Focal Adhesion Kinase Regulation of N-WASP Subcellular Localization and Function

VAMP2 controls murine epidermal differentiation and carcinogenesis by regulation of nucleophagy

Differentiation of murine epidermal stem/progenitor cells involves the permanent withdrawal from the cell cycle, the synthesis of various protein and lipid components for the cornified envelope, and the controlled dissolution of cellular organelles and nuclei. Deregulated epidermal differentiation contributes to the development of various skin diseases, including skin cancers. With a genome-wide shRNA screen, we identified vesicle-associated membrane protein 2 (VAMP2) as a critical factor involved in skin differentiation. Deletion of VAMP2 leads to aberrant skin stratification and enucleation in vivo. With quantitative proteomics, we further identified an autophagy protein, focal adhesion kinase family interacting protein of 200 kDa (FIP200), as a binding partner of VAMP2. Additionally, we showed that both VAMP2 and FIP200 are critical for murine keratinocyte enucleation and epidermal differentiation. Loss of VAMP2 or FIP200 enhances cutaneous carcinogenesis in vivo. Together, our findings identify important molecular mechanisms underlying epidermal differentiation and skin tumorigenesis.

Membrane adhesion junctions regulate airway smooth muscle phenotype and function

The local environment surrounding airway smooth muscle (ASM) cells has profound effects on the physiological and phenotypic properties of ASM tissues. ASM is continually subjected to the mechanical forces generated during breathing and to the constituents of its surrounding extracellular milieu. The smooth muscle cells within the airways continually modulate their properties to adapt to these changing environmental influences. Smooth muscle cells connect to the extracellular cell matrix (ECM) at membrane adhesion junctions that provide mechanical coupling between smooth muscle cells within the tissue. Membrane adhesion junctions also sense local environmental signals and transduce them to cytoplasmic and nuclear signaling pathways in the ASM cell. Adhesion junctions are composed of clusters of transmembrane integrin proteins that bind to ECM proteins outside the cell and to large multiprotein complexes in the submembranous cytoplasm. Physiological conditions and stimuli from the surrounding ECM are sensed by integrin proteins and transduced by submembranous adhesion complexes to signaling pathways to the cytoskeleton and nucleus. The transmission of information between the local environment of the cells and intracellular processes enables ASM cells to rapidly adapt their physiological properties to modulating influences in their extracellular environment: mechanical and physical forces that impinge on the cell, ECM constituents, local mediators, and metabolites. The structure and molecular organization of adhesion junction complexes and the actin cytoskeleton are dynamic and constantly changing in response to environmental influences. The ability of ASM to rapidly accommodate to the ever-changing conditions and fluctuating physical forces within its local environment is essential for its normal physiological function.

Branching out in different directions: Emerging cellular functions for the Arp2/3 complex and WASP-family actin nucleation factors

The actin cytoskeleton impacts practically every function of a eukaryotic cell. Historically, the best-characterized cytoskeletal activities are in cell morphogenesis, motility, and division. The structural and dynamic properties of the actin cytoskeleton are also crucial for establishing, maintaining, and changing the organization of membrane-bound organelles and other intracellular structures. Such activities are important in nearly all animal cells and tissues, although distinct anatomical regions and physiological systems rely on different regulatory factors. Recent work indicates that the Arp2/3 complex, a broadly expressed actin nucleator, drives actin assembly during several intracellular stress response pathways. These newly described Arp2/3-mediated cytoskeletal rearrangements are coordinated by members of the Wiskott-Aldrich Syndrome Protein (WASP) family of actin nucleation-promoting factors. Thus, the Arp2/3 complex and WASP-family proteins are emerging as crucial players in cytoplasmic and nuclear activities including autophagy, apoptosis, chromatin dynamics, and DNA repair. Characterizations of the functions of the actin assembly machinery in such stress response mechanisms are advancing our understanding of both normal and pathogenic processes, and hold great promise for providing insights into organismal development and interventions for disease.

WASP family proteins: Molecular mechanisms and implications in human disease

Proteins of the Wiskott-Aldrich syndrome protein (WASP) family play a central role in regulating actin cytoskeletal dynamics in a wide range of cellular processes. Genetic mutations or misregulation of these proteins are tightly associated with many diseases. The WASP-family proteins act by transmitting various upstream signals to their conserved WH2-Central-Acidic (WCA) peptide sequence at the C-terminus, which in turn binds to the Arp2/3 complex to stimulate the formation of branched actin networks at membranes. Despite this common feature, the regulatory mechanisms and cellular functions of distinct WASP-family proteins are very different. Here, we summarize and clarify our current understanding of WASP-family proteins and how disruption of their functions is related to human disease.

Evaluation of Biological Effects and Transcriptome Changes Induced by LED Based Narrow Band UVB Phototherapy

Ultraviolet (UV), particularly UVB, is widely used in the treatment of skin diseases including psoriasis, atopic dermatitis, vitiligo, mycosis fungoides, and pruritus. Recently, there has been a trend of replacing broad band UVB (BB-UVB) units with narrow band UVB (NB-UVB), as studies have demonstrated that NB-UVB is more efficacious in the treatment of psoriasis. The purpose of this study is to evaluate the biological effects and transcriptome changes induced by light emitting diode based NB-UVB (NB-UVB LED) phototherapy. Cell viability and the cell migration ability was significantly decreased post treatment, as well as apoptosis and ROS levels were remarkably increased. NB-UVB induced S phase arrest was observed 12 hours post irradiation. Bioinformatics analysis of transcriptome sequencing data revealed that NB-UVB LED irradiation induced dose-depended changes in multiple key signaling pathways, such as PI3K and cytoskeletal-related pathways. The depolymerization of cytoskeleton induced by NB-UVB was observed 24 hours post treatment. In addition, the expression levels of cytoskeleton related proteins FN1, ITGB4, ITGA1, RAC2 and DOCK1 decreased significantly 12 hours after irradiation. Our results indicated that NB-UVB LED may serve as a novel option for the development of NB-UVB phototherapy devices.

FAK in Cancer: From Mechanisms to Therapeutic Strategies

Focal adhesion kinase (FAK), a non-receptor tyrosine kinase, is overexpressed and activated in many cancer types. FAK regulates diverse cellular processes, including growth factor signaling, cell cycle progression, cell survival, cell motility, angiogenesis, and the establishment of immunosuppressive tumor microenvironments through kinase-dependent and kinase-independent scaffolding functions in the cytoplasm and nucleus. Mounting evidence has indicated that targeting FAK, either alone or in combination with other agents, may represent a promising therapeutic strategy for various cancers. In this review, we summarize the mechanisms underlying FAK-mediated signaling networks during tumor development. We also summarize the recent progress of FAK-targeted small-molecule compounds for anticancer activity from preclinical and clinical evidence.

A Cas-BCAR3 co-regulatory circuit controls lamellipodia dynamics

Integrin adhesion complexes regulate cytoskeletal dynamics during cell migration. Adhesion activates phosphorylation of integrin-associated signaling proteins, including Cas (p130Cas, BCAR1), by Src-family kinases. Cas regulates leading-edge protrusion and migration in cooperation with its binding partner, BCAR3. However, it has been unclear how Cas and BCAR3 cooperate. Here, using normal epithelial cells, we find that BCAR3 localization to integrin adhesions requires Cas. In return, Cas phosphorylation, as well as lamellipodia dynamics and cell migration, requires BCAR3. These functions require the BCAR3 SH2 domain and a specific phosphorylation site, Tyr 117, that is also required for BCAR3 downregulation by the ubiquitin-proteasome system. These findings place BCAR3 in a co-regulatory positive-feedback circuit with Cas, with BCAR3 requiring Cas for localization and Cas requiring BCAR3 for activation and downstream signaling. The use of a single phosphorylation site in BCAR3 for activation and degradation ensures reliable negative feedback by the ubiquitin-proteasome system.

