Reduced cell motility and enhanced focal adhesion contact formation in cells from FAK-deficient mice

Vascular growth responses to chronic arterial occlusion are unaffected by myeloid specific focal adhesion kinase (FAK) deletion

Arteriogenesis, or the lumenal expansion of pre-existing arterioles in the presence of an upstream occlusion, is a fundamental vascular growth response. Though alterations in shear stress stimulate arteriogenesis, the migration of monocytes into the perivascular space surrounding collateral arteries and their differentiation into macrophages is critical for this vascular growth response to occur. Focal adhesion kinase’s (FAK) role in regulating cell migration has recently been expanded to primary macrophages. We therefore investigated the effect of the myeloid-specific conditional deletion of FAK on vascular remodeling in the mouse femoral arterial ligation (FAL) model. Using laser Doppler perfusion imaging, whole mount imaging of vascular casted gracilis muscles, and immunostaining for CD31 in gastrocnemius muscles cross-sections, we found that there were no statistical differences in perfusion recovery, arteriogenesis, or angiogenesis 28 days after FAL. We therefore sought to determine FAK expression in different myeloid cell populations. We found that FAK is expressed at equally low levels in Ly6C^hi and Ly6C^lo blood monocytes, however expression is increased over 2-fold in bone marrow derived macrophages. Ultimately, these results suggest that FAK is not required for monocyte migration to the perivascular space and that vascular remodeling following arterial occlusion occurs independently of myeloid specific FAK.

The Interaction between Cancer Stem Cell Marker CD133 and Src Protein Promotes Focal Adhesion Kinase (FAK) Phosphorylation and Cell Migration

CD133, a widely known cancer stem cell marker, has been proved to promote tumor metastasis. However, the mechanism by which CD133 regulates metastasis remains largely unknown. Here, we report that CD133 knockdown inhibits cancer cell migration, and CD133 overexpression promotes cell migration. CD133 expression is beneficial to activate the Src-focal adhesion kinase (FAK) signaling pathway. Further studies show that CD133 could interact with Src, and the region between amino acids 845 and 857 in the CD133 C-terminal domain is indispensable for its interaction with Src. The interaction activates Src to phosphorylate its substrate FAK and to promote cell migration. Likewise, a Src binding-deficient CD133 mutant loses the abilities to increase Src and FAK phosphorylation and to promote cell migration. Inhibition of Src activity by PP2, a known Src activity inhibitor, could block the activation of FAK phosphorylation and cell migration induced by CD133. In summary, our data suggest that activation of FAK by the interaction between CD133 and Src promotes cell migration, providing clues to understand the migratory mechanism of CD133(+) tumor cells.

CAP1 (Cyclase-Associated Protein 1) Exerts Distinct Functions in the Proliferation and Metastatic Potential of Breast Cancer Cells Mediated by ERK

The actin-regulating protein CAP1 is implicated in the invasiveness of human cancers. However, the exact role remains elusive and controversial given lines of conflicting evidence. Moreover, a potential role in the proliferative transformation has largely been overlooked. Further establishing the role and dissecting underlying mechanisms are imperative before targeting CAP1 can become a possibility for cancer treatment. Here we report our findings that CAP1 exerts cell type-dependent functions in the invasiveness of breast cancer cells. Depletion of CAP1 in the metastatic MDA-MB-231 and BT-549 cancer cells stimulated the metastatic potential while it actually inhibited it in the non-metastatic MCF-7 cancer cells or in normal cells. Moreover, we demonstrate functions for CAP1 in cancer cell proliferation and anchorage-independent growth, again in a cell context-dependent manner. Importantly, we identify pivotal roles for the ERK-centered signaling in mediating both CAP1 functions. Phosphor mutants of CAP1 at the S307/S309 regulatory site had compromised rescue effects for both the invasiveness and proliferation in CAP1-knockdown cells, suggesting that CAP1 likely mediates upstream cell signals to control both functions. These novel mechanistic insights may ultimately open up avenues for strategies targeting CAP1 in the treatment of breast cancer, tailored for specific types of the highly diverse disease.

Autophagy Promotes Focal Adhesion Disassembly and Cell Motility of Metastatic Tumor Cells through the Direct Interaction of Paxillin with LC3

Autophagy is a conserved catabolic process that plays a housekeeping role in eliminating protein aggregates and organelles and is activated during nutrient deprivation to generate metabolites and energy. Autophagy plays a significant role in tumorigenesis, although opposing context-dependent functions of autophagy in cancer have complicated efforts to target autophagy for therapeutic purposes. We demonstrate that autophagy inhibition reduces tumor cell migration and invasion in vitro and attenuates metastasis in vivo. Numerous abnormally large focal adhesions (FAs) accumulate in autophagy-deficient tumor cells, reflecting a role for autophagy in FA disassembly through targeted degradation of paxillin. We demonstrate that paxillin interacts with processed LC3 through a conserved LIR motif in the amino-terminal end of paxillin and that this interaction is regulated by oncogenic SRC activity. Together, these data establish a function for autophagy in FA turnover, tumor cell motility, and metastasis.

Deguelin inhibits vasculogenic function of endothelial progenitor cells in tumor progression and metastasis via suppression of focal adhesion

Deguelin is a nature-derived chemopreventive drug. Endothelial progenitor cells (EPCs) are bone-marrow (BM)-derived key components to induce new blood vessels in early tumorigenesis and metastasis. Here we determined whether deguelin inhibits EPC function in vitro and in vivo at doses not affecting cancer cell apoptosis. Deguelin significantly reduced the number of EPC colony forming units of BM-derived c-kit+/sca-1+ mononuclear cells (MNCs), proliferation, migration, and adhesion to endothelial cell monolayers, and suppressed incorporation of EPC into tube-like vessel networks when co-cultured with endothelial cells. Deguelin caused cell cycle arrest at G1 without induction of apoptosis in EPC. In a mouse tumor xenograft model, tumor growth, lung metastasis and tumor-induced circulating EPCs were supressed by deguelin treatment (2 mg/kg). In mice tranplanted with GFP-expressing BM-MNCs, deguelin reduced the co-localization of CD31 and GFP, suggesting suppression of BM-derived EPC incoporation into tumor vessels. Interestingly, focal adhesion kinase (FAK)-integrin-linked kinase (ILK) activation and actin polymerization were repressed by deguelin. Decreased number of focal adhesions and a depolarized morphology was found in deguelin-treated EPCs. Taken together, our results suggest that the deguelin inhibits tumorigenesis and metastasis via EPC suppression and that suppression of focal adhesion by FAK-integrin-ILK-dependent actin remodeling is a key underlying molecular mechanism.

FAK, talin and PIPKIγ regulate endocytosed integrin activation to polarize focal adhesion assembly

Integrin endocytic recycling is critical for cell migration, yet how recycled integrins assemble into new adhesions is unclear. By synchronizing endocytic disassembly of focal adhesions (FAs), we find that recycled integrins reassemble FAs coincident with their return to the cell surface and dependent on Rab5 and Rab11. Unexpectedly, endocytosed integrins remained in an active but unliganded state in endosomes. FAK and Src kinases co-localized with endocytosed integrin and were critical for FA reassembly by regulating integrin activation and recycling, respectively. FAK sustained the active integrin conformation by maintaining talin association with Rab11 endosomes in a type I phosphatidylinositol phosphate kinase (PIPKIγ)-dependent manner. In migrating cells, endocytosed integrins reassembled FAs polarized towards the leading edge, and this polarization required FAK. These studies identify unanticipated roles for FA proteins in maintaining endocytosed integrin in an active conformation. We propose that the conformational memory of endocytosed integrin enhances polarized reassembly of FAs to enable directional cell migration.

