Glycoprotein 115, a glycoprotein isolated from chick blood vessels, is widely distributed in connective tissue.

Abstract

An extracellular glycoprotein (gp 115) with an apparent Mr = 115,000 isolated from chick aortas (Bressan, G. M., i. Castellani, A. Colombatti, and D. Volpin, 1983, J. Biol. Chem., 258:13262-13267), was used to immunize mice. The antisera were shown to specifically recognize gp 115 by numerous criteria: a major band around Mr = 115,000 plus minor bands of lower Mr were visible by immunoblotting on aorta extracts, and a similar pattern was observed with a monoclonal antibody; no cross-reactivity was detected by radioimmunobinding with other extracellular proteins, namely, fibronectin, laminin, and collagen types I, III, IV, V, and Vl. Antigen distribution on frozen tissue sections from newborn chicks was investigated by using affinity-purified antibody. Strong immunoreactivity was always found in blood vessels. In the digestive tract, the fluorescent staining was localized both at the level of muscular layers and in the stromal matrix of the villi. Within skeletal muscle and myocardium, staining was associated with large connective tissue bundles and the matrix around each muscle fiber. Intense fluorescence was observed in the kidney, in smooth muscle cells rich areas of parabronchi, and within the portal space and along liver sinusoids. The antigen was not detected at the epidermal-dermal junction; immunoreactivity in the dermis was present as a diffuse fibrillar pattern. That the antigen detected by immunofluorescence in the various organs was indeed gp 115 was demonstrated by immunoblotting analysis: as in aorta extracts, a major band around Mr --115,000 was detected in several tissues. Antibody-reacting material was also incorporated into the extracellular matrix produced by embryo smooth muscle cells grown in vitro and was organized as a meshwork of fine fibrils.There is increasing evidence suggesting that the extracellular matrix plays an important role in establishing and organizing tissue structure (I, 2). This is likely to be the result of multiple interactions between cells and a specific set of extracellular components in the different anatomical districts. The knowledge of tissue distribution of each novel molecular species is the first step toward the understanding of its possible function. Thus, a characteristic pattern of distribution has been detected in the various organs for several components of the connective tissue such as the different collagen types (3, 4), fibronectin (5, 6), laminin (7), entactin (8), vitronectin (9), and proteoglycans (10, 11). In addition, the composition of the matrix is closely dependent on the cell type and the degree of its differentiation (2).While studying the proteins of chick blood vessels, we have identified a noncollagenous glycoprotein of about Mr = l 15,000 (gp 115), which was unrelated by biochemical and immunological criteria to the major known extracellular glycoproteins, fibronectin and laminin (12).The investigation of the distribution of gp 115 in tissues t?om newborn chicks by using immunofluorescence histochemistry is reported here. We have ...

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