Actin cytoskeleton dynamics and the cell division cycle

Metabolomics reveals the toxicological effects of penconazole (PEN) in mice oocyte

Penconazole (PEN) is a widely employed agent in the mitigation of fungal infestations, and recent research shows that water exposure and subsequent bioaccumulation within the food web elicits inflammatory responses in certain vital organs. Nonetheless, the fundamental pathways through which PEN impacts the quality of oocytes remain inadequately elucidated to date. We gavaged mouse with PEN (2.5 mg / kg) at the same time for 10 consecutive days and discovered a precipitous decline in the developmental proportion of oocytes collected from mice exposed to PEN. Metabolomic profiling revealed significant perturbations in key metabolic pathways, including oxidative phosphorylation and longevity regulation, with nicotinamide adenine dinucleotide (NAD) being markedly downregulated in PEN-exposed oocytes. Subsequent evaluations indicated a compromised state in both the cytoplasmic and nuclear maturation processes. This phenomenon stems from heightened levels of reactive oxygen species coupled with diminished mitochondrial functionality. Furthermore, Annexin-V signaling suggested that PEN triggered an apoptotic response in the oocytes. Our metabolomic findings underscore the central role of NAD depletion in mediating PEN-induced toxicity, linking mitochondrial dysfunction and oxidative stress to impaired oocyte quality. Overall, we recommend that females who are preparing for pregnancy in areas with higher risks of PEN exposure should supplement with Nicotinamide mononucleotide (NMN) to protect the quality of their oocytes.

Long noncoding RNA semaphorin 6A-antisense RNA 1 reduces hepatocellular carcinoma by promoting semaphorin 6A mRNA degradation

BACKGROUND

Hepatocellular carcinoma (HCC) is a prevalent malignant tumor with a poor prognosis, which is often associated with chronic hepatitis B virus infection in China. Our previous study has shown that long non-coding RNA semaphorin 6A-antisense RNA 1 (SEMA6A-AS1) was significantly downregulated in hepatitis B virus-related HCC and associated with poor prognosis.

AIM

To explore the underlying mechanism of SEMA6A-AS1 in HCC progression.

METHODS

The expression levels of SEMA6A-AS1 and SEMA6A were detected using quantitative polymerase chain reaction, immunohistochemistry and Western blot. A growth curve, colony formation, wound-healing and transwell (with or without Matrigel) assays were respectively performed to assess the proliferation, migration and invasion abilities of HCC cells. Cell cycle and apoptosis assays were performed by flow cytometry. To investigate the potential mechanism underpinning SEMA6A-AS1, we utilized tagged RNA affinity purification, dual luciferase reporter assay and immunofluorescence.

RESULTS

Downregulation of SEMA6A-AS1 in HCC was negatively correlated with SEMA6A protein expression. SEMA6A was upregulated in HCC and correlated with high alpha-fetoprotein level, high Edmondson-Steiner grade and poor prognosis. SEMA6A-AS1 significantly inhibited the proliferation, migration and invasion of HCC cells by combining with SEMA6A mRNA and promoting its degradation. SEMA6A protein promoted the proliferation, migration and invasion of HCC cells by regulating the actin cytoskeleton.

CONCLUSION

Our findings suggest that SEMA6A-AS1 can inhibit HCC progression through decreasing SEMA6A expression by promoting its mRNA degradation. SEMA6A-AS1 may be a prognostic biomarker and therapeutic target for HCC.

Regulatory mechanisms of connexin26

Connexins are essential for cellular communication and play a critical role in various physiological processes, including hearing. Connexin26 (Cx26), encoded by the GJB2 gene, is a key component of cochlear gap junctions and is vital for potassium recycling and ATP release-both of which are vital for auditory function. Mutations in GJB2 are the primary cause of sensorineural hearing loss. However, the phenotypic variability observed in individuals with the same mutation suggests the involvement of other complex regulatory factors. While the regulatory mechanisms of Connexin43 have been extensively studied, research on the mechanisms of Cx26 remains limited. This review summarizes the reported regulatory mechanisms of GJB2 from multiple perspectives, both pre- and post-transcription, in an effort to explore ways to regulate connexin expression and provide new insights into gene therapy for diseases caused by alterations in connexin levels.

Electrical impedance sensing in stem cell research: Insights, applications, and future directions

The exceptional differentiation abilities of stem cells make them ideal candidates for cell replacement therapies. Considering their great potential, researchers should understand how stem cells interact with other cell types. The production of high-quality differentiated cells is crucial for favorable treatment and makes them an ideal choice for clinical applications. Label-free stem cell monitoring approaches are anticipated to be more effective in this context, as they ensure quality of differentiation while preserving the therapeutic potential. Electric cell-substrate impedance sensing (ECIS) is a nonintrusive technique that enables cell quantification through continuous monitoring of adherent cell behavior using electronic transcellular impedance measurements. This technique also facilitates the study of cell growth, motility, differentiation, drug effects, and cell barrier functions. Therefore, numerous studies have identified ECIS as an effective method for monitoring stem cell quality and differentiation. In this review, we discuss the current understanding of ECIS's achievements in examining cell behaviors and the potential applications of ECIS arrays in preclinical stem cell research. Moreover, we highlight our present knowledge concerning ECIS's contributions in examining cell behaviors and speculate about the future uses of ECIS arrays in preclinical stem cell research. This review also aims to stimulate research on electrochemical biosensors for future applications in regenerative medicine.

Emerging functions of Plakophilin 4 in the control of cell contact dynamics

Plakophilin 4 (PKP4, also called p0071) is a unique armadillo family protein localized at adherens junctions that acts as a scaffold protein capable of clustering cadherins. PKP4 also regulates cadherin recycling which is vital to enable junction dynamics. In addition, PKP4 controls the mechanical properties of cells by regulating actin filament organization through small Rho-GTPases. In this setting, PKP4 controls the localization and activity of specific guanine exchange factors (GEFs) and of their opponents, the GTPase activating proteins (GAPs). Through the formation of multiprotein complexes with Rho-GTPases, their regulators and their effectors, PKP4 controls the spatio-temporal activity of Rho signaling to regulate cell adhesion and cell mechanics. In keratinocytes, PKP4 prevents differentiation and at the same time dampens proliferation. This is, in part achieved through an interaction with the Hippo pathway, which controls the activity of the transcriptional co-factors YAP and TAZ. In a feedback loop, YAP/TAZ modulate PKP4 localization and function. Here, we review the various functions of PKP4 in cell signaling, cell mechanics, cell adhesion and growth control. We discuss how these functions converge in the regulation of cell adhesion dynamics to allow cells to adapt to their changing environment and enable proliferation, delamination but, at the same time, guarantee cell barrier function.

Mebendazole Exerts Anticancer Activity in Ovarian Cancer Cell Lines via Novel Girdin-Mediated AKT/IKKα/β/NF-κB Signaling Axis

Mebendazole (MBZ), a benzimidazole anthelmintic and cytoskeleton-disrupting compound, exhibits antitumor properties; however, its action on ovarian cancer (OC) is not clearly understood. This study evaluates the effect of MBZ on OC cell lines OVCAR3 and OAW42, focusing on cell proliferation, migration, invasion, and cancer stemness. The underlying mechanisms, including cytoskeletal disruption, epithelial-mesenchymal transition (EMT), and signaling pathways, were explored. MBZ inhibited OVCAR3 and OAW42 cell proliferation in a dose- and time-dependent manner. Additionally, MBZ significantly impedes migration, spheroid invasion, colony formation, and stemness. In addition, it reduced actin polymerization and down-regulated CSC markers (e.g., CD24, CD44, EpCAM). Moreover, MBZ suppressed MMP-9 activity and inhibited the EMT marker as judged by decreased N-Cadherin and Vimentin and increased E-Cadherin. Furthermore, MBZ induced G2/M cell cycle arrest by modulating Cyclin B1, CDC25C, and WEE1. Also, it triggered apoptosis by disrupting mitochondrial membrane potential. Mechanistic studies revealed a significant downregulation of Girdin, an Akt modulator, along with reduced p-Akt, p-IKKα/β, and p-NF-κB, indicating MBZ's novel mechanism of action through the Girdin-mediated Akt/IKKα/β/NF-κB signaling axis. Thus, by targeting Girdin, MBZ presents a promising repurposed therapeutic strategy to inhibit cancer cell proliferation and metastasis in ovarian cancer.

