Integrin signaling to the actin cytoskeleton

Complementary transcriptomic and proteomic analyses elucidate the toxicological molecular mechanisms of deoxynivalenol-induced contractile dysfunction in enteric smooth muscle cells

Deoxynivalenol (DON) is one of the frequent Fusarium mycotoxins and poses a serious threat to public health worldwide. DON-induced weight loss is tightly connected with its ability to decrease feed intake by influencing gastrointestinal tract (GIT) motility. Our previous reports indicated that DON interfered with intestinal motility by injuring the contractility of enteric smooth muscle cells (SMC). Here, we further explored the potential mechanisms by employing a complementary method of transcriptomics and proteomics using the porcine enteric smooth muscle cell line (PISMC) as an experimental model. The transcriptomic and proteomic data uncover that the expression of numerous extracellular matrix (ECM) proteins and multiple integrin subunits were downregulated in PISMC under DON exposure, suppressing the ECM-integrin receptor interaction and its mediated signaling. Furthermore, DON treatment could depress actin polymerization, as reflected by the upregulated expression of Rho GTPase-activating proteins and cofilin in PISMC. Meanwhile, the expression levels of downstream contractile apparatus genes were significantly inhibited after challenge with DON. Taken together, the current results suggest that DON inhibits enteric SMC contractility by regulating the ECM-integrin-actin polymerization signaling pathway. Our findings provide novel insights into the potential mechanisms behind the DON toxicological effects in the GIT of humans and animals.

Influence of clinical zirconia surface treatments on microscopic characteristics and adhesion-proliferation behavior of human gingival fibroblasts

Zirconia is favored in dental implant applications due to its biocompatibility, mechanical properties, and esthetic appeal, particularly in its interaction with soft oral tissues such as the gingiva. To optimize zirconia for clinical use, surface treatments like sanding and polishing are essential. The aim of this study was to investigate the effects of clinical surface treatments on the microscopic characteristics of zirconia and the adhesion and proliferation of human gingival fibroblasts (HGFs). Scanning electron microscopy (SEM) and fluorescence microscopy were utilized to examine the microscopic morphology and roughness resulting from various clinical surface treatment procedures on zirconia and to assess their impact on the microscopic appearance and behavior of HGFs. The results showed that the application of surface treatment procedures, particularly polishing treatments, resulted in the formation of a regular shallow groove morphology and a significant reduction in roughness in zirconia. This was accompanied by improved cell proliferation, cell adhesion, and the expression of integrin β1 in HGFs. The results suggest that smoother zirconia surfaces promote better cell-material interactions, potentially improving the clinical success of dental implants. This research contributes to our understanding of the optimal surface roughness for soft tissue adhesion and the effect of different micro-morphologies on HGF attachment.

HAM/TSP Pathogenesis: The Transmigration Activity of HTLV-1-Infected T Cells into Tissues

Slowly progressive spastic paraparesis with bladder dysfunction, the main clinical feature of human T-cell leukemia virus-1 (HTLV-1)-associated myelopathy/tropical spastic paraparesis (HAM/TSP), is induced by chronic inflammation in the spinal cord, mainly the lower thoracic cord. A long-standing bystander mechanism, such as the destruction of surrounding tissues by inflammatory cytokines, etc., induced under the interaction between infiltrated HTLV-1-infected CD4⁺ T cells and HTLV-1-specific CD8⁺ cytotoxic T cells, has been considered implicated for the induction of chronic inflammation. As this bystander mechanism is triggered conceivably by the transmigration of HTLV-1-infected CD4⁺ T cells to the spinal cord, heightened transmigrating activity of HTLV-1-infected CD4⁺ T cells to the spinal cord might play a crucial role as the first responder in the development of HAM/TSP. This review evaluated the functions of HTLV-1-infected CD4⁺ T cells in HAM/TSP patients as the prerequisite for the acquisition of the activity such as adhesion molecule expression changes, small GTPases activation, and expression of mediators involved in basement membrane disruption. The findings suggest that HTLV-1-infected CD4⁺ T cells in HAM/TSP patients have enough potential to facilitate transmigration into the tissues. Future HAM/TSP research should clarify the molecular mechanisms leading to the establishment of HTLV-1-infected CD4⁺ T cells as the first responder in HAM/TSP patients. In addition, a regimen with an inhibitory activity against the transmigration of HTLV-1-infected CD4⁺ T cells into the spinal cord might be recommended as one of the therapeutic strategies against HAM/TSP patients.

Filamin A in platelets: Bridging the (signaling) gap between the plasma membrane and the actin cytoskeleton

Platelets are anucleate cells that are essential for hemostasis and wound healing. Upon activation of the cell surface receptors by their corresponding extracellular ligands, platelets undergo rapid shape change driven by the actin cytoskeleton; this shape change reaction is modulated by a diverse array of actin-binding proteins. One actin-binding protein, filamin A (FLNA), cross-links and stabilizes subcortical actin filaments thus providing stability to the cell membrane. In addition, FLNA binds the intracellular portion of multiple cell surface receptors and acts as a critical intracellular signaling scaffold that integrates signals between the platelet's plasma membrane and the actin cytoskeleton. This mini-review summarizes how FLNA transduces critical cell signals to the platelet cytoskeleton.

Dysregulation of integrin αvβ3 and α5β1 impedes migration of placental endothelial cells in fetal growth restriction

Placentas from pregnancies complicated by severe early-onset fetal growth restriction (FGR) exhibit diminished vascular development mediated by impaired angiogenesis, but underlying mechanisms remain unknown. In this study, we show that FGR endothelial cells demonstrate inherently reduced migratory capacity despite the presence of fibronectin, a matrix protein abundant in placental stroma that displays abnormal organization in FGR placentas. Thus, we hypothesized that aberrant endothelial-fibronectin interactions in FGR are a key mechanism underlying impaired FGR endothelial migration. Using human fetoplacental endothelial cells isolated from uncomplicated term control and FGR pregnancies, we assessed integrin α5β1 and αvβ3 regulation during cell migration. We show that endothelial integrin α5β1 and αvβ3 interactions with fibronectin are required for migration and that FGR endothelial cells responded differentially to integrin inhibition, indicating integrin dysregulation in FGR. Whole-cell expression was not different between groups. However, there were significantly more integrins in focal adhesions and reduced intracellular trafficking in FGR. These newly identified changes in FGR endothelial cellular processes represent previously unidentified mechanisms contributing to persistent angiogenic deficiencies in FGR.

A mechanosensitive lipolytic factor in the bone marrow promotes osteogenesis and lymphopoiesis

Exercise can prevent osteoporosis and improve immune function, but the mechanism remains unclear. Here, we show that exercise promotes reticulocalbin-2 secretion from the bone marrow macrophages to initiate bone marrow fat lipolysis. Given the crucial role of lipolysis in exercise-stimulated osteogenesis and lymphopoiesis, these findings suggest that reticulocalbin-2 is a pivotal regulator of a local adipose-osteogenic/immune axis. Mechanistically, reticulocalbin-2 binds to a functional receptor complex, which is composed of neuronilin-2 and integrin beta-1, to activate a cAMP-PKA signaling pathway that mobilizes bone marrow fat via lipolysis to fuel the differentiation and function of mesenchymal and hematopoietic stem cells. Notably, the administration of recombinant reticulocalbin-2 in tail-suspended and old mice remarkably decreases bone marrow fat accumulation and promotes osteogenesis and lymphopoiesis. These findings identify reticulocalbin-2 as a novel mechanosensitive lipolytic factor in maintaining energy homeostasis in bone resident cells, and it provides a promising target for skeletal and immune health.

