Association of glycoconjugates with the cytoskeletal framework

The association of glycoconjugates with the cytoskeletal framework was examined in detergent-extracted cells. Sparse cultures of fibroblasts that assemble only minimal amounts of extracellular matrix were extracted under mild conditions with Triton X-100 which remove most of the lipids and soluble cellular proteins. The detergent-resistant framework retains lectin binding sites in the nucleus, in the perinuclear area occupied by the rough endoplasmic reticulum-Golgi system of the intact cell, and in a network throughout the cytoskeletal framework. Fluorescent-antibody staining with antibody against collagen type I and fibronectin reveals extensive perinuclear staining of the remnant rough endoplasmic reticulum-Golgi system. In contrast, only sporadic staining of the pericellular area is obtained with these antibodies, in sparse cultures of whole cells. Lectin binding sites were detected in the nucleus and are attributed to chromatin-associated glycoconjugates. They can be removed by DNase under conditions that preserve the cytoplasmic lectin binding sites and the nuclear matrix. The results suggest a high degree of integration of the membrane residues of the cytoplasmic elements and the nuclear matrix with the skeletal framework and indicate a possible role for the glycoconjugates in this structural integration.