Talin promotes integrin activation accompanied by generation of tension in talin and an increase in osmotic pressure in neurite outgrowth

HDAC1 is involved in the destabilization of the HSF2 protein under non-stress and stress conditions

Heat shock transcription factors 1 and 2 (HSF1 and HSF2) are the major regulators of the cellular response to stressors, notably to heat shock and to oxidative stress. HSF1 and HSF2 are also important contributors in devasting human pathologies like cancer, neurodegenerative disorders, and neurodevelopmental disorders. Under physiological conditions, nuclear HSF2 is detected in only a few cell types in human adult healthy tissues. In contrast, HSF2 protein levels are elevated at some embryonic stages, but greatly vary among cell types and fluctuates during the cell cycle in diverse cell lines. HSF2 is a short-lived protein whose rapid turnover is controlled by the components of the ubiquitin-proteasome degradation pathway and the stabilization of HSF2 constitutes an important step that regulates its DNA-binding activity and mediates its roles in non-stress, physiological processes. The control of HSF2 abundancy is therefore critical for its regulatory roles in stress responses as well as under physiological conditions. In this regard, the fetal brain cortex is a singular context where HSF2 is strikingly abundant, exhibits constitutive DNA-binding activity and, by controlling a specific repertoire of target genes that play important roles at multiple steps of neurodevelopment. Recently, we showed that the lysine-acetyl-transferases CBP and EP300 stabilize the HSF2 protein under both unstressed and stressed conditions and that the integrity of the CBP/EP300-HSF2 pathway is important for neurodevelopment. Here, we identify the lysine-deacetylase HDAC1 as a novel HSF2-interacting protein partner and regulator, in an unbiased manner, and show that HSF2 and HDAC1 localize in the same cells in the developing mouse cortex and human cerebral organoids (hCOs). We also demonstrate that HDAC1, through its catalytic activity, destabilizes the HSF2 protein, through HSF2 poly-ubiquitination and proteasomal degradation, under both normal and stress conditions.

Talin-1 variants associated with spontaneous coronary artery dissection (SCAD) highlight how even subtle changes in multi-functional scaffold proteins can manifest in disease

Variants of talin-1 (TLN1) have recently been linked with spontaneous coronary artery dissection (SCAD) a condition where a tear can form in the wall of a heart artery necessitating immediate medical care. One talin-1 variant, A2013T, has an extensive familial pedigree of SCAD, which led to the screening for, and identification of, further talin-1 variants in SCAD patients. Here we evaluated these variants with commonly used pathogenicity prediction tools and found it challenging to reliably classify SCAD-associated variants, even A2013T where the evidence of a causal role is strong. Using biochemical and cell biological methods, we show that SCAD-associated variants in talin-1, which would typically be classified as non-pathogenic, still cause a measurable impact on protein structure and cell behaviour, including cell movement and wound healing capacity. Together, this indicates that even subtle variants in central mechanosensitive adapter proteins, can give rise to significant health impacts at the individual level, suggesting the need for a possible re-evaluation of the scoring criteria for pathogenicity prediction for talin variants.

Apnea of prematurity induces short and long-term development-related transcriptional changes in the murine cerebellum

Apnea of prematurity (AOP) affects more than 50% of preterm infants and leads to perinatal intermittent hypoxia (IH) which is a major cause of morbimortality worldwide. At birth, the human cerebellar cortex is still immature, making it vulnerable to perinatal events. Additionally, studies have shown a correlation between cerebellar functions and the deficits observed in children who have experienced AOP. Yet, the cerebellar alterations underpinning this link remain poorly understood. To gain insight into the involvement of the cerebellum in perinatal hypoxia-related consequences, we developed a mouse model of AOP. Our previous research has revealed that IH induces oxidative stress in the developing cerebellum, as evidenced by the over-expression of genes involved in reactive oxygen species production and the under-expression of genes encoding antioxidant enzymes. These changes suggest a failure of the defense system against oxidative stress and could be responsible for neuronal death in the cerebellum. Building upon these findings, we conducted a transcriptomic study of the genes involved in the processes that occur during cerebellar development. Using real-time PCR, we analyzed the expression of these genes at different developmental stages and in various cell types. This enabled us to pinpoint a timeframe of vulnerability at P8, which represents the age with the highest number of downregulated genes in the cerebellum. Furthermore, we discovered that our IH protocol affects several molecular pathways, including proliferation, migration, and differentiation. This indicates that IH can impact the development of different cell types, potentially contributing to the histological and behavioral deficits observed in this model. Overall, our data strongly suggest that the cerebellum is highly sensitive to IH, and provide valuable insights into the cellular and molecular mechanisms underlying AOP. In the long term, these findings may contribute to the identification of novel therapeutic targets for improving the clinical management of this prevalent pathology.