New partners and phosphorylation sites of focal adhesion kinase identified by mass spectrometry

The regulation of focal adhesion kinase (FAK) involves phosphorylation and multiple interactions with other signaling proteins. Some of these pathways are relevant for nervous system functions such as branching, axonal guidance, and plasticity. In this study, we screened mouse brain to identify FAK-interactive proteins and phosphorylatable residues as a first step to address the neuronal functions of this kinase. Using mass spectrometry analysis, we identified new phosphorylated sites (Thr 952, Thr 1048, and Ser 1049), which lie in the FAT domain; and putative new partners for FAK, which include cytoskeletal proteins such as drebrin and MAP 6, adhesion regulators such as neurabin-2 and plakophilin 1, and synapse-associated proteins such as SynGAP and a NMDA receptor subunit. Our findings support the participation of brain-localized FAK in neuronal plasticity.

Human fibroblasts display a differential focal adhesion phenotype relative to chimpanzee

It has been documented that there are differences in disease susceptibilities between humans and non-human primates. We investigate one of these differences in fibroblasts to examine differences in cellular adhesion between humans and chimpanzees using microscopy and gene expression and have found significant differences in both datasets. These results suggest that human and chimpanzee fibroblasts may have somewhat different adhesive properties, which could play a role in differential disease phenotypes and responses to external factors.

There are a number of documented differences between humans and our closest relatives in responses to wound healing and in disease susceptibilities, suggesting a differential cellular response to certain environmental factors. In this study, we sought to look at a specific cell type, fibroblasts, to examine differences in cellular adhesion between humans and chimpanzees in visualized cells and in gene expression. We have found significant differences in the number of focal adhesions between primary human and chimpanzee fibroblasts. Additionally, we see that adhesion related gene ontology categories are some of the most differentially expressed between human and chimpanzee in normal fibroblast cells. These results suggest that human and chimpanzee fibroblasts may have somewhat different adhesive properties, which could play a role in differential disease phenotypes and responses to external factors.

CD44 Influences Fibroblast Behaviors Via Modulation of Cell-Cell and Cell-Matrix Interactions, Affecting Survivin and Hippo Pathways

CD44 has been studied in a wide variety of cell types, in a diverse array of cell behaviors and in a diverse range of signaling pathways. We now document a role for CD44 in mediating fibroblast behaviors via regulation of N-cadherin, extracellular matrix expression, Survivin and the Hippo pathway. Here, we report our findings on the roles of CD44 in modulating proliferation, apoptosis, migration and invasion of murine wild-type (WT-FB) and CD44 knockout dermal fibroblasts (CD44KO-FB). As we have documented in microvascular endothelial cells lacking CD44, we found persistent increased proliferation, reduced activation of cleaved caspase 3, increased initial attachment, but decreased strength of cell attachment in high cell density, post confluent CD44KO-FB cultures. Additionally, we found that siRNA knock-down of CD44 mimicked the behaviors of CD44KO-FB, restoring the decreases in N-cadherin, collagen type I, fibronectin, Survivin, nuclear fractions of YAP and phospho-YAP and decreased levels of cleaved caspase 3 to the levels observed in CD44KO-FB. Interestingly, plating CD44KO-FB on collagen type I or fibronectin resulted in significant decreases in secondary proliferation rates compared to plating cells on non-coated dishes, consistent with increased cell adhesion compared to their effects on WT-FB. Lastly, siRNA knockdown of CD44 in WT-FB resulted in increased fibroblast migration compared to WT-FB, albeit at reduced rates compared to CD44KO-FB. These results are consistent with CD44's pivotal role in modulating several diverse behaviors important for adhesion, proliferation, apoptosis, migration and invasion during development, growth, repair, maintenance and regression of a wide variety of mesenchymal tissues.

Stability and function of adult vasculature is sustained by Akt/Jagged1 signalling axis in endothelium

The signalling pathways operational in quiescent, post-development vasculature remain enigmatic. Here we show that unlike neovascularization, endothelial Akt signalling in established vasculature is crucial not for endothelial cell (EC) survival, but for sustained interactions with pericytes and vascular smooth muscle cells (VSMCs) regulating vascular stability and function. Inducible endothelial-specific Akt1 deletion in adult global Akt2KO mice triggers progressive VSMC apoptosis. In hearts, this causes a loss of arteries and arterioles and, despite a high capillary density, diminished vascular patency and severe cardiac dysfunction. Similarly, endothelial Akt deletion induces retinal VSMC loss and basement membrane deterioration resulting in vascular regression and retinal atrophy. Mechanistically, the Akt/mTOR axis controls endothelial Jagged1 expression and, thereby, Notch signalling regulating VSMC maintenance. Jagged1 peptide treatment of Akt1ΔEC;Akt2KO mice and Jagged1 re-expression in Akt-deficient endothelium restores VSMC coverage. Thus, sustained endothelial Akt1/2 signalling is critical in maintaining vascular stability and homeostasis, thereby preserving tissue and organ function.

The Akt pathway integrates multiple signals, but whether it affects vasculature function is debatable. Here the authors show that Akt pathway shutdown in adult mouse endothelium causes destabilization of vasculature leading to cardiac and retinal dysfunction, due to decreased levels of Jagged1 and impaired Notch signaling.

A ligand-independent integrin β1 mechanosensory complex guides spindle orientation

Control of spindle orientation is a fundamental process for embryonic development, morphogenesis and tissue homeostasis, while defects are associated with tumorigenesis and other diseases. Force sensing is one of the mechanisms through which division orientation is determined. Here we show that integrin β1 plays a critical role in this process, becoming activated at the lateral regions of the cell cortex in a ligand-independent manner. This activation is force dependent and polar, correlating with the spindle capture sites. Inhibition of integrin β1 activation on the cortex and disruption of its asymmetric distribution leads to spindle misorientation, even when cell adhesion is β1 independent. Examining downstream targets reveals that a cortical mechanosensory complex forms on active β1, and regulates spindle orientation irrespective of cell context. We propose that ligand-independent integrin β1 activation is a conserved mechanism that allows cell responses to external stimuli.

Exploring the interaction between human focal adhesion kinase and inhibitors: a molecular dynamic simulation and free energy calculations

Focal adhesion kinase is an important target for the treatment of many kinds of cancers. Inhibitors of FAK are proposed to be the anticancer agents for multiple tumors. The interaction characteristic between FAK and its inhibitors is crucial to develop new inhibitors. In the present article, we used Molecular Dynamic (MD) simulation method to explore the characteristic of interaction between FAK and three inhibitors (PHM16, TAE226, and ligand3). The MD simulation results together with MM-GB/SA calculations show that the combinations are enthalpy-driven process. Cys502 and Asp564 are both essential residues due to the hydrogen bond interactions with inhibitors, which was in good agreement with experimental data. Glu500 can form a non-classical hydrogen bond with each inhibitor. Arg426 can form electrostatic interactions with PHM16 and ligand3, while weaker with TAE226. The electronic static potential was employed, and we found that the ortho-position methoxy of TAE226 has a weaker negative charge than the meta-position one in PHM16 or ligand3. Ile428, Val436, Ala452, Val484, Leu501, Glu505, Glu506, Leu553, Gly563 Leu567, Ser568 are all crucial residues in hydrophobic interactions. The key residues in this work will be available for further inhibitor design of FAK and also give assistance to further research of cancer.

