WIP is necessary for matrix invasion by breast cancer cells

A Triple-pose Complex Between an Extended WIP Motif and a C-terminal SH3 Domain Modulates Cortactin Activity

The central domain of WASp-interacting protein (WIP) interacts with the cortactin SH3 domain through a previously undefined binding motif. This interaction affects extracellular matrix (ECM) degradation and the invasive phenotype of cells. Here, using NMR-based methods, we identify the major WIP epitope modulating this binding event as residues 168-183, an unexpectedly long segment uncharacteristic of SH3 peptidic ligands. A scanning mutagenesis analysis showed that peptide binding 'hotspots' are distributed throughout the binding sequence. To uncover the structural basis of WIP-cortactin recognition we utilized edited-filtered NOESY experiments to determine the structure of the intermediate-affinity SH3/peptide complex. Analysis of the NOESY pattern suggests that the peptide sequence dictates three interchanging binding modes, two oppositely oriented canonical poses involving N-terminal interactions, corresponding to class I and class II complexes, and a non-canonical pseudo-class II pose involving C-terminal interactions. The latter pose highlights the importance of the hydrophobic surface adjacent to the canonical binding grooves and accounts for the extended binding motif. Design of mutant peptides with increased affinity based on this multi-conformational complex demonstrates how these structural insights may impact design of improved inhibitors of the WIP-cortactin interaction with potential therapeutic applications.

Sos1 ablation alters focal adhesion dynamics and increases Mmp2/9-dependent gelatinase activity in primary mouse embryonic fibroblasts

BACKGROUND

Sos1 and Sos2 are guanine-nucleotide exchange factors for Ras and Rac small GTPases, which are involved in a wide range of cellular responses including proliferation and migration. We have previously shown that Sos1 and Sos2 have different effects on cell migration, but the underlying mechanisms are not clear.

METHODS

Using a 4-hydroxytamoxifen-inducible conditional Sos1KO mutation, here we evaluated the functional specificity or redundancy of Sos1 and Sos2 regarding the control of cell migration and dynamics of focal adhesions (FAs) in primary mouse embryonic fibroblasts (MEFs).

RESULTS

Functional analysis of the transcriptome of primary Sos1/2WT, Sos1KO, Sos2KO and Sos1/2DKO-MEFs revealed a specific, dominant role of Sos1 over Sos2 in transcriptional regulation. Sos1KO MEFs had an increased number and stability of focal adhesions (FAs) and curbed protrusion and spreading. Conversely, Sos2KO MEFs displayed unstable FAs with increased protrusion. Interestingly, Sos1, but not Sos2, ablation reduced the levels of GTP-bound Rac at the leading edge. In 3D, however, only Sos1/2KO MEFs showed increased invasion and matrix degradative capacity, which correlated with increased expression of the Mmp2 and Mmp9 gelatinases. Moreover, increased matrix degradation in Sos1/2KO MEFs was abrogated by treatment with Mmp2/9 inhibitors.

CONCLUSIONS

Our data demonstrate that Sos1 and Sos2 have different functions in FAs distribution and dynamics in 2D whereas in 3D they act together to regulate invasion and unveil a previously undescribed mechanistic connection between Sos1/2 and the regulation of Mmp2/9 expression in primary MEFs.

Multifaceted role of the actin-binding protein WIP: Promotor and inhibitor of tumor progression and dissemination

Cancer cells depend on actin cytoskeleton reorganization to achieve hallmark malignant functions including abnormal activation, proliferation, migration and invasiveness. (Neural)-Wiskott-Aldrich Syndrome protein ((N-)WASP) binds actin and forms a complex with the WASP-interacting protein (WIP), which plays a critical role in regulating the actin cytoskeleton, through (N)-WASP-dependent and independent functions. Mutations in the WIP gene (WIPF1) lead to severe early onset immunodeficiency in humans and severe autoimmunity and shortened lifespan in mice. This review covers the available evidence about the physiological role of WIP in different tissues and its contribution to human disease, focusing on cancer. In solid tumors overexpression of WIP has mostly been associated with tumor initiation, progression and dissemination through matrix degradation by invadopodia, while a suppressive function has been shown for WIP in certain hematological cancers. Interestingly, a minority of studies suggest a protective role for WIP in specific tumor contexts. These data support the need for further research to fully understand the mechanisms underlying WIP's diverse functions in health and disease and raise important questions for future work.

