Ursolic acid reverses liver fibrosis by inhibiting interactive NOX4/ROS and RhoA/ROCK1 signalling pathways

Liver fibrosis is the reversible deposition of extracellular matrix (ECM) and scar formation after liver damage by various stimuli. The interaction between NOX4/ROS and RhoA/ROCK1 in liver fibrosis is not yet clear. Ursolic acid (UA) is a traditional Chinese medicine with anti-fibrotic effects, but the molecular mechanism underlying these effects is still unclear. We investigated the interaction between NOX4/ROS and RhoA/ROCK1 during liver fibrosis and whether these molecules are targets for the anti-fibrotic effects of UA. First, we confirmed that UA reversed CCl4-induced liver fibrosis. In the NOX4 intervention and RhoA intervention groups, related experimental analyses confirmed the decrease in CCl4-induced liver fibrosis. Next, we determined that the expression of NOX4 and RhoA/ROCK1 was decreased in UA-treated liver fibrotic mice. Furthermore, RhoA/ROCK1 expression was decreased in the NOX4 intervention group, but there was no significant change in the expression of NOX4 in the RhoA intervention group. Finally, we found that liver fibrotic mice showed a decline in their microbiota diversity and abundance, a change in their microbiota composition, and a reduction in the number of potential beneficial bacteria. However, in UA-treated liver fibrotic mice, the microbiota dysbiosis was ameliorated. In conclusion, the NOX4/ROS and RhoA/ROCK1 signalling pathways are closely linked to the development of liver fibrosis. UA can reverse liver fibrosis by inhibiting the NOX4/ROS and RhoA/ROCK1 signalling pathways, which may interact with each other.

Syndecan-4 tunes cell mechanics by activating the kindlin-integrin-RhoA pathway

Extensive research over the past decades has identified integrins to be the primary transmembrane receptors that enable cells to respond to external mechanical cues. We reveal here a mechanism whereby syndecan-4 tunes cell mechanics in response to localized tension via a coordinated mechanochemical signalling response that involves activation of two other receptors: epidermal growth factor receptor and β1 integrin. Tension on syndecan-4 induces cell-wide activation of the kindlin-2/β1 integrin/RhoA axis in a PI3K-dependent manner. Furthermore, syndecan-4-mediated tension at the cell-extracellular matrix interface is required for yes-associated protein activation. Extracellular tension on syndecan-4 triggers a conformational change in the cytoplasmic domain, the variable region of which is indispensable for the mechanical adaptation to force, facilitating the assembly of a syndecan-4/α-actinin/F-actin molecular scaffold at the bead adhesion. This mechanotransduction pathway for syndecan-4 should have immediate implications for the broader field of mechanobiology.

The sphingosine-1-phosphate/RhoA/Rho associated kinases/myosin light chain pathway in detrusor of female rats is down-regulated in response to ovariectomy

BACKGROUND

Dysuria is one of the main symptoms of genitourinary syndrome of menopause, which causes serious disruption to the normal life of peri-menopausal women. Studies have shown that it is related to decrease of detrusor contractile function, but the exact mechanism is still poorly understood. Previous results have suggested that the sphingosine-1-phosphate (S1P) pathway can regulate detrusor contraction, and this pathway is affected by estrogen in various tissues. However, how estrogen affects this pathway in the detrusor has not been investigated. In this study, we detected changes of the S1P/RhoA/Rho associated kinases (ROCK)/myosin light chain (MLC) pathway in the detrusor of ovariectomized rats in order to explore the underlying mechanism of dysuria during peri-menopause.

METHODS

Thirty-six female Sprague-Dawley rats were randomly divided into SHAM (sham operation), OVX (ovariectomy), and E groups (ovariectomy + estrogen), with 12 rats in each group. We obtained bladder detrusor tissues from each group and examined the mRNA and protein levels of the major components of the S1P/RhoA/ROCK/MLC pathway using quantitative real-time polymerase chain reaction and Western blotting, respectively. We also quantified the content of S1P in the detrusor using an enzyme linked immunosorbent assay. Finally, we compared results between the groups with one-way analysis of variance.

RESULTS

The components of the S1P pathway and the RhoA/ROCK/MLC pathway of the OVX group were significantly decreased, as compared with SHAM group. The percent decreases of the components in the S1P pathway were as follows: sphingosine kinase 1 (mRNA: 39%, protein: 45%) (both P < 0.05), S1P (21.73 ± 1.09 nmol/g vs. 18.86 ± 0.69 nmol/g) (P < 0.05), and S1P receptor 2/3 (S1PR2/3) (mRNA: 25%, 27%, respectively) (P < 0.05). However, the protein expression levels of S1PR2/3 and the protein and mRNA levels of SphK2 and S1PR1 did not show significant differences between groups (P > 0.05). The percent decreases of the components in the RhoA/ROCK/MLC pathway were as follows: ROCK2 (protein: 41%, mRNA: 36%) (both P < 0.05), p-MYPT1 (protein: 54%) (P < 0.05), and p-MLC20 (protein: 47%) (P < 0.05), but there were no significant differences in the mRNA and protein levels of RhoA, ROCK1, MYPT1, and MLC20 (all P > 0.05). In addition, all of the above-mentioned decreases could be reversed after estrogen supplementation (E group vs. SHAM group) (all P > 0.05).

CONCLUSION

In this study, we confirmed that ovariectomy is closely associated with the down-regulation of the S1P/RhoA/ROCK/MLC pathway in the rat detrusor, which may be one mechanism of dysuria caused by decreased contractile function of the female detrusor during peri-menopause.

Ligand Binding to the Collagen VI Receptor Triggers a Talin-to-RhoA Switch that Regulates Receptor Endocytosis

Capillary morphogenesis gene 2 (CMG2/ANTXR2) is a cell surface receptor for both collagen VI and anthrax toxin. Biallelic loss-of-function mutations in CMG2 lead to a severe condition, hyaline fibromatosis syndrome (HFS). We have here dissected a network of dynamic interactions between CMG2 and various actin interactors and regulators, describing a different behavior from other extracellular matrix receptors. CMG2 binds talin, and thereby the actin cytoskeleton, only in its ligand-free state. Extracellular ligand binding leads to src-dependent talin release and recruitment of the actin cytoskeleton regulator RhoA and its effectors. These sequential interactions of CMG2 are necessary for the control of oriented cell division during fish development. Finally, we demonstrate that effective switching between talin and RhoA binding is required for the intracellular degradation of collagen VI in human fibroblasts, which explains why HFS mutations in the cytoskeleton-binding domain lead to dysregulation of extracellular matrix homeostasis.

Omega-3 polyunsaturated fatty acids impinge on CD4+ T cell motility and adipose tissue distribution via direct and lipid mediator-dependent effects

AIMS

Adaptive immunity contributes to the pathogenesis of cardiovascular metabolic disorders (CVMD). The omega-3 polyunsaturated fatty acids (n-3PUFA) are beneficial for cardiovascular health, with potential to improve the dysregulated adaptive immune responses associated with metabolic imbalance. We aimed to explore the mechanisms through which n-3PUFA may alter T cell motility and tissue distribution to promote a less inflammatory environment and improve lymphocyte function in CVMD.

METHODS AND RESULTS

Using mass spectrometry lipidomics, cellular, biochemical, and in vivo and ex vivo analyses, we investigated how eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), the main n-3PUFA, modify the trafficking patterns of activated CD4+ T cells. In mice subjected to allogeneic immunization, a 3-week n-3PUFA-enriched diet reduced the number of effector memory CD4+ T cells found in adipose tissue, and changed the profiles of eicosanoids, octadecanoids, docosanoids, endocannabinoids, 2-monoacylglycerols, N-acyl ethanolamines, and ceramides, in plasma, lymphoid organs, and fat tissues. These bioactive lipids exhibited differing chemotactic properties when tested in chemotaxis assays with activated CD4+ T cells in vitro. Furthermore, CD4+ T cells treated with EPA and DHA showed a significant reduction in chemokinesis, as assessed by trans-endothelial migration assays, and, when implanted in recipient mice, demonstrated less efficient migration to the inflamed peritoneum. Finally, EPA and DHA treatments reduced the number of polarized CD4+ T cells in vitro, altered the phospholipid composition of membrane microdomains and decreased the activity of small Rho GTPases, Rhoα, and Rac1 instrumental in cytoskeletal dynamics.

CONCLUSIONS

Our findings suggest that EPA and DHA affect the motility of CD4+ T cells and modify their ability to reach target tissues by interfering with the cytoskeletal rearrangements required for cell migration. This can explain, at least in part, the anti-inflammatory effects of n-3PUFA supporting their potential use in interventions aiming to address adipocyte low-grade inflammation associated with cardiovascular metabolic disease.

ER stress induced by ER calcium depletion and UVB irradiation regulates tight junction barrier integrity in human keratinocytes

BACKGROUND

Endoplasmic reticulum (ER) calcium depletion-induced ER stress is a crucial signal for keratinocyte differentiation and barrier homeostasis, but its effects on the epidermal tight junction (TJ) have not been characterized. Ultraviolet B (UVB) causes ER calcium release in keratinocytes and disrupts epidermal TJ, however, the involvement of ER stress in the UVB-induced TJ alterations remains unknown.

OBJECTIVES

To investigate the effect of ER stress by pharmacological ER calcium depletion or UVB on the TJ integrity in normal human epidermal keratinocytes (NHEK).

METHODS

NHEK were exposed to ER calcium pump inhibitor thapsigargin (Tg) or UVB. ER stress markers and TJ molecules expression, TJ and F-actin structures, and TJ barrier function were analyzed.

