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  • Title: Distinctive epidermal growth factor receptor/extracellular regulated kinase-independent and -dependent signaling pathways in the induction of airway mucin 5B and mucin 5AC expression by phorbol 12-myristate 13-acetate.
    Author: Yuan-Chen Wu D, Wu R, Reddy SP, Lee YC, Chang MM.
    Journal: Am J Pathol; 2007 Jan; 170(1):20-32. PubMed ID: 17200179.
    Abstract:
    Elevated expression of gel-forming mucin (MUC) genes MUC5AC and MUC5B is a major pathological feature in various airway diseases. In this study, we show that phorbol 12-myristate 13-acetate (PMA) is a potent stimulator for MUC5B gene expression under air-liquid interface conditions in three airway epithelial cell systems: primary cultures of normal human bronchial epithelial cells, the immortalized normal bronchial epithelial cell line HBE1, and the human lung adenocarcinoma cell line A549. Stimulation was time- and dose-dependent, could be demonstrated by promoter-reporter gene transfection, and was sensitive to mithramycin A, suggesting the involvement of a specificity protein 1-based transcriptional mechanism in the stimulation. PMA-induced MUC5B message and promoter-reporter gene activity were specifically sensitive to inhibition of protein kinase C delta, which was further confirmed by the forced expression of dominant-negative mutant of protein kinase C delta. Regarding downstream transduction, PMA-induced MUC5B expression was sensitive to inhibitors and dominant-negative expression of signaling molecules involved in Ras/mitogen-activated protein kinase/extracellular signal-regulated kinase kinase kinase1-mediated c-Jun N-terminal kinase and p38 pathways. This contrasted with the inhibition of PMA-induced MUC5AC expression by inhibitors of the Ras/epidermal growth factor receptor/extracellular regulated kinase signaling pathway. These results demonstrate for the first time that PMA-stimulated MUC5AC and MUC5B expressions are regulated through distinctive epidermal growth factor receptor/extracellular regulated kinase-dependent and -independent signaling pathways.
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