Disruption of anchoring junctions in the testes of experimental varicocele rats

Varicocele is a common disease of the male reproductive system and is the main cause of male infertility; however, the pathological mechanisms of varicocele remain unclear. The anchoring junctions (AJs) in the testies are located between Sertoli cells, or between Sertoli cells and germ cells. Intact and functional AJs are crucial for spermatogenesis. In the present study, the histomorphology, ultrastructure of AJ, cell cycle, expression of AJ structural proteins, and the level of AJ-associated signaling molecules were investigated in the left testes of experimental varicocele rats at 8 and 12 weeks after surgery. The results revealed that varicocele induced the loss of premature germ cells from the seminiferous epithelium. Furthermore, the results of the present study also revealed damage to the AJ ultrastructure, disorientation of the spermatid head, deregulation of the cell cycle, downregulation of AJ structural proteins, enhanced phosphorylation of focal adhesion kinase (FAK) at Tyr³⁹⁷ and its downstream adapter Src at Tyr⁴¹⁶, and activation of the extracellular signal-regulated protein kinase 1 (ERK1) signaling pathway. Thus, the present study demonstrated that varicocele disrupted the structure and function of AJs in the left testes of rats, and that enhancement of FAK phosphorylation may contribute to AJ damage by activating ERK1 signaling, disrupting actin-based filament networks, and altering the balance of the apical ectoplasmic specialization-blood testis barrier functional axis. These findings provide important insights into the pathological mechanisms through which varicocele contributes to male infertility and could help to identify new therapeutic targets for varicocele.

N6 -methyladenosine modification of lncRNA Pvt1 governs epidermal stemness

Dynamic chemical modifications of RNA represent novel and fundamental mechanisms that regulate stemness and tissue homeostasis. Rejuvenation and wound repair of mammalian skin are sustained by epidermal progenitor cells, which are localized within the basal layer of the skin epidermis. N⁶ -methyladenosine (m⁶ A) is one of the most abundant modifications found in eukaryotic mRNA and lncRNA (long noncoding RNA). In this report, we survey changes of m⁶ A RNA methylomes upon epidermal differentiation and identify Pvt1, a lncRNA whose m⁶ A modification is critically involved in sustaining stemness of epidermal progenitor cells. With genome-editing and a mouse genetics approach, we show that ablation of m⁶ A methyltransferase or Pvt1 impairs the self-renewal and wound healing capability of skin. Mechanistically, methylation of Pvt1 transcripts enhances its interaction with MYC and stabilizes the MYC protein in epidermal progenitor cells. Our study presents a global view of epitranscriptomic dynamics that occur during epidermal differentiation and identifies the m⁶ A modification of Pvt1 as a key signaling event involved in skin tissue homeostasis and wound repair.

Focal Adhesion Kinase Fine Tunes Multifaced Signals toward Breast Cancer Progression

Breast cancer represents the most common diagnosed malignancy and the main leading cause of tumor-related death among women worldwide. Therefore, several efforts have been made in order to identify valuable molecular biomarkers for the prognosis and prediction of therapeutic responses in breast tumor patients. In this context, emerging discoveries have indicated that focal adhesion kinase (FAK), a non-receptor tyrosine kinase, might represent a promising target involved in breast tumorigenesis. Of note, high FAK expression and activity have been tightly correlated with a poor clinical outcome and metastatic features in several tumors, including breast cancer. Recently, a role for the integrin-FAK signaling in mechanotransduction has been suggested and the function of FAK within the breast tumor microenvironment has been ascertained toward tumor angiogenesis and vascular permeability. FAK has been also involved in cancer stem cells (CSCs)-mediated initiation, maintenance and therapeutic responses of breast tumors. In addition, the potential of FAK to elicit breast tumor-promoting effects has been even associated with the capability to modulate immune responses. On the basis of these findings, several agents targeting FAK have been exploited in diverse preclinical tumor models. Here, we recapitulate the multifaceted action exerted by FAK and its prognostic significance in breast cancer. Moreover, we highlight the recent clinical evidence regarding the usefulness of FAK inhibitors in the treatment of breast tumors.

Focal Adhesion Kinase in Ovarian Cancer: A Potential Therapeutic Target for Platinum and Taxane-Resistant Tumors

Focal adhesion kinase (FAK) is a non-receptor tyrosine kinase, which is an essential player in regulating cell migration, invasion, adhesion, proliferation, and survival. Its overexpression and activation have been identified in sixty-eight percent of epithelial ovarian cancer patients and this is significantly associated with higher tumor stage, metastasis, and shorter overall survival of these patients. Most recently, a new role has emerged for FAK in promoting resistance to taxane and platinum-based therapy in ovarian and other cancers. The development of resistance is a complex network of molecular processes that make the identification of a targetable biomarker in platinum and taxane-resistant ovarian cancer a major challenge. FAK overexpression upregulates ALDH and XIAP activity in platinum-resistant and increases CD44, YB1, and MDR-1 activity in taxaneresistant tumors. FAK is therefore now emerging as a prognostically significant candidate in this regard, with mounting evidence from recent successes in preclinical and clinical trials using small molecule FAK inhibitors. This review will summarize the significance and function of FAK in ovarian cancer, and its emerging role in chemotherapeutic resistance. We will discuss the current status of FAK inhibitors in ovarian cancers, their therapeutic competencies and limitations, and further propose that the combination of FAK inhibitors with platinum and taxane-based therapies could be an efficacious approach in chemotherapeutic resistant disease.

IQGAP1 control of centrosome function defines distinct variants of triple negative breast cancer

Triple negative breast cancer (TNBC) is a heterogenous and lethal disease that lacks diagnostic markers and therapeutic targets; as such common targets are highly sought after. IQGAP1 is a signaling scaffold implicated in TNBC, but its mechanism is unknown. Here we show that IQGAP1 localizes to the centrosome, interacts with and influences the expression level and localization of key centrosome proteins like BRCA1 and thereby impacts centrosome number. Genetic mutant analyses suggest that phosphorylation cycling of IQGAP1 is important to its subcellular localization and centrosome-nuclear shuttling of BRCA1; dysfunction of this process defines two alternate mechanisms associated with cell proliferation. TNBC cell lines and patient tumor tissues differentially phenocopy these mechanisms supporting clinical existence of molecularly distinct variants of TNBC defined by IQGAP1 pathways. These variants are defined, at least in part, by differential mis-localization or stabilization of IQGAP1-BRCA1 and rewiring of a novel Erk1/2-MNK1-JNK-Akt-β-catenin signaling signature. We discuss a model in which IQGAP1 modulates centrosome-nuclear crosstalk to regulate cell division and imparts on cancer. These findings have implications on cancer racial disparities and can provide molecular tools for classification of TNBC, presenting IQGAP1 as a common target amenable to personalized medicine.