ANGPTL3 impacts proteinuria and hyperlipidemia in primary nephrotic syndrome

Background

It is unclear why primary nephrotic syndrome (PNS) patients often have dyslipidemia. Recent studies have shown that angiopoietin-like protein 3 (ANGPTL3) is an important regulator of lipid metabolism. In this study, we explored how ANGPTL3 impacts dyslipidemia during PNS development.

Methods

We measured the serum levels of ANGPTL3 in PNS patients (n=196). Furthermore, the degree of proteinuria and lipid metabolism were examined in angptl3-overexpressing transgenic (angptl3-tg) mice at different ages. Moreover, in this study, we used the clustered regularly interspaced short palindromic repeats-associated protein 9 (CRISPR/Cas9) system to create angptl3-knockout (angptl3-/-) mice to investigate lipopolysaccharide (LPS)-induced nephrosis.

Results

Compared with that in the healthy group, the serum level of ANGPTL3 in the PNS group was significantly increased (32 (26.35-39.66) ng/ml vs. 70.44 (63.95-76.51) ng/ml, Z =-4.81, P < 0.001). There were significant correlations between the serum level of ANGPTL3 and the levels of cholesterol (r=0.34, P < 0.001), triglycerides (r= 0.25, P = 0.001) and low-density lipoprotein (r= 0.50, P < 0.001) in PNS patients. With increasing age, angptl3-tg mice exhibited increasingly severe hypertriglyceridemia and proteinuria. The pathological features of angptl3-tg mice included rich lipid droplet deposition in hepatocytes and diffuse podocyte effacement. Compared to wild-type mice, angptl3-/- mice showed significantly lower degrees of lipid dysfunction and proteinuria after stimulation with LPS. The effects of ANGPTL3 on nephrotic dyslipidemia were confirmed in cultured hepatocytes subjected to angptl3 knockdown or overexpression. Finally, significant alterations in lipoprotein lipase (LPL) levels were observed in liver tissues from Angptl3-/- and wild-type mice stimulated with LPS.

Conclusions

ANGPTL3 could be involved in the development of dyslipidemia, as well as proteinuria, during PNS pathogenesis. Inhibition of LPL expression may the mechanism by which ANGPTL3 induces hyperlipidemia in PNS.

Avian Hepatitis E Virus ORF2 Protein Interacts with Rap1b to Induce Cytoskeleton Rearrangement That Facilitates Virus Internalization

Avian hepatitis E virus (HEV) causes liver diseases and multiple extrahepatic disorders in chickens. However, the mechanisms involved in avian HEV entry remain elusive. Herein, we identified the RAS-related protein 1b (Rap1b) as a potential HEV-ORF2 protein interacting candidate. Experimental infection of chickens and cells with an avian HEV isolate from China (CaHEV) led to upregulated expression and activation of Rap1b both in vivo and in vitro. By using CaHEV capsid as mimic of virion to treat cell in vitro, it appears that the interaction between the viral capsid and Rap1b promoted cell membrane recruitment of the downstream effector Rap1-interacting molecule (RIAM). In turn, RIAM further enhanced Talin-1 membrane recruitment and retention, which led to the activation of integrin α5/β1, as well as integrin-associated membrane protein kinases, including focal adhesion kinase (FAK). Meanwhile, FAK activation triggered activation of downstream signaling molecules, such as Ras-related C3 botulinum toxin substrate 1 RAC1 cell division cycle 42 (CDC42), p21-activated kinase 1 (PAK1), and LIM domain kinase 1 (LIMK1). Finally, F-actin rearrangement induced by Cofilin led to the formation of lamellipodia, filopodia, and stress fibers, contributes to plasma membrane remodeling, and might enhance CaHEV virion internalization. In conclusion, our data suggested that Rap1b activation was triggered during CaHEV infection and appeared to require interaction between CaHEV-ORF2 and Rap1b, thereby further inducing membrane recruitment of Talin-1. Membrane-bound Talin-1 then activates key Integrin-FAK-Cofilin cascades involved in modulation of actin kinetics, and finally leads to F-actin rearrangement and membrane remodeling to potentially facilitate internalization of CaHEV virions into permissive cells. IMPORTANCE Rap1b is a multifunctional protein that is responsible for cell adhesion, growth, and differentiation. The inactive form of Rap1b is phosphorylated and distributed in the cytoplasm, while active Rap1b is prenylated and loaded with GTP to the cell membrane. In this study, the activation of Rap1b was induced during the early stage of avian HEV infection under the regulation of PKA and SmgGDS. Continuously activated Rap1b recruited its effector RIAM to the membrane, thereby inducing the membrane recruitment of Talin-1 that led to the activation of membrane α5/β1 integrins. The triggering of the signaling pathway-associated Integrin α5/β1-FAK-CDC42&RAC1-PAK1-LIMK1-Cofilin culminated in F-actin polymerization and membrane remodeling that might promote avian HEV virion internalization. These findings suggested a novel mechanism that is potentially utilized by avian HEV to invade susceptible cells.

Recent Progress in Understanding the Action of Natural Compounds at Novel Therapeutic Drug Targets for the Treatment of Liver Cancer

Liver cancer is the third most common cause of cancer-related death following lung and stomach cancers. As a highly lethal disease, liver cancer is diagnosed frequently in less developed countries. Natural compounds extracted from herbs, animals and natural materials have been adopted by traditional Chinese medicine (TCM) practices and reported to be effective in the development of new medications for the treatment of diseases. It is important to focus on the mechanisms of action of natural compounds against hepatocellular carcinoma (HCC), particularly in terms of cell cycle regulation, apoptosis induction, autophagy mediation and cell migration and invasion. In this review, we characterize novel representative natural compounds according to their pharmacologic effects based on recently published studies. The aim of this review is to summarize and explore novel therapeutic drug targets of natural compounds, which could accelerate the discovery of new anticancer drugs.

Eukaryotic initiation factor 6 regulates mechanical responses in endothelial cells

The repertoire of extratranslational functions of components of the protein synthesis apparatus is expanding to include control of key cell signaling networks. However, very little is known about noncanonical functions of members of the protein synthesis machinery in regulating cellular mechanics. We demonstrate that the eukaryotic initiation factor 6 (eIF6) modulates cellular mechanobiology. eIF6-depleted endothelial cells, under basal conditions, exhibit unchanged nascent protein synthesis, polysome profiles, and cytoskeleton protein expression, with minimal effects on ribosomal biogenesis. In contrast, using traction force and atomic force microscopy, we show that loss of eIF6 leads to reduced stiffness and force generation accompanied by cytoskeletal and focal adhesion defects. Mechanistically, we show that eIF6 is required for the correct spatial mechanoactivation of ERK1/2 via stabilization of an eIF6-RACK1-ERK1/2-FAK mechanocomplex, which is necessary for force-induced remodeling. These results reveal an extratranslational function for eIF6 and a novel paradigm for how mechanotransduction, the cellular cytoskeleton, and protein translation constituents are linked.

