Phosphorylation Of Paxillin Research Articles

Deletion of the Ste20-like kinase SLK in skeletal muscle results in a progressive myopathy and muscle weakness

BackgroundThe Ste20-like kinase, SLK, plays an important role in cell proliferation and cytoskeletal remodeling. In fibroblasts, SLK has been shown to respond to FAK/Src signaling and regulate focal adhesion turnover through Paxillin phosphorylation. Full-length SLK has also been shown to be essential for embryonic development. In myoblasts, the overexpression of a dominant negative SLK is sufficient to block myoblast fusion.MethodsIn this study, we crossed the Myf5-Cre mouse model with our conditional SLK knockout model to delete SLK in skeletal muscle. A thorough analysis of skeletal muscle tissue was undertaken in order to identify defects in muscle development caused by the lack of SLK. Isometric force analysis was performed on adult knockout mice and compared to age-matched wild-type mice. Furthermore, cardiotoxin injections were performed followed by immunohistochemistry for myogenic markers to assess the efficiency muscle regeneration following SLK deletion.ResultsWe show here that early deletion of SLK from the myogenic lineage does not markedly impair skeletal muscle development but delays the regenerative process. Interestingly, adult mice (~6 months) display an increase in the proportion of central nuclei and increased p38 activation. Furthermore, mice as young as 3 months old present with decreased force generation, suggesting that the loss of SLK impairs myofiber stability and function. Assessment of structural components revealed aberrant localization of focal adhesion proteins, such as FAK and paxillin. Our data show that the loss of SLK results in unstable myofibers resulting in a progressive myopathy. Additionally, the loss of SLK resulted in a delay in muscle regeneration following cardiotoxin injections.ConclusionsOur results show that SLK is dispensable for muscle development and regeneration but is required for myofiber stability and optimal force generation.

The selective cysteinyl leukotriene receptor 1 (CysLT1R) antagonist montelukast regulates extracellular matrix remodeling

Scar formation after filtration surgery of glaucoma is mainly caused by excessive synthesis of new extracellular matrix (ECM) and contraction of subconjunctival tissue mediated by human Tenon fibroblasts (HTFs) and the transforming growth factor (TGF-β1). Montelukast, a potent and specific cysteinyl leukotriene receptor 1 (cysLT1R) antagonist, is a licensed drug clinically used for the treatment of bronchial asthma. In this study, we investigated the effects of montelukast on the contractility of HTFs cultured in a three-dimensional collagen gel. We found that cysLT1R was expressed in HTFs. Interestingly, the expression of cysLT1R was increased in response to TGF-β1 in a dose dependent manner, suggesting its potential role in TGF-β1 induced fibrosis. Importantly, we found that montelukast inhibited TGF-β1-induced collagen gel contraction mediated by HTFs in a concentration- and time-dependent manner. In addition, TGF-β1-induced expression of MMP-1 and MMP-3, generation of fibronectin and type I collagen production, focal adhesion kinase (FAK) and paxillin phosphorylation in HTFs were also ameliorated by montelukast in a dose dependent manner. These results suggested that montelukast might provide therapeutic possibilities for inhibition of scar formation after such surgery.

Distinct focal adhesion protein modules control different aspects of mechanotransduction.

Focal adhesions (FAs) are macromolecular complexes that regulate cell adhesion and mechanotransduction. By performing fluorescence recovery after photobleaching (FRAP) and fluorescence loss after photoactivation (FLAP) experiments, we found that the mobility of core FA proteins correlates with their function. Structural proteins such as tensin, talin and vinculin are significantly less mobile in FAs than signaling proteins such as FAK (also known as PTK2) and paxillin. The mobilities of the structural proteins are directly influenced by substrate stiffness, suggesting that they are involved in sensing the rigidity of the extracellular environment. The turnover rates of FAK and paxillin, as well as kindlin2 (also known as FERMT2), are not influenced by substrate stiffness. By using specific Src and FAK inhibitors, we reveal that force-sensing by vinculin occurs independently of FAK and paxillin phosphorylation. However, their phosphorylation is required for downstream Rac1-driven cellular processes, such as protrusion and cell migration. Overall, we show that the FA is composed of different functional modules that separately control mechanosensing and the cellular mechano-response.

