epidermal-growth-factor and glycyl-arginyl-glycyl-aspartyl-serine

A novel protein was engineered by inserting the GRGDS motif of fibronectin within the 14-residue loop of the EGF-like module from human complement protease C1r. The resulting chimeric EGF-RGD module (52 residues, three disulfide bridges) was assembled by automated solid-phase synthesis using the t-Boc strategy. Using reduced/oxidized glutathione, the EGF-RGD module was folded as efficiently as the natural C1r-EGF module, resulting in formation of the appropriate disulfide bridge pattern as shown by mass spectrometry and N-terminal sequence analyses of thermolytic fragments. Circular dichroism and NMR measurements provided further indication that introduction of the GRGDS motif had no significant effect on the folding. Using Chinese Hamster Ovary (CHO) cells bearing the integrin receptors specific for fibronectin and vitronectin, EGF-RGD was shown to induce cell adhesion via the introduced GRGDS motif. Cell binding was inhibited specifically and efficiently by the synthetic peptide GRGDSP and by fibronectin, and to a much lesser extent by vitronectin, whereas the monoclonal antibody PB1 directed to the alpha5 subunit of alpha5beta1 integrin had no effect. The ability of EGF-RGD to trigger significant cell spreading and intracellular signaling was also demonstrated using immunofluorescence and confocal microscopy.

Topics: Amino Acid Sequence; Animals; Binding, Competitive; Cell Adhesion; CHO Cells; Circular Dichroism; Complement C1r; Cricetinae; Epidermal Growth Factor; Fibronectins; Fluorescent Antibody Technique; Mass Spectrometry; Models, Molecular; Molecular Sequence Data; Oligopeptides; Recombinant Fusion Proteins; Sequence Analysis

Some human neoplasms show aberrant expression or overexpression of epidermal growth factor (EGF) receptor, and the degree of the receptor expression is correlated with the malignant phenotype in certain epithelial tumors including squamous carcinoma cells. Since phenotypic transformation of cells could involve quantitative and qualitative alteration of integrin function, the effects of EGF on cell-matrix interactions were studied using HSC-1 cells, a human squamous carcinoma cell line showing EGF receptor overexpression. The EGF-treated HSC-1 cells interacted with matrix proteins differently from the untreated cells, as shown by cell adhesion and phagokinetic track assays. Among fibronectin, laminin, fibrinogen, and type I collagen, fibronectin was the most efficient substratum to promote untreated HSC-1 cell adhesion and migration. Pretreatment of the cells with 50 ng/ml EGF for 18 h selectively increased the number of spread cells and the size of the individual cell migration area on type I collagen by 250 and 400%, respectively. The same pretreatment diminished cell adhesion and migration on other substrata so that the EGF treatment converted type I collagen as the most efficient substratum for cell adhesion and migration of the HSC-1 cells. ELISA and immunoprecipitation studies showed that EGF up-regulated the expression of alpha 2 beta 1 integrin collagen receptor in a time- and dose-dependent manner by stimulating biosynthesis of alpha 2 subunit, but did not up-regulate those of the alpha 3 beta 1, alpha 5 beta 1, or alpha v beta 3 integrins. These results suggest that EGF preferentially enhances HSC-1 cell interaction with type I collagen, leading to the enhanced cellular migratory activity on the substratum, as a result of selective up-regulation of alpha 2 beta 1 integrin expression.

Topics: Antigens, CD; Antineoplastic Agents; Carcinoma, Squamous Cell; Cell Adhesion; Cell Movement; Collagen; Epidermal Growth Factor; ErbB Receptors; Extracellular Matrix Proteins; Gene Amplification; Gene Expression Regulation, Neoplastic; Humans; Integrin beta1; Integrins; Oligopeptides; Skin Neoplasms; Tumor Cells, Cultured; Up-Regulation