Interaction of phospholipase C-gamma1 with villin regulates epithelial cell migration

Molecular profiling of urinary extracellular vesicles in chronic kidney disease and renal fibrosis

Chronic kidney disease (CKD) is a long-term kidney damage caused by gradual loss of essential kidney functions. A global health issue, CKD affects up to 16% of the population worldwide. Symptoms are often not apparent in the early stages, and if left untreated, CKD can progress to end-stage kidney disease (ESKD), also known as kidney failure, when the only possible treatments are dialysis and kidney transplantation. The end point of nearly all forms of CKD is kidney fibrosis, a process of unsuccessful wound-healing of kidney tissue. Detection of kidney fibrosis, therefore, often means detection of CKD. Renal biopsy remains the best test for renal scarring, despite being intrinsically limited by its invasiveness and sampling bias. Urine is a desirable source of fibrosis biomarkers as it can be easily obtained in a non-invasive way and in large volumes. Besides, urine contains biomolecules filtered through the glomeruli, mirroring the pathological state. There is, however, a problem of highly abundant urinary proteins that can mask rare disease biomarkers. Urinary extracellular vesicles (uEVs), which originate from renal cells and carry proteins, nucleic acids, and lipids, are an attractive source of potential rare CKD biomarkers. Their cargo consists of low-abundant proteins but highly concentrated in a nanosize-volume, as well as molecules too large to be filtered from plasma. Combining molecular profiling data (protein and miRNAs) of uEVs, isolated from patients affected by various forms of CKD, this review considers the possible diagnostic and prognostic value of uEVs biomarkers and their potential application in the translation of new experimental antifibrotic therapeutics.

Site-specific phosphorylation of villin remodels the actin cytoskeleton to regulate Sendai viral glycoprotein-mediated membrane fusion

Connivance of cellular factors during virus-host cell membrane fusion is poorly understood. We have recently shown that cellular villin plays an important role during membrane fusion of reconstituted Sendai virosomes with hepatocytes. Here, we employed villin-null Chinese Hamster Ovary (CHO) cells, where villin expression led to an increased fusion with virosomes, which was further enhanced due to tyrosine phosphorylation in the presence of c-src. However, the villin RRI mutant, lacking actin-severing function, failed to augment membrane fusion. Furthermore, quantitative mass spectrometry and detailed analysis revealed Tyr⁴⁹⁹ to be the key phosphorylation site of villin responsible for the enhancement of virosome-CHO cell fusion. Overall, our results demonstrate a critical role for villin and its cell-type dependent phosphorylation in regulating membrane fusion.

Sendai virus recruits cellular villin to remodel actin cytoskeleton during fusion with hepatocytes

Reconstituted Sendai viral envelopes (virosomes) are well recognized for their promising potential in membrane fusion-mediated delivery of bioactive molecules to liver cells. Despite the known function of viral envelope glycoproteins in catalyzing fusion with cellular membrane, the role of host cell proteins remains elusive. Here, we used two-dimensional differential in-gel electrophoresis to analyze hepatic cells in early response to virosome-induced membrane fusion. Quantitative mass spectrometry together with biochemical analysis revealed that villin, an actin-modifying protein, is differentially up-regulated and phosphorylated at threonine 206-an early molecular event during membrane fusion. We found that villin influences actin dynamics and that this influence, in turn, promotes membrane mixing through active participation of Sendai viral envelope glycoproteins. Modulation of villin in host cells also resulted in a discernible effect on the entry and egress of progeny Sendai virus. Taken together, these results suggest a novel mechanism of regulated viral entry in animal cells mediated by host factor villin.

Development and characterization of 2-dimensional culture for buffalo intestinal cells

Small intestinal epithelial cells (IEC) play a major role in the absorption of nutrients and toxins. Due to the similarity of genome-wide single copy protein orthologues between cattle and human, establishment of ruminant's primary small IEC culture could be a valuable tool for toxicity studies. Therefore, the current study focused on the development and characterization of buffalo IEC culture, as cattle slaughter is banned in India. The buffalo jejunum fragments were washed consecutively several times in saline, warm phosphate buffered saline (PBS), PBS with 5 mM dithiothreitol, digesting solution and 2% sorbitol in PBS. The cells were cultured on 17 µg/cm² collagen coated plates and transwell plates with serum (2% Fetal bovine serum (FBS) and 10% FBS) and serum-free culture conditions. The cells were differentiated into typical epithelial cobblestone morphology from day 5 onwards in 50% successful cultures. The cultured IEC were characterized by gene expression of epithelial cell markers, cytokeratin and vimentin, and enterocyte markers like villin, zonula occluden (ZO1), fatty acid binding protein 2 (FABP2) and small intestinal peptidase (IP). Based on the morphology and gene expression profile, 10% FBS has been recommended for culturing primary buffalo IEC on collagen coated plates for 10 days. However, 50% of the successful cultures could not show epithelial phenotype on 10% FBS culture conditions even on collagen coated plates. Interestingly, undifferentiated IEC showed an increasing expression of FABP2, IP and ZO1 transcripts compared to differentiated intestinal cells with 10% FBS on collagen plates. Therefore, future studies are needed to understand the role of FABP2, IP and ZO1 in differentiation of buffalo IEC.

