Mitotic down-regulation of p190RhoGAP is required for the successful completion of cytokinesis.

p190RhoGAP-A (p190) is a GTPase-activating protein known to regulate actin cytoskeleton dynamics by decreasing RhoGTP levels through activation of Rho intrinsic GTPase activity. We have previously shown that p190 protein levels are cell cycle-regulated, decreasing in mitosis, and that this decrease is mediated by the ubiquitin-proteasome pathway. In addition, overexpression of p190 results in decreased RhoGTP levels at the cleavage furrow during cytokinesis, p190 and the RhoGEF Ect2 play opposing roles in cytokinesis, and sustained levels of p190 in mitosis are associated with cytokinesis failure, all findings that suggest but do not directly demonstrate that completion of cytokinesis is dependent on reduced levels of p190.

p190RhoGAP negatively regulates Rho activity at the cleavage furrow of mitotic cells.

Previous studies demonstrated that p190RhoGAP (p190) negatively affects cytokinesis in a RhoGAP-dependent manner, suggesting that regulation of Rho may be a critical mechanism of p190 action during cytokinesis. P190 localizes to the cleavage furrow (CF) of dividing cells, and its levels decrease during late mitosis by an ubiquitin-mediated mechanism, consistent with the hypothesis that high RhoGTP levels are required for completion of cytokinesis. To determine whether RhoGTP levels in the CF are affected by p190 and to define the phase(s) of cytokinesis in which p190 is involved, we used FRET analysis alone or in combination with time-lapse microscopy.

Opposing roles of p190RhoGAP and Ect2 RhoGEF in regulating cytokinesis.

Evidence suggests that p190RhoGAP (p190), a GTPase activating protein (GAP) specific for Rho, plays a role in cytokinesis. First, ectopic expression of p190 induces a multinucleated cellular phenotype. Second, endogenous p190 localizes to the cleavage furrow of dividing cells.

Novel peptide ligands for integrin alpha 4 beta 1 overexpressed in cancer cells.

Using the "one-bead one-peptide" combinatorial technology, a library of random cyclic octapeptides and nonapeptides, consisting of natural and unnatural amino acids, was synthesized on polystyrene beads. This library was used to screen for peptides that promoted attachment and proliferation of bronchioloalveolar carcinoma cells (H1650), employing a "cell growth on bead" assay. Consensus peptide sequences of cNleDXXXXc and cXNleDXXXXc (where Nle is norleucine) were identified.