Impaired translation of CCAAT/enhancer binding protein α mRNA in bronchial smooth muscle cells of asthmatic patients

• Published in: Journal of allergy and clinical immunology Vol. 123; no. 3; pp. 639 - 645
• Main Authors: Borger, Peter, Miglino, Nicola, Baraket, Melissa, Black, Judith L., Tamm, Michael, Roth, Michael
• Format: Journal Article
• Language: English
• Published: United States Mosby, Inc 01.03.2009
• Subjects: Allergy and Immunology; Asthma; Asthma - genetics; Asthma - immunology; Asthma - metabolism; Bronchi - immunology; Bronchi - metabolism; bronchial smooth muscle cell hyperplasia; C/EBPα; Calreticulin - immunology; Calreticulin - metabolism; CCAAT-Enhancer-Binding Protein-alpha - biosynthesis; CCAAT-Enhancer-Binding Protein-alpha - immunology; Cell Proliferation; Cells, Cultured; Eukaryotic Initiation Factor-4E - immunology; Eukaryotic Initiation Factor-4E - metabolism; Heterogeneous-Nuclear Ribonucleoproteins - immunology; Heterogeneous-Nuclear Ribonucleoproteins - metabolism; Humans; Interleukin-6 - biosynthesis; Interleukin-6 - immunology; messenger RNA translation; Myocytes, Smooth Muscle - immunology; Myocytes, Smooth Muscle - metabolism; Protein Biosynthesis; RNA, Messenger - immunology; RNA, Messenger - metabolism; C/EBPα; C/EBP; eIF4E; LP; 4EBP; bronchial smooth muscle cell hyperplasia; Asthma; messenger RNA translation; PDGF; TCRS; mTOR; uORF; HA; BSM; SP; hnRNPE2; Platelet-derived growth factor; Heterogeneous nuclear ribonucleoprotein E2; Hemagglutinin; Translation control reporter system; Long peptide; Bronchial smooth muscle; Eukaryotic translation initiation factor 4E; Short peptide; CCAAT/enhancer binding protein; 4E binding protein; Mammalian target of rapamycin; Upstream open reading frame
• ISSN: 0091-6749; 1097-6825; 1097-6825
• DOI: 10.1016/j.jaci.2008.11.006

Bronchial smooth muscle (BSM) cells of asthmatic patients have an impaired expression of CCAAT/enhancer binding protein (C/EBP) α, which is associated with increased proliferation. We sought to assess the translational regulation of CEBPA mRNA in cultured BSM cells of healthy control subjects (n = 11) and asthmatic patients (n = 12). Translation efficiency was studied by using a translation control reporter system driven by the control elements present in the CEBPA mRNA. Translation efficiency was determined by the ratio of 2 artificial hemagglutinin (HA.11) proteins: p23 and p12. We also analyzed levels of proteins that control translation of CEBPA mRNA, namely heterogeneous nuclear ribonucleoprotein E2, calreticulin, eukaryotic translation initiation factor (eIF4E), and 4E binding protein. Compared with healthy control subjects, BSM cells of asthmatic patients proliferate faster (2.1-fold) and are primed for IL-6 secretion. Real-time RT-PCR showed that BSM cells of asthmatic patients express normal levels of CEBPA mRNA, whereas they express lower levels of C/EBPα (p42). Transient transfections with the translation control reporter system construct showed a disturbed p12/p23 ratio in BSM cells of asthmatic patients relative to healthy control subjects, which coincided with lower levels of eIF4E. BSM cells of asthmatic patients have normal levels of CEBPA mRNA but inadequately reinitiate the translation into C/EBPα. Impaired translation control upstream of eIF4E might underlie the observed increased proliferation and priming of BSM cells of asthmatic patients.