A RhoG-mediated signaling pathway that modulates invadopodia dynamics in breast cancer cells.

One of the hallmarks of cancer is the ability of tumor cells to invade surrounding tissues and metastasize. During metastasis, cancer cells degrade the extracellular matrix, which acts as a physical barrier, by developing specialized actin-rich membrane protrusion structures called invadopodia. The formation of invadopodia is regulated by Rho GTPases, a family of proteins that regulates the actin cytoskeleton. Here, we describe a novel role for RhoG in the regulation of invadopodia disassembly in human breast cancer cells. Our results show that RhoG and Rac1 have independent and opposite roles in the regulation of invadopodia dynamics. We also show that SGEF (also known as ARHGEF26) is the exchange factor responsible for the activation of RhoG during invadopodia disassembly. When the expression of either RhoG or SGEF is silenced, invadopodia are more stable and have a longer lifetime than in control cells. Our findings also demonstrate that RhoG and SGEF modulate the phosphorylation of paxillin, which plays a key role during invadopodia disassembly. In summary, we have identified a novel signaling pathway involving SGEF, RhoG and paxillin phosphorylation, which functions in the regulation of invadopodia disassembly in breast cancer cells.

The opposite mechano-response of paxillin phosphorylation between subcellular and whole-cell levels is explained by a minimal model of cell-substrate adhesions

The opposite mechano-response of paxillin phosphorylation between subcellular and whole-cell levels is explained by a minimal model of cell-substrate adhesions

Antcin‐H Isolated from Antrodia cinnamomea Inhibits Renal Cancer Cell Invasion Partly through Inactivation of FAK‐ERK‐C/EBP‐β/c‐Fos‐MMP‐7 Pathways

Antcin-H, a natural triterpene, is purified from a famous anticancer medicinal mushroom, Antrodia cinnamomea, in Taiwan. This study showed that antcin-H inhibited the growth of human renal carcinoma 786-0 cells; the IC50 value (for 48 h) was 170 μM. Besides, the migration and invasion of 786-0 cells were suppressed by antcin-H under noncytotoxic concentrations (<100 μM); these events were accompanied by inhibition of FAK and Src kinase activities, decrease of paxillin phosphorylation, impairment of lamellipodium formation, and upregulation of TIMPs and downregulation of MMPs, especially MMP-7 expression. Luciferase reporter assay showed that antcin-H repressed the MMP-7 promoter activity, in parallel to inhibiting c-Fos/AP-1 and C/EBP-β transactivation abilities. Moreover, antcin-H suppressed the activity of ERK1/2 and decreased the binding ability of C/EBP-β and c-Fos on the upstream/enhancer region of MMP-7 promoter. Overall, this study demonstrated that the anti-invasive effect of antcin-H in human renal carcinoma 786-0 cells might be at least in part by abrogating focal adhesion complex and lamellipodium formation through inhibiting the Src/FAK-paxillin signaling pathways and decreasing MMP-7 expression through suppressing the ERK1/2-AP-1/c-Fos and C/EBP-β signaling axis. Our findings provide the evidence that antcin-H may be an active component existing in A. cinnamomea with anticancer effect.

The molecular mechanisms underlying the ER\u03b1-36-mediated signaling in breast cancer

Alterations in estrogen-mediated cellular signaling have largely been implicated in the pathogenesis of breast cancer. Here, we investigated the signaling regulation of a splice variant of the estrogen receptor, namely estrogen receptor (ERα-36), associated with a poor prognosis in breast cancers. Coupling in vitro and in vivo approaches we determined the precise sequential molecular events of a new estrogen signaling network in an ERα-negative cell line and in an original patient-derived xenograft. After estrogen treatment, ERα-36 rapidly associates with Src at the level of the plasma membrane, initiating downstream cascades, including MEK1/ERK activation and paxillin phosphorylation on S126, which in turn triggers a higher expression of cyclin D1. Of note, the direct binding of ERα-36 to ERK2 prevents its dephosphorylation by MKP3 and enhances the downstream signaling. These findings improve our understanding of the regulation of non-genomic estrogen signaling and open new avenues for personalized therapeutic approaches targeting Src or MEK in ERα-36-positive patients.