Regulation of epidermal differentiation through KDF1-mediated deubiquitination of IKKα

Progenitor cells at the basal layer of skin epidermis play an essential role in maintaining tissue homeostasis and enhancing wound repair in skin. The proliferation, differentiation, and cell death of epidermal progenitor cells have to be delicately regulated, as deregulation of this process can lead to many skin diseases, including skin cancers. However, the underlying molecular mechanisms involved in skin homeostasis remain poorly defined. In this study, with quantitative proteomics approach, we identified an important interaction between KDF1 (keratinocyte differentiation factor 1) and IKKα (IκB kinase α) in differentiating skin keratinocytes. Ablation of either KDF1 or IKKα in mice leads to similar but striking abnormalities in skin development, particularly in skin epidermal differentiation. With biochemical and mouse genetics approach, we further demonstrate that the interaction of IKKα and KDF1 is essential for epidermal differentiation. To probe deeper into the mechanisms, we find that KDF1 associates with a deubiquitinating protease USP7 (ubiquitin-specific peptidase 7), and KDF1 can regulate skin differentiation through deubiquitination and stabilization of IKKα. Taken together, our study unravels an important molecular mechanism underlying epidermal differentiation and skin tissue homeostasis.

Wnt5b integrates Fak1a to mediate gastrulation cell movements via Rac1 and Cdc42

Focal adhesion kinase (FAK) mediates vital cellular pathways during development. Despite its necessity, how FAK regulates and integrates with other signals during early embryogenesis remains poorly understood. We found that the loss of Fak1a impaired epiboly, convergent extension and hypoblast cell migration in zebrafish embryos. We also observed a clear disturbance in cortical actin at the blastoderm margin and distribution of yolk syncytial nuclei. In addition, we investigated a possible link between Fak1a and a well-known gastrulation regulator, Wnt5b, and revealed that the overexpression of fak1a or wnt5b could cross-rescue convergence defects induced by a wnt5b or fak1a antisense morpholino (MO), respectively. Wnt5b and Fak1a were shown to converge in regulating Rac1 and Cdc42, which could synergistically rescue wnt5b and fak1a morphant phenotypes. Furthermore, we generated several alleles of fak1a mutants using CRISPR/Cas9, but those mutants only revealed mild gastrulation defects. However, injection of a subthreshold level of the wnt5b MO induced severe gastrulation defects in fak1a mutants, which suggested that the upregulated expression of wnt5b might complement the loss of Fak1a. Collectively, we demonstrated that a functional interaction between Wnt and FAK signalling mediates gastrulation cell movements via the possible regulation of Rac1 and Cdc42 and subsequent actin dynamics.

Targeting Src family kinase member Fyn by Saracatinib attenuated liver fibrosis in vitro and in vivo

Recent studies suggest that Src family kinase (SFK) plays important roles in systemic sclerosis and pulmonary fibrosis. However, how SFKs contributed to the pathogenesis of liver fibrosis remains largely unknown. Here, we investigated the role of Fyn, a member of SFK, in hepatic stellate cell (HSC) activation and liver fibrosis, and evaluated the anti-fibrotic effects of Saracatinib, a clinically proven safe Fyn inhibitor. Fyn activation was examined in human normal and fibrotic liver tissues. The roles of Fyn in HSC activation and liver fibrosis were evaluated in HSC cell lines by using Fyn siRNA and in Fyn knockout mice. The effects of Saracatinib on HSC activation and liver fibrosis were determined in primary HSCs and CCl₄ induced liver fibrosis model. We showed that the Fyn was activated in the liver of human fibrosis patients. TGF-β induced the activation of Fyn in HSC cell lines. Knockdown of Fyn significantly blocked HSC activation, proliferation, and migration. Fyn deficient mice were resistant to CCl₄ induced liver fibrosis. Saracatinib treatment abolished the activation of Fyn, downregulated the Fyn/FAK/N-WASP signaling in HSCs, and subsequently prevented the activation of HSCs. Saracatinib treatment significantly reduced the severity liver fibrosis induced by CCl₄ in mice. In conclusions, our findings supported the critical role of Fyn in HSC activation and development of liver fibrosis. Fyn could serve as a promising drug target for liver fibrosis treatment. Fyn inhibitor Saracatinib significantly inhibited HSC activation and attenuated liver fibrosis in mouse model.

Complementary functions for the Ran gradient during division

The Ran pathway has a well-described function in nucleocytoplasmic transport, where active Ran dissociates importin/karyopherin-bound cargo containing a nuclear localization signal (NLS) in the nucleus. As cells enter mitosis, the nuclear envelope breaks down and a gradient of active Ran forms where levels are highest near chromatin. This gradient plays a crucial role in regulating mitotic spindle assembly, where active Ran binds to and releases importins from NLS-containing spindle assembly factors. An emerging theme is that the Ran gradient also regulates the actomyosin cortex for processes including polar body extrusion during meiosis, and cytokinesis. For these events, active Ran could play an inhibitory role, where importin-binding may help promote or stabilize a conformation or interaction that favours the recruitment and function of cortical regulators. For either spindle assembly or cortical polarity, the gradient of active Ran determines the extent of importin-binding, the effects of which could vary for different proteins.

Concerted regulation of actin polymerization during constitutive secretion by cortactin and PKD2

Constitutive secretion from the trans-Golgi-network (TGN) is facilitated by a concerted regulation of vesicle biogenesis and fission processes. The protein kinase D family (PKD) has been previously described to enhance vesicle fission by modifying the lipid environment. PKD also phosphorylates the actin regulatory protein cortactin at S298 to impair synergistic actin polymerization. We here report additional functions for PKD2 (also known as PRKD2) and cortactin in the regulation of actin polymerization during the fission of transport carriers from the TGN. Phosphorylation of cortactin at S298 impairs the interaction between WIP (also known as WIPF1) and cortactin. WIP stabilizes the autoinhibited conformation of N-WASP (also known as WASL). This leads to an inhibition of synergistic Arp2/3-complex-dependent actin polymerization at the TGN. PKD2 activity at the TGN is controlled by active CDC42-GTP which directly activates N-WASP, inhibits PKD2 and shifts the balance to non-S298-phosphorylated cortactin, which can in turn sequester WIP from N-WASP. Consequently, synergistic actin polymerization at the TGN and constitutive secretion are enhanced.

Local Integrin Activation in Pancreatic β Cells Targets Insulin Secretion to the Vasculature

The extracellular matrix (ECM) critically affects β cell functions via integrin activation. But whether these ECM actions drive the spatial organization of β cells, as they do in epithelial cells, is unknown. Here, we show that within islets of Langerhans, focal adhesion activation in β cells occurs exclusively where they contact the capillary ECM (vascular face). In cultured β cells, 3D mapping shows enriched insulin granule fusion where the cells contact ECM-coated coverslips, which depends on β1 integrin receptor activation. Culture on micro-contact printed stripes of E-cadherin and fibronectin shows that β cell contact at the fibronectin stripe selectively activates focal adhesions and enriches exocytic machinery and insulin granule fusion. Culture of cells in high glucose, as a model of glucotoxicity, abolishes granule targeting. We conclude that local integrin activation targets insulin secretion to the islet capillaries. This mechanism might be important for islet function and may change in disease.

Passing the Vascular Barrier: Endothelial Signaling Processes Controlling Extravasation

A central function of the vascular endothelium is to serve as a barrier between the blood and the surrounding tissue of the body. At the same time, solutes and cells have to pass the endothelium to leave or to enter the bloodstream to maintain homeostasis. Under pathological conditions, for example, inflammation, permeability for fluid and cells is largely increased in the affected area, thereby facilitating host defense. To appropriately function as a regulated permeability filter, the endothelium uses various mechanisms to allow solutes and cells to pass the endothelial layer. These include transcellular and paracellular pathways of which the latter requires remodeling of intercellular junctions for its regulation. This review provides an overview on endothelial barrier regulation and focuses on the endothelial signaling mechanisms controlling the opening and closing of paracellular pathways for solutes and cells such as leukocytes and metastasizing tumor cells.