Potential key factors involved in regulating adipocyte dedifferentiation

Adipocytes are the key constituents of adipose tissue, and their de-differentiation process has been widely observed in physiological and pathological conditions. For obese people, the promotion of adipocyte de-differentiation or maintenance of an undifferentiated state of adipocytes may help to improve their metabolic condition. Thus, understanding the regulatory mechanisms of adipocyte de-differentiation is necessary for treating metabolic diseases. Attractively, in addition to intracellular signals regulating adipocyte de-differentiation, external factors such as temperature and pressure also affect adipocyte de-differentiation. In this review, we summarize the recent progress in the field and discuss the regulatory roles and mechanisms of involved endogenous and exogenous factors during the process of de-differentiation.

Designing 3D-nanosubstrates mimicking biological cell growth: pitfalls of using 2D substrates in the evaluation of anticancer efficiency

Designing nano-substrates (NS) that support three-dimensional (3D) cell growth using physico-chemical interventions mimicking the cellular microenvironment is highly challenging. Here we report NS that assist 3D cell development (3D NS) using multi-components on a glass substrate (2D GS), which mimics the ex vivo tissue microenvironment and promotes 3D cell growth superior to conventional 2D cell culturing methodologies. 3D NS were chemically fabricated by linking the combination of advanced materials imparting different physico-chemical traits, for example, multiwalled carbon nanotubes (CNT), graphene (G), bovine serum albumin (BSA), and iron oxide magnetic nanoparticles (MNP). We compared cell-substrate interactions resulting in cellular morphological changes, influence on the cell circularity index (CI), nuclear-cytoplasmic ratios (N/C), and nuclear compression or derangements using human colorectal carcinoma cells (HCT116) and cervical cancer (HeLa) cells. We observed the increase in N/C, extended on the 3D NS micro-environment as indicative of cellular adaptation and the transformation. HCT116 and HeLa cells on 2D GS showed an N/C ratio <0.3, and 3D NS cultured cells exhibited a higher N/C ratio (>0.5). The most significant increase in the ratio, relative to arrested cell spreading, was observed with G-3D NS. Furthermore, 3D NS were evaluated for the cell viability differentiations using the anticancer drug doxorubicin (Dox). The drug-treated cells on 3D NS demonstrated far-displaced N/C ratios compared to 2D GS. In conclusion, 3D NS systems implicate an 'in vitro to in vivo' relevance for the outcome in cell biology, cell proliferation and migration, and in anticancer drug efficacy evaluation.

Protein tyrosine phosphatase 1B targets focal adhesion kinase and paxillin in cell-matrix adhesions

Protein tyrosine phosphatase 1B (PTP1B, also known as PTPN1) is an established regulator of cell-matrix adhesion and motility. However, the nature of substrate targets at adhesion sites remains to be validated. Here, we used bimolecular fluorescence complementation assays, in combination with a substrate trapping mutant of PTP1B, to directly examine whether relevant phosphotyrosines on paxillin and focal adhesion kinase (FAK, also known as PTK2) are substrates of the phosphatase in the context of cell-matrix adhesion sites. We found that the formation of catalytic complexes at cell-matrix adhesions requires intact tyrosine residues Y31 and Y118 on paxillin, and the localization of FAK at adhesion sites. Additionally, we found that PTP1B specifically targets Y925 on the focal adhesion targeting (FAT) domain of FAK at adhesion sites. Electrostatic analysis indicated that dephosphorylation of this residue promotes the closed conformation of the FAT 4-helix bundle and its interaction with paxillin at adhesion sites.

The dipeptide prolyl-hydroxyproline promotes cellular homeostasis and lamellipodia-driven motility via active β1-integrin in adult tendon cells

Collagen-derived hydroxyproline (Hyp)-containing peptides have a variety of biological effects on cells. These bioactive collagen peptides are locally generated by the degradation of endogenous collagen in response to injury. However, no comprehensive study has yet explored the functional links between Hyp-containing peptides and cellular behavior. Here, we show that the dipeptide prolyl-4-hydroxyproline (Pro-Hyp) exhibits pronounced effects on mouse tendon cells. Pro-Hyp promotes differentiation/maturation of tendon cells with modulation of lineage-specific factors and induces significant chemotactic activity in vitro. In addition, Pro-Hyp has profound effects on cell proliferation, with significantly upregulated extracellular signal-regulated kinase phosphorylation and extracellular matrix production and increased type I collagen network organization. Using proteomics, we have predicted molecular transport, cellular assembly and organization, and cellular movement as potential linked-network pathways that could be altered in response to Pro-Hyp. Mechanistically, cells treated with Pro-Hyp demonstrate increased directional persistence and significantly increased directed motility and migration velocity. They are accompanied by elongated lamellipodial protrusions with increased levels of active β1-integrin-containing focal contacts, as well as reorganization of thicker peripheral F-actin fibrils. Pro-Hyp-mediated chemotactic activity is significantly reduced (p < 0.001) in cells treated with the mitogen-activated protein kinase kinase 1/2 inhibitor PD98059 or the α5β1-integrin antagonist ATN-161. Furthermore, ATN-161 significantly inhibits uptake of Pro-Hyp into adult tenocytes. Thus, our findings document the molecular basis of the functional benefits of the Pro-Hyp dipeptide in cellular behavior. These dynamic properties of collagen-derived Pro-Hyp dipeptide could lead the way to its application in translational medicine.

Modulation of lung cytoskeletal remodeling, RXR based metabolic cascades and inflammation to achieve redox homeostasis during extended exposures to lowered pO2

Extended exposure to low pO₂ has multiple effects on signaling cascades. Despite multiple exploratory studies, omics studies elucidating the signaling cascades essential for surviving extended low pO₂ exposures are lacking. In this study, we simulated low pO₂ (P_B = 40 kPa; 7620 m) exposure in male Sprague-Dawley rats for 3, 7 and 14 days. Redox stress assays and proteomics based network biology were performed using lungs and plasma. We observed that redox homeostasis was achieved after day 3 of exposure. We investigated the causative events for this. Proteo-bioinformatics analysis revealed STAT3 to be upstream of lung cytoskeletal processes and systemic lipid metabolism (RXR) derived inflammatory processes, which were the key events. Thus, during prolonged low pO₂ exposure, particularly those involving slowly decreasing pressures, redox homeostasis is achieved but energy metabolism is perturbed and this leads to an immune/inflammatory signaling impetus after third day of exposure. We found that an interplay of lung cytoskeletal elements, systemic energy metabolism and inflammatory proteins aid in achieving redox homeostasis and surviving extended low pO₂ exposures. Qualitative perturbations to cytoskeletal stability and innate immunity/inflammation were also observed during extended low pO₂ exposure in humans exposed to 14,000 ft for 7, 14 and 21 days.

Effect of Fucoxanthinol on Pancreatic Ductal Adenocarcinoma Cells from an N-Nitrosobis(2-oxopropyl)amine-initiated Syrian Golden Hamster Pancreatic Carcinogenesis Model

BACKGROUND/AIM

Fucoxanthinol (FxOH) is a marine carotenoid metabolite with potent anti-cancer activity. However, little is known about the efficacy of FxOH in pancreatic cancer. In the present study, we investigated the inhibitory effect of FxOH on six types of cells cloned from N-nitrosobis(2-oxopropyl)amine (BOP)-induced hamster pancreatic cancer (HaPC) cells.

MATERIALS AND METHODS

FxOH action and its molecular mechanisms were investigated in HaPC cells using flow-cytometry, comprehensive gene array, and western blotting analyses.

RESULTS

FxOH (5.0 μM) significantly suppressed the growth of four out of six types of HaPC cells. Moreover, FxOH significantly suppressed cell cycle, chemokine, integrin, actin polymerization, microtubule organization and PI3K/AKT and TGF-β signals, and activated caspase-3 followed by apoptosis and anoikis induction in HaPC-5 cells.

