Rho GTPases and signaling networks

Pathogenicity and virulence of Yersinia

The genus Yersinia includes human, animal, insect, and plant pathogens as well as many symbionts and harmless bacteria. Within this genus are Yersinia enterocolitica and the Yersinia pseudotuberculosis complex, with four human pathogenic species that are highly related at the genomic level including the causative agent of plague, Yersinia pestis. Extensive laboratory, field work, and clinical research have been conducted to understand the underlying pathogenesis and zoonotic transmission of these pathogens. There are presently more than 500 whole genome sequences from which an evolutionary footprint can be developed that details shared and unique virulence properties. Whereas the virulence of Y. pestis now seems in apparent homoeostasis within its flea transmission cycle, substantial evolutionary changes that affect transmission and disease severity continue to ndergo apparent selective pressure within the other Yersiniae that cause intestinal diseases. In this review, we will summarize the present understanding of the virulence and pathogenesis of Yersinia, highlighting shared mechanisms of virulence and the differences that determine the infection niche and disease severity.

The RhoGEF protein Plekhg5 self-associates via its PH domain to regulate apical cell constriction

RhoGEFs are critical activators of Rho family small GTPases and regulate diverse biological processes, such as cell division and tissue morphogenesis. We reported previously that the RhoGEF gene plekhg5 controls apical constriction of bottle cells at the blastopore lip during Xenopus gastrulation, but the detailed mechanism of plekhg5 action is not understood in depth. In this study, we show that localization of Plekhg5 in the apical cortex depends on its N-terminal sequences and intact guanine nucleotide exchange activity, whereas the C-terminal sequences prevent ectopic localization of the protein to the basolateral compartment. We also reveal that Plekhg5 self-associates via its PH domain, and this interaction leads to functional rescue of two mutants that lack the N-terminal region and the guanine nucleotide exchange factor activity, respectively, in trans. A point mutation in the PH domain corresponding to a variant associated with human disease leads to loss of self-association and failure of the mutant to induce apical constriction. Taken together, our results suggest that PH-mediated self-association and N-terminal domain-mediated subcellular localization are both crucial for the function of Plekhg5 in inducing apical constriction.

Adaptive Evolution and Functional Differentiation of Testis-Expressed Genes in Theria

Gene expression patterns differ in different tissues, and the expression pattern of genes in the mammalian testis is known to be extremely variable in different species. To clarify how the testis transcriptomic pattern has evolved in particular species, we examined the evolution of the adult testis transcriptome in Theria using 10 species: two marsupials (opossum and Tasmanian devil), six eutherian (placental) mammals (human, chimpanzee, bonobo, gorilla, rhesus macaque, and mouse), and two outgroup species (platypus and chicken). We show that 22 testis-expressed genes are marsupial-specific, suggesting their acquisition in the stem lineage of marsupials after the divergence from eutherians. Despite the time length of the eutherian stem lineage being similar to that of the marsupial lineage, acquisition of testis-expressed genes was not found in the stem lineage of eutherians; rather, their expression patterns differed by species, suggesting rapid gene evolution in the eutherian ancestors. Fifteen testis-expressed genes are therian-specific, and for three of these genes, the evolutionary tempo is markedly faster in eutherians than in marsupials. Our phylogenetic analysis of Rho GTPase-activating protein 28 (ARHGAP28) suggests the adaptive evolution of this gene in the eutherians, probably together with the expression pattern differentiation.

The Small G-Protein Rac1 in the Dorsomedial Striatum Promotes Alcohol-Dependent Structural Plasticity and Goal-Directed Learning in Mice

The small G-protein Ras-related C3 botulinum toxin substrate 1 (Rac1) promotes the formation of filamentous actin (F-actin). Actin is a major component of dendritic spines, and we previously found that alcohol alters actin composition and dendritic spine structure in the nucleus accumbens (NAc) and the dorsomedial striatum (DMS). To examine if Rac1 contributes to these alcohol-mediated adaptations, we measured the level of GTP-bound active Rac1 in the striatum of mice following 7 weeks of intermittent access to 20% alcohol. We found that chronic alcohol intake activates Rac1 in the DMS of male mice. In contrast, Rac1 is not activated by alcohol in the NAc and DLS of male mice or in the DMS of female mice. Similarly, closely related small G-proteins are not activated by alcohol in the DMS, and Rac1 activity is not increased in the DMS by moderate alcohol or natural reward. To determine the consequences of alcohol-dependent Rac1 activation in the DMS of male mice, we inhibited endogenous Rac1 by infecting the DMS of mice with an adeno-associated virus (AAV) expressing a dominant negative form of the small G-protein (Rac1-DN). We found that overexpression of AAV-Rac1-DN in the DMS inhibits alcohol-mediated Rac1 signaling and attenuates alcohol-mediated F-actin polymerization, which corresponded with a decrease in dendritic arborization and spine maturation. Finally, we provide evidence to suggest that Rac1 in the DMS plays a role in alcohol-associated goal-directed learning. Together, our data suggest that Rac1 in the DMS plays an important role in alcohol-dependent structural plasticity and aberrant learning.

The small G-protein Rac1 in the dorsomedial striatum promotes alcohol-dependent structural plasticity and goal-directed learning in mice

The small G-protein Rac1 promotes the formation of filamentous actin (F-Actin). Actin is a major component of dendritic spines, and we previously found that alcohol alters actin composition and dendritic spine structure in the nucleus accumbens (NAc) and the dorsomedial striatum (DMS). To examine if Rac1 contributes to these alcohol-mediated adaptations, we measured the level of GTP-bound active Rac1 in the striatum of mice following 7 weeks of intermittent access to 20% alcohol. We found that chronic alcohol intake activates Rac1 in the DMS of male mice. In contrast, Rac1 is not activated by alcohol in the NAc and DLS of male mice, or in the DMS of female mice. Similarly, closely related small G-proteins are not activated by alcohol in the DMS, and Rac1 activity is not increased in the DMS by moderate alcohol or natural reward. To determine the consequences of alcohol-dependent Rac1 activation in the DMS of male mice, we inhibited endogenous Rac1 by infecting the DMS of mice with an AAV expressing a dominant negative form of the small G-protein (Rac1-DN). We found that overexpression of AAV-Rac1-DN in the DMS inhibits alcohol-mediated Rac1 signaling and attenuates alcohol-mediated F-actin polymerization, which corresponded with a decrease in dendritic arborization and spine maturation. Finally, we provide evidence to suggest that Rac1 in the DMS plays a role in alcohol-associated goal-directed learning. Together, our data suggest that Rac1 in the DMS plays an important role in alcohol-dependent structural plasticity and aberrant learning.

Significance Statement

Addiction, including alcohol use disorder, is characterized by molecular and cellular adaptations that promote maladaptive behaviors. We found that Rac1 was activated by alcohol in the dorsomedial striatum (DMS) of male mice. We show that alcohol-mediated Rac1 signaling is responsible for alterations in actin dynamics and neuronal morphology. We also present data to suggest that Rac1 is important for alcohol-associated learning processes. These results suggest that Rac1 in the DMS is an important contributor to adaptations that promote alcohol use disorder.

Methylated dialkylphosphate metabolites of the organophosphate pesticide malathion modify actin cytoskeleton arrangement and cell migration via activation of Rho GTPases Rac1 and Cdc42

The non-cholinergic molecular targets of organophosphate (OP) compounds have recently been investigated to explain their role in the generation of non-neurological diseases, such as immunotoxicity and cancer. Here, we evaluated the effects of malathion and its dialkylphosphate (DAP) metabolites on the cytoskeleton components and organization of RAW264.7 murine macrophages as non-cholinergic targets of OP and DAPs toxicity. All OP compounds affected actin and tubulin polymerization. Malathion, dimethyldithiophosphate (DMDTP) dimethylthiophosphate (DMTP), and dimethylphosphate (DMP) induced elongated morphologies and the formation of pseudopods rich in microtubule structures, and increased filopodia formation and general actin disorganization in RAW264.7 cells and slightly reduced stress fibers in the human fibroblasts GM03440, without significantly disrupting the tubulin or vimentin cytoskeleton. Exposure to DMTP and DMP increased cell migration in the wound healing assay but did not affect phagocytosis, indicating a very specific modification in the organization of the cytoskeleton. The induction of actin cytoskeleton rearrangement and cell migration suggested the activation of cytoskeletal regulators such as small GTPases. We found that DMP slightly reduced Ras homolog family member A activity but increased the activities of Ras-related C3 botulinum toxin substrate 1 (Rac1) and cell division control protein 42 (Cdc42) from 5 min to 2 h of exposure. Chemical inhibition of Rac1 with NSC23766 reduced cell polarization and treatment with DMP enhanced cell migration, but Cdc42 inhibition by ML-141 completely inhibited the effects of DMP. These results suggest that methylated OP compounds, especially DMP, can modify macrophage cytoskeleton function and configuration via activation of Cdc42, which may represent a potential non-cholinergic molecular target for OP compounds.