Albumins as Extracellular Protein Nanoparticles Collaborate with Plasma Ions to Control Biological Osmotic Pressure

Introduction

Plasma albumins as protein nanoparticles (PNs) exert essential functions in the control of biological osmotic pressure (OP), being involved in regulating water metabolism, cell morphology and cell tension. Understanding how plasma albumins and different electrolytes co-determine biological OP effects is crucial for correct interpretation of hemodynamic disorders, and practical treatment of hypo/hyper-proteinemia.

Methods

Optical measurement based on intermediate filament (IF) tension probe was used for real-time evaluation of transmembrane osmotic effects in live cells. Ion fluorescent probes were employed to evaluate intracellular ion levels, and a current clamp was used to measure membrane potential, thus exploring association of electrochemical and osmotic effects.

Results

Albumins are involved in regulation of intracellular osmolarity by a quantitative relationship. Extracellular PNs can alter membrane potentials by adsorbing counterions, induce production of intracellular PNs and further control the opening of ion channels and ion flow, contributing to electrochemical and osmotic re-equilibrium. Furthermore, various ions interplay with extracellular PNs, showing different osmotic effects: increased levels of calcium ions result in a hypotonic effect, whereas potassium ions induce hyper-osmolarity.

Conclusion

Extracellular PNs and Ca²⁺/K⁺ display antagonistic or synergetic effects in regulating biological OP. Live cells can spontaneously regulate osmotic effects through changing membrane potential and controlling intracellular ion content. Various plasma components need to be comprehensively analyzed, further developing a diagnostic index that considers the biological OP effects of various blood components and improves the evaluation of symptoms and diseases, such as calcium/potassium-hemodynamic disorders and edema.

Tension of plus-end tracking protein Clip170 confers directionality and aggressiveness during breast cancer migration

The microtubule (MT) plus-end binding protein Clip170 is associated closely with breast cancer invasion and migration. In this study, Clip170 tension observed by a newly designed cpstFRET tension probe was suggested to be positive related to breast cancer aggressiveness, which could be regulated by α-tubulin detyrosination-induced MT disassembly. Clip170 phosphorylation induced by Ribosomal protein S6 kinase (RSK) could also increase its tension and promote the conversion of a discrete comet-like Clip-170 distribution into a spotty pattern during cancer metastasis. Heightened Clip170 tension was correlated with the formation of cortactin-associated filopodia and lamellipodia, and then promoted invasion and metastasis both in vitro and in vivo. Meanwhile, Clip170 tension enhanced at the leading edge in directional migration, accompanying with IQGAP1 subcellular distribution variation. Our work indicates that the malignancy and directionality during breast cancer migration depend on the magnitude and polarization of Clip170 tension, and we suggest Clip170 tension as a new potential drug target for breast cancer therapy.

Par3 promotes breast cancer invasion and migration through pull tension and protein nanoparticle-induced osmotic pressure

Cancer cell invasion and metastasis are closely related to intracellular tension. The cell-polarity protein, Par3, is a mechanical transmitter that affects cytoskeletal forces and determines breast cancer aggressiveness. Increased Par3 tension caused by aPKC inactivation is involved in filopodia and lamellipodia formation. Blocking the connection between Par3 and aPKC increases breast cancer aggressiveness both in vitro and in vivo. Meanwhile, aPKC-induced Par3 cytoplasmic translocation results in JAM-A phase separation and microfilament depolymerization, which is associated with increased intracellular protein nanoparticle-induced osmotic pressure. This study demonstrated the effects of aPKC on Par3 tension and osmotic pressure in breast cancer metastasis, and introduced Par3-associated mechanical mechanisms as potential targets for breast cancer treatment.

