Rho GTPases and their role in organizing the actin cytoskeleton

The Regulation of Pericellular Matrix Synthesis During Articular Cartilage Tissue Engineering

Articular cartilage, vital to the health and functioning of joints, remains challenging to regenerate. The pericellular matrix (PCM) is critical for transducing biophysical stimuli to the articular chondrocytes (ACs) that it envelops. Given the mechanobiological sensitivity of ACs, it is pivotal in maintaining the chondrogenic phenotype and the production of extracellular matrix (ECM) during articular cartilage tissue engineering. While the maintenance of the native PCM significantly improves the quality of neocartilage, current isolation methods are limited. A solution to this challenge is facilitating ACs to regenerate their PCM. However, the regulation of PCM synthesis remains poorly understood, hindering the development of effective tissue engineering strategies. This narrative review aims to provide a comprehensive analysis of the complex interplay between extracellular cues and intracellular pathways regulating PCM synthesis during articular cartilage tissue engineering. Our analysis reveals that mechanical cues, such as material stiffness and mechanical stimulation, are the primary regulators of PCM synthesis. Additionally, the use of scaffold-free techniques potentially affects the structuring of newly created PCM. Tuning these stimuli can significantly impact the quality of the formed PCM, ultimately influencing neocartilage quality. Furthermore, we highlight intracellular mechanisms involved in the transduction of these extracellular cues, including actin polymerization, yes-associated protein and transcriptional coactivator with PDZ-binding motif localization, and transforming growth factor beta-induced Smad signaling. Although the current literature suggests the involvement of these signaling pathways in regulating the synthesis of PCM components, we found that studies investigating these processes in ACs are lacking. Elucidating the relationships between extracellular stimuli, intracellular signaling, and the expression of PCM components could provide a framework for designing new cartilage tissue engineering approaches that facilitate proper PCM synthesis. Ultimately, this can improve ECM quality and advance articular cartilage regeneration.

Diallyl disulfide in oncotherapy: molecular mechanisms and therapeutic potentials

Garlic possesses a broad spectrum of medicinal properties, such as anti-cancer, antioxidant, anti-diabetic effects, and protective effects on the heart, nervous system, and liver. Diallyl disulfide (DADS), an oil-soluble organic sulfur-containing compound in garlic, has garnered attention in recent years for its demonstrated anti-cancer efficacy in various cancer types such as leukemia, breast cancer, hepatocellular carcinoma, stomach cancer, and prostate cancer. The anticancer properties of DADS are attributed to its ability to suppress cancer cell proliferation, impede invasion and metastasis, as well as induce apoptosis, promote differentiation, and facilitate cell cycle arrest. Although many literatures have reviewed the pharmacokinetics, molecular mechanisms of anti-cancer effects and some clinical trials of DADS, the specific mechanisms and clinical-translational therapeutic potentials have not been elucidated. This comprehensive review focuses on delineating the molecular mechanisms underlying the anticancer effects of DADS, with a particular emphasis on its potential utility as a therapeutic intervention in the clinical management of cancer, and analyzes the challenges and coping strategies faced in the application of DADS as an anti-cancer drug, pointing out the directions for scientific research.

The biochemical mechanism of Rho GTPase membrane binding, activation and retention in activity patterning

Rho GTPases form plasma membrane-associated patterns that control the cytoskeleton during cell division, morphogenesis, migration, and wound repair. Their patterning involves transitions between inactive cytosolic and active membrane-bound states, regulated by guanine nucleotide exchange factors (GEFs), GTPase-activating proteins (GAPs), and guanine nucleotide dissociation inhibitors (GDIs). However, the relationships between these transitions and role of different regulators remain unclear. We developed a novel reconstitution approach to study Rho GTPase patterning with all major GTPase regulators in a biochemically defined system. We show that Rho GTPase dissociation from RhoGDI is rate-limiting for its membrane association. Rho GTPase activation occurs after membrane insertion, which is unaffected by GEF activity. Once activated, Rho GTPases are retained at the membrane through effector interactions, essential for their enrichment at activation sites. Thus, high cytosolic levels of RhoGDI-bound GTPases ensure a constant supply of inactive GTPases for the membrane, where GEF-mediated activation and effector binding stabilize them. These results delineate the route by which Rho GTPase patterns are established and define stage-dependent roles of its regulators.

Astrocyte-synapse structural plasticity in neurodegenerative and neuropsychiatric diseases

Synaptic dysfunction is a common feature across a broad spectrum of brain diseases, spanning from psychopathologies such as post-traumatic stress disorder (PTSD) and substance use disorders (SUD) to neurodegenerative diseases like Alzheimer's and Parkinson's disease (AD and PD). While neuroscience research aiming to understand the mechanisms underlying synaptic dysfunction has traditionally focused on the neuronal elements of the synapse, recent research increasingly acknowledges the contribution of astrocytes as a third element controlling synaptic transmission. This also sparked interest to investigate the tripartite synapse and its role in the etiology of neurological diseases. According to recent evidence, changes in the structural interaction between astrocytes and synapses not only play a pivotal role in modulating synaptic function and behavioral states, but are also implicated in the initiation and progression of various brain diseases. This review aims to integrate recent findings that provide insight into the molecular mechanisms underpinning astrocytic structural changes at the synapse. We offer a comprehensive discussion of the potential implications of compromised astrocyte-synapse interactions, and put forward that astrocytic synaptic coverage is generally reduced in numerous neurological disorders, with the extent of it being disease- and stage- specific. Finally, we propose outstanding questions on astrocyte-synapse structural plasticity that are relevant for future therapeutic strategies to tackle neurodegenerative and neuropsychiatric diseases.

Pard3 promotes corneal epithelial stratification and homeostasis by regulating apical-basal polarity, cytoskeletal organization and tight junction-mediated barrier function

PURPOSE

To document the expression of apical-basal polarity (ABP) determinants in the mouse corneal epithelium (CE) and elucidate the functions of Pard3 in establishment and maintenance of ABP, stratification, homeostasis, and barrier function in the CE.

METHODS

Pard3Δ/ΔC mice (Pard3LoxP/LoxP; Aldh3A1-Cre/+) with cornea-specific Pard3 ablation were generated by breeding Aldh3A1-Cre/+ with Pard3LoxP/LoxP mice. The control (Aldh3A1-Cre/+ or Pard3LoxP/LoxP alone) and Pard3Δ/ΔC corneal histology, ocular surface properties, barrier function, and actin cytoskeleton were assessed by Haematoxylin and Eosin staining of paraformaldehyde-fixed, paraffin-embedded tissues, scanning electron microscopy, fluorescein staining, and phalloidin staining, respectively. The expression of specific markers of interest was evaluated by qRT-PCR, immunoblots and immunofluorescent staining.

RESULTS

Dynamic changes were observed in the expression and localization of ABP determinants as the CE stratified and matured between post-natal day 5 (PN5) and PN52. Adult Pard3Δ/ΔC CE contained fewer cell layers with rounded basal cells, and loosely adherent superficial cells lacking microplicae. Adult Pard3Δ/ΔC CE also displayed impaired barrier function with decreased expression of tight junction, adherens junction, and desmosome components, disrupted actin cytoskeletal organization, increased proliferation, and upregulation of transcription factors that drive epithelial-mesenchymal transition (EMT).

CONCLUSIONS

Disruption of ABP in Pard3Δ/ΔC CE, altered expression of cell junction complex components and disorganized actin cytoskeleton, increased cell proliferation, and upregulated EMT transcription factors suggest that the ABP-determinant Pard3 promotes CE features while suppressing mesenchymal cell fate. Collectively, these results elucidate that Pard3-mediated ABP is essential for CE stratification, homeostasis and barrier function.

ARHGAP29 promotes keratinocyte proliferation and migration in vitro and is dispensable for in vivo wound healing

BACKGROUND

RhoA GTPases play critical roles in actin cytoskeletal remodeling required for controlling a diverse range of cellular functions including cell proliferation, adhesion, migration and changes in cell shape, all required for cutaneous wound healing. RhoA cycles between an active GTP-bound and an inactive GDP-bound form, a process regulated by guanine nucleotide exchange factors (GEFs) and GTPase-activating proteins (GAPs). ARHGAP29 is a GAP expressed in skin keratinocytes and is decreased in the absence of interferon regulator factor 6, a critical regulator of cell proliferation, migration, and wound healing. However, the role for ARHGAP29 in keratinocyte biology is unknown.

RESULTS

We generated ARHGAP29 knockdown keratinocyte cell lines and show they displayed increased filamentous actin, phospho-myosin regulatory light chain, cell area and population doubling time. Furthermore, we found that ARHGAP29 knockdown keratinocytes displayed significant delays in scratch wound closure in both single and collective cell migration conditions; these delays were rescued by both adding back ARHGAP29 or adding a ROCK inhibitor to ARHGAP29 knockdown cells. In vivo, however, Arhgap29 heterozygotes or keratinocyte-specific knockouts showed on-time wound healing.

