Showing papers by "F. Van Leuven published in 1989"

Distribution of the beta 1 subgroup of the integrins in human cells and tissues.

Abstract: We studied the distribution of the beta 1 integrin subfamily in human tissues and cells by light microscopy, electron microscopy, and immunoblotting, using monoclonal antibody DH12, previously shown to react with the beta 1 subunit of the human fibronectin receptor. Crossreaction with the other beta subunits of the integrin family, which have 45% and 47% primary amino acid sequence identity with the beta 1 subunit, was excluded, as MAb DH12 did not react with the beta 2 subunit in granulocytes and the beta 3 subunit in thrombocytes. Reactivity with the anti-beta 1 antibody was found in skin, lung, heart, striated and smooth muscle, blood cells, liver, kidney, intestine, spleen and placenta. Thus, cells of mesodermal, ectodermal, and entodermal origin express the beta 1 subunit. In skin fibroblasts cultured in vitro, beta 1 subunit was also detected intracellularly. The wide distribution of the beta 1 family, originally detected in activated T-lymphocytes after prolonged culture in vitro, contrast with the...

Fibronectin-Mediated Cellular (Inter)Actions

Abstract: Fibronectins are large glycoproteins (440 kDa), present in many tissues and in most body fluids. The soluble form, usually referred to as “plasma fibronectin”, is present in rather high concentrations (300 μg/ml) in blood (Mosesson and Umfleet, 1970). The insoluble, multimeric form, called “cellular fibronectin”, is found in connective tissue and basement membranes and is organized in short fibrils, in amorphous granules, or in thick cross-striated fibrils consisting of collagen I and II decorated with fibronectin (Fyrand, 1979; Couchman et al., 1979; Fleishmajer and Timpl, 1984). Fibronectin containing matrices are particularly prominent in vivo at sites of tissue remodelling and cell migration (e.g., wound repair, neural crest cell migration). In vitro, fibronectin localizes in extracellular fibrillar structures and in the basement membranes of most cultured cells (Yamada, 1978; Hedman et al., 1978). In these structures, fibronectin rather than collagen is the major structural component (Chen et al., 1978). Extensive accumulation of collagen fibrils appears to be a subsequent event and the distribution seems to depend on the integrity of the fibronectin matrix as shown by inhibition studies with anti-fibronectin antibodies (Mc Donald et al., 1982).