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.

Modulation of FAK and Src adhesion signaling occurs independently of adhesion complex composition

Integrin adhesion complexes (IACs) form mechanochemical connections between the extracellular matrix and actin cytoskeleton and mediate phenotypic responses via posttranslational modifications. Here, we investigate the modularity and robustness of the IAC network to pharmacological perturbation of the key IAC signaling components focal adhesion kinase (FAK) and Src. FAK inhibition using AZ13256675 blocked FAK(Y397) phosphorylation but did not alter IAC composition, as reported by mass spectrometry. IAC composition was also insensitive to Src inhibition using AZD0530 alone or in combination with FAK inhibition. In contrast, kinase inhibition substantially reduced phosphorylation within IACs, cell migration and proliferation. Furthermore using fluorescence recovery after photobleaching, we found that FAK inhibition increased the exchange rate of a phosphotyrosine (pY) reporter (dSH2) at IACs. These data demonstrate that kinase-dependent signal propagation through IACs is independent of gross changes in IAC composition. Together, these findings demonstrate a general separation between the composition of IACs and their ability to relay pY-dependent signals.

Focal Adhesion Kinase Regulates Fibroblast Migration via Integrin beta-1 and Plays a Central Role in Fibrosis

Lung fibrosis is a major medical problem for the aging population worldwide. Fibroblast migration plays an important role in fibrosis. Focal Adhesion Kinase (FAK) senses the extracellular stimuli and initiates signaling cascades that promote cell migration. This study first examined the dose and time responses of FAK activation in human lung fibroblasts treated with platelet derived growth factor BB (PDGF-BB). The data indicate that FAK is directly recruited by integrin β1 and the subsequent FAK activation is required for fibroblast migration on fibronectin. In addition, the study has identified that α5β1 and α4β1 are the major integrins for FAK-mediated fibroblast migration on fibronect. In contrast, integrins αvβ3, αvβ6, and αvβ8 play a minor but distinct role in fibroblast migration on fibronectin. FAK inhibitor significantly reduces PDGF-BB stimulated fibroblast migration. Importantly, FAK inhibitor protects bleomycin-induced lung fibrosis in mice. FAK inhibitor blocks FAK activation and significantly reduces signaling cascade of fibroblast migration in bleomycin-challenged mice. Furthermore, FAK inhibitor decreases lung fibrotic score, collagen accumulation, fibronectin production, and myofibroblast differentiation in in bleomycin-challenged mice. These data demonstrate that FAK mediates fibroblast migration mainly via integrin β1. Furthermore, the findings suggest that targeting FAK signaling is an effective therapeutic strategy against fibrosis.

The Role of Rac1 in the Growth Cone Dynamics and Force Generation of DRG Neurons

We used optical tweezers, video imaging, immunocytochemistry and a variety of inhibitors to analyze the role of Rac1 in the motility and force generation of lamellipodia and filopodia from developing growth cones of isolated Dorsal Root Ganglia neurons. When the activity of Rac1 was inhibited by the drug EHop-016, the period of lamellipodia protrusion/retraction cycles increased and the lamellipodia retrograde flow rate decreased; moreover, the axial force exerted by lamellipodia was reduced dramatically. Inhibition of Arp2/3 by a moderate amount of the drug CK-548 caused a transient retraction of lamellipodia followed by a complete recovery of their usual motility. This recovery was abolished by the concomitant inhibition of Rac1. The filopodia length increased upon inhibition of both Rac1 and Arp2/3, but the speed of filopodia protrusion increased when Rac1 was inhibited and decreased instead when Arp2/3 was inhibited. These results suggest that Rac1 acts as a switch that activates upon inhibition of Arp2/3. Rac1 also controls the filopodia dynamics necessary to explore the environment.

FAK activation is required for IGF1R-mediated regulation of EMT, migration, and invasion in mesenchymal triple negative breast cancer cells

Triple negative breast cancer (TNBC) is a highly metastatic disease that currently lacks effective prevention and treatment strategies. The insulin-like growth factor 1 receptor (IGF1R) and focal adhesion kinase (FAK) signaling pathways function in numerous developmental processes, and alterations in both are linked with a number of common pathological diseases. Overexpression of IGF1R and FAK are closely associated with metastatic breast tumors. The present study investigated the interrelationship between IGF1R and FAK signaling in regulating the malignant properties of TNBC cells. Using small hairpin RNA (shRNA)-mediated IGF1R silencing methods, we showed that IGF1R is essential for sustaining mesenchymal morphologies of TNBC cells and modulates the expression of EMT-related markers. We further showed that IGF1R overexpression promotes migratory and invasive behaviors of TNBC cell lines. Most importantly, IGF1R-driven migration and invasion is predominantly mediated by FAK activation and can be suppressed using pharmacological inhibitors of FAK. Our findings in TNBC cells demonstrate a novel role of the IGF1R/FAK signaling pathway in regulating critical processes involved in the metastatic cascade. These results may improve the current understanding of the basic molecular mechanisms of TNBC metastasis and provide a strong rationale for co-targeting of IGF1R and FAK as therapy for mesenchymal TNBCs.

Activation of dickkopf-1 and focal adhesion kinase pathway by tumour necrosis factor α induces enhanced migration of fibroblast-like synoviocytes in rheumatoid arthritis

OBJECTIVE

The objective of this study was to investigate the roles of dickkopf-1 (DKK-1) and integrin-related focal adhesion kinase (FAK) by TNF-α on the migration of fibroblast-like synoviocytes (FLSs) in RA.

METHODS

Wound scratch assays were performed to assess FLS migration. Western blotting was used to measure the levels of DKK-1, Wnt signalling molecules and FAK signalling molecules. Quantitative real-time PCR was used to measure the expression levels of DKK-1, integrin αv, laminin, fibronectin, E-cadherin, MMP-8 and MMP-13. The concentrations of DKK-1, TNF-α and GSK-3β were measured by ELISA. Genetic silencing of TNF-α was achieved by the transfection of small interfering RNA into cells.

RESULTS

Migrating RA FLSs exhibited higher levels of DKK-1 and TNF-α expression compared with those in OA FLSs and/or stationary RA FLSs. Moreover, migrating FLSs exhibited significantly higher levels of FAK, p-JNK, paxillin and cdc42 expression, whereas the level of cytosolic β-catenin was lower. WAY-262611, Wnt pathway agonist via inhibition of DKK-1, markedly inhibited cell migration of RA FLSs through the accumulation of cytosolic β-catenin and suppression of FAK-related signalling pathways. TNF-α treatment to RA FLSs up-regulated expression of DKK-1, integrin αv, fibronectin, laminin and MMP-13. TNF-α stimulation also suppressed cytosolic β-catenin and E-cadherin expression in a time-dependent manner. Moreover, TNF-α small interfering RNA-transfected migrating FLSs exhibited decreased activation of integrin-related FAK, paxillin, p-JNK and cdc42 signalling pathways.

CONCLUSION

This study demonstrates that the activation of DKK-1 and the integrin-related FAK signalling pathway stimulated by TNF-α induces the dissociation of β-catenin/E-cadherin, thus promoting RA FLS migration.