The Evaluation of Rac1 Signaling as a Potential Therapeutic Target of Alzheimer's Disease

The Small GTPase Rac1 is critical for various fundamental cellular processes, including cognitive functions. The cyclical activation and inactivation of Rac1, mediated by Rac guanine nucleotide exchange factors (RacGEFs) and Rac GTPase-activating proteins (RacGAPs), respectively, are essential for activating intracellular signaling pathways and controlling cellular processes. We have recently shown that the Alzheimer's disease (AD) therapeutic drug donepezil activates the Rac1-PAK pathway in the nucleus accumbens (NAc) for enhanced aversive learning. Also, PAK activation itself in the NAc enhances aversive learning. As aversive learning allows short-term preliminary AD drug screening, here we tested whether sustained Rac1 activation by RacGAP inhibition can be used as an AD therapeutic strategy for improving AD-learning deficits based on aversive learning. We found that the RacGAP domain of breakpoint cluster region protein (Bcr) (Bcr-GAP) efficiently inhibited Rac1 activity in a membrane ruffling assay. We also found that, in striatal/accumbal primary neurons, Bcr knockdown by microRNA mimic-expressing adeno-associated virus (AAV-miRNA mimic) activated Rac1-PAK signaling, while Bcr-GAP-expressing AAV inactivated it. Furthermore, conditional knockdown of Bcr in the NAc of wild-type adult mice enhanced aversive learning, while Bcr-GAP expression in the NAc inhibited it. The findings indicate that Rac1 activation by RacGAP inhibition enhances aversive learning, implying the AD therapeutic potential of Rac1 signaling.

Boosting mitochondrial function and metabolism in aging female germ cells with dual ROCK/ROS inhibition

The decline in oocyte quality with age is an irreversible process that results in low fertility. Reproductive aging causes an increase in oocyte aneuploidy leading to a decrease in embryo quality and an increase in the incidence of miscarriage and congenital defects. Here, we show that the dysfunction associated with aging is not limited to the oocyte, as oocyte granulosa cells also show a range of defects related to mitochondrial activity. The addition of Y-27632 and Vitamin C combination drugs to aging germ cells was effective in enhancing the quality of aging cells. We observed that supplement treatment significantly decreased the production of reactive oxygen species (ROS) and restored the balance of mitochondrial membrane potential. Supplementation treatment reduces excessive mitochondrial fragmentation in aging cells by upregulating mitochondrial fusion. Moreover, it regulated the energy metabolism within cells, favoring oxygen respiration and reducing anaerobic respiration, thereby increasing cellular ATP production. In an experiment with aged mice, supplement treatment improved the maturation of oocytes in vitro and prevented the buildup of ROS in aging oocytes in culture. Additionally, this treatment resulted in an increased concentration of anti-mullerian hormone (AMH) in the culture medium. By improving mitochondrial metabolism in aging females, supplement treatment has the potential to increase quality of oocytes during in vitro fertilization.

Rac1 and Rac3 GTPases and TPC2 are required for axonal outgrowth and migration of cortical interneurons

Rho GTPases, among them Rac1 and Rac3, are major transducers of extracellular signals and are involved in multiple cellular processes. In cortical interneurons, the neurons that control the balance between excitation and inhibition of cortical circuits, Rac1 and Rac3 are essential for their development. Ablation of both leads to a severe reduction in the numbers of mature interneurons found in the murine cortex, which is partially due to abnormal cell cycle progression of interneuron precursors and defective formation of growth cones in young neurons. Here, we present new evidence that upon Rac1 and Rac3 ablation, centrosome, Golgi complex and lysosome positioning is significantly perturbed, thus affecting both interneuron migration and axon growth. Moreover, for the first time, we provide evidence of altered expression and localization of the two-pore channel 2 (TPC2) voltage-gated ion channel that mediates Ca2+ release. Pharmacological inhibition of TPC2 negatively affected axonal growth and migration of interneurons. Our data, taken together, suggest that TPC2 contributes to the severe phenotype in axon growth initiation, extension and interneuron migration in the absence of Rac1 and Rac3.

Identification of a small RhoA GTPase inhibitor effective in fission yeast and human cells

The Rho GTPase family proteins are key regulators of cytoskeletal dynamics. Deregulated activity of Rho GTPases is associated with cancers and neurodegenerative diseases, and their potential as drug targets has long been recognized. Using an economically effective drug screening workflow in fission yeast and human cells, we have identified a Rho GTPase inhibitor, O1. By a suppressor mutant screen in fission yeast, we find a point mutation in the rho1 gene that confers resistance to O1. Consistent with the idea that O1 is the direct inhibitor of Rho1, O1 reduced the cellular amount of activated, GTP-bound Rho1 in wild-type cells, but not in the O1-resistant mutant cells, in which the evolutionarily conserved Ala62 residue is mutated to Thr. Similarly, O1 inhibits activity of the human orthologue RhoA GTPase in tissue culture cells. Our studies illustrate the power of yeast phenotypic screens in the identification and characterization of drugs relevant to human cells and have identified a novel GTPase inhibitor for fission yeast and human cells.

Cholesterol metabolism pathway in autism spectrum disorder: From animal models to clinical observations

Autism Spectrum Disorder (ASD) is a neurodevelopmental disorder characterized by a persistent impairment of social skills, including aspects of perception, interpretation, and response, combined with restricted and repetitive behavior. ASD is a complex and multifactorial condition, and its etiology could be attributed to genetic and environmental factors. Despite numerous clinical and experimental studies, no etiological factor, biomarker, and specific model of transmission have been consistently associated with ASD. However, an imbalance in cholesterol levels has been observed in many patients, more specifically, a condition of hypocholesterolemia, which seems to be shared between ASD and ASD-related genetic syndromes such as fragile X syndrome (FXS), Rett syndrome (RS), and Smith- Lemli-Opitz (SLO). Furthermore, it is known that alterations in cholesterol levels lead to neuroinflammation, oxidative stress, impaired myelination and synaptogenesis. Thus, the aim of this review is to discuss the cholesterol metabolic pathways in the ASD context, as well as in genetic syndromes related to ASD, through clinical observations and animal models. In fact, SLO, FXS, and RS patients display early behavioral markers of ASD followed by cholesterol disturbances. Several studies have demonstrated the role of cholesterol in psychiatric conditions and how its levels modulate brain neurodevelopment. This review suggests an important relationship between ASD pathology and cholesterol metabolism impairment; thus, some strategies could be raised - at clinical and pre-clinical levels - to explore whether cholesterol metabolism disturbance has a generally adverse effect in exacerbating the symptoms of ASD patients.

Rho GTPase Signaling in Platelet Regulation and Implication for Antiplatelet Therapies

Platelets play a vital role in regulating hemostasis and thrombosis. Rho GTPases are well known as molecular switches that control various cellular functions via a balanced GTP-binding/GTP-hydrolysis cycle and signaling cascade through downstream effectors. In platelets, Rho GTPases function as critical regulators by mediating signal transduction that drives platelet activation and aggregation. Mostly by gene targeting and pharmacological inhibition approaches, Rho GTPase family members RhoA, Rac1, and Cdc42 have been shown to be indispensable in regulating the actin cytoskeleton dynamics in platelets, affecting platelet shape change, spreading, secretion, and aggregation, leading to thrombus formation. Additionally, studies of Rho GTPase function using platelets as a non-transformed model due to their anucleated nature have revealed valuable information on cell signaling principles. This review provides an updated summary of recent advances in Rho GTPase signaling in platelet regulation. We also highlight pharmacological approaches that effectively inhibited platelet activation to explore their possible development into future antiplatelet therapies.