A potential contribution of dipeptidyl peptidase-4 by the mediation of monocyte differentiation in the development and progression of abdominal aortic aneurysms

ObjectiveAbdominal aortic aneurysms (AAAs) are characterized by the destruction of elastin and collagen in the media and adventitia. Dipeptidyl peptidase-4 (DPP-4, an adipokine known as CD26) influences cell signaling, cell-matrix interactions, and the regulation of the functional activity of incretins in metabolic and inflammatory disorders. Although the role of DPP-4 in AAA evolution has been demonstrated, the underlying mechanisms of DPP-4-regulated AAA development remains unknown. MethodsPatients with AAA (n = 93) and healthy controls (CTL, n = 20) were recruited. Based on computed tomography image analyses, 93 patients were divided into two groups: those with a small AAA (SAA, aortic diameter <5 cm, n = 16) and those with a large AAA (LAA, aortic diameter ≥5 cm, n = 77). Plasma DPP-4, glucagon-like peptide-1 levels, and expression of CD26 on mononuclear cells were analyzed. In addition, phorbol 12-myristate 13-acetate (PMA)-induced THP-1 cells and angiotensin II-infused apolipoprotein EtmlUnc mice were used to explore the underlying mechanisms. ResultsThe levels of DPP-4 (μU/μg) increased while active glucagon-like peptide-1 (pM) decreased in patients with AAA in a diameter-dependent manner [CTL: 2.3 ± 1.5 and 3.7 ± 2.4, respectively; SAA: 10.0 ± 10.9 and 2.1 ± 0.9, respectively; LAA: 32.2 ± 15.0 and 1.8 ± 1.1, respectively]. A significant decline in monocyte CD26 expression in patients with AAAs was observed relative to the CTL group. In vitro studies demonstrated that the inhibition of DPP-4 promoted PMA-induced monocytic cells differentiation, with increased CD68 and p21 expression, regulated by extracellular signal-regulated protein kinase 1/2 activation. Furthermore, inhibition of DPP-4 significantly increased the phosphorylation of PYK2 and paxillin in PMA-induced THP-1 cell differentiation. Finally, the animal study was used to confirm the in vitro results that LAA mice showed marked macrophage infiltration in the adventitia with a decreased expression of DPP-4 as compared with SAA mice. ConclusionsIncreased plasma DPP-4 activity may correlate with aneurysmal development. CD26 on monocytes plays a critical role in cell differentiation, possibly mediated by extracellular signal-regulated protein kinase 1/2-p21 axis signaling pathways and cytoskeletal proteins reassembly. Exploring the role of DPP-4 further may yield potential therapeutic insights.

Novel Small Molecule JP-153 Targets the Src-FAK-Paxillin Signaling Complex to Inhibit VEGF-Induced Retinal Angiogenesis.

Targeting vascular endothelial growth factor (VEGF) is a common treatment strategy for neovascular eye disease, a major cause of vision loss in diabetic retinopathy and age-related macular degeneration. However, the decline in clinical efficacy over time in many patients suggests that monotherapy of anti-VEGF protein therapeutics may benefit from adjunctive treatments. Our previous work has shown that through decreased activation of the cytoskeletal protein paxillin, growth factor-induced ischemic retinopathy in the murine oxygen-induced retinopathy model could be inhibited. In this study, we demonstrated that VEGF-dependent activation of the Src/FAK/paxillin signalsome is required for human retinal endothelial cell migration and proliferation. Specifically, the disruption of focal adhesion kinase (FAK) and paxillin interactions using the small molecule JP-153 inhibited Src-dependent phosphorylation of paxillin (Y118) and downstream activation of Akt (S473), resulting in reduced migration and proliferation of retinal endothelial cells stimulated with VEGF. However, this effect did not prevent the initial activation of either Src or FAK. Furthermore, topical application of a JP-153-loaded microemulsion affected the hallmark features of pathologic retinal angiogenesis, reducing neovascular tuft formation and increased avascular area, in a dose-dependent manner. In conclusion, our results suggest that using small molecules to modulate the focal adhesion protein paxillin is an effective strategy for treating pathologic retinal neovascularization. To our knowledge, this is the first paradigm validating modulation of paxillin to inhibit angiogenesis. As such, we have identified and developed a novel class of small molecules aimed at targeting focal adhesion protein interactions that are essential for pathologic neovascularization in the eye.