CONCLUSIONS

These data demonstrate that ARHGAP29 is required for keratinocyte morphology, proliferation and migration in vitro but is dispensable during wound healing in vivo.

Volume-Regulated Anion Channel Complex Modulates Mechano-Electrical Signal Responses in Human Airway Smooth Muscle Shortening

LRRC8A (leucine-rich repeat containing 8A) is an obligatory constituent of the volume-regulated anion channel (VRAC) that is fundamental to a wide range of biological processes, including regulating cell size, proliferation, and migration. Here we explored the physiological role of VRAC in excitation-contraction (E-C) coupling and shortening of human airway smooth muscle (HASM). In HASM cells, pharmacological inhibition of VRAC with DCPIB (4-[2-butyl-6,7-dichloro-2-cyclopentyl-indan-1-on-5-yl]) (0.1-10 μM) markedly attenuated swell-activated Cl- conductance, and contractile agonist (histamine or carbachol)-induced cellular stiffening as measured by single-cell patch-clamp and optical magnetic twisting cytometry, respectively. In addition, HASM cells treated with DCPIB or transfected with LRRC8A-targeting siRNA showed reduced agonist-induced phosphorylation of protein kinase B (i.e., AKT), paxillin, MYPT1, and myosin light chain. Consistent with the changes of these E-C coupling effectors, DCPIB appreciably decreased agonist-induced small airways narrowing in human precision-cut lung slices. Taken together, our findings shed new light on the mechanistic link between HASM shortening and regulatory volume decrease via LRRC8A, revealing a previously unrecognized nodal point for modulation of E-C coupling and acute airway constriction.

Stiff extracellular matrix activates the transcription factor ATF5 to promote the proliferation of cancer cells

Cancer tissues are stiffer than normal tissues. Carcinogenesis stiffens the extracellular matrix (ECM) of cancerous tissues, to which cancer cells respond by activating transcription factors, such as YAP/TAZ, Twist1, and β-catenin, which further elevate their malignancy. However, these transcription factors are also expressed in normal tissues. Therefore, inhibiting these factors in order to treat cancer may lead to severe side effects. Here, we show that activating transcription factor 5 (ATF5), highly expressed in tumors, is activated by ECM stiffness and promotes the proliferation of cancer cells, including that of pancreatic cancer cells and lung cancer cells. In addition, ATF5 suppressed the expression of early growth response 1 (EGR1), thereby accelerating cancer cell proliferation. Stiff ECMs trigger the JAK-MYC pathway which activates ATF5. JAK activation was actomyosin independent whereas MYC induction was actomyosin dependent. These results demonstrate the critical role played by ATF5 in the mechanotransduction process seen in cancers.

Thyroid Hormones and Brain Development: A Focus on the Role of Mitochondria as Regulators of Developmental Time

Thyroid hormones (THs) regulate metabolism in a homeostatic state in an adult organism. During the prenatal period, prior to the establishment of homeostatic mechanisms, THs assume additional functions as key regulators of brain development. Here, we focus on reviewing the role of THs in orchestrating cellular dynamics in a developing brain. The evidence from the reviewed scientific literature suggests that the developmental roles of the hormones are predominantly mediated by non-genomic mitochondrial effects of THs due to attenuation of genomic effects of THs that antagonise non-genomic impacts. We argue that the key function of TH signalling during brain development is to orchestrate the tempo of self-organisation of neural progenitor cells. Further, evidence is provided that major neurodevelopmental consequences of hypothyroidism stem from an altered tempo of cellular self-organisation.

Mechanisms and therapeutic potential of disulphidptosis in cancer

SLC7A11 plays a pivotal role in tumour development by facilitating cystine import to enhance glutathione synthesis and counteract oxidative stress. Disulphidptosis, an emerging form of cell death observed in cells with high expression of SLC7A11 under glucose deprivation, is regulated through reduction-oxidation reactions and disulphide bond formation. This process leads to contraction and collapse of the F-actin cytoskeleton from the plasma membrane, ultimately resulting in cellular demise. Compared to other forms of cell death, disulphidptosis exhibits distinctive characteristics and regulatory mechanisms. This mechanism provides novel insights and innovative strategies for cancer treatment while also inspiring potential therapeutic approaches for other diseases. Our review focuses on elucidating the molecular mechanism underlying disulphidptosis and its connection with the actin cytoskeleton, identifying alternative metabolic forms of cell death, as well as offering insights into disulphidptosis-based cancer therapy. A comprehensive understanding of disulphidptosis will contribute to our knowledge about fundamental cellular homeostasis and facilitate the development of groundbreaking therapies for disease treatment.

Spatiotemporal analysis of F-actin polymerization with micropillar arrays reveals synchronization between adhesion sites

We repurposed micropillar arrays to quantify spatiotemporal inter-adhesion communication. Following the observation that integrin adhesions formed around pillar tops we relied on the precise repetitive spatial control of the pillars to reliably monitor F-actin dynamics in mouse embryonic fibroblasts as a model for spatiotemporal adhesion-related intracellular signaling. Using correlation-based analyses, we revealed localized information flows propagating between adjacent pillars that were integrated over space and time to synchronize the adhesion dynamics within the entire cell. Probing the mechanical regulation, we discovered that stiffer pillars or partial actomyosin contractility inhibition enhances inter-adhesion F-actin synchronization, and that inhibition of Arp2/3, but not formin, reduces synchronization. Our results suggest that adhesions can communicate and highlight the potential of using micropillar arrays as a tool to measure spatiotemporal intracellular signaling.

Gene therapy for glaucoma: Targeting key mechanisms

Glaucoma is a group of optic neuropathies characterised by progressive retinal ganglion cell (RGC) degeneration and is the leading cause of irreversible blindness worldwide. Current treatments for glaucoma focus on reducing intraocular pressure (IOP) with topical medications. However, many patients do not achieve sufficient IOP reductions with such treatments. Patient compliance to dosing schedules also poses a significant challenge, further limiting their effectiveness. While surgical options exist for resistant cases, these are invasive and carry risks of complications. Thus, there is a critical need for better strategies to prevent irreversible vision loss in glaucoma. Gene therapy holds significant promise in this regard, offering potential long-term solutions by targeting the disease's underlying causes at a molecular level. Gene therapy strategies for glaucoma primarily target the two key hallmarks of the disease: elevated IOP and RGC death. This review explores key mechanisms underlying these hallmarks and discusses the current state of gene therapies targeting them. In terms of IOP reduction, this review covers strategies aimed at enhancing extracellular matrix turnover in the conventional outflow pathway, targeting fibrosis, regulating aqueous humor production, and targeting myocilin for gene-specific therapy. Neuroprotective strategies explored include targeting neurotrophic factors and their receptors, reducing oxidative stress and mitochondrial dysfunction, and preventing Wallerian degeneration. This review also briefly highlights key research priorities for advancing gene therapies for glaucoma through the clinical pipeline, such as refining delivery vectors and improving transgene regulation. Addressing these priorities will be essential for translating advancements from preclinical models into effective clinical therapies for glaucoma.

Loss of Cdc42 causes abnormal optic cup morphogenesis and microphthalmia in mouse

Congenital ocular malformations originate from defective morphogenesis during early eye development and cause 25% of childhood blindness. Formation of the eye is a multi-step, dynamic process; it involves evagination of the optic vesicle, followed by distal and ventral invagination, leading to the formation of a two-layered optic cup with a transient optic fissure. These tissue folding events require extensive changes in cell shape and tissue growth mediated by cytoskeleton mechanics and intercellular adhesion. We hypothesized that the Rho GTPase Cdc42 may be an essential, convergent effector downstream of key regulatory factors required for ocular morphogenesis. CDC42 controls actin remodeling, apicobasal polarity, and junction assembly. Here we identify a novel essential function for Cdc42 during eye morphogenesis in mouse; in Cdc42 mutant eyes expansion of the ventral optic cup is arrested, resulting in microphthalmia and a wide coloboma. Our analyses show that Cdc42 is required for expression of the polarity effector proteins PRKCZ and PARD6, intercellular junction protein tight junction protein 1, β-catenin, actin cytoskeleton F-actin, and contractile protein phospho myosin light chain 2. Expression of RPE fate determinants OTX2 and MITF, and formation of the RPE layer are severely affected in the temporal domain of the proximal optic cup. EdU incorporation is significantly downregulated. In addition, mitotic retinal progenitor cells mislocalize deeper, basal regions, likely contributing to decreased proliferation. We propose that morphogenesis of the ventral optic cup requires Cdc42 function for coordinated optic cup expansion and establishment of subretinal space, tissue tension, and differentiation of the ventral RPE layer.

