Regulation of Airway Goblet Cell Mucin Secretion

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DESCRIPTION: The obstructive pulmonary diseases (OPD), cystic fibrosis, chronic bronchitis, bronchiectasis, emphysema, and asthma, are inflammatory diseases with very different inflammatory cell profiles, cytokine responses, etc; mucin hypersecretion from airway surface goblet cells and submucosal mucous cells represents a singular, shared characteristic. Conceptually, mucin hypersecretion may result from inflammation-driven goblet cell meta/hyperplasia and/or elevated rates of mucin secretion. Although the best long-term treatment for OPDs will likely target the individual causes of inflammation, it is notable that acute relief to OPD patients, generally, could be achieved by selectively inhibiting mucin secretion. Possibly more important, such an inhibitor would help to open mucus-clogged airways to enable efficient, inhalation-based treatment of the underlying disease. Hence, our long-range goal is to study the molecular mechanisms by which mucin granule exocytosis in airway goblet cells is regulated, to identify molecular targets for selective drug therapies. It is well known that goblet cell mucin secretion is regulated by extracellular ATP and UTP acting through the P2Y2 receptor (P2Y2-R), and that the subsequent secretory response is mediated by the phospholipase C pathway through PKC and Ca2+. Yet, our knowledge of the signaling pathways involved in goblet cell regulation is incomplete. For instance, the effects of muscarinic agonists are highly controversial, there are no data relevant to the mechanisms and pathways underlying the regulation of basal mucin secretion from airway goblet cells, and the effects of agents signaling through receptors acting via tyrosine kinase pathways are uknown, though many of them do have metaplastic effects on the airways epithelium. At the molecular level, we know very little of the effectors regulating exocytosis beyond the identities of the intracellular messengers. Hence, we propose a broadly based approach using the primary cultures of human bronchial epithelial cells, airways epithelium from human lungs and genetically manipulated mice rendered metaplastic for goblet cells, and SPOC1 goblet cells to further delineate the intracellular molecular regulation of mucin granule exocytosis from airway goblet cells, and to extend our knowledge of the signaling pathways regulating goblet cell function into new areas involving basal mucin secretion, type I receptor and involvement, and mechanical shear effects.