RESULTS

Tg or UVB exposure dose-dependently triggered unfolded protein response (UPR) in NHEK. Low dose Tg induced the IRE1α-XBP1 pathway and strengthened TJ barrier. Contrary, high dose Tg activated PERK phosphorylation and disrupted TJ by F-actin disorganization. UVB disrupted TJ and F-actin structures dose dependently. IRE1α RNase inhibition induced or exacerbated TJ and F-actin disruption in the presence of low dose Tg or UVB. High dose Tg increased RhoA activity. 4-PBA or Rho kinase (ROCK) inhibitor partially prevented the disruption of TJ and F-actin following high dose Tg or UVB.

CONCLUSIONS

ER stress has bimodal effects on the epidermal TJ depending on its intensity. The IRE1α pathway is critical for the maintenance of TJ integrity during mild ER stress. Severe ER stress-induced UPR or ROCK signalling mediates the disruption of TJ through cytoskeletal disorganization during severe ER stress.

Impact of RhoA overexpression on clinical outcomes in cervical squamous cell carcinoma treated with concurrent chemoradiotherapy

The Rho-associated coiled-coil-containing protein kinase (ROCK) pathway is known to influence metastasis in several cancers; however, the impact of the pathway on clinical outcomes in patients undergoing radiotherapy remains unknown. In the present study, the expression of RhoA, RhoC, ROCK-1, ROCK-2 and p53 was immunohistochemically evaluated using biopsy specimens obtained from 49 patients with stage II-III cervical squamous cell carcinoma treated with concurrent chemoradiotherapy (CCRT). The relationship between the expression of these proteins and patient outcomes was investigated. RhoA overexpression was associated with significantly impaired disease-free survival and distant metastasis-free survival (P = 0.045 and P = 0.041, respectively) in stage III cancer patients. No differences in survival were observed based on the expression of the other proteins among stage III cancer patients. In stage II cancer patients, no differences in survival were noted based on the expression of any of the proteins. The expression of RhoA was able to successfully differentiate cervical cancer patients with distant metastasis after CCRT. This information may help stratify patients according to the risk of metastasis, thereby leading to the potential to provide individualized treatment.

ILK supports RhoA/ROCK-mediated contractility of human intestinal epithelial crypt cells by inducing the fibrillogenesis of endogenous soluble fibronectin during the spreading process

BACKGROUND

Fibronectin (FN) assembly into an insoluble fibrillar matrix is a crucial step in many cell responses to extracellular matrix (ECM) properties, especially with regards to the integrin-related mechanosensitive signaling pathway. We have previously reported that the silencing of expression of integrin-linked kinase (ILK) in human intestinal epithelial crypt (HIEC) cells causes significant reductions in proliferation and spreading through concomitantly acquired impairment of soluble FN deposition. These defects in ILK-depleted cells are rescued by growth on exogenous FN. In the present study we investigated the contribution of ILK in the fibrillogenesis of FN and its relation to integrin-actin axis signaling and organization.

RESULTS

We show that de novo fibrillogenesis of endogenous soluble FN is ILK-dependent. This function seemingly induces the assembly of an ECM that supports increased cytoskeletal tension and the development of a fully spread contractile cell phenotype. We observed that HIEC cell adhesion to exogenous FN or collagen-I (Col-I) is sufficient to restore fibrillogenesis of endogenous FN in ILK-depleted cells. We also found that optimal engagement of the Ras homolog gene family member A (RhoA) GTPase/Rho-associated kinase (ROCK-1, ROCK-2)/myosin light chain (MLC) pathway, actin ventral stress fiber formation, and integrin adhesion complex (IAC) maturation rely primarily upon the cell's capacity to execute FN fibrillogenesis, independent of any significant ILK input. Lastly, we confirm the integrin α5β1 as the main integrin responsible for FN assembly, although in ILK-depleted cells αV-class integrins expression is needed to allow the rescue of FN fibrillogenesis on exogenous substrate.

CONCLUSION

Our study demonstrates that ILK specifically induces the initiation of FN fibrillogenesis during cell spreading, which promotes RhoA/ROCK-dependent cell contractility and maturation of the integrin-actin axis structures. However, the fibrillogenesis process and its downstream effect on RhoA signaling, cell contractility and spreading are ILK-independent in human intestinal epithelial crypt cells.

Cancer Cells Resist Mechanical Destruction in Circulation via RhoA/Actomyosin-Dependent Mechano-Adaptation

During metastasis, cancer cells are exposed to potentially destructive hemodynamic forces including fluid shear stress (FSS) while en route to distant sites. However, prior work indicates that cancer cells are more resistant to brief pulses of high-level FSS in vitro relative to non-transformed epithelial cells. Herein, we identify a mechano-adaptive mechanism of FSS resistance in cancer cells. Our findings demonstrate that cancer cells activate RhoA in response to FSS, which protects them from FSS-induced plasma membrane damage. We show that cancer cells freshly isolated from mouse and human tumors are resistant to FSS, that formin and myosin II activity protects circulating tumor cells (CTCs) from destruction, and that short-term inhibition of myosin II delays metastasis in mouse models. Collectively, our data indicate that viable CTCs actively resist destruction by hemodynamic forces and are likely to be more mechanically robust than is commonly thought.

Annatto-Derived Tocotrienol Promotes Mineralization of MC3T3-E1 Cells by Enhancing BMP-2 Protein Expression via Inhibiting RhoA Activation and HMG-CoA Reductase Gene Expression

PURPOSE

Annatto-derived tocotrienol (AnTT) has been shown to improve bone formation in animal models of osteoporosis and promote differentiation of pre-osteoblastic cells. However, the mechanism of action of AnTT in achieving these effects is unclear. This study aims to investigate the mechanism of action of AnTT on MC3T3-E1 pre-osteoblasts via the mevalonate pathway.

METHODS

Murine pre-osteoblastic cells, MC3T3-E1, were cultured with the density of 1 × 104 cells/mL and treated with 4 concentrations of AnTT (0.001-1 µg/mL). Expression of HMG-CoA reductase (HMGR) gene was carried out using qPCR after treatment with AnTT for 21 days. RhoA activation and bone morphogenetic protein-2 (BMP-2) were measured using immunoassay after 9 and 15 days of AnTT treatment. Lovastatin was used as the positive control. Mineralized nodules were detected using Von Kossa staining after 21 days of AnTT treatment.

RESULTS

The results showed that HMGR was up-regulated in the lovastatin group on day 9 and 21 compared to the control. Lovastatin also inhibited RhoA activation (day 9 and 15) and increased BMP-2 protein (day 15). On the other hand, AnTT at 0.001 μg/mL (day 3) and 0.1 μg/mL (day 21) significantly down-regulated HMGR gene expression compared to the control. On day 21, HMGR gene expression was significantly reduced in all groups compared to day 15. AnTT at 0.1 μg/mL significantly decreased RhoA activation on day 9 compared to the control. AnTT at 1 μg/mL significantly increased BMP-2 protein on day 15 compared to the control (P<0.05). Mineralized calcium nodules were more abundant in AnTT treated groups compared to the control on day 21.

CONCLUSION

AnTT suppresses the mevalonate pathway by downregulating HMGR gene expression and inhibiting RhoA activation, leading to increased BMP-2 protein in MC3T3-E1 cells. This explains the stimulating effects of AnTT on osteoblast mineralization.

[TNF-α activates RhoA/ROCK signaling pathway and increases permeability of endothelial cells infected with Listeria monocytogenes]

Objective To investigate the role of Ras homolog gene (Rho) A/Rho-associated coiled-coil containing protein kinase (ROCK) signaling pathway in tumor necrosis factor α (TNF-α) promoting hyper-permeability of vascular endothelial cells infected by Listeria monocytogenes (Lm) . Methods The cultured human umbilical vein endothelial cells (HUVECs) were divided into a control group (uninfected cells), TNF-α treatment group (100 ng/mL TNF-α, for 2 hours), Lm infection group (infected with MOI=10 Lm for 2 hours, then added gentamicin for 0.5 hour), Lm infection and TNF-α treatment group (infected with Lm and then treated with 100 ng/mL TNF-α for 2 hours), and Y-27632 inhibitor group combined with Lm infection and TNF-α treatment (treated with 50 μmol/L ROCK inhibitor Y-27632 for 30 minutes, and then Lm infection and TNF-α treatment as above). The protein levels of RhoA, zonula occluden-1 (ZO-1), occludin and ROCK in HUVECs were detected by Western blot analysis; the permeability of HUVECs was analyzed by the horseradish peroxidase (HRP) leakage; and the distribution of F-actin in HUVECs was detected by fluorescein isothiocyanate (FITC)-labeled phalloidine staining. Results TNF-α reduced the expression of tight junction protein ZO-1 and occludin in Lm-infected HUVECs, promoted its hyper-permeability and cytoskeletal rearrangement, and up-regulated the expression of RhoA and ROCK. ROCK inhibitor Y-27632 obviously inhibited the cytoskeleton rearrangement and hyper-permeability of HUVECs induced by TNF-α. Conclusion TNF-α can enhance hyper-permeability of HUVECs infected by Lm, which may be regulated by RhoA/Rock signaling pathway.

Epigenetic silencing of microRNA-125b-5p promotes liver fibrosis in nonalcoholic fatty liver disease via integrin α8-mediated activation of RhoA signaling pathway

BACKGROUND

Nonalcoholic fatty liver disease (NAFLD) is one of the most common chronic liver diseases that may progress to liver fibrosis or cancer. The present study aimed to investigate the role of microRNA-125b-5p (miR-125b-5p) in NAFLD and to further explore underlying molecular mechanisms.

