ROCK1 but not ROCK2 contributes to RhoA signaling and NMIIA-mediated contractility at the epithelial zonula adherens

Coactosin-like protein 1 regulates integrity and repair of model intestinal epithelial barriers via actin binding dependent and independent mechanisms

The actin cytoskeleton regulates the integrity and repair of epithelial barriers by mediating the assembly of tight junctions (TJs), and adherens junctions (AJs), and driving epithelial wound healing. Actin filaments undergo a constant turnover guided by numerous actin-binding proteins, however, the roles of actin filament dynamics in regulating intestinal epithelial barrier integrity and repair remain poorly understood. Coactosin-like protein 1 (COTL1) is a member of the ADF/cofilin homology domain protein superfamily that binds and stabilizes actin filaments. COTL1 is essential for neuronal and cancer cell migration, however, its functions in epithelia remain unknown. The goal of this study is to investigate the roles of COTL1 in regulating the structure, permeability, and repair of the epithelial barrier in human intestinal epithelial cells (IEC). COTL1 was found to be enriched at apical junctions in polarized IEC monolayers in vitro. The knockdown of COTL1 in IEC significantly increased paracellular permeability, impaired the steady state TJ and AJ integrity, and attenuated junctional reassembly in a calcium-switch model. Consistently, downregulation of COTL1 expression in Drosophila melanogaster increased gut permeability. Loss of COTL1 attenuated collective IEC migration and decreased cell-matrix attachment. The observed junctional abnormalities in COTL1-depleted IEC were accompanied by the impaired assembly of the cortical actomyosin cytoskeleton. Overexpression of either wild-type COTL1 or its actin-binding deficient mutant tightened the paracellular barrier and activated junction-associated myosin II. Furthermore, the actin-uncoupled COTL1 mutant inhibited epithelial migration and matrix attachment. These findings highlight COTL1 as a novel regulator of the intestinal epithelial barrier integrity and repair.

Plakophilin 4 controls the spatio-temporal activity of RhoA at adherens junctions to promote cortical actin ring formation and tissue tension

Plakophilin 4 (PKP4) is a component of cell-cell junctions that regulates intercellular adhesion and Rho-signaling during cytokinesis with an unknown function during epidermal differentiation. Here we show that keratinocytes lacking PKP4 fail to develop a cortical actin ring, preventing adherens junction maturation and generation of tissue tension. Instead, PKP4-depleted cells display increased stress fibers. PKP4-dependent RhoA localization at AJs was required to activate a RhoA-ROCK2-MLCK-MLC2 axis and organize actin into a cortical ring. AJ-associated PKP4 provided a scaffold for the Rho activator ARHGEF2 and the RhoA effectors MLCK and MLC2, facilitating the spatio-temporal activation of RhoA signaling at cell junctions to allow cortical ring formation and actomyosin contraction. In contrast, association of PKP4 with the Rho suppressor ARHGAP23 reduced ARHGAP23 binding to RhoA which prevented RhoA activation in the cytoplasm and stress fiber formation. These data identify PKP4 as an AJ component that transduces mechanical signals into cytoskeletal organization.

Protective effects of low-intensity pulsed ultrasound (LIPUS) against cerebral ischemic stroke in mice by promoting brain vascular remodeling via the inhibition of ROCK1/p-MLC2 signaling pathway

Vascular remodeling is essential for patients with cerebral ischemic stroke (CIS). Our previous study proved that low-intensity pulsed ultrasound (LIPUS) could increase cortical hemodynamics. However, the effects and mechanisms of LIPUS on cerebral vascular remodeling after CIS are still unknown. In this study, we applied LIPUS to the mouse brain at 0.5 h after distal middle cerebral artery occlusion (dMCAO) and subsequently daily for a stimulation time of 30 min. Results showed that compared with the dMCAO group, LIPUS markedly increased cerebral blood flow (CBF), reduced brain swelling, and improved functional recovery at day 3 after CIS. LIPUS promoted leptomeningeal vasculature remodeling, enlarged vascular diameter, and increased the average vessel length and density at day 3 after CIS. Proteomic analysis highlighted that LIPUS mainly participated in the regulation of actin cytoskeleton pathway. Rho kinase 1 (ROCK1) was downregulated by LIPUS and participated in regulation of actin cytoskeleton. Subsequently, we verified that ROCK1 was mainly expressed in pericytes. Furthermore, we demonstrated that LIPUS inhibited ROCK1/p-MLC2 signaling pathway after CIS, which had positive effects on vascular remodeling and cerebral blood circulation. In conclusion, our preliminary study revealed the vascular remodeling effects and mechanism of LIPUS in CIS, provided evidence for potential clinical application of LIPUS.

