Filopodia Formation (filopodia + formation)

Distribution by Scientific Domains


Selected Abstracts


Fascin1 is dispensable for mouse development but is favorable for neonatal survival

CYTOSKELETON, Issue 8 2009
Yoshihiko Yamakita
Abstract Fascin1, an actin-bundling protein, has been demonstrated to be critical for filopodia formation in cultured cells, and thus is believed to be vital in motile activities including neurite extension and cell migration. To test whether fascin1 plays such essential roles within a whole animal, we have generated and characterized fascin1-deficient mice. Unexpectedly, fascin1-deficient mice are viable and fertile with no major developmental defect. Nissl staining of serial coronal brain sections reveals that fascin1-deficient brain is grossly normal except that knockout mouse brain lacks the posterior region of the anterior commissure neuron and has larger lateral ventricle. Fascin1-deficient, dorsal root ganglion neurons are able to extend neurites in vitro as well as those from wild-type mice, although fascin1-deficient growth cones are smaller and exhibit fewer and shorter filopodia than wild-type counterparts. Likewise, fascin1-deficient, embryonic fibroblasts are able to assemble filopodia, though filopodia are fewer, shorter and short-lived. These results indicate that fascin1-mediated filopodia assembly is dispensable for mouse development. Cell Motil. Cytoskeleton 2009. © 2009 Wiley-Liss, Inc. [source]


Src and FAK mediate cell,matrix adhesion-dependent activation of met during transformation of breast epithelial cells

JOURNAL OF CELLULAR BIOCHEMISTRY, Issue 6 2009
Angela Y. Hui
Abstract Cell,matrix adhesion has been shown to promote activation of the hepatocyte growth factor receptor, Met, in a ligand-independent manner. This process has been linked to transformation and tumorigenesis in a variety of cancer types. In the present report, we describe a key role of integrin signaling via the Src/FAK axis in the activation of Met in breast epithelial and carcinoma cells. Expression of an activated Src mutant in non-neoplastic breast epithelial cells or in carcinoma cells was found to increase phosphorylation of Met at regulatory tyrosines in the auto-activation loop domain, correlating with increased cell spreading and filopodia extensions. Furthermore, phosphorylated Met is complexed with ,1 integrins and is co-localized with vinculin and FAK at focal adhesions in epithelial cells expressing activated Src. Conversely, genetic or pharmacological inhibition of Src abrogates constitutive Met phosphorylation in carcinoma cells or epithelial cells expressing activated Src, and inhibits filopodia formation. Interestingly, Src-dependent phosphorylation of Met requires cell,matrix adhesion, as well as actin stress fiber assembly. Phosphorylation of FAK by Src is also required for Src-induced Met phosphorylation, emphasizing the importance of the Src/FAK signaling pathway. However, stimulation of Met phosphorylation by addition of exogenous HGF in epithelial cells is refractory to inhibition of Src family kinases, indicating that HGF-dependent and Src/integrin-dependent Met activation occur via distinct mechanisms. Together these findings demonstrate a novel mechanism by which the Src/FAK axis links signals from the integrin adhesion complex to promote Met activation in breast epithelial cells. J. Cell. Biochem. 107: 1168,1181, 2009. © 2009 Wiley-Liss, Inc. [source]


The enteropathogenic Escherichia coli type III secretion system effector Map binds EBP50/NHERF1: implication for cell signalling and diarrhoea

MOLECULAR MICROBIOLOGY, Issue 2 2006
Nandi Simpson
Summary Enteropathogenic Escherichia coli (EPEC) is the single most important contributor to child diarrhoea in developing countries. Nevertheless, the mechanism responsible for EPEC diarrhoea remains elusive. Using the yeast two-hybrid system to determine the target host cell protein of the EPEC type III secretion system effector Map led to identification of ezrin/radixin/moesin (ERM)-binding phosphoprotein 50 (EBP50), also known as Na+/H+ exchanger regulatory factor 1 (NHERF1). Protein interaction is mediated by the carboxy-terminal Thr-Arg-Leu (TRL) motif of Map and the PSD-95/Disk-large/ZO-1 domain 1 (PDZ1) of EBP50/NHERF1. Although EBP50/NHERF1 is recruited to site of EPEC adhesion in a Map-independent mechanism, co-immunoprecipitation and immunostaining revealed that Map binds to, induces proteolysis of, and colocalizes with EBP50/NHERF1 during infection of cultured epithelial cells. The TRL motif of Map was involved in Map-induced filopodia formation and brush border elongation on infected HeLa and Caco-2 cells respectively. As EBP50/NHERF1 regulates ion channels in the intestine we assessed the involvement of Map in diarrhoea using the Citrobacter rodentium mouse model of EPEC. We report significantly greater diarrhoea following infections with wild-type C. rodentium compared with C. rodentium,map. These results provide new insights into the mechanisms of EPEC diarrhoea. [source]


The mechanisms used by enteropathogenic Escherichia coli to control filopodia dynamics

CELLULAR MICROBIOLOGY, Issue 2 2009
Cedric N. Berger
Summary Enteropathogenic Escherichia coli (EPEC) subverts actin dynamics in eukaryotic cells by injecting effector proteins via a type III secretion system. First, WxxxE effector Map triggers transient formation of filopodia. Then, following recovery from the filopodial signals, EPEC triggers robust actin polymerization via a signalling complex comprising Tir and the adaptor proteins Nck. In this paper we show that Map triggers filopodia formation by activating Cdc42; expression of dominant-negative Cdc42 or knock-down of Cdc42 by siRNA impaired filopodia formation. In addition, Map binds PDZ1 of NHERF1. We show that Map,NHERF1 interaction is needed for filopodia stabilization in a process involving ezrin and the RhoA/ROCK cascade; expression of dominant-negative ezrin and RhoA or siRNA knock-down of RhoA lead to rapid elimination of filopodia. Moreover, we show that formation of the Tir-Nck signalling complex leads to filopodia withdrawal. Recovery from the filopodial signals requires phosphorylation of a Tir tyrosine (Y474) residue and actin polymerization pathway as both infection of cells with EPEC expressing TirY474S or infection of Nck knockout cells with wild-type EPEC resulted in persistence of filopodia. These results show that EPEC effectors modulate actin dynamics by temporal subverting the Rho GTPases and other actin polymerization pathways for the benefit of the adherent pathogen. [source]