Cytoplasmic Domain Affects Membrane Expression and Function of an Ia Molecule

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 85; no. 13; pp. 4847 - 4851
• Main Authors: Griffith, Irwin J., Ghogawala, Zoher, Nabavi, Nasrin, Golan, David E., Myer, Anita, McKean, David J., Glimcher, Laurie H.
• Format: Journal Article
• Language: English
• Published: Washington, DC National Academy of Sciences of the United States of America 01.07.1988; National Acad Sciences
• Subjects: Amino Acid Sequence; Animals; Antigen presentation; Antigen presenting cells; Antigen-Presenting Cells - immunology; Antigens; B lymphocytes; Base Sequence; Biological and medical sciences; Cell lines; DNA - genetics; Fundamental and applied biological sciences. Psychology; Fundamental immunology; Gels; Half lives; Histocompatibility antigens (hla, h-2 and other systems); Histocompatibility Antigens Class II - genetics; Histocompatibility Antigens Class II - immunology; Hybridomas - immunology; Mice; Molecular immunology; Molecular Sequence Data; Molecular weight; Molecules; Protein Conformation; T lymphocytes; Antigen presentation; Vertebrata; Mammalia; Mouse; Topography; Rodentia; Class II histocompatibility antigen; Plasma membrane; Gene expression; Structure function relationship
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.85.13.4847

The association of foreign antigen with Ia molecules on the surface of antigen-presenting cells is necessary for the interaction with the clonally distributed antigen receptor on T cells and is therefore critical in the initiation and regulation of immune responses. Ia polypeptides (α and β ) are composed of two extracellular domains, a transmembrane domain and a cytoplasmic domain. Although exon-shuffling experiments have demonstrated that antigen associates with the NH2-terminal α 1 and β 1 domains, the roles that the other domains play in Ia function are still poorly understood. The B-hybridoma cell line 2B1 was selected in a series of positive and negative immunoselection steps for a mutation in the Eβk polypeptide. It was found to fortuitously contain a mutation in the Aαk polypeptide as well. Sequence analysis of the Aαk gene showed that a single base transition (C→ T) resulted in a stop codon at amino acid residue 222. This caused the loss of 12 amino acids from the cytoplasmic domain of the mature polypeptide. This mutation results in a decreased level of Aαk polypeptide expression on the cell surface (50% of wild-type levels), an increased half-life of Aαk polypeptide in the cell, and a specific limited defect in antigen presentation.