Both the anti- and pro-apoptotic functions of villin regulate cell turnover and intestinal homeostasis

In the small intestine, epithelial cells are derived from stem cells in the crypts, migrate up the villus as they differentiate and are ultimately shed from the villus tips. This process of proliferation and shedding is tightly regulated to maintain the intestinal architecture and tissue homeostasis. Apoptosis regulates both the number of stem cells in the crypts as well as the sloughing of cells from the villus tips. Previously, we have shown that villin, an epithelial cell-specific actin-binding protein functions as an anti-apoptotic protein in the gastrointestinal epithelium. The expression of villin is highest in the apoptosis-resistant villus cells and lowest in the apoptosis-sensitive crypts. In this study we report that villin is cleaved in the intestinal mucosa to generate a pro-apoptotic fragment that is spatially restricted to the villus tips. This cleaved villin fragment severs actin in an unregulated fashion to initiate the extrusion and subsequent apoptosis of effete cells from the villus tips. Using villin knockout mice, we validate the physiological role of villin in apoptosis and cell extrusion from the gastrointestinal epithelium. Our study also highlights the potential role of villin’s pro-apoptotic function in the pathogenesis of inflammatory bowel disease, ischemia-reperfusion injury, enteroinvasive bacterial and parasitic infections.

Proteomics of Urinary Vesicles Links Plakins and Complement to Polycystic Kidney Disease

Novel therapies in autosomal dominant polycystic kidney disease (ADPKD) signal the need for markers of disease progression or response to therapy. This study aimed to identify disease-associated proteins in urinary extracellular vesicles (uEVs), which include exosomes, in patients with ADPKD. We performed quantitative proteomics on uEVs from healthy controls and patients with ADPKD using a labeled approach and then used a label-free approach with uEVs of different subjects (healthy controls versus patients with ADPKD versus patients with non-ADPKD CKD). In both experiments, 30 proteins were consistently more abundant (by two-fold or greater) in ADPKD-uEVs than in healthy- and CKD-uEVs. Of these proteins, we selected periplakin, envoplakin, villin-1, and complement C3 and C9 for confirmation because they were also significantly overrepresented in pathway analysis and were previously implicated in ADPKD pathogenesis. Immunoblotting confirmed higher abundances of the selected proteins in uEVs from three independent groups of patients with ADPKD. Whereas uEVs of young patients with ADPKD and preserved kidney function already had higher levels of complement, only uEVs of patients with advanced stages of ADPKD had increased levels of villin-1, periplakin, and envoplakin. Furthermore, all five proteins correlated positively with total kidney volume. Analysis in kidney tissue from mice with kidney-specific, tamoxifen-inducible Pkd1 deletion demonstrated higher expression in more severe stages of the disease and correlation with kidney weight for each protein of interest. In summary, proteomic analysis of uEVs identified plakins and complement as disease-associated proteins in ADPKD. These proteins are new candidates for evaluation as biomarkers or targets for therapy in ADPKD.

By moonlighting in the nucleus, villin regulates epithelial plasticity

Nuclear villin regulates the expression and activity of Slug, a key transcriptional regulator of epithelial–mesenchymal transition, by directly interacting with its transcriptional corepressor, ZBRK1. Villin accumulates in the nucleus during wound repair, and altering the cellular microenvironment by hypoxia increases the nuclear villin.

