Small Rho GTPases in the control of cell shape and mobility

Daily high doses of atorvastatin alter neuronal morphology in a juvenile songbird model

Statins are highly effective and widely prescribed cholesterol lowering drugs. However, statins cross the blood-brain barrier and decrease neural cholesterol in animal models, raising concern that long-term statin use may impact cholesterol-dependent structures and functions in the brain. Cholesterol is a fundamental component of cell membranes and experimentally decreasing membrane cholesterol has been shown to alter cell morphology in vitro. In addition, brain regions that undergo adult neurogenesis rely on local brain cholesterol for the manufacture of new neuronal membranes. Thus neurogenesis may be particularly vulnerable to long-term statin use. Here we asked whether oral statin treatment impacts neurogenesis in juveniles, either by decreasing numbers of new cells formed or altering the structure of new neurons. The use of statins in children and adolescents has received less attention than in older adults, with few studies on potential unintended effects in young brains. We examined neurons in the juvenile zebra finch songbird in telencephalic regions that function in song perception and memory (caudomedial nidopallium, NCM) and song production (HVC). Birds received either 40 mg/kg of atorvastatin in water or water vehicle once daily for 2-3 months until they reached adulthood. We labeled newborn cells using systemic injections of bromodeoxyuridine (BrdU) and quantified cells double-labeled with antibodies for BrdU and the neuron-specific protein Hu 30-32 days post mitosis. We also quantified a younger cohort of new neurons in the same birds using antibody to the neuronal protein doublecortin (DCX). We then compared numbers of new neurons and soma morphology of BrdU + /Hu+ neurons between statin-treated and control birds. We did not find an effect of statins on the density of newly formed neurons in either brain region, suggesting that statin treatment did not impact neurogenesis or young neuron survival in our paradigm. However, we found that neuronal soma morphology differed significantly between statin-treated and control birds. Somata of BrdU + /Hu+ (30-32 day old) neurons were flatter and had more furrowed contours in statin-treated birds relative to controls. In a larger, heterogeneous cohort of non-birthdated BrdU-/Hu+ neurons, largely born prior to statin treatment, somata were smaller in statin-treated birds than in controls. Our findings indicate that atorvastatin may affect neural cytoarchitecture in both newly formed and mature neurons, perhaps as a consequence of decreased cholesterol availability in the brain.

PPM1F regulates ovarian cancer progression by affecting the dephosphorylation of ITGB1

PPM1F has been shown to play diverse biological functions in the progression of multiple tumors. PPM1F controls the T788/T789 phosphorylation switch of ITGB1 and regulates integrin activity. However, the impacts of PPM1F and ITGB1 on ovarian cancer (OV) progression remain unclear. Whether there is such a regulatory relationship between PPM1F and ITGB1 in ovarian cancer has not been studied. Therefore, the purpose of this study is to elucidate the function and the mechanism of PPM1F in ovarian cancer. The expression level and the survival curve of PPM1F were analyzed by databases. Gain of function and loss of function were applied to explore the function of PPM1F in ovarian cancer. A tumor formation assay in nude mice showed that knockdown of PPM1F inhibited tumor formation. We tested the effect of PPM1F on ITGB1 dephosphorylation in ovarian cancer cells by co-immunoprecipitation and western blotting. Loss of function was applied to investigate the function of ITGB1 in ovarian cancer. ITGB1-mut overexpression promotes the progression of ovarian cancer. Rescue assays showed the promoting effect of ITGB1-wt on ovarian cancer is attenuated due to the dephosphorylation of ITGB1-wt by PPM1F. PPM1F and ITGB1 play an oncogene function in ovarian cancer. PPM1F regulates the phosphorylation of ITGB1, which affects the occurrence and development of ovarian cancer.

RhoA-ROCK2 signaling possesses complex pathophysiological functions in cancer progression and shows promising therapeutic potential

The Rho GTPase signaling pathway is responsible for cell-specific processes, including actin cytoskeleton organization, cell motility, cell division, and the transcription of specific genes. The implications of RhoA and the downstream effector ROCK2 in cancer epithelial-mesenchymal transition, migration, invasion, and therapy resistance associated with stem cells highlight the potential of targeting RhoA/ROCK2 signaling in therapy. Tumor relapse can occur due to cancer cells that do not fully respond to adjuvant chemoradiotherapy, targeted therapy, or immunotherapy. Rho signaling-mediated mitotic defects and cytokinesis failure lead to asymmetric cell division, allowing cells to form polyploids to escape cytotoxicity and promote tumor recurrence and metastasis. In this review, we elucidate the significance of RhoA/ROCK2 in the mechanisms of cancer progression and summarize their inhibitors that may improve treatment strategies.

Endometriosis and Sjögren's syndrome: Bidirectional associations in population-based 15-year retrospective cohorts

INTRODUCTION

Primary Sjögren's syndrome (pSS) is a chronic autoimmune disorder affecting salivary and lacrimal glands, while endometriosis involves uterine-like tissue growth outside the uterus, causing pelvic pain and infertility. Investigating their intricate relationship using real-world data is crucial due to limited research on their connection.

MATERIAL AND METHODS

This population-based cohort study included patients with endometriosis and controls without endometriosis. Propensity score matching was used to balance baseline differences in demographic and clinic characteristics between the two groups. Cox proportional hazards model were used to estimate the effect of endometriosis on the risk of new-onset pSS over time. A symmetrical cohort study, including patients with pSS and propensity score-matched controls without pSS, was conducted to investigate the effect of pSS on the risk of endometriosis over time. To elaborate on the mechanisms linking endometriosis and pSS, Ingenuity Pathway Analysis was performed to identify activated pathways in eutopic endometrium from patients with endometriosis and parotid tissues from patients with pSS.

RESULTS

A total of 15 947 patients with endometriosis and 15 947 propensity score-matched controls without endometriosis were included. Patients with endometriosis presented a significantly greater risk of pSS compared to non-endometriosis controls (adjusted hazard ratio, aHR = 1.57, 95% CI = 1.29-1.91, p < 0.001). In the symmetrical cohort study, which included 4906 pSS patients and 4,906 propensity score-matched controls without pSS, patients with pSS were found to be at a significantly higher risk of endometriosis compared to non-pSS controls (aHR = 1.51, 95% CI = 1.12-2.04, p = 0.012). Ingenuity Pathway Analysis showed that the underlying cellular mechanisms involved autoimmune-related pathways, including activation of dendritic cell maturation, and chronic inflammatory pathways, including the fibrosis signaling pathway.

CONCLUSIONS

These findings support a bidirectional association between endometriosis and pSS, which may be driven by dendritic cell maturation and fibrosis signaling pathways.

Differences and similarities in biophysical and biological characteristics between U87 MG glioblastoma and astrocyte cells

Current cancer studies focus on molecular-targeting diagnostics and interactions with surroundings; however, there are still gaps in characterization based on topological differences and elemental composition. Glioblastoma (GBM cells; GBMCs) is an astrocytic aggressive brain tumor. At the molecular level, GBMCs and astrocytes may differ, and cell elemental/topological analysis is critical for identifying potential new cancer targets. Here, we used U87 MG cells for GBMCS. U87 MG cell lines, which are frequently used in glioblastoma research, are an important tool for studying the various features and underlying mechanisms of this aggressive brain tumor. For the first time, atomic force microscopy (AFM), scanning electron microscopy (SEM) accompanied by energy-dispersive X-ray spectroscopy (EDS), and X-ray photoelectron spectroscopy (XPS) are used to report the topology and chemistry of cancer (U87 MG) and healthy (SVG p12) cells. In addition, F-actin staining and cytoskeleton-based gene expression analyses were performed. The degree of gene expression for genes related to the cytoskeleton was similar; however, the intensity of F-actin, anisotropy values, and invasion-related genes were different. Morphologically, GBMCs were longer and narrower while astrocytes were shorter and more disseminated based on AFM. Furthermore, the roughness values of these cells differed slightly between the two call types. In contrast to the rougher astrocyte surfaces in the lamellipodial area, SEM-EDS analysis showed that elongated GBMCs displayed filopodial protrusions. Our investigation provides considerable further insight into rapid cancer cell characterization in terms of a combinatorial spectroscopic and microscopic approach.