METHODS

A mouse model of NAFLD was constructed by high cholesterol diet feeding and a cell-model was developed by treating the mouse liver cell line NCTC1469 with palmitic acid. Gain- and loss-of-function experiments were performed to determine the effects of miR-125b-5p, integrin α8 (ITGA8), and the RhoA signaling pathway on liver fibrosis in NAFLD. After the expression levels of miR-125b-5p, ITGA8, and RhoA were determined, liver fibrosis was evaluated in vivo and in vitro. The binding relationship of miR-125b-5p and ITGA8 was then validated. Finally, miR-125b-5p promoter methylation in NAFLD liver tissues and cells was determined.

RESULTS

In NAFLD clinical samples, mouse model, and cell-model, miR-125b-5p expression was reduced, while ITGA8 expression was increased. Moreover, miR-125b-5p targeted and downregulated ITGA8, leading to inhibition of the RhoA signaling pathway. In NAFLD liver tissues and cells, the CpG island in the miR-125b-5p promoter was methylated, causing epigenetic silencing of miR-125b-5p. Both miR-125b-5p silencing and ITGA8 overexpression promoted in vitro and in vivo liver fibrosis in NAFLD via activation of the RhoA signaling pathway.

CONCLUSIONS

Collectively, epigenetic silencing of miR-125b-5p upregulates ITGA8 expression to activate the RhoA signaling pathway, leading to liver fibrosis in NAFLD.

The pyrin inflammasome in host-microbe interactions

Pyrin is an inflammasome sensor in phagocytes that is activated in response to bacterial toxins and effectors that modify RhoA. Pathogen effector-triggered pyrin activation is analogous to an indirect guard mechanism in plants. Pyrin activation appears to be triggered when RhoA GTPases in a host cell are prevented from binding downstream signaling proteins (transducers). RhoA transducers that control this response include PRK kinases, which negatively regulate pyrin by phosphorylation and binding of 14-3-3 proteins. Microtubules regulate pyrin at different levels and may serve as a platform for inflammasome nucleation. Pyrin increases inflammation in the lung, gut or systemically during infection or intoxication in mouse models and protects against systemic infection by decreasing bacterial loads. Pathogenic Yersinia spp. overcome this protective response using effectors that inhibit the pyrin inflammasome. Gain of function mutations in MEFV, the gene encoding pyrin, cause the autoinflammatory disease Familial Mediterranean Fever. Yersinia pestis may have selected for gain of function MEFV mutations in the human population.

Effects of dexamethasone on VEGF-induced MUC5AC expression in human primary bronchial epithelial cells: Implications for asthma

Mucins are major macromolecular components of lung mucus that are mainly responsible for the viscoelastic property of mucus. MUC5AC is a major mucin glycoprotein that is hypersecreted in asthmatic individuals. Vascular endothelial growth factor (VEGF) has been implicated in inflammatory and airway blood vessel remodeling in asthmatics. Our previous studies indicate that VEGF upregulates MUC5AC expression by interacting with VEGF receptor 2 (VEGFR2). It has been shown that dexamethasone (Dex) downregulates MUC5AC expression; however, the underlying mechanisms have not been completely elucidated. Therefore, we sought to investigate the effect of Dex on MUC5AC expression induced by VEGF and study the underlying mechanisms. We tested the effects of Dex on VEGFR2 and RhoA activation, caveolin-1 expression, and the association of caveolin-1 and VEGFR2 in primary bronchial epithelial cells. Dex downregulated MUC5AC mRNA and protein levels in a dose- and time-dependent manner, and suppressed the activation of VEGFR2 and RhoA induced by VEGF. Additionally, Dex upregulated caveolin-1 protein levels in a dose- and time-dependent manner. Furthermore, phospho-VEGFR2 expression was decreased through overexpression of caveolin-1 and increased after caveolin-1 knockdown. Dex treatment attenuated the VEGF-decreased association of caveolin-1 and VEGFR2. Collectively, our findings suggest that Dex downregulates VEGF-induced MUC5AC expression by inactivating VEGFR2 and RhoA. Furthermore, decreased MUC5AC expression by Dex was related to the increased association of caveolin-1 with VEGFR2. Further studies characterizing these mechanisms are required to facilitate the development of improved treatment strategies for asthma.

Cullin 3 overexpression inhibits lung cancer metastasis and is associated with survival of lung adenocarcinoma

Cullin 3 (CUL3), a molecular scaffold of Cullin-RING ubiquitin ligase, plays an important role in regulating biological processes through modulating the ubiquitylation and degradation of various protein substrates. Dysfunction of CUL3 is implicated in the development of several human diseases. However, the clinical significance and prognostic value of CUL3 in lung cancer have not been investigated. This study investigated the CUL3-modulating potential of non-small cell lung cancer cell lines, H1299, H358, H2170 and H520, by using immunoblotting, MTT, migration, invasion, colony formation and in vivo tumorigenicity assays. The prognostic significance of CUL3 was measured by public KM plotter database (http://kmplot.com/analysis/index.php?p=service&cancer=breast) and tissue immunohistochemistry analysis. The public online database analysis revealed that elevated mRNA expression of CUL3 was associated with better prognosis for non-small cell lung cancer and lung adenocarcinoma. In vitro experiments showed that ectopic overexpression of CUL3 significantly inhibited lung adenocarcinoma cell proliferation and migration, and the tumor-suppressive effect of CUL3 was dependent on the Nrf2/RhoA axis. In vivo mice model demonstrated that overexpression of CUL3 lead to a significant reduction of lung adenocarcinoma growth and metastasis. Importantly, tissue immunohistochemistry analysis showed that about 47% of non-small cell lung cancer tissues were expressed of CUL3 at high levels. Overexpression of CUL3 predicted favorable overall survival in non-small cell lung cancer patients, especially in lung adenocarcinoma, but not in lung squamous cell carcinoma patients. CUL3 could serve as a prognostic biomarker for lung adenocarcinoma. Loss of CUL3 might be driving tumorigenesis by activating the Nrf2/RhoA pathway.

Characterization of C3larvinA, a novel RhoA-targeting ADP-ribosyltransferase toxin produced by the honey bee pathogen, Paenibacillus larvae

C3larvinA is a putative virulence factor produced by Paenibacillus larvae enterobacterial-repetitive-intergenic-consensus (ERIC) III/IV (strain 11-8051). Biochemical, functional and structural analyses of C3larvinA revealed that it belongs to the C3-like mono-ADP-ribosylating toxin subgroup. Mammalian RhoA was the target substrate for its transferase activity suggesting that it may be the biological target of C3larvinA. The kinetic parameters of the NAD+ substrate for the transferase (KM = 75 ± 10 µM) and glycohydrolase (GH) (KM = 107 ± 20 µM) reactions were typical for a C3-like bacterial toxin, including the Plx2A virulence factor from Paenibacillus larvae ERIC I. Upon cytoplasmic expression in yeast, C3larvinA caused a growth-defective phenotype indicating that it is an active C3-like toxin and is cytotoxic to eukaryotic cells. The catalytic variant of the Q187-X-E189 motif in C3larvinA showed no cytotoxicity toward yeast confirming that the cytotoxicity of this factor depends on its enzymatic activity. A homology consensus model of C3larvinA with NAD+ substrate was built on the structure of Plx2A, provided additional confirmation that C3larvinA is a member of the C3-like mono-ADP-ribosylating toxin subgroup. A homology model of C3larvinA with NADH and RhoA was built on the structure of the C3cer-NADH-RhoA complex which provided further evidence that C3larvinA is a C3-like toxin that shares an identical catalytic mechanism with C3cer from Bacillus cereus. C3larvinA induced actin cytoskeleton reorganization in murine macrophages, whereas in insect cells, vacuolization and bi-nucleated cells were observed. These cellular effects are consistent with C3larvinA disrupting RhoA function by covalent modification that is shared among C3-like bacterial toxins.

Mechanical force regulation of YAP by F-actin and GPCR revealed by super-resolution imaging

The Hippo signaling pathway plays critical roles in many biological processes including mechanotransduction. The key activator YAP of this pathway is considered as a central component of mechanotransduction signaling sensing the extracellular mechanical microenvironment changes, such as different cell density, the architecture of tissues and matrix stiffness. Although it has been largely studied that YAP is involved in these processes, the underlying mechanism of mechanical force-induced YAP regulation remains unclear. Here we exerted pressure on cell surfaces and investigated how YAP senses the extracellular mechanical force change using one of the super-resolution imaging techniques, dSTORM. We demonstrated that pressure promoted F-actin depolymerization, RhoA down-regulation, and LPAR1 (Gα12/13-coupled receptor) inactivation, which led to YAP cytoplasmic translocation and decreased clustering. Our work uncovers the role of GPCRs and F-actin in pressure-controlled YAP inactivation, and provides new insights into the mechanisms of mechanical regulation of the Hippo signaling pathway.

RhoA Mediates Epithelial Cell Shape Changes via Mechanosensitive Endocytosis

Epithelial remodeling involves ratcheting behavior whereby periodic contractility produces transient changes in cell-cell contact lengths, which stabilize to produce lasting morphogenetic changes. Pulsatile RhoA activity is thought to underlie morphogenetic ratchets, but how RhoA governs transient changes in junction length, and how these changes are rectified to produce irreversible deformation, remains poorly understood. Here, we use optogenetics to characterize responses to pulsatile RhoA in model epithelium. Short RhoA pulses drive reversible junction contractions, while longer pulses produce irreversible junction length changes that saturate with prolonged pulse durations. Using an enhanced vertex model, we show this is explained by two effects: thresholded tension remodeling and continuous strain relaxation. Our model predicts that structuring RhoA into multiple pulses overcomes the saturation of contractility and confirms this experimentally. Junction remodeling also requires formin-mediated E-cadherin clustering and dynamin-dependent endocytosis. Thus, irreversible junction deformations are regulated by RhoA-mediated contractility, membrane trafficking, and adhesion receptor remodeling.