Focal adhesion kinase-dependent focal adhesion recruitment of SH2 domains directs SRC into focal adhesions to regulate cell adhesion and migration

Directed cell migration requires dynamical control of the protein complex within focal adhesions (FAs) and this control is regulated by signaling events involving tyrosine phosphorylation. We screened the SH2 domains present in tyrosine-specific kinases and phosphatases found within FAs, including SRC, SHP1 and SHP2, and examined whether these enzymes transiently target FAs via their SH2 domains. We found that the SRC_SH2 domain and the SHP2_N-SH2 domain are associated with FAs, but only the SRC_SH2 domain is able to be regulated by focal adhesion kinase (FAK). The FAK-dependent association of the SRC_SH2 domain is necessary and sufficient for SRC FA targeting. When the targeting of SRC into FAs is inhibited, there is significant suppression of SRC-mediated phosphorylation of paxillin and FAK; this results in an inhibition of FA formation and maturation and a reduction in cell migration. This study reveals an association between FAs and the SRC_SH2 domain as well as between FAs and the SHP2_N-SH2 domains. This supports the hypothesis that the FAK-regulated SRC_SH2 domain plays an important role in directing SRC into FAs and that this SRC-mediated FA signaling drives cell migration.

Compound C inhibits macrophage chemotaxis through an AMPK-independent mechanism

Macrophage infiltration in adipose tissue is a well-established cause of obesity-linked insulin resistance. AMP-activated protein kinase (AMPK) activation in peripheral tissues such as adipose tissue has beneficial effects on the protection against obesity-induced insulin resistance, which is mainly mediated by prevention of adipose tissue macrophage infiltration and inflammation. In examining the role of AMPK on adipose tissue inflammation, we unexpectedly found that compound C (CC), despite its inhibition of AMPK, robustly inhibited macrophage chemotaxis in RAW 264.7 cells when adipocyte conditioned medium (CM) was used as a chemoattractant. Here, we report that CC inhibition of macrophage migration occurred independently of AMPK. Mechanistically, this inhibitory effect of cell migration by CC was mediated by inhibition of the focal adhesion kinase, AKT, nuclear factor κB pathways. Moreover, the expression of chemokine monocyte chemoattractant protein-1 and pro-inflammatory genes such as tumor necrosis factor α and inducible nitric oxide synthase were prevented by CC treatment in RAW 264.7 cells stimulated with either adipocyte CM or lipopolysaccharide. Lastly, in accord with the findings of the anti-inflammatory effect of CC, we demonstrated that CC functioned as a repressor of macrophage CM-mediated insulin resistance in adipocytes. Taken together, our results suggest that CC serves as a useful inhibitory molecule against macrophage chemotaxis into adipose tissue and thus might have therapeutic potential for the treatment of obesity-linked adipose inflammation.

Protein 4.1G Regulates Cell Adhesion, Spreading, and Migration of Mouse Embryonic Fibroblasts through the β1 Integrin Pathway

Protein 4.1G is a membrane skeletal protein that can serve as an adapter between transmembrane proteins and the underlying membrane skeleton. The function of 4.1G remains largely unexplored. Here, using 4.1G knockout mouse embryonic fibroblasts (MEFs) as a model system, we explored the function of 4.1G in motile cells. We show that the adhesion, spreading, and migration of 4.1G(-/-) MEF cells are impaired significantly. We further show that, although the total cellular expression of β1 integrin is unchanged, the surface expression of β1 integrin and its active form are decreased significantly in 4.1G(-/-) MEF cells. Moreover, the phosphorylation of focal adhesion kinase, a downstream component of the integrin-mediated signal transduction pathway, is suppressed in 4.1G(-/-) MEF cells. Co-immunoprecipitation experiments and in vitro binding assays showed that 4.1G binds directly to β1 integrin via its membrane-binding domain. These findings identified a novel role of 4.1G in cell adhesion, spreading, and migration in MEF cells by modulating the surface expression of β1 integrin and subsequent downstream signal transduction.

Multiplexed Fluid Flow Device to Study Cellular Response to Tunable Shear Stress Gradients

Endothelial cells (ECs) line the interior of blood and lymphatic vessels and experience spatially varying wall shear stress (WSS) as an intrinsic part of their physiological function. How ECs, and mammalian cells generally, sense spatially varying WSS remains poorly understood, due in part to a lack of convenient tools for exposing cells to spatially varying flow patterns. We built a multiplexed device, termed a 6-well impinging flow chamber, that imparts controlled WSS gradients to a six-well tissue culture plate. Using this device, we investigated the migratory response of lymphatic microvascular ECs, umbilical vein ECs, primary fibroblasts, and epithelial cells to WSS gradients on hours to days timescales. We observed that lymphatic microvascular ECs migrate upstream, against the direction of flow, a response that was unique among all the cells types investigated here. Time-lapse, live cell imaging revealed that the microtubule organizing center relocated to the upstream side of the nucleus in response to the applied WSS gradient. To further demonstrate the utility of our device, we screened for the involvement of canonical signaling pathways in mediating this upstream migratory response. These data highlight the importance of WSS magnitude and WSS spatial gradients in dictating the cellular response to fluid flow.

The Src non-receptor tyrosine kinase paradigm: New insights into mammalian Sertoli cell biology

Src kinases are non-receptor tyrosine kinases that phosphorylate diverse substrates, which control processes such as cell proliferation, differentiation and survival; cell adhesion; and cell motility. c-Src, the prototypical member of this protein family, is widely expressed by several organs that include the testis. In the seminiferous epithelium of the adult rat testis, c-Src is highest at the tubule lumen during the release of mature spermatids. Other studies show that testosterone regulates spermatid adhesion to Sertoli cells via c-Src, indicating Src phosphorylates key substrates that prompt the disassembly of Sertoli cell-spermatid junctions. A more recent in vitro study reveals that c-Src participates in the internalization of proteins that constitute the blood-testis barrier, which is present between Sertoli cells, suggesting a similar mechanism of junction disassembly is at play during spermiation. In this review, we discuss recent findings on c-Src, with an emphasis on its role in spermatogenesis in the mammalian testis.

Five miRNAs Considered as Molecular Targets for Predicting Esophageal Cancer

Background

Esophageal cancer (EC) is one of the most aggressive malignant gastrointestinal tumors; however the traditional therapies for EC are not effective enough. Great improvements are needed to explore new and valid treatments for EC. We aimed to screen the differentially expressed miRNAs (DEMs) in esophageal cancer and explore the pathogenesis of esophageal cancer along with functions and pathways of the target genes.

Material/Methods

miRNA high-throughput sequencing data were downloaded from The Cancer Genome Atlas (TCGA), then the DEMs underwent principal component analysis (PCA) based on their expression value. Following that, TargetScan software was used to predict the target genes, and enrichment analysis and pathway annotation of these target genes were done by DAVID and KEGG, respectively. Finally, survival analysis between the DEMs and patient survival time was done, and the miRNAs with prediction potential were identified.

Results

A total of 140 DEMs were obtained, 113 miRNAs were up-regulated including hsa-mir-153-2, hsa-mir-92a-1 and hsa-mir-182; while 27 miRNAs were down-regulated including hsa-mir comprising 29a, hsa-mir-100 and hsa-mir-139 and so on. Five miRNAs (hsa-mir-103-1, hsa-mir-18a, hsa-mir-324, hsa-mir-369 and hsa-mir-320b-2) with diagnostic and preventive potential were significantly correlated with survival time.