Microenvironments‐Modulated Biomaterials Enhance Spinal Cord Injury Therapy

Spinal cord injury (SCI) results from various causes, including sports‐related incidents, degenerative cervical myelopathy, traffic accidents, and falls. SCI typically leads to sensory and motor dysfunction and even paralysis. Current treatments for SCI include systemic administration of high‐dose steroids and surgical decompression and stabilization. However, excessive use of glucocorticoids may increase susceptibility to infections and systemic bleeding. The long‐term effect of surgery intervention remains unclear, with ongoing debates regarding its timing, efficacy, and safety. Therefore, innovative approaches are urgently needed to alleviate secondary injuries and promote spinal recovery. One emerging therapeutic approach for SCI is modulating the microenvironments to achieve neuroprotection and neurogenesis during recovery. Several biomaterials with favorable physicochemical properties have been developed to enhance therapeutic effects by regulating microenvironments. This Review first discusses the pathology of SCI microenvironments and then introduces biomaterials‐based regulatory strategies targeting various microenvironmental components, including anti‐inflammation, anti‐oxidation, reduction of excitotoxicity, revascularization, neurogenesis, and scar density reduction. Additionally, the research and clinical application prospects for microenvironment regulation are presented.

Loss of Cdc42 causes abnormal optic cup morphogenesis and microphthalmia in mouse

Congenital ocular malformations originate from defective morphogenesis during early eye development and cause 25% of childhood blindness. Formation of the eye is a multi-step, dynamic process; it involves evagination of the optic vesicle, followed by distal and ventral invagination, leading to the formation of a two-layered optic cup with a transient optic fissure. These tissue folding events require extensive changes in cell shape and tissue growth mediated by cytoskeleton mechanics and intercellular adhesion. We hypothesized that the Rho GTPase Cdc42 may be an essential, convergent effector downstream of key regulatory factors required for ocular morphogenesis. CDC42 controls actin remodeling, apicobasal polarity, and junction assembly. Here we identify a novel essential function for Cdc42 during eye morphogenesis in mouse; in Cdc42 mutant eyes expansion of the ventral optic cup is arrested, resulting in microphthalmia and a wide coloboma. Our analyses show that Cdc42 is required for expression of the polarity effector proteins PRKCZ and PARD6, intercellular junction protein tight junction protein 1, β-catenin, actin cytoskeleton F-actin, and contractile protein phospho myosin light chain 2. Expression of RPE fate determinants OTX2 and MITF, and formation of the RPE layer are severely affected in the temporal domain of the proximal optic cup. EdU incorporation is significantly downregulated. In addition, mitotic retinal progenitor cells mis-localized deeper, basal regions, likely contributing to decreased proliferation. We propose that morphogenesis of the ventral optic cup requires Cdc42 function for coordinated optic cup expansion and establishment of subretinal space, tissue tension, and differentiation of the ventral RPE layer.

Inhibition of RHOA activity preserves the survival and hemostasis function of long-term cold-stored platelets

ABSTRACT

Patients with thrombocytopenia require platelet transfusion to prevent and stop hemorrhage. Cold storage of platelets results in complex molecular lesions, including changes in membrane microdomains that are recognized by host macrophages and hepatocyte counter-receptors, resulting in phagocytosis and clearance upon transfusion. For this reason, platelets are stored at room temperature, a method that confers increased risk of bacterial contamination. By applying signaling analysis and genetic and pharmacological approaches, we identified that cold-induced activation of RAS homolog family, member A (RHOA) GTPase causes the major hallmarks of platelet cold storage lesions. RHOA deficiency renders murine platelets insensitive to cold storage-induced damage, and pharmacological inhibition by a RHOA activation inhibitor, R-G04, can prevent the cold storage-induced lesions. RHOA inhibition prevents myosin activation and clathrin-independent formation and internalization of lipid rafts enriched in active glycosyltransferases as well as abnormal distribution of GPIbα. RHOA inhibition further prevents the metabolic reprogramming of cold storage-induced lesions and allows the maintenance of glycolytic flux and mitochondria-dependent respiration. Importantly, human platelets transfused in mice after cold storage, in the presence of R-G04 or its more potent enantiomer S-G04, can circulate in vivo at similar levels as room temperature-stored platelets while retaining their hemostatic activity in vivo, as assessed by bleeding time correction in aspirin-treated mice. Our studies provide a mechanism-based translational approach to prevent cold storage-induced damage, which is useful for human platelet transfusion in patients with thrombocytopenia.

Androgen receptor activation inhibits endothelial cell migration in vitro and angiogenesis in vivo

Our previous research revealed that androgen receptor (AR) activation reduces endothelial cell proliferation via non-genomic pathways. We hypothesized that AR activation might also affect endothelial cell migration, a critical step in angiogenesis. Our data demonstrates that treatment of human umbilical vein endothelial cells (HUVECs) with AR agonists, metribolone (R1881) or dihydrotestosterone (DHT), results in a dose-dependent reduction in migration, which can be reversed by AR antagonists or AR knockdown. Mechanistically, R1881 inhibits HUVEC migration by suppressing RhoA activity through the cSrc/FAK/paxillin pathway and promoting RhoA degradation via RhoA-p27 complex formation, ultimately resulting in RhoA ubiquitination. Transfection with constitutively active RhoA-V14 rescues the inhibitory effect of R1881 on HUVEC migration. Furthermore, R1881 elevates intracellular vascular endothelial growth factor (VEGF) and connective tissue growth factor (CTGF) levels but reduces VEGF secretion from HUVECs. This reduction is attributed to the formation of VEGF-CTGF complexes in the cytosol induced by R1881. Transfection with RhoA-V14 reduces CTGF levels and VEGF-CTGF complex formation, leading to enhanced VEGF secretion. Pre-treatment with WP631, a CTGF inhibitor, mitigates the R1881-induced reduction in VEGF secretion and HUVECs migration. In vivo assessments using zebrafish angiogenesis and mouse matrigel plug assays validate the anti-angiogenic effects of R1881. These findings provide insight into the molecular mechanisms through which AR activation modulates endothelial cell migration and angiogenesis.

Cardiovascular adaptations in microgravity conditions

Gravity has had a significant impact on the evolution of life on Earth with organisms developing necessary biological adaptations over billions of years to counter this ever-existing force. There has been an exponential increase in experiments using real and simulated gravity environments in the recent years. Although an understanding followed by discovery of counter measures to negate diminished gravity in space had been the driving force of research initially, there has since been a phenomenal leap wherein a force unearthly as microgravity is beginning to show promising potential. The current review summarizes pathophysiological changes that occur in multiple aspects of the cardiovascular system when exposed to an altered gravity environment leading to cardiovascular deconditioning and orthostatic intolerance. Gravity influences not just the complex multicellular systems but even the survival of organisms at the molecular level by intervening fundamental cellular processes, directly affecting those linked to actin and microtubule organization via mechano-transduction pathways. The reach of gravity ranges from cytoskeletal rearrangement that regulates cell adhesion and migration to intracellular dynamics that dictate cell fate commitment and differentiation. An understanding that microgravity itself is not present on Earth propels the scope of simulated gravity conditions to be a unique and useful environment that could be explored for enhancing the potential of stem cells for a wide range of applications as has been highlighted here.

A proximity proteomics pipeline with improved reproducibility and throughput

Proximity labeling (PL) via biotinylation coupled with mass spectrometry (MS) captures spatial proteomes in cells. Large-scale processing requires a workflow minimizing hands-on time and enhancing quantitative reproducibility. We introduced a scalable PL pipeline integrating automated enrichment of biotinylated proteins in a 96-well plate format. Combining this with optimized quantitative MS based on data-independent acquisition (DIA), we increased sample throughput and improved protein identification and quantification reproducibility. We applied this pipeline to delineate subcellular proteomes across various compartments. Using the 5HT2A serotonin receptor as a model, we studied temporal changes of proximal interaction networks induced by receptor activation. In addition, we modified the pipeline for reduced sample input to accommodate CRISPR-based gene knockout, assessing dynamics of the 5HT2A network in response to perturbation of selected interactors. This PL approach is universally applicable to PL proteomics using biotinylation-based PL enzymes, enhancing throughput and reproducibility of standard protocols.

