Figure 2.

Integrin ligation with cell-binding fibronectin fragments does not attenuate platelet-derived growth factor (PDGF)-induced intracellular calcium release. Fibronectin-null mouse embryonic fibroblasts (FN-null MEFs) were seeded on collagen-coated wells (1.1 × 10⁵ cells/cm²). Four hours after seeding, cells were treated with fibronectin (FN; 25 nM) or an equal volume of phosphate-buffered saline (PBS); the indicated fibronectin fusion protein (250 nM); or the indicated concentrations of tag-less FNIII10. After 20 h, cells were loaded with Fluo-4, stimulated with 30 ng/mL PDGF and monitored for changes in fluorescence intensity. (A) Each trace represents fluorescence intensity versus time for a population of cells in an individual well. Data are representative of 1 of 4 independent experiments performed in quadruplicate. (B–D) Data are presented as relative change in fluorescence intensity from baseline (ΔF/F₀) and are expressed as mean ± the standard error of the mean (SEM) of 4 (B) or 7 (C,D) experiments performed in quadruplicate. Values were normalized to “+PBS” or “+glutathione S-transferase (GST)”, which were set to 1. (B) * Significantly different versus respective control by analysis of variance (ANOVA) (p < 0.05). (C,D) * Significantly different versus +GST by ANOVA (p < 0.05).