Focal adhesion kinase (FAK) activation by estrogens involves GPER in triple-negative breast cancer cells

BACKGROUND

Focal adhesion kinase (FAK) is a cytoplasmatic protein tyrosine kinase that associates with both integrins and growth factor receptors toward the adhesion, migration and invasion of cancer cells. The G-protein coupled estrogen receptor (GPER) has been involved in the stimulatory action of estrogens in breast tumor. In this study, we have investigated the engagement of FAK by GPER signaling in triple negative breast cancer (TNBC) cells.

METHODS

Publicly available large-scale database and patient data sets derived from "The Cancer Genome Atlas" (TCGA; www.cbioportal.org ) were used to assess FAK expression in TNBC, non-TNBC tumors and normal breast tissues. MDA-MB 231 and SUM159 TNBC cells were used as model system. The levels of phosphorylated FAK, other transduction mediators and target genes were detected by western blotting analysis. Focal adhesion assay was carried out in order to determine the focal adhesion points and the formation of focal adhesions (FAs). Luciferase assays were performed to evaluate the promoters activity of c-FOS, EGR1 and CTGF upon GPER activation. The mRNA expression of the aforementioned genes was measured by real time-PCR. Boyden chamber and wound healing assays were used in order to evaluate cell migration. The statistical analysis was performed by ANOVA.

RESULTS

We first determined by bioinformatic analysis that the mRNA expression levels of the gene encoding FAK, namely PTK2, is higher in TNBC respect to non-TNBC and normal breast tissues. Next, we found that estrogenic GPER signaling triggers Y397 FAK phosphorylation as well as the increase of focal adhesion points (FAs) in TNBC cells. Besides, we ascertained that GPER and FAK activation are involved in the STAT3 nuclear accumulation and gene expression changes. As biological counterpart, we show that FAK inhibition prevents the migration of TNBC cells upon GPER activation.

CONCLUSIONS

The present data provide novel insights regarding the action of FAK in TNBC. Moreover, on the basis of our findings estrogenic GPER signaling may be considered among the transduction mechanisms engaging FAK toward breast cancer progression.

Genome-edited skin epidermal stem cells protect mice from cocaine-seeking behaviour and cocaine overdose

Cocaine addiction is associated with compulsive drug-seeking, and exposure to the drug or to drug-associated cues leads to relapse, even after long periods of abstention. A variety of pharmacological targets and behavioral interventions have been explored to counteract cocaine addiction, but to date no market-approved medications for treating cocaine addiction or relapse exist, and effective interventions for acute emergencies resulting from cocaine overdose are lacking. We recently demonstrated that skin epidermal stem cells can be readily edited by using CRISPR (clustered regularly interspaced short palindromic repeats) and then transplanted back into the donor mice. Here, we show that the transplantation, into mice, of skin cells modified to express an enhanced form of butyrylcholinesterase, an enzyme that hydrolyzes cocaine, enables the long-term release of the enzyme and efficiently protects the mice from cocaine-seeking behavior and cocaine overdose. Cutaneous gene therapy through skin transplants that elicit drug elimination may offer a therapeutic option to address drug abuse.

Emerging regulators of vascular smooth muscle cell migration

Vascular smooth muscle cells (VSMCs) are the predominant cell type in the blood vessel wall and normally adopt a quiescent, contractile phenotype. VSMC migration is tightly controlled, however, disease associated changes in the soluble and insoluble environment promote VSMC migration. Classically, studies investigating VSMC migration have described the influence of soluble factors. Emerging data has highlighted the importance of insoluble factors, including extracellular matrix stiffness and porosity. In this review, we will recap on the important signalling pathways that regulate VSMC migration and reflect on the potential importance of emerging regulators of VSMC function.

Forkhead box O4 transcription factor in human neoplasms: Cannot afford to lose the novel suppressor

Forkhead box O4 (FOXO4), a member of FOXO family, has been highlighted as an essential transcriptional regulator in many diverse carcinomas. Accumulated studies have demonstrated that FOXO4 is downregulated and associated with tumorigenesis, invasiveness, and metastasis of most human cancer. FOXO4 alteration is also closely linked to the prognosis of various types of cancer. The aim of this review is to comprehensively present the clinical and pathological significance of FOXO4 in human cancer. Additionally, the potential clinical applications of future FOXO4 research are discussed. Collectively, the information reviewed here should increase the potential of FOXO4 as a therapeutic target for cancer.

Targeting Focal Adhesion Kinase Using Inhibitors of Protein-Protein Interactions

Focal adhesion kinase (FAK) is a cytoplasmic non-receptor protein tyrosine kinase that is overexpressed and activated in many human cancers. FAK transmits signals to a wide range of targets through both kinase-dependant and independent mechanism thereby playing essential roles in cell survival, proliferation, migration and invasion. In the past years, small molecules that inhibit FAK kinase function have been developed and show reduced cancer progression and metastasis in several preclinical models. Clinical trials have been conducted and these molecules display limited adverse effect in patients. FAK contain multiple functional domains and thus exhibit both important scaffolding functions. In this review, we describe the major FAK interactions relevant in cancer signalling and discuss how such knowledge provide rational for the development of Protein-Protein Interactions (PPI) inhibitors.

Regulating the migration of smooth muscle cells by a vertically distributed poly(2-hydroxyethyl methacrylate) gradient on polymer brushes covalently immobilized with RGD peptides

The gradient localization of biological cues is of paramount importance to guide directional migration of cells. In this study, poly(2-hydroxyethyl methacrylate-co-glycidyl methacrylate)-block- poly(2-hydroxyethyl methacrylate) (P(HEMA-co-GMA)-b-PHEMA) brushes with a uniform underneath P(HEMA-co-GMA) layer and a gradient thickness of PHEMA blocks were prepared by using surface-initiated atom-transfer radical polymerization and a dynamically controlled polymerization process. The polymer chains were subsequently functionalized with the cell-adhesive arginine-glycine-aspartic acid (RGD) peptides by reaction with the glycidyl groups, and their structures and properties were characterized by X-ray photoelectron spectrometry (XPS), quartz crystal microbalance with dissipation (QCM-D) and air contact angle. Adhesion and migration processes of smooth muscle cells (SMCs) were then studied. Compared with those on the sufficiently exposed RGD surface, the cell adhesion and mobility were well maintained when the RGD peptides were localized at 18.9 nm depth, whereas the adhesion, spreading and migration rate of SMCs were significantly impaired when the RGD peptides were localized at a depth of 38.4 nm. On the RGD depth gradient surface, the SMCs exhibited preferential orientation and enhanced directional migration toward the direction of reduced thickness of the second PHEMA brushes. Half of the cells were oriented within ± 30° to the x-axis direction, and 72% of the cells moved directionally at the optimal conditions. Cell adhesion strength, arrangement of cytoskeleton, and gene and protein expression levels of adhesion-related proteins were studied to corroborate the mechanisms, demonstrating that the cell mobility is regulated by the complex and synergetic intracellular signals resulted from the difference in surface properties.