Cortactin: A major cellular target of viral, protozoal, and fungal pathogens

Many viral, protozoal, and fungal pathogens represent major human and animal health problems due to their great potential of causing infectious diseases. Research on these pathogens has contributed substantially to our current understanding of both microbial virulence determinants and host key factors during infection. Countless studies have also shed light on the molecular mechanisms of host-pathogen interactions that are employed by these microbes. For example, actin cytoskeletal dynamics play critical roles in effective adhesion, host cell entry, and intracellular movements of intruding pathogens. Cortactin is an eminent host cell protein that stimulates actin polymerization and signal transduction, and recently emerged as fundamental player during host-pathogen crosstalk. Here we review the important role of cortactin as major target for various prominent viral, protozoal and fungal pathogens in humans, and its role in human disease development and cancer progression. Most if not all of these important classes of pathogens have been reported to hijack cortactin during infection through mediating up- or downregulation of cortactin mRNA and protein expression as well as signaling. In particular, pathogen-induced changes in tyrosine and serine phosphorylation status of cortactin at its major phospho-sites (Y-421, Y-470, Y-486, S-113, S-298, S-405, and S-418) are addressed. As has been reported for various Gram-negative and Gram-positive bacteria, many pathogenic viruses, protozoa, and fungi also control these regulatory phospho-sites, for example, by activating kinases such as Src, PAK, ERK1/2, and PKD, which are known to phosphorylate cortactin. In addition, the recruitment of cortactin and its interaction partners, like the Arp2/3 complex and F-actin, to the contact sites between pathogens and host cells is highlighted, as this plays an important role in the infection process and internalization of several pathogens. However, there are also other ways in which the pathogens can exploit the function of cortactin for their needs, as the cortactin-mediated regulation of cellular processes is complex and involves numerous different interaction partners. Here, the current state of knowledge is summarized.

A Co-MOF encapsulated microneedle patch activates hypoxia induction factor-1 to pre-protect transplanted flaps from distal ischemic necrosis

Avoiding ischemic necrosis after flap transplantation remains a significant clinical challenge. Developing an effective pretreatment method to promote flap survival postoperatively is crucial. Cobalt chloride (CoCl2) can increase cell tolerance to ischemia and hypoxia condition by stimulating hypoxia-inducible factor-1 (HIF-1) expression. However, the considerable toxic effects severely limit the clinical application of CoCl2. In this study, cobalt-based metal-organic frameworks (Co-MOF) encapsulated in a microneedle patch (Co-MOF@MN) was developed to facilitate the transdermal sustained release of Co2+ for rapid, minimally invasive rapid pretreatment of flap transplantation. The MN patch was composed of a fully methanol-based two-component cross-linked polymer formula, with a pyramid structure and high mechanical strength, which satisfied the purpose of penetrating the skin stratum corneum of rat back to achieve subcutaneous vascular area administration. Benefiting from the water-triggered disintegration of Co-MOF and the transdermal delivery via the MN patch, preoperative damage and side effects were effectively mitigated. Moreover, in both the oxygen-glucose deprivation/recovery (OGD/R) cell model and the rat dorsal perforator flap model, Co-MOF@MN activated the HIF-1α pathway and its associated downstream proteins, which reduced reperfusion oxidative damage, improved blood supply in choke areas, and increased flap survival rates post-transplantation. This preprotection strategy, combining MOF nanoparticles and the MN patch, meets the clinical demands for trauma minimization and uniform administration in flap transplantation. STATEMENT OF SIGNIFICANCE: Cobalt chloride (CoCl2) can stimulate the expression of hypoxia-inducible factor (HIF-1) and improve the tolerance of cells to ischemia and hypoxia conditions. However, the toxicity and narrow therapeutic window of CoCl2 severely limit its clinical application. Herein, we explored the role of Co-MOF as a biocompatible nanocage for sustained release of Co2+, showing the protective effect on vascular endothelial cells in the stress model of oxygen-glucose deprivation. To fit the clinical needs of minimal trauma in flap transplantation, a Co-MOF@MN system was developed to achieve local transdermal delivery at the choke area, significantly improving blood supply opening and flap survival rate. This strategy of two-step delivery of Co2+ realized the enhancement of biological functions while ensuring the biosafety.

Mechano-metabolism of metastatic breast cancer cells in 2D and 3D microenvironments

Cells regulate their shape and metabolic activity in response to the mechano-chemical properties of their microenvironment. To elucidate the impact of matrix stiffness and ligand density on the bioenergetics of mesenchymal cells, we developed a nonequilibrium, active chemo-mechanical model that accounts for the mechanical energy of the cell and matrix, chemical energy from ATP hydrolysis, interfacial energy, and mechano-sensitive regulation of stress fiber assembly through signaling. By integrating the kinetics and energetics of these processes, we define the cell "metabolic potential" that, when minimized, provides testable predictions of cell contractility, shape, and ATP consumption. Specifically, we show that the morphology of MDA-MB-231 breast cancer cells in 3D collagen changes from spherical to elongated to spherical with increasing matrix stiffness, which is consistent with experimental observations. On 2D hydrogels, our model predicts a hemispherical-to-spindle-to-disc shape transition with increasing gel stiffness. In both cases, we show that these shape transitions emerge from competition between the energy of ATP hydrolysis associated with increased contractility that drives cell elongation and the interfacial energy that favors a rounded shape. Furthermore, our model can predict how increased energy demand in stiffer microenvironments is met by AMPK activation, which is confirmed experimentally in both 2D and 3D microenvironments and found to correlate with the upregulation of mitochondrial potential, glucose uptake, and ATP levels, as well as provide estimates of changes in intracellular adenosine nucleotide concentrations with changing environmental stiffness. Overall, we present a framework for relating adherent cell energy levels and contractility through biochemical regulation of underlying physical processes.

Statement of Significance

Increasing evidence indicates that cellular metabolism is regulated by mechanical cues from the extracellular environment. Forces transmitted from the microenvironment activate mechanotransduction pathways in the cell, which trigger a cascade of biochemical events that impact cytoskeletal tension, cellular morphology and energy budget available to the cell. Using a nonequilibrium free energy-based theory, we can predict the ATP consumption, contractility, and shape of mesenchymal cancer cells, as well as how cells regulate energy levels dependent on the mechanosensitive metabolic regulator AMPK. The insights from our model can be used to understand the mechanosensitive regulation of metabolism during metastasis and tumor progression, during which cells experience dynamic changes in their microenvironment and metabolic state.

RhoA-mediated G12-G13 signaling maintains muscle stem cell quiescence and prevents stem cell loss

Multiple processes control quiescence of muscle stem cells (MuSCs), which is instrumental to guarantee long-term replenishment of the stem cell pool. Here, we describe that the G-proteins G12-G13 integrate signals from different G-protein-coupled receptors (GPCRs) to control MuSC quiescence via activation of RhoA. Comprehensive screening of GPCR ligands identified two MuSC-niche-derived factors, endothelin-3 (ET-3) and neurotensin (NT), which activate G12-G13 signaling in MuSCs. Stimulation with ET-3 or NT prevented MuSC activation, whereas pharmacological inhibition of ET-3 or NT attenuated MuSC quiescence. Inactivation of Gna12-Gna13 or Rhoa but not of Gnaq-Gna11 completely abrogated MuSC quiescence, which depleted the MuSC pool and was associated with accelerated sarcopenia during aging. Expression of constitutively active RhoA prevented exit from quiescence in Gna12-Gna13 mutant MuSCs, inhibiting cell cycle entry and differentiation via Rock and formins without affecting Rac1-dependent MuSC projections, a hallmark of quiescent MuSCs. The study uncovers a critical role of G12-G13 and RhoA signaling for active regulation of MuSC quiescence.

Farnesyltransferase inhibition overcomes oncogene-addicted non-small cell lung cancer adaptive resistance to targeted therapies

Drug-tolerance has emerged as one of the major non-genetic adaptive processes driving resistance to targeted therapy (TT) in non-small cell lung cancer (NSCLC). However, the kinetics and sequence of molecular events governing this adaptive response remain poorly understood. Here, we combine real-time monitoring of the cell-cycle dynamics and single-cell RNA sequencing in a broad panel of oncogenic addiction such as EGFR-, ALK-, BRAF- and KRAS-mutant NSCLC, treated with their corresponding TT. We identify a common path of drug adaptation, which invariably involves alveolar type 1 (AT1) differentiation and Rho-associated protein kinase (ROCK)-mediated cytoskeletal remodeling. We also isolate and characterize a rare population of early escapers, which represent the earliest resistance-initiating cells that emerge in the first hours of treatment from the AT1-like population. A phenotypic drug screen identify farnesyltransferase inhibitors (FTI) such as tipifarnib as the most effective drugs in preventing relapse to TT in vitro and in vivo in several models of oncogenic addiction, which is confirmed by genetic depletion of the farnesyltransferase. These findings pave the way for the development of treatments combining TT and FTI to effectively prevent tumor relapse in oncogene-addicted NSCLC patients.

Paeoniflorin regulates RhoA/ROCK1 and Nrf2 pathways in PDLIM1-dependent or independent manners in oxidative stressed melanocytes

BACKGROUND

The adhesive properties of vitiligo melanocytes have decreased under oxidative stress., cytoskeleton proteins can control cell adhesion. Paeoniflorin (PF) was proved to resist hydrogen peroxide (H2O2)-induced oxidative stress in melanocytes via nuclear factorE2-related factor 2 (Nrf2)/heme oxygenase-1 (HO-1) pathway.

OBJECTIVES

This study was to investigate whether PF exerts anti-oxidative effect through influencing cytoskeleton markers or potential signaling pathway.

