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Invariant chain can function as a chaperone protein for class II major histocompatibility complex molecules
1Committee on Immunology, University of Chicago, IL 60637.
Summary
Invariant chain (Ii) is crucial for proper folding and transport of major histocompatibility complex (MHC) class II molecules. Without Ii, MHC class II molecules misfold, leading to altered conformation and impaired cellular processing.
Area of Science:
- Immunology
- Molecular Biology
- Cell Biology
Background:
- Class II major histocompatibility complex (MHC) molecules associate with invariant chain (Ii) during biosynthesis.
- This association influences peptide binding and the final conformation of cell surface MHC class II.
Purpose of the Study:
- To biochemically analyze the effects of invariant chain (Ii) on the biosynthesis of MHC class II molecules.
- To understand the role of Ii in the folding, transport, and modification of MHC class II.
Main Methods:
- Biosynthesis analysis of MHC class II (I-Ad) in EL4 cells transfected with and without invariant chain (Ii).
- Assessment of molecular conformation, epitope expression, intracellular transport, and glycosylation.
Main Results:
- In the absence of Ii, MHC class II molecules formed misfolded dimers, losing epitopes and showing inefficient ER-Golgi transport.
- Transported MHC class II molecules exhibited abnormal N-linked glycosylation.
- Introduction of Ii restored normal MHC class II conformation, epitopes, transport, and glycosylation.
Conclusions:
- Invariant chain (Ii) profoundly impacts MHC class II folding, transport, and modification.
- Ii may function as a specific chaperone for MHC class II molecules, ensuring proper biosynthesis and cell surface expression.