Villin is a tissue-specific, actin-binding protein involved in the assembly and maintenance of microvilli in polarized epithelial cells. Conversely, villin is also linked with the loss of epithelial polarity and gain of the mesenchymal phenotype in migrating, invasive cells. In this study, we describe for the first time how villin can switch between these disparate functions to change tissue architecture by moonlighting in the nucleus. Our study reveals that the moonlighting function of villin in the nucleus may play an important role in tissue homeostasis and disease. Villin accumulates in the nucleus during wound repair, and altering the cellular microenvironment by inducing hypoxia increases the nuclear accumulation of villin. Nuclear villin is also associated with mouse models of tumorigenesis, and a systematic analysis of a large cohort of colorectal cancer specimens confirmed the nuclear distribution of villin in a subset of tumors. Our study demonstrates that nuclear villin regulates epithelial–mesenchymal transition (EMT). Altering the nuclear localization of villin affects the expression and activity of Slug, a key transcriptional regulator of EMT. In addition, we find that villin directly interacts with a transcriptional corepressor and ligand of the Slug promoter, ZBRK1. The outcome of this study underscores the role of nuclear villin and its binding partner ZBRK1 in the regulation of EMT and as potential new therapeutic targets to inhibit tumorigenesis.

Giardia duodenalis Surface Cysteine Proteases Induce Cleavage of the Intestinal Epithelial Cytoskeletal Protein Villin via Myosin Light Chain Kinase

Giardia duodenalis infections are among the most common causes of waterborne diarrhoeal disease worldwide. At the height of infection, G. duodenalis trophozoites induce multiple pathophysiological processes within intestinal epithelial cells that contribute to the development of diarrhoeal disease. To date, our understanding of pathophysiological processes in giardiasis remains incompletely understood. The present study reveals a previously unappreciated role for G. duodenalis cathepsin cysteine proteases in intestinal epithelial pathophysiological processes that occur during giardiasis. Experiments first established that Giardia trophozoites indeed produce cathepsin B and L in strain-dependent fashion. Co-incubation of G. duodenalis with human enterocytes enhanced cathepsin production by Assemblage A (NF and S2 isolates) trophozoites, but not when epithelial cells were exposed to Assemblage B (GSM isolate) trophozoites. Direct contact between G. duodenalis parasites and human intestinal epithelial monolayers resulted in the degradation and redistribution of the intestinal epithelial cytoskeletal protein villin; these effects were abolished when parasite cathepsin cysteine proteases were inhibited. Interestingly, inhibition of parasite proteases did not prevent degradation of the intestinal tight junction-associated protein zonula occludens 1 (ZO-1), suggesting that G. duodenalis induces multiple pathophysiological processes within intestinal epithelial cells. Finally, this study demonstrates that G. duodenalis-mediated disruption of villin is, at least, in part dependent on activation of myosin light chain kinase (MLCK). Taken together, this study indicates a novel role for parasite cathepsin cysteine proteases in the pathophysiology of G. duodenalis infections.

Loss of villin immunoexpression in colorectal carcinoma is associated with poor differentiation and survival

Background and Aims. Villin is a highly specialised protein and is expressed in intestinal and renal proximal tubular epithelium. It was detected in colorectal carcinomas (CRC) and other nongastrointestinal tumours. The aim of the current study is to investigate the immunohistochemical expression of villin in a subset of primary CRC and determine its relation to tumour differentiation, invasion, nodal metastasis, recurrence, and disease-free survival. Patients and Methods. Paraffin blocks of 93 cases of CRC were retrieved constituting 93 primary CRC and 58 adjacent normal mucosa. Immunohistochemistry was performed using antivillin antibody. The extent (%) of villin immunoexpression was categorised for statistical analysis. Statistical tests were used to determine the association of villin with clinicopathological characteristics: age, sex, tumour location, tumour size, depth of invasion, tumour grade, nodal metastasis, lymphovascular invasion, margin status, recurrence, and survival. Results. Villin immunostaining results showed that villin is downregulated in CRC. Villin has no association with age, sex, tumour location, depth of invasion, nodal metastasis, lymphovascular invasion, margin status, and recurrence. However, villin is expressed in higher rate in CRC less than 5 cm, well- and moderately differentiated CRC. Poor survival was associated with tumour with low villin immunoexpression. Conclusion. Villin was downregulated in CRC. Villin immunoexpression in CRC is associated with better survival, well-differentiated tumours, and small-sized tumours. Villin has no significant association with disease recurrence or nodal metastasis. More in vivo and in vitro studies are required for further elucidation of how villin may be involved in CRC.