METHODS

Human Oxidative Stress Plus array was used to identify the differentially expressed genes between H2O2 + PF group and H2O2 only group, in PIG1 and PIG3V melanocyte cell lines respectively. Western blotting was used to verify the PCR array results and to test the protein expression levels of cytoskeleton markers including Ras homolog family member A (RhoA), Rho-associated kinase 1 (ROCK1) and antioxidative marker Nrf2. Small interfering RNA was used to knock down PDZ and LIM domain 1 (PDLIM1).

RESULTS

PF increased the expressions of PDLIM1, RhoA and ROCK1 in H2O2-induced PIG1, in contrast, decreased the expressions of PDLIM1 and ROCK1 in H2O2-induced PIG3V. Knockdown of PDLIM1 increased the expressions of RhoA and Nrf2 in PF-pretreated H2O2-induced PIG1, and ROCK1 and Nrf2 in PF-pretreated H2O2-induced PIG3V.

CONCLUSIONS

PF regulates RhoA/ROCK1 and Nrf2 pathways in PDLIM1-dependent or independent manners in H2O2-induced melanocytes. In PIG1, PF promotes PDLIM1 to inhibit RhoA/ROCK1 pathway or activates Nrf2/HO-1 pathway, separately. In PIG3V, PF directly downregulates ROCK1 in PDLIM1-independent manner or upregulates Nrf2 dependent of PDLIM1.

Atypical Protein Kinase C Promotes its own Asymmetric Localisation by Phosphorylating Cdc42 in the C. elegans zygote

Atypical protein kinase C (aPKC) is a major regulator of cell polarity. Acting in conjunction with Par6, Par3 and the small GTPase Cdc42, aPKC becomes asymmetrically localised and drives the polarisation of cells. aPKC activity is crucial for its own asymmetric localisation, suggesting a hitherto unknown feedback mechanism contributing to polarisation. Here we show in the C. elegans zygote that the feedback relies on aPKC phosphorylation of Cdc42 at serine 71. The turnover of CDC-42 phosphorylation ensures optimal aPKC asymmetry and activity throughout polarisation by tuning Par6/aPKC association with Par3 and Cdc42. Moreover, turnover of Cdc42 phosphorylation regulates actomyosin cortex dynamics that are known to drive aPKC asymmetry. Given the widespread role of aPKC and Cdc42 in cell polarity, this form of self-regulation of aPKC may be vital for the robust control of polarisation in many cell types.

Kisspeptin/KISS1R Signaling Modulates Human Airway Smooth Muscle Cell Migration

Airway remodeling is a cardinal feature of asthma, associated with increased airway smooth muscle (ASM) cell mass and upregulation of extracellular matrix deposition. Exaggerated ASM cell migration contributes to excessive ASM mass. Previously, we demonstrated the alleviating role of Kp (kisspeptin) receptor (KISS1R) activation by Kp-10 in mitogen (PDGF [platelet-derived growth factor])-induced human ASM cell proliferation in vitro and airway remodeling in vivo in a mouse model of asthma. Here, we examined the mechanisms by which KISS1R activation regulates mitogen-induced ASM cell migration. KISS1R activation using Kp-10 significantly inhibited PDGF-induced ASM cell migration, further confirmed using KISS1R shRNA. Furthermore, KISS1R activation modulated F/G actin dynamics and the expression of promigration proteins like CDC42 (cell division control protein 42) and cofilin. Mechanistically, we observed reduced ASM RhoA-GTPAse with KISS1R activation. The antimigratory effect of KISS1R was abolished by PKA (protein kinase A)-inhibitory peptide. Conversely, KISS1R activation significantly increased cAMP and phosphorylation of CREB (cAMP-response element binding protein) in PDGF-exposed ASM cells. Overall, these results highlight the alleviating properties of Kp-10 in the context of airway remodeling.

Phosphoproteomics Reveals Selective Regulation of Signaling Pathways by Lysophosphatidic Acid Species in Macrophages

Lysophosphatidic acid (LPA) species, prevalent in the tumor microenvironment (TME), adversely impact various cancers. In ovarian cancer, the 18:0 and 20:4 LPA species are selectively associated with shorter relapse-free survival, indicating distinct effects on cellular signaling networks. Macrophages represent a cell type of high relevance in the TME, but the impact of LPA on these cells remains obscure. Here, we uncovered distinct LPA-species-specific responses in human monocyte-derived macrophages through unbiased phosphoproteomics, with 87 and 161 phosphosites upregulated by 20:4 and 18:0 LPA, respectively, and only 24 shared sites. Specificity was even more pronounced for downregulated phosphosites (163 versus 5 sites). Considering the high levels 20:4 LPA in the TME and its selective association with poor survival, this finding may hold significant implications. Pathway analysis pinpointed RHO/RAC1 GTPase signaling as the predominantly impacted target, including AHRGEF and DOCK guanine exchange factors, ARHGAP GTPase activating proteins, and regulatory protein kinases. Consistent with these findings, exposure to 20:4 resulted in strong alterations to the actin filament network and a consequent enhancement of macrophage migration. Moreover, 20:4 LPA induced p38 phosphorylation, a response not mirrored by 18:0 LPA, whereas the pattern for AKT was reversed. Furthermore, RNA profiling identified genes involved in cholesterol/lipid metabolism as selective targets of 20:4 LPA. These findings imply that the two LPA species cooperatively regulate different pathways to support functions essential for pro-tumorigenic macrophages within the TME. These include cellular survival via AKT activation and migration through RHO/RAC1 and p38 signaling.

Excessive endometrial PlGF- Rac1 signalling underlies endometrial cell stiffness linked to pre-eclampsia

Cell stiffness is regulated by dynamic interaction between ras-related C3 botulinum toxin substrate 1 (Rac1) and p21 protein-activated kinase 1 (PAK1) proteins, besides other biochemical and molecular regulators. In this study, we investigated how the Placental Growth Factor (PlGF) changes endometrial mechanics by modifying the actin cytoskeleton at the maternal interface. We explored the global effects of PlGF in endometrial stromal cells (EnSCs) using the concerted approach of proteomics, atomic force microscopy (AFM), and electrical impedance spectroscopy (EIS). Proteomic analysis shows PlGF upregulated RhoGTPases activating proteins and extracellular matrix organization-associated proteins in EnSCs. Rac1 and PAK1 transcript levels, activity, and actin polymerization were significantly increased with PlGF treatment. AFM further revealed an increase in cell stiffness with PlGF treatment. The additive effect of PlGF on actin polymerization was suppressed with siRNA-mediated inhibition of Rac1, PAK1, and WAVE2. Interestingly, the increase in cell stiffness by PlGF treatment was pharmacologically reversed with pravastatin, resulting in improved trophoblast cell invasion. Taken together, aberrant PlGF levels in the endometrium can contribute to an altered pre-pregnancy maternal microenvironment and offer a unifying explanation for the pathological changes observed in conditions such as pre-eclampsia (PE).

Pan-microscopic examination of monkeypox virus in trophoblasts cells reveals new insights into virions release through filopodia-like projections

Vertical transmission has been described following monkeypox virus (MPXV) infection in pregnant women. The presence of MPXV has been reported in the placenta from infected women, but whether pathogens colonize placenta remains unexplored. We identify trophoblasts as a target cell for MPXV replication. In a pan-microscopy approach, we decipher the specific infectious cycle of MPXV and inner cellular structures in trophoblasts. We identified the formation of a specialized region for viral morphogenesis and replication in placental cells. We also reported infection-induced cellular remodeling. We found that MPXV stimulates cytoskeleton reorganization with intercellular extensions for MPXV cell spreading specifically to trophoblastic cells. Altogether, the specific infectious cycle of MPXV in trophoblast cells and these protrusions that were structurally and morphologically similar to filopodia reveal new insights into the infection of MPXV.