Pattern recognition receptor mediated innate immune response requires a Rif-dependent pathway

Small GTPases play critical roles in cell morphology, movement, and adhesion by dynamic regulation of actin cytoskeleton. The small Rho GTPase Rif/RhoF (Rho in filopodia) regulates the formation of filopodia and stress fibers in cells. Rif is highly expressed in a number of cell types in the immune system; however, it's role in immune system function is unclear. In this research, we found that Rif expression is necessary for NF-κB activation in primary immune cells, and mature dendritic cell (mature DCs) induced from Bone Marrow-Derived Dendritic Cells (BMDCs) isolated from Rif knock out (Rif KO) mice displayed impaired degradation of I-κBα, as well as reduced TNF-α secretion and p38 MAPK phosphorylation under LPS stimulation. Interestingly, we revealed that TLR agonists, such as LPS and poly (I:C), as well as bacterial virulence factor SopE could induce a transient increase in Rif activation in monocytes THP-1 cells. Furthermore, Rif was found to be an integral part of the TLR4, TLR3 and nodosome signaling complex. We further identified Src tyrosine kinases as upstream activator of Rif in both bacterial and viral induced immune responses. Moreover, activated Rif induces activation of transcription factors, such as NF-κB, AP-1 and IRF-3, and mediates inflammation through secretion of IL-6, IL-8 or TNFα. Rif activation by PRRs contributes in a variety of ways to protective host responses against invading microbes. Taken together, this study reveals that Rif is indispensable for both extracellular and intracellular pattern-recognition receptor-mediated innate immune responses. Rif possess broad anti-pathogenic effect and understanding of the molecular mechanisms by which this small Rho GTPase interferes with innate immune system will be beneficial to develop therapies against infectious agents.

Transcriptome profiling of male and female Ascaris lumbricoides reproductive tissues

BACKGROUND

Ascaris lumbricoides causes human ascariasis, the most prevalent helminth disease, infecting approximately 1 billion individuals globally. In 2019 the global disease burden was estimated to be 754,000 DALYs and resulted in 2090 deaths. In the absence of a vaccination strategy, treatment of ascariasis has relied on anthelminthic chemotherapy, but drug resistance is a concern. The propensity for reinfection is also a major challenge to disease control; female worms lay up to 200,000 eggs daily, which contaminate surrounding environments and remain viable for years, resulting in high transmission rates. Understanding the molecular mechanisms of reproductive processes, including control of egg production, spermatogenesis, oogenesis and embryogenesis, will drive the development of new drugs and/or vaccine targets for future ascariasis control.

METHODS

Transcriptome profiles of discrete reproductive and somatic tissue samples were generated from adult male and female worms using Illumina HiSeq with 2 × 150 bp paired-end sequencing. Male tissues included: testis germinal zone, testis part of vas deferens, seminal vesicle and somatic tissue. Female tissues included: ovary germinal zone, ovary part of the oviduct, uterus and somatic tissue. Differentially expressed genes (DEGs) were identified from the fragments per kilobases per million reads (FPKM) profiles. Hierarchical analysis was performed to identify tissue-specific genes. Furthermore, Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses were employed to identify significant terms and pathways for the DEGs.

RESULTS

DEGs involved in protein phosphorylation and adhesion molecules were indicated to play a crucial role in spermatogenesis and fertilization, respectively. Those genes associated with the G-protein-coupled receptor (GPCR) signaling pathway and small GTPase-mediated signal transduction pathway play an essential role in cytoskeleton organization during oogenesis. Additionally, DEGs associated with the SMA genes and TGF-β signaling pathway are crucial in adult female embryogenesis. Some genes associated with particular biological processes and pathways that were identified in this study have been linked to defects in germline development, embryogenesis and reproductive behavior. In the enriched KEGG pathway analysis, Hippo signaling, oxytocin signaling and tight junction pathways were identified to play a role in Ascaris male and female reproductive systems.

CONCLUSIONS

This study has provided comprehensive transcriptome profiles of discrete A. lumbricoides reproductive tissue samples, revealing the molecular basis of these functionally important tissues. The data generated from this study will provide fundamental knowledge on the reproductive biology of Ascaris and will inform future target identification for anti-ascariasis drugs and/or vaccines.

Nectin4 is a potential therapeutic target for asthma

BACKGROUND

Nectins comprise a family of cellular adhesion molecules involved in Ca2+-independent cellular adhesion. Neither the biological significance nor clinical potential of Nectin4 for asthma has been investigated.

OBJECTIVES

The aims of this study were to elucidate the role of Nectin4 in airway inflammation and to determine the relationship between Nectin4 and clinical variables in patients with asthma.

METHODS

The relationship between Nectin4 levels in the blood of asthmatic patients and clinical variables was examined. Dermatophagoides pteronyssinus 1 (Der p1)-exposed normal human bronchial epithelial (NHBE) cells, and Nectin4-deficient (Nectin4-/-) and wild-type (WT) mice sensitized/challenged with ovalbumin (OVA), were used to investigate the involvement of Nectin4 in the pathogenesis of bronchial asthma via the Src/Rac1 pathway.

RESULTS

Plasma Nectin4 levels were significantly higher in asthmatic patients than controls and correlated with specific IgE D1, D2, lung function. The ROC curves for Nectin4 levels differed between asthma patients and controls. Nectin4/Afadin and Src/Rac1 levels were significantly increased in NHBE cells exposed to Der p1, but decreased in NHBE cells treated with Nectin4 siRNA. Airway obstruction and inflammation, as well as the levels of Th2 cytokines, Nectin4, and Src/Rac1, were increased in WT OVA/OVA mice compared with WT sham mice. Nectin4 knockdown resulted in lower levels of Afadin and Src/Rac1 in Nectin4-/-OVA/OVA than WT OVA/OVA mice.

CONCLUSION

These results suggest that Nectin4 is involved in airway inflammation and may be a therapeutic target in patients with asthma.

CD16+ fibroblasts foster a trastuzumab-refractory microenvironment that is reversed by VAV2 inhibition

The leukocyte Fcγ receptor (FcγR)-mediated response is important for the efficacy of therapeutic antibodies; however, little is known about the role of FcγRs in other cell types. Here we identify a subset of fibroblasts in human breast cancer that express CD16 (FcγRIII). An abundance of these cells in HER2⁺ breast cancer patients is associated with poor prognosis and response to trastuzumab. Functionally, upon trastuzumab stimulation, CD16⁺ fibroblasts reduce drug delivery by enhancing extracellular matrix stiffness. Interaction between trastuzumab and CD16 activates the intracellular SYK-VAV2-RhoA-ROCK-MLC2-MRTF-A pathway, leading to elevated contractile force and matrix production. Targeting of a Rho family guanine nucleotide exchange factor, VAV2, which is indispensable for the function of CD16 in fibroblasts rather than leukocytes, reverses desmoplasia provoked by CD16⁺ fibroblasts. Collectively, our study reveals a role for the fibroblast FcγR in drug resistance, and suggests that VAV2 is an attractive target to augment the effects of antibody treatments.

Regulation of Cdc42 protein turnover modulates the filamentous growth MAPK pathway

Rho GTPases are central regulators of cell polarity and signaling. How Rho GTPases are directed to function in certain settings remains unclear. Here, we show the protein levels of the yeast Rho GTPase Cdc42p are regulated, which impacts a subset of its biological functions. Specifically, the active conformation of Cdc42p was ubiquitinated by the NEDD4 ubiquitin ligase Rsp5p and HSP40/HSP70 chaperones and turned over in the proteasome. A GTP-locked (Q61L) turnover-defective (TD) version, Cdc42pQ61L+TD, hyperactivated the MAPK pathway that regulates filamentous growth (fMAPK). Cdc42pQ61L+TD did not influence the activity of the mating pathway, which shares components with the fMAPK pathway. The fMAPK pathway adaptor, Bem4p, stabilized Cdc42p levels, which resulted in elevated fMAPK pathway signaling. Our results identify Cdc42p turnover regulation as being critical for the regulation of a MAPK pathway. The control of Rho GTPase levels by stabilization and turnover may be a general feature of signaling pathway regulation, which can result in the execution of a specific developmental program.

RHO GTPase family in hepatocellular carcinoma

RHO GTPases are a subfamily of the RAS superfamily of proteins, which are highly conserved in eukaryotic species and have important biological functions, including actin cytoskeleton reorganization, cell proliferation, cell polarity, and vesicular transport. Recent studies indicate that RHO GTPases participate in the proliferation, migration, invasion and metastasis of cancer, playing an essential role in the tumorigenesis and progression of hepatocellular carcinoma (HCC). This review first introduces the classification, structure, regulators and functions of RHO GTPases, then dissects its role in HCC, especially in migration and metastasis. Finally, we summarize inhibitors targeting RHO GTPases and highlight the issues that should be addressed to improve the potency of these inhibitors.

