retained MHC class I molecules was demonstrated to be essential for their isolation.
Conclusions:
- Naturally processed viral peptides associate with MHC class I molecules in an early intracellular exocytic compartment, prior to their transport through the Golgi apparatus.
- This study provides direct evidence for the site of peptide loading onto MHC class I molecules within the secretory pathway.