Tensional force on PECAM-1 elicits global focal adhesion growth that is dependent on cellular contractility. (a–c) ECs were incubated with magnetic beads coated with an antibody specific to CD44 or PECAM-1 and subjected to force for 0 min (no force [NF]) or 30 min (force [F]) with a permanent magnet. (a) Representative fluorescent micrographs of cells showing focal adhesions (vinculin; green) with bound beads (red, marked by white circles). Scale bars = 20 μm. (b and c) Quantification of mean frequency of focal adhesions per cell (b) and mean focal adhesion area (c) following NF or F (n > 30 cells across three separate experiments). (d–g) ECs were treated with vehicle or ROCK inhibitor Y-27632, and then mechanical force was applied for 0 min (NF) or 30 min (F). Quantification of global activation of ERK (d), colocalization of pERK1/2^T202/Y204 to vinculin (e) quantified using Pearson’s coefficient, mean area of vinculin-positive focal adhesions (f), and mean frequency of focal adhesions per cell (g; n > 30 cells across three separate experiments). Values in b–g are mean ± SEM, and significance was determined in b and c by two-sided t test and in d–g by two-way ANOVA. **, P < 0.01; ***, P < 0.001; ****, P < 0.0001. FA, focal adhesion.