Rabbit Anti-Human CRK Polyclonal antibody

Raf-1 is a serine/threonine protein kinase that has an essential role in cell proliferation. The mechanisms that regulate Raf-1 in airway smooth muscle are not well understood. In this study, treatment with platelet-derived growth factor(PDGF) induced spatial redistribution of Raf-1 from the cytoplasm to the periphery of human airway smooth muscle cells. Moreover, a pool of Raf-1 was found in F-actin of human airway smooth muscle cells. Activation with PDGF led to an increase in the association of Raf-1 with cytoskeletal actin. Treatment of cells with the actin polymerization inhibitor latrunculin A (LAT-A), but not the microtubule depolymerizer nocodazole, inhibited the interaction of Raf-1 with actin in response to PDGF activation. Because abelson tyrosine kinase (Abl) is known to specifically regulate actin dynamics in smooth muscle, the role of Abl in modulating the coupling of Raf-1 with actin was also evaluated. Abl knockdown by RNA interference attenuated the association of Raf-1 with actin, which is recovered by Abl rescue. Treatment with LAT-A, but not nocodazole, inhibited the spatial redistribution of Raf-1 during PDGF activation. However, treatment with both LAT-A and nocodazole attenuated smooth muscle cell proliferation. Finally, Abl knockdown attenuated the redistribution of Raf-1 and cell proliferation, which were restored by Abl reexpression. The results suggest a novel mechanism that the interaction of Raf-1 with cytoskeletal actin is critical for Raf-1 redistribution and airway smooth muscle cell proliferation during activation with the growth factor.

P130Cas is a docking protein essentially coordinating tyrosine-kinase-based signaling pathways associated with cell adhesion and migration etc. Its central substrate domain (CasSD) can bind to Crk and includes 15 YxxP motifs, where most tyrosine phosphorylation happens. It has been shown that CasSD can be stretched to promote phosphorylation, the mechanism of which needs to be explored in detail. Thus, it is important to uncover the native structure(s) of CasSD and the structural changes associated with mechanical stretching, both of which are still unclear. Here, we used atomic force microscopy force mode and magnetic tweezers to stretch individual molecules of CasSD constructs. Our results showed that the CasSD domain was intrinsically disordered. Natively, CasSD domains took many conformations beside random coils, while most of these conformations possessed limited mechanical stability. In magnetic tweezers experiments, the intramolecular interactions stabilizing the varied native conformations of CasSD were found similar in strength. Such diversity in native conformations of CasSD domains, as discovered here, should play important role in their signaling functions and their limited strength should be relevant to the mechanical activation of those signaling pathways. (C) 2013 Elsevier B.V. All rights reserved.