Unraveling Axon Guidance during Axotomy and Regeneration

During neuronal development and regeneration axons extend a cytoskeletal-rich structure known as the growth cone, which detects and integrates signals to reach its final destination. The guidance cues “signals” bind their receptors, activating signaling cascades that result in the regulation of the growth cone cytoskeleton, defining growth cone advance, pausing, turning, or collapse. Even though much is known about guidance cues and their isolated mechanisms during nervous system development, there is still a gap in the understanding of the crosstalk between them, and about what happens after nervous system injuries. After neuronal injuries in mammals, only axons in the peripheral nervous system are able to regenerate, while the ones from the central nervous system fail to do so. Therefore, untangling the guidance cues mechanisms, as well as their behavior and characterization after axotomy and regeneration, are of special interest for understanding and treating neuronal injuries. In this review, we present findings on growth cone guidance and canonical guidance cues mechanisms, followed by a description and comparison of growth cone pathfinding mechanisms after axotomy, in regenerative and non-regenerative animal models.

Zi Qi Decoction Alleviates Liver Fibrosis by Inhibiting the Toll-Like Receptor 4 (TLR4)-Related Nuclear Factor kappa b (NF-κB) and Mitogen-Activated Protein Kinase (MAPK) Signaling Pathways

Background

Hepatic stellate cells (HSCs) play a vital role in hepatic fibrogenesis. Our recent clinical study indicated that the Zi Qi decoction, a Traditional Chinese Medicine formula, exhibited good efficacy in alleviating liver fibrosis, but the underlying mechanism remains elusive.

Material/Methods

Rats repeatedly injected with CCl₄ and cells stimulated with lipopolysaccharide were used as in vivo and in vitro models for liver fibrosis, respectively. The viability of LX-2 cells was evaluated with MTT assay. Relative messenger RNA (mRNA) expression of representative extracellular matrix (ECM) components was detected with real-time quantitative polymerase chain reaction (RT-qPCR). Moreover, total and phosphorylation levels of ECM proteins and pathway-related proteins were detected with western blotting. Immunofluorescent staining was used to show the nuclear translocation of nuclear factor kappa b (NF-κB) p65. Hematoxylin & eosin (H&E) and Masson trichrome staining and immunohistochemistry were performed to evaluate the extent of liver fibrosis. The levels of alanine transaminase (ALT), aspartate transaminase (AST), gamma-glutamyl transpeptidase (GGT), Hyp, tumor necrosis factor-α (TNF-α), and interleukin-6 (IL-6) were tested with an enzyme-linked immunosorbent assay. In addition, 7.0T micro-magnetic resonance imaging (micro-MRI) was used to evaluate the severity of hepatic damage.

Results

The Zi Qi decoction inhibited lipopolysaccharide-mediated upregulation of mRNA and protein levels of representative ECM proteins both in vivo and in vitro. The Zi Qi decoction also suppressed activation of the Toll-like receptor 4 (TLR4)-related NF-κB signaling pathway and subsequently inhibited the nuclear translocation of activated NF-κB. Moreover, another TLR4 downstream pathway, mitogen-activated protein kinase (MAPK), was simultaneously restrained. The results of liver pathology and MRI in rat models also suggested the efficacy of the Zi Qi decoction in attenuating liver damage.

Conclusions

The Zi Qi decoction inhibited liver fibrosis by inhibiting the TLR4-related NF-κB and MAPK signaling pathways and preventing activation of HSCs.

Positive effect of Astragaloside IV on neurite outgrowth via talin-dependent integrin signaling and microfilament force

Integrin plays a prominent role in neurite outgrowth by transmitting both mechanical and chemical signals. Integrin expression is closely associated with Astragaloside IV (AS-IV), the main component extracted from Astragali radix, which has a positive effect on neural-protection. However, the relationship between AS-IV and neurite outgrowth has not been studied exhaustively to date. The present study investigated the underlying mechanism of AS-IV on neurite outgrowth. Longer neurites have been observed in SH-SY5Y cells or cortical neurons after AS-IV treatment. Furthermore, AS-IV not only increased the expression of integrin β but also activated it. The AS-IV-induced increased integrin activity was attributed to the integrin-activating protein talin. Application of the actin force probe showed that AS-IV led to an increase in intracellular microfilament force during neurite growth. Furthermore, in response to AS-IV, the microfilament force was regulated by talin and integrin activity during neurite growth. These results suggest that AS-IV has the ability to increase intracellular structural force and facilitate neurite elongation by integrin signaling, which highlights its therapeutic potential for neurite outgrowth.