Ribose-induced advanced glycation end products reduce the lifespan in Drosophila melanogaster by changing the redox state and down-regulating the Sirtuin genes

Advanced Glycation End (AGE) products are one such factor that accumulates during aging and age-related diseases. However, how exogenous AGE compounds cause aging is an area that needs to be explored. Specifically, how an organ undergoes aging and aging-related phenomena that need further investigation. The intestine is the most exposed area to food substances. How AGEs affect the intestine in terms of aging need to be explored. Drosophila melanogaster, a well-known model organism, is used to decode aging and age-associated phenomena. In this study, we fed Ribose induced Advanced Glycation End products (Rib-AGE) to D. melanogaster to study the aging mechanism. The Rib-AGE-induced aging was checked in Drosophila. We found a series of changes in Rib-AGE-fed flies. Reactive oxygen species (ROS) and nitric oxide species (NOs) were higher in the Rib-AGE-fed flies, and the antioxidant level was lower. The intestinal permeability was altered. The microorganism load was higher inside the gut. The structural arrangement of the gut's microfilament was found to be damaged, and the nuclear shape was found to be irregular. Cell death within the gut was elevated in comparison to control. The food intake was found to be reduced. The relative mRNA expression of the Sirtuin 2 and Sirtuin 6 gene of D. melanogaster was downregulated in Rib-AGE-fed flies compared to the control. All these findings strongly suggest that Rib-AGE accelerates aging and age-related disorders in D. melanogaster.

Incarvine C and its analogues inhibit the formation of cell cytoskeleton by targeting Rac1

Ras-related C3 botulinum toxin substrate 1 (Rac1) has emerged as a key regulator in the treatment of cancer metastasis because of its involvement in the formation of cell plate pseudopods and effects on cell migration. In this study, we found that incarvine C, a natural product isolated from Incarvillea sinensis, and its seven analogues exhibited antitumour activity by inhibiting cell cytoskeleton formation, with moderate cytotoxicity. Accordingly, these compounds inhibited the cytoskeleton-mediated migration and invasion of MDA-MB-231 cells, with inhibition rates ranging from 37.30 % to 69.72 % and 51.27 % to 70.90 % in vitro, respectively. Moreover, they induced G2/M phase cell cycle arrest in MDA-MB-231 cells. A pull-down assay revealed that the interaction between Rac1 and its downstream effector protein PAK1 was inhibited by these compounds and that the compound Ano-6 exhibited substantial activity, with an inhibition rate of more than 90 %. Molecular docking showed that incarvine C and its analogues could bind to the nucleotide-binding pocket of Rac1, maintaining high levels of inactivated Rac1. As Ano-6 exhibited significant activity in vitro, its anti-cancer activity was tested in vivo. Four weeks of oral treatment with Ano-6 was well-tolerated in mice, and it induced a potential anti-tumour response in xenografts of MDA-MB-231 cells. Further studies demonstrated that Ano-6 was enriched in tumour tissues after 2 h of administration and induced an increase in the number of dead tumour cells. In summary, these findings not only reveal the mechanism of incarvine C but also provide a new molecular template for Rac1 inhibitors and identify a promising candidate for breast cancer treatment.

Differential Regulation of Hemichannels and Gap Junction Channels by RhoA GTPase and Actin Cytoskeleton: A Comparative Analysis of Cx43 and Cx26

Connexins (Cxs) are transmembrane proteins that assemble into gap junction channels (GJCs) and hemichannels (HCs). Previous researches support the involvement of Rho GTPases and actin microfilaments in the trafficking of Cxs, formation of GJCs plaques, and regulation of channel activity. Nonetheless, it remains uncertain whether distinct types of Cxs HCs and GJCs respond differently to Rho GTPases or changes in actin polymerization/depolymerization dynamics. Our investigation revealed that inhibiting RhoA, a small GTPase that controls actin polymerization, or disrupting actin microfilaments with cytochalasin B (Cyto-B), resulted in reduced GJCs plaque size at appositional membranes and increased transport of HCs to non-appositional plasma membrane regions. Notably, these effects were consistent across different Cx types, since Cx26 and Cx43 exhibited similar responses, despite having distinct trafficking routes to the plasma membrane. Functional assessments showed that RhoA inhibition and actin depolymerization decreased the activity of Cx43 GJCs while significantly increasing HC activity. However, the functional status of GJCs and HCs composed of Cx26 remained unaffected. These results support the hypothesis that RhoA, through its control of the actin cytoskeleton, facilitates the transport of HCs to appositional cell membranes for GJCs formation while simultaneously limiting the positioning of free HCs at non-appositional cell membranes, independently of Cx type. This dynamic regulation promotes intercellular communications and reduces non-selective plasma membrane permeability through a Cx-type dependent mechanism, whereby the activity of Cx43 HCs and GJCs are differentially affected but Cx26 channels remain unchanged.

Conditional deficiency of Rho-associated kinases disrupts endothelial cell junctions and impairs respiratory function in adult mice

The Ras homology (Rho) family of GTPases serves various functions, including promotion of cell migration, adhesion, and transcription, through activation of effector molecule targets. One such pair of effectors, the Rho-associated coiled-coil kinases (ROCK1 and ROCK2), induce reorganization of actin cytoskeleton and focal adhesion through substrate phosphorylation. Studies on ROCK knockout mice have confirmed that ROCK proteins are essential for embryonic development, but their physiological functions in adult mice remain unknown. In this study, we aimed to examine the roles of ROCK1 and ROCK2 proteins in normal adult mice. Tamoxifen (TAM)-inducible ROCK1 and ROCK2 single and double knockout mice (ROCK1flox/flox and/or ROCK2flox/flox;Ubc-CreERT2) were generated and administered a 5-day course of TAM. No deaths occurred in either of the single knockout strains, whereas all of the ROCK1/ROCK2 double conditional knockout mice (DcKO) had died by Day 11 following the TAM course. DcKO mice exhibited increased lung tissue vascular permeability, thickening of alveolar walls, and a decrease in percutaneous oxygen saturation compared with noninducible ROCK1/ROCK2 double-floxed control mice. On Day 3 post-TAM, there was a decrease in phalloidin staining in the lungs in DcKO mice. On Day 5 post-TAM, immunohistochemical analysis also revealed reduced staining for vascular endothelial (VE)-cadherin, β-catenin, and p120-catenin at cell-cell contact sites in vascular endothelial cells in DcKO mice. Additionally, VE-cadherin/β-catenin complexes were decreased in DcKO mice, indicating that ROCK proteins play a crucial role in maintaining lung function by regulating cell-cell adhesion.

GnRH Induces Citrullination of the Cytoskeleton in Murine Gonadotrope Cells

Peptidylarginine deiminases (PADs or PADIs) catalyze the conversion of positively charged arginine to neutral citrulline, which alters target protein structure and function. Our previous work established that gonadotropin-releasing hormone agonist (GnRHa) stimulates PAD2-catalyzed histone citrullination to epigenetically regulate gonadotropin gene expression in the gonadotrope-derived LβT2 cell line. However, PADs are also found in the cytoplasm. Given this, we used mass spectrometry (MS) to identify additional non-histone proteins that are citrullinated following GnRHa stimulation and characterized the temporal dynamics of this modification. Our results show that actin and tubulin are citrullinated, which led us to hypothesize that GnRHa might induce their citrullination to modulate cytoskeletal dynamics and architecture. The data show that 10 nM GnRHa induces the citrullination of β-actin, with elevated levels occurring at 10 min. The level of β-actin citrullination is reduced in the presence of the pan-PAD inhibitor biphenyl-benzimidazole-Cl-amidine (BB-ClA), which also prevents GnRHa-induced actin reorganization in dispersed murine gonadotrope cells. GnRHa induces the citrullination of β-tubulin, with elevated levels occurring at 30 min, and this response is attenuated in the presence of PAD inhibition. To examine the functional consequence of β-tubulin citrullination, we utilized fluorescently tagged end binding protein 1 (EB1-GFP) to track the growing plus end of microtubules (MT) in real time in transfected LβT2 cells. Time-lapse confocal microscopy of EB1-GFP reveals that the MT average lifetime increases following 30 min of GnRHa treatment, but this increase is attenuated by PAD inhibition. Taken together, our data suggest that GnRHa-induced citrullination alters actin reorganization and MT lifetime in gonadotrope cells.