Myocardin-related transcription factor A (MRTF-A) activity-dependent cell adhesion is correlated to focal adhesion kinase (FAK) activity.

The regulation of cell-substrate adhesion is tightly linked to the malignant phenotype of tumor cells and plays a role in their migration, invasion, and metastasis. Focal adhesions (FAs) are dynamic adhesion structures that anchor the cell to the extracellular matrix. Myocardin-related transcription factors (MRTFs), co-regulators of the serum response factor (SRF), regulate expression of a set of genes encoding actin cytoskeletal/FA-related proteins. Here we demonstrated that the forced expression of a constitutively active MRTF-A (CA-MRTF-A) in B16F10 melanoma cells induced the up-regulation of actin cytoskeletal and FA proteins, resulting in FA reorganization and the suppression of cell migration. Expression of CA-MRTF-A markedly increased phosphorylation of focal adhesion kinase (FAK) and paxillin, which are important components for FA dynamics. Notably, FAK activation was triggered by the clustering of up-regulated integrins. Our results revealed that the MRTF-SRF-dependent regulation of cell migration requires both the up-regulation of actin cytoskeletal/FA proteins and the integrin-mediated regulation of FA components via the FAK/Src pathway. We also demonstrated that activation of the MRTF-dependent transcription correlates FAK activation in various tumor cells. The elucidation of the correlation between MRTF and FAK activities would be an effective therapeutic target in focus of tumor cell migration.

Bupleurum chinense polysaccharide inhibit adhesion of human melanoma cells via blocking β1 integrin function

Adhesive interaction contributes toward tumor metastasis and the transmembrane glycoprotein receptor, integrin has been recognized to mediate the adhesion to extracellular matrix thus upregulating tumor metastasis. In the current study, we evaluated the anti-adhesive mechanisms of a water-soluble polysaccharide (BCP) extracted from Bupleurum chinense. BCP inhibited integrin-mediated adhesion of human melanoma A375 cells to fibronectin but had no effects on nonspecific adhesion to poly-l-lysine. BCP also reduced β1 integrin ligand affinity for GST-FNIII9-10 proteins. The adhesion-dependent formation of F-actin stress fiber and focal adhesion (FA) was also inhibited by BCP treatment. The inhibition of BCP on integrin-mediated signaling is probably through inhibiting phosphorylation of focal adhesion kinase (FAK) and paxillin. Collectively, our current findings indicated that BCP may be a potential therapy for melanoma metastasis due to its inhibitory effects on integrin function.