Targeting YAP/TAZ mechanosignaling to ameliorate stiffness-induced Schlemm's canal cell pathobiology

Pathological alterations in the biomechanical properties of the Schlemm's canal (SC) inner wall endothelium and its immediate vicinity are strongly associated with ocular hypertension in glaucoma due to decreased outflow facility. Specifically, the underlying trabecular meshwork is substantially stiffer in glaucomatous eyes compared with that from normal eyes. This raises the possibility of a critical involvement of mechanotransduction processes in driving SC cell dysfunction. Yes-associated protein (YAP) has emerged as a key contributor to glaucoma pathogenesis. However, the molecular underpinnings of SC cell mechanosignaling via YAP and transcriptional coactivator with PDZ-binding motif (TAZ) in response to glaucomatous extracellular matrix (ECM) stiffening are not well understood. Using a novel biopolymer hydrogel that facilitates dynamic and reversible stiffness tuning, we investigated how ECM stiffening modulates YAP/TAZ activity in primary human SC cells, and whether disruption of YAP/TAZ mechanosignaling attenuates SC cell pathobiology and increases ex vivo outflow facility. We demonstrated that ECM stiffening drives pathologic YAP/TAZ activation and cytoskeletal reorganization in SC cells, which was fully reversible by matrix softening in a distinct time-dependent manner. Furthermore, we showed that pharmacologic or genetic disruption of YAP/TAZ mechanosignaling abrogates stiffness-induced SC cell dysfunction involving altered cytoskeletal and ECM remodeling. Finally, we found that perfusion of the clinically used, small molecule YAP/TAZ inhibitor verteporfin (without light activation) increases ex vivo outflow facility in normal mouse eyes. Collectively, our data provide new evidence for a pathologic role of aberrant YAP/TAZ mechanosignaling in SC cell dysfunction and suggest that YAP/TAZ inhibition has therapeutic value for treating ocular hypertension in glaucoma.NEW & NOTEWORTHY Pathologically altered biomechanical properties of the Schlemm's canal (SC) inner wall microenvironment were recently validated as the cause for increased outflow resistance in ocular hypertensive glaucoma. However, the involvement of specific mechanotransduction pathways in these disease processes is largely unclear. Here, we demonstrate that Yes-associated protein (YAP)/transcriptional coactivator with PDZ-binding motif (TAZ) are central regulators of glaucoma-like SC cell dysfunction in response to extracellular matrix stiffening and that targeted disruption of YAP/TAZ mechanosignaling attenuates SC cell pathobiology and enhances outflow function.

Mechanism of action of the bile acid receptor TGR5 in obesity

G protein-coupled receptors (GPCRs) are a large family of membrane protein receptors, and Takeda G protein-coupled receptor 5 (TGR5) is a member of this family. As a membrane receptor, TGR5 is widely distributed in different parts of the human body and plays a vital role in regulating metabolism, including the processes of energy consumption, weight loss and blood glucose homeostasis. Recent studies have shown that TGR5 plays an important role in glucose and lipid metabolism disorders such as fatty liver, obesity and diabetes. With the global obesity situation becoming more and more serious, a comprehensive explanation of the mechanism of TGR5 and filling the gaps in knowledge concerning clinical ligand drugs are urgently needed. In this review, we mainly explain the anti-obesity mechanism of TGR5 to promote the further study of this target, and show the electron microscope structure of TGR5 and review recent studies on TGR5 ligands to illustrate the specific binding between TGR5 receptor binding sites and ligands, which can effectively provide new ideas for ligand research and promote drug research.

Adhesion-induced cortical flows pattern E-cadherin-mediated cell contacts

Metazoan development relies on the formation and remodeling of cell-cell contacts. Dynamic reorganization of adhesion receptors and the actomyosin cell cortex in space and time plays a central role in cell-cell contact formation and maturation. Nevertheless, how this process is mechanistically achieved when new contacts are formed remains unclear. Here, by building a biomimetic assay composed of progenitor cells adhering to supported lipid bilayers functionalized with E-cadherin ectodomains, we show that cortical F-actin flows, driven by the depletion of myosin-2 at the cell contact center, mediate the dynamic reorganization of adhesion receptors and cell cortex at the contact. E-cadherin-dependent downregulation of the small GTPase RhoA at the forming contact leads to both a depletion of myosin-2 and a decrease of F-actin at the contact center. At the contact rim, in contrast, myosin-2 becomes enriched by the retraction of bleb-like protrusions, resulting in a cortical tension gradient from the contact rim to its center. This tension gradient, in turn, triggers centrifugal F-actin flows, leading to further accumulation of F-actin at the contact rim and the progressive redistribution of E-cadherin from the contact center to the rim. Eventually, this combination of actomyosin downregulation and flows at the contact determines the characteristic molecular organization, with E-cadherin and F-actin accumulating at the contact rim, where they are needed to mechanically link the contractile cortices of the adhering cells.

SH2 domain protein E and ABL signaling regulate blood vessel size

Blood vessels in different vascular beds vary in size, which is essential for their function and fluid flow along the vascular network. Molecular mechanisms involved in the formation of a vascular lumen of appropriate size, or tubulogenesis, are still only partially understood. Src homology 2 domain containing E (She) protein was previously identified in a screen for proteins that interact with Abelson (Abl)-kinase. However, its biological role has remained unknown. Here we demonstrate that She and Abl signaling regulate vessel size in zebrafish embryos and human endothelial cell culture. Zebrafish she mutants displayed increased endothelial cell number and enlarged lumen size of the dorsal aorta (DA) and defects in blood flow, eventually leading to the DA collapse. Vascular endothelial specific overexpression of she resulted in a reduced diameter of the DA, which correlated with the reduced arterial cell number and lower endothelial cell proliferation. Chemical inhibition of Abl signaling in zebrafish embryos caused a similar reduction in the DA diameter and alleviated the she mutant phenotype, suggesting that She acts as a negative regulator of Abl signaling. Enlargement of the DA size in she mutants correlated with an increased endothelial expression of claudin 5a (cldn5a), which encodes a protein enriched in tight junctions. Inhibition of cldn5a expression partially rescued the enlarged DA in she mutants, suggesting that She regulates DA size, in part, by promoting cldn5a expression. SHE knockdown in human endothelial umbilical vein cells resulted in a similar increase in the diameter of vascular tubes, and also increased phosphorylation of a known ABL downstream effector CRKL. These results argue that SHE functions as an evolutionarily conserved inhibitor of ABL signaling and regulates vessel and lumen size during vascular tubulogenesis.

RhoA Is a Crucial Regulator of Myoblast Fusion

Satellite cells (SCs) are adult muscle stem cells that are mobilized when muscle homeostasis is perturbed. Here we show that RhoA in SCs is indispensable to have correct muscle regeneration and hypertrophy. In particular, the absence of RhoA in SCs prevents a correct SC fusion both to other RhoA-deleted SCs (regeneration context) and to growing control myofibers (hypertrophy context). We demonstrated that RhoA is dispensable for SCs proliferation and differentiation; however, RhoA-deleted SCs have an inefficient movement even if their cytoskeleton assembly is not altered. Proliferative myoblast and differentiated myotubes without RhoA display a decreased expression of Chordin, suggesting a crosstalk between these genes for myoblast fusion regulation. These findings demonstrate the importance of RhoA in SC fusion regulation and its requirement to achieve an efficient skeletal muscle homeostasis restoration.

Centrosome amplification promotes cell invasion via cell-cell contact disruption and Rap-1 activation

Centrosome amplification (CA) is a prominent feature of human cancers linked to tumorigenesis in vivo. Here, we report mechanistic contributions of CA induction alone to tumour architecture and extracellular matrix (ECM) remodelling. CA induction in non-tumorigenic breast cells MCF10A causes cell migration and invasion, with underlying disruption of epithelial cell-cell junction integrity and dysregulation of expression and subcellular localisation of cell junction proteins. CA also elevates expression of integrin β-3, its binding partner fibronectin-1 and matrix metalloproteinase enzymes, promoting cell-ECM attachment, ECM degradation, and a migratory and invasive cell phenotype. Using a chicken embryo xenograft model for in vivo validation, we show that CA-induced (+CA) MCF10A cells invade into the chick mesodermal layer, with inflammatory cell infiltration and marked focal reactions between chorioallantoic membrane and cell graft. We also demonstrate a key role of small GTPase Rap-1 signalling through inhibition using GGTI-298, which blocked various CA-induced effects. These insights reveal that in normal cells, CA induction alone (without additional oncogenic alterations) is sufficient to confer early pro-tumorigenic changes within days, acting through Rap-1-dependent signalling to alter cell-cell contacts and ECM disruption.

HIV-1 diverts cortical actin for particle assembly and release

Enveloped viruses assemble and bud from the host cell membranes. Any role of cortical actin in these processes have often been a source of debate. Here, we assessed if cortical actin was involved in HIV-1 assembly in infected CD4 T lymphocytes. Our results show that preventing actin branching not only increases HIV-1 particle release but also the number of individual HIV-1 Gag assembly clusters at the T cell plasma membrane. Indeed, in infected T lymphocytes and in in vitro quantitative model systems, we show that HIV-1 Gag protein prefers areas deficient in F-actin for assembling. Finally, we found that the host factor Arpin, an inhibitor of Arp2/3 branched actin, is recruited at the membrane of infected T cells and it can associate with the viral Gag protein. Altogether, our data show that, for virus assembly and particle release, HIV-1 prefers low density of cortical actin and may favor local actin debranching by subverting Arpin.

