Functional consequences of the macrophage stimulating protein 689C inflammatory bowel disease risk allele.
Kauder SE1, Santell L2, Mai E3, Wright LY4, Luis E5, N'Diaye EN1, Lutman J6, Ratti N7, Sa SM7, Maun HR2, Stefanich E6, Gonzalez LC5, Graham RR8, Diehl L7, Faubion WA Jr9, Keir ME4, Young J3, Chaudhuri A10, Lazarus RA2, Egen JG1.
Macrophage stimulating protein (MSP) is a serum growth factor that binds to and activates the receptor tyrosine kinase, Recepteur d'Origine Nantais (RON). A non-synonymous coding variant in MSP (689C) has been associated with genetic susceptibility to both Crohn's disease and ulcerative colitis, two major types of inflammatory bowel disease (IBD) characterized by chronic inflammation of the digestive tract. We investigated the consequences of this polymorphism for MSP-RON pathway activity and IBD pathogenesis.
RON expression patterns were examined on mouse and human cells and tissues under normal and disease conditions to identify cell types regulated by MSP-RON. Recombinant MSP variants were tested for their ability to bind and stimulate RON and undergo proteolytic activation. MSP concentrations were quantified in the serum of individuals carrying the MSP 689R and 689C alleles.
In intestinal tissue, RON was primarily expressed by epithelial cells under normal and disease conditions. The 689C polymorphism had no impact on the ability of MSP to bind to or signal through RON. In a cohort of normal individuals and IBD patients, carriers of the 689C polymorphism had lower concentrations of MSP in their serum.
By reducing the quantities of circulating MSP, the 689C polymorphism, or a variant in linkage disequilibrium with this polymorphism, may impact RON ligand availability and thus receptor activity. Given the known functions of RON in regulating wound healing and our analysis of RON expression patterns in human intestinal tissue, these data suggest that decreased RON activity may impact the efficiency of epithelial repair and thus underlie the increased IBD susceptibility associated with the MSP 689C allele.
PMID: 24409221 [PubMed - indexed for MEDLINE] PMCID: PMC3884107
:: Courtesy NCBI (National Center for Biotechnology Information) Database and The NIH (National Institutes of Health) ::
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