Fibronectin induces macrophage migration through a SFK-FAK/CSF-1R pathway

ABSTRACTIntegrins, following binding to proteins of the extracellular matrix (ECM) including collagen, laminin and fibronectin (FN), are able to transduce molecular signals inside the cells and to regulate several biological functions such as migration, proliferation and differentiation. Besides activation of adaptor molecules and kinases, integrins transactivate Receptor Tyrosine Kinases (RTK). In particular, adhesion to the ECM may promote RTK activation in the absence of growth factors. The Colony-Stimulating Factor-1 Receptor (CSF-1R) is a RTK that supports the survival, proliferation, and motility of monocytes/macrophages, which are essential components of innate immunity and cancer development. Macrophage interaction with FN is recognized as an important aspect of host defense and wound repair. The aim of the present study was to investigate on a possible cross-talk between FN-elicited signals and CSF-1R in macrophages. FN induced migration in BAC1.2F5 and J774 murine macrophage cell lines and in human primary macrophages. Adhesion to FN determined phosphorylation of the Focal Adhesion Kinase (FAK) and Src Family Kinases (SFK) and activation of the SFK/FAK complex, as witnessed by paxillin phosphorylation. SFK activity was necessary for FAK activation and macrophage migration. Moreover, FN-induced migration was dependent on FAK in either murine macrophage cell lines or human primary macrophages. FN also induced FAK-dependent/ligand-independent CSF-1R phosphorylation, as well as the interaction between CSF-1R and β1. CSF-1R activity was necessary for FN-induced macrophage migration. Indeed, genetic or pharmacological inhibition of CSF-1R prevented FN-induced macrophage migration. Our results identified a new SFK-FAK/CSF-1R signaling pathway that mediates FN-induced migration of macrophages.

Staphylococcus aureus α-toxin-mediated cation entry depolarizes membrane potential and activates p38 MAP kinase in airway epithelial cells.

Membrane potential (Vm)-, Na(+)-, or Ca(2+)-sensitive fluorescent dyes were used to analyze changes in Vm or intracellular ion concentrations in airway epithelial cells treated with Staphylococcus aureus α-toxin (Hla), a major virulence factor of pathogenic strains of these bacteria. Gramicidin, a channel-forming peptide causing membrane permeability to monovalent cations, a mutated form of Hla, rHla-H35L, which forms oligomers in the plasma membranes of eukaryotic cells but fails to form functional transmembrane pores, or the cyclodextrin-derivative IB201, a blocker of the Hla pore, were used to investigate the permeability of the pore. Na(+) as well as Ca(2+) ions were able to pass the Hla pore and accumulated in the cytosol. The pore-mediated influx of calcium ions was blocked by IB201. Treatment of cells with recombinant Hla resulted in plasma membrane depolarization as well as in increases in the phosphorylation levels of paxillin (signaling pathway mediating disruption of the actin cytoskeleton) and p38 MAP kinase (signaling pathway resulting in defensive actions). p38 MAP kinase phosphorylation, but not paxillin phosphorylation, was elicited by treatment of cells with gramicidin. Although treatment of cells with rHla-H35L resulted in the formation of membrane-associated heptamers, none of these cellular effects were observed in our experiments. This indicates that formation of functional Hla-transmembrane pores is required to induce the cell physiological changes mediated by α-toxin. Specifically, the changes in ion equilibria and plasma membrane potential are important activators of p38 MAP kinase, a signal transduction module involved in host cell defense.

Erratum: The rat tyrosine phosphatase η increases cell adhesion by activating c-Src through dephosphorylation of its inhibitory phosphotyrosine residue

The expression of the receptor protein tyrosine phosphatase r-PTPeta is drastically reduced in rat and human malignant thyroid cells, whereas its restoration reverts the neoplastic phenotype of retrovirally transformed rat thyroid cells. Moreover, reduced levels and loss of heterozygosity of DEP-1, the human homolog of r-PTPeta, have been found in many human neoplasias. Here, we report that the r-PTPeta protein binds to c-Src in living cells and dephosphorylates the c-Src inhibitory tyrosine phosphorylation site (Tyr 529), thereby increasing c-Src tyrosine kinase activity in malignant rat thyroid cells stably transfected with r-PTPeta. Tyrosine phosphorylation of focal adhesion kinase (FAK) and paxillin was enhanced in r-PTPeta-expressing cells. This was associated with increased adhesion of malignant r-PTPeta-transfected thyroid cells vs both untransfected cells and cells stably transfected with an inactive r-PTPeta mutant. Treatment of rat thyroid cells with the c-Src inhibitor PP2 decreased cell adhesion to a higher extent in r-PTPeta-transfected cells than in mock-transfected or stably transfected cells with the inactive r-PTPeta mutant, indicating that r-PTPeta regulates cell-substratum adhesion by activating c-Src. Interestingly, the extent of both c-Src dephosphorylation at Tyr 529, FAK and paxillin phosphorylation, and the increased cell adhesion were associated with the degree of r-PTPeta expression.