Analysis of H3K4me3-ChIP-Seq and RNA-Seq data to understand the putative role of miRNAs and their target genes in breast cancer cell lines

Breast cancer is one of the leading causes of cancer in women all over the world and accounts for ~25% of newly observed cancers in women. Epigenetic modifications influence differential expression of genes through non-coding RNA and play a crucial role in cancer regulation. In the present study, epigenetic regulation of gene expression by in-silico analysis of histone modifications using chromatin immunoprecipitation sequencing (ChIP-Seq) has been carried out. Histone modification data of H3K4me3 from one normal-like and four breast cancer cell lines were used to predict miRNA expression at the promoter level. Predicted miRNA promoters (based on ChIP-Seq) were used as a probe to identify gene targets. Five triple-negative breast cancer (TNBC)‒specific miRNAs (miR153-1, miR4767, miR4487, miR6720, and miR-LET7I) were identified and corresponding 13 gene targets were predicted. Eight miRNA promoter peaks were predicted to be differentially expressed in at least three breast cancer cell lines (miR4512, miR6791, miR330, miR3180-3, miR6080, miR5787, miR6733, and miR3613). A total of 44 gene targets were identified based on the 3′-untranslated regions of downregulated mRNA genes that contain putative binding targets to these eight miRNAs. These include 17 and 15 genes in luminal-A type and TNBC respectively, that have been reported to be associated with breast cancer regulation. Of the remaining 12 genes, seven (A4GALT, C2ORF74, HRCT1, ZC4H2, ZNF512, ZNF655, and ZNF608) show similar relative expression profiles in large patient samples and other breast cancer cell lines thereby giving insight into predicted role of H3K4me3 mediated gene regulation via the miRNA-mRNA axis.

The Disordered Cellular Multi-Tasker WIP and Its Protein-Protein Interactions: A Structural View

WASp-interacting protein (WIP), a regulator of actin cytoskeleton assembly and remodeling, is a cellular multi-tasker and a key member of a network of protein-protein interactions, with significant impact on health and disease. Here, we attempt to complement the well-established understanding of WIP function from cell biology studies, summarized in several reviews, with a structural description of WIP interactions, highlighting works that present a molecular view of WIP's protein-protein interactions. This provides a deeper understanding of the mechanisms by which WIP mediates its biological functions. The fully disordered WIP also serves as an intriguing example of how intrinsically disordered proteins (IDPs) exert their function. WIP consists of consecutive small functional domains and motifs that interact with a host of cellular partners, with a striking preponderance of proline-rich motif capable of interactions with several well-recognized binding partners; indeed, over 30% of the WIP primary structure are proline residues. We focus on the binding motifs and binding interfaces of three important WIP segments, the actin-binding N-terminal domain, the central domain that binds SH3 domains of various interaction partners, and the WASp-binding C-terminal domain. Beyond the obvious importance of a more fundamental understanding of the biology of this central cellular player, this approach carries an immediate and highly beneficial effect on drug-design efforts targeting WIP and its binding partners. These factors make the value of such structural studies, challenging as they are, readily apparent.