Regulation of intestinal epithelial cell cytoskeletal remodeling by cellular immunity following gut infection

Gut infections often lead to epithelial cell damage followed by a healing response. We examined changes in the epithelial cell cytoskeleton and the involvement of host adaptive immunity in these events using an in vivo model of parasitic infection. We found that both ezrin and villin, key components of the actin cytoskeleton comprising the brush border (BB) of intestinal epithelial cells (IECs), underwent significant post-translational changes following gut infection and during the recovery phase of gut infection. Intriguingly, using mice lacking either CD4(+) or CD8(+) T-cell responses, we demonstrated that the mechanisms by which ezrin and villin are regulated in response to infection are different. Both ezrin and villin undergo proteolysis during the recovery phase of infection. Cleavage of ezrin requires CD4(+) but not CD8(+) T cells, whereas cleavage of villin requires both CD4(+) and CD8(+) T-cell responses. Both proteins were also regulated by phosphorylation; reduced levels of phosphorylated ezrin and increased levels of villin phosphorylation were observed at the peak of infection and correlated with reduced BB enzyme activity. Finally, we show that infection also leads to enhanced proliferation of IECs in this model. Cytoskeletal remodeling in IECs can have critical roles in the immunopathology and healing responses observed during many infectious and non-infectious intestinal conditions. These data indicate that cellular immune responses can be significant drivers of these processes.

Regulation of directional cell migration by membrane-induced actin bundling

During embryonic development and in metastatic cancers, cells detach from the epithelium and migrate with persistent directionality. Directional cell migration is also crucial for the regeneration and maintenance of the epithelium and impaired directional migration is linked to chronic inflammatory diseases. Despite its significance, the mechanisms controlling epithelial cell migration remain poorly understood. Villin is an epithelial-cell-specific actin modifying protein that regulates epithelial cell plasticity and motility. In motile cells villin is associated with the highly branched and the unbranched actin filaments of lamellipodia and filopodia, respectively. In this study we demonstrate for the first time that villin regulates directionally persistent epithelial cell migration. Functional characterization of wild-type and mutant villin proteins revealed that the ability of villin to self-associate and bundle actin as well as its direct interaction with phosphatidylinositol 4,5-bisphosphate [PtdIns(4,5)P(2)] regulates villin-induced filopodial assembly and directional cell migration. Our findings suggest that convergence of different signaling cascades could spatially restrict villin activity to areas of high PtdIns(4,5)P(2) and F-actin concentration to assemble filopodia. Furthermore, our data reveal the ability of villin to undergo actin- and PtdIns(4,5)P(2)-induced self-association, which may be particularly suited to coalesce and reorganize actin bundles within the filopodia.

Actin reorganization as the molecular basis for the regulation of apoptosis in gastrointestinal epithelial cells

The gastrointestinal (GI) epithelium is a rapidly renewing tissue in which apoptosis represents part of the overall homeostatic process. Regulation of apoptosis in the GI epithelium is complex with a precise relationship between cell position and apoptosis. Apoptosis occurs spontaneously and in response to radiation and cytotoxic drugs at the base of the crypts. By contrast, the villus epithelial cells are extremely resistant to apoptosis. The molecular mechanism underlying this loss of function of villus epithelial cells to undergo apoptosis shortly after their exit from the crypt is unknown. In this study we demonstrate for the first time, that deletion of two homologous actin-binding proteins, villin and gelsolin renders villus epithelial cells extremely sensitive to apoptosis. Ultrastructural analysis of the villin-gelsolin(-/-) double-knockout mice shows an abnormal accumulation of damaged mitochondria demonstrating that villin and gelsolin function on an early step in the apoptotic signaling at the level of the mitochondria. A characterization of functional and ligand-binding mutants demonstrate that regulated changes in actin dynamics determined by the actin severing activities of villin and gelsolin are required to maintain cellular homeostasis. Our study provides a molecular basis for the regulation of apoptosis in the GI epithelium and identifies cell biological mechanisms that couple changes in actin dynamics to apoptotic cell death.

The role of actin bundling proteins in the assembly of filopodia in epithelial cells

The goal of this review is to highlight how emerging new models of filopodia assembly, which include tissue specific actin-bundling proteins, could provide more comprehensive representations of filopodia assembly that would describe more adequately and effectively the complexity and plasticity of epithelial cells.  This review also describes how the true diversity of actin bundling proteins must be considered to predict the far-reaching significance and versatile functions of filopodia in epithelial cells.