The clock gene Bmal1 inhibits macrophage motility, phagocytosis, and impairs defense against pneumonia

The circadian clock regulates many aspects of immunity. Bacterial infections are affected by time of day, but the mechanisms involved remain undefined. Here we show that loss of the core clock protein BMAL1 in macrophages confers protection against pneumococcal pneumonia. Infected mice show both reduced weight loss and lower bacterial burden in circulating blood. In vivo studies of macrophage phagocytosis reveal increased bacterial ingestion following Bmal1 deletion, which was also seen in vitro. BMAL1-/- macrophages exhibited marked differences in actin cytoskeletal organization, a phosphoproteome enriched for cytoskeletal changes, with reduced phosphocofilin and increased active RhoA. Further analysis of the BMAL1-/- macrophages identified altered cell morphology and increased motility. Mechanistically, BMAL1 regulated a network of cell movement genes, 148 of which were within 100 kb of high-confidence BMAL1 binding sites. Links to RhoA function were identified, with 29 genes impacting RhoA expression or activation. RhoA inhibition restored the phagocytic phenotype to that seen in control macrophages. In summary, we identify a surprising gain of antibacterial function due to loss of BMAL1 in macrophages, associated with a RhoA-dependent cytoskeletal change, an increase in cell motility, and gain of phagocytic function.

RhoA/Rock2/Limk1/cofilin1 pathway is involved in attenuation of neuronal dendritic spine loss by paeonol in the frontal cortex of D-galactose and aluminum‑induced Alzheimer's disease‑like rat model

Alzheimer's disease (AD) has become the most prevalent neurodegenerative disorder. Given the pathogenesis of AD is unclear, there is currently no drug approved to halt or delay the progression of AD. Therefore, it is pressing to explore new targets and drugs for AD. In China, polyphenolic Chinese herbal medicine has been used for thousands of years in clinical application, and no toxic effects have been reported. In the present study, using D‑galactose and aluminum‑induced rat model, the effects of paeonol on AD were validated via the Morris water maze test, open field test, and elevated plus maze test. Neuronal morphology in frontal cortex was assessed using ImageJ's Sholl plugin and RESCONSTRUCT software. RhoA/Rock2/Limk1/cofilin1 signaling pathway‑related molecules were determined by Western blotting. Cofilin1 and p‑cofilin1 were analyzed by immunofluorescence. Results showed that pre‑treatment with paeonol attenuated D‑galactose and aluminum‑induced behavioral dysfunction and AD‑like pathological alterations in the frontal cortex. Accompanied by these changes were the alterations in the dendrite and dendritic spine densities, especially the mushroom‑type and filopodia‑type spines in the apical dendrites, as well as actin filaments. In addition, the activity and intracellular distribution of cofilin1 and the molecules RhoA/Rock2/Limk1 that regulate the signaling pathway for cofilin1 phosphorylation have also changed. Our data suggests that paeonol may be through reducing Aβ levels to alleviate the loss of fibrillar actin and dendrites and dendritic spines via the Rho/Rock2/Limk1/cofilin1 signaling pathway in the frontal cortex, and ultimately improving AD‑like behavior.

Selenium Deficiency Affects Uterine Smooth Muscle Contraction Through Regulation of the RhoA/ROCK Signalling Pathway in Mice

Selenium (Se) is considered one of the essential micronutrients for humans and animals, and its effects on physiological functions are multifaceted. In the present study, we investigated the effects of Se deficiency on uterine smooth muscle contraction in mice by studying G protein Rho (RhoA)/Rho kinase (ROCK) signalling pathway-related molecules. The α-sma in smooth muscle tissue of mice was determined. The extracorporeal contraction curve for uterine smooth muscle in mice was determined. Both of these results indicate that Se deficiency impairs the contractile ability of uterine smooth muscle in mice. The expression of mRNA was measured by real-time quantitative PCR. The results showed that there was no significant change in mRNA expression of RhoA, ROCK, myosin light chain phosphatase (MLCP), or myosin light chain (MLC) in tissues. The protein levels were detected by Western blot. The results showed that there were no significant differences in RhoA, ROCK, MLCP, or MLC expression. However, compared with the CG, the concentration of phosphorylated MLC (P-MLC) increased in the SG and the concentration of P-MLC decreased in the DG. The activity of ROCK and MLCP was tested by liquid scintillation. The results suggest that the lack of Se may affect the regulation of MLCP by ROCK. Cellular experiments were performed to compare with results from tissues. There was no significant difference between the two models. The results indicated that Se deficiency affects uterine smooth muscle contraction by regulating the RhoA/ROCK signalling pathway. As the concentration of Se decreases, the activity of MLCP increases, which promotes the dephosphorylation of P-MLC, causing a decrease in contraction.

Paracrine signalling of AGR2 stimulates RhoA function in fibroblasts and modulates cell elongation and migration

The most prominent cancer-associated fibroblasts (CAFs) in tumor stroma is known to form a protective structure to support tumor growth. Anterior gradient-2 (AGR2), a tumor secretory protein is believed to play a pivotal role during tumor microenvironment (TME) development. Here, we report that extracellular AGR2 enhances fibroblasts elongation and migration significantly. The early stimulation of RhoA showed the association of AGR2 by upregulation of G1-S phase-regulatory protein cyclin D1 and FAK phosphorylation through fibroblasts growth factor receptor (FGFR) and vascular endothelial growth factor receptor (VEGFR). Our finding indicates that secretory AGR2 alters fibroblasts elongation, migration, and organization suggesting the secretory AGR2 as a potential molecular target that might be responsible to alter fibroblasts infiltration to support tumor growth.

Cdc42 is involved in NC1 peptide-regulated BTB dynamics through actin and microtubule cytoskeletal reorganization

Noncollagenous domain 1 (NC1)-peptide is a biologically active peptide derived from the C-terminal region of collagen α3(IV) chain, a structural constituent protein at the basement membrane in the rat testis, likely via proteolytic cleavage of matrix metalloproteinase 9. Studies have shown that this NC1 peptide regulates testis function by inducing Sertoli cell blood-testis barrier (BTB) remodeling and is also capable of inducing elongate spermatid exfoliation through its disruptive effects on the organization of actin- and microtubule (MT)-based cytoskeletons at these cell adhesion sites. However, the underlying molecular mechanism remains unknown. NC1 peptide was found to exert its biologic effects through an activation of small GTPase cell division control protein 42 homolog (Cdc42) because cooverexpression of the dominant negative mutant of Cdc42 [namely, Cdc42-T17N (via a single mutation of amino acid residue 17 from the N terminus from Thr to Asn by site-directed mutagenesis, making it constitutively inactive)] and NC1 peptide was able to block the NC1 peptide-induced Sertoli cell tight junction-permeability barrier disruption. Their cooverexpression also blocked the NC1 peptide-induced misdistribution of BTB-associated proteins at the cell-cell interface and also disruptive cytoskeletal organization of F-actin and MTs through changes in spatial expression of the corresponding actin and MT regulatory proteins. Interestingly, NC1 peptide was also found to induce an up-regulation of phosphorylated (p)-ribosomal protein S6 (rpS6) (namely, p-rpS6-S235/S236) and a concomitant down-regulation of p-Akt1/2 (namely, p-Akt1-S473 and p-Akt2-S474), but these changes could not be blocked by overexpression of Cdc42-T17N. More importantly, NC1 peptide-induced Cdc42 activation was effectively blocked by treatment of Sertoli cell epithelium with a p-Akt1/2 activator SC79, which is also capable of blocking NC1 peptide-induced down-regulation of p-Akt1-S473 and p-Akt2/S474, but not p-rpS6-S235/S236 up-regulation. In summary, these findings illustrate that Cdc42 is working downstream of the mammalian target of rapamycin complex 1/rpS6/Akt1/2 signaling pathway to support NC1 peptide-mediated effects on Sertoli cell function in the testis using the rat as an animal model.-Su, W., Cheng, C. Y. Cdc42 is involved in NC1 peptide-regulated BTB dynamics through actin and microtubule cytoskeletal reorganization.

N-WASP Control of LPAR1 Trafficking Establishes Response to Self-Generated LPA Gradients to Promote Pancreatic Cancer Cell Metastasis

Pancreatic ductal adenocarcinoma is one of the most invasive and metastatic cancers and has a dismal 5-year survival rate. We show that N-WASP drives pancreatic cancer metastasis, with roles in both chemotaxis and matrix remodeling. lysophosphatidic acid, a signaling lipid abundant in blood and ascites fluid, is both a mitogen and chemoattractant for cancer cells. Pancreatic cancer cells break lysophosphatidic acid down as they respond to it, setting up a self-generated gradient driving tumor egress. N-WASP-depleted cells do not recognize lysophosphatidic acid gradients, leading to altered RhoA activation, decreased contractility and traction forces, and reduced metastasis. We describe a signaling loop whereby N-WASP and the endocytic adapter SNX18 promote lysophosphatidic acid-induced RhoA-mediated contractility and force generation by controlling lysophosphatidic acid receptor recycling and preventing degradation. This chemotactic loop drives collagen remodeling, tumor invasion, and metastasis and could be an important target against pancreatic cancer spread.