Conclusions

The crucial molecular targets such as p53 may provide great clinical value in treatment, as well to provide new ideas for esophageal cancer therapy. The target genes of miRNA were found to play key roles in protein phosphorylation, and the functions of the target genes during protein phosphorylation should be further studied to explore novel treatment of EC.

Endocytosis and the Src family of non-receptor tyrosine kinases

The regulated intracellular transport of nutrient, adhesion, and growth factor receptors is crucial for maintaining cell and tissue homeostasis. Endocytosis, or endocytic membrane trafficking, involves the steps of intracellular transport that include, but are not limited to, internalization from the plasma membrane, sorting in early endosomes, transport to late endosomes/lysosomes followed by degradation, and/or recycling back to the plasma membrane through tubular recycling endosomes. In addition to regulating the localization of transmembrane receptor proteins, the endocytic pathway also controls the localization of non-receptor molecules. The non-receptor tyrosine kinase c-Src (Src) and its closely related family members Yes and Fyn represent three proteins whose localization and signaling activities are tightly regulated by endocytic trafficking. Here, we provide a brief overview of endocytosis, Src function and its biochemical regulation. We will then concentrate on recent advances in understanding how Src intracellular localization is regulated and how its subcellular localization ultimately dictates downstream functioning. As Src kinases are hyperactive in many cancers, it is essential to decipher the spatiotemporal regulation of this important family of tyrosine kinases.

FGF2 Overrides TGFβ1-Driven Integrin ITGA11 Expression in Human Dermal Fibroblasts

Deposition of collagen-based extracellular matrix by fibroblasts during wound healing leads to scar formation--a typical outcome of the healing process in soft tissue wounds. The process can, however, be skewed in favor of tissue regeneration by manipulation of wound environment. Low oxygen conditions and supplementation with FGF2 provide extracellular cues that drive wound fibroblasts towards a pro-regenerative phenotype. Under these conditions, fibroblasts dramatically alter expression of many genes among which the most significantly deregulated are extracellular matrix and adhesion molecules. Here we investigate the mechanism of a collagen I binding integrin α11 (ITGA11) deregulation in response to low oxygen-mediated FGF2 effects in dermal fibroblasts. Using RT-PCR, qRT-PCR, Western blotting, and immunocytochemistry, we describe significant down-regulation of ITGA11. Decrease in ITGA11 is associated with its loss from focal adhesions. We show that loss of ITGA11 requires FGF2 induced ERK1/2 activity and in the presence of FGF2, ITGA11 expression cannot be rescued by TGFβ1, a potent activator of ITGA11. Our results indicate that FGF2 may be redirecting fibroblasts towards an anti-fibrotic phenotype by overriding TGFβ1 mediated ITGA11 expression.

LRRK2 G2019S mutation attenuates microglial motility by inhibiting focal adhesion kinase

In response to brain injury, microglia rapidly extend processes that isolate lesion sites and protect the brain from further injury. Here we report that microglia carrying a pathogenic mutation in the Parkinson's disease (PD)-associated gene, G2019S-LRRK2 (GS-Tg microglia), show retarded ADP-induced motility and delayed isolation of injury, compared with non-Tg microglia. Conversely, LRRK2 knockdown microglia are highly motile compared with control cells. In our functional assays, LRRK2 binds to focal adhesion kinase (FAK) and phosphorylates its Thr–X–Arg/Lys (TXR/K) motif(s), eventually attenuating FAK activity marked by decreased pY397 phosphorylation (pY397). GS-LRRK2 decreases the levels of pY397 in the brain, microglia and HEK cells. In addition, treatment with an inhibitor of LRRK2 kinase restores pY397 levels, decreased pTXR levels and rescued motility of GS-Tg microglia. These results collectively suggest that G2019S mutation of LRRK2 may contribute to the development of PD by inhibiting microglial response to brain injury.

In response to brain injury, microglia extend processes to isolate the lesion. Here Choi et al. show that microglia expressing a pathogenic mutation in the Parkinson's disease-associated LRRK2 gene show reduced motility and delayed lesion isolation in vitro and in vivo due to attenuated focal adhesion kinase activity.

ODAM inhibits RhoA-dependent invasion in breast cancer

Odontogenic ameloblast-associated protein (ODAM) contributes to cell adhesion. In human cancer, ODAM is down-regulated, and the overexpression of ODAM results in a favourable prognosis; however, the molecular mechanisms underlying ODAM-mediated inhibition of cancer invasion and metastasis remain unclear. Here, we identify a critical role for ODAM in inducing cancer cell adhesion. ODAM induced RhoA activity and the expression of downstream factors, including Rho-associated kinase (ROCK). ODAM-mediated RhoA signalling resulted in actin filament rearrangement by activating PTEN and inhibiting the phosphorylation of AKT. When ODAM is overexpressed in MCF7 breast cancer cells and AGS gastric cancer cells that activate RhoA at high levels, it decreases motility, increases adhesion and inhibits the metastasis of MCF7 cells. Conversely, depletion of ODAM in cancer cells inhibits Rho GTPase activation, resulting in increased cancer migration and invasion. These results suggest that ODAM expression in cells maintains their adhesion, resulting in the prevention of their metastasis via the regulation of RhoA signalling in breast cancer cells. SIGNIFICANCE Breast cancer represents the first most frequent cancer, and the ratio of mortality is high in women. Of utmost importance for reducing risk by breast cancer are their anti-invasion mechanisms, particularly in the non-invasive cancer cells because metastasis is the principal cause of death among cancer patients. ODAM induced RhoA activity. ODAM-mediated RhoA signalling resulted in actin filament rearrangement, increased cell adhesion and inhibited the migration/invasion of MCF7 cells. These results suggest that ODAM expression maintains their adhesion, resulting in the prevention of their metastasis via the regulation of RhoA signalling in breast cancer cells.

Mechanisms underlying the cytotoxicity of a novel quinazolinedione-based redox modulator, QD232, in pancreatic cancer cells

BACKGROUND AND PURPOSE

Pancreatic cancer is characterized by alterations in several key signalling proteins, including increased expression and activity of the Src tyrosine kinase and focal adhesion kinase (FAK), which have been linked to its chemoresistance. Sustained Src inhibition reactivates survival pathways regulated by the transcription factor STAT3, also leading to resistance. Therefore, simultaneously targeting Src/FAK and STAT3 signalling could provide an important strategy for treating pancreatic cancer. Recently, we described novel quinazolinediones that increased generation of reactive oxygen species (ROS) and were cytotoxic in pancreatic cancer cells. Here, we have investigated effects of our lead compound, QD232, on Src/FAK and STAT3 signalling.

EXPERIMENTAL APPROACH

The major signalling pathways affected by QD232 in pancreatic cancer cell lines were identified by Kinexus proteomic analysis. Changes in key signalling proteins were confirmed by Western blotting. Cell migration was assessed by Boyden chamber and wound healing assays. Direct inhibition of kinase activity in vitro was assayed with a panel of 92 oncogenic kinases. Safety and efficacy of QD232 were determined in a xenograft mouse model of pancreatic cancer.

KEY RESULTS

QD232 potently inhibited Src/FAK and STAT3 phosphorylation, decreasing pancreatic cancer cell viability and migration. Furthermore, QD232 arrested cell cycle progression and induced apoptosis in these cells at low micromolar concentrations. Effects of QD232 on Src/FAK and STAT3 phosphorylation were blocked by N-acetylcysteine or glutathione.

