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Processing and major histocompatibility complex binding of the MTV7 superantigen
G M Winslow1, P Marrack, J W Kappler
1Howard Hughes Medical Institute, Department of Medicine, National Jewish Center for Immunology and Respiratory Medicine, Denver, Colorado 80206.
Immunity
|April 1, 1994
Summary
Mouse mammary tumor virus superantigens (vSAGs) bind to MHC class II molecules. Researchers characterized vSAG7, finding it processed and stably bound to MHC class II, with a processed form dominating the bound material.
Area of Science:
- Immunology
- Virology
- Molecular Biology
Background:
- Mouse mammary tumor viruses produce superantigens (vSAGs) that interact with class II major histocompatibility complex (MHC) proteins, stimulating T cells.
- vSAGs are synthesized as Type II membrane proteins, with some, like vSAG7, appearing cell-surface bound in a processed form.
Purpose of the Study:
- To characterize the viral superantigen vSAG7.
- To investigate the binding of vSAG7 to class II major histocompatibility complex (MHC) molecules.
Main Methods:
- Utilized monoclonal antibodies (MAbs) for vSAG7 characterization.
- Analyzed vSAG7 synthesis, glycosylation, and proteolytic processing in the endoplasmic reticulum (ER) and Golgi complex.
- Assessed the binding stability of vSAG7 forms to class II molecules.
Main Results:
- vSAG7 is synthesized as a 45 kd glycoprotein in the ER with N-asparagine-linked oligomannosyl carbohydrates.
- vSAG7 undergoes modification with complex-type glycans and proteolysis at three sites in the Golgi.
- All forms of vSAG7 (ER, Golgi, surface) stably bind to class II molecules, with a proteolysed form being the most abundant class II-bound species.
Conclusions:
- vSAG7 exhibits complex post-translational modifications including glycosylation and proteolytic cleavage.
- vSAG7 demonstrates stable, noncovalent association with class II major histocompatibility complex (MHC) molecules.
- A specific proteolysed form of vSAG7 is the predominant species interacting with class II MHC.