Open AccessThe effect of excess beta-chain synthesis on cell-surface expression of allele-mismatched class II heterodimers in vivo.
Author(s) -
Susan Gilfillan,
Sadakazu Aiso,
Sara A. Michie,
Hugh O. McDevitt
Publication year - 1990
Publication title -
proceedings of the national academy of sciences of the united states of america
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.011
H-Index - 771
eISSN - 1091-6490
pISSN - 0027-8424
DOI - 10.1073/pnas.87.18.7314
Subject(s) - transgene , beta (programming language) , microbiology and biotechnology , biology , alpha (finance) , genetically modified mouse , in vivo , allele , messenger rna , gene expression , cell , cell culture , gene , biochemistry , genetics , medicine , construct validity , nursing , computer science , patient satisfaction , programming language
We have recently described 12 lines of H-2s/s mice carrying from 1 to 65 copies of an A beta k transgene. The transgene was coexpressed with the endogenous allele, and A beta K mRNA expression correlated well with transgene copy number. Overexpression of the transgene was associated with a variety of defects, including a significant reduction in I-A cell-surface expression. In this paper, we assess the effect of increased levels of A beta k mRNA synthesis on I-A cell-surface expression in these mice. Crossing representatives from several lines of A beta k mice to A alpha k transgenic mice demonstrated that the A beta k mRNA was translated and expressed at high levels on the cell surface in association with A alpha k. In H-2s/s (A alpha s /A beta s) mice carrying greater than 10 copies of the A beta k transgene, excess A beta k mRNA and protein synthesis did drive cell-surface expression of the less favored A alpha s/A beta k heterodimers. However, the highest levels of A beta k detected on the cell surface were only 50-70% of those observed in [B10.A(4R) x nontransgenic]F1 controls. Maximum levels of A alpha s/A beta k cell-surface expression were accompanied by a significant reduction in A alpha s/A beta s expression. Unpaired and improperly paired complexes were not detected intracellularly and appeared to be degraded quite rapidly. Thus, only a fraction of the chains competing for pairing reached the cell surface under conditions of asymmetric chain synthesis in these mice. This markedly reduced total Ia cell-surface levels in mice carrying greater than 10 copies of the A beta k transgene.