Neuroligin 2 governs synaptic morphology and function through RACK1-cofilin signaling in Drosophila

Neuroligins are transmembrane cell adhesion proteins well-known for their genetic links to autism spectrum disorders. Neuroligins can function by regulating the actin cytoskeleton, however the factors and mechanisms involved are still largely unknown. Here, using the Drosophila neuromuscular junction as a model, we reveal that F-Actin assembly at the Drosophila NMJ is controlled through Cofilin signaling mediated by an interaction between DNlg2 and RACK1, factors not previously known to work together. The deletion of DNlg2 displays disrupted RACK1-Cofilin signaling pathway with diminished actin cytoskeleton proteo-stasis at the terminal of the NMJ, aberrant NMJ structure, reduced synaptic transmission, and abnormal locomotion at the third-instar larval stage. Overexpression of wildtype and activated Cofilin in muscles are sufficient to rescue the morphological and physiological defects in dnlg2 mutants, while inactivated Cofilin is not. Since the DNlg2 paralog DNlg1 is known to regulate F-actin assembly mainly via a specific interaction with WAVE complex, our present work suggests that the orchestration of F-actin by Neuroligins is a diverse and complex process critical for neural connectivity.

Volumetric Compression Shifts Rho GTPase Balance and Induces Mechanobiological Cell State Transition

During development and disease progression, cells are subject to osmotic and mechanical stresses that modulate cell volume, which fundamentally influences cell homeostasis and has been linked to a variety of cellular functions. It is not well understood how the mechanobiological state of cells is programmed by the interplay of intracellular organization and complex extracellular mechanics when stimulated by cell volume modulation. Here, by controlling cell volume via osmotic pressure, we evaluate physical phenotypes (including cell shape, morphodynamics, traction force, and extracellular matrix (ECM) remodeling) and molecular signaling (YAP), and we uncover fundamental transitions in active biophysical states. We demonstrate that volumetric compression shifts the ratiometric balance of Rho GTPase activities, thereby altering mechanosensing and cytoskeletal organization in a reversible manner. Specifically, volumetric compression controls cell spreading, adhesion formation, and YAP nuclear translocation, while maintaining cell contractile activity. Furthermore, we show that on physiologically relevant fibrillar collagen I matrices, which are highly non-elastic, cells exhibit additional modes of cell volume-dependent mechanosensing that are not observable on elastic substrates. Notably, volumetric compression regulates the dynamics of cell-ECM interactions and irreversible ECM remodeling via Rac-directed protrusion dynamics, at both the single-cell level and the multicellular level. Our findings support that cell volume is a master biophysical regulator and reveal its roles in cell mechanical state transition, cell-ECM interactions, and biophysical tissue programming.

The emerging role of Piezo1 channels in skeletal muscle physiology

Piezo1 channels are mechanically activated (MA) cation channels that are involved in sensing of various mechanical perturbations, such as membrane stretch and shear stress, and play a crucial role in cell mechanotransduction. In response to mechanical stimuli, these channels open up and allow cations to travel into the cell and induce biochemical reactions that can change the cell's metabolism and function. Skeletal muscle cells/fibers inherently depend upon mechanical cues in the form of fluid shear stress and contractions (physical exercise). For example, an exposure of skeletal muscles to chronic mechanical loading leads to increased anabolism and fiber hypertrophy, while prolonged mechanical unloading results in muscle atrophy. MA Piezo1 channels have recently emerged as key mechanosensors that are capable of linking mechanical signals and intramuscular signaling in skeletal muscle cells/fibers. This review will summarize the emerging role of Piezo1 channels in the development and regeneration of skeletal muscle tissue as well as in the regulation of skeletal muscle atrophy. In addition, an overview of potential Piezo1-related signaling pathways underlying anabolic and catabolic processes will be provided. A better understanding of Piezo1's role in skeletal muscle mechanotransduction may represent an important basis for the development of therapeutic strategies for maintaining muscle functions under disuse conditions and in some disease states.

Serial and multi-level proteome analysis for microscale protein samples

Post-translational modifications (PTMs), such as phosphorylation and ubiquitination, play key roles in signal transduction and protein homeostasis. The crosstalk of PTMs greatly expands the components of proteome and protein functions. Multi-level proteome analysis, which involves proteome investigations of total lysate and PTMs in this context, provides a comprehensive approach to explore the PTM crosstalk of a biological system under diverse disturbances. However, multi-level proteome practice remains technically challenging. Here we intended to build a strategy for multi-level proteome analysis, in which we focus on the serial profiling the total proteome, ubiquitinome and phosphoproteome from the microscale of starting material. We started by evaluating five common lysis buffers and found that the sodium deoxycholate buffer provided the best overall performance. We then developed an approach for serial enrichment and profiling of the multi-level proteome. To expand the depth of identification, we customized the variable windows to perform data-independent acquisition (DIA) sequencing for each proteome. In total, we identified 6465 proteins, ∼20,000 GlyGly sites (class 1), and ∼ 19,000 phosphosites (class 1) sequentially using 1 mg of HeLa digest by three DIA measurements. We applied this strategy to analyze MG132-treated HeLa cells and observed the crosstalk between ubiquitination and phosphorylation. Our method can be referenced for other multi-level proteome studies with microscale samples. SIGNIFICANCE: Lysis buffer containing sodium deoxycholate provided the best overall performance in multi-level proteome analysis. One step of ubiquitination enrichment before phosphorylation enrichment does not reduce the reproducibility of phosphoproteome. Customized isolation windows were established for DIA analysis on each level of proteome. Combined the serial enrichment approach and the customized single-shot DIA method enabled the multi-level proteome of microscale protein samples.

Targeting YAP mechanosignaling to ameliorate stiffness-induced Schlemm's canal cell pathobiology

Pathologic alterations in the biomechanical properties of the Schlemm's canal (SC) inner wall endothelium and its immediate vicinity are strongly associated with ocular hypertension in glaucoma due to decreased outflow facility. Specifically, the underlying trabecular meshwork is substantially stiffer in glaucomatous eyes compared to that from normal eyes. This raises the possibility of a critical involvement of mechanotransduction processes in driving SC cell dysfunction. Yes-associated protein (YAP) has emerged as a key contributor to glaucoma pathogenesis. However, the molecular underpinnings of SC cell YAP mechanosignaling in response to glaucomatous extracellular matrix (ECM) stiffening are not well understood. Using a novel biopolymer hydrogel that facilitates dynamic and reversible stiffness tuning, we investigated how ECM stiffening modulates YAP activity in primary human SC cells, and whether disruption of YAP mechanosignaling attenuates SC cell pathobiology and increases ex vivo outflow facility. We demonstrated that ECM stiffening drives pathologic YAP activation and cytoskeletal reorganization in SC cells, which was fully reversible by matrix softening in a distinct time-dependent manner. Furthermore, we showed that pharmacologic or genetic disruption of YAP mechanosignaling abrogates stiffness-induced SC cell dysfunction involving altered cytoskeletal and ECM remodeling. Lastly, we found that perfusion of the clinically-used, small molecule YAP inhibitor verteporfin (without light activation) increases ex vivo outflow facility in normal mouse eyes. Collectively, our data provide new evidence for a pathologic role of aberrant YAP mechanosignaling in SC cell dysfunction and suggest that YAP inhibition has therapeutic value for treating ocular hypertension in glaucoma.

Yes-associated protein regulates cortical actin architecture and dynamics through intracellular translocation of Rho GTPase-activating protein 18

Yes-associated protein (YAP) is a transcriptional co-activator that controls the transcription of target genes and modulates the structures of various cytoskeletal architecture as mechanical responses. Although it has been known that YAP regulates actin-regulatory proteins, the detailed molecular mechanism of how they control and coordinate intracellular actin architecture remains elusive. Herein, we aimed to examine the structure and dynamics of intracellular actin architecture from molecular to cellular scales in normal and YAP-knockout (YAP-KO) cells utilizing high-speed atomic force microscopy (HS-AFM) for live-cell imaging and other microscope-based mechanical manipulation and measurement techniques. YAP-KO Madin-Darby canine kidney cells had a higher density and turnover of actin filaments in the cell cortex and a higher elastic modulus. Laser aberration assay demonstrated that YAP-KO cells were more resistant to damage than normal cells. We also found that Rho GTPase-activating protein 18 (ARHGAP18), a downstream factor of YAP, translocated from the cortex to the edge of sparsely cultured YAP-KO cells. It resulted in high RhoA activity and promotion of actin polymerization in the cell cortex and their reductions at the edge. HS-AFM imaging of live cell edge and a cell-migration assay demonstrated lower membrane dynamics and motility of YAP-KO cells than those of normal cells, suggesting lower actin dynamics at the edge. Together, these results demonstrate that a YAP-dependent pathway changes the intracellular distribution of RhoGAP and modulates actin dynamics in different parts of the cell, providing a mechanistic insight into how a mechano-sensitive transcription cofactor regulates multiple intracellular actin architecture and coordinates mechano-responses.