Push-pull mechanics of E-cadherin ectodomains in biomimetic adhesions

E-cadherin plays a central role in cell-cell adhesion. The ectodomains of wild-type cadherins form a crystalline-like two-dimensional lattice in cell-cell interfaces mediated by both trans (apposed cell) and cis (same cell) interactions. In addition to these extracellular forces, adhesive strength is further regulated by cytosolic phenomena involving α and β catenin-mediated interactions between cadherin and the actin cytoskeleton. Cell-cell adhesion can be further strengthened under tension through mechanisms that have not been definitively characterized in molecular detail. Here we quantitatively determine the role of the cadherin ectodomain in mechanosensing. To this end, we devise an E-cadherin-coated emulsion system, in which droplet surface tension is balanced by protein binding strength to give rise to stable areas of adhesion. To reach the honeycomb/cohesive limit, an initial emulsion compression by centrifugation facilitates E-cadherin trans binding, whereas a high protein surface concentration enables the cis-enhanced stabilization of the interface. We observe an abrupt concentration dependence on recruitment into adhesions of constant crystalline density, reminiscent of a first-order phase transition. Removing the lateral cis interaction with a "cis mutant" shifts this transition to higher surface densities leading to denser, yet weaker adhesions. In both proteins, the stabilization of progressively larger areas of deformation is consistent with single-molecule experiments that show a force-dependent lifetime enhancement in the cadherin ectodomain, which may be attributed to the "X-dimer" bond.

Inflammation modulates intercellular adhesion and mechanotransduction in human epidermis via ROCK2

Aberrant mechanotransduction and compromised epithelial barrier function are associated with numerous human pathologies including inflammatory skin disorders. However, the cytoskeletal mechanisms regulating inflammatory responses in the epidermis are not well understood. Here we addressed this question by inducing a psoriatic phenotype in human keratinocytes and reconstructed human epidermis using a cytokine stimulation model. We show that the inflammation upregulates the Rho-myosin II pathway and destabilizes adherens junctions (AJs) promoting YAP nuclear entry. The integrity of cell-cell adhesion but not the myosin II contractility per se is the determinative factor for the YAP regulation in epidermal keratinocytes. The inflammation-induced disruption of AJs, increased paracellular permeability, and YAP nuclear translocation are regulated by ROCK2, independently from myosin II activation. Using a specific inhibitor KD025, we show that ROCK2 executes its effects via cytoskeletal and transcription-dependent mechanisms to shape the inflammatory response in the epidermis.

Key role of Rho GTPases in motor disorders associated with neurodevelopmental pathologies

Growing evidence suggests that Rho GTPases and molecules involved in their signaling pathways play a major role in the development of the central nervous system (CNS). Whole exome sequencing (WES) and de novo examination of mutations, including SNP (Single Nucleotide Polymorphism) in genes coding for the molecules of their signaling cascade, has allowed the recent discovery of dominant autosomic mutations and duplication or deletion of candidates in the field of neurodevelopmental diseases (NDD). Epidemiological studies show that the co-occurrence of several of these neurological pathologies may indeed be the rule. The regulators of Rho GTPases have often been considered for cognitive diseases such as intellectual disability (ID) and autism. But, in a remarkable way, mild to severe motor symptoms are now reported in autism and other cognitive NDD. Although a more abundant litterature reports the involvement of Rho GTPases and signaling partners in cognitive development, molecular investigations on their roles in central nervous system (CNS) development or degenerative CNS pathologies also reveal their role in embryonic and perinatal motor wiring through axon guidance and later in synaptic plasticity. Thus, Rho family small GTPases have been revealed to play a key role in brain functions including learning and memory but their precise role in motor development and associated symptoms in NDD has been poorly scoped so far, despite increasing clinical data highlighting the links between cognition and motor development. Indeed, early impairements in fine or gross motor performance is often an associated feature of NDDs, which then impact social communication, cognition, emotion, and behavior. We review here recent insights derived from clinical developmental neurobiology in the field of Rho GTPases and NDD (autism spectrum related disorder (ASD), ID, schizophrenia, hypotonia, spastic paraplegia, bipolar disorder and dyslexia), with a specific focus on genetic alterations affecting Rho GTPases that are involved in motor circuit development.

Rho-associated kinase1 promotes laryngeal squamous cell carcinoma tumorigenesis and progression via the FAK signaling pathway

Laryngeal squamous cell carcinoma (LSCC) is one of the most common head and neck squamous cell carcinomas (HNSCC). Rho-associated kinase1 (ROCK1) is considered to promote progression of numerous cancers, however, its role in LSCC is still unknown. Here, the expression level of ROCK1 is higher in LSCC tissues than non-tumor tissues, and the expression level of ROCK1 is positively correlated with advanced stage and poor survival prognosis. ROCK1 knockdown in TU686 and TU212 cells dramatically inhibits cellular proliferation, migration and invasion. Whereas the overexpression of ROCK1 reversed these changes. FAK signaling pathway plays an essential role in promoting LSCC progression. Inhibiting FAK activity with TAE226 observably impairs the tumor-promoting effects. In conclusion, ROCK1 promotes LSCC tumorigenesis and progression via the FAK signaling pathway, targeting the ROCK1 molecule may represent potential targets for clinical LSCC treatment.