CONCLUSION

FxOH may have a high potential as a cancer chemopreventive agent in a hamster pancreatic carcinogenesis model.

Effects of physicochemical properties of polyacrylamide (PAA) and (polydimethylsiloxane) PDMS on cardiac cell behavior

In vitro cell culture is commonly applied in laboratories around the world. Cultured cells are either of primary origin or established cell lines. Such transformed cell lines are increasingly replaced by pluripotent stem cell derived organotypic cells with more physiological properties. The quality of the culture conditions and matrix environment is of considerable importance in this regard. In fact, mechanical cues of the extracellular matrix have substantial effects on the cellular physiology. This is especially true if contractile cells such as cardiomyocytes are cultured. Therefore, elastic biomaterials have been introduced as scaffolds in 2D and 3D culture models for different cell types, cardiac cells among them. In this review, key aspects of cell-matrix interaction are highlighted with focus on cardiomyocytes and chemical properties as well as strengths and potential pitfalls in using two commonly applied polymers for soft matrix engineering, polyacrylamide (PAA) and polydimethylsiloxane (PDMS) are discussed.

Erythroblastic Island Macrophages Shape Normal Erythropoiesis and Drive Associated Disorders in Erythroid Hematopoietic Diseases

Erythroblastic islands (EBIs), discovered more than 60 years ago, are specialized microenvironments for erythropoiesis. This island consists of a central macrophage with surrounding developing erythroid cells. EBI macrophages have received intense interest in the verifications of the supporting erythropoiesis hypothesis. Most of these investigations have focused on the identification and functional analyses of EBI macrophages, yielding significant progresses in identifying and isolating EBI macrophages, as well as verifying the potential roles of EBI macrophages in erythropoiesis. EBI macrophages express erythropoietin receptor (Epor) both in mouse and human, and Epo acts on both erythroid cells and EBI macrophages simultaneously in the niche, thereby promoting erythropoiesis. Impaired Epor signaling in splenic niche macrophages significantly inhibit the differentiation of stress erythroid progenitors. Moreover, accumulating evidence suggests that EBI macrophage dysfunction may lead to certain erythroid hematological disorders. In this review, the heterogeneity, identification, and functions of EBI macrophages during erythropoiesis under both steady-state and stress conditions are outlined. By reviewing the historical data, we discuss the influence of EBI macrophages on erythroid hematopoietic disorders and propose a new hypothesis that erythroid hematopoietic disorders are driven by EBI macrophages.

Microfibrous Extracellular Matrix Changes the Liver Hepatocyte Energy Metabolism via Integrins

Cell line-based liver models are critical tools for liver-related studies. However, the conventional monolayer culture of hepatocytes, the most widely used in vitro model, does not have the extracellular matrix (ECM), which contributes to the three-dimensional (3D) arrangement of the hepatocytes in the liver. As a result, the metabolic properties of the hepatocytes in the monolayer tissue culture may not accurately reflect those of the hepatocytes in the liver. Here, we developed a modular platform for 3D hepatocyte cultures on fibrous ECMs produced by electrospinning, a technique that can turn a polymer solution to the micro/nanofibers and has been widely used to produce scaffolds for 3D cell cultures. Metabolomics quantitation by liquid chromatography-mass spectrometry (LC-MS) indicated that Huh7 hepatocytes grown in microfibers electrospun from silk fibroin exhibited reduced glycolysis and tricarboxylic acid (TCA) cycle, as compared to the cells cultured as a monolayer. Further mechanistic studies suggested that integrins were correlated to the ECM's effects. This is the first time to report how an ECM scaffold could affect the fundamental metabolism of the hepatocytes via integrins.

Platelet-rich plasma inhibits osteoblast apoptosis and actin cytoskeleton disruption induced by gingipains through upregulating integrin β1

The aim of this study was to explore the effects of platelet-rich plasma on gingipain-caused changes in cell morphology and apoptosis of osteoblasts. Mouse osteoblasts MC3T3-E1 cells were treated with gingipain extracts from Porphyromonas gingivalis in the presence or absence of platelet-rich plasma. Apoptosis was detected with terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling staining. F-actin was determined by phalloidin-fluorescent staining and observed under confocal microscopy. Western blot analysis was used to detect integrin β1, F-actin, and G-actin protein expressions. A knocking down approach was used to determine the role of integrin β1. The platelet-rich plasma protected osteoblasts from gingipain-induced apoptosis in a dose-dependent manner, accompanied by upregulation of integrin β1. Platelet-rich plasma reversed the loss of F-actin integrity and decrease of F-actin/G-actin ratio in osteoblasts in the presence of gingipains. By contrast, the effects of platelet-rich plasma were abrogated by knockdown of integrin β1. The platelet-rich plasma failed to reduce cell apoptosis and reorganize the cytoskeleton after knockdown of integrin β1. In conclusion, platelet-rich plasma inhibits gingipain-induced osteoblast apoptosis and actin cytoskeleton disruption by upregulating integrin β1 expression.

Circulating extracellular vesicles from patients with breast cancer enhance migration and invasion via a Src‑dependent pathway in MDA‑MB‑231 breast cancer cells

Triple negative breast cancer (TNBC) is a breast cancer subtype associated with high rates of metastasis, heterogeneity, drug resistance and a poor prognosis. Extracellular vesicles (EVs) are vesicles of endosomal and plasma membrane origin, and are secreted by healthy and cancer cells. In cancer, EVs contribute to tumor progression by mediating escape from the immune system surveillance, and are involved in extracellular matrix degradation, invasion, angiogenesis, migration and metastasis. Furthermore, EVs have been identified in several human fluids. However, the role of EVs from patients with breast cancer in the migration and invasion of human breast cancer cells is not fully understood. The present study investigated whether EVs isolated from Mexican patients with breast cancer can induce cellular processes related to invasion in breast cancer. Moreover, plasma fractions enriched in EVs and deprived of platelet-derived EVs obtained from blood samples of 32 Mexican patients with biopsy-diagnosed breast cancer at different clinical stages who had not received treatment were analyzed. Furthermore, one control group was included, which consisted of 20 Mexican healthy females. The present results demonstrated that EVs from women with breast cancer promote migration and invasion, and increase matrix metalloproteinase (MMP)-2 and MMP-9 secretion in TNBC MDA-MB-231 cells. In addition, it was found that EVs from patients with breast cancer induced Src and focal adhesion kinase activation, and focal adhesions assembly with an increase in focal adhesions number, while the migration and invasion was dependent on Src activity. Collectively, EVs from Mexican patients with breast cancer induce migration and invasion via a Src-dependent pathway in TNBC MDA-MB-231 cells.

A Surface-Tailoring Method for Rapid Non-Thermosensitive Cell-Sheet Engineering via Functional Polymer Coatings

Cell sheet engineering, a technique utilizing a monolayer cell sheet, has recently emerged as a promising technology for scaffold-free tissue engineering. In contrast to conventional tissue-engineering approaches, the cell sheet technology allows cell harvest as a continuous cell sheet with intact extracellular matrix proteins and cell-cell junction, which facilitates cell transplantation without any other artificial biomaterials. A facile, non-thermoresponsive method is demonstrated for a rapid but highly reliable platform for cell-sheet engineering. The developed method exploits the precise modulation of cell-substrate interactions by controlling the surface energy of the substrate via a series of functional polymer coatings to enable prompt cell sheet harvesting within 100 s. The engineered surface can trigger an intrinsic cellular response upon the depletion of divalent cations, leading to spontaneous cell sheet detachment under physiological conditions (pH 7.4 and 37 °C) in a non-thermoresponsive manner. Additionally, the therapeutic potential of the cell sheet is successfully demonstrated by the transplantation of multilayered cell sheets into mouse models of diabetic wounds and ischemia. These findings highlight the ability of the developed surface for non-thermoresponsive cell sheet engineering to serve as a robust platform for regenerative medicine and provide significant breakthroughs in cell sheet technology.

