Vimentin intermediate filaments (VIFs), expressed in most mesenchymal and cancer cells, undergo dramatic reorganization during cell migration; however, the mechanism remains obscure. This study demonstrates that upon growth-factor stimulation, Src directly phosphorylates vimentin at Tyr117, leading to VIF disassembly into squiggles and particles at the cell edge during lamellipodia formation. The protein tyrosine phosphatase SHP2 counteracted the Src effects on VIF tyrosine phosphorylation and organization. VIFs formed by vimentin Y117D mutant were more soluble and dynamic than those formed by the wild-type and Y117F mutant. Increased expression of vimentin promoted growth-factor induced lamellipodia formation and cell migration, whereas the mutants suppressed both. The vimentin-induced increase in lamellipodia formation correlated with the activation of Rac and Vav2, with the latter associated with VIFs and recruited to the plasma membrane upon growth-factor stimulation. These results reveal a novel mechanism for regulating VIF dynamics through Src and SHP2 and demonstrate that proper VIF dynamics are important for Rac activation and cell migration.

SummaryPodosomes are actin-based membrane protrusions that facilitate extracellular matrix degradation and motility of invasive cells. Podosomes can self-organize into large rosette-like structures in Src-transformed fibroblasts, osteoclasts and some highly invasive cancer cells. However, the mechanism of this assembly remains obscure. In this study, we show that the suppression of Jun N-terminal kinase (JNK) by the JNK inhibitor SP600125 or short-hairpin RNA inhibited podosome rosette formation in SrcY527F-transformed NIH3T3 fibroblasts. In addition, SrcY527F was less able to induce podosome rosettes in JNK1-null or JNK2-null mouse embryo fibroblasts than in wild-type counterparts. The kinase activity of JNK was essential for promoting podosome rosette formation but not for its localization to podosome rosettes. Moesin, a member of the ERM (ezrin, radixin and moesin) protein family, was identified as a substrate of JNK. We show that the phosphorylation of moesin at Thr558 by JNK was important for podosome rosette formation in SrcY527F-transformed NIH3T3 fibroblasts. Taken together, our results unveil a novel role of JNK in podosome rosette formation through the phosphorylation of moesin.

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The purpose of this paper is to investigate the effect of ablation parameters on the ablation characteristics for the fixed diamond multi-wire sawing by using Taguchi method. Meanwhile, using the optimal ablation parameters, we accomplish the cutting dynamic analysis and controller design of the diamond multi-wire sawing system. In this paper, we apply the Chemical Mechanical Polishing (CMP) theorem to derive the ingot profile and cutting rate equations of the diamond multi-wire sawing system. The characteristics discussed in this paper include ingot profile variance, cutting rate. The ablation parameters are tension force, wire velocity, cutting force, width of the kerf. The orthogonal array, signal-to-noise (S/N) ratio and analysis of variance (ANOVA) are employed to analyze the effect of these ablation parameters. In the meantime, we use the optimal ablation parameters to accomplish the controller design of the diamond multi-wire sawing system, include diamond high-speed control of the main roller in the cutting system, cutting rate control and the moving wire bow angle holding.