Shenqihuatan formula reduces inflammation by inhibiting transforming growth factor-beta-stimulated signaling pathway in airway smooth muscle cells

OBJECTIVE

To study the effects and mechanism of Shenqihuatan formula (, SQHT) of the transforming growth factor-beta (TGF-β)-stimulated cell processes in airway remodeling.

METHODS

The current study examined cell viability using a Cell Counting Kit-8 assay. Furthermore, a Transwell assay was conducted to detect the ability of cell migration, and apoptosis was detected via flowcytometry. Western Blot and quantitative real-time polymerase chain reaction (qRT-PCR) were used to determine the expression levels of apoptosis or inflammation-related factors, such as TGF-β, Interleukin-1β (IL-1β), B cell lymphoma 2 (Bcl-2), Bcl-2-Associated X (Bax), Ras homolog gene family, member A (RhoA), recombinant rho associated coiled coil containing protein kinase 1/2 (ROCK1/2), extracellular regulated protein kinases 1/2 (ERK1/2), Snail, and Slug. Finally, the expression levels of matrix metalloproteinase-9 (MMP-9) and Tissue inhibitor of metalloproteinase (TIMP-1) were admeasured by enzyme-linked immuno sorbent assay.

RESULTS

The results demonstrated that SQHT inhibited the viability and migration, as well as the the F-actin formation and cytoskeletal reorganization of airway smooth muscle cells (ASMCs) stimulated by TGF-β. By monitoring the changes of critical regulators in the presence of the formula, it was observed that the expression levels of TGF-β, IL-1β, Bcl-2, RhoA, ROCK1/2, ERK1/2, Snail, and Slug were markedly suppressed, whereas Bax expression exhibited the opposite effect. Compared with a well-characterized RhoA pathway inhibitor, Fasudil, SQHT generated equivalent or even higher inhibitory effects on these processes in ASMCs.

CONCLUSIONS

Collectively, these suggested that SQHT can reduce airway inflammation by inhibiting TGF-β-stimulated signaling pathways in ASMCs. These findings may provide a novel remedy for treating ASMC inflammation, which causes thickening and obstruction of the airway in chronic obstructive pulmonary disease.

Laminin-511 activates the human induced pluripotent stem cell survival via α6β1 integrin-Fyn-RhoA-ROCK signaling

In human induced pluripotent stem cells (hiPSCs), laminin-511/α6β1 integrin interacts with E-cadherin, an intercellular adhesion molecule, to induce the activation of the PI3K-dependent signaling pathway. The interaction between laminin-511/α6β1 integrin and E-cadherin, an intercellular adhesion molecule, results in protection against apoptosis via the proto-oncogene tyrosine-protein kinase Fyn(Fyn)-RhoA-ROCK signaling pathway and the Ras homolog gene family member A (RhoA)/Rho kinase (ROCK) signaling pathway (the major pathway for cell death). In this paper, the impact of laminin-511 on hiPSC on α6β1 integrin-Fyn-RhoA-ROCK signaling is discussed and explored along with validation experiments. PIK3CA mRNA (mean [standard deviation {SD}]: iMatrix-511, 1.00 [0. 61]; collagen+MFGE8, 0.023 [0.02]; **P<0.01; n=6) and PIK3R1 mRNA (mean [SD]: iMatrix-511, 1.00 [0. 79]; collagen+MFGE8, 0.040 [0.06]; *P<0.05; n=6) were upregulated by iMatrix-511 resulting from an increased expression of Integrin α6 mRNA (mean [SD]: iMatrix-511, 1.00 [0. 42]; collagen+MFGE8, 0.23 [0.05]; **P<0.01; n=6). iMatrix-511 increased the expression of p120-Catenin mRNA (mean [SD]: iMatrix-511, 1.00 [0. 71]; collagen+MFGE8, 0.025 [0.03]; **P<0.01; n=6) and RAC1 mRNA (mean [SD]: iMatrix-511, 1.00 [0. 28]; collagen+MFGE8, 0.39 [0.15]; **P<0.01; n=6) by increasing the expression of E-cadherin mRNA (mean [SD]: iMatrix-511, 1.00 [0. 38]; collagen+MFGE8, 0.16 [0.11]; **P<0.01; n=6). As a result, iMatrix-511 increased the expression of P190 RhoGAP (GTPase-activating proteins) mRNA, such as ARHGAP1 mRNA (mean [SD]: iMatrix-511, 1.00 [0. 57]; collagen+MFGE8, 0.032 [0.03]; **P<0.01; n=6), ARHGAP4 mRNA (mean [SD]: iMatrix-511, 1.00 [0. 56]; collagen+MFGE8, 0.039 [0.049]; **P<0.01; n=6), and ARHGAP5 mRNA (mean [SD]: iMatrix-511, 1.00 [0. 39]; collagen+MFGE8, 0.063 [0.043]; **P<0.01; n=6). Western blotting showed that phospho-Rac1 remained in the cytoplasm and phospho-Fyn showed nuclear transition in iPSCs cultured on iMatrix-511. Proteome analysis showed that PI3K signaling was enhanced and cytoskeletal actin was activated in iPSCs cultured on iMatrix-511. In conclusion, laminin-511 strongly activated the cell survival by promoting α6β1 integrin-Fyn-RhoA-ROCK signaling in hiPSCs.

