Functional Genomics of Mucin Secretion in the Airway Epithelium

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Title: Functional Genomics of Mucin Secretion in the Airway Epithelium
Author: Raiford, Kimberly Lizell
Advisors: James Bonner, PhD, Committee Member
Matthew Breen, PhD, Committee Member
Kenneth Adler, PhD, Committee Chair
Anthony Blikslager, DVM, PhD, Committee Member
Abstract: Mucin secretion of the airways is an exocytotic event that can cause substantial problems when it is imbalanced. Disproportionately large levels of mucin secretion can lead to impaired mucociliary function, increased susceptibility to bacterial pathogens, vivification of inflammatory responses, and, in extreme cases, death. The process of regulated exocytosis in the airway epithelium is still poorly understood, eventhough the result of its inaccuracies are potentially so deleterious. Previously, studies from our lab demonstrated that Myristoylated Alanine-Rich C Kinase substrate protein (MARCKS) regulated mucin secretion in in vitro cultures of human bronchial epithelial cells and in mice in vivo. It is our hypothesis that MARCKS mediates the exocytotic release of mucin from preformed membrane-bound mucin granules by facilitating granule movement from the cytosol to the plasma membrane where the granule docks, fuses and secretes its contents into the airway lumen. In these studies, we use proteomics to elucidate novel proteins involved in the molecular mechanisms of mucin secretion that are associated with the mucin granule. These studies will greatly contribute to our understanding of proteins involved in regulated exocytosis potentiating therapeutics with new targets. In the first study, we elucidate some aspects of the regulated exocytosis mechanism whereby MARCKS, hCLCA1, and chaperones cysteine string protein and heat shock proteins interact in a complex. We found that these proteins form a complex that is associated with the mucin granule in normal bronchial epithelial cells grown using the in vitro air-liquid interface culture system. We further elucidated novel proteins that also associate with the mucin granule most of which are cytoskeletal related. The second study elucidates proteins associated with the mucin granules in unstimulated and stimulated conditions further expanding the study to include a diseased model, cystic fibrosis cell line UNCN3T, and the intestinal cell line HT29-18N2. We found that many of the proteins are conserved across the cell types suggesting possible conservation in regulated exocytosis machinery involved in mucin secretion. Overall, these studies elucidate potential players in the mechanism of mucin secretion. These data provide the first proteomic analysis of mucin granule membrane associated proteins in airway epithelial cell.
Date: 2009-04-28
Degree: PhD
Discipline: Functional Genomics

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