ETV5 Silencing Produces Mesenchymal to Epithelial Transition in INS-1 (832/13) Cell Line

ETV5 has been described to be involved in the epithelial to mesenchymal transition (EMT) mainly in cancer. It is known that EMT provokes cytoskeleton remodeling, improving cellular migratory, and invasive capabilities. Moreover, overexpression of ETV5 has been correlated to cancer development and this gene has been implicated in cell proliferation. However, little is known about the downregulation of ETV5 expression in a pancreatic cell line and the inverse mesenchymal to epithelial transition (MET). Therefore, we studied the implications of ETV5 silencing over the phenotype of the insulinoma INS-1 (832/13) cell line and described the MET by partial ETV5 silencing in the INS-1 (832/13) cell line. The downregulation of ETV5 expression was obtained by using ETV5 siRNA in the insulinoma rat cell line, INS-1 (832/13). Then, ETV5 knockdown provoked a MET phenotype observed by crystal violet staining and verified by immunohistochemistry against E-cadherin. Wound healing assay showed no migration, and F-actin stain revealed rearrangement of actin microfilaments. In addition, TGFβ1 and TGFβ3 were downregulated in the absence of ETV5. ETV5 silencing induces epithelial phenotype by downregulating TGFβ1 and TGFβ3 in INS-1 (832/13) cell line.

CAMSAP3, a microtubule orientation regulator, plays a vital role in manifesting differentiation-dependent characteristics in keratinocytes

Microtubules constitute pivotal structural elements integral to cellular architecture and physiological functionality. Within the epidermis of the skin, microtubules undergo a noteworthy transition in orientation, shifting from centrosomal to non-centrosomal configurations during the processes of differentiation and stratification. This transition aligns with a discernible increase in the expression of CAMSAP3, a protein that binds to the minus end of microtubules, thereby regulating their orientation. In this study, we identified microtubule-bound CAMSAP3 within HaCaT keratinocytes, revealing an upregulation during the mitotic phase and accumulation at the intercellular bridge during cytokinesis. Building upon this observation, we scrutinized cellular responses upon a tetracycline/doxycycline-inducible CAMSAP3 expression in CAMSAP3-deficient HaCaT cells. Remarkably, CAMSAP3 deficiency induced shifts in microtubule orientation, resulting in cell cycle exit and delayed cytokinesis in a subset of the cells. Furthermore, our inquiry unveiled that CAMSAP3 deficiency adversely impacted the formation and stability of Adherens Junctions and Tight Junctions. In contrast, these perturbations were rectified upon the re-expression of CAMSAP3, underscoring the pivotal role of CAMSAP3 in manifesting differentiation-dependent characteristics in stratified keratinocytes. These observations emphasize the significance of CAMSAP3 in maintaining epidermal homeostasis.

Deficiency of copper responsive gene stmn4 induces retinal developmental defects

As part of the central nervous system (CNS), the retina senses light and also conducts and processes visual impulses. The damaged development of the retina not only causes visual damage, but also leads to epilepsy, dementia and other brain diseases. Recently, we have reported that copper (Cu) overload induces retinal developmental defects and down-regulates microtubule (MT) genes during zebrafish embryogenesis, but whether the down-regulation of microtubule genes mediates Cu stress induced retinal developmental defects is still unknown. In this study, we found that microtubule gene stmn4 exhibited obviously reduced expression in the retina of Cu overload embryos. Furthermore, stmn4 deficiency (stmn4-/-) resulted in retinal defects similar to those seen in Cu overload embryos, while overexpression of stmn4 effectively rescued retinal defects and cell apoptosis occurred in the Cu overload embryos and larvae. Meanwhile, stmn4 deficient embryos and larvae exhibited reduced mature retinal cells, the down-regulated expression of microtubules and cell cycle-related genes, and the mitotic cell cycle arrests of the retinal cells, which subsequently tended to apoptosis independent on p53. The results of this study demonstrate that Cu stress might lead to retinal developmental defects via down-regulating expression of microtubule gene stmn4, and stmn4 deficiency leads to impaired cell cycle and the accumulation of retinal progenitor cells (RPCs) and their subsequent apoptosis. The study provides a certain referee for copper overload in regulating the retinal development in fish.

Rhogef17: A novel target for endothelial barrier function

ARHGEF17 encodes the protein RhoGEF17, which is highly expressed in vascular endothelial cells. It is a guanine nucleotide exchange factor (GEF) that accelerates the exchange of GDP with GTP on many small GTPases through its Dbl homology (DH) domain, enabling the activation of Rho-GTPases such as RhoA, RhoB, and RhoC. Rho GTPase-regulated changes in the actin cytoskeleton and cell adhesion kinetics are the main mechanisms mediating many endothelial cell (EC) alterations, including cell morphology, migration, and division changes, which profoundly affect EC barrier function. This review focuses on ARHGEF17 expression, activation and biological functions in ECs, linking its regulation of cellular morphology, migration, mitosis and other cellular behaviors to disease onset and progression. Understanding ARHGEF17 mechanisms of action will contribute to the design of therapeutic approaches targeting RhoGEF17, a potential drug target for the treatment of various endothelium-related diseases, Such as vascular inflammation, carcinogenesis and transendothelial metastasis of tumors.

WAVE2 Is a Vital Regulator in Myogenic Differentiation of Progenitor Cells through the Mechanosensitive MRTFA-SRF Axis

Skeletal myogenesis is an intricate process involving the differentiation of progenitor cells into myofibers, which is regulated by actin cytoskeletal dynamics and myogenic transcription factors. Although recent studies have demonstrated the pivotal roles of actin-binding proteins (ABPs) as mechanosensors and signal transducers, the biological significance of WAVE2 (Wiskott-Aldrich syndrome protein family member 2), an ABP essential for actin polymerization, in myogenic differentiation of progenitor cells has not been investigated. Our study provides important insights into the regulatory roles played by WAVE2 in the myocardin-related transcription factor A (MRTFA)-serum response factor (SRF) signaling axis and differentiation of myoblasts. We demonstrate that WAVE2 expression is induced during myogenic differentiation and plays a pivotal role in actin cytoskeletal remodeling in C2C12 myoblasts. Knockdown of WAVE2 in C2C12 cells reduced filamentous actin levels, increased globular actin accumulation, and impaired the nuclear translocation of MRTFA. Furthermore, WAVE2 depletion in myoblasts inhibited the expression and transcriptional activity of SRF and suppressed cell proliferation in myoblasts. Consequently, WAVE2 knockdown suppressed myogenic regulatory factors (i.e., MyoD, MyoG, and SMYD1) expressions, thereby hindering the differentiation of myoblasts. Thus, this study suggests that WAVE2 is essential for myogenic differentiation of progenitor cells by modulating the mechanosensitive MRTFA-SRF axis.

MAST4 promotes primary ciliary resorption through phosphorylation of Tctex-1

The primary cilium undergoes cell cycle-dependent assembly and disassembly. Dysregulated ciliary dynamics are associated with several pathological conditions called ciliopathies. Previous studies showed that the localization of phosphorylated Tctex-1 at Thr94 (T94) at the ciliary base critically regulates ciliary resorption by accelerating actin remodeling and ciliary pocket membrane endocytosis. Here, we show that microtubule-associated serine/threonine kinase family member 4 (MAST4) is localized at the primary cilium. Suppressing MAST4 blocks serum-induced ciliary resorption, and overexpressing MAST4 accelerates ciliary resorption. Tctex-1 binds to the kinase domain of MAST4, in which the R503 and D504 residues are key to MAST4-mediated ciliary resorption. The ciliary resorption and the ciliary base localization of phospho-(T94)Tctex-1 are blocked by the knockdown of MAST4 or the expression of the catalytic-inactive site-directed MAST4 mutants. Moreover, MAST4 is required for Cdc42 activation and Rab5-mediated periciliary membrane endocytosis during ciliary resorption. These results support that MAST4 is a novel kinase that regulates ciliary resorption by modulating the ciliary base localization of phospho-(T94)Tctex-1. MAST4 is a potential new target for treating ciliopathies causally by ciliary resorption defects.

Role of Actin-Binding Proteins in Skeletal Myogenesis

Maintenance of skeletal muscle quantity and quality is essential to ensure various vital functions of the body. Muscle homeostasis is regulated by multiple cytoskeletal proteins and myogenic transcriptional programs responding to endogenous and exogenous signals influencing cell structure and function. Since actin is an essential component in cytoskeleton dynamics, actin-binding proteins (ABPs) have been recognized as crucial players in skeletal muscle health and diseases. Hence, dysregulation of ABPs leads to muscle atrophy characterized by loss of mass, strength, quality, and capacity for regeneration. This comprehensive review summarizes the recent studies that have unveiled the role of ABPs in actin cytoskeletal dynamics, with a particular focus on skeletal myogenesis and diseases. This provides insight into the molecular mechanisms that regulate skeletal myogenesis via ABPs as well as research avenues to identify potential therapeutic targets. Moreover, this review explores the implications of non-coding RNAs (ncRNAs) targeting ABPs in skeletal myogenesis and disorders based on recent achievements in ncRNA research. The studies presented here will enhance our understanding of the functional significance of ABPs and mechanotransduction-derived myogenic regulatory mechanisms. Furthermore, revealing how ncRNAs regulate ABPs will allow diverse therapeutic approaches for skeletal muscle disorders to be developed.