Maturation of a postsynaptic domain: Role of small Rho GTPases in organising nicotinic acetylcholine receptor aggregates at the vertebrate neuromuscular junction

The neuromuscular junction (NMJ) is the peripheral synapse formed between a motor axon and a skeletal muscle fibre that allows muscle contraction and the coordinated movement in many species. A main hallmark of the mature NMJ is the assembly of nicotinic acetylcholine receptor (nAChR) aggregates in the muscle postsynaptic domain, that distributes in perfect apposition to presynaptic motor terminals. To assemble its unique functional architecture, initial embryonic NMJs undergo an early postnatal maturation process characterised by the transformation of homogenous nAChR-containing plaques to elaborate and branched pretzel-like structures. In spite of a detailed morphological characterisation, the molecular mechanisms controlling the intracellular scaffolding that organises a postsynaptic domain at the mature NMJ have not been fully elucidated. In this review, we integrate evidence of key processes and molecules that have shed light on our current understanding of the NMJ maturation process. On the one hand, we consider in vitro studies revealing the potential role of podosome-like structures to define discrete low nAChR-containing regions to consolidate a plaque-to-pretzel transition at the NMJ. On the other hand, we focus on in vitro and in vivo evidence demonstrating that members of the Ras homologous (Rho) protein family of small GTPases (small Rho GTPases) play indispensable roles on NMJ maturation by regulating the stability of nAChR aggregates. We combine this evidence to propose that small Rho GTPases are key players in the assembly of podosome-like structures that drive the postsynaptic maturation of vertebrate NMJs.

Molecular basis of ocean acidification sensitivity and adaptation in Mytilus galloprovincialis

Predicting the potential for species adaption to climate change is challenged by the need to identify the physiological mechanisms that underpin species vulnerability. Here, we investigated the sensitivity to ocean acidification in marine mussels during early development, and specifically the trochophore stage. Using RNA and DNA sequencing and in situ RNA hybridization, we identified developmental processes associated with abnormal development and rapid adaptation to low pH. Trochophores exposed to low pH seawater exhibited 43 differentially expressed genes. Gene annotation and in situ hybridization of differentially expressed genes point to pH sensitivity of (1) shell field development and (2) cellular stress response. Five genes within these two processes exhibited shifts in allele frequencies indicative of a potential for rapid adaptation. This case study contributes direct evidence that protecting species’ existing genetic diversity is a critical management action to facilitate species resilience to climate change.

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Marine mussel larval development and genetic adaptation in low pH seawater

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RNA and DNA responses reveal impacts on shell field development and cell stress

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Five genes exhibited both physiological sensitivity and long-term adaptive potential

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Conserving standing genetic variation could bolster resilience to global change

Cdc42/Rac Interactive Binding Containing Effector Proteins in Unicellular Protozoans With Reference to Human Host: Locks of the Rho Signaling

Small GTPases are the key to actin cytoskeleton signaling, which opens the lock of effector proteins to forward the signal downstream in several cellular pathways. Actin cytoskeleton assembly is associated with cell polarity, adhesion, movement and other functions in eukaryotic cells. Rho proteins, specifically Cdc42 and Rac, are the primary regulators of actin cytoskeleton dynamics in higher and lower eukaryotes. Effector proteins, present in an inactive state gets activated after binding to the GTP bound Cdc42/Rac to relay a signal downstream. Cdc42/Rac interactive binding (CRIB) motif is an essential conserved sequence found in effector proteins to interact with Cdc42 or Rac. A diverse range of Cdc42/Rac and their effector proteins have evolved from lower to higher eukaryotes. The present study has identified and further classified CRIB containing effector proteins in lower eukaryotes, focusing on parasitic protozoans causing neglected tropical diseases and taking human proteins as a reference point to the highest evolved organism in the evolutionary trait. Lower eukaryotes’ CRIB containing proteins fall into conventional effector molecules, PAKs (p21 activated kinase), Wiskoit-Aldrich Syndrome proteins family, and some have unique domain combinations unlike any known proteins. We also highlight the correlation between the effector protein isoforms and their selective specificity for Cdc42 or Rac proteins during evolution. Here, we report CRIB containing effector proteins; ten in Dictyostelium and Entamoeba, fourteen in Acanthamoeba, one in Trypanosoma and Giardia. CRIB containing effector proteins that have been studied so far in humans are potential candidates for drug targets in cancer, neurological disorders, and others. Conventional CRIB containing proteins from protozoan parasites remain largely elusive and our data provides their identification and classification for further in-depth functional validations. The tropical diseases caused by protozoan parasites lack combinatorial drug targets as effective paradigms. Targeting signaling mechanisms operative in these pathogens can provide greater molecules in combatting their infections.

Cytoplasmic and Nuclear Functions of cIAP1

Cellular inhibitor of apoptosis 1 (cIAP1) is a cell signaling regulator of the IAP family. Through its E3-ubiquitine ligase activity, it has the ability to activate intracellular signaling pathways, modify signal transduction pathways by changing protein-protein interaction networks, and stop signal transduction by promoting the degradation of critical components of signaling pathways. Thus, cIAP1 appears to be a potent determinant of the response of cells, enabling their rapid adaptation to changing environmental conditions or intra- or extracellular stresses. It is expressed in almost all tissues, found in the cytoplasm, membrane and/or nucleus of cells. cIAP1 regulates innate immunity by controlling signaling pathways mediated by tumor necrosis factor receptor superfamily (TNFRs), some cytokine receptors and pattern recognition-receptors (PRRs). Although less documented, cIAP1 has also been involved in the regulation of cell migration and in the control of transcriptional programs.

TMEM16A inhibits angiotensin II-induced basilar artery smooth muscle cell migration in a WNK1-dependent manner

Vascular smooth muscle cell (VSMC) migration plays a critical role in the pathogenesis of many cardiovascular diseases. We recently showed that TMEM16A is involved in hypertension-induced cerebrovascular remodeling. However, it is unclear whether this effect is related to the regulation of VSMC migration. Here, we investigated whether and how TMEM16A contributes to migration in basilar artery smooth muscle cells (BASMCs). We observed that AngII increased the migration of cultured BASMCs, which was markedly inhibited by overexpression of TMEM16A. TMEM16A overexpression inhibited AngII-induced RhoA/ROCK2 activation, and myosin light chain phosphatase (MLCP) and myosin light chain (MLC20) phosphorylation. But AngII-induced myosin light chain kinase (MLCK) activation was not affected by TMEM16A. Furthermore, a suppressed activation of integrinβ3/FAK pathway, determined by reduced integrinβ3 expression, FAK phosphorylation and F-actin rearrangement, was observed in TMEM16A-overexpressing BASMCs upon AngII stimulation. Contrary to the results of TMEM16A overexpression, silencing of TMEM16A showed the opposite effects. These in vitro results were further demonstrated in vivo in basilar arteries from VSMC-specific TMEM16A transgenic mice during AngII-induced hypertension. Moreover, we observed that the inhibitory effect of TMEM16A on BASMC migration was mediated by decreasing the activation of WNK1, a Cl--sensitive serine/threonine kinase. In conclusion, this study demonstrated that TMEM16A suppressed AngII-induced BASMC migration, thus contributing to the protection against cerebrovascular remodeling during AngII-infused hypertension. TMEM16A may exert this effect by suppressing the RhoA/ROCK2/MLCP/MLC20 and integrinβ3/FAK signaling pathways via inhibiting WNK1. Our results suggest that TMEM16A may serve as a novel therapeutic target for VSMC migration-related diseases, such as vascular remodeling.

Increased Phosphatase of Regenerating Liver-1 by Placental Stem Cells Promotes Hepatic Regeneration in a Bile-Duct-Ligated Rat Model

Phosphatase of regenerating liver-1 (PRL-1) controls various cellular processes and liver regeneration. However, the roles of PRL-1 in liver regeneration induced by chorionic-plate-derived mesenchymal stem cells (CP-MSCs) transplantation remain unknown. Here, we found that increased PRL-1 expression by CP-MSC transplantation enhanced liver regeneration in a bile duct ligation (BDL) rat model by promoting the migration and proliferation of hepatocytes. Engrafted CP-MSCs promoted liver function via enhanced hepatocyte proliferation through increased PRL-1 expression in vivo and in vitro. Moreover, higher increased expression of PRL-1 regulated CP-MSC migration into BDL-injured rat liver through enhancement of migration-related signals by increasing Rho family proteins. The dual effects of PRL-1 on proliferation of hepatocytes and migration of CP-MSCs were substantially reduced when PRL-1 was silenced with siRNA-PRL-1 treatment. These findings suggest that PRL-1 may serve as a multifunctional enhancer for therapeutic applications of CP-MSC transplantation.