CONCLUSIONS AND IMPLICATIONS

QD232 is a novel compound with a unique, ROS-dependent mechanism, effective in drug-resistant cancer cell lines. This compound shows potential as therapy for pancreatic cancer.

Down-regulation of ALDH1A3, CD44 or MDR1 sensitizes resistant cancer cells to FAK autophosphorylation inhibitor Y15

PURPOSE

Focal adhesion kinase is an important survival signal in cancer. Recently, we demonstrated that the autophosphorylation inhibitor of FAK, Y15, effectively inhibited cancer cell growth. We detected many cancer cell lines sensitive to Y15 and also detected several cell lines such as colon cancer Lovo-1 and thyroid K1 more resistant to Y15. We sought to determine the main players responsible for the resistance.

METHODS

To reveal the signaling pathways responsible for the increased resistance of these cancer cells to the inhibitor of FAK, we performed a microarray gene profile study in both sensitive and resistant cells treated with Y15 inhibitor to compare with the more sensitive cells.

RESULTS

Among unique genes up-regulated by Y15 in Lovo-1 and K1 resistant cells, a stem cell marker-ALDH1A3-was detected to be up-regulated >twofold. The resistant Lovo-1 and thyroid K1 cells overexpressed ALDH1A3 and CD44 versus sensitive cells. Treatment with ALDH1A3 siRNAs or ALDH inhibitor, DEAB sensitized resistant Lovo-1 and K1 cells to Y15 inhibitor, decreased viability and caused G1 cell cycle arrest more effectively than each agent alone. In addition, down-regulation of CD44 that was overexpressed in resistant Lovo-1 cells with CD44 siRNA effectively decreased the viability of cells in combination with Y15. In addition, down-regulation of overexpressed MDR1 with specific inhibitor, PSC-833, also sensitized resistant colon cancer cells to Y15.

CONCLUSIONS

This report clearly demonstrates the mechanism of resistance to FAK autophosphorylation inhibitor and the mechanism to overcome it that is important for developing FAK-targeted therapy approaches.

Endothelial Cell mTOR Complex-2 Regulates Sprouting Angiogenesis

Tumor neovascularization is targeted by inhibition of vascular endothelial growth factor (VEGF) or the receptor to prevent tumor growth, but drug resistance to angiogenesis inhibition limits clinical efficacy. Inhibition of the phosphoinositide 3 kinase pathway intermediate, mammalian target of rapamycin (mTOR), also inhibits tumor growth and may prevent escape from VEGF receptor inhibitors. mTOR is assembled into two separate multi-molecular complexes, mTORC1 and mTORC2. The direct effect of mTORC2 inhibition on the endothelium and tumor angiogenesis is poorly defined. We used pharmacological inhibitors and RNA interference to determine the function of mTORC2 versus Akt1 and mTORC1 in human endothelial cells (EC). Angiogenic sprouting, EC migration, cytoskeleton re-organization, and signaling events regulating matrix adhesion were studied. Sustained inactivation of mTORC1 activity up-regulated mTORC2-dependent Akt1 activation. In turn, ECs exposed to mTORC1-inhibition were resistant to apoptosis and hyper-responsive to renal cell carcinoma (RCC)-stimulated angiogenesis after relief of the inhibition. Conversely, mTORC1/2 dual inhibition or selective mTORC2 inactivation inhibited angiogenesis in response to RCC cells and VEGF. mTORC2-inactivation decreased EC migration more than Akt1- or mTORC1-inactivation. Mechanistically, mTORC2 inactivation robustly suppressed VEGF-stimulated EC actin polymerization, and inhibited focal adhesion formation and activation of focal adhesion kinase, independent of Akt1. Endothelial mTORC2 regulates angiogenesis, in part by regulation of EC focal adhesion kinase activity, matrix adhesion, and cytoskeletal remodeling, independent of Akt/mTORC1.

Cell-Substrate Interactions Feedback to Direct Cell Migration along or against Morphological Polarization

In response to external stimuli, cells polarize morphologically into teardrop shapes prior to moving in the direction of their blunt leading edge through lamellipodia extension and retraction of the rear tip. This textbook description of cell migration implies that the initial polarization sets the direction of cell migration. Using microfabrication techniques to control cell morphologies and the direction of migration without gradients, we demonstrate that after polarization, lamelipodia extension and attachment can feedback to change and even reverse the initial morphological polarization. Cells do indeed migrate faster in the direction of their morphologically polarization. However, feedback from subsequent lamellipodia extension and attachment can be so powerful as to induce cells to reverse and migrate against their initial polarization, albeit at a slower speed. Constitutively active mutants of RhoA show that RhoA stimulates cell motility when cells are guided either along or against their initial polarization. Cdc42 activation and inhibition, which results in loss of directional motility during chemotaxis, only reduces the speed of migration without altering the directionality of migration on the micropatterns. These results reveal significant differences between substrate directed cell migration and that induced by chemotactic gradients.

Depression of focal adhesion kinase induces apoptosis in rat osteosarcoma OSR-6 cells in a caspase-dependent pathway

Focal adhesion kinase (FAK), a nonreceptor tyrosine kinase protein, acts as an early modulator of integrin signaling cascade, regulating basic cellular functions. In transformed cells, unopposed FAK signaling has been considered to promote tumor growth, progression, and metastasis. The aim of this study was to assess the role of FAK in rat osteosarcoma OSR-6 cells. OSR-6 cells were transfected with PGPU6/GFP/shNC (shNC), and PGPU6/GFP/FAK-2434 (shRNA-2434), separately. Expression of FAK was detected by Real-time PCR and Western blots. MTT assay was used to examine changes in cell proliferation. Cell apoptosis was analyzed by flow cytometry. The expression of caspase-3,-7,-9 was measured by Western blots. The expression of FAK in OSR-6 cells significantly decreased in shRNA-2434 group in contrast to the control group (P < 0.01). Cell proliferation was inhibited by shRNA-2434 and shRNA-2434+ cisplatin, and the effects were clearly enhanced when cells were treated with anticancer agents. The level of cell apoptosis in shRNA-2434 and shRNA-2434+ cisplatin group was higher than that in the control group (P < 0.01). The current data support evidence that down-regulation of FAK could induce rat osteosarcoma cells (OSR-6) apoptosis through the caspase-dependent cell death pathway. Inhibition of the kinases may be important for therapies designed to enhance the apoptosis in osteosarcoma.

The extracellular matrix and insulin resistance

The extracellular matrix (ECM) is a highly-dynamic compartment that undergoes remodeling as a result of injury and repair. Over the past decade, mounting evidence in humans and rodents suggests that ECM remodeling is associated with diet-induced insulin resistance in several metabolic tissues. In addition, integrin receptors for the ECM have also been implicated in the regulation of insulin action. This review addresses what is currently known about the ECM, integrins, and insulin action in the muscle, liver, and adipose tissue. Understanding how ECM remodeling and integrin signaling regulate insulin action may aid in the development of new therapeutic targets for the treatment of insulin resistance and type 2 diabetes (T2D).

