Regulation of expression of the leukocyte integrin CD11a (LFA-1) molecule during differentiation of HL-60 cells along the monocyte/macrophage pathway.
The CD11a/CD18 (LFA-1) leukocyte integrin receptor mediates homotypic and heterotypic leukocyte adhesion by binding to one of two defined ligands, ICAM-1 or 2, on the conjugate cell. In this study we investigated the molecular regulation of expression of the CD11a subunit during myeloid differentiation of HL-60 cells. Induction of monocyte/macrophage differentiation of HL-60 promyelocytic leukemia cells with PMA results in an increase in CD11a surface Ag expression and the acquisition of CD11a/CD18-mediated homotypic adherence. These changes are accompanied by a 40-fold increase in CD11a mRNA levels. Nuclear run-on transcription assays indicate that the increase in CD11a mRNA in PMA-induced HL-60 cells is not caused by an increase in CD11a RNA transcription. We assessed the posttranscriptional regulation of CD11a using two methods. By using actinomycin D to block RNA transcription, we demonstrate that the CD11a mRNA half-life in HL-60 cells is prolonged after PMA treatment. Inhibition of protein synthesis with cycloheximide also results in enhanced expression of CD11a mRNA in HL-60 cells without increasing CD11a transcription. These findings indicate that, in HL-60 cells induced with PMA to differentiate along the monocyte/macrophage pathway, CD11a expression is regulated primarily at the posttranscriptional level by a labile protein. Identification of the specific CD11a RNA sequences, and the proteins that bind to these sequences may provide insight into lineage commitment during human monocyte/macrophage differentiation.
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Medical Research Division, Seattle Veterans Administration Medical Center, WA 98108.
Gollahon
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Hickstein
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D015152:Blotting, Northern; D002454:Cell Differentiation / Q000187:drug effects; D002462:Cell Membrane / Q000378:metabolism; D015870:Gene Expression; D006801:Humans; D066298:In Vitro Techniques; D007951:Leukemia, Myeloid / Q000473:pathology; D016169:Lymphocyte Function-Associated Antigen-1 / Q000235:genetics*; D008264:Macrophages / Q000502:physiology*; D009000:Monocytes / Q000502:physiology*; D012333:RNA, Messenger / Q000235:genetics; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014158:Transcription, Genetic; D014407:Tumor Cells, Cultured
D016169:Lymphocyte Function-Associated Antigen-1; D012333:RNA, Messenger; D013755:Tetradecanoylphorbol Acetate