Membrane Tension Orchestrates Rear Retraction in Matrix-Directed Cell Migration

In development, wound healing, and cancer metastasis, vertebrate cells move through 3D interstitial matrix, responding to chemical and physical guidance cues. Protrusion at the cell front has been extensively studied, but the retraction phase of the migration cycle is not well understood. Here, we show that fast-moving cells guided by matrix cues establish positive feedback control of rear retraction by sensing membrane tension. We reveal a mechanism of rear retraction in 3D matrix and durotaxis controlled by caveolae, which form in response to low membrane tension at the cell rear. Caveolae activate RhoA-ROCK1/PKN2 signaling via the RhoA guanidine nucleotide exchange factor (GEF) Ect2 to control local F-actin organization and contractility in this subcellular region and promote translocation of the cell rear. A positive feedback loop between cytoskeletal signaling and membrane tension leads to rapid retraction to complete the migration cycle in fast-moving cells, providing directional memory to drive persistent cell migration in complex matrices.

lncRNA HOTAIR promotes gastric cancer proliferation and metastasis via targeting miR-126 to active CXCR4 and RhoA signaling pathway

HOTAIR, a well-known long noncoding RNAs (lncRNA), has been recognized to contribute to the tumor metastasis in several tumors. But its role in gastric cancer remains elusive. Here, we reported an increase in HOTAIR promoted proliferation and metastasis of gastric cancer cell lines. The HOTAIR and miR-126 level was determined in 15 paired primary gastric cancer tissues and their adjacent noncancerous gastric tissues. Over-expression or downregulation HOTAIR was conducted in AGS or BGC-823 cells to investigate the impact of HOTAIR in proliferation and metastasis. Then dual luciferase reporter assay was utilized to study the interaction between CXCR4 and miR-126. Cells transfected with shHOTAIR or miR-126 mimic were subjected to western blot to investigate the role of SDF-1/CXCR4 signaling in HOTAIR mediated proliferation and metastasis. HOTAIR was highly expressed in gastric cancer tissues and several gastric cancer cell lines. Overexpressed HOTAIR facilitated proliferation and metastasis in vitro while HOTAIR knockdown inhibit proliferation and metastasis. A negative correlation was observed between miR-126 and HOTAIR. And, we also confirmed the decrease in miR-126 in clinic specimen. Furthermore, HOTAIR and miR-126 negatively regulated each other and then increase or decrease CXCR4 expression and downstream pathway, respectively. CXCR4 was confirmed as a direct target of miR-126. Our study demonstrated that high HOTAIR expression promote proliferation and metastasis in gastric cancer via miR-126/CXCR4 axis and downstream signaling pathways.

Protein tyrosine phosphatase 11 acts through RhoA/ROCK to regulate eosinophil accumulation in the allergic airway

Src homology domain 2-containing protein tyrosine phosphatase 2 (SHP2) participates in multiple cell functions including cell shape, movement, and differentiation. Therefore, we investigated the potential role of SHP2 in eosinophil recruitment into lungs in allergic airway inflammation and explored the underlying mechanism. Both SHP2 and Ras homolog family member A (RhoA) kinase were robustly activated in the airway eosinophils of children with allergic asthma and of a mouse model with allergic airway inflammation. Moreover, inhibition of SHP2 activity by its specific inhibitors reverses the dephosphorylation of p190-A Rho GTPase-activating protein and in turn attenuates RhoA/Rho-associated protein kinase (ROCK) signaling, resulting in the attenuation of eosinophil migration in response to platelet-activating factor stimulation. Specifically, SHP2 deletion in myeloid cells did not affect the number and classification of circulating leukocytes but significantly attenuated the allergen-induced inflammatory cell, especially eosinophil, infiltration into lungs, and airway hyperreactivity. Notably, genetic interaction between RhoA and SHP2 indicated that RhoA inactivation and SHP2 deletion synergistically attenuated the allergen-induced eosinophil infiltration into lungs and airway hyperreactivity, whereas overexpression of active RhoA robustly restored the SHP2 deletion-resultant attenuation of allergen-induced eosinophil recruitment into lungs and airway hyperreactivity as well. Thus, this study demonstrates that SHP2 via RhoA/ROCK signaling regulates eosinophil recruitment in allergic airway inflammation and possibly in allergic asthma.-Xu, C., Wu, X., Lu, M., Tang, L., Yao, H., Wang, J., Ji, X., Hussain, M., Wu, J., Wu, X. Protein tyrosine phosphatase 11 acts through RhoA/ROCK to regulate eosinophil accumulation in the allergic airway.

The Involvement of the RhoA/ROCK Signaling Pathway in Hypersensitivity Reactions Induced by Paclitaxel Injection

A high incidence of hypersensitivity reactions (HSRs) largely limits the use of paclitaxel injection. Currently, these reactions are considered to be mediated by histamine release and complement activation. However, the evidence is insufficient and the molecular mechanism involved in paclitaxel injection-induced HSRs is still incompletely understood. In this study, a mice model mimicking vascular hyperpermeability was applied. The vascular leakage induced merely by excipients (polyoxyl 35 castor oil) was equivalent to the reactions evoked by paclitaxel injection under the same conditions. Treatment with paclitaxel injection could cause rapid histamine release. The vascular exudation was dramatically inhibited by pretreatment with a histamine antagonist. No significant change in paclitaxel injection-induced HSRs was observed in complement-deficient and complement-depleted mice. The RhoA/ROCK signaling pathway was activated by paclitaxel injection. Moreover, the ROCK inhibitor showed a protective effect on vascular leakage in the ears and on inflammation in the lungs. In conclusion, this study provided a suitable mice model for investigating the HSRs characterized by vascular hyperpermeability and confirmed the main sensitization of excipients in paclitaxel injection. Histamine release and RhoA/ROCK pathway activation, rather than complement activation, played an important role in paclitaxel injection-induced HSRs. Furthermore, the ROCK inhibitor may provide a potential preventive approach for paclitaxel injection side effects.

RhoA-Dependent HGF and c-Met Mediate Gas6-Induced Inhibition of Epithelial-Mesenchymal Transition, Migration, and Invasion of Lung Alveolar Epithelial Cells

Previously, we demonstrated that growth arrest-specific protein 6 (Gas6)/Axl or Mer signaling inhibited the transforming growth factor (TGF)-β1-induced epithelial–mesenchymal transition (EMT) in lung epithelial cells. Hepatocyte growth factor (HGF) has also been shown to inhibit TGF-β1-induced changes in EMT markers. Here, we examined whether Gas6 signaling can induce the production of HGF and c-Met in lung alveolar epithelial cells to mediate the inhibition of EMT and to inhibit the migration and invasion of epithelial cells. The inhibition of the RhoA/Rho kinase pathway, using either a RhoA-targeted small interfering RNA (siRNA) or the Rho kinase pharmacologic inhibitor Y27362, prevented the inhibition of TGF-β1-induced EMT in LA-4 cells and primary alveolar type II (AT II) epithelial cells. The c-Met antagonist PHA-665752 also blocked the anti-EMT effects associated with Gas6. Moreover, treatment with Y27362 or PHA-665752 prevented the Gas6-mediated inhibition of TGF-β1-induced migration and invasion. Our data provided evidence that the RhoA-dependent production of HGF and c-Met mediated the Gas6-induced inhibition of EMT, migration and invasion in lung alveolar epithelial cells. Thus, Gas6/Axl and Mer/RhoA signaling may be necessary for the maintenance of homeostasis in the alveolar epithelium, via HGF and c-Met.

Synthetic presentation of noncanonical Wnt5a motif promotes mechanosensing-dependent differentiation of stem cells and regeneration

Noncanonical Wnt signaling in stem cells is essential to numerous developmental events. However, no prior studies have capitalized on the osteoinductive potential of noncanonical Wnt ligands to functionalize biomaterials in enhancing the osteogenesis and associated skeleton formation. Here, we investigated the efficacy of the functionalization of biomaterials with a synthetic Wnt5a mimetic ligand (Foxy5 peptide) to promote the mechanosensing and osteogenesis of human mesenchymal stem cells by activating noncanonical Wnt signaling. Our findings showed that the immobilized Wnt5a mimetic ligand activated noncanonical Wnt signaling via the up-regulation of Disheveled 2 and downstream RhoA-ROCK signaling, leading to enhanced intracellular calcium level, F-actin stability, actomyosin contractility, and cell adhesion structure development. This enhanced mechanotransduction in stem cells promoted the in vitro osteogenic lineage commitment and the in vivo healing of rat calvarial defects. Our work provides valuable guidance for the developmentally inspired design of biomaterials for a wide array of therapeutic applications.

Elevated BMP and Mechanical Signaling Through YAP1/RhoA Poises FOP Mesenchymal Progenitors for Osteogenesis

Fibrodysplasia ossificans progressiva (FOP) is a rare genetic disease characterized by the formation of extraskeletal bone, or heterotopic ossification (HO), in soft connective tissues such as skeletal muscle. All familial and sporadic cases with a classic clinical presentation of FOP carry a gain-of-function mutation (R206H; c.617 G > A) in ACVR1, a cell surface receptor that mediates bone morphogenetic protein (BMP) signaling. The BMP signaling pathway is recognized for its chondro/osteogenic-induction potential, and HO in FOP patients forms ectopic but qualitatively normal endochondral bone tissue through misdirected cell fate decisions by tissue-resident mesenchymal stem cells. In addition to biochemical ligand-receptor signaling, mechanical cues from the physical environment are transduced to activate intracellular signaling, a process known as mechanotransduction, and can influence cell fates. Utilizing an established mesenchymal stem cell model of mouse embryonic fibroblasts (MEFs) from the Acvr1R206H/+ mouse model that mimics the human disease, we demonstrated that activation of the mechanotransductive effectors Rho/ROCK and YAP1 are increased in Acvr1R206H/+ cells. We show that on softer substrates, a condition associated with low mechanical signaling, the morphology of Acvr1R206H/+ cells is similar to the morphology of control Acvr1+/+ cells on stiffer substrates, a condition that activates mechanotransduction. We further determined that Acvr1R206H/+ cells are poised for osteogenic differentiation, expressing increased levels of chondro/osteogenic markers compared with Acvr1+/+ cells. We also identified increased YAP1 nuclear localization in Acvr1R206H/+ cells, which can be rescued by either BMP inhibition or Rho antagonism. Our results establish RhoA and YAP1 signaling as modulators of mechanotransduction in FOP and suggest that aberrant mechanical signals, combined with and as a result of the increased BMP pathway signaling through mutant ACVR1, lead to misinterpretation of the cellular microenvironment and a heightened sensitivity to mechanical stimuli that promotes commitment of Acvr1R206H/+ progenitor cells to chondro/osteogenic lineages.