ROCK1 mechano-signaling dependency of human malignancies driven by TEAD/YAP activation

Rho family mechano-signaling through the actin cytoskeleton positively regulates physiological TEAD/YAP transcription, while the evolutionarily conserved Hippo tumor suppressor pathway antagonizes this transcription through YAP cytoplasmic localization/degradation. The mechanisms responsible for oncogenic dysregulation of these pathways, their prevalence in tumors, as well as how such dysregulation can be therapeutically targeted are not resolved. We demonstrate that p53 DNA contact mutants in human tumors, indirectly hyperactivate RhoA/ROCK1/actomyosin signaling, which is both necessary and sufficient to drive oncogenic TEAD/YAP transcription. Moreover, we demonstrate that recurrent lesions in the Hippo pathway depend on physiological levels of ROCK1/actomyosin signaling for oncogenic TEAD/YAP transcription. Finally, we show that ROCK inhibitors selectively antagonize proliferation and motility of human tumors with either mechanism. Thus, we identify a cancer driver paradigm and a precision medicine approach for selective targeting of human malignancies driven by TEAD/YAP transcription through mechanisms that either upregulate or depend on homeostatic RhoA mechano-signaling.

LncRNA SNHG20 promotes migration and invasion of ovarian cancer via modulating the microRNA-148a/ROCK1 axis

BACKGROUND

Ovarian cancer (OC) is characterized by early metastasis and poor prognosis, which threatens the health of women worldwide. Small nucleolar RNA host gene 20 (SNHG20), a long noncoding RNA (lncRNA), has been verified to be significantly up-regulated in several tumors, including OC. MicroRNA-148a (miR-148a)/rho-kinase1 (ROCK1) axis plays an important role in the modulation of tumor development. However, whether SNHG20 can regulate OC progression through miR-148a/ROCK1 axis remains unclear. Normal human ovarian epithelial cell line and four OC cell lines were adopted for in vitro experiments. Real-time PCR was performed to assess the levels of SNHG20 and miR-148a. OC cell proliferation, apoptosis, invasion and migration were detected using clone formation, flow cytometry, transwell, and wound healing assays, respectively. Tumor xenograft assay was applied to evaluate the effect of SNHG20 on tumor growth in vivo.

RESULTS

Significant higher expression of SNHG20 was observed in OC cell lines. SNHG20 markedly promoted the invasion, migration, proliferation and inhibited the apoptosis of OC cells. SNHG20 enhanced ROCK1 expression by sponging miR-148a, and the direct binding between SNHG20/ROCK1 and miR-148a was identified.

CONCLUSION

SNHG20 promoted invasion and migration of OC via targeting miR-148a/ROCK1 axis. The present research may provide a novel insight for the therapeutic strategies of OC.

EpCAM promotes endosomal modulation of the cortical RhoA zone for epithelial organization

At the basis of cell shape and behavior, the organization of actomyosin and its ability to generate forces are widely studied. However, the precise regulation of this contractile network in space and time is unclear. Here, we study the role of the epithelial-specific protein EpCAM, a contractility modulator, in cell shape and motility. We show that EpCAM is required for stress fiber generation and front-rear polarity acquisition at the single cell level. In fact, EpCAM participates in the remodeling of a transient zone of active RhoA at the cortex of spreading epithelial cells. EpCAM and RhoA route together through the Rab35/EHD1 fast recycling pathway. This endosomal pathway spatially organizes GTP-RhoA to fine tune the activity of actomyosin resulting in polarized cell shape and development of intracellular stiffness and traction forces. Impairment of GTP-RhoA endosomal trafficking either by silencing EpCAM or by expressing Rab35/EHD1 mutants prevents proper myosin-II activity, stress fiber formation and ultimately cell polarization. Collectively, this work shows that the coupling between co-trafficking of EpCAM and RhoA, and actomyosin rearrangement is pivotal for cell spreading, and advances our understanding of how biochemical and mechanical properties promote cell plasticity.