Regulation of paxillin-p130-PI3K-AKT signaling axis by Src and PTPRT impacts colon tumorigenesis.

Protein tyrosine phosphatase receptor T (PTPRT) is frequently mutated in a variety of human cancers including colorectal cancer. Here we report that PTPRT knockout increases the size of mouse colon tumors in the Apcmin+/− genetic background, suggesting that inactivation of PTPRT promotes tumor progression. We previously demonstrated that PTPRT dephosphorylates paxillin at tyrosine-Y88 residue. Consistently, phosphorylation of Y88 paxillin (pY88) is up-regulated in colon tumors derived from Apcmin+/− Ptprt−/− mice. An important downstream effector of pY88 paxillin is the oncogene Akt. Here, we show that pY88 paxillin impacts the Akt pathway by regulating the interaction between p130cas and the p85 regulatory subunit of PI3-Kinase. Additionally, while pY88 paxillin is a substrate of the tumor suppressor phosphatase PTPRT, the corresponding kinase has not been previously identified. In this study, we demonstrate that the oncogenic kinase Src directly phosphorylates paxillin at Y88. Moreover, colorectal cancer cells that express high levels of pY88 paxillin are sensitive to dasatinib treatment, suggesting that pY88 paxillin may serve as a predictive biomarker for Src family kinase inhibitors.

Abstract 702: Serglycin promotes cell migration via modulating cytoskeleton reorganization and enhancing focal adhesion turnover

Abstract Serglycin (SRGN), a hematopoietic cell granule proteoglycan, has recently been shown to be overexpressed in several aggressive cancer types. In nasopharyngeal and hepatocellular carcinomas, elevated expression of SRGN was shown to correlate with poor prognosis. However, the molecular mechanisms underlying SRGN-mediated malignancies remain to be explored. In this study, we showed that SRGN is expressed at elevated levels in several lung cancer-derived cell lines. By gain-of-function and loss-of-function approaches, we showed that SRGN promoted NSCLC cell migration. SRGN modulated actin cytoskeleton reorganization and promoted lamellipodia and filopodia formation at the leading edge, facilitating a directional movement during wound closure in NSCLC cells. In consistence, increased levels of activated Rac1, which is required for lamellipodia formation, and CDC42, which is required for filopodia formation, were detected. Increased focal adhesion (FA) turnover, the process of continuous assembly and disassembly of adhesions, would lead to increased cell migration. We further showed that SRGN promoted Src activation, leading to increased phosphorylation of paxillin (PAX) at Y118 as well as reduced PAX/FAK complex formation, which were well-defined indicators of FA turnover. Taken together, these data suggested that SRGN promotes cell migration through inducing cytoskeleton reorganization and focal adhesion turnover. Citation Format: Jeou-Yuan Chen, Jing-You Guo. Serglycin promotes cell migration via modulating cytoskeleton reorganization and enhancing focal adhesion turnover. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 702.

Graphene Oxide Hierarchical Patterns for the Derivation of Electrophysiologically Functional Neuron-like Cells from Human Neural Stem Cells.

