A new cell surface, detergent-insoluble glycoprotein matrix of human and hamster fibroblasts. The role of disulfide bonds in stabilization of the matrix

Differences in domain structure between pericellular matrix and plasma fibronectins as revealed by domain-specific antibodies combined with limited proteolysis and S-cyanylation: a preliminary note

Differences in domain structure between human fibronectins obtained from pericellular matrix and plasma have been revealed by limited proteolysis and S-cyanylation, followed by identification of each domain with domain-specific antibodies. Although the overall domain structure is similar between pericellular and plasma fibronectins, the fragments derived from the COOH-terminal region of these fibronectins, which were defined by specific antibodies, exhibited clear differences in their molecular weights and protease susceptibility, suggesting that the structure near the COOH-terminal region is significantly different between these two proteins.

Characterization of a detergent-resistant surface lamina in cultured human fibroblasts

Treatment of cultured human fibroblasts with 0.5% Triton X-100 produces substratum-anchored cytoskeletal preparations consisting of cytoplasmic filaments, nucleus and a plasma membrane-derived surface lamina. The lamina was visualized in fluorescence microscopy with fluorochrome-coupled wheat germ agglutinin (WGA) as a lace-like structure, extending throughout the cell domain. It displayed a different organization at the ventral and dorsal surfaces of the cell, partially coaligning with bundles of actin and myosin filaments at the dorsal cell surface. At the ventral surface vinculin patches appeared to be included in the surface lamina. Polyacrylamide gel electrophoresis, combined with lectin reactivity studies and lectin affinity chromatography, revealed a 140 kD sialoglycoprotein as the major glycoprotein component of the surface lamina.

140 000 Dalton surface glycoprotein. A plasma membrane component of the detergent-resistant cytoskeletal preparations of cultured human fibroblasts

A 140 000 D glycoprotein (140 kD gp), labelled radioactively with surface-specific techniques, remained as the major cell surface glycoprotein in the detergent-resistant cytoskeletal preparations of cultured human fibroblasts. The 140 kD gp was present also in trypsinized cells and was not affected by treatment of the cells either with collagenase, chymotrypsin or thrombin. In density gradient fractionation of whole cells the 140 kD gp was recovered in the plasma membrane fraction together with small amounts of cytoskeletal components. In fractionation of cytoskeletal preparations, on the other hand, the 140 kD gp could not be dissociated from cytoskeletal proteins and together with vimentin it formed the major component of the oligomeric polypeptide complex generated by treating the surface-labelled cytoskeletal preparations with bifunctional cross-linking reagent, dithiobis succinimidyl propionate (DTPS). Moreover, the 140 kD gp seemed to copurify with vimentin upon reconstitution of intermediate filaments from urea-solubilized cytoskeletal preparations. On the other hand, low ionic-induced degradation of vimentin led to a decrease in the amount of the detergent-resistant 140 kD gp on the cell surface. In electron microscopy, a close apposition between bilayer-like plasma membrane remnants of the adherent cytoskeletons and cytoskeletal elements could be seen. The results indicate that the 140 kD gp is a plasma membrane glycoprotein which closely interacts with the detergent-resistant cytoskeleton of cultured human fibroblast. Possible mechanisms of the association are discussed.