Lung Endothelial Transcytosis

Transcytosis of macromolecules through lung endothelial cells is the primary route of transport from the vascular compartment into the interstitial space. Endothelial transcytosis is mostly a caveolae-dependent process that combines receptor-mediated endocytosis, vesicle trafficking via actin-cytoskeletal remodeling, and SNARE protein directed vesicle fusion and exocytosis. Herein, we review the current literature on caveolae-mediated endocytosis, the role of actin cytoskeleton in caveolae stabilization at the plasma membrane, actin remodeling during vesicle trafficking, and exocytosis of caveolar vesicles. Next, we provide a concise summary of experimental methods employed to assess transcytosis. Finally, we review evidence that transcytosis contributes to the pathogenesis of acute lung injury. © 2020 American Physiological Society. Compr Physiol 10:491-508, 2020.

The multifarious regulation of the apical junctional complex

Epithelial cells form highly organized polarized sheets with characteristic cell morphologies and tissue architecture. Cell–cell adhesion and intercellular communication are prerequisites of such cohesive sheets of cells, and cell connectivity is mediated through several junctional assemblies, namely desmosomes, adherens, tight and gap junctions. These cell–cell junctions form signalling hubs that not only mediate cell–cell adhesion but impact on multiple aspects of cell behaviour, helping to coordinate epithelial cell shape, polarity and function. This review will focus on the tight and adherens junctions, constituents of the apical junctional complex, and aims to provide a comprehensive overview of the complex signalling that underlies junction assembly, integrity and plasticity.

Catharmus tinctorius volatile oil promote the migration of mesenchymal stem cells via ROCK2/Myosin light chain signaling

MSC transplantation has been explored as a new clinical approach to stem cell-based therapies for bone diseases in regenerative medicine due to their osteogenic capability. However, only a small population of implanted MSC could successfully reach the injured areas. Therefore, enhancing MSC migration could be a beneficial strategy to improve the therapeutic potential of cell transplantation. Catharmus tinctorius volatile oil (CTVO) was found to facilitate MSC migration. Further exploration of the underlying molecular mechanism participating in the pro-migratory ability may provide a novel strategy to improve MSC transplantation efficacy. This study indicated that CTVO promotes MSC migration through enhancing ROCK2 mRNA and protein expressions. MSC migration induced by CTVO was blunted by ROCK2 inhibitor, which also decreased myosin light chain (MLC) phosphorylation. Meanwhile, the siRNA for ROCK2 inhibited the effect of CTVO on MSC migration ability and attenuated MLC phosphorylation, suggesting that CTVO may promote BMSC migration via the ROCK2/MLC signaling. Taken together, this study indicates that C. tinctorius volatile oil could enhance MSC migration via ROCK2/MLC signaling in vitro. C. tinctorius volatile oil-targeted therapy could be a beneficial strategy to improve the therapeutic potential of cell transplantation for bone diseases in regenerative medicine.

Propofol Inhibits the Migration and Invasion of Glioma Cells by Blocking the PI3K/AKT Pathway Through miR-206/ROCK1 Axis

Background

Propofol has been identified to perform anti-tumor functions in glioma. However, the molecular mechanisms underlying propofol-induced prevention on migration and invasion of glioma cells remain unclear.

Methods

Cell proliferation, invasion and migration were measured by 3-(4,5)-dimethylthiahiazo(−z-y1)-3,5-di-phenytetrazoliumromide assay and transwell assay, respectively. The expression of microRNA (miR)-206 and Rho-associated coiled coil-containing protein kinase 1 (ROCK1) was detected by quantitative real-time polymerase chain reaction. Western blot was used to measure the activation of the PI3K/AKT pathway. The interaction between miR-206 and ROCK1 was analyzed using the dual-luciferase reporter assay, RNA immunoprecipitation assay, and pull-down assay.

Results

Propofol treatment inhibited the migration, invasion, and PI3K/AKT pathway activation in glioma cells. MiR-206 was decreased in glioma tissues and cells, while propofol exposure induced the upregulation of miR-206 in glioma cells. Besides that, we also found overexpressed miR-206 enhanced propofol-mediated inhibition on the migration, invasion, and PI3K/AKT pathway activation of glioma cells. Subsequently, ROCK1 was confirmed to be a target of miR-206. ROCK1 was elevated in glioma tissues and cells, but was reduced by propofol exposure in glioma cells. The rescue assay indicated that the miR-206/ROCK1 axis was involved in propofol-induced inhibition on the migration, invasion, and PI3K/AKT pathway activation in glioma cells.

Conclusion

Propofol inhibited the migration and invasion of glioma cells by blocking the PI3K/AKT pathway through the miR-206/ROCK1 axis, suggesting an effective clinical implication for the anesthetic to prevent the metastasis of glioma.