Regulation of NADPH Oxidase-Mediated Superoxide Production by Acetylation and Deacetylation

Oral treatment of apolipoprotein E-knockout (ApoE-KO) mice with the putative sirtuin 1 (SIRT1) activator resveratrol led to a reduction of nicotinamide adenine dinucleotide phosphate (NADPH) oxidase activity in the heart. In contrast, the SIRT1 inhibitor EX527 enhanced the superoxide production in isolated human polymorphonuclear granulocytes. In human monocytic THP-1 cells, phorbol ester-stimulated superoxide production was enhanced by inhibitors of histone deacetylases (HDACs; including quisinostat, trichostatin A (TSA), PCI34051, and tubastatin A) and decreased by inhibitors of histone acetyltransferases [such as garcinol, curcumin, and histone acetyltransferase (HAT) Inhibitor II]. These results indicate that protein acetylation and deacetylation may represent crucial mechanisms regulating NADPH oxidase-mediated superoxide production. In cell-free systems, incubation of recombinant Rac1 with SIRT1 resulted in decreased Rac1 acetylation. Mass spectrometry analyses identified lysine 166 (K166) in Rac1 as a residue targeted by SIRT1. Deacetylation of Rac1 by SIRT1 markedly reduced the interaction of Rac1 with p67phox in in vitro assays. Computational modeling analyses revealed that K166 deacetylation of Rac1 led to a 5-fold reduction in its binding affinity to guanosine-5'-triphosphate, and a 21-fold decrease in its binding potential to p67phox. The latter is crucial for Rac1-mediated recruitment of p67phox to the membrane and for p67phox activation. In conclusion, both SIRT1 and non-sirtuin deacetylases play a role in regulating NADPH oxidase activity. Rac1 can be directly deacetylated by SIRT1 in a cell-free system, leading to an inhibition of Rac1-p67phox interaction. The downstream targets of non-sirtuin deacetylases are still unknown. The in vivo significance of these findings needs to be investigated in future studies.

Bladder Cancer Invasion Is Mediated by Mammalian Target of Rapamycin Complex 2-Driven Regulation of Nitric Oxide and Invadopodia Formation

Bladder cancer invasion depends on mammalian target of rapamycin complex 2 (mTORC2) activity, although the downstream mTORC2 effectors that mediate this effect have not been fully defined. One potential downstream effector is the arginine derivative nitric oxide (NO). We identified a stage-associated increase in the expression of the NO-generating enzymes endothelial NO synthase (NOS) and inducible NOS (iNOS) in human bladder cancer. Reduction of NOS activity by pharmacologic inhibition or silencing of NOS enzymes reduced cancer cell invasion, with similar effects observed using the NO scavenger cobinamide. By contrast, enhanced invasion was seen with the NO donor Deta-NONOate and an analog of the downstream NO second messenger cGMP. We next evaluated NOS expression in invadopodia, which are cellular protrusions that form the invasive tips of cancer cells. Invadopodia were enriched in both iNOS protein and mTORC2 activity, and invadopodia formation was increased by Deta-NONOate and decreased by cobinamide and ablation of mTORC2 activity. mTORC2 additionally increased expression of iNOS. Using a zebrafish model, injection of iNOS- or rictor-silenced cells reduced the frequency of bladder cancer cell metastasis in zebrafish. These results indicate that mTORC2 can mediate bladder cancer cell invasion through increased iNOS expression, resulting in increased NO and cGMP production in invadopodia and further propagation of invadopodia formation.

Actin Remodeling Defects Leading to Autoinflammation and Immune Dysregulation

A growing number of monogenic immune-mediated diseases have been related to genes involved in pathways of actin cytoskeleton remodeling. Increasing evidences associate cytoskeleton defects to autoinflammatory diseases and primary immunodeficiencies. We reviewed the pathways of actin cytoskeleton remodeling in order to identify inflammatory and immunological manifestations associated to pathological variants. We list more than twenty monogenic diseases, ranging from pure autoinflammatory conditions as familial Mediterranean fever, mevalonate kinase deficiency and PAPA syndrome, to classic and novel primary immunodeficiencies as Wiskott-Aldrich syndrome and DOCK8 deficiency, characterized by the presence of concomitant inflammatory and autoimmune manifestations, such as vasculitis and cytopenia, to severe and recurrent infections. We classify these disorders according to the role of the mutant gene in actin cytoskeleton remodeling, and in particular as disorders of transcription, elongation, branching and activation of actin. This expanding field of rare immune disorders offers a new perspective to all immunologists to better understand the physiological and pathological role of actin cytoskeleton in cells of innate and adaptive immunity.

Actin Remodeling Defects Leading to Autoinflammation and Immune Dysregulation

A growing number of monogenic immune-mediated diseases have been related to genes involved in pathways of actin cytoskeleton remodeling. Increasing evidences associate cytoskeleton defects to autoinflammatory diseases and primary immunodeficiencies. We reviewed the pathways of actin cytoskeleton remodeling in order to identify inflammatory and immunological manifestations associated to pathological variants. We list more than twenty monogenic diseases, ranging from pure autoinflammatory conditions as familial Mediterranean fever, mevalonate kinase deficiency and PAPA syndrome, to classic and novel primary immunodeficiencies as Wiskott-Aldrich syndrome and DOCK8 deficiency, characterized by the presence of concomitant inflammatory and autoimmune manifestations, such as vasculitis and cytopenia, to severe and recurrent infections. We classify these disorders according to the role of the mutant gene in actin cytoskeleton remodeling, and in particular as disorders of transcription, elongation, branching and activation of actin. This expanding field of rare immune disorders offers a new perspective to all immunologists to better understand the physiological and pathological role of actin cytoskeleton in cells of innate and adaptive immunity.

Rho GTPases as Key Molecular Players within Intestinal Mucosa and GI Diseases

Rho proteins operate as key regulators of the cytoskeleton, cell morphology and trafficking. Acting as molecular switches, the function of Rho GTPases is determined by guanosine triphosphate (GTP)/guanosine diphosphate (GDP) exchange and their lipidation via prenylation, allowing their binding to cellular membranes and the interaction with downstream effector proteins in close proximity to the membrane. A plethora of in vitro studies demonstrate the indispensable function of Rho proteins for cytoskeleton dynamics within different cell types. However, only in the last decades we have got access to genetically modified mouse models to decipher the intricate regulation between members of the Rho family within specific cell types in the complex in vivo situation. Translationally, alterations of the expression and/or function of Rho GTPases have been associated with several pathological conditions, such as inflammation and cancer. In the context of the GI tract, the continuous crosstalk between the host and the intestinal microbiota requires a tight regulation of the complex interaction between cellular components within the intestinal tissue. Recent studies demonstrate that Rho GTPases play important roles for the maintenance of tissue homeostasis in the gut. We will summarize the current knowledge on Rho protein function within individual cell types in the intestinal mucosa in vivo, with special focus on intestinal epithelial cells and T cells.

The Physical Role of Mesenchymal Cells Driven by the Actin Cytoskeleton Is Essential for the Orientation of Collagen Fibrils in Zebrafish Fins

Fibrous collagen imparts physical strength and flexibility to tissues by forming huge complexes. The density and orientation of collagen fibers must be correctly specified for the optimal physical property of the collagen complex. However, little is known about its underlying cellular mechanisms. Actinotrichia are collagen fibers aligned at the fin-tip of bony fish and are easily visible under the microscope due to their thick, linear structure. We used the actinotrichia as a model system to investigate how cells manipulate collagen fibers. The 3D image obtained by focused ion beam scanning electron microscopy (FIB-SEM) showed that the pseudopodia of mesenchymal cells encircle the multiple actinotrichia. We then co-incubated the mesenchymal cells and actinotrichia in vitro, and time-lapse analysis revealed how cells use pseudopods to align collagen fiber orientation. This in vitro behavior is dependent on actin polymerization in mesenchymal cells. Inhibition of actin polymerization in mesenchymal cells results in mis-orientation of actinotrichia in the fin. These results reveal how mesenchymal cells are involved in fin formation and have important implications for the physical interaction between cells and collagen fibers.