Mechanical Signals Induce Dedifferentiation of Mature Adipocytes and Increase the Retention Rate of Fat Grafts

BACKGROUND

Mature adipocytes dedifferentiate in vivo on application of a soft-tissue expander. Dedifferentiated adipocytes can proliferate and redifferentiate. This study used tissue expanders to pretreat adipose flaps, to increase the retention rate after fat graft.

METHODS

A soft-tissue expander and silicone sheet were implanted beneath the left and right inguinal fat pads of rats, respectively. After 7 days of expansion, the adipose tissue derived from the pads was transplanted beneath dorsal skin. Samples were harvested at various time points, and histologic, immunohistochemical, and gene expression analyses were conducted. Mature adipocytes were cultured in vitro under a pressure of 520 Pa. Changes in cell morphology, the cytoskeleton, and expression of mechanical signal-related proteins were investigated.

RESULTS

Pressure in adipose flaps increased to 25 kPa on expansion. Mature adipocytes dedifferentiated following expansion. At 1 week after transplantation, the expression of vascular endothelial growth factor (p < 0.05) was higher in the expanded group. The retention rate at 12 weeks after transplantation was higher in the expanded group (56 ± 3 percent) than in the control group (32 ± 3 percent) (p < 0.05), and the surviving/regenerating zones (p < 0.01) were wider. The lipid content of mature adipocytes gradually decreased on culture under increased pressure, and these cells regained a proliferative capacity. This was accompanied by increased expression of mechanical signal--related proteins (p < 0.05).

CONCLUSIONS

Mechanical signals may induce dedifferentiation of mature adipocytes. Dedifferentiated adipocytes increase the retention rate of fat grafts by acting as seed cells.

PAX8 expression in high-grade serous ovarian cancer positively regulates attachment to ECM via Integrin β3

Background

Ovarian cancer is the third most common cause of death among gynecologic malignancies worldwide. Understanding the biology and molecular pathogenesis of ovarian epithelial tumors is key to developing improved prognostic indicators and effective therapies. We aimed to determine the effects of PAX8 expression on the migrative, adhesive and survival capabilities of high-grade serous carcinoma cells.

Methods

PAX8 depleted Fallopian tube secretory cells and ovarian cancer cells were generated using short interfering siRNA. Anoikis resistance, cell migration and adhesion properties of PAX8 silenced cells were analyzed by means of specific assays. Chromatin immunoprecipitation (ChIP) was carried out using a PAX8 polyclonal antibody to demonstrate that PAX8 is able to bind to the 5′-flanking region of the ITGB3 gene positively regulating its expression.

Results

Here, we report that RNAi silencing of PAX8 sensitizes non-adherent cancer cells to anoikis and affects their tumorigenic properties. We show that PAX8 plays a critical role in migration and adhesion of both Fallopian tube secretory epithelial cells and ovarian cancer cells. Inhibition of PAX8 gene expression reduces the ability of ovarian cancer cells to migrate and adhere to the ECM and specifically to fibronectin and/or collagen substrates. Moreover, loss of PAX8 strongly reduces ITGB3 expression and consequently the correct expression of the αvβ3 heterodimer on the plasma membrane.

Conclusions

Our results demonstrate that PAX8 modulates the interaction of tumor cells with the extracellular matrix (ECM). Notably, we also highlight a novel pathway downstream this transcription factor. Overall, PAX8 could be a potential therapeutic target for high-grade serous carcinoma.

7-O-methylpunctatin, a Novel Homoisoflavonoid, Inhibits Phenotypic Switch of Human Arteriolar Smooth Muscle Cells

Remodeling of arterioles is a pivotal event in the manifestation of many inflammation-based cardio-vasculopathologies, such as hypertension. During these remodeling events, vascular smooth muscle cells (VSMCs) switch from a contractile to a synthetic phenotype. The latter is characterized by increased proliferation, migration, and invasion. Compounds with anti-inflammatory actions have been successful in attenuating this phenotypic switch. While the vast majority of studies investigating phenotypic modulation were undertaken in VSMCs isolated from large vessels, little is known about the effect of such compounds on phenotypic switch in VSMCs of microvessels (microVSMCs). We have recently characterized a novel homoisoflavonoid that we called 7-O-methylpunctatin (MP). In this study, we show that MP decreased FBS-induced cell proliferation, migration, invasion, and adhesion. MP also attenuated adhesion of THP-1 monocytes to microVSMCs, abolished FBS-induced expression of MMP-2, MMP-9, and NF-κB, as well as reduced activation of ERK1/2 and FAK. Furthermore, MP-treated VSMCs showed an increase in early (myocardin, SM-22α, SM-α) and mid-term (calponin and caldesmon) differentiation markers and a decrease in osteopontin, a protein highly expressed in synthetic VSMCs. MP also reduced transcription of cyclin D1, CDK4 but increased protein levels of p21 and p27. Taken together, these results corroborate an anti-inflammatory action of MP on human microVSMCs. Therefore, by inhibiting the synthetic phenotype of microVSMCs, MP may be a promising modulator for inflammation-induced arteriolar pathophysiology.

Atypical Endocannabinoid Signaling Initiates a New Form of Memory-Related Plasticity at a Cortical Input to Hippocampus

Endocannabinoids (ECBs) depress transmitter release at sites throughout the brain. Here, we describe another form of ECB signaling that triggers a novel form of long-term potentiation (LTP) localized to the lateral perforant path (LPP) which conveys semantic information from cortex to hippocampus. Two cannabinoid CB1 receptor (CB1R) signaling cascades were identified in hippocampus. The first is pregnenolone sensitive, targets vesicular protein Munc18-1 and depresses transmitter release; this cascade is engaged by CB1Rs in Schaffer-Commissural afferents to CA1 but not in the LPP, and it does not contribute to LTP. The second cascade is pregnenolone insensitive and LPP specific; it entails co-operative CB1R/β1-integrin signaling to effect synaptic potentiation via stable enhancement of transmitter release. The latter cascade is engaged during LPP-dependent learning. These results link atypical ECB signaling to the encoding of a fundamental component of episodic memory and suggest a novel route whereby endogenous and exogenous cannabinoids affect cognition.

Effect of the Large and Small T-Antigens of Human Polyomaviruses on Signaling Pathways

Viruses are intracellular parasites that require a permissive host cell to express the viral genome and to produce new progeny virus particles. However, not all viral infections are productive and some viruses can induce carcinogenesis. Irrespective of the type of infection (productive or neoplastic), viruses hijack the host cell machinery to permit optimal viral replication or to transform the infected cell into a tumor cell. One mechanism viruses employ to reprogram the host cell is through interference with signaling pathways. Polyomaviruses are naked, double-stranded DNA viruses whose genome encodes the regulatory proteins large T-antigen and small t-antigen, and structural proteins that form the capsid. The large T-antigens and small t-antigens can interfere with several host signaling pathways. In this case, we review the interplay between the large T-antigens and small t-antigens with host signaling pathways and the biological consequences of these interactions.