Cell contractility and focal adhesion kinase control circumferential arterial stiffness

Arterial stiffening is a hallmark of aging and cardiovascular disease. While it is well established that vascular smooth muscle cells (SMCs) contribute to arterial stiffness by synthesizing and remodeling the arterial extracellular matrix, the direct contributions of SMC contractility and mechanosensors to arterial stiffness, and particularly the arterial response to pressure, remain less well understood despite being a long-standing question of biomedical importance. Here, we have examined this issue by combining the use of pressure myography of intact carotid arteries, pharmacologic inhibition of contractility, and genetic deletion of SMC focal adhesion kinase (FAK). Biaxial inflation-extension tests performed at physiological pressures showed that acute inhibition of cell contractility with blebbistatin or EGTA altered vessel geometry and preferentially reduced circumferential, as opposed to axial, arterial stiffness in wild-type mice. Similarly, genetic deletion of SMC FAK, which attenuated arterial contraction to KCl, reduced vessel wall thickness and circumferential arterial stiffness in response to pressure while having minimal effect on axial mechanics. Moreover, these effects of FAK deletion were lost by treating arteries with blebbistatin or by inhibiting myosin light-chain kinase. The expression of arterial fibrillar collagens, the integrity of arterial elastin, or markers of SMC differentiation were not affected by the deletion of SMC FAK. Our results connect cell contractility and SMC FAK to the regulation of arterial wall thickness and directionally specific arterial stiffening.

Transcriptomic Dynamics of Active and Inactive States of Rho GTPase MoRho3 in Magnaporthe oryzae

The small Rho GTPase acts as a molecular switch in eukaryotic signal transduction, which plays a critical role in polar cell growth and vesicle trafficking. Previous studies demonstrated that constitutively active (CA) mutant strains, of MoRho3-CA were defective in appressorium formation. While dominant-negative (DN) mutant strains MoRho3-DN shows defects in polar growth. However, the molecular dynamics of MoRho3-mediated regulatory networks in the pathogenesis of Magnaporthe oryzae still needs to be uncovered. Here, we perform comparative transcriptomic profiling of MoRho3-CA and MoRho3-DN mutant strains using a high-throughput RNA sequencing approach. We find that genetic manipulation of MoRho3 significantly disrupts the expression of 28 homologs of Saccharomyces cerevisiae Rho3-interacting proteins, including EXO70, BNI1, and BNI2 in the MoRho3 CA, DN mutant strains. Functional enrichment analyses of up-regulated DEGs reveal a significant enrichment of genes associated with ribosome biogenesis in the MoRho3-CA mutant strain. Down-regulated DEGs in the MoRho3-CA mutant strains shows significant enrichment in starch/sucrose metabolism and the ABC transporter pathway. Moreover, analyses of down-regulated DEGs in the in MoRho3-DN reveals an over-representation of genes enriched in metabolic pathways. In addition, we observe a significant suppression in the expression levels of secreted proteins suppressed in both MoRho3-CA and DN mutant strains. Together, our results uncover expression dynamics mediated by two states of the small GTPase MoRho3, demonstrating its crucial roles in regulating the expression of ribosome biogenesis and secreted proteins.

Microenvironmental sensing by fibroblasts controls macrophage population size

Animal tissues comprise diverse cell types. However, the mechanisms controlling the number of each cell type within tissue compartments remain poorly understood. Here, we report that different cell types utilize distinct strategies to control population numbers. Proliferation of fibroblasts, stromal cells important for tissue integrity, is limited by space availability. In contrast, proliferation of macrophages, innate immune cells involved in defense, repair, and homeostasis, is constrained by growth factor availability. Examination of density-dependent gene expression in fibroblasts revealed that Hippo and TGF-β target genes are both regulated by cell density. We found YAP1, the transcriptional coactivator of the Hippo signaling pathway, directly regulates expression of Csf1, the lineage-specific growth factor for macrophages, through an enhancer of Csf1 that is specifically active in fibroblasts. Activation of YAP1 in fibroblasts elevates Csf1 expression and is sufficient to increase the number of macrophages at steady state. Our data also suggest that expression programs in fibroblasts that change with density may result from sensing of mechanical force through actin-dependent mechanisms. Altogether, we demonstrate that two different modes of population control are connected and coordinated to regulate cell numbers of distinct cell types. Sensing of the tissue environment may serve as a general strategy to control tissue composition.

Wound Healing from an Actin Cytoskeletal Perspective

Wound healing requires a complex cascade of highly controlled and conserved cellular and molecular processes. These involve numerous cell types and extracellular matrix molecules regulated by the actin cytoskeleton. This microscopic network of filaments is present within the cytoplasm of all cells and provides the shape and mechanical support required for cell movement and proliferation. Here, an overview of the processes of wound healing are described from the perspective of the cell in relation to the actin cytoskeleton. Key points of discussion include the role of actin, its binding proteins, signaling pathways, and events that play significant roles in the phases of wound healing. The identification of cytoskeletal targets that can be used to manipulate and improve wound healing is included as an emerging area of focus that may inform future therapeutic approaches to improve healing of complex wounds.

Recreational physical activity before and during pregnancy and placental DNA methylation-an epigenome-wide association study

BACKGROUND

Physical activity (PA) prior to and during pregnancy may have intergenerational effects on offspring health through placental epigenetic modifications. We are unaware of epidemiologic studies on longitudinal PA and placental DNA methylation.

OBJECTIVES

We evaluated the association between PA before and during pregnancy and placental DNA methylation.

METHODS

Placental tissues were obtained at delivery and methylation was measured using HumanMethylation450 Beadchips for participants in the Eunice Kennedy Shriver National Institute of Child Health and Human Development Fetal Growth Studies-Singletons among 298 participants. Using the Pregnancy Physical Activity Questionnaire, women recalled periconception PA (past 12 mo) at 8-13 wk of gestation and PA since last visit at 4 follow-up visits at 16-22, 24-29, 30-33, and 34-37 wk. We conducted linear regression for associations of PA at each visit with methylation controlling for false discovery rate (FDR). Top 100 CpGs were queried for enrichment of functional pathways using Ingenuity Pathway Analysis.

RESULTS

Periconception PA was significantly associated with 1 CpG site. PA since last visit for visits 1-4 was associated with 2, 2, 8, and 0 CpGs (log fold changes ranging from -0.0319 to 0.0080, after controlling for FDR). The largest change in methylation occurred at a site in TIMP2 , which is known to encode a protein critical for vasodilation, placentation, and uterine expansion during pregnancy (log fold change: -0.05; 95% CI: -0.06, -0.03 per metabolic equivalent of task-h/wk at 30-33 wk). Most significantly enriched pathways include cardiac hypertrophy signaling, B-cell receptor signaling, and netrin signaling. Significant CpGs and enriched pathways varied by visit.

CONCLUSIONS

Recreational PA in the year prior and during pregnancy was associated with placental DNA methylation. The associated CpG sites varied based on timing of PA. If replicated, the findings may inform the mechanisms underlying the impacts of PA on placenta health. This study was registered at clinicaltrials.gov as NCT00912132.

Implication of Lipids in Calcified Aortic Valve Pathogenesis: Why Did Statins Fail?

Calcific Aortic Valve Disease (CAVD) is a fibrocalcific disease. Lipoproteins and oxidized phospholipids play a substantial role in CAVD; the level of Lp(a) has been shown to accelerate the progression of valve calcification. Indeed, oxidized phospholipids carried by Lp(a) into the aortic valve stimulate endothelial dysfunction and promote inflammation. Inflammation and growth factors actively promote the synthesis of the extracellular matrix (ECM) and trigger an osteogenic program. The accumulation of ECM proteins promotes lipid adhesion to valve tissue, which could initiate the osteogenic program in interstitial valve cells. Statin treatment has been shown to have the ability to diminish the death rate in subjects with atherosclerotic impediments by decreasing the serum LDL cholesterol levels. However, the use of HMG-CoA inhibitors (statins) as cholesterol-lowering therapy did not significantly reduce the progression or the severity of aortic valve calcification. However, new clinical trials targeting Lp(a) or PCSK9 are showing promising results in reducing the severity of aortic stenosis. In this review, we discuss the implication of lipids in aortic valve calcification and the current findings on the effect of lipid-lowering therapy in aortic stenosis.