Inhibition of Androgen Receptor Signaling Promotes Prostate Cancer Cell Migration via Upregulation of Annexin A1 Expression

BACKGROUND

Recent studies indicate that androgen deprivation therapy (ADT), the main therapeutic approach for metastatic prostate cancer (PCa), accelerates PCa invasion and metastasis. Annexin A1 (ANXA1) is a Ca²⁺-regulated phospholipid-binding protein that can promote PCa migration and invasion.

AIM OF THE STUDY

The aim of this study is to determine whether ANXA1 is regulated by ADT and participates in PCa progression after ADT, and to explore the possible mechanism of ANXA1-mediated PCa migration.

METHODS

Expression of ANXA1 and androgen receptor (AR) in PCa cell lines and tissues was detected, and the association between these two proteins were analyzed. Expression of ANXA1 was evaluated after AR knockdown or AR inhibition in PCa cell lines. Cell migration of PCa cell liness after ANXA1 knockdown or overexpression was determined by in vitro migration assay. Transcriptome analysis was used to explore the possible mechanism of ANXA1-mediated PCa migration.

RESULTS

ANXA1 expression in PCa cell lines and tissues was reversely associated with AR. In vitro studies revealed an increase in ANXA1 expression after AR knockdown or treatment with AR antagonist. Moreover, functional assays indicated that ANXA1 knockdown in PCa cells significantly inhibited cell migration, while ANXA1 overexpression in PCa cells significantly accelerated cell migration. Transcriptome analysis showed that ANXA1 regulated multiple genes involved in cell junction organization, such as CADM1, LIMCH1 and PPM1F.

CONCLUSIONS

Our results indicate that ADT might accelerate PCa metastasis via ANXA1 expression and PCa cell migration.

Partners in crime: POPX2 phosphatase and its interacting proteins in cancer

Protein phosphorylation and dephosphorylation govern intracellular signal transduction and cellular functions. Kinases and phosphatases are involved in the regulation and development of many diseases such as Alzheimer’s, diabetes, and cancer. While the functions and roles of many kinases, as well as their substrates, are well understood, phosphatases are comparatively less well studied. Recent studies have shown that rather than acting on fewer and more distinct substrates like the kinases, phosphatases can recognize specific phosphorylation sites on many different proteins, making the study of phosphatases and their substrates challenging. One approach to understand the biological functions of phosphatases is through understanding their protein–protein interaction network. POPX2 (Partner of PIX 2; also known as PPM1F or CaMKP) is a serine/threonine phosphatase that belongs to the PP2C family. It has been implicated in cancer cell motility and invasiveness. This review aims to summarize the different binding partners of POPX2 phosphatase and explore the various functions of POPX2 through its interactome in the cell. In particular, we focus on the impact of POPX2 on cancer progression. Acting via its different substrates and interacting proteins, POPX2’s involvement in metastasis is multifaceted and varied according to the stages of metastasis.

Reanalysis of Gene Expression Profiles of CD4+ T Cells Treated with HIV-1 Latency Reversal Agents

The human immunodeficiency virus (HIV-1) causes a progressive depletion of CD4+ T cells, hampering immune function. Current experimental strategies to fight the virus focus on the reactivation of latent HIV-1 in the viral reservoir to make the virus detectable by the immune system, by searching for latency reversal agents (LRAs). We hypothesize that if common molecular pathways elicited by the presence of LRAs are known, perhaps new, more efficient, “shock-and-kill” strategies can be found. Thus, the objective of the present study is to re-evaluate RNA-Seq assays to find differentially expressed genes (DEGs) during latency reversal via transcriptome analysis. We selected six studies (45 samples altogether: 16 negative controls and 29 LRA-treated CD4+ T cells) and 11 LRA strategies through a systematic search in Gene Expression Omnibus (GEO) and PubMed databases. The raw reads were trimmed, counted, and normalized. Next, we detected consistent DEGs in these independent experiments. AZD5582, romidepsin, and suberanilohydroxamic acid (SAHA) were the LRAs that modulated most genes. We detected 948 DEGs shared by those three LRAs. Gene ontology analysis and cross-referencing with other sources of the literature showed enrichment of cell activation, differentiation and signaling, especially mitogen-activated protein kinase (MAPK) and Rho-GTPases pathways.

Baicalein suppresses vasculogenic mimicry through inhibiting RhoA/ROCK expression in lung cancer A549 cell line

Vasculogenic mimicry (VM) refers to a new tubular network of the blood supply system with abundant extracellular matrix. VM is similar to capillaries but does not involve endothelial cells. As a traditional herbal medicine commonly used in China, baicalein possesses anti-inflammatory and lipoxygenase activities. However, the effects of baicalein on the process of VM formation in non-small cell lung cancer (NSCLC) and the underlying mechanisms have remained poorly understood. In this study, baicalein was found to inhibit the viability and motility of A549 cells and induced the breakage of the cytoskeletal actin filament network. In addition, baicalein significantly decreased the formation of VM and downregulated the expressions of VM-associated factors, such as VE-cadherin, EphA2, MMP14, MMP2, MMP9, PI3K and LAMC2, similar to the effects of ROCK inhibitors. Indeed, baicalein inhibited RhoA/ROCK expression in vitro and in vivo, suggesting the underlying mechanisms of reduced VM formation. Collectively, baicalein suppressed the formation of VM in NSCLC by targeting the RhoA/ROCK signaling pathway, indicating that baicalein might serve as an emerging drug for NSCLC.

Regulation of Eosinophil Recruitment and Allergic Airway Inflammation by Tropomyosin Receptor Kinase A

Eosinophilia is a hallmark of allergic airway inflammation (AAI). Identifying key molecules and specific signaling pathways that regulate eosinophilic inflammation is critical for development of novel therapeutics. Tropomycin receptor kinase A (TrkA) is the high-affinity receptor for nerve growth factor. AAI is associated with increased expression of TrkA by eosinophils; however, the functional role of TrkA in regulating eosinophil recruitment and contributing to AAI is poorly understood. This study identifies, to our knowledge, a novel mechanism of eotaxin-mediated activation of TrkA and its role in regulating eosinophil recruitment by using a chemical-genetic approach to specifically inhibit TrkA kinase activity with 1-NM-PP1 in TrkAF592A-knock-in (TrkA-KI) eosinophils. Blockade of TrkA by 1-NM-PP1 enhanced eosinophil spreading on VCAM-1 but inhibited eotaxin-1 (CCL11)-mediated eosinophil migration, calcium flux, cell polarization, and ERK1/2 activation, suggesting that TrkA is an important player in the signaling pathway activated by eotaxin-1 during eosinophil migration. Further, blockade of matrix metalloprotease with BB-94 inhibited eotaxin-1-induced TrkA activation and eosinophil migration, additively with 1-NM-PP1, indicating a role for matrix metalloproteases in TrkA activation. TrkA inhibition in Alternaria alternata-challenged TrkA-KI mice markedly inhibited eosinophilia and attenuated various features of AAI. These findings are indicative of a distinctive eotaxin-mediated TrkA-dependent signaling pathway, which, in addition to other TrkA-activating mediators, contributes to eosinophil recruitment during AAI and suggests that targeting the TrkA signaling pathway to inhibit eosinophil recruitment may serve as a therapeutic strategy for management of eosinophilic inflammation in allergic airway disease, including asthma.

Myeloid HMG-CoA Reductase Determines Adipose Tissue Inflammation, Insulin Resistance, and Hepatic Steatosis in Diet-Induced Obese Mice

Adipose tissue macrophages (ATMs) are involved in the development of insulin resistance in obesity. We have recently shown that myeloid cell-specific reduction of HMG-CoA reductase (Hmgcr ^m-/m- ), which is the rate-limiting enzyme in cholesterol biosynthesis, protects against atherosclerosis by inhibiting macrophage migration in mice. We hypothesized that ATMs are harder to accumulate in Hmgcr ^m-/m- mice than in control Hmgcr ^fl/fl mice in the setting of obesity. To test this hypothesis, we fed Hmgcr ^m-/m- and Hmgcr ^fl/fl mice a high-fat diet (HFD) for 24 weeks and compared plasma glucose metabolism as well as insulin signaling and histology between the two groups. Myeloid cell-specific reduction of Hmgcr improved glucose tolerance and insulin sensitivity without altering body weight in the HFD-induced obese mice. The improvement was due to a decrease in the number of ATMs. The ATMs were reduced by decreased recruitment of macrophages as a result of their impaired chemotactic activity. These changes were associated with decreased expression of proinflammatory cytokines in adipose tissues. Myeloid cell-specific reduction of Hmgcr also attenuated hepatic steatosis. In conclusion, reducing myeloid HMGCR may be a promising strategy to improve insulin resistance and hepatic steatosis in obesity.