Quantifying Cell Confluency by Plasmonic Nanodot Arrays to Achieve Cultivating Consistency

The determination of cell confluency and subculture timing for cell culture consistency is crucial in the field of cell-based research, but there is no universal standard concerning optimal confluence. In this study, gold nanodot arrays on glass substrates were used as culture substrates, and their spectral shifts of localized surface plasmon resonance (LSPR) were employed to monitor cell growth and quantify cell confluency. Experiments including cell counting, metabolic activity, focal adhesion, and cell cycle were also performed to confirm the cell growth monitoring accuracy of the LSPR signals. The LSPR signal exhibited the same trends like the increase of cell numbers and cell metabolic activity and reached the maximum as the cell growth achieved confluency, suggesting its great capability as an effective indicator to predict suitable subculture timing. The proposed sensing approach is a noninterventional, nondestructive, real-time, and useful tool to help biologists quantify the optimal subculture timing, achieve cell culture consistency, and obtain reproducible experimental results efficiently.

Molecular Mechanisms of Microglial Motility: Changes in Ageing and Alzheimer's Disease

Microglia are the tissue-resident immune cells of the central nervous system, where they constitute the first line of defense against any pathogens or injury. Microglia are highly motile cells and in order to carry out their function, they constantly undergo changes in their morphology to adapt to their environment. The microglial motility and morphological versatility are the result of a complex molecular machinery, mainly composed of mechanisms of organization of the actin cytoskeleton, coupled with a “sensory” system of membrane receptors that allow the cells to perceive changes in their microenvironment and modulate their responses. Evidence points to microglia as accountable for some of the changes observed in the brain during ageing, and microglia have a role in the development of neurodegenerative diseases, such as Alzheimer’s disease. The present review describes in detail the main mechanisms driving microglial motility in physiological conditions, namely, the cytoskeletal actin dynamics, with emphasis in proteins highly expressed in microglia, and the role of chemotactic membrane proteins, such as the fractalkine and purinergic receptors. The review further delves into the changes occurring to the involved proteins and pathways specifically during ageing and in Alzheimer’s disease, analyzing how these changes might participate in the development of this disease.

EPC-derived exosomes promote osteoclastogenesis through LncRNA-MALAT1

Bone repair involves bone resorption through osteoclastogenesis and the stimulation of neovascularization and osteogenesis by endothelial progenitor cells (EPCs). However, the role of EPCs in osteoclastogenesis is unclear. In this study, we assess the effects of EPC-derived exosomes on the migration and osteoclastic differentiation of primary mouse bone marrow-derived macrophages (BMMs) in vitro using immunofluorescence, western blotting, RT-PCR and Transwell assays. We also evaluated the effects of EPC-derived exosomes on the homing and osteoclastic differentiation of transplanted BMMs in a mouse bone fracture model in vivo. We found that EPCs cultured with BMMs secreted exosomes into the medium and, compared with EPCs, exosomes had a higher expression level of LncRNA-MALAT1. We confirmed that LncRNA-MALAT1 directly binds to miR-124 to negatively control miR-124 activity. Moreover, overexpression of miR-124 could reverse the migration and osteoclastic differentiation of BMMs induced by EPC-derived exosomes. A dual-luciferase reporter assay indicated that the integrin ITGB1 is the target of miR-124. Mice treated with EPC-derived exosome-BMM co-transplantations exhibited increased neovascularization at the fracture site and enhanced fracture healing compared with those treated with BMMs alone. Overall, our results suggest that EPC-derived exosomes can promote bone repair by enhancing recruitment and differentiation of osteoclast precursors through LncRNA-MALAT1.

Microbial uptake by the respiratory epithelium: outcomes for host and pathogen

Intracellular occupancy of the respiratory epithelium is a useful pathogenic strategy facilitating microbial replication and evasion of professional phagocytes or circulating antimicrobial drugs. A less appreciated but growing body of evidence indicates that the airway epithelium also plays a crucial role in host defence against inhaled pathogens, by promoting ingestion and quelling of microorganisms, processes that become subverted to favour pathogen activities and promote respiratory disease. To achieve a deeper understanding of beneficial and deleterious activities of respiratory epithelia during antimicrobial defence, we have comprehensively surveyed all current knowledge on airway epithelial uptake of bacterial and fungal pathogens. We find that microbial uptake by airway epithelial cells (AECs) is a common feature of respiratory host-microbe interactions whose stepwise execution, and impacts upon the host, vary by pathogen. Amidst the diversity of underlying mechanisms and disease outcomes, we identify four key infection scenarios and use best-characterised host-pathogen interactions as prototypical examples of each. The emergent view is one in which effi-ciency of AEC-mediated pathogen clearance correlates directly with severity of disease outcome, therefore highlighting an important unmet need to broaden our understanding of the antimicrobial properties of respiratory epithelia and associated drivers of pathogen entry and intracellular fate.

How the epigenome integrates information and reshapes the synapse

In the past few decades, the field of neuroepigenetics has investigated how the brain encodes information to form long-lasting memories that lead to stable changes in behaviour. Activity-dependent molecular mechanisms, including, but not limited to, histone modification, DNA methylation and nucleosome remodelling, dynamically regulate the gene expression required for memory formation. Recently, the field has begun to examine how a learning experience is integrated at the level of both chromatin structure and synaptic physiology. Here, we provide an overview of key established epigenetic mechanisms that are important for memory formation. We explore how epigenetic mechanisms give rise to stable alterations in neuronal function by modifying synaptic structure and function, and highlight studies that demonstrate how manipulating epigenetic mechanisms may push the boundaries of memory.

Matrix Rigidity-Dependent Regulation of Ca2+ at Plasma Membrane Microdomains by FAK Visualized by Fluorescence Resonance Energy Transfer

The dynamic regulation of signal transduction at plasma membrane microdomains remains poorly understood due to limitations in current experimental approaches. Genetically encoded biosensors based on fluorescent resonance energy transfer (FRET) can provide high spatiotemporal resolution for imaging cell signaling networks. Here, distinctive regulation of focal adhesion kinase (FAK) and Ca2+ signals are visualized at different membrane microdomains by FRET using membrane-targeting biosensors. It is shown that rigidity-dependent FAK and Ca2+ signals in human mesenchymal stem cells (hMSCs) are selectively activated at detergent-resistant membrane (DRM or rafts) microdomains during the cell-matrix adhesion process, with minimal activities at non-DRM domains. The rigidity-dependent Ca2+ signal at the DRM microdomains is downregulated by either FAK inhibition or lipid raft disruption, suggesting that FAK and lipid raft integrity mediate the in situ Ca2+ activation. It is further revealed that transient receptor potential subfamily M7 (TRPM7) participates in the mobilization of Ca2+ signals within DRM regions. Thus, the findings provide insights into the underlying mechanisms that regulate Ca2+ and FAK signals in hMSCs under different mechanical microenvironments.

