The overall goal of this project is to understand the role of gallbladder mucin in the pathogenesis of cholesterol gallstones. Medical or surgical treatment for symptomatic gallstones is a frequent cause for hospitalization in the United States and consumes more than 8 billion dollars in health care costs per year. Gallbladder mucin has been shown to have a central role in gallstone pathogenesis. Mucin hypersecretion occurs prior to stone formation in both experimental animals and man. Mucin also promotes cholesterol crystal nucleation, a critical early step in stone formation, and the mucin gel lining. The gallbladder provides an ideal environment for growth of cholesterol crystals into mature stones. Human gallbladder expresses genes for five different mucins and two of these, MUC5B and MUC3 have been identified as the major human gallbladder mucins. Nothing is known about the structural features of these proteins which interact with biliary lipids and lead to the lithogenic state. In this project, a novel recombinant approach will be used to identify the structural domains of MUC5B and MUC3 which bind biliary lipids.
The specific aims of this proposal are to: (l) characterize the major human gallbladder mucins MUC5B and MUC3 by determining the nucleotide and deduced amino acid sequences of the poorly glycosylated amino- and carboxyl-terminal regions, (2) determine the genomic organization of these mucins and (3) to identify functional domains in MUC5B and MUC3. Information obtained in specific aims 1 and 2 will be used to design constructs containing individual mucin domains. Recombinant mucin polypeptides will be expressed in bacteria and examined in lipid binding, cholesterol crystal nucleation and vesicle fusion assays. The results of these studies will provide new information about the relationship between the structure of the major human gallbladder mucins and their function in normal and pathologic gallbladder. This information is necessary for the rational design of therapies for the prevention and treatment of gallstone disease.

Agency
National Institute of Health (NIH)
Institute
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Type
Research Project (R01)
Project #
5R01DK044619-07
Application #
6177198
Study Section
Physiological Chemistry Study Section (PC)
Program Officer
Serrano, Jose
Project Start
1992-02-01
Project End
2003-03-31
Budget Start
2000-04-01
Budget End
2003-03-31
Support Year
7
Fiscal Year
2000
Total Cost
$211,743
Indirect Cost
Name
Boston University
Department
Internal Medicine/Medicine
Type
Schools of Medicine
DUNS #
604483045
City
Boston
State
MA
Country
United States
Zip Code
02118
Piludu, Marco; Rayment, Sean A; Liu, Bing et al. (2003) Electron microscopic immunogold localization of salivary mucins MG1 and MG2 in human submandibular and sublingual glands. J Histochem Cytochem 51:69-79
Becerra, Laura; Soares, Rodrigo V; Bruno, Lucila S et al. (2003) Patterns of secretion of mucins and non-mucin glycoproteins in human submandibular/sublingual secretion. Arch Oral Biol 48:147-54
Liu, Bing; Rayment, Sean A; Soares, Rodrigo V et al. (2002) Interaction of human salivary mucin MG2, its recombinant N-terminal region and a synthetic peptide with Actinobacillus actinomycetemcomitans. J Periodontal Res 37:416-24
Liu, Bing; Lague, Jessica R; Nunes, David P et al. (2002) Expression of membrane-associated mucins MUC1 and MUC4 in major human salivary glands. J Histochem Cytochem 50:811-20
Soares, Rodrigo V; Liu, Bing; Oppenheim, Frank G et al. (2002) Structural characterisation of cysteines in a bacterial-binding motif of human salivary mucin MG2. Arch Oral Biol 47:591-7
Rayment, S A; Liu, B; Soares, R V et al. (2001) The effects of duration and intensity of stimulation on total protein and mucin concentrations in resting and stimulated whole saliva. J Dent Res 80:1584-7
Iontcheva, I; Oppenheim, F G; Offner, G D et al. (2000) Molecular mapping of statherin- and histatin-binding domains in human salivary mucin MG1 (MUC5B) by the yeast two-hybrid system. J Dent Res 79:732-9
Rayment, S A; Liu, B; Offner, G D et al. (2000) Immunoquantification of human salivary mucins MG1 and MG2 in stimulated whole saliva: factors influencing mucin levels. J Dent Res 79:1765-72
Offner, G D; Troxler, R F (2000) Heterogeneity of high-molecular-weight human salivary mucins. Adv Dent Res 14:69-75
Rayment, S A; Liu, B; Offner, G D et al. (2000) Salivary mucin: a factor in the lower prevalence of gastroesophageal reflux disease in African-Americans? Am J Gastroenterol 95:3064-70

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