Cerebral Cavernous Malformation Proteins in Barrier Maintenance and Regulation

Cerebral cavernous malformation (CCM) is a disease characterized by mulberry shaped clusters of dilated microvessels, primarily in the central nervous system. Such lesions can cause seizures, headaches, and stroke from brain bleeding. Loss-of-function germline and somatic mutations of a group of genes, called CCM genes, have been attributed to disease pathogenesis. In this review, we discuss the impact of CCM gene encoded proteins on cellular signaling, barrier function of endothelium and epithelium, and their contribution to CCM and potentially other diseases.

Proteoglycan serglycin promotes non-small cell lung cancer cell migration through the interaction of its glycosaminoglycans with CD44

Background

Serglycin (SRGN), previously recognized as an intracellular proteoglycan involved in the storage processes of secretory granules, has recently been shown to be upregulated in several solid tumors. We have previously shown that SRGN in non-small cell lung cancer (NSCLC) promotes malignant phenotypes in a CD44-dependent manner and increased expression of SRGN predicts poor prognosis of primary lung adenocarcinomas. However, the underlying mechanism remains to be defined.

Methods

Overexpression, knockdown and knockout approaches were performed to assess the role of SRGN in cell motility using wound healing and Boyden chamber migration assays. SRGN devoid of glycosaminoglycan (GAG) modification was produced by site-directed mutagenesis or chondroitinase treatment. Liquid chromatography/tandem mass spectrometry was applied for quantitative analysis of the disaccharide compositions and sulfation extent of SRGN GAGs. Western blot and co-immunoprecipitation analyses were performed to determine the expression and interaction of proteins of interest. Actin cytoskeleton organization was monitored by immunofluorescence staining.

Results

SRGN expressed by NSCLC cells is readily secreted to the extracellular matrix in a heavily glycosylated form attached with mainly chondroitin sulfate (CS)-GAG chains, and to a lesser extent with heparin sulfate (HS). The CS-GAG moiety serves as the structural motif for SRGN binding to tumor cell surface CD44 and promotes cell migration. SRGN devoid of CS-GAG modification fails to interact with CD44 and has lost the ability to promote cell migration. SRGN/CD44 interaction promotes focal adhesion turnover via Src-mediated paxillin phosphorylation and disassembly of paxillin/FAK adhesion complex, facilitating cell migration. In support, depletion of Src activity or removal of CS-GAGs efficiently blocks SRGN-mediated Src activation and cell migration. SRGN also promotes cell migration via inducing cytoskeleton reorganization mediated through RAC1 and CDC42 activation accompanied with increased lamellipodia and filopodia formation.

Conclusions

Proteoglycan SRGN promotes NSCLC cell migration via the binding of its GAG motif to CD44. SRGN/CD44 interaction induces Rho-family GTPase-mediated cytoskeleton reorganization and facilitates Src-mediated focal adhesion turnover, leading to increased cell migration. These findings suggest that targeting specific glycans in tumor microenvironment that serve as ligands for oncogenic pathways may be a potential strategy for cancer therapy.

Genomic imbalances defining novel intellectual disability associated loci

Background

High resolution genome-wide copy number analysis, routinely used in clinical diagnosis for several years, retrieves new and extremely rare copy number variations (CNVs) that provide novel candidate genes contributing to disease etiology. The aim of this work was to identify novel genetic causes of neurodevelopmental disease, inferred from CNVs detected by array comparative hybridization (aCGH), in a cohort of 325 Portuguese patients with intellectual disability (ID).

Results

We have detected CNVs in 30.1% of the patients, of which 5.2% corresponded to novel likely pathogenic CNVs. For these 11 rare CNVs (which encompass novel ID candidate genes), we identified those most likely to be relevant, and established genotype-phenotype correlations based on detailed clinical assessment. In the case of duplications, we performed expression analysis to assess the impact of the rearrangement. Interestingly, these novel candidate genes belong to known ID-related pathways. Within the 8% of patients with CNVs in known pathogenic loci, the majority had a clinical presentation fitting the phenotype(s) described in the literature, with a few interesting exceptions that are discussed.

Conclusions

Identification of such rare CNVs (some of which reported for the first time in ID patients/families) contributes to our understanding of the etiology of ID and for the ever-improving diagnosis of this group of patients.

Electronic supplementary material

The online version of this article (10.1186/s13023-019-1135-0) contains supplementary material, which is available to authorized users.

Role of Berry Anthocyanins and Phenolic Acids on Cell Migration and Angiogenesis: An Updated Overview

Cell migration is a critical process that is highly involved with normal and pathological conditions such as angiogenesis and wound healing. Important members of the RHO GTPase family are capable of controlling cytoskeleton conformation and altering motility characteristics of cells. There is a well-known relationship between small GTPases and the PI3K/AKT pathway. Endothelial cell migration can lead to angiogenesis, which is highly linked to wound healing processes. Phenolics, flavonoids, and anthocyanins are major groups of phytochemicals and are abundant in many natural products. Their antioxidant, antimicrobial, anti-inflammatory, antidiabetic, angiogenenic, neuroprotective, hepatoprotective, and cardioprotective properties have been extensively documented. This comprehensive review focuses on the in vitro and in vivo role of berry extracts and single anthocyanin and phenolic acid compounds on cell migration and angiogenesis. We aim to summarize the most recent published studies focusing on the experimental model, type of berry extract, source, dose/concentration and overall effect(s) of berry extracts, anthocyanins, and phenolic acids on the above processes.

RhoGDI2 positively regulates the Rho GTPases activation in response to the β2 outside-in signaling in T cells adhesion and migration on ICAM-1

Cytoskeletal reorganization driven by Rho GTPases plays a crucial role in the migration of T cells, which are key regulators of immunity. The molecular mechanisms that control actin cytoskeleton remodeling during T cell movement have only partially been clarified as the function of many modulators has not been evaluated in these cells. Here, we report a new function of RhoGDI2 by showing that this protein positively regulates Rho GTPase activation during T cell adhesion and migration. RhoGDI2 knockdown significantly reduced T cell adhesion and migration. Furthermore, RhoGDI2 knockdown decreased the activation of Rac1 and Cdc42, 2 members of Rho GTPases, and the remodeling of the actin cytoskeleton. Upon P-selectin glycoprotein ligand-1 engagement, RhoGDI2 was phosphorylated at Y24 and Y153 by kinases related to β2 integrin outside-in signaling, Src, c-Abl, and Syk, resulting in the accumulation of RhoGDI2 at the cell membrane. Subsequent phosphorylation of S31 induced the opening of RhoGDI2 and the release of Rho GTPases, whereas phosphorylation of Y153 might promote the activation of Rho GTPases by recruiting Vav1. Moreover, the disruption of lipid rafts with methyl-β-cyclodextrin blocked the interaction between integrins and RhoGDI2, reducing the level of phosphorylated RhoGDI2 and the activation of downstream Rho GTPases. Based on these observations, RhoGDI2 is a target of intergrin outside-in signaling that activates Rho GTPases during T cell adhesion and migration, and RhoGDI2-mediated signal transduction is based on the lipid rafts integrity.