Talin‑1 interaction network in cellular mechanotransduction (Review)

The mechanical signals within the extracellular matrix (ECM) regulate cell growth, proliferation and differentiation, and integrins function as the hub between the ECM and cellular actin. Focal adhesions (FAs) are multi‑protein, integrin‑containing complexes, acting as tension‑sensing anchoring points that bond cells to the extracellular microenvironment. Talin‑1 serves as the central protein of FAs that participates in the activation of integrins and connects them with the actin cytoskeleton. As a cytoplasmic protein, Talin‑1 consists of a globular head domain and a long rod comprised of a series of α‑helical bundles. The unique structure of the Talin‑1 rod domain permits folding and unfolding in response to the mechanical stress, revealing various binding sites. Thus, conformation changes of the Talin‑1 rod domain enable the cell to convert mechanical signals into chemical through multiple signaling pathways. The present review discusses the binding partners of Talin‑1, their interactions, effects on the cellular processes, and their possible roles in diseases.

Septins guide noncentrosomal microtubules to promote focal adhesion disassembly in migrating cells

Endothelial cell migration is critical for vascular angiogenesis and is compromised to facilitate tumor metastasis. The migratory process requires the coordinated assembly and disassembly of focal adhesions (FA), actin, and microtubules (MT). MT dynamics at FAs deliver vesicular cargoes and enhance actomyosin contractility to promote FA turnover and facilitate cell advance. Noncentrosomal (NC) MTs regulate FA dynamics and are sufficient to drive cell polarity, but how NC MTs target FAs to control FA turnover is not understood. Here, we show that Rac1 induces the assembly of FA-proximal septin filaments that promote NC MT growth into FAs and inhibit mitotic centromere-associated kinesin (MCAK)-associated MT disassembly, thereby maintaining intact MT plus ends proximal to FAs. Septin-associated MT rescue is coupled with accumulation of Aurora-A kinase and cytoplasmic linker-associated protein (CLASP) localization to the MT between septin and FAs. In this way, NC MTs are strategically positioned to undergo MCAK- and CLASP-regulated bouts of assembly and disassembly into FAs, thereby regulating FA turnover and cell migration.

PI Kinase-EhGEF2-EhRho5 axis contributes to LPA stimulated macropinocytosis in Entamoeba histolytica

Entamoeba histolytica is a protozoan responsible for several pathologies in humans. Trophozoites breach the intestinal site to enter the bloodstream and thus traverse to a secondary site. Macropinocytosis and phagocytosis, collectively accounting for heterophagy, are the two major processes responsible for sustenance of Entamoeba histolytica within the host. Both of these processes require significant rearrangements in the structure to entrap the target. Rho GTPases play an indispensable role in mustering proteins that regulate cytoskeletal remodelling. Unlike phagocytosis which has been studied in extensive detail, information on machinery of macropinocytosis in E. histolytica is still limited. In the current study, using site directed mutagenesis and RNAi based silencing, coupled with functional studies, we have demonstrated the involvement of EhRho5 in constitutive and LPA stimulated macropinocytosis. We also report that LPA, a bioactive phospholipid present in the bloodstream of the host, activates EhRho5 and translocates it from cytosol to plasma membrane and endomembrane compartments. Using biochemical and FRAP studies, we established that a PI Kinase acts upstream of EhRho5 in LPA mediated signalling. We further identified EhGEF2 as a guanine nucleotide exchange factor of EhRho5. In the amoebic trophozoites, EhGEF2 depletion leads to reduced macropinocytic efficiency of trophozoites, thus phenocopying its substrate. Upon LPA stimulation, EhGEF2 is found to sequester near the plasma membrane in a wortmannin sensitive fashion, explaining a possible mode for activation of EhRho5 in the amoebic trophozoites. Collectively, we propose that LPA stimulated macropinocytosis in E. histolytica is driven by the PI Kinase-EhGEF2-EhRho5 axis.

The Small GTPase RHOA Links SLP65 Activation to PTEN Function in Pre B Cells and Is Essential for the Generation and Survival of Normal and Malignant B Cells

The generation, differentiation, survival and activation of B cells are coordinated by signals emerging from the B cell antigen receptor (BCR) or its precursor, the pre-BCR. The adaptor protein SLP65 (also known as BLNK) is an important signaling factor that controls pre-B cell differentiation by down-regulation of PI3K signaling. Here, we investigated the mechanism by which SLP65 interferes with PI3K signaling. We found that SLP65 induces the activity of the small GTPase RHOA, which activates PTEN, a negative regulator of PI3K signaling, by enabling its translocation to the plasma membrane. The essential role of RHOA is confirmed by the complete block in early B cell development in conditional RhoA-deficient mice. The RhoA-deficient progenitor B cells showed defects in activation of immunoglobulin gene rearrangement and fail to survive both in vitro and in vivo. Reconstituting the RhoA-deficient cells with RhoA or Foxo1, a transcription factor repressed by PI3K signaling and activated by PTEN, completely restores the survival defect. However, the defect in differentiation can only be restored by RhoA suggesting a unique role for RHOA in B cell generation and selection. In full agreement, conditional RhoA-deficient mice develop increased amounts of autoreactive antibodies with age. RHOA function is also required at later stage, as inactivation of RhoA in peripheral B cells or in a transformed mature B cell line resulted in cell loss. Together, these data show that RHOA is the key signaling factor for B cell development and function by providing a crucial SLP65-activated link between BCR signaling and activation of PTEN. Moreover, the identified essential role of RHOA for the survival of transformed B cells offers the opportunity for targeting B cell malignancies by blocking RHOA function.

The Immunomodulatory Effects of Statins on Macrophages

Statins are 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors used worldwide to manage dyslipidaemia and thus limit the development of atherosclerotic disease and its complications. These atheroprotective drugs are now known to exert pleiotropic actions outside of their cholesterol-lowering activity, including altering immune cell function. Macrophages are phagocytic leukocytes that play critical functional roles in the pathogenesis of atherosclerosis and are directly targeted by statins. Early studies documented the anti-inflammatory effects of statins on macrophages, but emerging evidence suggests that these drugs can also enhance pro-inflammatory macrophage responses, creating an unresolved paradox. This review comprehensively examines the in vitro, in vivo, and clinical literature to document the statin-induced changes in macrophage polarization and immunomodulatory functions, explore the underlying mechanisms involved, and offer potential explanations for this paradox. A better understanding of the immunomodulatory actions of statins on macrophages should pave the way for the development of novel therapeutic approaches to manage atherosclerosis and other chronic diseases and conditions characterised by unresolved inflammation.

Associations of statin use with the onset and progression of open-angle glaucoma: A systematic review and meta-analysis

Background

Statins, the first-line therapy for hyperlipidemia, have received considerable attention as candidates for glaucoma treatments given its neuroprotective effects. In this systematic review and meta-analysis, we intended to assess the association of statin use with the onset and progression of open-angle glaucoma (OAG).

Methods

Databases including PubMed, Embase and Web of Science Core Collection were searched for longitudinal studies reporting the association between statin use and OAG onset or progression on Feb 3, 2021. A meta-analysis was performed for the association between statin use and OAG onset. Relative risks (RRs) with 95% confidential intervals (CIs) were retrieved from included studies and pooled using random-effects models. Potential risks of bias were evaluated by the Newcastle-Ottawa Quality Assessment Scale for all eligible studies. This study had been registered on PROSPERO (CRD 42021232172).

Findings

515,788 participants (mean age 68.7 years, 62.3% female) from ten studies were included in the systematic review of the association between statin use and OAG onset, and 26,347 OAG patients (mean age 67.3 years, 52.2% female) from seven studies were included for the association between statin use and OAG progression. Potential risks of bias were detected in 12 studies, which were mainly attributed to selection and confounding bias. In addition, 515,600 participants from eight studies were included in the meta-analysis which collectively showed that statin use was associated with a reduced risk of OAG onset (Pooled RR: 0.95; 95%CI: 0.93-0.98; I2=0.199;). No significant heterogeneity or publication bias was found for studies included in the meta-analysis. There were inconsistent evidences for the association between statin use and OAG progression.

Interpretation

Statin use is associated with a slightly lower risk of OAG onset based on existing evidences from longitudinal observational studies, the association between statin use and OAG progression remains inconclusive. The included evidences were typically weak due to poor study design and under-powered studies. Current findings should be interpreted cautiously and still need to be validated in further research.

Funding

The National Key R&D Program of China (2018YFC0116500), Science and Technology Planning Project of Guangdong Province (2013B20400003), the China Postdoctoral Science Foundation (2019TQ0365), the National Natural Science Foundation of China (82000901 and 82101171).

The Relationship between Cadherin Polymorphisms and the Risk of Delayed Encephalopathy after Acute Carbon Monoxide Poisoning in the Chinese Han Population

Objective

The purpose of this study was to analyze the relationship between cadherin gene single-nucleotide polymorphisms (SNPs) and the risk of delayed encephalopathy after acute carbon monoxide poisoning (DEACMP).