PTK2 rs7460 and rs7843014 polymorphisms and exceptional longevity: a functional replication study

Focal adhesion is critical for cell survival. The focal adhesion kinase (FAK, or PTK2) is an important component of the human interactome and thus is a potential longevity-related protein. Here we studied the association between two PTK2 gene single-nucleotide polymorphisms (SNPs) (rs7843014, rs7460) and exceptional longevity (EL). In addition to gaining insight into their functionality by determining luciferase gene reporter activity, we studied the genotype/allele frequency of these two SNPs among three different cohorts: (1) Spanish centenarians (n=175, 100-111 years, 144 women) and healthy controls (n=355, 20-50 years, 284 women); (2) Italian centenarians (n=79, 100-104 years, 40 women) and controls (n=316, 29-50 years, 156 women); and (3) Japanese centenarians (n=742, 100-116 years, 623 women) and healthy controls (n=499, 23-59 years, 356 women). Both SNPs had functional significance, with the A allele up-regulating luciferase activity compared to the other allele (rs7460 T allele and rs7843014 C allele, respectively). The A allele of both SNPs was negatively associated with EL in the Spanish cohort (rs7460, odds ratio [OR] adjusted by sex=0.40, 95% confidence intervals [CI] 0.3, 0.6, p<0.001); rs7843014, OR=0.37, 95% CI 0.3, 0.5, p<0.001). The OR of being a centenarian if having the rs7460-TT genotype was 6.68 (95% CI 4.1, 10.8, p<0.001). The rs7843014 CC genotype was also positively associated with EL (OR=7.58, 95% CI 4.6, 12.3, p<0.001]. No association was, however, found for the Italian or Japanese cohorts. Thus, two genotypes of the FAK gene, rs7460 TT and rs7843014 CC, are possibly associated with lower gene expression and might favor the likelihood of reaching EL in the Spanish population. Further research is needed to unveil the mechanisms by which FAK expression could perhaps influence the rate of aging.

Progress in neuregulin/ErbB signaling and chronic heart failure

Heart failure is one of the leading causes of death today. It is a complex clinical syndrome in which the heart has a reduced contraction ability and decreased viable myocytes. Novel approaches to the clinical management of heart failure have been achieved through an understanding of the molecular pathways necessary for normal heart development. Neuregulin-1 (NRG-1) has emerged as a potential therapeutic target based on the fact that mice null for NRG-1 or receptors mediating its activity, ErbB2 and ErbB4, are embryonic lethal and exhibit severe cardiac defects. Preclinical studies performed with animal models of heart failure demonstrate that treatment with NRG-1 significantly improves heart function and survival. Clinical data further support NRG-1 as a promising drug candidate for the treatment of cardiac dysfunction in patients. Recent studies have revealed the mechanism underlying the therapeutic effects of NRG-1/ErbB signaling in the treatment of heart failure. Through activation of upstream signaling molecules such as phosphoinositide 3-kinase, mitogen-activated protein kinase, and focal adhesion kinase, NRG-1/ErbB pathway activation results in increased cMLCK expression and enhanced intracellular calcium cycling. The former is a regulator of the contractile machinery, and the latter triggers cell contraction and relaxation. In addition, NRG-1/ErbB signaling also influences energy metabolism and induces epigenetic modification in cardiac myocytes in a way that more closely resembles healthy heart. These observations reveal potentially new treatment options for heart failure.

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.

Regulation of the microtubular cytoskeleton by Polycystin-1 favors focal adhesions turnover to modulate cell adhesion and migration

Background

Polycystin-1 (PC-1) is a large plasma membrane receptor, encoded by the PKD1 gene, which is mutated in most cases of Autosomal Dominant Polycystic Kidney Disease (ADPKD). The disease is characterized by renal cysts. The precise function of PC-1 remains elusive, although several studies suggest that it can regulate the cellular shape in response to external stimuli. We and others reported that PC-1 regulates the actin cytoskeleton and cell migration.

Results

Here we show that cells over-expressing PC-1 display enhanced adhesion rates to the substrate, while cells lacking PC-1 have a reduced capability to adhere. In search for the mechanism responsible for this new property of PC-1 we found that this receptor is able to regulate the stability of the microtubules, in addition to its capability to regulate the actin cytoskeleton. The two cytoskeletal components are acting in a coordinated fashion. Notably, we uncovered that PC-1 regulation of the microtubule cytoskeleton impacts on the turnover rates of focal adhesions in migrating cells and we link all these properties to the capability of PC-1 to regulate the activation state of Focal Adhesion Kinase (FAK).

Conclusions

In this study we show several new features of the PC-1 receptor in modulating microtubules and adhesion dynamics, which are essential for its capability to regulate migration.

Electronic supplementary material

The online version of this article (doi:10.1186/s12860-015-0059-3) contains supplementary material, which is available to authorized users.

2-Hydroxyethyl methacrylate inhibits migration of dental pulp stem cells

INTRODUCTION

Cell migration is an important step in pulpal wound healing. Although components in the resin-based dental materials are known to have adverse effects on pulp wound healing including proliferation and mineralization, their effects on cell migration have been scarcely examined. Here, we investigated the effects of 2-hydroxyethyl methacrylate (HEMA) on the migration of dental pulp stem cells (DPSC) in vitro.

METHODS

Cell viability was assessed using the MTT (3-(4, 5-dimethylthiazolyl-2)-2, 5-diphenyltetrazolium bromide) assay, and cell migration was evaluated using the wound scratch assay and transwell migration assay at noncytotoxic doses. The Western blot was used to examine pathways associated with migration such as focal adhesion kinase, mitogen-activated protein kinase, and glycogen synthase kinase 3.

RESULTS

There were no drastic changes in the cell viability below 3 mmol/L HEMA. When DPSCs were treated with HEMA at 0.5, 1.0, and 2.5 mmol/L, cell migration was diminished. HEMA-treated DPSCs exhibited the loss of phosphorylated focal adhesion kinase in a dose-dependent manner. The HEMA-mediated inhibition of cell migration was associated with phosphorylation of p38 but not glycogen synthase kinase 3, Extracellular signal-related kinase (ERK), or c-Jun N-terminal kinase (JNK) pathways. When we inhibited the p38 signaling pathway using a p38 inhibitor, the migration of DPSCs was suppressed.

CONCLUSIONS

HEMA inhibits the migration of dental pulp cells in vitro, suggesting that poor pulpal wound healing under resin-based dental materials may be caused, in part, by the inhibition of cell migration by HEMA.

Cell adhesion proteins: roles in periodontal physiology and discovery by proteomics

Adhesion molecules expressed by periodontal connective tissue cells are involved in cell migration, matrix remodeling and inflammatory responses to infection. Currently, the processes by which the biologic activity of these molecules are appropriately regulated in time and space to preserve tissue homeostasis, and to control inflammatory responses and tissue regeneration, are not defined. As cell adhesions are heterogeneous, dynamic, contain a complex group of interacting molecules and are strongly influenced by the type of substrate to which they adhere, we focus on how cell adhesions in periodontal connective tissues contribute to information generation and processing that regulate periodontal structure and function. We also consider how proteomic methods can be applied to discover novel cell-adhesion proteins that could potentially contribute to the form and function of periodontal tissues.

Junctional complex and focal adhesion rearrangement mediates pulmonary endothelial barrier enhancement by FTY720 S-phosphonate

RATIONALE

Modulation of pulmonary vascular barrier function is an important clinical goal given the devastating effects of vascular leak in acute lung injury (ALI). We previously demonstrated that FTY720 S-phosphonate (Tys), an analog of sphingosine 1-phosphate (S1P) and FTY720, has more potent pulmonary barrier protective effects than these agents in vitro and in mouse models of ALI. Tys preserves expression of the barrier-promoting S1P1 receptor (S1PR1), whereas S1P and FTY720 induce its ubiquitination and degradation. Here we further characterize the novel barrier promoting effects of Tys in cultured human pulmonary endothelial cells (EC).

