Mucin granule-associated proteins in human bronchial epithelial cells: the airway goblet cell granulomeReport as inadecuate

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Respiratory Research

, 12:118

First Online: 01 December 2011Received: 05 July 2011Accepted: 06 September 2011


BackgroundExcess mucus in the airways leads to obstruction in diseases such as chronic bronchitis, asthma, and cystic fibrosis. Mucins, the highly glycosolated protein components of mucus, are stored in membrane-bound granules housed in the cytoplasm of airway epithelial -goblet- cells until they are secreted into the airway lumen via an exocytotic process. Precise mechanisms of mucin secretion, including the specific proteins involved in the process, have yet to be elucidated. Previously, we have shown that the Myristoylated Alanine-Rich C Kinase Substrate MARCKS protein regulates mucin secretion by orchestrating translocation of mucin granules from the cytosol to the plasma membrane, where the granules dock, fuse and release their contents into the airway lumen. Associated with MARCKS in this process are chaperone Heat Shock Protein 70 HSP70, Cysteine string protein CSP and cytoskeletal actin, myosin proteins. However, additional granule-associated proteins that may be involved in secretion have not yet been elucidated.

MethodsHere, we isolated mucin granules and granule membranes from primary cultures of well differentiated human bronchial epithelial cells utilizing a novel technique of immuno-isolation, based on the presence of the calcium activated chloride channel hCLCA1 the human ortholog of murine Gob-5 on the granule membranes, and verified via Western blotting and co-immunoprecipitation that MARCKS, HSP70, CSP and hCLCA1 were present on the granule membranes and associated with each other. We then subjected the isolated granules-membranes to liquid chromatography mass spectrometry LC-MS-MS to identify other granule associated proteins.

ResultsA number of additional cytoskeletal e.g. Myosin Vc and regulatory proteins e.g. Protein phosphatase 4 associated with the granules and could play a role in secretion were discovered. This is the first description of the airway goblet cell -granulome.-

Electronic supplementary materialThe online version of this article doi:10.1186-1465-9921-12-118 contains supplementary material, which is available to authorized users.

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Author: Kimberly L Raiford - Joungjoa Park - Ko-Wei Lin - Shijing Fang - Anne L Crews - Kenneth B Adler


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