Materials and Methods

A total of 416 patients with DEACMP and 754 patients with acute carbon monoxide poisoning (ACMP) were recruited. We used the Sequenom MassARRAY® system to detect cadherin gene SNPs related to DEACMP. Using different genetic analysis models, we evaluated the relationship between the cadherin gene polymorphisms and risk of DEACMP.

Results

We found that rs1944294 in the N-cadherin (CDH2) gene showed significant differences in genotype frequencies between the two groups under codominant and dominant inheritance models. Similarly, rs2513796 in the cadherin-17 (CDH17) gene showed significant differences under the codominant, dominant, and overdominant genetic models. And the T allele frequency of rs1944294 in the DEACMP group was significantly higher than that in the ACMP group (P = 0.023).

Conclusions

Cadherin gene SNPs (rs1944294, rs2513796) are associated with an increased risk of DEACMP in the Chinese population.

Nutraceuticals and mitochondrial oxidative stress: bridging the gap in the management of bronchial asthma

Asthma is a chronic inflammatory disease primarily characterized by inflammation and reversible bronchoconstriction. It is currently one of the leading causes of morbidity and mortality in the world. Oxidative stress further complicates the pathology of the disease. The current treatment strategies for asthma mainly involve the use of anti-inflammatory agents and bronchodilators. However, long-term usage of such medications is associated with severe adverse effects and complications. Hence, there is an urgent need to develop newer, novel, and safe treatment modalities for the management of asthma. This has therefore prompted further investigations and detailed research to identify and develop novel therapeutic interventions from potent untapped resources. This review focuses on the significance of oxidative stressors that are primarily derived from both mitochondrial and non-mitochondrial sources in initiating the clinical features of asthma. The review also discusses the biological scavenging system of the body and factors that may lead to its malfunction which could result in altered states. Furthermore, the review provides a detailed insight into the therapeutic role of nutraceuticals as an effective strategy to attenuate the deleterious effects of oxidative stress and may be used in the mitigation of the cardinal features of bronchial asthma.

Insights into the post-translational modification and its emerging role in shaping the tumor microenvironment

More and more in-depth studies have revealed that the occurrence and development of tumors depend on gene mutation and tumor heterogeneity. The most important manifestation of tumor heterogeneity is the dynamic change of tumor microenvironment (TME) heterogeneity. This depends not only on the tumor cells themselves in the microenvironment where the infiltrating immune cells and matrix together forming an antitumor and/or pro-tumor network. TME has resulted in novel therapeutic interventions as a place beyond tumor beds. The malignant cancer cells, tumor infiltrate immune cells, angiogenic vascular cells, lymphatic endothelial cells, cancer-associated fibroblastic cells, and the released factors including intracellular metabolites, hormonal signals and inflammatory mediators all contribute actively to cancer progression. Protein post-translational modification (PTM) is often regarded as a degradative mechanism in protein destruction or turnover to maintain physiological homeostasis. Advances in quantitative transcriptomics, proteomics, and nuclease-based gene editing are now paving the global ways for exploring PTMs. In this review, we focus on recent developments in the PTM area and speculate on their importance as a critical functional readout for the regulation of TME. A wealth of information has been emerging to prove useful in the search for conventional therapies and the development of global therapeutic strategies.

Advances in the study of CDC42 in the female reproductive system

CDC42 is a member of the Rho‐GTPase family and is involved in a variety of cellular functions including regulation of cell cycle progression, constitution of the actin backbone and membrane transport. In particular, CDC42 plays a key role in the establishment of polarity in female vertebrate oocytes, and essential to this major regulatory role is its local occupation of specific regions of the cell to ensure that the contractile ring is assembled at the right time and place to ensure proper gametogenesis. The multifactor controlled ‘inactivation‐activation’ process of CDC42 also allows it to play an important role in the multilevel signalling network, and the synergistic regulation of multiple genes ensures maximum precision during gametogenesis. The purpose of this paper is to review the role of CDC42 in the control of gametogenesis and to explore its related mechanisms, with the aim of further understanding the great research potential of CDC42 in female vertebrate germ cells and its future clinical translation.

The Small GTPase CsRAC1 Is Important for Fungal Development and Pepper Anthracnose in Colletotrichum scovillei

The pepper anthracnose fungus, Colletotrichum scovillei, causes severe losses of pepper fruit production in the tropical and temperate zones. RAC1 is a highly conserved small GTP-binding protein in the Rho GTPase family. This protein has been demonstrated to play a role in fungal development, and pathogenicity in several plant pathogenic fungi. However, the functional roles of RAC1 are not characterized in C. scovillei causing anthracnose on pepper fruits. Here, we generated a deletion mutant (ΔCsrac1) via homologous recombination to investigate the functional roles of CsRAC1. The ΔCsrac1 showed pleiotropic defects in fungal growth and developments, including vegetative growth, conidiogenesis, conidial germination and appressorium formation, compared to wild-type. Although ΔCsrac1 was able to develop appressoria, it failed to differentiate appressorium pegs. However, ΔCsrac1 still caused anthracnose disease with significantly reduced rate on wounded pepper fruits. Further analyses revealed that ΔCsrac1 was defective in tolerance to oxidative stress and suppression of host-defense genes. Taken together, our results suggest that CsRAC1 plays essential roles in fungal development and pathogenicity in C. scovillei-pepper fruit pathosystem.

Histone deacetylase 8 interacts with the GTPase SmRho1 in Schistosoma mansoni

Background

Schistosoma mansoni histone deacetylase 8 (SmHDAC8) has elicited considerable interest as a target for drug discovery. Invalidation of its transcripts by RNAi leads to impaired survival of the worms in infected mice and its inhibition causes cell apoptosis and death. To determine why it is a promising therapeutic target the study of the currently unknown cellular signaling pathways involving this enzyme is essential. Protein partners of SmHDAC8 were previously identified by yeast two-hybrid (Y2H) cDNA library screening and by mass spectrometry (MS) analysis. Among these partners we characterized SmRho1, the schistosome orthologue of human RhoA GTPase, which is involved in the regulation of the cytoskeleton. In this work, we validated the interaction between SmHDAC8 and SmRho1 and explored the role of the lysine deacetylase in cytoskeletal regulation.

Methodology/principal findings

We characterized two isoforms of SmRho1, SmRho1.1 and SmRho1.2. Co- immunoprecipitation (Co-IP)/Mass Spectrometry (MS) analysis identified SmRho1 partner proteins and we used two heterologous expression systems (Y2H assay and Xenopus laevis oocytes) to study interactions between SmHDAC8 and SmRho1 isoforms.

To confirm SmHDAC8 and SmRho1 interaction in adult worms and schistosomula, we performed Co-IP experiments and additionally demonstrated SmRho1 acetylation using a Nano LC-MS/MS approach. A major impact of SmHDAC8 in cytoskeleton organization was documented by treating adult worms and schistosomula with a selective SmHDAC8 inhibitor or using RNAi followed by confocal microscopy.

Conclusions/significance

Our results suggest that SmHDAC8 is involved in cytoskeleton organization via its interaction with the SmRho1.1 isoform. The SmRho1.2 isoform failed to interact with SmHDAC8, but did specifically interact with SmDia suggesting the existence of two distinct signaling pathways regulating S. mansoni cytoskeleton organization via the two SmRho1 isoforms. A specific interaction between SmHDAC8 and the C-terminal moiety of SmRho1.1 was demonstrated, and we showed that SmRho1 is acetylated on K136. SmHDAC8 inhibition or knockdown using RNAi caused extensive disruption of schistosomula actin cytoskeleton.

Schistosoma mansoni is the major parasitic platyhelminth species causing intestinal schistosomiasis. Currently one drug, praziquantel, is the treatment of choice but its use in mass treatment programs means that the development of resistance is likely and renders imperative the development of new therapeutic agents. As new potential targets we have focused on lysine deacetylases, and in particular S. mansoni histone deacetylase 8 (SmHDAC8). Previous studies showed that reduction in the level of transcripts of SmHDAC8 by RNAi led to the impaired survival of the worms after the infection of mice. The analysis of the 3D structure of SmHDAC8 by X-ray crystallography showed that the catalytic domain structure diverges significantly from that of human HDAC8 and this was exploited to develop novel potential anti-schistosomal drugs. The biological roles of SmHDAC8 are unknown. For this reason, we previously characterized its protein binding partners and identified the schistosome orthologue of the human RhoA GTPase, suggesting the involvement of SmHDAC8 in the modulation of cytoskeleton organization. Here we investigated the interaction between SmHDAC8 and SmRho1 and identified two SmRho1 isoforms (SmRho1.1 and SmRho1.2). Our study showed that SmHDAC8 is involved in schistosome cytoskeleton organization.