Unchain My Heart: Integrins at the Basis of iPSC Cardiomyocyte Differentiation

The cellular response to the extracellular matrix (ECM) microenvironment mediated by integrin adhesion is of fundamental importance, in both developmental and pathological processes. In particular, mechanotransduction is of growing importance in groundbreaking cellular models such as induced pluripotent stem cells (iPSC), since this process may strongly influence cell fate and, thus, augment the precision of differentiation into specific cell types, e.g., cardiomyocytes. The decryption of the cellular machinery starting from ECM sensing to iPSC differentiation calls for new in vitro methods. Conveniently, engineered biomaterials activating controlled integrin-mediated responses through chemical, physical, and geometrical designs are key to resolving this issue and could foster clinical translation of optimized iPSC-based technology. This review introduces the main integrin-dependent mechanisms and signalling pathways involved in mechanotransduction. Special consideration is given to the integrin-iPSC linkage signalling chain in the cardiovascular field, focusing on biomaterial-based in vitro models to evaluate the relevance of this process in iPSC differentiation into cardiomyocytes.

ECM signaling in cartilage development and endochondral ossification

During cartilage development chondrocytes undergo a multi-step process characterized by consecutive changes in cell morphology and gene expression. Cell proliferation, polarity, differentiation, and migration are influenced by chemical and mechanical signaling between the extracellular matrix (ECM) and the cell. Several structurally diverse transmembrane receptors such as integrins, discoidin domain receptor 2 (DDR 2), and CD44 mediate the crosstalk between cells and their ECM. However, the contribution of cell-matrix interactions during early chondrogenesis and further cartilage development through cell receptors and their signal transduction pathways is still not fully understood. Determination of receptor signaling pathways and the function of downstream targets will aid in a better understanding of musculoskeletal pathologies such as chondrodysplasia, and the development of new approaches for the treatment of cartilage disorders. We will summarize recent findings, linking cell receptors and their potential signaling pathways to the control of chondrocyte behavior during early chondrogenesis and endochondral ossification.

Integrin α5 down-regulation by miR-205 suppresses triple negative breast cancer stemness and metastasis by inhibiting the Src/Vav2/Rac1 pathway

Triple negative breast cancer (TNBC) usually displays more aggressive metastasis, the underlying mechanism is unclear. Previous studies showed that microRNA-205 (miR-205) has controversial roles in cancer, however, its role in TNBC metastasis and the underlying mechanism have not been well-understood. In this study we found that miR-205 expression level is extremely low in basal mesenchymal-like highly migratory and invasive TNBC cells. Stably re-expressing miR-205 in TNBC cells significantly reduced their migration, invasion capability and cancer stem cell (CSC)-like property. Nude mouse orthotopic mammary xenograft tumor model study revealed that miR-205 re-expression greatly decreases TNBC tumor growth and abolishes spontaneous lung metastasis. Mechanistic studies demonstrated that miR-205 inhibits TNBC cell metastatic traits and tumor metastasis by down-regulating integrin α5 (ITGA5). Moreover, ITGA5 knockout using the CRISPR/Cas9 technique achieved the same strong inhibitory effect on TNBC cell CSC-like property and tumor metastasis as re-expressing miR-205 did. Further mechanistic studies indicated that ITGA5 down-regulation by miR-205 re-expression impairs TNBC cell metastatic traits by inhibiting the Src/Vav2/Rac1 pathway. Together, our findings suggest that miR-205 and ITGA5 may serve as potential targets for developing effective therapies for metastatic TNBC.

Mechanisms and consequences of constitutive activation of integrin-linked kinase in acute myeloid leukemia

Integrin-linked kinase (ILK) has emerged as a critical adaptor and mediator protein in cell signaling pathways that is commonly deregulated in acute myeloid leukemia (AML). This has led to the expectation that therapeutic targeting of ILK may be a useful option in treating leukemia. Although ILK can regulate many cellular processes, including cell differentiation, survival, migration, apoptosis and production of pro-inflammatory cytokines, its role in promoting AML is still unclear. However, its ability to mediate phosphorylation and regulate the important hematopoietic stem cell regulators protein kinase B (AKT) and glycogen synthase kinase-3β supports ILK as an attractive target for the development of novel anticancer therapeutics. In this review, we summarize the existing knowledge of ILK signaling and its impact on cytokines, paying particular attention to the relevance of ILK signaling in AML. We also discuss the rationale for targeting ILK in the treatment of AML and conclude with perspectives on the future of ILK-targeted therapy in AML.

Naked physically synthesized gold nanoparticles affect migration, mitochondrial activity, and proliferation of vascular smooth muscle cells

Introduction

Vascular smooth muscle cells (VSMCs) play an important role in the development and progression of atherosclerosis and vascular injuries in terms of proliferation and migration. Therefore, the aim of this study was to investigate the anti-migratory and proliferative effects of naked gold nanoparticles (AuNPs) on VSMCs.

Materials and methods

One set of physically synthesized AuNPs (pAuNPs) and three sets of chemically synthesized AuNPs (cAuNPs) were tested.

Results and discussion

Among them, the pAuNPs were found to significantly and markedly inhibit platelet-derived growth factor (PDGF)-induced VSMC migration. Transmission electron microscopy revealed that the pAuNPs were ingested and aggregated in the cytoplasm at an early stage of treatment, while the viability of VSMCs was not affected within 24 hours of treatment. The pAuNP treatment enhanced cellular mitochondrial activity but inhibited basal and PDGF-induced VSMC proliferation, as determined by MTT, WST-1, and BrdU cell proliferation assays. Furthermore, the pAuNPs did not interfere with PDGF signaling or matrix metalloproteinase-2 expression/activity. Unlike the cAuNPs, the pAuNPs could markedly reduce VSMC adhesion to collagen, which was supported by the findings that the pAuNPs could inhibit collagen-induced tyrosine protein and focal adhesion kinase (FAK) phosphorylation and actin cytoskeleton reorganization during cell adhesion. The in vitro effects of the pAuNPs were confirmed in the in vivo rat balloon-injured carotid artery model by diminishing the proliferating VSMCs.

Conclusion

Taken together, the present study provides the first evidence that naked pAuNPs can reduce VSMC migration and compromise cell adhesion by affecting FAK and tyrosine-protein activation. The pAuNPs also have an inhibitory effect on PDGF-induced VSMC proliferation and can reduce proliferating/migrating VSMC expression in vivo.

Src Cooperates with Oncogenic Ras in Tumourigenesis via the JNK and PI3K Pathways in Drosophila epithelial Tissue

The Ras oncogene (Rat Sarcoma oncogene, a small GTPase) is a key driver of human cancer, however alone it is insufficient to produce malignancy, due to the induction of cell cycle arrest or senescence. In a Drosophila melanogaster genetic screen for genes that cooperate with oncogenic Ras (bearing the Ras^V12 mutation, or Ras^ACT), we identified the Drosophila Src (Sarcoma virus oncogene) family non-receptor tyrosine protein kinase genes, Src42A and Src64B, as promoting increased hyperplasia in a whole epithelial tissue context in the Drosophila eye. Moreover, overexpression of Src cooperated with Ras^ACT in epithelial cell clones to drive neoplastic tumourigenesis. We found that Src overexpression alone activated the Jun N-terminal Kinase (JNK) signalling pathway to promote actin cytoskeletal and cell polarity defects and drive apoptosis, whereas, in cooperation with Ras^ACT, JNK led to a loss of differentiation and an invasive phenotype. Src + Ras^ACT cooperative tumourigenesis was dependent on JNK as well as Phosphoinositide 3-Kinase (PI3K) signalling, suggesting that targeting these pathways might provide novel therapeutic opportunities in cancers dependent on Src and Ras signalling.

Gingipains disrupt F-actin and cause osteoblast apoptosis via integrin β1

BACKGROUND AND OBJECTIVE

The aim of this study was to explore the cellular mechanisms underlying gingipain-caused changes in cell morphology and apoptosis of osteoblasts.