Differential effects of lysophosphatidic acid and phosphatidylinositol 4,5-bisphosphate on actin dynamics by direct association with the actin-binding protein villin

We have previously reported that the epithelial cell-specific actin-binding protein villin directly associates with phosphatidylinositol 4,5-bisphosphate (PIP(2)) through three binding sites that overlap with actin-binding sites in villin. As a result, association of villin with PIP(2) inhibits actin depolymerization and enhances actin cross-linking by villin. In this study, we demonstrate that these three PIP(2)-binding sites also bind the more hydrophilic phospholipid, lysophosphatidic acid (LPA) but with a higher affinity than PIP(2) (dissociation constant (K(d)) of 22 mum versus 39.5 mum for PIP(2)). More interestingly, unlike PIP(2), the association of villin with LPA inhibits all actin regulatory functions of villin. In addition, unlike PIP(2), LPA dramatically stimulates the tyrosine phosphorylation of villin by c-Src kinase. These studies suggest that in cells, selective interaction of villin with either PIP(2) or LPA could have dramatically different outcomes on actin reorganization as well as phospholipid-regulated cell signaling. These studies provide a novel regulatory mechanism for phospholipid-induced changes in the microfilament structure and cell function and suggest that LPA could be an intracellular regulator of the actin cytoskeleton.

Regulation of cell structure and function by actin-binding proteins: villin's perspective

Villin is a tissue-specific actin modifying protein that is associated with actin filaments in the microvilli and terminal web of epithelial cells. It belongs to a large family of actin-binding proteins which includes actin-capping, -nucleating and/or -severing proteins such as gelsolin, severin, fragmin, adseverin/scinderin and actin crosslinking proteins such as dematin and supervillin. Studies done in epithelial cell lines and villin knock-out mice have demonstrated the function of villin in regulating actin dynamics, cell morphology, epithelial-to-mesenchymal transition, cell migration and cell survival. In addition, the ligand-binding properties of villin (F-actin, G-actin, calcium, phospholipids and phospholipase C-gamma1) are mechanistically important for the crosstalk between signaling pathways and actin reorganization in epithelial cells.

Potential molecular mechanism for c-Src kinase-mediated regulation of intestinal cell migration

The ubiquitously expressed Src tyrosine kinases (c-Src, c-Yes, and c-Fyn) regulate intestinal cell growth and differentiation. Src activity is also elevated in the majority of malignant and premalignant tumors of the colon. The development of fibroblasts with the three ubiquitously expressed kinases deleted (SYF cells) has identified the role of Src proteins in the regulation of actin dynamics associated with increased cell migration and invasion. Despite this, unexpectedly nothing is known about the role of the individual Src kinases on intestinal cell cytoskeleton and/or cell migration. We have previously reported that villin, an epithelial cell-specific actin-modifying protein that regulates actin reorganization, cell morphology, cell migration, cell invasion, and apoptosis, is tyrosine-phosphorylated. In this report using the SYF cells reconstituted individually with c-Src, c-Yes, c-Fyn, and wild type or phosphorylation site mutants of villin, we demonstrate for the first time the absolute requirement for c-Src in villin-induced regulation of cell migration. The other major finding of our study is that contrary to previous reports, the nonreceptor tyrosine kinase, Jak3 (Janus kinase 3), does not regulate phosphorylation of villin or villin-induced cell migration and is, in fact, not expressed in intestinal epithelial cells. Further, we identify SHP-2 and PTP-PEST (protein-tyrosine phosphatase proline-, glutamate-, serine-, and threonine-rich sequence) as negative regulators of c-Src kinase and demonstrate a new function for these phosphatases in intestinal cell migration. Together, these data suggest that in colorectal carcinogenesis, elevation of c-Src or down-regulation of SHP-2 and/or PTP-PEST may promote cancer metastases and invasion by regulating villin-induced cell migration and cell invasion.

Phospholipase C-epsilon regulates epidermal morphogenesis in Caenorhabditis elegans

Migration of cells within epithelial sheets is an important feature of embryogenesis and other biological processes. Previous work has demonstrated a role for inositol 1,4,5-trisphosphate (IP₃)-mediated calcium signalling in the rearrangement of epidermal cells (also known as hypodermal cells) during embryonic morphogenesis in Caenorhabditis elegans. However the mechanism by which IP₃ production is stimulated is unknown. IP₃ is produced by the action of phospholipase C (PLC). We therefore surveyed the PLC family of C. elegans using RNAi and mutant strains, and found that depletion of PLC-1/PLC-ε produced substantial embryonic lethality. We used the epithelial cell marker ajm-1::gfp to follow the behaviour of epidermal cells and found that 96% of the arrested embryos have morphogenetic defects. These defects include defective ventral enclosure and aberrant dorsal intercalation. Using time-lapse confocal microscopy we show that the migration of the ventral epidermal cells, especially of the leading cells, is slower and often fails in plc-1(tm753) embryos. As a consequence plc-1 loss of function results in ruptured embryos with a Gex phenotype (gut on exterior) and lumpy larvae. Thus PLC-1 is involved in the regulation of morphogenesis. Genetic studies using gain- and loss-of-function alleles of itr-1, the gene encoding the IP₃ receptor in C. elegans, demonstrate that PLC-1 acts through ITR-1. Using RNAi and double mutants to deplete the other PLCs in a plc-1 background, we show that PLC-3/PLC-γ and EGL-8/PLC-β can compensate for reduced PLC-1 activity. Our work places PLC-ε into a pathway controlling epidermal cell migration, thus establishing a novel role for PLC-ε.