CCDC103 as a Prognostic Biomarker Correlated with Tumor Progression and Immune Infiltration in Glioma

Background

The Coiled-coil domain-containing proteins (CCDCs) are expressed in many cancers, but the role of Coiled-coil domain-containing protein 103 (CCDC103) in cancers remains unclear. Further investigations are necessary to ascertain its diagnostic significance and understand its biological function in cancers. This study aims to elucidate the biological functionalities of CCDC103 in glioma and evaluate the correlation between CCDC103 expression with glioma progression.

Methods

Clinical data on glioma patients were acquired from The Cancer Genome Atlas (TCGA), the Chinese Glioma Genome Atlas (CGGA), and the Gene Expression Omnibus (GEO). The evaluation encompassed the examination of correlations between CCDC103 expression, pathological characteristics, and clinical outcomes. Furthermore, the analysis included the assessment of the correlations between CCDC103 expression and immune cell infiltration as well as glioma progression.

Results

Gliomas have higher levels of CCDC103 expression than the para-carcinoma tissues. Poorer prognosis, unfavorable histological characteristics, the absence of IDH gene mutations, and the absence of chromosome 1p and 19q deletions were all associated with higher expression of CCDC103 in gliomas. In addition to patient age, tumor grade, the absence of IDH mutations, and the absence of chromosome 1p and 19q deletions, univariate and multivariate Cox analyses showed that CCDC103 expression was independently prognostic of overall survival, disease-free survival, and progression-free survival in patients with glioma. Furthermore, tumor infiltration of B cells, neutrophils, macrophages, and dendritic cells were all linked with elevated expression of CCDC103. High CCDC103 expression was linked to immune response-related signaling pathways and cell proliferation, according to gene set enrichment analysis (GSEA). Notably, the knockdown of CCDC103 in glioma cell lines resulted in a significant reduction in cell proliferation and migration.

Conclusion

The correlation between CCDC103 expression and both glioma progression and immune cell infiltration implies that CCDC103 expression holds promise as a valuable prognostic biomarker for glioma.

Roles of host SUMOylation in bacterial pathogenesis

Bacteria frequently interfere with the post-translational modifications of host cells to facilitate their survival and growth after invasion. SUMOylation, a reversible post-translational modification process, plays an important role in biological life activities. In addition to being critical to host cell metabolism and survival, SUMOylation also regulates gene expression and cell signal transmission. Moreover, SUMOylation in eukaryotic cells can be used by a variety of bacterial pathogens to advance bacterial invasion. In this minireview, we focused on the role and mechanism of host SUMOylation in the pathogenesis of six important clinical bacterial pathogens (Listeria monocytogenes, Shigella flexneri, Salmonella Typhimurium, Klebsiella pneumoniae, Staphylococcus aureus, and Escherichia coli). Taken together, this review provided new insights for understanding the unique pathogen-host interaction based on host SUMOylation and provided a novel perspective on the development of new strategies to combat bacterial infections in the future.

Actin polymerization inhibition by targeting ARPC2 affects intestinal stem cell homeostasis

Background

The rapid turnover of the intestinal epithelium is driven by the proliferation and differentiation of intestinal stem cells (ISCs). The dynamics of the F-actin cytoskeleton are critical for maintaining intercellular force and the signal transduction network. However, it remains unclear how direct interference with actin polymerization impacts ISC homeostasis. This study aims to reveal the regulatory effects of the F-actin cytoskeleton on the homeostasis of intestinal epithelium, as well as the potential risks of benproperine (BPP) as an anti-tumor drug.

Methods

Phalloidin fluorescence staining was utilized to test F-actin polymerization. Flow cytometry and IHC staining were employed to discriminate different types of intestinal epithelial cells. Cell proliferation was assessed through bromo-deoxyuridine (BrdU) and 5-ethynyl-2'-deoxyuridine (EdU) incorporation assays. The proliferation and differentiation of intestinal stem cells were replicated in vitro through organoid culture. Epithelial migration was evaluated through BrdU pulse labeling and chasing in mice.

Results

The F-actin content was observed to significantly increase as crypt cells migrated into the villus region. Additionally, actin polymerization in secretory cells, especially in Paneth cells (PCs), was much higher than that in neighboring ISCs. Treatment with the newly identified actin-related protein 2/3 complex subunit 2 (ARPC2) inhibitor BPP led to a dose-dependent increase or inhibition of intestinal organoid growth in vitro and crypt cell proliferation in vivo. Compared with the vehicle group, BPP treatment decreased the expression of Lgr5 ISC feature genes in vivo and in organoid culture. Meanwhile, PC differentiation derived from ISCs and progenitors was decreased by inhibition of F-actin polymerization. Mechanistically, BPP-induced actin polymerization inhibition may activate the Yes1-associated transcriptional regulator pathway, which affects ISC proliferation and differentiation. Accordingly, BPP treatment affected intestinal epithelial cell migration in a dose-dependent manner.

Conclusion

Our findings indicate that the regulation of cytoskeleton reorganization can affect ISC homeostasis. In addition, inhibiting ARPC2 with the Food and Drug Administration-approved drug BPP represents a novel approach to influencing the turnover of intestinal epithelial cells.

Fibroblast growth factor 2 acts as an upstream regulator of inhibition of pulmonary fibroblast activation

Fibroblast growth factor (FGF) signaling plays a crucial role in lung development and repair. Fibroblast growth factor 2 (FGF2) can inhibit fibrotic gene expression and suppress the differentiation of pulmonary fibroblasts (PFs) into myofibroblasts in vitro, suggesting that FGF2 is a potential target for inhibiting pulmonary fibrosis. To gain deeper insights into the molecular mechanism underlying FGF2-mediated regulation of PFs, we performed mRNA sequencing analysis to systematically and globally uncover the regulated genes and biological functions of FGF2 in PFs. Gene Ontology analysis revealed that the differentially expressed genes regulated by FGF2 were enriched in multiple cellular functions including extracellular matrix (ECM) organization, cytoskeleton formation, β-catenin-independent Wnt signaling pathway, supramolecular fiber organization, epithelial cell proliferation, and cell adhesion. Gene Set Enrichment Analysis and cellular experiments confirmed that FGF2 can suppress ECM and actin filament organization and increase PFs proliferation. Taken together, these findings indicate that FGF2 acts as an upstream regulator of the inhibition of PFs activation and may play a regulatory role in pulmonary fibrosis.

FLII Modulates the Myogenic Differentiation of Progenitor Cells via Actin Remodeling-Mediated YAP1 Regulation

The dynamic rearrangement of the actin cytoskeleton plays an essential role in myogenesis, which is regulated by diverse mechanisms, such as mechanotransduction, modulation of the Hippo signaling pathway, control of cell proliferation, and the influence of morphological changes. Despite the recognized importance of actin-binding protein Flightless-1 (FLII) during actin remodeling, the role played by FLII in the differentiation of myogenic progenitor cells has not been explored. Here, we investigated the roles of FLII in the proliferation and differentiation of myoblasts. FLII was found to be enriched in C2C12 myoblasts, and its expression was stable during the early stages of differentiation but down-regulated in fully differentiated myotubes. Knockdown of FLII in C2C12 myoblasts resulted in filamentous actin (F-actin) accumulation and inhibited Yes-associated protein 1 (YAP1) phosphorylation, which triggers its nuclear translocation from the cytoplasm. Consequently, the expressions of YAP1 target genes, including PCNA, CCNB1, and CCND1, were induced, and the cell cycle and proliferation of myoblasts were promoted. Moreover, FLII knockdown significantly inhibited the expression of myogenic regulatory factors, i.e., MyoD and MyoG, thereby impairing myoblast differentiation, fusion, and myotube formation. Thus, our findings demonstrate that FLII is crucial for the differentiation of myoblasts via modulation of the F-actin/YAP1 axis and suggest that FLII is a putative novel therapeutic target for muscle wasting.