Loss of Wasl improves pancreatic cancer outcome

Several studies have suggested an oncogenic role for the neural Wiskott-Aldrich syndrome protein (N-WASP, encoded by the Wasl gene), but thus far, little is known about its function in pancreatic ductal adenocarcinoma (PDAC). In this study, we performed in silico analysis of WASL expression in PDAC patients and found a correlation between low WASL expression and prolonged survival. To clarify the role of Wasl in pancreatic carcinogenesis, we used 2 oncogenic Kras-based PDAC mouse models with pancreas-specific Wasl deletion. In line with human data, both mouse models had an increased survival benefit due to either impaired tumor development in the presence of the tumor suppressor Trp53 or the delayed tumor progression and senescent phenotype upon genetic ablation of Trp53. Mechanistically, loss of Wasl resulted in cell-autonomous senescence through displacement of the N-WASP binding partners WASP-interacting protein (WIP) and p120ctn; vesicular accumulation of GSK3β, as well as YAP1 and phosphorylated β-catenin, which are components of the destruction complex; and upregulation of Cdkn1a(p21), a master regulator of senescence. Our findings, thus, indicate that Wasl functions in an oncogenic manner in PDAC by promoting the deregulation of the p120-catenin/β-catenin/p21 pathway. Therefore, strategies to reduce N-WASP activity might improve the survival outcomes of PDAC patients.

WIP/ITSN1 complex is involved in cellular vesicle trafficking and formation of filopodia-like protrusions

WIP (WASP interacting protein) together with N-WASP (neural Wiskott-Aldrich syndrome protein) regulates actin polymerization that is crucial for invadopodia and filopodia formation. Recently, we reported the WIP interaction with ITSN1 which is highly implicated in endo-/exocytosis, apoptosis, mitogenic signaling and cytoskeleton rearrangements. Here we demonstrate that the WIP/ITSN1 complex is involved in the transferrin receptor recycling and partially co-localizes with a marker of the fast recycling endosomes, RAB4. Moreover, ITSN1 recruits WIP to RAB4-positive vesicles upon overexpression. Our data indicate that WIP enhances the interaction of N-WASP with ITSN1 and promotes ITSN1/β-actin association. Moreover, the WIP/ITSN1-L complex facilitates formation of filopodia-like protrusions in MCF-7 cells. Thus, WIP/ITSN1 complex is involved in the cellular vesicle trafficking and actin-dependent membrane processes.

Epigenetically upregulated WIPF1 plays a major role in BRAF V600E-promoted papillary thyroid cancer aggressiveness

How the BRAF V600E mutation promotes the pathogenesis and aggressiveness of papillary thyroid cancer (PTC) is not completely understood. Here we explored a novel mechanism involving WASP interacting protein family member 1 (WIPF1). In PTC tumors, compared with the wild-type BRAF, BRAF V600E was associated with over-expression and hypomethylation of the WIPF1 gene. In thyroid cancer cell lines with wild-type BRAF, WIPF1 expression was robustly upregulated upon introduced expression of BRAF V600E (P=0.03) whereas the opposite was seen upon BRAF knockdown or treatment with BRAF V600E or MEK inhibitors in cells harboring BRAF V600E. Methylation of a functionally critical region of the WIPF1 promoter was decreased by expressing BRAF V600E in cells harboring the wild-type BRAF and increased by BRAF knockdown or treatment with BRAF V600E or MEK inhibitors in cells harboring BRAF V600E mutation. Under-expression and hypermethylation of WIPF1 induced by stable BRAF knockdown was reversed by DNA demethylating agent 5′-azadeoxycytidine. Knockdown of WIPF1 robustly inhibited anchorage-independent colony formation, migration, and invasion of thyroid cancer cells and suppressed xenograft thyroid cancer tumor growth and vascular invasion, mimicking the effects of BRAF knockdown. In human PTC tumors, WIPF1 expression was associated with extrathyroidal invasion (P=0.01) and lymph node metastasis (P=2.64E-05). In summary, BRAF V600E-activated MAP kinase pathway causes hypomethylation and overexpression of WIPF1; WIPF1 then functions like an oncoprotein to robustly promote aggressive cellular and tumor behaviors of PTC. This represents a novel mechanism in BRAF V600E-promoted PTC aggressiveness and identifies WIPF1 as a novel therapeutic target for thyroid cancer.