Tumor Angiogenesis Is Differentially Regulated by Phosphorylation of Endothelial Cell Focal Adhesion Kinase Tyrosines-397 and -861

Expression of focal adhesion kinase (FAK) in endothelial cells (EC) is essential for angiogenesis, but how FAK phosphorylation at tyrosine-(Y)397 and Y861 regulate tumor angiogenesis in vivo is unknown. Here, we show that tumor growth and angiogenesis are constitutively reduced in inducible, ECCre+;FAKY397F/Y397F -mutant mice. Conversely, ECCre+;FAKY861F/Y861F mice exhibit normal tumor growth with an initial reduction in angiogenesis that recovered in end-stage tumors. Mechanistically, FAK-Y397F ECs exhibit increased Tie2 expression, reduced Vegfr2 expression, decreased β1 integrin activation, and disrupted downstream FAK/Src/PI3K(p55)/Akt signaling. In contrast, FAK-Y861F ECs showed decreased Vegfr2 and Tie2 expression with an enhancement in β1 integrin activation. This corresponds with a decrease in Vegfa-stimulated response, but an increase in Vegfa+Ang2- or conditioned medium from tumor cell-stimulated cellular/angiogenic responses, mimicking responses in end-stage tumors with elevated Ang2 levels. Mechanistically, FAK-Y861F, but not FAK-Y397F ECs showed enhanced p190RhoGEF/P130Cas-dependent signaling that is required for the elevated responses to Vegfa+Ang2. This study establishes the differential requirements of EC-FAK-Y397 and EC-FAK-Y861 phosphorylation in the regulation of EC signaling and tumor angiogenesis in vivo. SIGNIFICANCE: Distinct motifs of the focal adhesion kinase differentially regulate tumor blood vessel formation and remodeling.

Substance P induces fibrotic changes through activation of the RhoA/ROCK pathway in an in vitro human corneal fibrosis model

Fibrosis is characterized by hardening, overgrowth, and development of scars in various tissues as a result of faulty reparative processes, diseases, or chronic inflammation. During the fibrotic process in the corneal stroma of the eye, the resident cells called keratocytes differentiate into myofibroblasts, specialized contractile fibroblastic cells that produce excessive amounts of disorganized extracellular matrix (ECM) and pro-fibrotic components such as alpha-smooth muscle actin (α-SMA) and fibronectin. This study aimed to elucidate the role of substance P (SP), a neuropeptide that has been shown to be involved in corneal wound healing, in ECM production and fibrotic markers expression in quiescent human keratocytes, and during the onset of fibrosis in corneal fibroblasts, in an in vitro human corneal fibrosis model. We report that SP induces keratocyte contraction and upregulates gene expression of collagens I, III, and V, and fibrotic markers: α-SMA and fibronectin, in keratocytes. Using our in vitro human corneal fibrosis model, we show that SP enhances gene expression and secretion of collagens I, III, and V, and lumican. Moreover, SP upregulates gene expression and secretion of α-SMA and fibronectin, and increases contractility of corneal fibroblasts during the onset of fibrosis. Activation of the preferred SP receptor, the neurokinin-1 receptor (NK-1R), is necessary for the SP-induced pro-fibrotic changes. In addition, SP induces the pro-fibrotic changes through activation of the RhoA/ROCK pathway. Taken together, we show that SP has a pro-fibrotic effect in both quiescent human keratocytes and during the onset of fibrosis in an in vitro human corneal fibrosis model.

Modulation of the p75 neurotrophin receptor using LM11A-31 prevents diabetes-induced retinal vascular permeability in mice via inhibition of inflammation and the RhoA kinase pathway

AIMS/HYPOTHESIS

Breakdown of the inner blood-retinal barrier (BRB) is an early event in the pathogenesis of diabetic macular oedema, that eventually leads to vision loss. We have previously shown that diabetes causes an imbalance of nerve growth factor (NGF) isoforms resulting in accumulation of its precursor proNGF and upregulation of the p75 neurotrophin receptor (p75^NTR), with consequent increases in the activation of Ras homologue gene family, member A (RhoA). We also showed that genetic deletion of p75^NTR in diabetes preserved the BRB and prevented inflammatory mediators in retinas. This study aims to examine the therapeutic potential of LM11A-31, a small-molecule p75^NTR modulator and proNGF antagonist, in preventing diabetes-induced BRB breakdown. The study also examined the role of p75^NTR/RhoA downstream signalling in mediating cell permeability.

METHODS

Male C57BL/6 J mice were rendered diabetic using streptozotocin injection. After 2 weeks of diabetes, mice received oral gavage of LM11A-31 (50 mg kg^-1 day^-1) or saline (NaCl 154 mmol/l) for an additional 4 weeks. BRB breakdown was assessed by extravasation of BSA-AlexaFluor-488. Direct effects of proNGF were examined in human retinal endothelial (HRE) cells in the presence or absence of LM11A-31 or the Rho kinase inhibitor Y-27632.

RESULTS

Diabetes triggered BRB breakdown and caused significant increases in circulatory and retinal TNF-α and IL-1β levels. These effects coincided with significant decreases in retinal NGF and increases in vascular endothelial growth factor and proNGF expression, as well as activation of RhoA. Interventional modulation of p75^NTR activity through treatment of mouse models of diabetes with LM11A-31 significantly mitigated proNGF accumulation and preserved BRB integrity. In HRE cells, treatment with mutant proNGF (10 ng/ml) triggered increased cell permeability with marked reduction of expression of tight junction proteins, zona occludens-1 (ZO-1) and claudin-5, compared with control, independent of inflammatory mediators or cell death. Modulating p75^NTR significantly inhibited proNGF-mediated RhoA activation, occludin phosphorylation (at serine 490) and cell permeability. ProNGF induced redistribution of ZO-1 in the cell wall and formation of F-actin stress fibres; these effects were mitigated by LM11A-31.

CONCLUSIONS/INTERPRETATION

Targeting p75^NTR signalling using LM11A-31, an orally bioavailable receptor modulator, may offer an effective, safe and non-invasive therapeutic strategy for treating macular oedema, a major cause of blindness in diabetes.

Both insufficient and excessive glucocorticoid receptor-mediated signaling impair neuronal migration

Glucocorticoids (GCs) are a class of steroid hormones that regulate numerous physiological events in the human body. Clinically, glucocorticoids are used for anti-inflammatory and immunosuppressive actions via binding with glucocorticoid receptors (GRs). Emerging evidence has also indicated that inappropriate GC and GR levels are detrimental for brain development and eventually lead to severe neurological diseases. However, the roles of GC/GR signaling in brain development are not fully understood. Here, we showed that stable GR expression levels were critical for brain development, because both GR knockdown and overexpression severely impaired neuronal migration. Further studies showed that the multipolar-bipolar transition and leading process development were interrupted in GR-knockdown and GR-overexpressing neurons. To elucidate the underlying mechanism, we screened the protein levels of downstream molecules and identified RhoA as a factor negatively regulated by the GR. Restoration of the RhoA protein level partially rescued the neuronal migration defects in the GR-knockdown and GR-overexpressing neurons, indicating that RhoA played a major role in GR-mediated neuronal migration. These data suggest that an appropriate level of GC/GR signaling is essential for precise control of neuronal migration.

β-arrestin1/YAP/mutant p53 complexes orchestrate the endothelin A receptor signaling in high-grade serous ovarian cancer

The limited clinical response observed in high-grade serous ovarian cancer (HG-SOC) with high frequency of TP53 mutations (mutp53) might be related to mutp53-driven oncogenic pathway network. Here we show that β-arrestin1 (β-arr1), interacts with YAP, triggering its cytoplasmic-nuclear shuttling. This interaction allows β-arr1 to recruit mutp53 to the YAP-TEAD transcriptional complex upon activation of endothelin-1 receptors (ET-1R) in patient-derived HG-SOC cells and in cell lines bearing mutp53. In parallel, β-arr1 mediates the ET-1R-induced Trio/RhoA-dependent YAP nuclear accumulation. In the nucleus, ET-1 through β-arr1 orchestrates the tethering of YAP and mutp53 to YAP/mutp53 target gene promoters, including EDN1 that ensures persistent signals. Treatment of patient-derived xenografts reveals synergistic antitumoral and antimetastatic effects of the dual ET-1R antagonist macitentan in combination with cisplatinum, shutting-down the β-arr1-mediated YAP/mutp53 transcriptional programme. Furthermore, ETAR/β-arr1/YAP gene signature correlates with a worst prognosis in HG-SOC. These findings support effective combinatorial treatment for repurposing the ET-1R antagonists in HG-SOC.

RhoA as a Key Regulator of Innate and Adaptive Immunity

RhoA is a ubiquitously expressed cytoplasmic protein that belongs to the family of small GTPases. RhoA acts as a molecular switch that is activated in response to binding of chemokines, cytokines, and growth factors, and via mDia and the ROCK signaling cascade regulates the activation of cytoskeletal proteins, and other factors. This review aims to summarize our current knowledge on the role of RhoA as a general key regulator of immune cell differentiation and function. The contribution of RhoA for the primary functions of innate immune cell types, namely neutrophils, macrophages, and conventional dendritic cells (DC) to (i) get activated by pathogen-derived and endogenous danger signals, (ii) migrate to sites of infection and inflammation, and (iii) internalize pathogens has been fairly established. In activated DC, which constitute the most potent antigen-presenting cells of the immune system, RhoA is also important for the presentation of pathogen-derived antigen and the formation of an immunological synapse between DC and antigen-specific T cells as a prerequisite to induce adaptive T cell responses. In T cells and B cells as the effector cells of the adaptive immune system Rho signaling is pivotal for activation and migration. More recently, mutations of Rho and Rho-modulating factors have been identified to predispose for autoimmune diseases and as causative for hematopoietic malignancies.