The diapause-like colorectal cancer cells induced by SMC4 attenuation are characterized by low proliferation and chemotherapy insensitivity

In response to adverse environmental conditions, embryonic development may reversibly cease, a process termed diapause. Recent reports connect this phenomenon with the non-genetic responses of tumors to chemotherapy, but the mechanisms involved are poorly understood. Here, we establish a multifarious role for SMC4 in the switching of colorectal cancer cells to a diapause-like state. SMC4 attenuation promotes the expression of three investment phase glycolysis enzymes increasing lactate production while also suppressing PGAM1. Resultant high lactate levels increase ABC transporter expression via histone lactylation, rendering tumor cells insensitive to chemotherapy. SMC4 acts as co-activator of PGAM1 transcription, and the coordinate loss of SMC4 and PGAM1 affects F-actin assembly, inducing cytokinesis failure and polyploidy, thereby inhibiting cell proliferation. These insights into the mechanisms underlying non-genetic chemotherapy resistance may have significant implications for the field, advancing our understanding of aerobic glycolysis functions in tumor and potentially informing future therapeutic strategies.

MicroRNA miR-263b-5p Regulates Developmental Growth and Cell Association by Suppressing Laminin A in Drosophila

Basement membranes (BMs) play important roles under various physiological conditions in animals, including ecdysozoans. During development, BMs undergo alterations through diverse intrinsic and extrinsic regulatory mechanisms; however, the full complement of pathways controlling these changes remain unclear. Here, we found that fat body-overexpression of Drosophila miR-263b, which is highly expressed during the larval-to-pupal transition, resulted in a decrease in the overall size of the larval fat body, and ultimately, in a severe growth defect accompanied by a reduction in cell proliferation and cell size. Interestingly, we further observed that a large proportion of the larval fat body cells were prematurely disassociated from each other. Moreover, we present evidence that miR-263b-5p suppresses the main component of BMs, Laminin A (LanA). Through experiments using RNA interference (RNAi) of LanA, we found that its depletion phenocopied the effects in miR-263b-overexpressing flies. Overall, our findings suggest a potential role for miR-263b in developmental growth and cell association by suppressing LanA expression in the Drosophila fat body.

Phase intensity nanoscope (PINE) opens long-time investigation windows of living matter

Fundamental to all living organisms and living soft matter are emergent processes in which the reorganization of individual constituents at the nanoscale drives group-level movements and shape changes at the macroscale over time. However, light-induced degradation of fluorophores, photobleaching, is a significant problem in extended bioimaging in life science. Here, we report opening a long-time investigation window by nonbleaching phase intensity nanoscope: PINE. We accomplish phase-intensity separation such that nanoprobe distributions are distinguished by an integrated phase-intensity multilayer thin film (polyvinyl alcohol/liquid crystal). We overcame a physical limit to resolve sub-10 nm cellular architectures, and achieve the first dynamic imaging of nanoscopic reorganization over 250 h using PINE. We discover nanoscopic rearrangements synchronized with the emergence of group-level movements and shape changes at the macroscale according to a set of interaction rules with importance in cellular and soft matter reorganization, self-organization, and pattern formation.

Effects on cell cycle progression and cytoskeleton organization of five Bothrops spp. venoms in cell culture-based assays

Snake envenomation is a neglected tropical disease. In Brazil, the Bothrops genus is responsible for about 86% of snakebite accidents. Despite extensive evidence of the cytotoxicity of snake venoms, the cellular and molecular mechanisms involved are not fully understood, especially regarding the effects on cell cycle progression and cytoskeleton organization. Traditionally, the effectiveness and quality control tests of venoms and antivenoms are assessed by in vivo assays. Despite this, there is a rising effort to develop surrogate in vitro models according to the 3R principle (Replacement, Reduction, and Refinement). In this study, we treated rat liver cells (BRL-3A) with venoms from five Bothrops species (B. jararaca, B. jararacussu, B. moojeni, B. alternatus, and B. neuwiedi) and analyzed cell viability and IC50 by MTT assay, cell cycle phases distribution by flow cytometry, and morphology and cytoskeleton alterations by immunofluorescence. In addition, we evaluated the correlation between IC50 and the enzymatic and biological activities of each venom. Our results indicated that Bothrops spp. venoms decreased the cell viability of rat liver BRL-3A cells. The rank order of potency was B. jararacussu > B. moojeni > B. alternatus > B. jararaca > B. neuwiedi. The mechanisms of cytotoxicity were related to microtubules and actin network disruption, but not to cell cycle arrest. No clear correlation was found between the IC50 and retrieved literature data of in vitro enzymatic and in vivo biological activities. This work contributed to understanding cellular and molecular mechanisms underlying the Bothrops spp. venom cytotoxicity, which can help to improve envenomation treatment, as well as disclose potential therapeutic properties of snake venoms.

Faulty Metabolism: A Potential Instigator of an Aggressive Phenotype in Cdk5-dependent Medullary Thyroid Carcinoma

Mechanistic modeling of cancers such as Medullary Thyroid Carcinoma (MTC) to emulate patient-specific phenotypes is challenging. The discovery of potential diagnostic markers and druggable targets in MTC urgently requires clinically relevant animal models. Here we established orthotopic mouse models of MTC driven by aberrantly active Cdk5 using cell-specific promoters. Each of the two models elicits distinct growth differences that recapitulate the less or more aggressive forms of human tumors. The comparative mutational and transcriptomic landscape of tumors revealed significant alterations in mitotic cell cycle processes coupled with the slow-growing tumor phenotype. Conversely, perturbation in metabolic pathways emerged as critical for aggressive tumor growth. Moreover, an overlapping mutational profile was identified between mouse and human tumors. Gene prioritization revealed putative downstream effectors of Cdk5 which may contribute to the slow and aggressive growth in the mouse MTC models. In addition, Cdk5/p25 phosphorylation sites identified as biomarkers for Cdk5-driven neuroendocrine tumors (NETs) were detected in both slow and rapid onset models and were also histologically present in human MTC. Thus, this study directly relates mouse and human MTC models and uncovers vulnerable pathways potentially responsible for differential tumor growth rates. Functional validation of our findings may lead to better prediction of patient-specific personalized combinational therapies.

Triplex metallohelices have enantiomer-dependent mechanisms of action in colon cancer cells

Self-assembled enantiomers of an asymmetric di-iron metallohelix differ in their antiproliferative activities against HCT116 colon cancer cells such that the compound with Λ-helicity at the metals becomes more potent than the Δ compound with increasing exposure time. From concentration- and temperature-dependent ⁵⁷Fe isotopic labelling studies of cellular accumulation we postulate that while the more potent Λ enantiomer undergoes carrier-mediated efflux, for Δ the process is principally equilibrative. Cell fractionation studies demonstrate that both enantiomers localise in a similar fashion; compound is observed mostly within the cytoskeleton and/or genomic DNA, with significant amounts also found in the nucleus and membrane, but with negligible concentration in the cytosol. Cell cycle analyses using flow cytometry reveal that the Δ enantiomer induces mild arrest in the G₁ phase, while Λ causes a very large dose-dependent increase in the G₂/M population at a concentration significantly below the relevant IC₅₀. Correspondingly, G₂-M checkpoint failure as a result of Λ-metallohelix binding to DNA is shown to be feasible by linear dichroism studies, which indicate, in contrast to the Δ compound, a quite specific mode of binding, probably in the major groove. Further, spindle assembly checkpoint (SAC) failure, which could also be responsible for the observed G₂/M arrest, is established as a feasible mechanism for the Λ helix via drug combination (synergy) studies and the discovery of tubulin and actin inhibition. Here, while the Λ compound stabilizes F-actin and induces a distinct change in tubulin architecture of HCT116 cells, Δ promotes depolymerization and more subtle changes in microtubule and actin networks.

The Role of non-muscle actin paralogs in cell cycle progression and proliferation

Uncontrolled cell proliferation leads to several pathologies, including cancer. Thus, this process must be tightly regulated. The cell cycle accounts for cell proliferation, and its progression is coordinated with changes in cell shape, for which cytoskeleton reorganization is responsible. Rearrangement of the cytoskeleton allows for its participation in the precise division of genetic material and cytokinesis. One of the main cytoskeletal components is filamentous actin-based structures. Mammalian cells have at least six actin paralogs, four of which are muscle-specific, while two, named β- and γ-actin, are abundantly present in all types of cells. This review summarizes the findings that establish the role of non-muscle actin paralogs in regulating cell cycle progression and proliferation. We discuss studies showing that the level of a given non-muscle actin paralog in a cell influences the cell's ability to progress through the cell cycle and, thus, proliferation. Moreover, we elaborate on the non-muscle actins' role in regulating gene transcription, interactions of actin paralogs with proteins involved in controlling cell proliferation, and the contribution of non-muscle actins to different structures in a dividing cell. The data cited in this review show that non-muscle actins regulate the cell cycle and proliferation through varying mechanisms. We point to the need for further studies addressing these mechanisms.