STATEMENT OF SIGNIFICANCE

Cell migration is of paramount importance for the processes of tissue repair and regeneration. So far, the gradient localization of biological cues perpendicular to the substrate, which is the usual case for the biological signaling molecules to locate in ECM in vivo, has been scarcely studied, and has not been used to guide the directional migration of cells. In this study, we prepare a depth gradient of RGD peptides along the polymer chains, which is used to guide the directional migration of SMCs after a second hydrophilic bock is prepared in a gradient manner. For the first time the directional migration of SMCs is achieved under the guidance of a depth gradient of RGD ligands. The mechanisms of different cell migration abilities are further discussed based on the results of cell adhesion, cell adhesion force, cytoskeleton alignment and expression of relative proteins and genes. This work paves a new strategy by fabricating a gradient polymer brushes with immobilized bioactive molecules to dominate the directional cell migration, and elucidates the mechanisms underlining the biased migration along RGD depth localization gradients, shedding a light for the design of novel biomaterials to control and guide cell migration and invasion.

Rho kinase collaborates with p21-activated kinase to regulate actin polymerization and contraction in airway smooth muscle

KEY POINTS

The mechanisms by which Rho kinase (ROCK) regulates airway smooth muscle contraction were determined in tracheal smooth muscle tissues. ROCK may mediate smooth muscle contraction by inhibiting myosin regulatory light chain (RLC) phosphatase. ROCK can also regulate F-actin dynamics during cell migration, and actin polymerization is critical for airway smooth muscle contraction. Our results show that ROCK does not regulate airway smooth muscle contraction by inhibiting myosin RLC phosphatase or by stimulating myosin RLC phosphorylation. We find that ROCK regulates airway smooth muscle contraction by activating the serine-threonine kinase Pak, which mediates the activation of Cdc42 and neuronal Wiskott-Aldrich syndrome protein (N-WASp). N-WASP transmits signals from Cdc42 to the Arp2/3 complex for the nucleation of actin filaments. These results demonstrate a novel molecular function for ROCK in the regulation of Pak and Cdc42 activation that is critical for the processes of actin polymerization and contractility in airway smooth muscle.

ABSTRACT

Rho kinase (ROCK), a RhoA GTPase effector, can regulate the contraction of airway and other smooth muscle tissues. In some tissues, ROCK can inhibit myosin regulatory light chain (RLC) phosphatase, which increases the phosphorylation of myosin RLC and promotes smooth muscle contraction. ROCK can also regulate cell motility and migration by affecting F-actin dynamics. Actin polymerization is stimulated by contractile agonists in airway smooth muscle tissues and is required for contractile tension development in addition to myosin RLC phosphorylation. We investigated the mechanisms by which ROCK regulates the contractility of tracheal smooth muscle tissues by expressing a kinase-inactive mutant of ROCK, ROCK-K121G, in the tissues or by treating them with the ROCK inhibitor H-1152P. Our results show no role for ROCK in the regulation of non-muscle or smooth muscle myosin RLC phosphorylation during contractile stimulation in this tissue. We found that ROCK regulates airway smooth muscle contraction by mediating activation of p21-activated kinase (Pak), a serine-threonine kinase, to promote actin polymerization. Pak catalyses paxillin phosphorylation on Ser273 and coupling of the GIT1-βPIX-Pak signalling module to paxillin, which activates the guanine nucleotide exchange factor (GEF) activity of βPIX towards Cdc42. Cdc42 is required for the activation of neuronal Wiskott-Aldrich syndrome protein (N-WASp), which transmits signals from Cdc42 to the Arp2/3 complex for the nucleation of actin filaments. Our results demonstrate a novel molecular function for ROCK in the regulation of Pak and Cdc42 activation that is critical for the processes of actin polymerization and contractility in airway smooth muscle.

Engineered Epidermal Progenitor Cells Can Correct Diet-Induced Obesity and Diabetes

Somatic gene therapy is a promising approach for treating otherwise terminal or debilitating diseases. The human skin is a promising conduit for genetic engineering, as it is the largest and most accessible organ, epidermal autografts and tissue-engineered skin equivalents have been successfully deployed in clinical applications, and skin epidermal stem/progenitor cells for generating such grafts are easy to obtain and expand in vitro. Here, we develop skin grafts from mouse and human epidermal progenitors that were engineered by CRISPR-mediated genome editing to controllably release GLP-1 (glucagon-like peptide 1), a critical incretin that regulates blood glucose homeostasis. GLP-1 induction from engineered mouse cells grafted onto immunocompetent hosts increased insulin secretion and reversed high-fat-diet-induced weight gain and insulin resistance. Taken together, these results highlight the clinical potential of developing long-lasting, safe, and versatile gene therapy approaches based on engineering epidermal progenitor cells.

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.

CML/CD36 accelerates atherosclerotic progression via inhibiting foam cell migration

Among the various complications of type 2 diabetes mellitus, atherosclerosis causes the highest disability and morbidity. A multitude of macrophage-derived foam cells are retained in atherosclerotic plaques resulting not only from recruitment of monocytes into lesions but also from a reduced rate of macrophage migration from lesions. Nε-carboxymethyl-Lysine (CML), an advanced glycation end product, is responsible for most complications of diabetes. This study was designed to investigate the mechanism of CML/CD36 accelerating atherosclerotic progression via inhibiting foam cell migration. In vivo study and in vitro study were performed. For the in vivo investigation, CML/CD36 accelerated atherosclerotic progression via promoting the accumulation of macrophage-derived foam cells in aorta and inhibited macrophage-derived foam cells in aorta migrating to the para-aorta lymph node of diabetic apoE^-/- mice. For the in vitro investigation, CML/CD36 inhibited RAW264.7-derived foam cell migration through NOX-derived ROS, FAK phosphorylation, Arp2/3 complex activation and F-actin polymerization. Thus, we concluded that CML/CD36 inhibited foam cells of plaque migrating to para-aorta lymph nodes, accelerating atherosclerotic progression. The corresponding mechanism may be via free cholesterol, ROS generation, p-FAK, Arp2/3, F-actin polymerization.

Autophagy gene FIP200 in neural progenitors non-cell autonomously controls differentiation by regulating microglia

Recent studies have shown important roles for autophagy genes in the regulation of different tissue stem cells, including neural stem/progenitor cells (NSCs). However, little is known about whether autophagy can regulate NSCs through cell-extrinsic mechanisms. Here, we show that deletion of an essential autophagy gene, FIP200, in NSCs increased expression of Ccl5 and Cxcl10 in a p53-independent manner, mediating increased infiltration of microglia into the subventricular zone of both FIP200hGFAP conditional knockout (cKO) and FIP200;p53hGFAP 2cKO mice. The microglia exhibited an activated M1 phenotype consistent with their potential to inhibit differentiation of FIP200-null NSCs. Blocking either microglia infiltration or activation rescued the deficient differentiation of FIP200-null NSCs from FIP200;p53hGFAP 2cKO mice. Lastly, we showed that increased chemokine expression in FIP200-null NSCs was induced by abnormal p62 aggregate formation and activation of NF-κB signaling. Our results suggest that autophagy plays a crucial role in regulating neurogenesis and restricting local immune response in postnatal NSCs through non-cell autonomous mechanisms.