Identification of genes involved in glaucoma pathogenesis using combined network analysis and empirical studies

Glaucoma is a leading cause of blindness. We aimed in this study to identify genes that may make subtle and cumulative contributions to glaucoma pathogenesis. To this end, we identified molecular interactions and pathways that include transcription factors (TFs) FOXC1, PITX2, PAX6 and NFKB1 and various microRNAs including miR-204 known to have relevance to trabecular meshwork (TM) functions and/or glaucoma. TM tissue is involved in glaucoma pathogenesis. In-house microarray transcriptome results and data sources were used to identify target genes of the regulatory molecules. Bioinformatics analyses were done to filter TM and glaucoma relevant genes. These were submitted to network-creating softwares to define interactions, pathways and a network that would include the genes. The network was stringently scrutinized and minimized, then expanded by addition of microarray data and data on TF and microRNA-binding sites. Selected features of the network were confirmed by empirical studies such as dual luciferase assays, real-time PCR and western blot experiments and apoptosis assays. MYOC, WDR36, LTPBP2, RHOA, CYP1B1, OPA1, SPARC, MEIS2, PLEKHG5, RGS5, BBS5, ALDH1A1, NOMO2, CXCL6, FMNL2, ADAMTS5, CLOCK and DKK1 were among the genes included in the final network. Pathways identified included those that affect ECM properties, IOP, ciliary body functions, retinal ganglion cell viability, apoptosis, focal adhesion and oxidative stress response. The identification of many genes potentially involved in glaucoma pathology is consistent with its being a complex disease. The inclusion of several known glaucoma-related genes validates the approach used.

Smoking as an Independent Risk Factor for Hepatocellular Carcinoma Due to the α7-Nachr Modulating the JAK2/STAT3 Signaling Axis

BACKGROUND

Hepatocellular carcinoma (HCC) is a worldwide health problem. Currently, there is no effective clinical therapeutic strategy for HCC. Smoking is associated with several malignant diseases including cancers.

EXPERIMENTAL APPROACH

However, the impact of smoking on HCC is still unresolved. Retrospectively reviewed HCC patients diagnosed between 1 January 2010 and 31 December 2015 at Taipei Medical University-Shuang Ho Hospital (Ministry of Health and Welfare). We found that smoking was associated with a poor prognosis, especially recurrence and patient survival after curative surgery using a clinicopathological analysis.

RESULTS

Our univariate and multivariate analyses showed that the α7-nicotinic acetylcholine receptor (α7-nAChR) was an oncogene and risk factor for post-resection recurrence. The α7-nAChR was overexpressed in HCC tissues compared to their non-tumor counterparts. Silencing the α7-nAChR reduced the viability of HCC cells, suppressed cellular proliferation, attenuated migration and invasion, and diminished the tumor's sphere-formation ability, with concurrent downregulation of expression levels of the TGR5, p-JAK2, p-STAT3 (Tyr705/Ser727), RhoA, ROCK1, MMP2, and MMP9 proteins. Furthermore, a positive correlation was found between α7-nAChR and JAK2 expressions (p = 0.01) in HCC specimens, as well as their membranous co-localization.

CONCLUSION

Together, we demonstrated that the α7-nAChR may be an independent prognosticator of the progression and prognosis of HCC patients. These findings suggest that the α7-nAChR drives the progression and recurrence of HCC through JAK2/STAT3 signaling and is a novel target for anti-HCC therapy.

ROCK isoforms differentially modulate cancer cell motility by mechanosensing the substrate stiffness

Tumors are characterized by extracellular matrix (ECM) remodeling and stiffening. The importance of ECM stiffness in cancer is well known. However, the biomechanical behavior of tumor cells and the underlying mechanotransduction pathways remain unclear. Here, we used polyacrylamide (PAA) substrates to simulate tissue stiffness at different progress stages of breast cancer in vitro, and we observed that moderate substrate stiffness promoted breast cancer cell motility. The substrate stiffness directly activated integrin β1 and focal adhesion kinase (FAK), which accelerate focal adhesion (FA) maturation and induce the downstream cascades of intracellular signals of the RhoA/ROCK pathway. Interestingly, the differential regulatory mechanism between two ROCK isoforms (ROCK1 and ROCK2) in cell motility and mechanotransduction was clearly identified. ROCK1 phosphorylated the myosin regulatory light chain (MRLC) and facilitated the generation of traction force, while ROCK2 phosphorylated cofilin and regulated the cytoskeletal remodeling by suppressing F-actin depolymerization. The ROCK isoforms differentially regulated the pathways of RhoA/ROCK1/p-MLC and RhoA/ROCK2/p-cofilin in a coordinate fashion to modulate breast cancer cell motility in a substrate stiffness-dependent manner through integrin β1-activated FAK signaling. Our findings provide new insights into the mechanisms of matrix mechanical property-induced cancer cell migration and malignant behaviors. STATEMENT OF SIGNIFICANCE: Here, we examined the relationship between substrate stiffness and tumor cellular motility by using polyacrylamide (PAA) substrates to simulate the stages in vivo of breast cancer. The results elucidated the different regulatory roles between the two ROCK isoforms in cell motility and demonstrated that stiff substrate (38 kPa) mediated RhoA/ROCK1/p-MLC and RhoA/ROCK2/p-cofilin pathways through integrin β1-FAK activation and eventually promoted directional migration. Our discoveries would have significant implications in the understanding of the interaction between cancer cells and tumor microenvironments, and hence, it might provide new insights into the metastasis inhibition, which could be an adjuvant way of cancer therapy.