N-myc downstream-regulated gene 2 controls astrocyte morphology via Rho-GTPase signaling

Astrocyte undergoes morphology changes that are closely associated with the signaling communications at synapses. N-myc downstream-regulated gene 2 (NDRG2) is specifically expressed in astrocytes and is associated with several important astrocyte functions, but its potential role(s) relating to astrocyte morphological changes remain unknown. Here, primary astrocytes were prepared from neonatal Ndrg2^+/+ and Ndrg2^-/- pups, and the drug Y27632 was used to induce stellation. We then used a variety of methods to measure the levels of NDRG2, α-Actinin4, and glial fibrillary acidic protein (GFAP), and the activity of RhoA, Rac1, and Cdc42 in Y27632-treated astrocytes as well as in Ndrg2^+/+ , Ndrg2^-/- , or Ndrg2^-/-  + lentivirus (restore NDRG2 expression) astrocytes. We also conducted live-imaging and proteomics studies of the cultured astrocytes. We found that induction of astrocytes stellation (characterized by cytoplasmic retraction and process outgrowth) resulted in increased NDRG2 protein expression and Rac1 activity and in reduced α-Actinin4 protein expression and RhoA activity. Ndrg2 deletion induced astrocyte flattening, whereas the restoration of NDRG2 expression induced stellation. Ndrg2 deletion also significantly increased α-Actinin4 protein expression and RhoA activity yet reduced GFAP protein expression and Rac1 activity, and these trends were reversed by restoration of NDRG2 expression. Collectively, our results showed that Ndrg2 deletion promoted cell proliferation, interrupted stellation capability, and extensively altered the protein expression profiles of proteins that function in Rho-GTPase signaling. These findings suggest that NDRG2 functions to regulate astrocytes morphology via altering the accumulation of the Rho-GTPase signaling pathway components, thereby supporting that NDRG2 should be understood as a regulator of synaptic plasticity and thus neuronal communications.

Cholecystokinin (CCK) Regulation of Pancreatic Acinar Cells: Physiological Actions and Signal Transduction Mechanisms

Pancreatic acinar cells synthesize and secrete about 20 digestive enzymes and ancillary proteins with the processes that match the supply of these enzymes to their need in digestion being regulated by a number of hormones (CCK, secretin and insulin), neurotransmitters (acetylcholine and VIP) and growth factors (EGF and IGF). Of these regulators, one of the most important and best studied is the gastrointestinal hormone, cholecystokinin (CCK). Furthermore, the acinar cell has become a model for seven transmembrane, heterotrimeric G protein coupled receptors to regulate multiple processes by distinct signal transduction cascades. In this review, we briefly describe the chemistry and physiology of CCK and then consider the major physiological effects of CCK on pancreatic acinar cells. The majority of the review is devoted to the physiologic signaling pathways activated by CCK receptors and heterotrimeric G proteins and the functions they affect. The pathways covered include the traditional second messenger pathways PLC-IP3-Ca²⁺ , DAG-PKC, and AC-cAMP-PKA/EPAC that primarily relate to secretion. Then there are the protein-protein interaction pathways Akt-mTOR-S6K, the three major MAPK pathways (ERK, JNK, and p38 MAPK), and Ca²⁺ -calcineurin-NFAT pathways that primarily regulate non-secretory processes including biosynthesis and growth, and several miscellaneous pathways that include the Rho family small G proteins, PKD, FAK, and Src that may regulate both secretory and nonsecretory processes but are not as well understood. © 2019 American Physiological Society. Compr Physiol 9:535-564, 2019.

Roles of EphA1/A2 and ephrin-A1 in cancer

The biological functions of the Eph/ephrin system have been intensively investigated and well documented so far since its discovery in 1987. Although the Eph/ephrin system has been implicated in pathological settings such as Alzheimer's disease and cancer, the molecular mechanism of the Eph/ephrin system in those diseases is not well understood. Especially in cancer, recent studies have demonstrated that most of Eph and ephrin are up‐ or down‐regulated in various types of cancer, and have been implicated in tumor progression, tumor malignancy, and prognosis. However, they lack consistency and are in controversy. The localization patterns of EphA1 and EphA2 in mouse lungs are very similar, and both knockout mice showed similar phenotypes in the lungs. Ephrin‐A1 that is a membrane‐anchored ligand for EphAs was co‐localized with EphA1 and EphA2 in lung vascular endothelial cells. We recently uncovered the molecular mechanism of ephrin‐A1‐induced lung metastasis by understanding the physiological function of ephrin‐A1 in lungs. This review focuses on the function of EphA1, EphA2, and ephrin‐A1 in tumors and an establishment of pre‐metastatic microenvironment in the lungs.

Pak1 gene functioned differentially in different BCR-ABL subtypes in leukemiagenesis and treatment response through STAT5 pathway

The BCR-ABL fusion gene (BCR-ABL) has different subtypes such as p210 and p190 with p190 appear to lead to a worse prognosis. To explore the mechanism of difference in pathogenesis and prognosis in different BCR-ABL subtype-related leukemia, expression profile microarray analysis was conducted between p190 and p210 patients and verified by RT-PCR. The p21-activated kinase (PAK1) gene was chosen and regulation of the PAK1-STAT5 biological axis and its influence on proliferation and apoptosis in leukemia cells were also analyzed. The results showed that PAK1 might be an important molecular mechanism of the pathogenic difference between different BCR-ABL subtypes. In P210 (+) chronic myelogenous leukemia (CML), down-regulated PAK1 gene expressions may lead to the suppression of cell proliferation and promotion of apoptosis through phosphorylation of STAT5, with a reverse effect in P190 (+) acute lymphoblastic leukemia(ALL), especially acute B lymphoblastic leukemia (B-ALL). Additionally, in P210 (+) CML, down-regulated PAK1 expression may enhance the effect of TKI, whereas the reverse is true in P190 (+) B-ALL, demonstrating that PAK1 might also be an important therapeutic target between different BCR-ABL subtypes.

Hnrnpab regulates neural cell motility through transcription of Eps8

Cell migration requires a complicated network of structural and regulatory proteins. Changes in cellular motility can impact migration as a result of cell-type or developmental stage regulated expression of critical motility genes. Hnrnpab is a conserved RNA-binding protein found as two isoforms produced by alternative splicing. Its expression is enriched in the subventricular zone (SVZ) and the rostral migratory stream within the brain, suggesting possible support of the migration of neural progenitor cells in this region. Here we show that the migration of cells from the SVZ of developing Hnrnpab^-/- mouse brains is impaired. An RNA-seq analysis to identify Hnrnpab-dependent cell motility genes led us to Eps8, and in agreement with the change in cell motility, we show that Eps8 is decreased in Hnrnpab^-/- SVZ tissue. We scrutinized the motility of Hnrnpab^-/- cells and confirmed that the decreases in both cell motility and Eps8 are restored by ectopically coexpressing both alternatively spliced Hnrnpab isoforms, therefore these variants are surprisingly nonredundant for cell motility. Our results support a model where both Hnrnpab isoforms work in concert to regulate Eps8 transcription in the mouse SVZ to promote the normal migration of neural cells during CNS development.

mDia1 and Cdc42 Regulate Activin B-Induced Migration of Bone Marrow-Derived Mesenchymal Stromal Cells

In a previous study, we have shown that Activin B is a potent chemoattractant for bone marrow-derived mesenchymal stromal cells (BMSCs). As such, the combination of Activin B and BMSCs significantly accelerated rat skin wound healing. In another study, we showed that RhoA activation plays a key role in Activin B-induced BMSC migration. However, the role of the immediate downstream effectors of RhoA in this process is unclear. Here, we demonstrated that mammalian homolog of Drosophila diaphanous-1 (mDia1), a downstream effector of RhoA, exerts a crucial function in Activin B-induced BMSC migration by promoting membrane ruffling, microtubule morphology, and adhesion signaling dynamics. Furthermore, we showed that Activin B does not change Rac1 activity but increases Cdc42 activity in BMSCs. Inactivation of Cdc42 inhibited Activin B-stimulated Golgi reorientation and the cell migration of BMSCs. Furthermore, knockdown of mDia1 affected Activin B-induced BMSC-mediated wound healing in vivo. In conclusion, this study demonstrated that the RhoA-mDia1 and Cdc42 pathways regulate Activin B-induced BMSC migration. This study may help to optimize clinical MSC-based transplantation strategies to promote skin wound healing. Stem Cells 2019;37:150-162.