ACF7 regulates inflammatory colitis and intestinal wound response by orchestrating tight junction dynamics

In the intestinal epithelium, the aberrant regulation of cell/cell junctions leads to intestinal barrier defects, which may promote the onset and enhance the severity of inflammatory bowel disease (IBD). However, it remains unclear how the coordinated behaviour of cytoskeletal network may contribute to cell junctional dynamics. In this report, we identified ACF7, a crosslinker of microtubules and F-actin, as an essential player in this process. Loss of ACF7 leads to aberrant microtubule organization, tight junction stabilization and impaired wound closure in vitro. With the mouse genetics approach, we show that ablation of ACF7 inhibits intestinal wound healing and greatly increases susceptibility to experimental colitis in mice. ACF7 level is also correlated with development and progression of ulcerative colitis (UC) in human patients. Together, our results reveal an important molecular mechanism whereby coordinated cytoskeletal dynamics contributes to cell adhesion regulation during intestinal wound repair and the development of IBD.

The cytoskeleton plays a key role in cell/cell junction formation, but how the coordinated behaviour of the cytoskeleton contributes is not known. Here the authors show that actin-microtubule crosslinker ACF7 plays a key role in tight junction stabilization and wound healing in intestinal epithelium.

Phosphorylation of Pkp1 by RIPK4 regulates epidermal differentiation and skin tumorigenesis

Tissue homeostasis of skin is sustained by epidermal progenitor cells localized within the basal layer of the skin epithelium. Post-translational modification of the proteome, such as protein phosphorylation, plays a fundamental role in the regulation of stemness and differentiation of somatic stem cells. However, it remains unclear how phosphoproteomic changes occur and contribute to epidermal differentiation. In this study, we survey the epidermal cell differentiation in a systematic manner by combining quantitative phosphoproteomics with mammalian kinome cDNA library screen. This approach identified a key signaling event, phosphorylation of a desmosome component, PKP1 (plakophilin-1) by RIPK4 (receptor-interacting serine-threonine kinase 4) during epidermal differentiation. With genome-editing and mouse genetics approach, we show that loss of function of either Pkp1 or Ripk4 impairs skin differentiation and enhances epidermal carcinogenesis in vivo Phosphorylation of PKP1's N-terminal domain by RIPK4 is essential for their role in epidermal differentiation. Taken together, our study presents a global view of phosphoproteomic changes that occur during epidermal differentiation, and identifies RIPK-PKP1 signaling as novel axis involved in skin stratification and tumorigenesis.

Thyroid Hormone Controls Breast Cancer Cell Movement via Integrin αV/β3/SRC/FAK/PI3-Kinases

Thyroid hormones (TH) play a fundamental role in diverse processes, including cellular movement. Cell migration requires the integration of events that induce changes in cell structure towards the direction of migration. These actions are driven by actin remodeling and stabilized by the development of adhesion sites to extracellular matrix via transmembrane receptors linked to the actin cytoskeleton. Focal adhesion kinase (FAK) is a non-receptor tyrosine kinase that promotes cell migration and invasion through the control of focal adhesion turnover. In this work, we demonstrate that the thyroid hormone triiodothyronine (T3) regulates actin remodeling and cell movement in breast cancer T-47D cells through the recruitment of FAK. T3 controls FAK phosphorylation and translocation at sites where focal adhesion complexes are assembled. This process is triggered via rapid signaling to integrin αV/β3, Src, phosphatidylinositol 3-OH kinase (PI3K), and FAK. In addition, we established a cellular model with different concentration of T3 levels: normal, absence, and excess in T-47D breast cancer cells. We found that the expression of Src, FAK, and PI3K remained at normal levels in the excess of T3 model, while it was significantly reduced in the absence model. In conclusion, these results suggest a novel role for T3 as an important modulator of cell migration, providing a starting point for the development of new therapeutic strategies for breast cancer treatment.

Addressing the Functional Determinants of FAK during Ciliogenesis in Multiciliated Cells

We previously identified focal adhesion kinase (FAK) as an important regulator of ciliogenesis in multiciliated cells. FAK and other focal adhesion (FA) proteins associate with the basal bodies and their striated rootlets and form complexes named ciliary adhesions (CAs). CAs display similarities with FAs but are established in an integrin independent fashion and are responsible for anchoring basal bodies to the actin cytoskeleton during ciliogenesis as well as in mature multiciliated cells. FAK down-regulation leads to aberrant ciliogenesis due to impaired association between the basal bodies and the actin cytoskeleton, suggesting that FAK is an important regulator of the CA complex. However, the mechanism through which FAK functions in the complex is not clear, and in this study we examined the role of this protein in both ciliogenesis and ciliary function. We show that localization of FAK at CAs depends on interactions taking place at the amino-terminal (FERM) and carboxyl-terminal (FAT) domains and that both domains are required for proper ciliogenesis and ciliary function. Furthermore, we show that an interaction with another CA protein, paxillin, is essential for correct localization of FAK in multiciliated cells. This interaction is indispensable for both ciliogenesis and ciliary function. Finally, we provide evidence that despite the fact that FAK is in the active, open conformation at CAs, its kinase activity is dispensable for ciliogenesis and ciliary function revealing that FAK plays a scaffolding role in multiciliated cells. Overall these data show that the role of FAK at CAs displays similarities but also important differences compared with its role at FAs.

In vivo epidermal migration requires focal adhesion targeting of ACF7

Turnover of focal adhesions allows cell retraction, which is essential for cell migration. The mammalian spectraplakin protein, ACF7 (Actin-Crosslinking Factor 7), promotes focal adhesion dynamics by targeting of microtubule plus ends towards focal adhesions. However, it remains unclear how the activity of ACF7 is regulated spatiotemporally to achieve focal adhesion-specific guidance of microtubule. To explore the potential mechanisms, we resolve the crystal structure of ACF7’s NT (amino-terminal) domain, which mediates F-actin interactions. Structural analysis leads to identification of a key tyrosine residue at the calponin homology (CH) domain of ACF7, whose phosphorylation by Src/FAK (focal adhesion kinase) complex is essential for F-actin binding of ACF7. Using skin epidermis as a model system, we further demonstrate that the phosphorylation of ACF7 plays an indispensable role in focal adhesion dynamics and epidermal migration in vitro and in vivo. Together, our findings provide critical insights into the molecular mechanisms underlying coordinated cytoskeletal dynamics during cell movement.

The spectraplakin protein ACF7 binds to actin at focal adhesions and targets microtubule plus ends to focal adhesions, promoting their disassembly. Here the authors reveal that ACF7 is phosphorylated by Src/FAK, and this regulates actin binding and focal adhesion dynamics in vitro and in vivo.

Wiskott-Aldrich syndrome proteins in the nucleus: aWASH with possibilities

Actin and proteins that regulate its dynamics or interactions have well-established roles in the cytoplasm where they function as key components of the cytoskeleton to control diverse processes, including cellular infrastructure, cellular motility, cell signaling, and vesicle transport. Recent work has also uncovered roles for actin and its regulatory proteins in the nucleus, primarily in mechanisms governing gene expression. The Wiskott Aldrich Syndrome (WAS) family of proteins, comprising the WASP/N-WASP, SCAR/WAVE, WHAMM/JMY/WHAMY, and WASH subfamilies, function in the cytoplasm where they activate the Arp2/3 complex to form branched actin filaments. WAS proteins are present in the nucleus and have been implicated as transcriptional regulators. We found that Drosophila Wash, in addition to transcriptional effects, is involved in global nuclear architecture. Here we summarize the regulation and function of nuclear WAS proteins, and highlight how our work with Wash expands the possibilities for the functions of these proteins in the nucleus.

