LPS upregulates MHC class II I-A expression in B lymphocytes at transcriptional and at translational levels.
Major histocompatibility complex (MHC) class II molecules are expressed in a limited number of cell types, including B lymphocytes, dendritic cells and macrophages. Lipopolysaccharide (LPS) increases the surface expression of class II molecules in a murine B-cell line by inducing an increase in I-A protein and I-A mRNA levels. LPS does not modify the rate of mRNA degradation; therefore, the increase in mRNA is due to an increase in transcription. In addition, LPS increases the levels of I-Aalpha protein, which correlates with an increase in ribosome loading for I-Aalpha but not for I-Abeta mRNA after treatment with LPS. Interestingly, in non-induced cells, I-Aalpha messenger RNA shows a significant peak of free mRNA. Therefore, LPS regulates the expression of MHC class II molecules at translational level in B cells, in addition to the transcriptional control. The actual mechanism implies changes of translation initiation rates, as shown by an increase ribosome loading in polysome gradients.
Barrachina
M
M
Departament de Fisiologia (Biologia del Macròfag), Facultat de Biologia and Fundació August Pi i sunyer, Universitat de Barcelona, Spain.
Goñalons
E
E
Celada
A
A
D000818:Animals; D001402:B-Lymphocytes / Q000737:chemistry / Q000166:cytology / Q000502:physiology*; D015152:Blotting, Northern; D015153:Blotting, Western; D002460:Cell Line; D003609:Dactinomycin / Q000494:pharmacology; D000949:Histocompatibility Antigens Class II / Q000032:analysis / Q000235:genetics*; D008070:Lipopolysaccharides / Q000494:pharmacology*; D051379:Mice; D011132:Polyribosomes / Q000235:genetics / Q000276:immunology; D014176:Protein Biosynthesis / Q000187:drug effects* / Q000276:immunology; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D012333:RNA, Messenger / Q000032:analysis / Q000378:metabolism; D012337:RNA, Ribosomal, 18S / Q000032:analysis; D014158:Transcription, Genetic / Q000187:drug effects* / Q000276:immunology
D000949:Histocompatibility Antigens Class II; D008070:Lipopolysaccharides; D011500:Protein Synthesis Inhibitors; D012333:RNA, Messenger; D012337:RNA, Ribosomal, 18S; D003609:Dactinomycin