Figure 1. PECAM1 is critical for flow- but not HGF-induced Gab1 activation.

A, The specific role of PECAM1 in flow-induced Gab1 tyrosine (Y627) phosphorylation. HUVECs were transfected with non-target control siRNA (siNC, 50 nM) or human PECAM1 siRNA (siPECAM1, 50 nM) for 48 h, and then exposed to laminar flow (12 dynes/cm²), HGF (10 ng/mL), or VEGF (25 ng/mL) for 15 min. Cell lysates were prepared and probed with the indicated antibodies by Western blot analysis. B, Densitometry quantification of panel A *P<0.05, **P<0.01 versus control (ctrl); ##P<0.01 versus siNC+flow; ### p<0.01 versus respective control. C, The specific role of PECAM1 in flow-induced Gab1 membrane translocation. HUVECs were transfected with siNC or siPECAM1 as described in A, then infected with recombinant adenovirus constructs encoding the GFP-tagged human Gab1 at the multiplicity of infection (MOI, 30) for 24 h, and then exposed to laminar flow (12 dynes/cm²) or HGF (10 ng/mL) for 15 min. Cells were fixed with 3.7% formaldehyde in PBS and GFP fluorescence was captured using a 60x oil immersion objective lens.