METHODS/RESULTS

In human lung EC, Tys significantly increased peripheral redistribution of adherens junction proteins VE-cadherin and β-catenin and tight junction protein ZO-1. Inhibition of VE-cadherin with blocking antibody significantly attenuated Tys-induced transendothelial resistance (TER) elevation, while ZO-1 siRNA partially inhibited this elevation. Tys significantly increased focal adhesion formation and phosphorylation of focal adhesion kinase (FAK). Pharmacologic inhibition of FAK significantly attenuated Tys-induced TER elevation. Tys significantly increased phosphorylation and peripheral redistribution of the actin-binding protein, cortactin, while cortactin siRNA partially attenuated Tys-induced TER elevation. Although Tys significantly increased phosphorylation of Akt and GSK3β, neither PI3 kinase nor GSK3β inhibition altered Tys-induced TER elevation. Tys significantly increased Rac1 activity, while inhibition of Rac1 activity significantly attenuated Tys-induced VE-cadherin redistribution and TER elevation.

CONCLUSION

Junctional complex, focal adhesion rearrangement and Rac1 activation play critical roles in Tys-mediated barrier protection in pulmonary EC. These results provide mechanistic insights into the effects of this potential ALI therapy.

Functions of the FAK family kinases in T cells: beyond actin cytoskeletal rearrangement

T cells control the focus and extent of adaptive immunity in infectious and pathological diseases. The activation of T cells occurs when the T cell antigen receptor (TCR) and costimulatory and/or adhesion receptors are engaged by their ligands. This process drives signaling that promotes cytoskeletal rearrangement and transcription factor activation, both of which regulate the quality and magnitude of the T cell response. However, it is not fully understood how different receptor-induced signals combine to alter T cell activation. The related non-receptor tyrosine kinases focal adhesion kinase (FAK) and proline-rich tyrosine kinase 2 (Pyk2) are phosphorylated downstream of the TCR and several costimulatory and adhesion receptors. FAK family proteins integrate receptor-mediated signals that influence actin cytoskeletal rearrangement and effector T cell responses. In this review, we summarize the receptor-specific roles that FAK and Pyk2 control to influence T cell development and activation.

Cell migration within confined sandwich-like nanoenvironments

Aim: We introduced sandwich-like culture as a tool to engineer the cellular nanoenvironment by tuning protein presentation and activation of dorsal and ventral receptors. We aim at studying cell migration under more similar conditions to the 3D physiological one. Materials & methods: We have investigated different nanoenvironments by changing the protein coating and using materials that adsorb proteins in different conformation, seeking to show their specific role in cell migration. Results: Cell migration within sandwich cultures greatly differs from 2D cultures, shares some similarities with migration within 3D environments and is highly dependent on the protein nanoenvironment. Beyond differences in cell morphology and migration, dorsal stimulation promotes cell remodeling of the extracellular matrix over simple ventral receptor activation in traditional 2D cultures. Conclusion: Local(nano) stimulation of dorsal and ventral receptors within sandwich cultures alter cell migration in comparison to standard 2D environments.

Identification of novel focal adhesion kinase substrates: role for FAK in NFκB signaling

Focal adhesion kinase (FAK) is a major signaling molecule which functions downstream of integrins or in conjunction with mitogenic signaling pathways. FAK is overexpressed and/or activated in many types of human tumors, in which it promotes cell adhesion, survival, migration and invasion. In addition to FAK's ability to regulate signaling through its scaffolding activities, FAK encodes an intrinsic kinase activity. Although some FAK substrates have been identified, a more comprehensive analysis of substrates is lacking. In this study, we use a protein microarray to screen the human proteome for FAK substrates. We confirm that several of the proteins identified are bona fide in vitro FAK substrates, including several factors which are known to regulate the NFκB pathway. Finally, we identify a role for FAK's kinase activity in both canonical and non-canonical NFκB signaling. Our screen therefore represents the first high throughput screen for FAK substrates and provides the basis for future in-depth analysis of the role of FAK's kinase activity in the processes of tumorigenesis.

Role of focal adhesion kinase in oocyte-follicle communication

Germ cells require communication with associated somatic cells for normal gametogenesis, as exemplified by an oocyte that interacts with granulosa cells via paracrine factors as well as gap junctions located at sites of contact between these two cell types. The objective of the present study was to define the mechanisms by which cell-cell contact with the oocyte is controlled and to determine the extent that the oocyte actively participates in this association. Proline-rich tyrosine kinase 2 (PTK2), a focal adhesion kinase, was found to be activated at sites of contact between the oocyte and trans-zonal cell processes from the surrounding granulosa cells. In order to determine the functional significance of oocyte-derived PTK2 signaling in oocyte-follicle communication, an oocyte-specific Ptk2 knockout was produced through a breeding strategy pairing a floxed Ptk2-CAT-eGFP mouse with the Zp3-Cre line. Since Ptk2-null mice never develop to birth, this represents the first opportunity to define the role of PTK2 in oocyte-follicle communication. Ablation of Ptk2 within the developing oocyte resulted in lower fertility with reduced numbers of pups, lower rates of blastocyst formation, and reduced cell numbers per blastocyst. Follicles containing Ptk2-null oocytes exhibited reduced oocyte diameter, reduced numbers of connexin 37 and 43 foci at the oocyte surface, and impaired dye coupling between oocyte and granulosa cells. These findings are consistent with a model in which PTK2 plays a critical role in establishing or maintaining oocyte-granulosa cell contacts that are essential for gap junction-mediated communication between granulosa cells and the oocyte.

Myoferlin depletion elevates focal adhesion kinase and paxillin phosphorylation and enhances cell-matrix adhesion in breast cancer cells

Breast cancer is the second leading cause of malignant death among women. A crucial feature of metastatic cancers is their propensity to lose adhesion to the underlying basement membrane as they transition to a motile phenotype and invade surrounding tissue. Attachment to the extracellular matrix is mediated by a complex of adhesion proteins, including integrins, signaling molecules, actin and actin-binding proteins, and scaffolding proteins. Focal adhesion kinase (FAK) is pivotal for the organization of focal contacts and maturation into focal adhesions, and disruption of this process is a hallmark of early cancer invasive potential. Our recent work has revealed that myoferlin (MYOF) mediates breast tumor cell motility and invasive phenotype. In this study we demonstrate that noninvasive breast cancer cell lines exhibit increased cell-substrate adhesion and that silencing of MYOF using RNAi in the highly invasive human breast cancer cell line MDA-MB-231 also enhances cell-substrate adhesion. In addition, we detected elevated tyrosine phosphorylation of FAK (FAK(Y397)) and paxillin (PAX(Y118)), markers of focal adhesion protein activation. Morphometric analysis of PAX expression revealed that RNAi-mediated depletion of MYOF resulted in larger, more elongated focal adhesions, in contrast to cells transduced with a control virus (MDA-231(LVC) cells), which exhibited smaller focal contacts. Finally, MYOF silencing in MDA-MB-231 cells exhibited a more elaborate ventral cytoskeletal structure near focal adhesions, typified by pronounced actin stress fibers. These data support the hypothesis that MYOF regulates cell adhesions and cell-substrate adhesion strength and may account for the high degree of motility in invasive breast cancer cells.