Figure 2. Syndecan-4-regulated integrin trafficking is independent of Rho kinase activity. Energy required to detach fibroblasts from 50K or Fn was measured by atomic force microscopy. (A) Energy measurements of untreated and Y27632-inhibited fibroblasts reveal that Rho kinase activity affects cell avidity itself, but is not required for syndecan-4-induced integrin endocytosis. (B and C) Contacts were made sequentially with 50K, then Fn, then 50K again to follow α₅β₁-integrin endocytosis upon syndecan-4-engagement and recovery upon removal of syndecan-4 ligand. (B) Untreated fibroblasts exhibit reduction in unbinding energy upon syndecan-4 engagement, and recover high unbinding energy upon return to 50K. (C) Treatment with Y27632 blocks neither the endocytic nor recovery phases caused by contact with fibronectin. Values represent at least 80 measurements per condition from 4 experiments. Error bars represent s.e.m., significance was tested by ANOVA.