Cellular senescence is associated with reorganization of the microtubule cytoskeleton

Senescent cells undergo structural and functional changes that affect essentially every aspect of cell physiology. To date, the impact of senescence on the cytoskeleton is poorly understood. This study evaluated the cytoskeleton in two independent cellular models of kidney epithelium senescence. Our work identified multiple senescence-related alterations that impact microtubules and filamentous actin during interphase. Both filamentous systems reorganized profoundly when cells became senescent. As such, microtubule stability increased during senescence, making these filaments more resistant to disassembly in the cold or by nocodazole. Microtubule stabilization was accompanied by enhanced α-tubulin acetylation on lysine 40 and the depletion of HDAC6, the major deacetylase for α-tubulin lysine 40. Rho-associated kinase Rock1 is an upstream regulator that modulates key properties of the cytoplasmic cytoskeleton. Our research shows that Rock1 concentrations were reduced significantly in senescent cells, and we revealed a mechanistic link between microtubule stabilization and Rock1 depletion. Thus, Rock1 overexpression partially restored the cold sensitivity of microtubules in cells undergoing senescence. Additional components relevant to microtubules were affected by senescence. Specifically, we uncovered the senescence-related loss of the microtubule nucleating protein γ-tubulin and aberrant formation of γ-tubulin foci. Concomitant with the alterations of microtubule and actin filaments, senescent cells displayed functional changes. In particular, cell migration was impaired significantly in senescent cells. Taken together, our study identified new senescence-associated deficiencies of the microtubule and actin cytoskeleton, provided insights into the underlying molecular mechanisms and demonstrated functional consequences that are important to the physiology and function of renal epithelial cells.

Anillin regulates epithelial cell mechanics by structuring the medial-apical actomyosin network

Cellular forces sculpt organisms during development, while misregulation of cellular mechanics can promote disease. Here, we investigate how the actomyosin scaffold protein anillin contributes to epithelial mechanics in Xenopus laevis embryos. Increased mechanosensitive recruitment of vinculin to cell-cell junctions when anillin is overexpressed suggested that anillin promotes junctional tension. However, junctional laser ablation unexpectedly showed that junctions recoil faster when anillin is depleted and slower when anillin is overexpressed. Unifying these findings, we demonstrate that anillin regulates medial-apical actomyosin. Medial-apical laser ablation supports the conclusion that that tensile forces are stored across the apical surface of epithelial cells, and anillin promotes the tensile forces stored in this network. Finally, we show that anillin's effects on cellular mechanics impact tissue-wide mechanics. These results reveal anillin as a key regulator of epithelial mechanics and lay the groundwork for future studies on how anillin may contribute to mechanical events in development and disease.

miR-133: A Suppressor of Cardiac Remodeling?

Cardiac remodeling, which is characterized by mechanical and electrical remodeling, is a significant pathophysiological process involved in almost all forms of heart diseases. MicroRNAs (miRNAs) are a group of non-coding RNAs of 20–25 nucleotides in length that primarily regulate gene expression by promoting mRNA degradation or post-transcriptional repression in a sequence-specific manner. Three miR-133 genes have been identified in the human genome, miR-133a-1, miR-133a-2, and miR-133b, which are located on chromosomes 18, 20, and 6, respectively. These miRNAs are mainly expressed in muscle tissues and appear to repress the expression of non-muscle genes. Based on accumulating evidence, miR-133 participates in the proliferation, differentiation, survival, hypertrophic growth, and electrical conduction of cardiac cells, which are essential for cardiac fibrosis, cardiac hypertrophy, and arrhythmia. Nevertheless, the roles of miR-133 in cardiac remodeling are ambiguous, and the mechanisms are also sophisticated, involving many target genes and signaling pathways, such as RhoA, MAPK, TGFβ/Smad, and PI3K/Akt. Therefore, in this review, we summarize the critical roles of miR-133 and its potential mechanisms in cardiac remodeling.

