How do neurons age?A focused review on the aging of the microtubular cytoskeleton

Aging is the leading risk factor for Alzheimer’s disease and other neurodegenerative diseases. We now understand that a breakdown in the neuronal cytoskeleton, mainly underpinned by protein modifications leading to the destabilization of microtubules, is central to the pathogenesis of Alzheimer’s disease. This is accompanied by morphological defects across the somatodendritic compartment, axon, and synapse. However, knowledge of what occurs to the microtubule cytoskeleton and morphology of the neuron during physiological aging is comparatively poor. Several recent studies have suggested that there is an age-related increase in the phosphorylation of the key microtubule stabilizing protein tau, a modification, which is known to destabilize the cytoskeleton in Alzheimer’s disease. This indicates that the cytoskeleton and potentially other neuronal structures reliant on the cytoskeleton become functionally compromised during normal physiological aging. The current literature shows age-related reductions in synaptic spine density and shifts in synaptic spine conformation which might explain age-related synaptic functional deficits. However, knowledge of what occurs to the microtubular and actin cytoskeleton, with increasing age is extremely limited. When considering the somatodendritic compartment, a regression in dendrites and loss of dendritic length and volume is reported whilst a reduction in soma volume/size is often seen. However, research into cytoskeletal change is limited to a handful of studies demonstrating reductions in and mislocalizations of microtubule-associated proteins with just one study directly exploring the integrity of the microtubules. In the axon, an increase in axonal diameter and age-related appearance of swellings is reported but like the dendrites, just one study investigates the microtubules directly with others reporting loss or mislocalization of microtubule-associated proteins. Though these are the general trends reported, there are clear disparities between model organisms and brain regions that are worthy of further investigation. Additionally, longitudinal studies of neuronal/cytoskeletal aging should also investigate whether these age-related changes contribute not just to vulnerability to disease but also to the decline in nervous system function and behavioral output that all organisms experience. This will highlight the utility, if any, of cytoskeletal fortification for the promotion of healthy neuronal aging and potential protection against age-related neurodegenerative disease. This review seeks to summarize what is currently known about the physiological aging of the neuron and microtubular cytoskeleton in the hope of uncovering mechanisms underpinning age-related risk to disease.

PCDH17 restricts dendritic spine morphogenesis by regulating ROCK2-dependent control of the actin cytoskeleton,modulating emotional behavior

Proper regulation of synapse formation and elimination is critical for establishing mature neuronal circuits and maintaining brain function.Synaptic abnormalities,such as defects in the density and morphology of postsynaptic dendritic spines,underlie the pathology of various neuropsychiatric disorders.Protocadherin 17(PCDH17)is associated with major mood disorders,including bipolar disorder and depression.However,the molecular mechanisms by which PCDH17 regulates spine number,morphology,and behavior remain elusive.In this study,we found that PCDH17 functions at postsynaptic sites,restricting the number and size of dendritic spines in excitatory neurons.Selective overexpression of PCDH17 in the ventral hippocampal CA1 results in spine loss and anxiety-and depression-like behaviors in mice.Mechanistically,PCDH17 interacts with actin-relevant proteins and regulates actin filament(F-actin)organization.Specifically,PCDH17 binds to ROCK2,increasing its expression and subsequently enhancing the activity of downstream targets such as LIMK1 and the phosphorylation of cofilin serine-3(Ser3).Inhibition of ROCK2 activity with belumosudil(KD025)ameliorates the defective F-actin organization and spine structure induced by PCDH17 overexpression,suggesting that ROCK2 mediates the effects of PCDH17 on F-actin content and spine development.Hence,these findings reveal a novel mechanism by which PCDH17 regulates synapse development and behavior,providing pathological insights into the neurobiological basis of mood disorders.