Epidermal growth factor receptor promotes infectious spleen and kidney necrosis virus invasion via PI3K-Akt signaling pathway

Infectious spleen and kidney necrosis virus disease (ISKNVD) caused significant economic losses to the fishery industry. Epidermal growth factor receptor (EGFR), phosphatidylinositide 3-kinase (PI3K) played an important role in ISKNV invasion. However, the molecular regulatory mechanisms among EGFR, PI3K-Akt, and ISKNV invasion are not clear. In this study, ISKNV infection rapidly induced EGFR activation. While, EGFR activation promoted virus entry, but EGFR inhibitors and specific RNA (siRNA) decreased virus invasion. The PI3K-Akt as downstream signalling of EGFR was activated upon ISKNV infection. Consistent with the trends of EGFR, Akt activation increased ISKNV entry into cells, Akt inhibition by specific inhibitor or siRNA decreased ISKNV invasion. Akt silencing combination with EGFR activation showed that EGFR activation regulation ISKNV invasion is required for activation of the Akt signalling pathway. Those data demonstrated that ISKNV-induced EGFR activation positively regulated virus invasion by PI3K-Akt pathway and provided a better understanding of the mechanism of EGFR-PI3K-Akt involved in ISKNV invasion.

SH2 domain protein E (SHE) and ABL signaling regulate blood vessel size

Blood vessels in different vascular beds vary in lumen diameter, which is essential for their function and fluid flow along the vascular network. Molecular mechanisms involved in the formation of a vascular lumen of appropriate size, or tubulogenesis, are still only partially understood. Src homology 2 domain containing E (She) protein was previously identified in a screen for proteins that interact with Abelson (Abl)-kinase. However, its biological role has remained unknown. Here we demonstrate that She and Abl signaling regulate vascular lumen size in zebrafish embryos and human endothelial cell culture. Zebrafish she mutants displayed increased endothelial cell number and enlarged lumen size of the dorsal aorta (DA) and defects in blood flow. Vascular endothelial specific overexpression of she resulted in a reduced diameter of the DA lumen, which correlated with the reduced arterial cell number and lower endothelial cell proliferation. Chemical inhibition of Abl signaling in zebrafish embryos caused a similar reduction in the DA diameter and alleviated the she mutant phenotype, suggesting that She acts as a negative regulator of Abl signaling. Enlargement of the DA lumen in she mutants correlated with an increased endothelial expression of claudin 5a and 5b (cldn5a / cldn5b), which encode proteins enriched in tight junctions. Inhibition of cldn5a expression partially rescued the enlarged DA in she mutants, suggesting that She regulates DA lumen size, in part, by promoting cldn5a expression. SHE knockdown in human endothelial umbilical vein cells resulted in a similar increase in the diameter of vascular tubes, and also increased phosphorylation of a known ABL downstream effector CRKL. These results argue that SHE functions as an evolutionarily conserved inhibitor of ABL signaling and regulates lumen size during vascular tubulogenesis.

Eosinophil: An innate immune cell with anti-filarial vaccine and biomarker potential

Background

Filarial infections continue to pose a great challenge in endemic countries. One of the central goals in the fight against human filarial infections is the development of strategies that will lead to the inhibition of microfilariae (mf) transmission. Keeping mf under a certain threshold within endemic populations will stop transmission and eliminate the infection.

Method

A narrative review was carried out to identify the possibilities and limitations of exploring the use of eosinophil responses as an anti-filarial vaccine, and biomarker for the detection of filarial infections. An extensive literature search was performed in online scientific databases including PubMed Central, PubMed, BioMed Central, with the use of predefined search terms.

Results

A better understanding of the parasite-host interactions will lead to the development of improved and better treatment or vaccine strategies that could eliminate filariasis as soon as possible. Highlighted in this review is the explorative use of eosinophil-producing CLC/Galectin-10 as a potential biomarker for filarial infections. Also discussed are some genes, and pathways involved in eosinophil recruitments that could be explored for anti-filarial vaccine development.

Conclusion

In this short communication, we discuss how eosinophil-regulated genes, pathways, and networks could be critical in providing more information on how reliably a front-line immune player could be exploited for anti-filarial vaccine development and early infection biomarker.

Intracellular mechanics and TBX3 expression jointly dictate the spreading mode of melanoma cells in 3D environments

Cell stiffness and T-box transcription factor 3 (TBX3) expression have been identified as biomarkers of melanoma metastasis in 2D environments. This study aimed to determine how mechanical and biochemical properties of melanoma cells change during cluster formation in 3D environments. Vertical growth phase (VGP) and metastatic (MET) melanoma cells were embedded in 3D collagen matrices of 2 and 4 mg/ml collagen concentrations, representing low and high matrix stiffness. Mitochondrial fluctuation, intracellular stiffness, and TBX3 expression were quantified before and during cluster formation. In isolated cells, mitochondrial fluctuation decreased and intracellular stiffness increased with increase in disease stage from VGP to MET and increased matrix stiffness. TBX3 was highly expressed in soft matrices but diminished in stiff matrices for VGP and MET cells. Cluster formation of VGP cells was excessive in soft matrices but limited in stiff matrices, whereas for MET cells it was limited in soft and stiff matrices. In soft matrices, VGP cells did not change the intracellular properties, whereas MET cells exhibited increased mitochondrial fluctuation and decreased TBX3 expression. In stiff matrices, mitochondrial fluctuation and TBX3 expression increased in VGP and MET, and intracellular stiffness increased in VGP but decreased in MET cells. The findings suggest that soft extracellular environments are more favourable for tumour growth, and high TBX3 levels mediate collective cell migration and tumour growth in the earlier VGP disease stage but play a lesser role in the later metastatic stage of melanoma.

RNAi screen in the Drosophila wing of genes encoding proteins related to cytoskeleton organization and cell division

Cell division and cytoskeleton organization are fundamental processes participating in the development of Drosophila imaginal discs. In this manuscript we describe the phenotypes in the adult fly wing generated by knockdowns of 85% of Drosophila genes encoding proteins likely related to the regulation of cell division and cytoskeleton organization. We also compile a molecular classification of these proteins into classes that describe their expected or known main biochemical characteristics, as well as mRNA expression in the wing disc and likely protein subcellular localization for a subset of these genes. Finally, we analyze in more detail one protein family of cytoskeleton genes (Arp2/3 complex), and define the consequences of interfering with cell division for wing growth and patterning.

The Proteome of Circulating Large Extracellular Vesicles in Diabetes and Hypertension

Hypertension and diabetes induce vascular injury through processes that are not fully understood. Changes in extracellular vesicle (EV) composition could provide novel insights. Here, we examined the protein composition of circulating EVs from hypertensive, diabetic and healthy mice. EVs were isolated from transgenic mice overexpressing human renin in the liver (TtRhRen, hypertensive), OVE26 type 1 diabetic mice and wild-type (WT) mice. Protein content was analyzed using liquid chromatography-mass spectrometry. We identified 544 independent proteins, of which 408 were found in all groups, 34 were exclusive to WT, 16 were exclusive to OVE26 and 5 were exclusive to TTRhRen mice. Amongst the differentially expressed proteins, haptoglobin (HPT) was upregulated and ankyrin-1 (ANK1) was downregulated in OVE26 and TtRhRen mice compared with WT controls. Conversely, TSP4 and Co3A1 were upregulated and SAA4 was downregulated exclusively in diabetic mice; and PPN was upregulated and SPTB1 and SPTA1 were downregulated in hypertensive mice, compared to WT mice. Ingenuity pathway analysis identified enrichment in proteins associated with SNARE signaling, the complement system and NAD homeostasis in EVs from diabetic mice. Conversely, in EVs from hypertensive mice, there was enrichment in semaphroin and Rho signaling. Further analysis of these changes may improve understanding of vascular injury in hypertension and diabetes.

The Role of PKGIα and AMPK Signaling Interplay in the Regulation of Albumin Permeability in Cultured Rat Podocytes

The permeability of the glomerular filtration barrier (GFB) is mainly regulated by podocytes and their foot processes. Protein kinase G type Iα (PKGIα) and adenosine monophosphate-dependent kinase (AMPK) affect the contractile apparatus of podocytes and influence the permeability of the GFB. Therefore, we studied the interplay between PKGIα and AMPK in cultured rat podocytes. The glomerular permeability to albumin and transmembrane FITC-albumin flux decreased in the presence of AMPK activators and increased in the presence of PKG activators. The knockdown of PKGIα or AMPK with small-interfering RNA (siRNA) revealed a mutual interaction between PKGIα and AMPK and influenced podocyte permeability to albumin. Moreover, PKGIα siRNA activated the AMPK-dependent signaling pathway. AMPKα2 siRNA increased basal levels of phosphorylated myosin phosphate target subunit 1 and decreased the phosphorylation of myosin light chain 2. Podocytes that were treated with AMPK or PKG activators were characterized by the different organization of actin filaments within the cell. Our findings suggest that mutual interactions between PKGIα and AMPKα2 regulate the contractile apparatus and permeability of the podocyte monolayer to albumin. Understanding this newly identified molecular mechanism in podocytes provides further insights into the pathogenesis of glomerular disease and novel therapeutic targets for glomerulopathies.