Serotonin uptake is required for Rac1 activation in Kras-induced acinar-to-ductal metaplasia in the pancreas

Pancreatic ductal adenocarcinoma (PDAC), which is the primary cause of pancreatic cancer mortality, is poorly responsive to currently available interventions. Identifying new targets that drive PDAC formation and progression is critical for developing alternative therapeutic strategies to treat this lethal malignancy. Using genetic and pharmacological approaches, we investigated in vivo and in vitro whether uptake of the monoamine serotonin [5-hydroxytryptamine (5-HT)] is required for PDAC development. We demonstrated that pancreatic acinar cells have the ability to readily take up 5-HT in a transport-mediated manner. 5-HT uptake promoted activation of the small GTPase Ras-related C3 botulinum toxin substrate 1 (Rac1), which is required for transdifferentiation of acinar cells into acinar-to-ductal metaplasia (ADM), a key determinant in PDAC development. Consistent with the central role played by Rac1 in ADM formation, inhibition of the 5-HT transporter Sert (Slc6a4) with fluoxetine reduced ADM formation both in vitro and in vivo in a cell-autonomous manner. In addition, fluoxetine treatment profoundly compromised the stromal reaction and affected the proliferation and lipid metabolism of malignant PDAC cells. We propose that Sert is a promising therapeutic target to counteract the early event of ADM, with the potential to stall the initiation and progression of pancreatic carcinogenesis. Copyright © 2018 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Targeting Rac and Cdc42 GTPases in Cancer

Rac and Cdc42 are small GTPases that have been linked to multiple human cancers and are implicated in epithelial to mesenchymal transition, cell-cycle progression, migration/invasion, tumor growth, angiogenesis, and oncogenic transformation. With the exception of the P29S driver mutation in melanoma, Rac and Cdc42 are not generally mutated in cancer, but are overexpressed (gene amplification and mRNA upregulation) or hyperactivated. Rac and Cdc42 are hyperactivated via signaling through oncogenic cell surface receptors, such as growth factor receptors, which converge on the guanine nucleotide exchange factors that regulate their GDP/GTP exchange. Hence, targeting Rac and Cdc42 represents a promising strategy for precise cancer therapy, as well as for inhibition of bypass signaling that promotes resistance to cell surface receptor-targeted therapies. Therefore, an understanding of the regulatory mechanisms of these pivotal signaling intermediates is key for the development of effective inhibitors. In this review, we focus on the role of Rac and Cdc42 in cancer and summarize the regulatory mechanisms, inhibitory efficacy, and the anticancer potential of Rac- and Cdc42-targeting agents. Cancer Res; 78(12); 3101-11. ©2018 AACR.

Global phenotypic characterisation of human platelet lysate expanded MSCs by high-throughput flow cytometry

Mesenchymal stromal cells (MSCs) are a promising cell source to develop cell therapy for many diseases. Human platelet lysate (PLT) is increasingly used as an alternative to foetal calf serum (FCS) for clinical-scale MSC production. To date, the global surface protein expression of PLT-expended MSCs (MSC-PLT) is not known. To investigate this, paired MSC-PLT and MSC-FCS were analysed in parallel using high-throughput flow cytometry for the expression of 356 cell surface proteins. MSC-PLT showed differential surface protein expression compared to their MSC-FCS counterpart. Higher percentage of positive cells was observed in MSC-PLT for 48 surface proteins, of which 13 were significantly enriched on MSC-PLT. This finding was validated using multiparameter flow cytometry and further confirmed by quantitative staining intensity analysis. The enriched surface proteins are relevant to increased proliferation and migration capacity, as well as enhanced chondrogenic and osteogenic differentiation properties. In silico network analysis revealed that these enriched surface proteins are involved in three distinct networks that are associated with inflammatory responses, carbohydrate metabolism and cellular motility. This is the first study reporting differential cell surface protein expression between MSC-PLT and MSC-FSC. Further studies are required to uncover the impact of those enriched proteins on biological functions of MSC-PLT.

All-Round Manipulation of the Actin Cytoskeleton by HIV

While significant progress has been made in terms of human immunodeficiency virus (HIV) therapy, treatment does not represent a cure and remains inaccessible to many people living with HIV. Continued mechanistic research into the viral life cycle and its intersection with many aspects of cellular biology are not only fundamental in the continued fight against HIV, but also provide many key observations of the workings of our immune system. Decades of HIV research have testified to the integral role of the actin cytoskeleton in both establishing and spreading the infection. Here, we review how the virus uses different strategies to manipulate cellular actin networks and increase the efficiency of various stages of its life cycle. While some HIV proteins seem able to bind to actin filaments directly, subversion of the cytoskeleton occurs indirectly by exploiting the power of actin regulatory proteins, which are corrupted at multiple levels. Furthermore, this manipulation is not restricted to a discrete class of proteins, but rather extends throughout all layers of the cytoskeleton. We discuss prominent examples of actin regulators that are exploited, neutralized or hijacked by the virus, and address how their coordinated deregulation can lead to changes in cellular behavior that promote viral spreading.

Three-dimensional hydrogel is suitable for targeted investigation of amoeboid migration of glioma cells

Glioblastoma (GBM) invasion and migration are key biological behaviors leading to refractoriness to current therapies and infiltration into the non-tumor brain parenchyma. GBM cell migration is strongly dependent on tumor architecture in vivo, which is absent in traditional two-dimensional (2D) monolayer culture. The present study applied a three-dimensional (3D) hydrogel model to rebuild the tumor architecture in vitro. Treatment with NSC23766, a specific inhibitor of Ras-related C3 botulinum toxin substrate 1 (Rac1), inhibited the mesenchymal invasiveness however triggered the amoeboid motility called mesenchymal-amoeboid transition (MAT). Notably, NSC23766 stimulated U87 GBM cell migration in the 3D hydrogel. However, this compound inhibited cell motility in 2D monolayer culture without tumor architecture for MAT, suggesting the advantage of 3D hydrogel to investigate tumor cell invasion. Due to the inverse interaction of Rac1 and Ras homolog family member A (RhoA) signaling in the transition between mesenchymal and amoeboid morphology, simultaneous treatment of NSC23766 and Y27632 (selective Rho associated coiled-coil containing protein kinase 1 inhibitor), abolished U87 GBM cell migration through inhibiting MAT and amoeboid-mesenchymal transition. In addition, Y27632 induced integrin expression which gave rise to the focal adhesion to facilitate the mesenchymal invasion. The results of the present study demonstrated that the 3D hydrogel was a preferable model in vitro to study tumor cell invasion and migration. The combined inhibition of Rac1 and RhoA signaling would be a promising strategy to suppress GBM invasion.

Rac Attack: Modulation of the Small GTPase Rac in Inflammatory Bowel Disease and Thiopurine Therapy

The incidence and prevalence of inflammatory bowel disease (IBD) are increasing. Although the etiology of IBD is unknown, it is thought that genetically susceptible individuals display an inappropriate inflammatory response to commensal microbes, resulting in intestinal tissue damage. Key proteins involved in regulating the immune response, and thus in inflammation, are the small triphosphate-binding protein Rac and its regulatory network. Recent data suggest these proteins to be involved in (dys)regulation of the characteristic inflammatory processes in IBD. Moreover, Rac-gene variants have been identified as susceptibility risk factors for IBD, and Rac1 GTPase signaling has been shown to be strongly suppressed in non-inflamed mucosa compared with inflamed colonic mucosa in IBD. In addition, first-line immunosuppressive treatment for IBD includes thiopurine therapy, and its immunosuppressive effect is primarily ascribed to Rac1 suppression. In this review, we focus on Rac modification and its potential role in the development of IBD, Rac as the molecular therapeutic target in current thiopurine therapy, and the modulation of the Rac signal transduction pathway as a promising novel therapeutic strategy.

Tipifarnib prevents development of hypoxia-induced pulmonary hypertension

Aims

RhoB plays a key role in the pathogenesis of hypoxia-induced pulmonary hypertension. Farnesylated RhoB promotes growth responses in cancer cells and we investigated whether inhibition of protein farnesylation will have a protective effect.

Methods and results

The analysis of lung tissues from rodent models and pulmonary hypertensive patients showed increased levels of protein farnesylation. Oral farnesyltransferase inhibitor tipifarnib prevented development of hypoxia-induced pulmonary hypertension in mice. Tipifarnib reduced hypoxia-induced vascular cell proliferation, increased endothelium-dependent vasodilatation and reduced vasoconstriction of intrapulmonary arteries without affecting cell viability. Protective effects of tipifarnib were associated with inhibition of Ras and RhoB, actin depolymerization and increased eNOS expression in vitro and in vivo. Farnesylated-only RhoB (F-RhoB) increased proliferative responses in cultured pulmonary vascular cells, mimicking the effects of hypoxia, while both geranylgeranylated-only RhoB (GG-RhoB), and tipifarnib had an inhibitory effect. Label-free proteomics linked F-RhoB with cell survival, activation of cell cycle and mitochondrial biogenesis. Hypoxia increased and tipifarnib reduced the levels of F-RhoB-regulated proteins in the lung, reinforcing the importance of RhoB as a signalling mediator. Unlike simvastatin, tipifarnib did not increase the expression levels of Rho proteins.