Scinderin promotes glioma cell migration and invasion via remodeling actin cytoskeleton

BACKGROUND Glioma is one of the most common intracranial tumors,characterized by invasive growth and poor prognosis.Actin cytoskeletal rearrangement is an essential event of tumor cell migration.The actin dynamics-related protein scinderin(SCIN)has been reported to be closely related to tumor cell migration and invasion in several cancers.AIM To investigate the role and mechanism of SCIN in glioma.METHODS The expression and clinical significance of SCIN in glioma were analyzed based on public databases.SCIN expression was examined using real-time quantitative polymerase chain reaction and Western blotting.Gene silencing was performed using short hairpin RNA transfection.Cell viability,migration,and invasion were assessed using cell counting kit 8 assay,wound healing,and Matrigel invasion assays,respectively.F-actin cytoskeleton organization was assessed using F-actin staining.RESULTS SCIN expression was significantly elevated in glioma,and high levels of SCIN were associated with advanced tumor grade and wild-type isocitrate dehydrogenase.Furthermore,SCIN-deficient cells exhibited decreased proliferation,migration,and invasion in U87 and U251 cells.Moreover,knockdown of SCIN inhibited the RhoA/focal adhesion kinase(FAK)signaling to promote F-actin depolymerization in U87 and U251 cells.CONCLUSION SCIN modulates the actin cytoskeleton via activating RhoA/FAK signaling,thereby promoting the migration and invasion of glioma cells.This study identified the cancer-promoting effect of SCIN and provided a potential therapeutic target for the treatment of glioma.

Regulation of actin cytoskeleton via photolithographic micropatterning

Actin cytoskeleton plays crucial roles in various cellular functions.Extracellular matrix(ECM)can modulate cell morphology by remodeling the internal cytoskeleton.To define how geometry of ECM regulates the organization of actin cytoskeleton,we plated individual NIH 3T3 cells on micropatterned substrates with distinct shapes and sizes.It was found that the stress fibers could form along the nonadhesive edges of T-shaped pattern,but were absent from the opening edge of V-shaped pattern,indicating that the organization of actin cytoskeleton was dependent on the mechanical environment.Furthermore,a secondary actin ring was observed on 50μm circular pattern while did not appear on 30μm and 40μm pattern,showing a size-dependent organization of actin cytoskeleton.Finally,osteoblasts,MDCK and A549 cells exhibited distinct organization of actin cytoskeleton on T-shaped pattern,suggesting a cell-type specificity in arrangement of actin cytoskeleton.Together,our findings brought novel insight into the organization of actin cytoskeleton on micropatterned environments.

Targeting cancer cytoskeleton: the mechanical properties of natural anticancerdrugs

Anticancer drugs are one of the most direct means of cancer therapy.However,the various cancer progressions hamper the development and discovery of anticancer drugs.In fact,the mechanical properties of the tumor cytoskeleton are extremely vital for any phase of cancer,especially in tumor invasion and metastasis.However,in the current category of anticancer drugs,the cytoskeleton-targeting drugs are limited and their role in tumor progression is unclear.Here,we present the mechanical characteristics of tumor stiffness that are tightly regulated by the cancer cytoskeleton,including actin filaments and microtubules during tumor initiation,growth and metastasis,and review the natural drugs that target the cancer cytoskeleton.We define cytoskeleton dynamics as target mechanisms for anticancer drugs and summarize the plant,microbial and marine sources of natural products.Furthermore,this paper also provides a material pathway to study active tumor mechanics,and introduces the unique advantages and future application potential of tumor cytoskeleton-targeting drugs in clinical use.The material approaches to active cancer mechanics are supplied in this review.We aim to promote the development of anticancer drugs that target tumor mechanics by using those material approaches and finding their pharmacological application.

The Change of Microtubule Cytoskeleton in the Stem-Tip Cells of Sugarcane during Mitosis

In order to understand the microtubule change of monocotyls stem-tip during mitosis, the arrangement, transformation of microtubule array and its relation with chromosome movement during mitosis were studied with freezing microtome, indirect immunofluoreseenee, DAPI staining and fluorescence microscopy. The results showed that nucleolus was intact when the cortical microtubules formed; cortical microtubules were changed into phramoplast microtubules bands at mitosis prophase. When phramoplast microtubules came into being, nuclear membrane was ruptured and chromosome was arranged at the position of cell plate ; subsequently, phramoplast microtubules were changed into phragmoplast microtubules, phramoplast microtubules were shortening and microtubules on the sides of cell plate were increasing gradually, during this course sister ehromatid was separated by microtubules at cell plate and tract to the two poles, forming phragmoplast microtubules. Then the nucleolus of two daughter cells formed and separated in the end with the increase of cells numbers. Therefore, cell division orientation could be judged from the arrangement of cell microtubules in different periods in order to understand its growth status.