Protein Nanoparticle-Related Osmotic Pressure Modifies Nonselective Permeability of the Blood-Brain Barrier by Increasing Membrane Fluidity

BACKGROUND

Intracellular tension plays a crucial role in the destruction of the blood-brain barrier (BBB) in response to lesion stimuli. Tight junction structure could be primarily affected by tension activity. In this study, we aimed to determine the effects of extracellular BBB damage on intracellular tension activity, and elucidate the mechanism underlying the effects of intracellular protein nanoparticle-related osmotic pressure on BBB permeability.

METHODS

The intracellular tension for tight junction proteins occludin and ZO1 was evaluated using the fluorescence resonance energy transfer (FRET)-based tension probes and cpstFRET analysis. The changes in mobility ratios of occludin were evaluated via the fluorescence recovery after photobleaching (FRAP) test. The cytoplasmic osmotic pressure (OP) was measured using Osmometer. The count rate of cytoplasmic nanoparticles was detected by Nanosight NS300. The activation of cofilin and stathmin was examined by Western blot analysis. The BBB permeability in vivo was determined via the changes of Evans Blue (EB) injected into SD rats. The tight junction formation was assessed by the measurement of transendothelial electrical resistance (TEER). Intracellular calcium or chloride ions were measured using Fluo-4 AM or MQAE dyes.

RESULTS

BBB lesions were accompanied by changes in occludin/ZO1 tension. Increases in intracellular osmotic pressure were involved in alteration of BBB permeability, possibly through the depolymerization of microfilaments or microtubules and mass production of protein nanoparticles according to the Donnan effect. Recovery of protein nanoparticle-related osmotic pressure could effectively reverse the effects of changes in occludin/ZO1 tension under BBB lesions. Outward tension of intracellular osmotic potential also caused upregulation of membrane fluidity, which promoted nonselective drug influx.

CONCLUSION

Our results suggest a crucial mechanical mechanism underlying BBB lesions, and protein nanoparticle-related osmotic pressure could be a novel therapeutic target for BBB lesion-related brain diseases.

Mechanosensation in traumatic brain injury

Traumatic brain injury (TBI) is distinct from other neurological disorders because it is induced by a discrete event that applies extreme mechanical forces to the brain. This review describes how the brain senses, integrates, and responds to forces under both normal conditions and during injury. The response to forces is influenced by the unique mechanical properties of brain tissue, which differ by region, cell type, and sub-cellular structure. Elements such as the extracellular matrix, plasma membrane, transmembrane receptors, and cytoskeleton influence its properties. These same components also act as force-sensors, allowing neurons and glia to respond to their physical environment and maintain homeostasis. However, when applied forces become too large, as in TBI, these components may respond in an aberrant manner or structurally fail, resulting in unique pathological sequelae. This so-called "pathological mechanosensation" represents a spectrum of cellular responses, which vary depending on the overall biomechanical parameters of the injury and may be compounded by repetitive injuries. Such aberrant physical responses and/or damage to cells along with the resulting secondary injury cascades can ultimately lead to long-term cellular dysfunction and degeneration, often resulting in persistent deficits. Indeed, pathological mechanosensation not only directly initiates secondary injury cascades, but this post-physical damage environment provides the context in which these cascades unfold. Collectively, these points underscore the need to use experimental models that accurately replicate the biomechanics of TBI in humans. Understanding cellular responses in context with injury biomechanics may uncover therapeutic targets addressing various facets of trauma-specific sequelae.