MATERIAL AND METHODS

Human calvarial osteoblasts and mouse osteoblasts MC3T3-E1 were treated with gingipain extracts from Porphyromonas gingivalis stain W83. Apoptosis was detected with annexin V and propidium iodide flow cytometry analysis or terminal deoxynucleotidyl transferase mediated dUTP nick-end labeling staining. F-actin was determined by immunostaining. Western blotting was used to detect protein expression. Knocking down and overexpressing approaches were used to determine the role of integrin β1.

RESULTS

Osteoblasts exposed to gingipain extracts displayed increased apoptosis, accompanied by loss of F-actin integrity and cell shrinkage. The effects of gingipain extracts were abolished by the cysteine protease inhibitor N-tosyl-l-lysyl chloromethyl-ketone. Notably, gingipain extracts resulted in reduction of integrin β1, accompanied by diminished active RhoA whereas without effect on the total RhoA. Knockdown of integrin β1 resembled those seen in gingipain-treated osteoblasts. By contrast, the effects of gingipain extracts were abrogated by either overexpression of integrin β1 or presence of RhoA agonist CN03.

CONCLUSION

Gingipain-induced F-actin disruption and apoptosis are mediated by the degradation of integrin β1 and inhibition of RhoA activity, which account for osteoblast apoptosis.

Acidic pHe regulates cytoskeletal dynamics through conformational integrin β1 activation and promotes membrane protrusion

An acidic extracellular pH (pHe) in the tumor microenvironment has been suggested to facilitate tumor growth and metastasis. However, the molecular mechanisms by which tumor cells sense acidic signal to induce a transition to an aggressive phenotype remain elusive. Here, we showed that an acidic pHe (pH 6.5) stimulation resulted in protrusion and epithelial-mesenchymal transition (EMT) of cancer cells, which promoted migration and matrix degeneration. Using computational molecular dynamics simulations, we reported acidic pHe-induced opening of the Integrin dimers (α5β1) headpiece which indicated the activation of integrin. Moreover, acidic pHe promoted maturation of focal adhesions, temporal activation of Rho GTPases and microfilament reorganization through integrin β1-activated FAK signaling. Furthermore, mechanical balance of cytoskeleton (actin, tubulin and vimentin) contributed to acidic pHe-triggered protrusion and morphology change. Taken together, these findings revealed that integrin β1 could be a novel pH-regulated sensitive molecule which confers protrusion and malignant phenotype of cancer cells.

Role of Integrin Signaling Activation on the Development of Human T Cell Leukemia Virus-1 (HTLV-1)-Associated Myelopathy/Tropical Spastic Paraparesis: Its Relationship to HTLV-1-Infected CD4+ T Cell Transmigrating Activity into the Tissues

The main clinical feature of human T cell leukemia virus-1 (HTLV-1)-associated myelopathy/tropical spastic paraparesis (HAM/TSP) is slowly progressive spastic paraparesis with bladder dysfunction. HAM/TSP is induced by chronic inflammation in the spinal cord, mainly the lower thoracic cord. A long-standing bystander mechanism, such as the destruction of surrounding tissues by the interaction between infiltrated Th1-like, HTLV-1-infected CD4⁺ T cells and HTLV-1-specific CD8⁺ cytotoxic T cells (CTL), is probably critical for the induction of chronic inflammation. Although the HTLV-1-infected CD4⁺ T cells in HAM/TSP appear to play a crucial role in the initial pathogenesis of HAM/TSP, the exact mechanisms of how these cells acquire their function as the first responders in the pathogenesis of HAM/TSP still remain unresolved. Herein, we propose the importance of the activation of both outside-in signals from integrin signaling and inside-out signals for integrin signaling in the HTLV-1-infected CD4⁺ T cells of HAM/TSP patients.

Nano-Pore Size of Alumina Affects Osteoblastic Response

The rapid development and application of nanotechnology to biological interfaces has impacted the bone implant field, allowing researchers to finely modulate the interface between biomaterials and recipient tissues. In the present study, oxidative anodization was exploited to generate two alumina surfaces with different pore diameters. The former displayed surface pores in the mean range of 16-30 nm, while in the latter pores varied from to 65 to 89 nm. The samples were characterized by Field Emission Scanning Electron Microscopy (FESEM) and Energy Dispersive X-ray spectroscopy (EDX) analysis prior to being tested with pre-osteoblastic MC3T3-E1 cells. In vitro cell response was studied in terms of early cell adhesion, viability, and morphology, including focal adhesion quantification. Both the alumina samples promoted higher cell adhesion and viability than the control condition represented by the standard culture dish plastic. Osteogenic differentiation was assessed through alkaline phosphatase activity and extracellular calcium deposition, and it was found that of the two nano-surfaces, one was more efficient than the other. By comparing for the first time two nano-porous alumina surfaces with different pore diameters, our data supported the role of nano-topography in inducing cell response. Modulating a simple aspect of surface texture may become an attractive route for guiding bone healing and regeneration around implantable metals.

Stiffness-dependent motility and proliferation uncoupled by deletion of CD44

Information in the microenvironment guides complex cellular decisions such as whether or not to proliferate and migrate. The effects of soluble extracellular signals on these cellular functions are fairly well understood, but relatively little is known about how the extracellular matrix (ECM), and particularly the mechanical information in the ECM, guides these cellular decisions. Here, we show that CD44, a major receptor for the glycosaminoglycan ECM component hyaluronan, coordinates the motility and proliferative responses to ECM stiffening. We analyzed these cellular responses on fibronectin-coated polyacrylamide hydrogels prepared at a physiologic range of ECM stiffness and found that stiffening of the ECM leads to both cell cycling and cell motility in serum-stimulated primary mouse dermal fibroblasts. Remarkably, deletion of CD44 impaired stiffness-stimulated motility of the primary cells without affecting other hallmark cellular responses to ECM stiffening including cell spread area, stress fiber formation, focal adhesion maturation, and intracellular stiffening. Even stiffness-mediated cell proliferation was unaffected by deletion of CD44. Our results reveal a novel effect of CD44, which is imposed downstream of ECM-mechanosensing and determines if cells couple or uncouple their proliferative and motility responses to ECM stiffness.

Sensing of micropillars by osteoblasts involves complex intracellular signaling

Topographical material surface features are sensed by cells and provoke a large range of cellular responses. We recognized earlier, that at micropillar topographies in the range of 5 µm, the osteoblasts attempt to phagocytize the pillars resulted in increased energy requirements and reduced osteoblast marker expression, e.g., collagen type I and osteocalcin. However, the precise cellular signaling transducing the topographic information into the cell and evoking phagocytic processes remained unknown. Here, we could show that the RhoA/ROCK signaling is involved in the transduction of the topography-mediated cellular reactions. After inhibition of ROCK-2 with Y27632 for 24 h, no caveolae-mediated micropillar assembly of the cell membrane domain component caveolin-1 (Cav-1) was found. ROCK inhibition was also able to attenuate the pillar-induced decrease in β-actin. Interestingly, phosphatidylinositol 3-kinase (PI3K) inhibition with LY294002 for 24 h did not influence the Cav-1 clustering on micropillars. Our results illustrate the importance of the integrin down-stream signaling of RhoA/ROCK in the recognition of and adaption to surface microtopographies by osteoblasts and extend our understanding about the complex mechanism of action inside the cells.