The Regulation of Cellular Responses to Mechanical Cues by Rho GTPases

The Rho GTPases regulate many cellular signaling cascades that modulate cell motility, migration, morphology and cell division. A large body of work has now delineated the biochemical cues and pathways, which stimulate the GTPases and their downstream effectors. However, cells also respond exquisitely to biophysical and mechanical cues such as stiffness and topography of the extracellular matrix that profoundly influence cell migration, proliferation and differentiation. As these cellular responses are mediated by the actin cytoskeleton, an involvement of Rho GTPases in the transduction of such cues is not unexpected. In this review, we discuss an emerging role of Rho GTPase proteins in the regulation of the responses elicited by biophysical and mechanical stimuli.

Neuronal Wiskott-Aldrich syndrome protein regulates TGF-β1-mediated lung vascular permeability

TGF-β1 induces an increase in paracellular permeability and actin stress fiber formation in lung microvascular endothelial and alveolar epithelial cells via small Rho GTPase. The molecular mechanism involved is not fully understood. Neuronal Wiskott-Aldrich syndrome protein (N-WASP) has an essential role in actin structure dynamics. We hypothesized that N-WASP plays a critical role in these TGF-β1-induced responses. In these cell monolayers, we demonstrated that N-WASP down-regulation by short hairpin RNA prevented TGF-β1-mediated disruption of the cortical actin structure, actin stress filament formation, and increased permeability. Furthermore, N-WASP down-regulation blocked TGF-β1 activation mediated by IL-1β in alveolar epithelial cells, which requires actin stress fiber formation. Control short hairpin RNA had no effect on these TGF-β1-induced responses. TGF-β1-induced phosphorylation of Y256 of N-WASP via activation of small Rho GTPase and focal adhesion kinase mediates TGF-β1-induced paracellular permeability and actin cytoskeleton dynamics. In vivo, compared with controls, N-WASP down-regulation increases survival and prevents lung edema in mice induced by bleomycin exposure-a lung injury model in which TGF-β1 plays a critical role. Our data indicate that N-WASP plays a crucial role in the development of TGF-β1-mediated acute lung injury by promoting pulmonary edema via regulation of actin cytoskeleton dynamics.-Wagener, B. M., Hu, M., Zheng, A., Zhao, X., Che, P., Brandon, A., Anjum, N., Snapper, S., Creighton, J., Guan, J.-L., Han, Q., Cai, G.-Q., Han, X., Pittet, J.-F., Ding, Q. Neuronal Wiskott-Aldrich syndrome protein regulates TGF-β1-mediated lung vascular permeability.

The FAK-Arp2/3 interaction promotes leading edge advance and haptosensing by coupling nascent adhesions to lamellipodia actin

Focal adhesion kinase (FAK) is an important regulator of focal adhesion dynamics during cell migration. Distinct functions of FAK—kinase activation and Arp2/3 binding—enable cells to mechanosense or haptotax during spreading and migration.

Cell migration is initiated in response to biochemical or physical cues in the environment that promote actin-mediated lamellipodial protrusion followed by the formation of nascent integrin adhesions (NAs) within the protrusion to drive leading edge advance. Although FAK is known to be required for cell migration through effects on focal adhesions, its role in NA formation and lamellipodial dynamics is unclear. Live-cell microscopy of FAK^−/− cells with expression of phosphorylation deficient or a FERM-domain mutant deficient in Arp2/3 binding revealed a requirement for FAK in promoting the dense formation, transient stabilization, and timely turnover of NA within lamellipodia to couple actin-driven protrusion to adhesion and advance of the leading edge. Phosphorylation on Y397 of FAK promotes dense NA formation but is dispensable for transient NA stabilization and leading edge advance. In contrast, transient NA stabilization and advance of the cell edge requires FAK–Arp2/3 interaction, which promotes Arp2/3 localization to NA and reduces FAK activity. Haptosensing of extracellular matrix (ECM) concentration during migration requires the interaction between FAK and Arp2/3, whereas FAK phosphorylation modulates mechanosensing of ECM stiffness during spreading. Taken together, our results show that mechanistically separable functions of FAK in NA are required for cells to distinguish distinct properties of their environment during migration.

Role of N-WASP in Endothelial Monolayer Formation and Integrity

Endothelial cells (ECs) form a monolayer that serves as a barrier between the blood and the underlying tissue. ECs tightly regulate their cell-cell junctions, controlling the passage of soluble materials and immune cells across the monolayer barrier. We studied the role of N-WASP, a key regulator of Arp2/3 complex and actin assembly, in EC monolayers. We report that N-WASP regulates endothelial monolayer integrity by affecting the organization of cell junctions. Depletion of N-WASP resulted in an increase in transendothelial electrical resistance, a measure of monolayer integrity. N-WASP depletion increased the width of cell-cell junctions and altered the organization of F-actin and VE-cadherin at junctions. N-WASP was not present at cell-cell junctions in monolayers under resting conditions, but it was recruited following treatment with sphingosine-1-phosphate. Taken together, our results reveal a novel role for N-WASP in remodeling EC junctions, which is critical for monolayer integrity and function.

Dynamics between actin and the VE-cadherin/catenin complex: novel aspects of the ARP2/3 complex in regulation of endothelial junctions

Endothelial adherens junctions are critical for physiological and pathological processes such as differentiation, maintenance of entire monolayer integrity, and the remodeling. The endothelial-specific VE-cadherin/catenin complex provides the backbone of adherens junctions and acts in close interaction with actin filaments and actin/myosin-mediated contractility to fulfill the junction demands. The functional connection between the cadherin/catenin complex and actin filaments might be either directly through ?-catenins, or indirectly e.g., via linker proteins such as vinculin, p120ctn, ?-actinin, or EPLIN. However, both junction integrity and dynamic remodeling have to be contemporarily coordinated. The actin-related protein complex ARP2/3 and its activating molecules, such as N-WASP and WAVE, have been shown to regulate the lammellipodia-mediated formation of cell junctions in both epithelium and endothelium. Recent reports now demonstrate a novel aspect of the ARP2/3 complex and the nucleating-promoting factors in the maintenance of endothelial barrier function and junction remodeling of established endothelial cell junctions. Those mechanisms open novel possibilities; not only in fulfilling physiological demands but obtained information may be of critical importance in pathologies such as wound healing, angiogenesis, inflammation, and cell diapedesis.

Ultraviolet B Inhibits Skin Wound Healing by Affecting Focal Adhesion Dynamics

As the most important interface between human body and external environment, skin acts as an essential barrier preventing various environmental damages, among which DNA-damaging UV radiation from the sun remains the major environmental risk factor causing various skin diseases. It has been well documented that wavelengths in the ultraviolet B (UVB) radiation range (290-320 nm) of the solar spectrum can be absorbed by skin and lead to cutaneous injury and various other deleterious effects. During process such as wound healing, the orchestrated movement of cells in a particular direction is essential and highly regulated, integrating signals controlling adhesion, polarity and the cytoskeleton. Cell adhesion and migration are modulated through both of actin and microtubule cytoskeletons. However, little was known about how UVB affects skin wound healing and migration of epidermal keratinocytes. Here, we demonstrate that UVB can delay the wound healing progress in vivo with a murine model of full-thickness skin wound. In addition, UVB significantly inhibited keratinocyte motility by altering focal adhesion turnover and cytoskeletal dynamics. Our results provide new insights into the etiology of UVB exposure-induced skin damages.