Conclusions

Our study demonstrates the importance of protein farnesylation in pulmonary vascular remodelling and provides a rationale for selective targeting of this pathway in pulmonary hypertension.

RhoB blockade selectively inhibits autoantibody production in autoimmune models of rheumatoid arthritis and lupus

During the development of autoimmune disease, a switch occurs in the antibody repertoire of B cells so that the production of pathogenic rather than non-pathogenic autoantibodies is enabled. However, there is limited knowledge concerning how this pivotal step occurs. Here, we present genetic and pharmacological evidence of a positive modifier function for the vesicular small GTPase RhoB in specifically mediating the generation of pathogenic autoantibodies and disease progression in the K/BxN preclinical mouse model of inflammatory arthritis. Genetic deletion of RhoB abolished the production of pathogenic autoantibodies and ablated joint inflammation in the model. Similarly, administration of a novel RhoB-targeted monoclonal antibody was sufficient to ablate autoantibody production and joint inflammation. In the MRL/lpr mouse model of systemic lupus erythematosus (SLE), another established preclinical model of autoimmune disease associated with autoantibody production, administration of the anti-RhoB antibody also reduced serum levels of anti-dsDNA antibodies. Notably, the therapeutic effects of RhoB blockade reflected a selective deficiency in response to self-antigens, insofar as RhoB-deficient mice and mice treated with anti-RhoB immunoglobulin (Ig) both mounted comparable productive antibody responses after immunization with a model foreign antigen. Overall, our results highlight a newly identified function for RhoB in supporting the specific production of pathogenic autoantibodies, and offer a preclinical proof of concept for use of anti-RhoB Ig as a disease-selective therapy to treat autoimmune disorders driven by pathogenic autoantibodies.

The Dynamic Actin Cytoskeleton in Smooth Muscle

Smooth muscle contraction requires both myosin activation and actin cytoskeletal remodeling. Actin cytoskeletal reorganization facilitates smooth muscle contraction by promoting force transmission between the contractile unit and the extracellular matrix (ECM), and by enhancing intercellular mechanical transduction. Myosin may be viewed to serve as an "engine" for smooth muscle contraction whereas the actin cytoskeleton may function as a "transmission system" in smooth muscle. The actin cytoskeleton in smooth muscle also undergoes restructuring upon activation with growth factors or the ECM, which controls smooth muscle cell proliferation and migration. Abnormal smooth muscle contraction, cell proliferation, and motility contribute to the development of vascular and pulmonary diseases. A number of actin-regulatory proteins including protein kinases have been discovered to orchestrate actin dynamics in smooth muscle. In particular, Abelson tyrosine kinase (c-Abl) is an important molecule that controls actin dynamics, contraction, growth, and motility in smooth muscle. Moreover, c-Abl coordinates the regulation of blood pressure and contributes to the pathogenesis of airway hyperresponsiveness and vascular/airway remodeling in vivo. Thus, c-Abl may be a novel pharmacological target for the development of new therapy to treat smooth muscle diseases such as hypertension and asthma.

CXCR5-Overexpressing Mesenchymal Stromal Cells Exhibit Enhanced Homing and Can Decrease Contact Hypersensitivity

Mesenchymal stromal cells (MSCs) can modulate inflammation and contribute to tissue regeneration and, thus, have emerged as a promising option for cell-based therapy. However, the ability of MSCs to migrate to injured tissues still needs to be improved. In this study, we investigated whether genetically engineered MSCs could exhibit increased migratory properties and improved therapeutic efficacy. Using a mouse model of contact hypersensitivity (CHS), chemokine gene expression screening revealed that CXCL13 changed most significantly in injured tissue. Unfortunately, MSCs hardly express the corresponding receptor, CXCR5. Thus, CXCR5-overexpressing MSCs (MSCCXCR5) were generated that retained their abilities of proliferation, differentiation, and immunomodulation. Furthermore, MSCCXCR5 showed significantly increased migrating ability toward CXCL13. Importantly, systemic infusion of MSCCXCR5 dramatically suppressed CHS in mice, as evidenced by decreased levels of inflammatory cell infiltration and pro-inflammatory cytokine production. Numerous MSCCXCR5 migrated into inflamed ears, localized with T cells, inhibited T cell proliferation, promoted T cell apoptosis, and suppressed the production of T cell-derived pro-inflammatory factors. Collectively, these findings demonstrate that CXCR5 overexpression increases the ability of MSCs to respond to migratory stimuli and highly intensifies their immunomodulatory effects in vivo. This strategy for enhancing targeted stem/progenitor cell homing may improve the efficacy of MSC-based therapies.

The roles and regulation of the actin cytoskeleton, intermediate filaments and microtubules in smooth muscle cell migration

Smooth muscle cell migration has been implicated in the development of respiratory and cardiovascular systems; and airway/vascular remodeling. Cell migration is a polarized cellular process involving a protrusive cell front and a retracting trailing rear. There are three cytoskeletal systems in mammalian cells: the actin cytoskeleton, the intermediate filament network, and microtubules; all of which regulate all or part of the migrated process. The dynamic actin cytoskeleton spatially and temporally regulates protrusion, adhesions, contraction, and retraction from the cell front to the rear. c-Abl tyrosine kinase plays a critical role in regulating actin dynamics and migration of airway smooth muscle cells and nonmuscle cells. Recent studies suggest that intermediate filaments undergo reorganization during migration, which coordinates focal adhesion dynamics, cell contraction, and nucleus rigidity. In particular, vimentin intermediate filaments undergo phosphorylation and reorientation in smooth muscle cells, which may regulate cell contraction and focal adhesion assembly/disassembly. Motile cells are characterized by a front-rear polarization of the microtubule framework, which regulates all essential processes leading to cell migration through its role in cell mechanics, intracellular trafficking, and signaling. This review recapitulates our current knowledge how the three cytoskeletal systems spatially and temporally modulate the migratory properties of cells. We also summarize the potential role of migration-associated biomolecules in lung and vascular diseases.

Human metapneumovirus Induces Reorganization of the Actin Cytoskeleton for Direct Cell-to-Cell Spread

Paramyxovirus spread generally involves assembly of individual viral particles which then infect target cells. We show that infection of human bronchial airway cells with human metapneumovirus (HMPV), a recently identified paramyxovirus which causes significant respiratory disease, results in formation of intercellular extensions and extensive networks of branched cell-associated filaments. Formation of these structures is dependent on actin, but not microtubule, polymerization. Interestingly, using a co-culture assay we show that conditions which block regular infection by HMPV particles, including addition of neutralizing antibodies or removal of cell surface heparan sulfate, did not prevent viral spread from infected to new target cells. In contrast, inhibition of actin polymerization or alterations to Rho GTPase signaling pathways significantly decreased cell-to-cell spread. Furthermore, viral proteins and viral RNA were detected in intercellular extensions, suggesting direct transfer of viral genetic material to new target cells. While roles for paramyxovirus matrix and fusion proteins in membrane deformation have been previously demonstrated, we show that the HMPV phosphoprotein extensively co-localized with actin and induced formation of cellular extensions when transiently expressed, supporting a new model in which a paramyxovirus phosphoprotein is a key player in assembly and spread. Our results reveal a novel mechanism for HMPV direct cell-to-cell spread and provide insights into dissemination of respiratory viruses.

Human metapneumovirus (HMPV) is an important human respiratory pathogen that affects all age groups worldwide. There are currently no vaccines or treatments available for HMPV, and key aspects of its life cycle remain unknown. We examined the late events of the HMPV infection cycle in human bronchial epithelial cells. Our data demonstrate that HMPV infection leads to formation of unique structures, including intercellular extensions connecting cells, and large networks of branched cell-associated filaments. Viral modulation of the cellular cytoskeleton and cellular signaling pathways are important for formation of these structures. Our results are consistent with the intercellular extensions playing a role in direct spread of virus from cell-to-cell, potentially by transfer of virus genetic material without particle formation. We also show that the HMPV phosphoprotein localizes with actin and can promote membrane deformations, suggesting a novel role in viral assembly or spread for paramyxovirus phosphoproteins.