Mechanism of smoke-induced MUC5B gene expression
Creators: name: University Of California Office Of The President
Publisher: name: University of California Office of the President
publisherIdentifier: https://ror.org/00dmfq477
publisherIdentifierScheme: ROR
Year: 2024

description: Mucins are major contributors to the visco-elastic properties of mucus secretion, which plays an important role in the mucociliary clearance in conducting airways. Hyper-mucus secretion and hyper-mucin production in airway lumen are frequently seen in various airway diseases and tobacco smoke is one of the major contributors to the development of various airway diseases. The nature of the smoke effect on mucin production is not known. We have recently demonstrated the expression of MUC5B message in surface airway epithelia of human tissues from patients with various airway diseases, including those are caused by tobacco smoke, such as emphysema, chronic bronchitis, etc. The expression of MUC5B message is normally seen in the mucous cells of the submucosal gland in airway tissues with no obvious inflammation and infection. In contrast, the expression of MUC5AC message, the other important mucin gene in airway mucin, is strictly seen in the surface epithelia. Thus, the expression of MUC5B by surface airway epithelium represents a trans-epithelial cell differentiation that is closely related to the symptom pathogenesis. Our preliminary studies in both primary human tracheobronchial epithelial (TBE) cultures and in vivo transgenic mice have demonstrated an elevation of MUC5B gene expression by tobacco smoke. The goal of this application is to elucidate the molecular mechanism involved in the smoke-induced MUC5B gene expression. The major hypothesis will be tested is that smoke enhances the transcription of MUC5B gene. To test this hypothesis, three specific aims are proposed. Aim 1 is to test the hypothesis that cis-elements at the 5'-flanking region of MUC5B gene are responsible for smoke-induced gene expression. To address this aim, in vivo and in vitro genomic footprintings will be used to identify the location of cis-elements involved in smoke-induced mucin gene expression. In addition, various promoter-reporter gene chimeric constructs will be prepared and used to elucidate the functional significance of cis-elements in transfection study. Aim 2 is to test the hypothesis that smoke-induced MUC5B expression involves the activation of mitogen-activated protein kinase (MAPK) signaling pathway. To address this aim, various mediators for different MAPK pathways will be used to attenuate smoke-induced MUC5B gene expression. Various dominant negative as well as constitutively active mutants of various MAPK signaling genes will be used to modulate the promoter activity in transfection study. These approaches will prove important information regarding to the mechanism and signaling pathway involved in smoke-induced MUC5B gene expression. To address the importance of these findings in vivo, transgenic mice carrying human MUC5B promoter-reporter gene (luciferase) chimeric construct will be used and exposed to smoke (Aim 3). We will test the hypothesis that both tissue-specific and smoke-inducible gene expression activities are preserved in the 5'-flanking region of human MUC5B gene. These studies will demonstrate the molecular pathway that regulates MUC5B gene expression by smoke.