The proteome of mouse mucosal mast cell homologues: the role of transforming growth factor beta1.

Mast cells migrate to the mucosal epithelium during intestinal nematode infections in mice, where they express abundant mucosal mast cell-specific proteases, mouse mast cell protease-1 and -2 (MCPT1 and MCPT2). Expression of these proteases is strictly controlled by transforming growth factor-beta1 (TGF-beta1) in the epithelium. In vitro homologues of mucosal mast cells are generated by culturing bone marrow-derived mast cells (BMMC) in the presence of TGF-beta1. We examined the proteome of BMMC cultured either in the presence of TGF-beta1 (n = 5) or of a neutralising anti-TGF-beta1 antibody (n = 5). Cell extracts were examined by 2-DE, and changes in expression levels of protein spots were determined by densitometry. Spots of interest were identified by tryptic peptide mapping. In addition to the up-regulation of MCPT1 and MCPT2, which accounted for approximately 40% of all soluble protein in the TGF-beta1 treated cells, MCPT7 was modestly up-regulated by TGF-beta1, and calnexin was up-regulated fivefold. A 7.6-fold down-regulation of galectin-1 was verified by Western blotting and FACS analysis. Galectin-1 is located on the cell surface where it mediates cellular adhesion to basement membranes. Regulation of its expression by TGF-beta1 may be of relevance to mast cell adhesion within the epithelium.