Quinacrine-CASIN combination overcomes chemoresistance in human acute lymphoid leukemia

Chemoresistance posts a major hurdle for treatment of acute leukemia. There is increasing evidence that prolonged and intensive chemotherapy often fails to eradicate leukemic stem cells, which are protected by the bone marrow niche and can induce relapse. Thus, new therapeutic approaches to overcome chemoresistance are urgently needed. By conducting an ex vivo small molecule screen, here we have identified Quinacrine (QC) as a sensitizer for Cytarabine (AraC) in treating acute lymphoblastic leukemia (ALL). We show that QC enhances AraC-mediated killing of ALL cells, and subsequently abrogates AraC resistance both in vitro and in an ALL-xenograft model. However, while combo AraC+QC treatment prolongs the survival of primary transplanted recipients, the combination exhibits limited efficacy in secondary transplanted recipients, consistent with the survival of niche-protected leukemia stem cells. Introduction of Cdc42 Activity Specific Inhibitor, CASIN, enhances the eradication of ALL leukemia stem cells by AraC+QC and prolongs the survival of both primary and secondary transplanted recipients without affecting normal long-term human hematopoiesis. Together, our findings identify a small-molecule regimen that sensitizes AraC-mediated leukemia eradication and provide a potential therapeutic approach for better ALL treatment.

Broken detailed balance and entropy production in the human brain

To perform biological functions, living systems must break detailed balance by consuming energy and producing entropy. At microscopic scales, broken detailed balance enables a suite of molecular and cellular functions, including computations, kinetic proofreading, sensing, adaptation, and transportation. But do macroscopic violations of detailed balance enable higher-order biological functions, such as cognition and movement? To answer this question, we adapt tools from nonequilibrium statistical mechanics to quantify broken detailed balance in complex living systems. Analyzing neural recordings from hundreds of human subjects, we find that the brain violates detailed balance at large scales and that these violations increase with physical and cognitive exertion. Generally, we provide a flexible framework for investigating broken detailed balance at large scales in complex systems.

Living systems break detailed balance at small scales, consuming energy and producing entropy in the environment to perform molecular and cellular functions. However, it remains unclear how broken detailed balance manifests at macroscopic scales and how such dynamics support higher-order biological functions. Here we present a framework to quantify broken detailed balance by measuring entropy production in macroscopic systems. We apply our method to the human brain, an organ whose immense metabolic consumption drives a diverse range of cognitive functions. Using whole-brain imaging data, we demonstrate that the brain nearly obeys detailed balance when at rest, but strongly breaks detailed balance when performing physically and cognitively demanding tasks. Using a dynamic Ising model, we show that these large-scale violations of detailed balance can emerge from fine-scale asymmetries in the interactions between elements, a known feature of neural systems. Together, these results suggest that violations of detailed balance are vital for cognition and provide a general tool for quantifying entropy production in macroscopic systems.

Increased expression of Rho-associated protein kinase 2 confers astroglial Stat3 pathway activation during epileptogenesis

Patients with TLE are prone to tolerance to antiepileptic drugs. Based on the perspective of molecular targets for drug resistance, it is necessary to explore effective drug resistant genes and signaling pathways for the treatment of TLE. We performed gene expression profiles in hippocampus of patients with drug-resistant TLE and identified ROCK2 as one of the 20 most significantly increased genes in hippocampus. In vitro and in vivo experiments were performed to identify the potential role of ROCK2 in epileptogenesis. In addition, the activity of Stat3 pathway was tested in rat hippocampal tissues and primary cultured astrocytes. The expression levels of ROCK2 in the hippocampus of TLE patients were significantly increased compared with the control group, which was due to the hypomethylation of ROCK2 promoter. Fasudil, a specific Rho-kinase inhibitor, alleviated epileptic seizures in the pilocarpine rat model of TLE. Furthermore, ROCK2 activated the Stat3 pathway in pilocarpine-treated epilepsy rats, and the spearman correlation method confirmed that ROCK2 is associated with Stat3 activation in TLE patients. In addition, ROCK2 was predominantly expressed in astrocytes during epileptogenesis, and induced epileptogenesis by activating astrocyte cell cycle progression via Stat3 pathway. The overexpressed ROCK2 plays an important role in the pathogenesis of drug-resistant epilepsy. ROCK2 accelerates astrocytes cell cycle progression via the activation of Stat3 pathway likely provides the key to explaining the process of epileptogenesis.

OPCML Exerts Antitumor Effects in Cholangiocarcinoma via AXL/STAT3 Inactivation and Rho GTPase Down-regulation

BACKGROUND/AIM

Opioid-binding protein/cell adhesion molecule-like (OPCML) plays a crucial role in the suppression of tumor progression in several cancer types. Nevertheless, the association between OPCML functions and cholangiocarcinoma (CCA) progression remains unknown. We aimed to investigate biological functions of OPCML and related signaling pathways in CCA cell lines.

MATERIALS AND METHODS

Methylation status and ectopic expression of OPCML were determined in CCA cell lines using methylation-specific polymerase chain reaction and pcDNA3.1+/C-(K)DYK-OPCML, respectively. Cell proliferation, migration and invasion were investigated.

RESULTS

OPCML was found to be epigenetically silenced by DNA methylation. Ectopic expression of OPCML inhibited CCA proliferation by inducing apoptosis via AXL receptor tyrosine kinase/signal transducer and activator of transcription 3 (AXL/STAT3) inactivation. It also suppressed cell migration and invasion via down-regulation of Rho GTPases, ras homolog family member A (RHOA), Rac family small GTPase 1 (RAC1) and cell division cycle 42 (CDC42).

CONCLUSION

We are the first to unravel the antitumor effects and the related signaling pathways of OPCML in CCA. The loss of OPCML expression due to promoter hypermethylation can cause a decrease in cell death but increase in cell migration and invasion, which may at least in part contribute to CCA progression.

Attenuation of apoptotic cell detection triggers thymic regeneration after damage

The thymus, which is the primary site of T cell development, is particularly sensitive to insult but also has a remarkable capacity for repair. However, the mechanisms orchestrating regeneration are poorly understood, and delayed repair is common after cytoreductive therapies. Here, we demonstrate a trigger of thymic regeneration, centered on detecting the loss of dying thymocytes that are abundant during steady-state T cell development. Specifically, apoptotic thymocytes suppressed production of the regenerative factors IL-23 and BMP4 via TAM receptor signaling and activation of the Rho-GTPase Rac1, the intracellular pattern recognition receptor NOD2, and micro-RNA-29c. However, after damage, when profound thymocyte depletion occurs, this TAM-Rac1-NOD2-miR29c pathway is attenuated, increasing production of IL-23 and BMP4. Notably, pharmacological inhibition of Rac1-GTPase enhanced thymic function after acute damage. These findings identify a complex trigger of tissue regeneration and offer a regenerative strategy for restoring immune competence in patients whose thymic function has been compromised.

The Arabidopsis Rho of Plants GTPase ROP1 Is a Potential Calcium-Dependent Protein Kinase (CDPK) Substrate

Plant Rho-type GTPases (ROPs) are versatile molecular switches involved in a number of signal transduction pathways. Although it is well known that they are indirectly linked to protein kinases, our knowledge about their direct functional interaction with upstream or downstream protein kinases is scarce. It is reasonable to suppose that similarly to their animal counterparts, ROPs might also be regulated by phosphorylation. There is only, however, very limited experimental evidence to support this view. Here, we present the analysis of two potential phosphorylation sites of AtROP1 and two types of potential ROP-kinases. The S74 site of AtROP1 has been previously shown to potentially regulate AtROP1 activation dependent on its phosphorylation state. However, the kinase phosphorylating this evolutionarily conserved site could not be identified: we show here that despite of the appropriate phosphorylation site consensus sequences around S74 neither the selected AGC nor CPK kinases phosphorylate S74 of AtROP1 in vitro. However, we identified several phosphorylation sites other than S74 for the CPK17 and 34 kinases in AtROP1. One of these sites, S97, was tested for biological relevance. Although the mutation of S97 to alanine (which cannot be phosphorylated) or glutamic acid (which mimics phosphorylation) somewhat altered the protein interaction strength of AtROP1 in yeast cells, the mutant proteins did not modify pollen tube growth in an in vivo test.