Crosstalk between WIP and Rho family GTPases

Through actin-binding proteins such as the neural Wiskott-Aldrich syndrome protein (N-WASP) and WASP-interacting protein (WIP), the Rho family GTPases RhoA, Rac1 and Cdc42 are major modulators of the cytoskeleton. (N-)WASP and WIP control Rho GTPase activity in various cell types, either by direct WIP/(N-)WASP/Cdc42 or potential WIP/RhoA binding, or through secondary links that regulate GTPase distribution and/or transcription levels. WIP helps to regulate filopodium generation and participates in the Rac1-mediated ruffle formation that determines cell motility. In neurons, lack of WIP increases dendritic spine size and filamentous actin content in a RhoA-dependent manner. In contrast, WIP deficiency in an adenocarcinoma cell line significantly reduces RhoA levels. These data support a role for WIP in the GTPase-mediated regulation of numerous actin-related cell functions; we discuss the possibility that this WIP effect is linked to cell proliferative status.

The Arp2/3 Regulatory System and Its Deregulation in Cancer

The Arp2/3 complex is an evolutionary conserved molecular machine that generates branched actin networks. When activated, the Arp2/3 complex contributes the actin branched junction and thus cross-links the polymerizing actin filaments in a network that exerts a pushing force. The different activators initiate branched actin networks at the cytosolic surface of different cellular membranes to promote their protrusion, movement, or scission in cell migration and membrane traffic. Here we review the structure, function, and regulation of all the direct regulators of the Arp2/3 complex that induce or inhibit the initiation of a branched actin network and that controls the stability of its branched junctions. Our goal is to present recent findings concerning novel inhibitory proteins or the regulation of the actin branched junction and place these in the context of what was previously known to provide a global overview of how the Arp2/3 complex is regulated in human cells. We focus on the human set of Arp2/3 regulators to compare normal Arp2/3 regulation in untransformed cells to the deregulation of the Arp2/3 system observed in patients affected by various cancers. In many cases, these deregulations promote cancer progression and have a direct impact on patient survival.

WIP Drives Tumor Progression through YAP/TAZ-Dependent Autonomous Cell Growth

In cancer, the deregulation of growth signaling pathways drives changes in the cell's architecture and its environment that allow autonomous growth of tumors. These cells then acquire a tumor-initiating "stemness" phenotype responsible for disease advancement to more aggressive stages. Here, we show that high levels of the actin cytoskeleton-associated protein WIP (WASP-interacting protein) correlates with tumor growth, both of which are linked to the tumor-initiating cell phenotype. We find that WIP controls tumor growth by boosting signals that stabilize the YAP/TAZ complex via a mechanism mediated by the endocytic/endosomal system. When WIP levels are high, the β-catenin Adenomatous polyposis coli (APC)-axin-GSK3 destruction complex is sequestered to the multi-vesicular body compartment, where its capacity to degrade YAP/TAZ is inhibited. YAP/TAZ stability is dependent on Rac, p21-activated kinase (PAK) and mammalian diaphanous-related formin (mDia), and is Hippo independent. This close biochemical relationship indicates an oncogenic role for WIP in the physiology of cancer pathology by increasing YAP/TAZ stability.