The p75 Neurotrophin Receptor Is an Essential Mediator of Impairments in Hippocampal-Dependent Associative Plasticity and Memory Induced by Sleep Deprivation

Sleep deprivation (SD) interferes with hippocampal structural and functional plasticity, formation of long-term memory and cognitive function. The molecular mechanisms underlying these effects are incompletely understood. Here, we show that SD impaired synaptic tagging and capture and behavioral tagging, two major mechanisms of associative learning and memory. Strikingly, mutant male mice lacking the p75 neurotrophin receptor (p75NTR) were resistant to the detrimental effects of SD on hippocampal plasticity at both cellular and behavioral levels. Mechanistically, SD increased p75NTR expression and its interaction with phosphodiesterase. p75NTR deletion preserved hippocampal structural and functional plasticity by preventing SD-mediated effects on hippocampal cAMP-CREB-BDNF, cAMP-PKA-LIMK1-cofilin, and RhoA-ROCK2 pathways. Our study identifies p75NTR as an important mediator of hippocampal structural and functional changes associated with SD, and suggests that targeting p75NTR could be a promising strategy to limit the memory and cognitive deficits that accompany sleep loss.SIGNIFICANCE STATEMENT The lack of sufficient sleep is a major health concern in today's world. Sleep deprivation (SD) affects cognitive functions such as memory. We have investigated how associative memory mechanisms, synaptic tagging and capture (STC), was impaired in SD mice at cellular and behavioral level. Interestingly, mutant male mice that lacked the p75 neurotrophin receptor (p75NTR) were seen to be resistant to the SD-induced impairments in hippocampal synaptic plasticity and STC. Additionally, we elucidated the molecular pathways responsible for this rescue of plasticity in the mutant mice. Our study has thus identified p75NTR as a promising target to limit the cognitive deficits associated with SD.

RhoA in tyrosine hydroxylase neurones regulates food intake and body weight via altered sensitivity to peripheral hormones

Dopamine-producing tyrosine hydroxylase (TH) neurones in the hypothalamic arcuate nucleus (ARC) have recently been shown to be involved in ghrelin signalling and body weight homeostasis. In the present study, we investigate the role of the intracellular regulator RhoA in hypothalamic TH neurones in response to peripheral hormones. Diet-induced obesity was found to be associated with increased phosphorylation of TH in ARC, indicating obesity-associated increased activity of ARC TH neurones. Mice in which RhoA was specifically knocked out in TH neurones (TH-RhoA^-/- mice) were more sensitive to the orexigenic effect of peripherally administered ghrelin and displayed an abolished response to the anorexigenic hormone leptin. When TH-RhoA^-/- mice were challenged with a high-fat high-sucrose (HFHS) diet, they became hyperphagic and gained more body weight and fat mass compared to wild-type control mice. Importantly, lack of RhoA prevented development of ghrelin resistance, which is normally observed in wild-type mice after long-term HFHS diet feeding. Patch-clamp electrophysiological analysis demonstrated increased ghrelin-induced excitability of TH neurones in lean TH-RhoA^-/- mice compared to lean littermate control animals. Additionally, increased expression of the orexigenic hypothalamic neuropeptides agouti-related peptide and neuropeptide Y was observed in TH-RhoA^-/- mice. Overall, our data indicate that TH neurones in ARC are important for the regulation of body weight homeostasis and that RhoA is both a central effector in these neurones and important for the development of obesity-induced ghrelin resistance. The obese phenotype of TH-RhoA^-/- mice may be a result of increased sensitivity to ghrelin and decreased sensitivity to leptin, resulting in increased food intake.

Ramipril and resveratrol co-treatment attenuates RhoA/ROCK pathway-regulated early-stage diabetic nephropathy-associated glomerulosclerosis in streptozotocin-induced diabetic rats

Clinical studies have shown that hyperglycemia can induce early-stage diabetic nephropathy (DN). Furthermore, oxidative stress, tubular epithelial-mesenchymal transition and extracellular matrix accumulation promote the progression of DN to chronic kidney disease and tubulointerstitial fibrosis. It is necessary to initiate treatment at the early stages of DN or even during the early stages of diabetes. In this work, rats with streptozotocin (STZ)-induced diabetes mellitus (DM) presented early DN symptoms within 45 days, and collagen accumulation in the glomerulus of the rats was primarily mediated through the RhoA/ROCK pathway instead of the TGF-β signaling pathway. Resveratrol (15 mg/kg/day) and ramipril (10 mg/kg/day) co-treatment of STZ-induced DN rats showed that glomerulosclerosis in early-stage DN was reversible (P < .05 compared with that in STZ-induced DM rats). The results of this study support early intervention in diabetes or DN as a more efficient therapeutic strategy.

Therapeutic Effect of Y-27632 on Tumorigenesis and Cisplatin-Induced Peripheral Sensory Loss through RhoA-NF-κB

Chemotherapy-induced peripheral neuropathy (CIPN) is a major side effect of cancer therapy that frequently requires a reduction or cessation of treatments and negatively impacts the patient's quality of life. There is currently no effective means to prevent or treat CIPN. In this study, we developed and applied CIPN in an immunocompetent, syngeneic murine Lewis Lung Carcinoma (LLCab) model that enabled the elucidation of both tumor and host responses to cisplatin and treatments of Y-27632, a selective inhibitor of Rho kinase/p160^ROCK. Y-27632 not only preserved cisplatin's efficacy toward tumor suppression but also the combination treatment inhibited tumor cell proliferation and increased cellular apoptosis. By alleviating the cisplatin-induced loss of epidermal nerve fibers (ENFs), Y-27632 protected tumor-bearing mice from cisplatin-induced reduction of touch sensation. Furthermore, quantitative proteomic analysis revealed the striking cisplatin-induced dysregulation in cellular stress (inflammation, mitochondrial deficiency, DNA repair, etc.)-associated proteins. Y-27632 was able to reverse the changes of these proteins that are associated with Rho GTPase and NF-κB signaling network, and also decreased cisplatin-induced NF-κB hyperactivation in both footpad tissues and tumor. Therefore, Y-27632 is an effective adjuvant in tumor suppression and peripheral neuroprotection. These studies highlight the potential of targeting the RhoA-NF-κB axis as a combination therapy to treat CIPN. IMPLICATIONS: This study, for the first time, demonstrated the dual antineoplastic and neuroprotective effects of Rho kinase/p160^ROCK inhibition in a syngeneic immunocompetent tumor-bearing mouse model, opening the door for further clinical adjuvant development of RhoA-NF-κB axis to improve chemotherapeutic outcomes.

Oxygen-Glucose Deprivation/Reoxygenation Induces Human Brain Microvascular Endothelial Cell Hyperpermeability Via VE-Cadherin Internalization: Roles of RhoA/ROCK2

The destruction of the blood-brain barrier (BBB) contributes to a spectrum of neurological diseases such as stroke, and the hyperpermeability of endothelial cells is one of the characters of stroke, which is possibly exacerbated after reperfusion. However, the underlying mechanisms involving hyperpermeability after reperfusion between the endothelial cells remain poorly understood. Therefore, in the present study, the human microvascular endothelial cells (HBMECs) were exposed to oxygen-glucose deprivation/reperfusion (OGD/R) to mimic ischemic stroke condition in vitro with the aim to investigate the potential mechanisms induced by OGD/R. The permeability of cultured HBMECs was measured using FITC-labeled dextran in a Transwell system and transendothelial electrical resistance (TEER), while the RhoA activity was detected by pull-down assay. In addition, the phosphorylation of MYPT1, which reflects the activation of ROCK and the internalization of VE-cadherin, was detected by Western blot. It showed that OGD/R treatment significantly increased the permeability of HBMEC monolayers and facilitated the internalization of VE-cadherin in HBMEC monolayers. Pull-down assay showed that RhoA activation was obviously enhanced after OGD/R treatment, while RhoA and ROCK inhibitor significantly reversed OGD/R-induced HBMEC monolayers hyperpermeability and the internalization of VE-cadherin. Meanwhile, the knockdown assay showed that RhoA small interfering RNA (siRNA) led to similar effects. The inactivation of the downstream effector protein ROCK was also examined. Intriguingly, ROCK2 rather than ROCK1 exerted its adverse effects on HBMEC monolayer integrity, since ROCK2 knockdown markedly reverses the injury of OGD/R in HBMEC monolayers. In conclusion, the present study provides evidence that OGD/R may induce HBMEC monolayer hyperpermeability via RhoA/ROCK2-mediated VE-cadherin internalization, which may provide an impetus for the development of therapeutics targeting BBB damage in ischemic stroke.