Induction of miR-665-3p Impairs the Differentiation of Myogenic Progenitor Cells by Regulating the TWF1-YAP1 Axis

Actin dynamics are known to orchestrate various myogenic processes in progenitor cells. Twinfilin-1 (TWF1) is an actin-depolymerizing factor that plays a crucial role in the differentiation of myogenic progenitor cells. However, little is known about the mechanisms underlying the epigenetic regulation of TWF1 expression and impaired myogenic differentiation in the background of muscle wasting. This study investigated how miR-665-3p affects TWF1 expression, actin filaments' modulation, proliferation, and myogenic differentiation in progenitor cells. Palmitic acid, the most prevalent saturated fatty acid (SFA) in food, suppressed TWF1 expression and inhibited the myogenic differentiation of C2C12 cells while increasing the level of miR-665-3p expression. Interestingly, miR-665-3p inhibited TWF1 expression by targeting TWF1 3'UTR directly. In addition, miR-665-3p accumulated filamentous actin (F-actin) and enhanced the nuclear translocation of Yes-associated protein 1 (YAP1), consequently promoting cell cycle progression and proliferation. Furthermore, miR-665-3p suppressed the expressions of myogenic factors, i.e., MyoD, MyoG, and MyHC, and consequently impaired myoblast differentiation. In conclusion, this study suggests that SFA-inducible miR-665-3p suppresses TWF1 expression epigenetically and inhibits myogenic differentiation by facilitating myoblast proliferation via the F-actin/YAP1 axis.

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.

Mir-302a/TWF1 Axis Impairs the Myogenic Differentiation of Progenitor Cells through F-Actin-Mediated YAP1 Activation

Actin cytoskeleton dynamics have been found to regulate myogenesis in various progenitor cells, and twinfilin-1 (TWF1), an actin-depolymerizing factor, plays a vital role in actin dynamics and myoblast differentiation. Nevertheless, the molecular mechanisms underlying the epigenetic regulation and biological significance of TWF1 in obesity and muscle wasting have not been explored. Here, we investigated the roles of miR-302a in TWF1 expression, actin filament modulation, proliferation, and myogenic differentiation in C2C12 progenitor cells. Palmitic acid, the most prevalent saturated fatty acid (SFA) in the diet, decreased the expression of TWF1 and impeded myogenic differentiation while increasing the miR-302a levels in C2C12 myoblasts. Interestingly, miR-302a inhibited TWF1 expression directly by targeting its 3′UTR. Furthermore, ectopic expression of miR-302a promoted cell cycle progression and proliferation by increasing the filamentous actin (F-actin) accumulation, which facilitated the nuclear translocation of Yes-associated protein 1 (YAP1). Consequently, by suppressing the expressions of myogenic factors, i.e., MyoD, MyoG, and MyHC, miR-302a impaired myoblast differentiation. Hence, this study demonstrated that SFA-inducible miR-302a suppresses TWF1 expression epigenetically and impairs myogenic differentiation by facilitating myoblast proliferation via F-actin-mediated YAP1 activation.

Targeting Ras-binding domain of ELMO1 by computational nanobody design

The control of cell movement through manipulation of cytoskeletal structure has therapeutic prospects notably in the development of novel anti-metastatic drugs. In this study, we determine the structure of Ras-binding domain (RBD) of ELMO1, a protein involved in cytoskeletal regulation, both alone and in complex with the activator RhoG and verify its targetability through computational nanobody design. Using our dock-and-design approach optimized with native-like initial pose selection, we obtain Nb01, a detectable binder from scratch in the first-round design. An affinity maturation step guided by structure-activity relationship at the interface generates 23 Nb01 sequence variants and 17 of them show enhanced binding to ELMO1-RBD and are modeled to form major spatial overlaps with RhoG. The best binder, Nb29, inhibited ELMO1-RBD/RhoG interaction. Molecular dynamics simulation of the flexibility of CDR2 and CDR3 of Nb29 reveal the design of stabilizing mutations at the CDR-framework junctions potentially confers the affinity enhancement.

WDR73 Depletion Destabilizes PIP4K2C Activity and Impairs Focal Adhesion Formation in Galloway–Mowat Syndrome

Simple Summary

Galloway–Mowat syndrome is a rare genetic disease, classically characterized by a combination of various neurological symptoms and nephrotic syndrome. WDR73 is the pathogenic gene responsible for Galloway–Mowat syndrome. However, the pathological and molecular mechanisms of Galloway–Mowat syndrome, especially nephrotic syndrome caused by WDR73 deficiency, remains unknown. In this study, we knocked out the WDR73 in human embryonic kidney 293 cells to observe the morphological characteristics of the cells and elucidate the functions of WDR73. Additionally, we used a combination of proteomics, transcriptomics, and biochemical assays to identify the regulated targets of WDR73. We aimed to discover directly interacting molecules and the regulatory pathway of WDR73 and to illustrate the molecular mechanism between the WDR73 pathway and nephrotic disease in Galloway–Mowat syndrome. From the molecular mechanism we found in vitro, we draw a hypothesis that the damage to focal adhesion of podocytes caused by WDR73 defect is the key issue of kidney dysfunction. Finally, we verified the hypothesis in a podocyte-specific conditional knockout Wdr73 mouse model.

Abstract

(1) Background: Galloway–Mowat syndrome (GAMOS) is a rare genetic disease, classically characterized by a combination of various neurological symptoms and nephrotic syndrome. WDR73 is the pathogenic gene responsible for GAMOS1. However, the pathological and molecular mechanisms of GAMOS1, especially nephrotic syndrome caused by WDR73 deficiency, remain unknown. (2) Methods and Results: In this study, we first observed remarkable cellular morphological changes including impaired cell adhesion, decreased pseudopodia, and G2/M phase arrest in WDR73 knockout (KO) HEK 293 cells. The differentially expressed genes in WDR73 KO cells were enriched in the focal adhesion (FA) pathway. Additionally, PIP4K2C, a phospholipid kinase also involved in the FA pathway, was subsequently validated to interact with WDR73 via protein microarray and GST pulldown. WDR73 regulates PIP4K2C protein stability through the autophagy–lysosomal pathway. The stability of PIP4K2C was significantly disrupted by WDR73 KO, leading to a remarkable reduction in PIP2 and thus weakening the FA formation. In addition, we found that podocyte-specific conditional knockout (Wdr73 CKO) mice showed high levels of albuminuria and podocyte foot process injury in the ADR-induced model. FA formation was impaired in primary podocytes derived from Wdr73 CKO mice. (3) Conclusions: Since FA has been well known for its critical roles in maintaining podocyte structures and function, our study indicated that nephrotic syndrome in GAMOS1 is associated with disruption of FA caused by WDR73 deficiency.

Kank1 Is Essential for Myogenic Differentiation by Regulating Actin Remodeling and Cell Proliferation in C2C12 Progenitor Cells

Actin cytoskeleton dynamics are essential regulatory processes in muscle development, growth, and regeneration due to their modulation of mechanotransduction, cell proliferation, differentiation, and morphological changes. Although the KN motif and ankyrin repeat domain-containing protein 1 (Kank1) plays a significant role in cell adhesion dynamics, actin polymerization, and cell proliferation in various cells, the functional significance of Kank1 during the myogenic differentiation of progenitor cells has not been explored. Here, we report that Kank1 acts as a critical regulator of the proliferation and differentiation of muscle progenitor cells. Kank1 was found to be expressed at a relatively high level in C2C12 myoblasts, and its expression was modulated during the differentiation. Depletion of Kank1 by siRNA (siKank1) increased the accumulation of filamentous actin (F-actin). Furthermore, it facilitated the nuclear localization of Yes-associated protein 1 (YAP1) by diminishing YAP1 phosphorylation in the cytoplasm, which activated the transcriptions of YAP1 target genes and promoted proliferation and cell cycle progression in myoblasts. Notably, depletion of Kank1 suppressed the protein expression of myogenic regulatory factors (i.e., MyoD and MyoG) and dramatically inhibited myoblast differentiation and myotube formation. Our results show that Kank1 is an essential regulator of actin dynamics, YAP1 activation, and cell proliferation and that its depletion impairs the myogenic differentiation of progenitor cells by promoting myoblast proliferation triggered by the F-actin-induced nuclear translocation of YAP1.