Wnt/Fz signaling and the cytoskeleton： potential roles in tumorigenesis

Wnt/β-catenin regulates cellular functions related to tumor initiation and progression, cell proliferation, differ- entiation, survival, and adhesion, β-Catenin-independent Wnt pathways have been proposed to regulate cell polarity and migration, including metastasis. In this review, we discuss the possible roles of both β-catenin-dependent and -independent signaling pathways in tumor progression, with an emphasis on their regulation of Rho-family GTPases, cytoskeletal remodeling, and relationships with cell-cell adhesion and cilia/ciliogenesis.

VISUALIZATION OF DYNAMIC ORGANIZATION OF CYTOSKELETON GELS IN LIVING CELLS BY HYBRID-SPM

We succeeded in performing of hybrid Scanning Probe Microscopy (hybrid-SPM) in which mechanical-SPM andfluorescence microscopy are combined. This technique is able to measure simultaneously mechanical properties anddistribution of cytoskeletons of living cells by using green fluorescent protein. We measured evolution of both local elasticityand distributions of actin stress fibers in an identical fibroblast living in physiological conditions. The SPM experimentsrevealed that stiffer lines develop in living cells, which correspond to actin stress fibers. The elasticity of the actin stressfibers is as high as 100 kPa. We discuss mechanical effects on the development of actin filament networks.

Heavy ion and X-ray irradiation alter the cytoskeleton and cytomechanics of cortical neurons

Heavy ion beams with high linear energy transfer exhibit more beneifcial physical and biological performance than conventional X-rays, thus improving the potential of this type of radiotherapy in the treatment of cancer. However, these two radiotherapy modalities both cause inevitable brain injury. The objective of this study was to evaluate the effects of heavy ion and X-ray irra-diation on the cytoskeleton and cytomechanical properties of rat cortical neurons, as well as to determine the potential mechanism of neuronal injury after irradiation. Cortical neurons from 30 new-born mice were irradiated with heavy ion beams at a single dose of 2 Gy and X-rays at a single dose of 4 Gy;subsequent evaluation of their effects were carried out at 24 hours after irradiation. An immunolfuorescence assay showed that after irradiation with both the heavy ion beam and X-rays, the number of primary neurons was signiifcantly decreased, and there was ev-idence of apoptosis. Radiation-induced neuronal injury was more apparent after X-irradiation. Under atomic force microscopy, the neuronal membrane appeared rough and neuronal rigidity had increased. These cell changes were more apparent following exposure to X-rays. Our ifnd-ings indicated that damage caused by heavy ion and X-ray irradiation resulted in the structural distortion and rearrangement of the cytoskeleton, and affected the cytomechanical properties of the cortical neurons. Moreover, this radiation injury to normal neurons was much severer after irradiation with X-rays than after heavy ion beam irradiation.

Effect of aging on cytoskeleton system of Kupffer cell and its phagocytic capacity

IM To investigate the agerelated alterations of cytoskeleton system in liver Kupffer cell and their relation to the changed phagocytic function.METHODS The phagocytic function of Kupffer cells from rats of various ages (6mo, 12mo, 18mo and 24mo) were quantitatively evaluated by phagocytosis of polystyrene beads. The actin distribution and measurement of Kupffer cell were determined by a phalloidinTRITC method; and the myosin and vimentin distribution and measurement with indirect immunochemical staining.RESULTS Aging resulted in significant alterations of actin, myosin and vimentin distributions and reductions in Kupffer cell; the 3 cytoskeleton components of 24moold Kupffer cell were significantly decreased to 680%, 849% and 755%, respectively of these of 6moold Kupffer cell(P<001,001 and 001). And these decreases had significant positive relations with the damaged phagocytosis of the aged Kupffer cell. γ values were 096(P<005), 099(P<001) and 095 (P<005) respectively.CONCLUSION The cytoskeleton system of the aged Kupffer cell presents an evident state of senescence, which may be an important mechanism of decreased phagocytosis of the aged Kupffer cell..