WIP promotes in-vitro invasion ability, anchorage independent growth and EMT progression of A549 lung adenocarcinoma cells by regulating RhoA levels

Cancer cell migration and invasion involves actin cytoskeleton reorganization, which is regulated by the WASP (Wiskott Aldrich Syndrome Protein) family of proteins such as WASP, N-WASP (Neural-WASP) and WASP interacting protein (WIP). In this study, we found that the expression of WIP was significantly upregulated in metastatic A5-RT3 cells compared to its parental non-tumorigenic HaCaT cells. Using A549 human lung adenocarcinoma cell line as the model system, we found that WIP regulates cell invasion, proliferation and anchorage-independent growth. Expression of WIP was enhanced during TGF-β1 induced epithelial-mesenchymal transition (EMT) and overexpression of WIP accelerated EMT while knocking down WIP attenuated EMT associated morphological changes. Knocking down WIP expression in A549 cells significantly reduced RhoA levels and WIP was found to interact with RhoA suggesting that WIP might be executing its function by regulating RhoA. Acquisition of invasive, proliferative properties and anoikis resistance is the central step in metastasis indicating a novel function of WIP in cancer progression.

Phosphatidylinositol 4-kinase IIβ negatively regulates invadopodia formation and suppresses an invasive cellular phenotype

The type II phosphatidylinositol 4-kinase (PI4KII) enzymes synthesize the lipid phosphatidylinositol 4-phosphate (PI(4)P), which has been detected at the Golgi complex and endosomal compartments and recruits clathrin adaptors. Despite common mechanistic similarities between the isoforms, the extent of their redundancy is unclear. We found that depletion of PI4KIIα and PI4KIIβ using small interfering RNA led to actin remodeling. Depletion of PI4KIIβ also induced the formation of invadopodia containing membrane type I matrix metalloproteinase (MT1-MMP). Depletion of PI4KII isoforms also differentially affected trans-Golgi network (TGN) pools of PI(4)P and post-TGN traffic. PI4KIIβ depletion caused increased MT1-MMP trafficking to invasive structures at the plasma membrane and was accompanied by reduced colocalization of MT1-MMP with membranes containing the endosomal markers Rab5 and Rab7 but increased localization with the exocytic Rab8. Depletion of PI4KIIβ was sufficient to confer an aggressive invasive phenotype on minimally invasive HeLa and MCF-7 cell lines. Mining oncogenomic databases revealed that loss of the PI4K2B allele and underexpression of PI4KIIβ mRNA are associated with human cancers. This finding supports the cell data and suggests that PI4KIIβ may be a clinically significant suppressor of invasion. We propose that PI4KIIβ synthesizes a pool of PI(4)P that maintains MT1-MMP traffic in the degradative pathway and suppresses the formation of invadopodia.

The ZEB1/miR-200c feedback loop regulates invasion via actin interacting proteins MYLK and TKS5

Epithelial to mesenchymal transition (EMT) is a developmental process which is aberrantly activated during cancer invasion and metastasis. Elevated expression of EMT-inducers like ZEB1 enables tumor cells to detach from the primary tumor and invade into the surrounding tissue. The main antagonist of ZEB1 in controlling EMT is the microRNA-200 family that is reciprocally linked to ZEB1 in a double negative feedback loop. Here, we further elucidate how the ZEB1/miR-200 feedback loop controls invasion of tumor cells. The process of EMT is attended by major changes in the actin cytoskeleton. Via in silico screening of genes encoding for actin interacting proteins, we identified two novel targets of miR-200c - TKS5 and MYLK (MLCK). Co-expression of both genes with ZEB1 was observed in several cancer cell lines as well as in breast cancer patients and correlated with low miR-200c levels. Depletion of TKS5 or MYLK in breast cancer cells reduced their invasive potential and their ability to form invadopodia. Whereas TKS5 is known to be a major component, we could identify MYLK as a novel player in invadopodia formation. In summary, TKS5 and MYLK represent two mediators of invasive behavior of cancer cells that are regulated by the ZEB1/miR-200 feedback loop.