The effects of microgravity on bone structure and function

Humans are spending an increasing amount of time in space, where exposure to conditions of microgravity causes 1-2% bone loss per month in astronauts. Through data collected from astronauts, as well as animal and cellular experiments conducted in space, it is evident that microgravity induces skeletal deconditioning in weight-bearing bones. This review identifies contentions in current literature describing the effect of microgravity on non-weight-bearing bones, different bone compartments, as well as the skeletal recovery process in human and animal spaceflight data. Experiments in space are not readily available, and experimental designs are often limited due to logistical and technical reasons. This review introduces a plethora of on-ground research that elucidate the intricate process of bone loss, utilising technology that simulates microgravity. Observations from these studies are largely congruent to data obtained from spaceflight experiments, while offering more insights behind the molecular mechanisms leading to microgravity-induced bone loss. These insights are discussed herein, as well as how that knowledge has contributed to studies of current therapeutic agents. This review also points out discrepancies in existing data, highlighting knowledge gaps in our current understanding. Further dissection of the exact mechanisms of microgravity-induced bone loss will enable the development of more effective preventative and therapeutic measures to protect against bone loss, both in space and possibly on ground.

Characterization and Functional Study of FAM49B Reveals Its Effect on Cell Proliferation in HEK293T Cells

FAM49B/Fam49b is a member of the Fam49 (Family with sequence similarity 49) gene family, which is characterized by the conserved domain, DUF1394 (Domain of Unknown Function 1394). It has also been named CYRI-B (CYFIP related RAC1 interactor B), implicating its important function of regulating RAC1-driven cytoskeleton remolding. In this study, to further investigate its functions and mechanisms affecting cell behaviors, HEK293T cells (where FAM49B is highly expressed) were used to establish a FAM49B knockout cell line by CRISPR/Cas9 genome editing technology. Our data have clearly revealed that there are triple alleles of FAM49B in the genome of HEK293T cells. Meanwhile, the proliferation deficiency of the FAM49B KO HEK293T cell line and the significantly changed cell proliferation related gene expression profiles, such as CCND1, have been uncovered. At the same time, the existence of isoform 3 has been confirmed in HEK293T cells. Our studies have suggested that FAM49B may also affect cell proliferation via Cyclins, besides its influence on the cytoskeleton.

Roots of the Malformations of Cortical Development in the Cell Biology of Neural Progenitor Cells

The cerebral cortex is a structure that underlies various brain functions, including cognition and language. Mammalian cerebral cortex starts developing during the embryonic period with the neural progenitor cells generating neurons. Newborn neurons migrate along progenitors’ radial processes from the site of their origin in the germinal zones to the cortical plate, where they mature and integrate in the forming circuitry. Cell biological features of neural progenitors, such as the location and timing of their mitoses, together with their characteristic morphologies, can directly or indirectly regulate the abundance and the identity of their neuronal progeny. Alterations in the complex and delicate process of cerebral cortex development can lead to malformations of cortical development (MCDs). They include various structural abnormalities that affect the size, thickness and/or folding pattern of the developing cortex. Their clinical manifestations can entail a neurodevelopmental disorder, such as epilepsy, developmental delay, intellectual disability, or autism spectrum disorder. The recent advancements of molecular and neuroimaging techniques, along with the development of appropriate in vitro and in vivo model systems, have enabled the assessment of the genetic and environmental causes of MCDs. Here we broadly review the cell biological characteristics of neural progenitor cells and focus on those features whose perturbations have been linked to MCDs.

Exploring Cell Surface-Nanopillar Interactions with 3D Super-Resolution Microscopy

Plasma membrane topography has been shown to strongly influence the behavior of many cellular processes such as clathrin-mediated endocytosis, actin rearrangements, and others. Recent studies have used three-dimensional (3D) nanostructures such as nanopillars to imprint well-defined membrane curvatures (the "nano-bio interface"). In these studies, proteins and their interactions were probed by two-dimensional fluorescence microscopy. However, the low resolution and limited axial detail of such methods are not optimal to determine the relative spatial position and distribution of proteins along a 100 nm-diameter object, which is below the optical diffraction limit. Here, we introduce a general method to explore the nanoscale distribution of proteins at the nano-bio interface with 10-20 nm precision using 3D single-molecule super-resolution (SR) localization microscopy. This is achieved by combining a silicone-oil immersion objective and 3D double-helix point spread function microscopy. We carefully adjust the objective to minimize spherical aberrations between quartz nanopillars and the cell. To validate the 3D SR method, we imaged the 3D shape of surface-labeled nanopillars and compared the results with electron microscopy measurements. Turning to transmembrane-anchored labels in cells, the high quality 3D SR reconstructions reveal the membrane tightly wrapping around the nanopillars. Interestingly, the cytoplasmic protein AP-2 involved in clathrin-mediated endocytosis accumulates along the nanopillar above a specific threshold of 1/R (the reciprocal of the radius) membrane curvature. Finally, we observe that AP-2 and actin preferentially accumulate at positive Gaussian curvature near the pillar caps. Our results establish a general method to investigate the nanoscale distribution of proteins at the nano-bio interface using 3D SR microscopy.

Disruption of actin dynamics induces autophagy of the eukaryotic chaperonin TRiC/CCT

Autophagy plays important role in the intracellular protein quality control system by degrading abnormal organelles and proteins, including large protein complexes such as ribosomes. The eukaryotic chaperonin tailless complex polypeptide 1 (TCP1) ring complex (TRiC), also called chaperonin-containing TCP1 (CCT), is a 1-MDa hetero-oligomer complex comprising 16 subunits that facilitates the folding of ~10% of the cellular proteome that contains actin. However, the quality control mechanism of TRiC remains unclear. To monitor the autophagic degradation of TRiC, we generated TCP1α-RFP-GFP knock-in HeLa cells using a CRISPR/Cas9-knock-in system with an RFP-GFP donor vector. We analyzed the autophagic degradation of TRiC under several stress conditions and found that treatment with actin (de)polymerization inhibitors increased the lysosomal degradation of TRiC, which was localized in lysosomes and suppressed by deficiency of autophagy-related genes. Furthermore, we found that treatment with actin (de)polymerization inhibitors increased the association between TRiC and unfolded actin, suggesting that TRiC was inactivated. Moreover, unfolded actin mutants were degraded by autophagy. Taken together, our results indicate that autophagy eliminates inactivated TRiC, serving as a quality control system.

MiR-320-3p Regulates the Proliferation and Differentiation of Myogenic Progenitor Cells by Modulating Actin Remodeling

Skeletal myogenesis is essential for the maintenance of muscle quality and quantity, and impaired myogenesis is intimately associated with muscle wasting diseases. Although microRNA (miRNA) plays a crucial role in myogenesis and relates to muscle wasting in obesity, the molecular targets and roles of miRNAs modulated by saturated fatty acids (SFA) are largely unknown. In the present study, we investigated the role of miR-320-3p on the differentiation of myogenic progenitor cells. Palmitic acid (PA), the most abundant dietary SFA, suppressed myogenic factors expression and impaired differentiation in C2C12 myoblasts, and these effects were accompanied by CFL2 downregulation and miR-320-3p upregulation. In particular, miR-320-3p appeared to target CFL2 mRNA directly and suppress the expression of CFL2, an essential factor for filamentous actin (F-actin) depolymerization. Transfection of myoblasts with miR-320-3p mimic increased F-actin formation and nuclear translocation of Yes-associated protein 1 (YAP1), a key component of mechanotransduction. Furthermore, miR-320-3p mimic increased myoblast proliferation and markedly impeded the expression of MyoD and MyoG, consequently inhibiting myoblast differentiation. In conclusion, our current study highlights the role of miR-320-3p on CFL2 expression, YAP1 activation, and myoblast differentiation and suggests that PA-inducible miR-320-3p is a significant mediator of muscle wasting in obesity.