Cytoskeleton reorganization and ultrastructural damage induced by gliadin in a three-dimensional in vitro model

AIM： To evaluate the interplay between gliadin and LoVo cells and the direct effect of gliadin on cytoskeletal patterns.METHODS： We treated LoVo multicellular spheroids with digested bread wheat gliadin in order to investigate their morphology and ultrastructure （by means of light microscopy and scanning electron microscopy）, and the effect of gliadin on actin （phalloidin fluorescence） and the tight-junction protein occludin and zonula occluden-1.RESULTS： The treated spheroids had deep holes and surface blebs, whereas the controls were smoothly surfaced ovoids. The incubation of LoVo spheroids with gUadin decreased the number of intracellular actin filaments, impaired and disassembled the integrity of the tight-junction system.CONCLUSION： Our data obtained from an ＂in vivolike＂ polarized culture system confirm the direct noxious effect of gliadin on the cytoskeleton and tight junctions of epithelial cells. Unlike two-dimensional cell culture systems, the use of multicellular spheroids seems to provide a suitable model for studying cell-cell interactions.

A new interaction between Abi-1 and βPIX involved in PDGF-activated actin cytoskeleton reorganisation

Members of the Rho family of GTPases are key regulators of the actin cytoskeleton. In particular, activated Racl stimulates membrane dorsal ruffle formation in response to platelet-derived growth factor （PDGF）. Abl-interactor （Abi）- 1 and βP1X, a guanine nucleotide exchange factor for Racl, localise at these Rac1-induced actin structures and play important roles in the induction of membrane dorsal ruffling in response to PDGF in fibroblasts. Here, we demonstrate a novel interaction between Abi-1 and βPIX using the yeast two-hybrid system, in vitro pull-down assays, and in vivo co-immunoprecipitation experiments. In vitro, the C-terminal fragment of βPIX interacted with Abi-1, while in vivo the N-terminal fragment of βPIX interacted with Abi-1. The biological function of this interaction was investigated in mouse fibroblasts in response to PDGF stimulation. Abi-1 and βPIX co-localised in the cytoplasm and to membrane dorsal ruffles after PDGF treatment. We show that the co-expression of Abi-1 and truncated forms of βPIX in mouse fibroblasts blocked PDGF-induced membrane dorsal ruffles. Together, these results show that the interaction between Abi-1 and βPIX is involved in the formation of growth factor-induced membrane dorsal ruffles.

Ion Implantation Hampers Pollen Tube Growth and Disrupts Actin Cytoskeleton Organization in Pollen Tubes of Pinus thunbergii

Pollen grains of Pinus thunbergii Parl. （Japanese black pine） were implanted with 30 keV nitrogen ion beams and the effects of nitrogen ion implantation on pollen tube growth in vitro and the organization of actin cytoskeleton in the pollen tube cell were investigated using a confocal laser scanning microscope after fluorescence labeling. Treatment with ion implantation significantly blocked pollen tube growth. Confocal microscopy showed that ion implantation disrupted actin filament cytoskeleton organization in the pollen tube. It was found that there was a distinct correlation between the inhibition of pollen tube growth and the disruption of actin cytoskeleton organization, indicating that an intact actin cytoskeleton is essential for continuous pollen tube elongation in Pinus thunbergii. Although the detailed mechanism for the ion-implantation-induced bioeffect still remains to be elucidated, the present study assumes that the cytoskeleton system in pollen grains may provide a key target in response to ion beam implantation and is involved in mediating certain subsequent cytological changes.

