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Modulation of class I major histocompatibility complex antigen cell-surface stability by transmembrane domain length
C K Osborn1, V Grigoriev, M D Crew
1Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences, Little Rock 72205, USA.
Molecular Immunology
|August 1, 1997
Summary
Altering the length of transmembrane domains (TMs) in human leukocyte antigen (HLA) class I proteins significantly impacts their cell surface stability. Longer TMs correlate with decreased protein levels on the cell surface, independent of other protein regions.
Area of Science:
- Immunology
- Molecular Biology
- Cell Biology
Background:
- Major histocompatibility complex (MHC) class I proteins are crucial for immune surveillance.
- Their cell surface localization is influenced by transmembrane domains (TMs), which show significant variation.
- Understanding TM variation's impact on protein trafficking and stability is key to immune function.
Purpose of the Study:
- To investigate how variations in the length of transmembrane domains (TMs) affect the cell surface localization and stability of human leukocyte antigen (HLA) class I proteins.
- To determine if TM length variation impacts protein trafficking and cell surface expression independently of other protein domains.
Main Methods:
- Utilized human leukocyte antigen (HLA)-A2 gene constructs with modified transmembrane domain lengths in transformed B lymphocytes (CIR cells).
- Assessed cell surface protein levels, intracellular trafficking rates, and protein stability using brefeldin A treatment.
- Compared wild-type HLA-A2 with variants having elongated TMs and TMs with different amino acid compositions.
Main Results:
- Enlarging the TM of HLA-A2 by 12 hydrophobic amino acids markedly decreased its steady-state cell surface levels.
- This reduction in surface expression was observed regardless of the cytoplasmic domain's presence and was not due to altered beta2-microglobulin association.
- Diminished cell surface levels were primarily attributed to decreased cell surface stability, showing a negative correlation with TM length.
Conclusions:
- Transmembrane domain length is a critical determinant of human leukocyte antigen (MHC) class I protein cell surface stability.
- Variations in MHC class I TM length can significantly affect cell surface expression, independent of amino acid sequence or cytoplasmic domain interactions.
- This TM length-dependent regulation may play a role in modulating immune responses.