Cerebral Cavernous Malformation 1/2 complex controls ROCK1 and ROCK2 complementary functions for endothelial integrity

Endothelial integrity relies on a mechanical crosstalk between intercellular and cell-matrix interactions. This cross-talk is compromised in hemorrhagic vascular lesions of patients carrying loss-of-function mutations in CCM genes. RhoA/ROCK-dependent cytoskeletal remodeling is central to the disease as it causes unbalanced cell adhesion towards increased cell-extracellular matrix adhesions and destabilized cell-cell junctions. Our study reveals that CCM proteins directly orchestrate ROCK1 and ROCK2 complementary roles on the mechanics of the endothelium. CCM proteins act as a scaffold promoting ROCK2 interactions with VE-cadherin and limiting ROCK1 kinase activity. Loss of CCM1 produces excessive ROCK1-dependent actin stress fibers and destabilizes intercellular junctions. Silencing of ROCK1 but not ROCK2 restores the adhesive and mechanical homeostasis of CCM1/2-depleted endothelial monolayers and rescues cardiovascular defects of ccm1 mutant zebrafish embryos. Conversely, knocking down of Rock2 but not Rock1 in WT zebrafish embryos generates defects reminiscent of the ccm1 mutant phenotypes. Our study uncovers the role of the CCM complex in controlling ROCK1 and ROCK2 to preserve endothelial integrity and drive heart morphogenesis. Moreover, it identifies solely the ROCK1 isoform as therapeutic target for the CCM disease.

Activation of ROCK and MLCK tunes regional stress fiber formation and mechanics via preferential myosin light chain phosphorylation

Graded induction of regulatory light chain (RLC) activators MLCK and ROCK were used to explore the relationship between RLC phosphorylation and actin-myosin stress fiber viscoelasticity. MLCK controls peripheral stress fiber mechanics by monophosphorylation of RLC, whereas ROCK acts on central stress fibers via diphosphorylation.

The assembly and mechanics of actomyosin stress fibers (SFs) depend on myosin regulatory light chain (RLC) phosphorylation, which is driven by myosin light chain kinase (MLCK) and Rho-associated kinase (ROCK). Although previous work suggests that MLCK and ROCK control distinct pools of cellular SFs, it remains unclear how these kinases differ in their regulation of RLC phosphorylation or how phosphorylation influences individual SF mechanics. Here, we combine genetic approaches with biophysical tools to explore relationships between kinase activity, RLC phosphorylation, SF localization, and SF mechanics. We show that graded MLCK overexpression increases RLC monophosphorylation (p-RLC) in a graded manner and that this p-RLC localizes to peripheral SFs. Conversely, graded ROCK overexpression preferentially increases RLC diphosphorylation (pp-RLC), with pp-RLC localizing to central SFs. Interrogation of single SFs with subcellular laser ablation reveals that MLCK and ROCK quantitatively regulate the viscoelastic properties of peripheral and central SFs, respectively. The effects of MLCK and ROCK on single-SF mechanics may be correspondingly phenocopied by overexpression of mono- and diphosphomimetic RLC mutants. Our results point to a model in which MLCK and ROCK regulate peripheral and central SF viscoelastic properties through mono- and diphosphorylation of RLC, offering new quantitative connections between kinase activity, RLC phosphorylation, and SF viscoelasticity.

Rho GTPases and actomyosin: Partners in regulating epithelial cell-cell junction structure and function

Epithelial tissues are defined by polarized epithelial cells that are integrated into tissues and exhibit barrier function in order to regulate what is allowed to pass between cells. Cell-cell junctions must be stable enough to promote barrier function and tissue integrity, yet plastic enough to remodel when necessary. This remarkable ability to dynamically sense and respond to changes in cell shape and tissue tension allows cell-cell junctions to remain functional during events that disrupt epithelial homeostasis including morphogenesis, wound healing, and cell division. In order to achieve this plasticity, both tight junctions and adherens junctions are coupled to the underlying actomyosin cytoskeleton. Here, we discuss the importance of the junctional linkage to actomyosin and how a localized zone of active RhoA along with other Rho GTPases work together to orchestrate junctional actomyosin dynamics. We focus on how scaffold proteins help coordinate Rho GTPases, their upstream regulators, and their downstream effectors for efficient, localized Rho GTPase signaling output. Additionally, we highlight important roles junctional actin-binding proteins play in addition to their traditional roles in organizing actin. Together, Rho GTPases, their regulators, and effectors form compartmentalized signaling modules that regulate actomyosin structure and contractility to achieve proper cell-cell adhesion and tissue barriers.

Bistable front dynamics in a contractile medium: Travelling wave fronts and cortical advection define stable zones of RhoA signaling at epithelial adherens junctions

Mechanical coherence of cell layers is essential for epithelia to function as tissue barriers and to control active tissue dynamics during morphogenesis. RhoA signaling at adherens junctions plays a key role in this process by coupling cadherin-based cell-cell adhesion together with actomyosin contractility. Here we propose and analyze a mathematical model representing core interactions involved in the spatial localization of junctional RhoA signaling. We demonstrate how the interplay between biochemical signaling through positive feedback, combined with diffusion on the cell membrane and mechanical forces generated in the cortex, can determine the spatial distribution of RhoA signaling at cell-cell junctions. This dynamical mechanism relies on the balance between a propagating bistable signal that is opposed by an advective flow generated by an actomyosin stress gradient. Experimental observations on the behavior of the system when contractility is inhibited are in qualitative agreement with the predictions of the model.