Effects of polar cortical cytoskeleton and unbalanced cortical surface tension on intercellular bridge thinning during cytokinesis

To probe the contributions of polar cortical cytoskeleton and the surface tension of daughter cells to intercellular bridge thinning dynamics during cytokinesis,we applied cytochalasin D（CD） or colchicine（COLC） in a highly localized manner to polar regions of dividing normal rat kidney（NRK） cells.We observed cellular morphological changes and analyzed the intercellular bridge thinning trajectories of dividing cells with different polar cortical characteristics.Global blebbistatin（BS） application was used to obtain cells losing active contractile force groups.Our results show that locally released CD or colchicine at the polar region caused inhibition of cytokinesis before ingression.Similar treatment at phases after ingression allowed completion of cytokinesis but dramatically influenced the trajectories of intercellular bridge thinning.Disturbing single polar cortical actin induced transformation of the intercellular bridge thinning process,and polar cortical tension controlled deformation time of intercellular bridges.Our study provides a feasible framework to induce and analyze the effects of local changes in mechanical properties of cellular components on single cellular cytokinesis.

The roles of focal adhesion and cytoskeleton systems in fluid shearstress-induced endothelial cell response

Focal adhesions are polyproteins linked to extracellular matrix and cytoskeleton,which play an important role in the process of transforming force signals into intracellular chemical signals and subsequently triggering related physiological or pathological reactions.The cytoskeleton is a network of protein fibers in the cytoplasm,which is composed of microfilaments,microtubules,intermediate filaments,and cross-linked proteins.It is a very important structure for cells to maintain their basic morphology.This review summarizes the process of fluid shear stress transduction mediated by focal adhesion and the key role of the cytoskeleton in this process,which focuses on the focal adhesion and cytoskeleton systems.The important proteins involved in signal transduction in focal adhesion are introduced emphatically.The relationship between focal adhesion and mechanical transduction pathways are discussed.In this review,we discuss the relationship between fluid shear stress and associated diseases such as atherosclerosis,as well as its role in clinical research and drug development.

Distribution pattern of axonal cytoskeleton proteins in the human optic nerve head

Glaucoma is one of the leading causes of blindness in the developed world.It is a progressive optic neuropathy where structural loss of retinal ganglion cell（RGC）axons corresponds with functional visual field defect.Glaucoma is distinguished from other optic neuropathies by its selective loss of RGC axons.Superior and inferior peripheral nerve sectors are found to be most vulnerable to pressure induced injury whereas the inner temporal sector is most resilient（Quigley et al.,1988）.

Yiqi Huoxue Decoction modifies the expression of myocardial cytoskeleton-associated proteins by regulating the AMPK signaling pathway in H9c2 cells exposed to hypoxic conditions

Background:In myocardial ischemia,hypoxia leads to destruction of the cytoskeleton,and especially the imbalance of microtubule polymerization-depolymerization,which seriously affects the structure and function of cardiomyocytes.We previously showed that a Yiqi Huoxue Decoction (YQHX) improves mitochondrial function and decreases anti-oxidative effects in hypoxia-induced H9c2 cell injury.Therefore,in this study we investigated whether YQHX protects against hypoxia-induced damage by decreasing damage to the cardiac cytoskeleton.Methods:After reaching 70%-80% confluence,H9c2 cells were synchronized in serum-free Dulbecco's Modified Eagle Medium for 6 hours,then divided into control,model,and YQHX (100,200,400 μg/mL) groups,which were then grown in a hypoxic atmosphere for 12 hours.Cardiac cell viability was assessed using an xCELLigence system.The levels of lactate dehydrogenase,maleic dialdehyde,and superoxide dismutase in H9c2 cell supernatants were measured.Hoechst 33258 staining was employed to observe cardiac cell apoptosis.Confocal microscopy,immunofluorescence,and western blot analysis were performed to evaluate the protective effects of the YQHX against hypoxia-induced injury in the H9c2 cell line.Results:Cells that were pretreated with YQHX were more able to maintain their microtubule structure in the early stages of hypoxia and had better myocardial fitness in response to hypoxia compared with cells that were not pretreated.However,hypoxia-induced upregulation of α-tubulin and β-tubulin expression antagonized the protective effect of YQHX (100 μg/mL).In addition,YQHX (100 μg/mL) treatment significantly upregulated MAP4 protein expression (P =.003) and downregulated p-AMPKα protein expression (P <.001) compared with the model group.Conclusion:The results indicate that YQHX plays a role in protecting against oxidative stress injury and apoptosis in H9c2 cells.Notably,our results suggested that the YQHX could mitigate the damage to the cardiac cytoskeleton and the dysregulation of AMPK-related protein signaling pathways that are induced by hypoxia.