Graphene has shown great potential for biomedical engineering applications due to its electrical conductivity, mechanical strength, flexibility, and biocompatibility. Topographical cues of culture substrates or tissue-engineering scaffolds regulate the behaviors and fate of stem cells. In this study, we developed a graphene oxide (GO)-based patterned substrate (GPS) with hierarchical structures capable of generating synergistic topographical stimulation to enhance integrin clustering, focal adhesion, and neuronal differentiation in human neural stem cells (hNSCs). The hierarchical structures of the GPS were composed of microgrooves (groove size: 5, 10, and 20 μm), ridges (height: 100-200 nm), and nanoroughness surfaces (height: ∼10 nm). hNSCs grown on the GPS exhibited highly elongated, aligned neurite extension along the ridge of the GPS and focal adhesion development that was enhanced compared to that of cells grown on GO-free flat substrates and GO substrates without the hierarchical structures. In particular, GPS with a groove width of 5 μm was found to be the most effective in activating focal adhesion signaling, such as the phosphorylation of focal adhesion kinase and paxillin, thereby improving neuronal lineage commitment. More importantly, electrophysiologically functional neuron-like cells exhibiting sodium channel currents and action potentials could be derived from hNSCs differentiated on the GPS even in the absence of any of the chemical agents typically required for neurogenesis. Our study demonstrates that GPS could be an effective culture platform for the generation of functional neuron-like cells from hNSCs, providing potent therapeutics for treating neurodegenerative diseases and neuronal disorders.

772 - The molecular mechanisms underlying the ERα-36-mediated signaling in breast cancer

Alterations in estrogen-mediated cellular signaling have largely been implicated in the pathogenesis of breast cancer. Here, we investigated the signaling regulation of a splice variant of the estrogen receptor, namely estrogen receptor (ERα-36), associated with a poor prognosis in breast cancers. Coupling in vitro and in vivo approaches we determined the precise sequential molecular events of a new estrogen signaling network in an ERα-negative cell line and in an original patient-derived xenograft. After estrogen treatment, ERα-36 rapidly associates with Src at the level of the plasma membrane, initiating downstream cascades, including MEK1/ERK activation and paxillin phosphorylation on S126, which in turn triggers a higher expression of cyclin D1. Of note, the direct binding of ERα-36 to ERK2 prevents its dephosphorylation by MKP3 and enhances the downstream signaling. These findings improve our understanding of the regulation of non-genomic estrogen signaling and open new avenues for personalized therapeutic approaches targeting Src or MEK in ERα-36-positive patients.

Capsaicin Inhibits Multiple Bladder Cancer Cell Phenotypes by Inhibiting Tumor-Associated NADH Oxidase (tNOX) and Sirtuin1 (SIRT1).

Bladder cancer is one of the most frequent cancers among males, and its poor survival rate reflects problems with aggressiveness and chemo-resistance. Recent interest has focused on the use of chemopreventatives (nontoxic natural agents that may suppress cancer progression) to induce targeted apoptosis for cancer therapy. Capsaicin, which has anti-cancer properties, is one such agent. It is known to preferentially inhibit a tumor-associated NADH oxidase (tNOX) that is preferentially expressed in cancer/transformed cells. Here, we set out to elucidate the correlation between tNOX expression and the inhibitory effects of capsaicin in human bladder cancer cells. We showed that capsaicin downregulates tNOX expression and decreases bladder cancer cell growth by enhancing apoptosis. Moreover, capsaicin was found to reduce the expression levels of several proteins involved in cell cycle progression, in association with increases in the cell doubling time and enhanced cell cycle arrest. Capsaicin was also shown to inhibit the activation of ERK, thereby reducing the phosphorylation of paxillin and FAK, which leads to decreased cell migration. Finally, our results indicate that RNA interference-mediated tNOX depletion enhances spontaneous apoptosis, prolongs cell cycle progression, and reduces cell migration and the epithelial-mesenchymal transition. We also observed a downregulation of sirtuin 1 (SIRT1) in these tNOX-knockdown cells, a deacetylase that is important in multiple cellular functions. Taken together, our results indicate that capsaicin inhibits the growth of bladder cancer cells by inhibiting tNOX and SIRT1 and thereby reducing proliferation, attenuating migration, and prolonging cell cycle progression.

Cyclin D1 promotes tumor cell invasion and metastasis by cytoplasmic mechanisms

ABSTRACTAmplification of cyclin D1 is a frequent alteration in many cancers of different type and origin. We recently described a novel regulatory axis involving cyclin D1 in the regulation of tumor invasion and metastasis. Membrane-associated cyclin D1-CDK4 complexes promote activation of the small GTPase RAC1 through phosphorylation of the regulatory protein paxillin.