Associated with the Gleevec phenotype was an increase in RhoA activity

increased global cell adhesion strength, a pronounced change in adhesion patterns and an increase in total traction applied to the substrate. Abl family kinases have been reported to be located at cell adhesions. They are correctly positioned to regulate the reorganization of the cytoskeleton at sites of membrane protrusion and at focal adhesions where integrins are engaged. In 10T1/2 fibroblasts, during the initial minutes of fibronectin stimulation, when c-Abl activity is the highest, the nuclear pool of c-Abl re-localizes transiently to focal adhesions. This transient re-localization also occurs in NIH3T3 cells, where a fraction of the cellular Abl associates with the focal adhesion proteins, paxillin and Grb2. Abl family kinases have also been reported to reduce initial cell attachment to the substrate. On fibronectin, fibroblasts derived from Abl-null mouse embryos spread faster than their wild-type counterparts, while restoration of Abl expression in the Abl-null fibroblasts 485-49-4 reduced the rate of spreading. Kain and Klemke provided evidence that Abl family kinases negatively regulate cell migration by uncoupling CAS-Crk complexes. Li and Pendergast recently reported that Arg could disrupt CrkII-C3G complex formation to reduce b1-integrin related adhesion formation. These reports indicate that Abl family kinases negatively regulate cell adhesion, thus supporting our observations that Abl family kinase inhibition results in a more adhesive and motile phenotype. Concomitant with the adhesion increase induced by Gleevec treatment, there is an increase RhoA activity. Since Bradley and Koleske reported that Abl family kinases could function through the activation of p190RhoGAP to reduce RhoA activity, it is possible that the Gleevec action occurs by inhibition of the Abl-mediated activation of this RhoGAP. In any event, the increase in RhoA activity 677746-25-7 distributor correlates with the increase in total traction force applied to the substrate; the spatial disposition of active myosin II indicates contractile activity parallel to the long axis of the cell and enhanced traction in the wings of the treated cell. Often, an abundance of retraction fibers at the trailing edge of a cell is taken as evidence for strong adhesion in this region. However, at the rear of Gleevec-treated cells, in spite of greater global adhesion strength, there are fewer retraction fibers than in control cells. What might be the reason for this observation? A potential explanation is found in the fact that the trailing edge tractions of Gleevec-treated cells were significantly stronger than in control cells. These tractions may effectively break all adhesions in the rear of the cell, even those in that normally result in retraction fiber formation.