RhoGTPase in Vascular Disease

Ras-homologous (Rho)A/Rho-kinase pathway plays an essential role in many cellular functions, including contraction, motility, proliferation, and apoptosis, inflammation, and its excessive activity induces oxidative stress and promotes the development of cardiovascular diseases. Given its role in many physiological and pathological functions, targeting can result in adverse effects and limit its use for therapy. In this review, we have summarized the role of RhoGTPases with an emphasis on RhoA in vascular disease and its impact on endothelial, smooth muscle, and heart and lung fibroblasts. It is clear from the various studies that understanding the regulation of RhoGTPases and their regulators in physiology and pathological conditions is required for effective targeting of Rho.

lncRNA 430945 promotes the proliferation and migration of vascular smooth muscle cells via the ROR2/RhoA signaling pathway in atherosclerosis

The proliferation and migration of vascular smooth muscle cells (VSMCs) are major cellular events in hypertension‑induced vascular remodeling, which is closely involved in the progression of atherosclerosis (AS). Although long non‑coding RNAs (lncRNAs) are gaining recognition as novel regulators of VSMCs, their functioning and role in AS remain to be elucidated. In the present study, the role of lncRNA ENST00000430945 (lncRNA 430945) in AS was investigated. VSMCs transfected with a small interfering RNA (siRNA; si‑430945) and a negative control (si‑NC) were used. Cell Counting Kit‑8, wound‑healing and Transwell migration arrays were performed to determine whether lncRNA 430945 influenced VSMC proliferation and migration. Furthermore, the study examined whether a correlation exists between lncRNA 430945 and the receptor tyrosine kinase‑like orphan receptor 2 (ROR2) signaling pathway. It was found that the expression of lncRNA 430945 was high in human AS tissues, which in turn promoted angiotensin II (AngII)‑induced VSMC proliferation. Reverse transcription‑quantitative polymerase chain reaction (RT‑qPCR) and western blot analyses showed that lncRNA 430945 mediated the AngII‑induced upregulation of ROR2. In addition, the microarray and RT‑qPCR results showed that the expression of lncRNA 430945 was increased considerably in AS tissues. The downregulation of lncRNA 430945 significantly suppressed AngII‑induced VSMC proliferation and migration. In addition, ROR2 levels in VSMCs transfected with si‑430945 were markedly lower than those cells transfected with si‑NC. Additionally, western blotting showed that lncRNA 430945 activated the signaling pathways associated with ROR2 and Ras homolog gene family member A (RhoA). The upregulation of lncRNA 430945 in AS promoted the proliferation and migration of VSMCs via activation of the ROR2/RhoA signaling pathway. Therefore, targeting ROR2 or RhoA may be a promising technique in developing therapeutic strategies for treating AS.

Integrin-Mediated Macrophage Adhesion Promotes Lymphovascular Dissemination in Breast Cancer

Lymphatic vasculature is crucial for metastasis in triple-negative breast cancer (TNBC); however, cellular and molecular drivers controlling lymphovascular metastasis are poorly understood. We define a macrophage-dependent signaling cascade that facilitates metastasis through lymphovascular remodeling. TNBC cells instigate mRNA changes in macrophages, resulting in β4 integrin-dependent adhesion to the lymphovasculature. β4 integrin retains macrophages proximal to lymphatic endothelial cells (LECs), where release of TGF-β1 drives LEC contraction via RhoA activation. Macrophages promote gross architectural changes to lymphovasculature by increasing dilation, hyperpermeability, and disorganization. TGF-β1 drives β4 integrin clustering at the macrophage plasma membrane, further promoting macrophage adhesion and demonstrating the dual functionality of TGF-β1 signaling in this context. β4 integrin-expressing macrophages were identified in human breast tumors, and a combination of vascular-remodeling macrophage gene signature and TGF-β signaling scores correlates with metastasis. We postulate that future clinical strategies for patients with TNBC should target crosstalk between β4 integrin and TGF-β1.

The Rho/MRTF pathway inhibitor CCG-222740 reduces stellate cell activation and modulates immune cell populations in KrasG12D; Pdx1-Cre (KC) mice

The stromal reaction in pancreatic cancer creates a physical barrier that blocks therapeutic intervention and creates an immunosuppressive tumor microenvironment. The Rho/myocardin-related transcription factor (MRTF) pathway is implicated in the hyper-activation of fibroblasts in fibrotic diseases and the activation of pancreatic stellate cells. In this study we use CCG-222740, a small molecule, designed as a Rho/MRTF pathway inhibitor. This compound decreases the activation of stellate cells in vitro and in vivo, by reducing the levels of alpha smooth muscle actin (α-SMA) expression. CCG-222740 also modulates inflammatory components of the pancreas in KC mice (LSL-KrasG12D/+; Pdx-1-Cre) stimulated with caerulein. It decreases the infiltration of macrophages and increases CD4 T cells and B cells. Analysis of the pancreatic adenocarcinoma (PDA) TCGA dataset revealed a correlation between elevated RhoA, RhoC and MRTF expression and decreased survival in PDA patients. Moreover, a MRTF signature is correlated with a Th2 cell signature in human PDA tumors.

Expression of orphan GPR56 correlates with tumor progression in human epithelial ovarian cancer

G protein-coupled receptor 56 (GPR56) has been demonstrated to be a significant prognostic predictor in several types of malignances, including melanoma, glioblastoma, breast cancer, colon cancer, and pancreatic cancer. GPR56 has a putative mucin-like extracellular domain, indicating functions for this receptor in the cell-cell interactions and triggering different downstream signaling pathways responsible for regulating cell survival, proliferation, adhesion, and migration. But the expression and clinical significance of GPR56 has not been elucidated in epithelial ovarian cancer (EOC). We detected GPR56 expression by immunohistochemistry in 110 samples of ovarian serous carcinoma to explore the correlation between its expression and clinicopathologic characteristics and overall survival. As the result, we found that GPR56 expression is significantly associated with advanced FIGO stage (P = 0.01) and positive lymph node invasion (P = 0.016), and it serves as an independent unfavorable prognostic factor through univariate and multivariate analysis. GPR56 knockdown could dramatically decrease the proliferation and invasion of epithelial ovarian cancer cells through down-regulating the RhoA-GTP level and up-regulating the E-cadherin level, which indicates GPR56 could promote the progression and invasion of EOC. In conclusion, GPR56 expression was demonstrated as an independent prognostic factor in EOC, suggesting that GPR56 may play an oncogenic role through the Rho and E-cadherin pathway and GPR56 could be a novel potential drug target in EOC.

p190RhoGAPs, the ARHGAP35- and ARHGAP5-Encoded Proteins, in Health and Disease

Small guanosine triphosphatases (GTPases) gathered in the Rat sarcoma (Ras) superfamily represent a large family of proteins involved in several key cellular mechanisms. Within the Ras superfamily, the Ras homolog (Rho) family is specialized in the regulation of actin cytoskeleton-based mechanisms. These proteins switch between an active and an inactive state, resulting in subsequent inhibiting or activating downstream signals, leading finally to regulation of actin-based processes. The On/Off status of Rho GTPases implicates two subsets of regulators: GEFs (guanine nucleotide exchange factors), which favor the active GTP (guanosine triphosphate) status of the GTPase and GAPs (GTPase activating proteins), which inhibit the GTPase by enhancing the GTP hydrolysis. In humans, the 20 identified Rho GTPases are regulated by over 70 GAP proteins suggesting a complex, but well-defined, spatio-temporal implication of these GAPs. Among the quite large number of RhoGAPs, we focus on p190RhoGAP, which is known as the main negative regulator of RhoA, but not exclusively. Two isoforms, p190A and p190B, are encoded by ARHGAP35 and ARHGAP5 genes, respectively. We describe here the function of each of these isoforms in physiological processes and sum up findings on their role in pathological conditions such as neurological disorders and cancers.

PLK1 plays dual roles in centralspindlin regulation during cytokinesis

Cytokinesis begins upon anaphase onset. An early step involves local activation of the small GTPase RhoA, which triggers assembly of an actomyosin-based contractile ring at the equatorial cortex. Here, we delineated the contributions of PLK1 and Aurora B to RhoA activation and cytokinesis initiation in human cells. Knock-down of PRC1, which disrupts the spindle midzone, revealed the existence of two pathways that can initiate cleavage furrow ingression. One pathway depends on a well-organized spindle midzone and PLK1, while the other depends on Aurora B activity and centralspindlin at the equatorial cortex and can operate independently of PLK1. We further show that PLK1 inhibition sequesters centralspindlin onto the spindle midzone, making it unavailable for Aurora B at the equatorial cortex. We propose that PLK1 activity promotes the release of centralspindlin from the spindle midzone through inhibition of PRC1, allowing centralspindlin to function as a regulator of spindle midzone formation and as an activator of RhoA at the equatorial cortex.

Cytoskeletal alteration modulates cancer cell invasion through RhoA-YAP signaling in stromal fibroblasts

Cancer-associated fibroblasts(CAFs) participate in carcinogenesis through interaction with cancer cells. This study aimed to investigate the mechanism of cytoskeletal alteration of CAFs and its role in invasion of oral squamous cell carcinoma(OSCC).Immortalized normal fibroblasts(hTERT-hNOFs) co-cultured with OSCC cells showed myofibroblastic and senescent phenotypes like CAFs. Thus, this study substituted hTERT-hNOFs for CAFs. Next, the cytoskeletal alteration and its molecular mechanism were investigated in hTERT-hNOFs co-cultured with OSCC. As results, we found that RhoA regulated cytoskeletal organization in fibroblasts surrounding OSCC cells. Furthermore, as a downstream transcriptional factor of RhoA, YAP was mainly localized in the nucleus of hTERT-hNOFs co-cultured with OSCC. Consequently, we examined whether nuclear YAP localization of fibroblasts could influence cancer progression. YAPS127A fibroblasts manifesting nuclear localization of YAP induced cytoskeletal alteration and increased gel contractility and matrix stiffness, and thereby enhances the invasiveness of OSCC cells. In conclusion, the modification of tumor microenvironment, such as cytoskeletal change and matrix remodeling via RhoA-YAP in CAFs, modulates OSCC invasion. These understandings will provide the development of novel approaches for CAFs-based cancer therapy.