Potential Therapeutic and Prognostic Values of LSM Family Genes in Breast Cancer

In recent decades, breast cancer (BRCA) has become one of the most common diseases worldwide. Understanding crucial genes and their signaling pathways remain an enormous challenge in evaluating the prognosis and possible therapeutics. The "Like-Smith" (LSM) family is known as protein-coding genes, and its member play pivotal roles in the progression of several malignancies, although their roles in BRCA are less clear. To discover biological processes associated with LSM family genes in BRCA development, high-throughput techniques were applied to clarify expression levels of LSMs in The Cancer Genome Atlas (TCGA)-BRCA dataset, which was integrated with the cBioPortal database. Furthermore, we investigated prognostic values of LSM family genes in BCRA patients using the Kaplan-Meier database. Among genes of this family, LSM4 expression levels were highly associated with poor prognostic outcomes with a hazard ratio of 1.35 (95% confidence interval 1.21-1.51, p for trend = 3.4 × 10-7). MetaCore and GlueGo analyses were also conducted to examine transcript expression signatures of LSM family members and their coexpressed genes, together with their associated signaling pathways, such as "Cell cycle role of APC in cell cycle regulation" and "Immune response IL-15 signaling via MAPK and PI3K cascade" in BRCA. Results showed that LSM family members, specifically LSM4, were significantly correlated with oncogenesis in BRCA patients. In summary, our results suggested that LSM4 could be a prospective prognosticator of BRCA.

MicroRNAs hsa-miR-618 and hsa-miR-297 Might Modulate the Pleiotropic Effects Exerted by Statins in Endothelial Cells Through the Inhibition of ROCK2 Kinase: in-silico Approach

Several studies show that statin therapy improves endothelial function by cholesterol-independent mechanisms called “pleiotropic effects.” These are due to the inhibition of the RhoA/ROCK kinase pathway, its inhibition being an attractive atheroprotective treatment. In addition, recent work has shown that microRNAs, posttranscriptional regulators of gene expression, can affect the response of statins and their efficacy. For this reason, the objective of this study was to identify by bioinformatic analysis possible new microRNAs that could modulate the pleiotropic effects exerted by statins through the inhibition of ROCK kinases. A bioinformatic study was performed in which the differential expression of miRNAs in endothelial cells was compared under two conditions: Control and treated with simvastatin at 10 μM for 24 h, using a microarray. Seven miRNAs were differentially expressed, three up and four down. Within the up group, the miRNAs hsa-miR-618 and hsa-miR-297 present as a predicted target to ROCK2 kinase. Also, functional and enriched pathway analysis showed an association with mechanisms associated with atheroprotective effects. This work shows an in-silico approach of how posttranscriptional regulation mediated by miRNAs could modulate the pleiotropic effects exerted by statins on endothelial cells, through the inhibition of ROCK2 kinase and its effects.

CRIF1 deficiency suppresses endothelial cell migration via upregulation of RhoGDI2

Rho GDP-dissociation inhibitor (RhoGDI), a downregulator of Rho family GTPases, prevents nucleotide exchange and membrane association. It is responsible for the activation of Rho GTPases, which regulate a variety of cellular processes, such as migration. Although RhoGDI2 has been identified as a tumor suppressor gene involved in cellular migration and invasion, little is known about its role in vascular endothelial cell (EC) migration. CR6-interacting factor 1 (CRIF1) is a CR6/GADD45-interacting protein with important mitochondrial functions and regulation of cell growth. We examined the expression of RhoGDI2 in CRIF1-deficient human umbilical vein endothelial cells (HUVECs) and its role in cell migration. Expression of RhoGDI2 was found to be considerably higher in CRIF1-deficient HUVECs along with suppression of cell migration. Moreover, the phosphorylation levels of Akt and CREB were decreased in CRIF1-silenced cells. The Akt-CREB signaling pathway was implicated in the changes in endothelial cell migration caused by CRIF1 downregulation. In addition to RhoGDI2, we identified another factor that promotes migration and invasion of ECs. Adrenomedullin2 (ADM2) is an autocrine/paracrine factor that regulates vascular tone and other vascular functions. Endogenous ADM2 levels were elevated in CRIF1-silenced HUVECs with no effect on cell migration. However, siRNA-mediated depletion of RhoGDI2 or exogenous ADM2 administration significantly restored cell migration via the Akt-CREB signaling pathway. In conclusion, RhoGDI2 and ADM2 play important roles in the migration of CRIF1-deficient endothelial cells.

ELMO1 Regulates RANKL-Stimulated Differentiation and Bone Resorption of Osteoclasts

Bone homeostasis is a metabolic balance between the new bone formation by osteoblasts and old bone resorption by osteoclasts. Excessive osteoclastic bone resorption results in low bone mass, which is the major cause of bone diseases such as rheumatoid arthritis. Small GTPases Rac1 is a key regulator of osteoclast differentiation, but its exact mechanism is not fully understood. ELMO and DOCK proteins form complexes that function as guanine nucleotide exchange factors for Rac activation. Here, we report that ELMO1 plays an important role in differentiation and bone resorption of osteoclasts. Osteoclast precursors derived from bone marrow monocytes (BMMs) of Elmo1^–/– mice display defective adhesion and migration during differentiation. The cells also have a reduced activation of Rac1, p38, JNK, and AKT in response to RANKL stimulation. Importantly, we show that bone erosion is alleviated in Elmo1^–/– mice in a rheumatoid arthritis mouse model. Taken together, our results suggest that ELMO1, as a regulator of Rac1, regulates osteoclast differentiation and bone resorption both in vitro and in vivo.

Actin cytoskeleton deregulation confers midostaurin resistance in FLT3-mutant acute myeloid leukemia

The presence of FMS-like tyrosine kinase 3-internal tandem duplication (FLT3-ITD) is one of the most frequent mutations in acute myeloid leukemia (AML) and is associated with an unfavorable prognosis. FLT3 inhibitors, such as midostaurin, are used clinically but fail to entirely eradicate FLT3-ITD + AML. This study introduces a new perspective and highlights the impact of RAC1-dependent actin cytoskeleton remodeling on resistance to midostaurin in AML. RAC1 hyperactivation leads resistance via hyperphosphorylation of the positive regulator of actin polymerization N-WASP and antiapoptotic BCL-2. RAC1/N-WASP, through ARP2/3 complex activation, increases the number of actin filaments, cell stiffness and adhesion forces to mesenchymal stromal cells (MSCs) being identified as a biomarker of resistance. Midostaurin resistance can be overcome by a combination of midostaruin, the BCL-2 inhibitor venetoclax and the RAC1 inhibitor Eht1864 in midostaurin-resistant AML cell lines and primary samples, providing the first evidence of a potential new treatment approach to eradicate FLT3-ITD + AML.

Garitano-Trojaola et al. used a combination of human acute myeloid leukemia (AML) cell lines and primary samples to show that RAC1-dependent actin cytoskeleton remodeling through BCL2 family plays a key role in resistance to the FLT3 inhibitor, Midostaurin in AML. They showed that by targeting RAC1 and BCL2, Midostaurin resistance was diminished, which potentially paves the way for an innovate treatment approach for FLT3 mutant AML.

Mechanisms Underlying the Comorbidity of Schizophrenia and Type 2 Diabetes Mellitus

The mortality rate of patients with schizophrenia is high, and life expectancy is shorter by 10 to 20 years. Metabolic abnormalities including type 2 diabetes mellitus (T2DM) are among the main reasons. The prevalence of T2DM in patients with schizophrenia may be epidemiologically frequent because antipsychotics induce weight gain as a side effect and the cognitive dysfunction of patients with schizophrenia relates to a disordered lifestyle, poor diet, and low socioeconomic status. Apart from these common risk factors and risk factors unique to schizophrenia, accumulating evidence suggests the existence of common susceptibility genes between schizophrenia and T2DM. Functional proteins translated from common genetic susceptibility genes are known to regulate neuronal development in the brain and insulin in the pancreas through several common cascades. In this review, we discuss common susceptibility genes, functional cascades, and the relationship between schizophrenia and T2DM. Many genetic and epidemiological studies have reliably associated the comorbidity of schizophrenia and T2DM, and it is probably safe to think that common cascades and mechanisms suspected from common genes' functions are related to the onset of both schizophrenia and T2DM. On the other hand, even when genetic analyses are performed on a relatively large number of comorbid patients, the results are sometimes inconsistent, and susceptibility genes may carry only a low or moderate risk. We anticipate future directions in this field.