Baicalein inhibits non-small-cell lung cancer invasion and metastasis by reducing ezrin tension in inflammation microenvironment

Baicalein, a flavonoid phytochemical, has been shown to be effective as an anti‐metastatic agent for various cancers, especially for non‐small‐cell lung cancer (NSCLC). However, the underlying mechanism of how baicalein targets cellular processes during NSCLC cell invasion and metastasis remains elusive. In this study, we found that non‐cytotoxic concentrations of baicalein still retained anti‐dissemination activity both in vitro and in vivo. Using a genetic encoding tension probe based on Förster resonance energy transfer (FRET) theory, baicalein was shown to significantly decrease ezrin tension by downregulating cellular ezrin S‐nitrosylation (SNO) levels in NSCLC cells in the inflammatory microenvironment. Decreased ezrin tension inhibited the formation of an aggressive phenotype of NSCLC cell and leader cell in collective migration, and subsequently suppressed NSCLC dissemination. Baicalein restrained SNO‐mediated ezrin tension by decreasing iNOS expression levels. Overall this study demonstrates the novel mechanism used by baicalein to suppress NSCLC invasion and metastasis from a mechanopharmacology perspective and illustrates a new direction for drug development.

Inward Tension of Talin and Integrin-related Osmotic Pressure are involved Synergetically in the Invasion and Metastasis of Non-small Cell Lung Cancer

The integrin receptor protein talin plays vital roles in intracellular chemical and mechanical activities, and it is implicated in the high invasion and poor prognosis of non-small cell lung cancer (NSCLC). To better understand the mechanism underlying the function of talin in NSCLC invasion and metastasis, a few newly designed tension probe based on Förster resonance energy transfer was used for real-time observation of tension changes in A549 cells. High NSCLC cell aggressiveness was found to be accompanied with inward talin and outward glial fibrillary acidic protein (GFAP) tensions, which are closely associated with microfilament (MF) force and intracellular osmotic potential. The increased osmotic pressure resulted from the production of intracellular protein nanoparticles and the related ion influx. Furthermore, integrin activation was found to adjust the talin and GFAP tensions. Disruption of the interaction between talin and MFs blocked the mechanical source of talin, reducing both talin tension and osmotic pressure and thus inhibiting NSCLC cell invasion and migration. Consequently, our study demonstrates that talin is involved in NSCLC invasion and migration via its inward tension and that the integrin pathway is correlated closely with protein-nanoparticle-induced outward osmotic pressure.

Regulation of ezrin tension by S-nitrosylation mediates non-small cell lung cancer invasion and metastasis

Cancer invasion and metastasis depend on accurate and rapid modulation of both chemical and mechanical activities. The S-nitrosylation (SNO) of membrane cytoskeletal cross-linker protein ezrin may regulate the malignant process in a tension-dependent manner. Methods: The level of nitrosylated ezrin in non-small cell lung cancer (NSCLC) tissues and A549 cell line were evaluated by biotin-switch assay. A few cysteine mutated plasmids of ezrin were used to identify active site for SNO. Newly designed ezrin or mutated-ezrin tension probes based on Förster resonance energy transfer (FRET) theory were applied to visually observe real-time tension changes. Cytoskeleton depolymerizing and motor molecular inhibiting experiments were performed to reveal the alternation of the mechanical property of ezrin after SNO. Transwell assays and xenograft mouse model were used to assess aggressiveness of A549 cells in different groups. Fluorescent staining was also applied to examine cellular location and structures. Results: High inducible nitric oxide synthase (iNOS) levels were observed to induce ezrin-SNO, and then promote malignant behaviors of NSCLC cells both in vitro and in vivo. Cys117 was identified as the only active site for ezrin-SNO. Meanwhile, an increased level of ezrin tension was observed after iNOS-induced SNO. Enhanced ezrin tension was positively correlated with aggressiveness of NSCLC. Moreover, Microfilament (MF) forces instead of microtubule (MT) forces played dominant roles in modulating ezrin tension, especially after ezrin nitrosylation. Conclusion: This study revealed a SNO-associated mechanism underlying the mechanical tension of ezrin. Ezrin-SNO promotes NSCLC cells invasion and metastasis through facilitating mechanical transduction from the cytoskeleton to the membrane. These studies implicate the therapeutic potential by targeting ezrin in the inhibition NSCLC invasion and metastasis.