Effects of Fumonisin B1 on Biomechanics and Cytoskeleton of Human Umbilical Vein Endothelial Cells

Objective Fumonisin B1(FB1)is an important mycotoxin in nature worldwide.The biomechanical properties of cells are closely related to their structure and function,and the cytoskeleton is the structural and functional basis of cells motility,and therefore,from a biomechanical point of view,the purpose of this study is to investigate the effects of FB1 on the biomechanical properties,migration capacity and cytoskeletal structure of human umbilical vein endothelial cells(HUVECs),which may lay an experimental foundation for further exploration of the toxicity mechanism of fumonisin.Methods HUVECs were cultured and treated with different concentrations of FB1.Then,CCK-8 kit was used to detect the effect of FB1 on the survival rate.The osmotic fragility of the cells was measured after treatment with different osmotic pressures for30 min.The cell membrane fluidity was measured by fluorescence polarization method.The cell electrophoretic mobility was measured by cell electrophoretic apparatus.The migration capacity of the cells was observed by scratch repair assay.The changes of reactive oxygen species and cytoskeletal structure were observed by confocal laser scanning microscopy.Finally,the mRNA and protein relative expression levels of cytoskeletal binding proteins were detected by real-time PCR,Western blotting and confocal laser scanning.Results The results of CCK-8 showed that FB1 could significantly inhibit the proliferation of HUVECs in a dose-and time-dependent manner.After treatment of HUVECs with FB1,the hypotonic resistance of the cell,cell surface charge,cell membrane fluidity and migration capacity were all weakened,while reactive oxygen species were significantly increased and the cytoskeletal structure was significantly reorganized.Furthermore,RTPCR results showed that the mRNA relative expression levels of cytoskeletal binding proteins,exception of actin,were down-regulated after treated with FB1.Besides,Western blotting and statistical analysis based on fluorescence intensity of laser confocal microscopy confirmed theses changes in protein level.Conclusions FB1 can significantly affect the biomechanical properties and motility of HUVECs,which may be directly correlated to the remodel of F-actin cytoskeleton,as well as the relative expression changes of cytoskeletal binding proteins.It is significant for further exploring the toxicity mechanism of fumonisin.

Tmod1 Affects the Immune Functions and Biophysical Properties of Dendritic Cells Through TLR4 Signaling Pathway and Cytoskeleton Remodeling

