Early events during substrate adhesion of normal and virus-transformed mouse fibroblasts

The relationship between attachment of Balb/c3T3 cells and their SV40 transformants to glass or plastic substrates and deposition of substrate-attached material (SAM-proteoglycans implicated in substrate adhesion) has been examined very early after inoculation of cells subcultured with ethylenebis (oxyethylenenitrilo) tetra-acetic acid (EGTA). The metabolic inhibitors cycloheximide and colchicine minimally affected the kinetics or short-term stability of attachment of cells or deposition of SAM. SAM deposition on to the substrate began immediately after inoculation of cells and was maximal prior to the highest cell attachment level (30-40 min after inoculation). At 4 degrees C, there was no attachment of cells to the substrate and no deposition of leucine- or glucosamine-radiolabelled SAM on to the substrate. 3T3 cells deposited SAM to a maximal level earlier during the attachment process than SV40-transformed cells. SVT2 cells deposited much smaller amounts of SAM (measured on a per-cell basis) to 3T3 SAM-coated substrates during attachment processes, whereas 3T3 cells and concanavalin A (con A) revertant variants of SVT2 cells, which have regained density-dependent inhibition of growth, deposited identical amounts of SAM (per-cell) on untreated or SAM-coated substrates. Serial attachment experiments with SVT2 cells indicated that all SVT2 cells reduced their deposition amounts on SAM-coated substrates, rather than there being an ability of a small proportion of cells to attach preferentially to SAM-coated substrates while being unable to deposit SAM themselves. The data are consistent with the presence of a sizeable pool of SAM-like proteoglycans being present on the surface of EGTA-removed cells whose deposition may be a requirement for, but may not necessarily be sufficient for, stable adhesion of cells to the substrate.