Morphogenesis is a fundamental part of development which underlies the ability of animals, including humans, to define the shape of their tissues and organs and thus enable their proper function. To understand morphogenesis we need to understand the signalling networks that regulate coordinated changes in cell morphology, movement and adhesion. We know that in C. elegans intracellular signalling through the messenger inositol 1,4,5-trisphosphate (IP₃) is required for the proper completion of the morphogenetic processes. However the mechanism by which this signal is produced remains unclear. In this work we define the mechanism responsible for IP₃ production in C. elegans. We use a combination of genetic and morphological analysis to show that phospholipase C-epsilon (PLC-ε) is the molecule responsible for IP₃ production. In worms with disrupted PLC-ε the embryonic epidermal cells fail to migrate properly so that morphogenesis fails. PLC-ε was only discovered relatively recently and interacts directly with a wide range of signalling pathways, including others that are known to regulate important cellular properties during morphogenesis such as small GTPases. Therefore we establish a potential link between IP₃ signalling and other pathways that are known to be involved in cell movements. This is an important advance in defining the network of interactions that regulate epithelial cell movements in morphogenesis.

Cell responses regulated by early reorganization of actin cytoskeleton

Microfilaments exist in a dynamic equilibrium between monomeric and polymerized actin and the ratio of monomers to polymeric forms is influenced by a variety of extracellular stimuli. The polymerization, depolymerization and redistribution of actin filaments are modulated by several actin-binding proteins, which are regulated by upstream signalling molecules. Actin cytoskeleton is involved in diverse cellular functions including migration, ion channels activity, secretion, apoptosis and cell survival. In this review we have outlined the role of actin dynamics in representative cell functions induced by the early response to extracellular stimuli.

Autotaxin and lysophosphatidic acid stimulate intestinal cell motility by redistribution of the actin modifying protein villin to the developing lamellipodia

Autotaxin (ATX) is a potent tumor cell motogen that can produce lysophosphatidic acid (LPA) from lysophosphatidylcholine. LPA is a lipid mediator that has also been shown to modulate tumor cell invasion. Autotaxin mRNA is expressed at significant levels in the intestine. Likewise, LPA2 receptor levels have been shown to be elevated in colon cancers. The molecular mechanism of ATX/LPA-induced increase in intestinal cell migration however, remains poorly understood. Villin is an intestinal and renal epithelial cell specific actin regulatory protein that modifies epithelial cell migration. In this study we demonstrate that both Caco-2 (endogenous villin) and MDCK (exogenous villin) cells, which express primarily LPA2 receptors, show enhanced cell migration in response to ATX/LPA. ATX and LPA treatment results in the rapid formation of lamellipodia and redistribution of villin to these cell surface structures, suggesting a role for villin in regulating this initial event of cell locomotion. The LPA-induced increase in cell migration required activation of c-src kinase and downstream tyrosine phosphorylation of villin by c-src kinase. LPA stimulated cell motility was determined to be insensitive to pertussis toxin, but was regulated by activation of PLC-gamma 1. Together, our results show that in epithelial cells ATX and LPA act as strong stimulators of cell migration by recruiting PLC-gamma 1 and villin, both of which participate in the initiation of protrusion.

Downregulation of gelsolin family proteins counteracts cancer cell invasion in vitro

Gelsolin and CapG are both actin binding proteins that modulate a variety of physiological processes by interacting differently with the actin cytoskeleton. Several studies suggest that overexpression of these proteins promotes invasion in vitro. In this study we explored the contribution of these proteins in human cancer cell invasion and motility. We show that down regulation of CapG or gelsolin in several types of cancer cells, including MDA-MB 231 and PC-3 cells, significantly reduces the invasive and motile properties of cells, as well as cell aggregation. These results point to a role for CapG and gelsolin as tumor activator.