Glucocorticoids Promote Extracellular Matrix Component Remodeling by Activating YAP in Human Retinal Capillary Endothelial Cells

Remodeling of extracellular matrix (ECM) components of endothelial cells is the main cause of retinal vascular basement membrane (BM) thickening, which leads to the initiation and perpetuation of microvasculopathy of diabetic retinopathy (DR). Excessive amounts of glucocorticoids (GCs) are related to the presence and severity of DR, however transcriptional effects of GCs on the biology of human retinal capillary endothelial cells (HRCECs) and its impacts on DR are still unclear. Here, we showed that GC (hydrocortisone) treatment induced ECM component [fibronectin (FN) and type IV collagen (Col IV)] expression and morphological changes in HRCECs via the glucocorticoid receptor (GR), which depended on the nuclear translocation of YAP coactivator. Mechanistically, GCs induced stress fiber formation in HRCECs, while blocking stress fiber formation inhibited GC-induced YAP nuclear translocation. Overexpression of FN, but not Col IV, activated YAP through the promotion of stress fiber formation via ECM-integrin signaling. Thus, a feedforward loop is established to sustain YAP activity. Using mRNA sequencing of HRCECs with overexpressed YAP or GC treatment, we found a similarity in Gene Ontology (GO) terms, differentially expressed genes (DEGs) and transcription factors (TFs) between the two RNA-seq datasets. In vivo, YAP was activated in retina vascular ECs of STZ-induced diabetic mice, and TF prediction analysis of published RNA-seq data of dermal vascular ECs from T2DM patients showed that GR and TEAD (the main transcription factor for YAP) were enriched. Together, GCs activate YAP and promote ECM component (FN and Col IV) remodeling in retinal capillary endothelial cells, and the underlying regulatory mechanism may provide new insights into the vascular BM thickening of the retina in the early pathogenesis of DR.

Wasp controls oriented migration of endothelial cells to achieve functional vascular patterning

Endothelial cell migration and proliferation are essential for the establishment of a hierarchical organization of blood vessels and optimal distribution of blood. However, how these cellular processes are quantitatively coordinated to drive vascular network morphogenesis remains unknown. Here, using the zebrafish vasculature as a model system, we demonstrate that the balanced distribution of endothelial cells, as well as the resulting regularity of vessel calibre, is a result of cell migration from veins towards arteries and cell proliferation in veins. We identify the Wiskott-Aldrich Syndrome protein (WASp) as an important molecular regulator of this process and show that loss of coordinated migration from veins to arteries upon wasb depletion results in aberrant vessel morphology and the formation of persistent arteriovenous shunts. We demonstrate that WASp achieves its function through the coordination of junctional actin assembly and PECAM1 recruitment and provide evidence that this is conserved in humans. Overall, we demonstrate that functional vascular patterning in the zebrafish trunk is established through differential cell migration regulated by junctional actin, and that interruption of differential migration may represent a pathomechanism in vascular malformations.

Summary: Regular diameter of developing veins and arteries in the zebrafish trunk is controlled by differential endothelial cell proliferation and WASp-driven directed cell migration.

Phosphoproteomics identifies potential downstream targets of the integrin α2β1 inhibitor BTT-3033 in prostate stromal cells

Background

Integrin α2β1 inhibitor BTT-3033 (1-(4-fluorophenyl)-N-methyl-N-[4[[(phenylamino)carbonyl]amino]phenyl]-1H-pyrazole-4-sulfonamide) was recently reported to inhibit neurogenic and thromboxane A2-induced human prostate smooth muscle contraction, and thus represents a target with a different inhibition spectrum than that of α1-blockers in benign prostate hyperplasia (BPH) treatments. Clarifying the underlying mechanisms of the inhibition effects will provide insights into the role of integrin α2β1 in prostate contraction and enable new intracellular targets for smooth muscle contraction to be explored.

Methods

ProteomeHD was used to predict and enrich the top co-regulated proteins of integrin α2 (ITGA2). A phosphoproteomic analysis was conducted on human prostate stromal cells (WPMY-1) treated with 1 or 10 µM of BTT-3033 or solvent for controls. A clustering analysis was conducted to identify the intracellular targets that were inhibited in a dose-dependent manner. Gene ontology (GO) and annotation enrichments were conducted to examine any functional alterations and identify possible downstream targets. A Kinase-substrate enrichment analysis (KSEA) was conducted to identify kinases-substrate relationships.

Results

Enrichments of the actin cytoskeleton and guanosine triphosphatases (GTPases) signaling were predicted from the co-regulated proteins with ITGA2. LIM domain kinases, including LIM domain and actin-binding 1 (LIMA1), zyxin (ZYX), and thyroid receptor-interacting protein 6 (TRIP6), which are functionally associated with focal adhesions and the cytoskeleton, were present in the clusters with dose-dependent phosphorylation inhibition pattern. 15 substrates were dose-dependently inhibited according to the KSEA, including polo-like kinase 1 (PLK1), and GTPases signaling proteins, such as disheveled segment polarity protein 2 (DVL2).

Conclusions

In this study, we proposed that the mechanisms underlying the contractile and proliferative effects of integrin α2β1 are the LIM domain kinases, including the ZYX family, and substrates, including PLK1 and DVL2.

Role of MiR-325-3p in the Regulation of CFL2 and Myogenic Differentiation of C2C12 Myoblasts

Skeletal myogenesis is required to maintain muscle mass and integrity, and impaired myogenesis is causally linked to the etiology of muscle wasting. Recently, it was shown that excessive uptake of saturated fatty acids (SFA) plays a significant role in the pathogenesis of muscle wasting. Although microRNA (miRNA) is implicated in the regulation of myogenesis, the molecular mechanism whereby SFA-induced miRNAs impair myogenic differentiation remains largely unknown. Here, we investigated the regulatory roles of miR-325-3p on CFL2 expression and myogenic differentiation in C2C12 myoblasts. PA impeded myogenic differentiation, concomitantly suppressed CFL2 and induced miR-325-3p. Dual-luciferase analysis revealed that miR-325-3p directly targets the 3'UTR of CFL2, thereby suppressing the expression of CFL2, a crucial factor for actin dynamics. Transfection with miR-325-3p mimic resulted in the accumulation of actin filaments (F-actin) and nuclear Yes-associated protein (YAP) in myoblasts and promoted myoblast proliferation and cell cycle progression. Consequently, miR-325-3p mimic significantly attenuated the expressions of myogenic factors and thereby impaired the myogenic differentiation of myoblasts. The roles of miR-325-3p on CFL2 expression, F-actin modulation, and myogenic differentiation suggest a novel miRNA-mediated regulatory mechanism of myogenesis and PA-inducible miR-325-3p may be a critical mediator between obesity and muscle wasting.

Palmitic Acid-Induced miR-429-3p Impairs Myoblast Differentiation by Downregulating CFL2

MicroRNAs are known to play a critical role in skeletal myogenesis and maintenance, and cofilin-2 (CFL2) is necessary for actin cytoskeleton dynamics and myogenic differentiation. Nonetheless, target molecules and the modes of action of miRNAs, especially those responsible for the inhibitory mechanism on the myogenesis by saturated fatty acids (SFA) or obesity, still remain unclear. Here, we reported the role played by miR-429-3p on CFL2 expression, actin filament dynamics, myoblast proliferation, and myogenic differentiation in C2C12 cells. Palmitic acid (PA), the most abundant SFA in diet, inhibited the myogenic differentiation of myoblasts, accompanied by CFL2 reduction and miR-429-3p induction. Interestingly, miR-429-3p suppressed the expression of CFL2 by targeting the 3'UTR of CFL2 mRNA directly. Transfection of miR-429-3p mimic in myoblasts increased F-actin formation and augmented nuclear YAP level, thereby promoting cell cycle progression and myoblast proliferation. Moreover, miR-429-3p mimic drastically suppressed the expressions of myogenic factors, such as MyoD, MyoG, and MyHC, and impaired myogenic differentiation of C2C12 cells. Therefore, this study unveiled the crucial role of miR-429-3p in myogenic differentiation through the suppression of CFL2 and provided implications of SFA-induced miRNA in the regulation of actin dynamics and skeletal myogenesis.

Exposure to perfluorooctane sulfonate in vitro perturbs the quality of porcine oocytes via induction of apoptosis

Perfluorooctane sulfonate (PFOS) is a widely used artificial surfactant with potential toxicity to humans and animals. However, little is known about the impact of PFOS on the female germ cell development. Here, we report that PFOS exposure weakens oocyte quality by disturbing oocyte meiotic competency and fertilization ability. Specifically, PFOS exposure impaired cytoskeleton assembly including spindle organization and actin polymerization to cause the oocyte maturation arrest. In addition, PFOS exposure also impaired the mitochondrial dynamics and function, resulting in the increased levels of reactive oxygen species (ROS) and DNA damage as well as generation of apoptosis. Lastly, PFOS exposure compromised the distribution of cortical granules (CGs) and their component ovastacin, leading to the failure of sperm binding and fertilization. Altogether, our study illustrates that oxidative stress-induced apoptosis is a major cause for the deteriorated quality of porcine oocytes exposed to PFOS.