WIP and WICH/WIRE co-ordinately control invadopodium formation and maturation in human breast cancer cell invasion

Cancer cells form actin-rich degradative protrusions (invasive pseudopods and invadopodia), which allows their efficient dispersal during metastasis. Using biochemical and advanced imaging approaches, we demonstrate that the N-WASP-interactors WIP and WICH/WIRE play non-redundant roles in cancer cell invasion. WIP interacts with N-WASP and cortactin and is essential for invadopodium assembly, whereas WICH/WIRE regulates N-WASP activation to control invadopodium maturation and degradative activity. Our data also show that Nck interaction with WIP and WICH/WIRE modulates invadopodium maturation; changes in WIP and WICH/WIRE levels induce differential distribution of Nck. We show that WIP can replace WICH/WIRE functions and that elevated WIP levels correlate with high invasiveness. These findings identify a role for WICH/WIRE in invasiveness and highlight WIP as a hub for signaling molecule recruitment during invadopodium generation and cancer progression, as well as a potential diagnostic biomarker and an optimal target for therapeutic approaches.

Invadopodia proteins, cortactin, N-WASP and WIP differentially promote local invasiveness in ameloblastoma

BACKGROUND

Cell migration and invasion through interstitial tissues are dependent upon several specialized characteristics of the migratory cell notably generation of proteolytic membranous protrusions or invadopodia. Ameloblastoma is a benign odontogenic epithelial neoplasm with a locally infiltrative behaviour. Cortactin and MMT1-MMP are two invadopodia proteins implicated in its local invasiveness. Other invadopodia regulators, namely N-WASP, WIP and Src kinase remain unclarified. This study addresses their roles in ameloblastoma.

MATERIALS AND METHOD

Eighty-seven paraffin-embedded ameloblastoma cases (20 unicystic, 47 solid/multicystic, 3 desmoplastic and 17 recurrent) were subjected to immunohistochemistry for expression of cortactin, N-WASP, WIP, Src kinase and F-actin, and findings correlated with clinicopathological parameters.

RESULTS

Invadopodia proteins (except Src kinase) and F-actin were widely detected in ameloblastoma (cortactin: n = 73/87, 83.9%; N-WASP: n = 59/87; 67.8%; WIP: n = 77/87; 88.5%; and F-actin: n = 87/87, 100%). Protein localization was mainly cytoplasmic and/or membranous, and occasionally nuclear for F-actin. Cortactin, which functions as an actin-scaffolding protein, demonstrated significantly higher expression levels within ameloblastoma tumoral epithelium than in stroma (P < 0.05). N-WASP, which coordinates actin polymerization and invadopodia-mediated extracellular matrix degradation, was overexpressed in the solid/multicystic subtype (P < 0.05). WIP, an upstream regulator of N-WASP, and F-actin were significantly upregulated along the tumour invasive front compared to tumour centres (P < 0.05). Except for males with cortactin overexpression, other clinical parameters (age, ethnicity and anatomical site) showed no significant correlations.

CONCLUSIONS

Present results suggest that local invasiveness of ameloblastoma is dependent upon the migratory potential of its tumour cells as defined by their distribution of cortactin, N-WASP and WIP in correlation with F-actin cytoskeletal dynamics.

Intersectin adaptor proteins are associated with actin-regulating protein WIP in invadopodia

Invasive cancer cells form actin-rich membrane protrusions called invadopodia that degrade extracellular matrix and facilitate cell invasion and metastasis. WIP (WASP-interacting protein) together with N-WASP (neural Wiskott-Aldrich syndrome protein) are localized in invadopodia and play a crucial role in their formation. Here we show that WIP interacts with endocytic adaptor proteins of the intersectin (ITSN) family, ITSN1 and ITSN2. The interaction is mediated by the SH3 domains of ITSNs and the middle part of the WIP proline-rich motifs. We have also demonstrated that ITSN1, WIP and N-WASP can form a complex in cells. Endogenous ITSN1 and ITSN2 are located in invasive protrusions of MDA-MB-231 breast cancer cell line. Moreover, data from immunofluorescent analysis revealed co-localization of ITSN1 and WIP at sites of invadopodia formation and in clathrin-coated pits. Together, these findings provide insights into the molecular mechanisms of invadopodia formation and identify ITSNs as scaffold proteins involved in this process.