Background Dendritic cells(DCs)are the most important antigen-presenting cells due to their professional and extremely efficient antigen-presenting function.The dynamics of cytoskeleton plays crucial regulated roles on DCs’immune functions and biophysical properties.Several evidences show that tumor-derived suppressive cytokines deteriorate DCs’immune functions through remodeling their F-actin cytoskeleton.But the underlying mechanism is still elusive.Tropomodulin1(Tmod1),a cytoskeleton-binding protein,regulates and stabilizes actin filaments lengths and cytoskeleton architecture,which involves in the regulations of the morphology,formation of neural dendrites and biophysical properties of cells.Our previous studies found that mature DCs(mDCs)had a higher expression of Tmod1 than immature DCs(imDCs). Therefore,it’s hypothesized that Tmod1 maybe involve in the modification of DCs’functions.Objective The aim of the study is to investigate the effects of Tmodl on the immune functions and biophysical properties of DCs and the underlying mechanisms in order to further understand the biological behaviors of DCs.Methods Bone marrow-derived cells were harvested from wild type(C57BL/6 J)mice and Tmod1 knockout mice(Tmod1 overexpressing transgenic(TOT)/Tmod1-/-)and differentiated to immature dendritic cells(imDCs)by rmGM-CSF and rmIL-4.imDCs were then matured by lipopolysaccharides(LPS)treatment.The expressions of the surface markers in DCs,including CD80,CD86,CD40,MHC-Ⅱand CCR7,were detected by flow cytometry,Western blot and qRT-PCR.The inflammation cytokines such as IL-6,IFN-γ,IFN-βand IL-10 were also detected by flow cytometry.The immune functions and the biophysical properties of DCs were compared between the wild type and Tmod1 knockout mice.The F-actin content and dendritic pseudopodia of these two kinds of DCs were detected by flow cytometry and laser scanning confocal microscope respectively.Finally,we detected the MyD88 dependent and independent signaling pathway to discover the molecular mechanisms.Results We found that Tmod1-deficient mDCs showed deficient antigen-presenting ability and they failed to express enough MHC-Ⅱ,co-stimulated molecules(CD80/86,CD40)and CCR7 on their cell surface.The secretions of the inflammatory cytokines IL-6 and IFN-γwere decreased while the anti-inflammatory cytokines IFN-βand IL-10 were increased in the supernatant of Tmod1-deficient mDCs.As compared to DCs of wild type mice,the migration ability of DCs from Tmod1 knockout mice were dramatically damaged including their free migration and CCL19 mediated chemotaxis migration.However,we found that Tmod1 knockout had no effects on the imDCs’endocytosis ability.Furthermore,Tmod1 knockout DCs showed higher osmotic fragility,lower Young’s modulus,less F-actin content and shorter dendritic pseudopodia.Under LPS stimulation,the phosphorylation level of p65 and p38 were significantly downregulated in Tmod1 knockout mice while the expression of p-IRF3 was upregulated.Conclusions These results indicated that Tmodl knockout leads to deficient antigen-presenting ability and impaired migration of DCs as well as their biophysical properties.The underlying mechanisms are due to the inhibitions of the TLR4-mediated NF-κB and p38 MAPK singling pathway and the activation of the IRF3 signaling pathway,as well as the disturbed reorganization of the F-actin cytoskeleton.Our results provide a new insight on the functions of Tmod1 which can affect the DCs’immune functions and biophysical properties through regulating the TLR4-mediated singling pathways and cytoskeleton remodeling.

Hsp90 inhibition induces destabilization of actin cytoskeleton in tumor cells:functional significance of Hsp90 interaction with F-actin

Objective:To examine the role of heat shock protein 90(Hsp90) in the maintenance of actin cytoskeleton in human neuroblastoma tumor cells.Methods:Co-precipitation experiments were performed to examine Hsp90 interaction with actin.Hsp90 and actin interactions were evaluated by protein refolding and acto-myosin motility assays.17-(AUylamino)-17- demethoxygeldanamycin(17AAG) induced actin-cytoskeleton re-organization was examined by laser scanning confocal microcopy.Results:It was shown that inhibition of Hsp90 by 17AAC accelerates detergent induced cell lysis of neuroblastoma tumor cells through destabilization of actin cytoskeleton.The in vitro co-precipitation experiments showed that functional but not mutant Hsp90 binds with F-actin.Among biochemical modifications,phopshorylation and oligomerization enhanced Hsp90 binding with F-actin.F-actin binding to Hsp90 interfered with Hsp90 chaperone activity in protein refolding assays,and Hsp90 binding to F-actin interfered with actin motility on myosin coated flow cell.In the combination treatment,17AAG irreversibly augmented the effect of cytochalasin D,an inhibitor of actin polymerization.Conclusions:It can be concluded that Hsp90 binds to F-actin in tumor cells and maintains the cellular integrity. The results display a novel element of Hsp90 inhibition in destabilizing the actin cytoskeleton of tumor cells,therefore suggest that 17AAG combination with cytoskeletal disruptor may be effective in combating cancer.