Targeting FAK scaffold functions inhibits human renal cell carcinoma growth

Human conventional renal cell carcinoma (CCC) remains resistant to current therapies. Focal Adhesion Kinase (FAK) is upregulated in many epithelial tumors and clearly implicated in nearly all facets of cancer. However, only few reports have assessed whether FAK may be associated with renal tumorigenesis. In this study, we investigated the potential role of FAK in the growth of human CCC using a panel of CCC cell lines expressing or not the von Hippel-Lindau (VHL) tumor suppressor gene as well as normal/tumoral renal tissue pairs. FAK was found constitutively expressed in human CCC both in culture cells and freshly harvested tumors obtained from patients. We showed that CCC cell growth was dramatically reduced in FAK-depleted cells or after FAK inhibition with various inhibitors and this effect was obtained through inhibition of cell proliferation and induction of cell apoptosis. Additionally, our results indicated that FAK knockdown decreased CCC cell migration and invasion. More importantly, depletion or pharmacological inhibition of FAK substantially inhibited tumor growth in vivo. Interestingly, investigations of the molecular mechanism revealed loss of FAK phosphorylation during renal tumorigenesis impacting multiple signaling pathways. Taken together, our findings reveal a previously uncharacterized role of FAK in CCC whereby FAK exerts oncogenic properties through a non canonical signaling pathway involving its scaffolding kinase-independent properties. Therefore, targeting the FAK scaffold may represent a promising approach for developing innovative and highly specific therapies in human CCC.

Emerging roles of focal adhesion kinase in cancer

Focal adhesion kinase (FAK) is a cytoplasmic nonreceptor tyrosine kinase that enables activation by growth factor receptors or integrins in various types of human cancers. The kinase-dependent and kinase-independent scaffolding functions of FAK modulate the authentic signaling and fundamental functions not only in cancer cells but also in tumor microenvironment to facilitate cancer progression and metastasis. The overexpression and activation of FAK are usually investigated in primary or metastatic cancers and correlated with the poor clinical outcome, highlighting FAK as a potential prognostic marker and anticancer target. Small molecule inhibitors targeting FAK kinase activity or FAK-scaffolding functions impair cancer development in preclinical or clinical trials. In this review, we give an overview for FAK signaling in cancer cells as well as tumor microenvironment that provides new strategies for the invention of cancer development and malignancy.

Abnormal Rho-associated kinase activity contributes to the dysfunctional myogenic response of cerebral arteries in type 2 diabetes

The structural and functional integrity of the brain, and therefore, cognition, are critically dependent on the appropriate control of blood flow within the cerebral circulation. Inadequate flow leads to ischemia, whereas excessive flow causes small vessel rupture and (or) blood-brain-barrier disruption. Cerebral blood flow is controlled through the interplay of several physiological mechanisms that regulate the contractile state of vascular smooth muscle cells (VSMCs) within the walls of cerebral resistance arteries and arterioles. The myogenic response of cerebral VSMCs is a key mechanism that is responsible for maintaining constant blood flow during variations in systemic pressure, i.e., flow autoregulation. Inappropriate myogenic control of cerebral blood flow is associated with, and prognostic of, neurological deterioration and poor outcome in patients with several conditions, including type 2 diabetes. Here, we review recent advances in our understanding of the role of inappropriate Rho-associated kinase activity as a cause of impaired myogenic regulation of cerebral arterial diameter in type 2 diabetes.

FAK signaling in human cancer as a target for therapeutics

Focal adhesion kinase (FAK) is a key regulator of growth factor receptor- and integrin-mediated signals, governing fundamental processes in normal and cancer cells through its kinase activity and scaffolding function. Increased FAK expression and activity occurs in primary and metastatic cancers of many tissue origins, and is often associated with poor clinical outcome, highlighting FAK as a potential determinant of tumor development and metastasis. Indeed, data from cell culture and animal models of cancer provide strong lines of evidence that FAK promotes malignancy by regulating tumorigenic and metastatic potential through highly-coordinated signaling networks that orchestrate a diverse range of cellular processes, such as cell survival, proliferation, migration, invasion, epithelial-mesenchymal transition, angiogenesis and regulation of cancer stem cell activities. Such an integral role in governing malignant characteristics indicates that FAK represents a potential target for cancer therapeutics. While pharmacologic targeting of FAK scaffold function is still at an early stage of development, a number of small molecule-based FAK tyrosine kinase inhibitors are currently undergoing pre-clinical and clinical testing. In particular, PF-00562271, VS-4718 and VS-6063 show promising clinical activities in patients with selected solid cancers. Clinical testing of rationally designed FAK-targeting agents with implementation of predictive response biomarkers, such as merlin deficiency for VS-4718 in mesothelioma, may help improve clinical outcome for cancer patients. In this article, we have reviewed the current knowledge regarding FAK signaling in human cancer, and recent developments in the generation and clinical application of FAK-targeting pharmacologic agents.

Focal adhesion kinase (FAK) perspectives in mechanobiology: implications for cell behaviour

Mechanobiology is a scientific interface discipline emerging from engineering and biology. With regard to tissue-regenerative cell-based strategies, mechanobiological concepts, including biomechanics as a target for cell and human mesenchymal stem cell behaviour, are on the march. Based on the periodontium as a paradigm, this mini-review discusses the key role of focal-adhesion kinase (FAK) in mechanobiology, since it is involved in mediating the transformation of environmental biomechanical signals into cell behavioural responses via mechanotransducing signalling cascades. These processes enable cells to adjust quickly to environmental cues, whereas adjustment itself relies on the specific intramolecular phosphorylation of FAK tyrosine residues and the multiple interactions of FAK with distinct partners. Furthermore, interaction-triggered mechanotransducing pathways govern the dynamics of focal adhesion sites and cell behaviour. Facets of behaviour not only include cell spreading and motility, but also proliferation, differentiation and apoptosis. In translational terms, identified and characterized biomechanical parameters can be incorporated into innovative concepts of cell- and tissue-tailored clinically applied biomaterials controlling cell behaviour as desired.

Podocalyxin-like 1 promotes invadopodia formation and metastasis through activation of Rac1/Cdc42/cortactin signaling in breast cancer cells

Metastatic disease is the leading cause of cancer mortality. Identifying biomarkers and regulatory mechanisms is important toward developing diagnostic and therapeutic tools against metastatic cancer. In this study, we demonstrated that podocalyxin-like 1 (PODXL) is overexpressed in breast tumor cells and increased in lymph node metastatic cancer. Mechanistically, we found that the expression of PODXL was associated with cell motility and invasiveness. Suppression of PODXL in MDA-MB-231 cells reduced lamellipodia formation and focal adhesion kinase (FAK) and paxillin phosphorylation. PODXL knockdown reduced the formation of invadopodia, such as inhibiting the colocalization of F-actin with cortactin and suppressing phosphorylation of cortactin and neural Wiskott-Aldrich syndrome protein. Conversely, overexpression of PODXL in MCF7 cells induced F-actin/cortactin colocalization and enhanced invadopodia formation and activation. Invadopodia activity and tumor invasion in PODXL-knockdown cells are similar to that in cortactin-knockdown cells. We further found that the DTHL motif in PODXL is crucial for regulating cortactin phosphorylation and Rac1/Cdc42 activation. Inhibition of Rac1/Cdc42 impeded PODXL-mediated cortactin activation and FAK and paxillin phosphorylation. Moreover, inhibition of PODXL in MDA-MB-231 cells significantly suppressed tumor colonization in the lungs and distant metastases, similar to those in cortactin-knockdown cells. These findings show that overexpression of PODXL enhanced invadopodia formation and tumor metastasis by inducing Rac1/Cdc42/cortactin signaling network.