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1.
Cell ; 185(19): 3588-3602.e21, 2022 Sep 15.
Artigo em Inglês | MEDLINE | ID: mdl-36113429

RESUMO

The current dogma of RNA-mediated innate immunity is that sensing of immunostimulatory RNA ligands is sufficient for the activation of intracellular sensors and induction of interferon (IFN) responses. Here, we report that actin cytoskeleton disturbance primes RIG-I-like receptor (RLR) activation. Actin cytoskeleton rearrangement induced by virus infection or commonly used reagents to intracellularly deliver RNA triggers the relocalization of PPP1R12C, a regulatory subunit of the protein phosphatase-1 (PP1), from filamentous actin to cytoplasmic RLRs. This allows dephosphorylation-mediated RLR priming and, together with the RNA agonist, induces effective RLR downstream signaling. Genetic ablation of PPP1R12C impairs antiviral responses and enhances susceptibility to infection with several RNA viruses including SARS-CoV-2, influenza virus, picornavirus, and vesicular stomatitis virus. Our work identifies actin cytoskeleton disturbance as a priming signal for RLR-mediated innate immunity, which may open avenues for antiviral or adjuvant design.


Assuntos
Actinas , COVID-19 , Citoesqueleto de Actina , Antivirais , Humanos , Interferons , Ligantes , Proteína Fosfatase 1 , RNA , RNA Helicases , SARS-CoV-2
2.
Cell ; 185(19): 3638-3638.e1, 2022 Sep 15.
Artigo em Inglês | MEDLINE | ID: mdl-36113430

RESUMO

Cells are continuously exposed to tissue-specific extrinsic forces that are counteracted by cell-intrinsic force generation through the actomyosin cytoskeleton and alterations in the material properties of various cellular components, including the nucleus. Forces impact nuclei both directly through inducing deformation, which is sensed by various mechanosensitive components of the nucleus, as well as indirectly through the actomyosin cytoskeleton and mechanosensitive pathways activated in the cytoplasm. To view this SnapShot, open or download the PDF.


Assuntos
Actomiosina , Mecanotransdução Celular , Citoesqueleto de Actina/metabolismo , Actomiosina/metabolismo , Núcleo Celular/metabolismo , Citoesqueleto/metabolismo , Mecanotransdução Celular/fisiologia
3.
J Gen Physiol ; 154(10)2022 Oct 03.
Artigo em Inglês | MEDLINE | ID: mdl-36053243

RESUMO

The ß-myosin heavy chain expressed in ventricular myocardium and the myosin heavy chain (MyHC) in slow-twitch skeletal Musculus soleus (M. soleus) type-I fibers are both encoded by MYH7. Thus, these myosin molecules are deemed equivalent. However, some reports suggested variations in the light chain composition between M. soleus and ventricular myosin, which could influence functional parameters, such as maximum velocity of shortening. To test for functional differences of the actin gliding velocity on immobilized myosin molecules, we made use of in vitro motility assays. We found that ventricular myosin moved actin filaments with ∼0.9 µm/s significantly faster than M. soleus myosin (0.3 µm/s). Filaments prepared from isolated actin are not the native interaction partner of myosin and are believed to slow down movement. Yet, using native thin filaments purified from M. soleus or ventricular tissue, the gliding velocity of M. soleus and ventricular myosin remained significantly different. When comparing the light chain composition of ventricular and M. soleus ß-myosin, a difference became evident. M. soleus myosin contains not only the "ventricular" essential light chain (ELC) MLC1sb/v, but also an additional longer and more positively charged MLC1sa. Moreover, we revealed that on a single muscle fiber level, a higher relative content of MLC1sa was associated with significantly slower actin gliding. We conclude that the ELC MLC1sa decelerates gliding velocity presumably by a decreased dissociation rate from actin associated with a higher actin affinity compared to MLC1sb/v. Such ELC/actin interactions might also be relevant in vivo as differences between M. soleus and ventricular myosin persisted when native thin filaments were used.


Assuntos
Actinas , Cadeias Leves de Miosina , Citoesqueleto de Actina/metabolismo , Actinas/metabolismo , Cadeias Pesadas de Miosina/metabolismo , Miosinas Ventriculares
4.
Phys Rev Lett ; 129(8): 088101, 2022 Aug 19.
Artigo em Inglês | MEDLINE | ID: mdl-36053696

RESUMO

Self-organized patterns in the actin cytoskeleton are essential for eukaryotic cellular life. They are the building blocks of many functional structures that often operate simultaneously to facilitate, for example, nutrient uptake and movement of cells. However, identifying how qualitatively distinct actin patterns can coexist remains a challenge. Using bifurcation theory of a mass conserved activator-inhibitor system, we uncover a generic mechanism of how different actin waves-traveling waves and excitable pulses-organize and simultaneously emerge. Live-cell imaging experiments indeed reveal that narrow, planar, and fast-moving excitable pulses may coexist with ring-shaped macropinocytic actin waves in the cortex of motile amoeboid cells.


Assuntos
Actinas , Dictyostelium , Citoesqueleto de Actina , Membrana Celular , Movimento
5.
Proc Natl Acad Sci U S A ; 119(37): e2205370119, 2022 Sep 13.
Artigo em Inglês | MEDLINE | ID: mdl-36067297

RESUMO

To orchestrate cell mechanics, trafficking, and motility, cytoskeletal filaments must assemble into higher-order networks whose local subcellular architecture and composition specify their functions. Cross-linking proteins bridge filaments at the nanoscale to control a network's µm-scale geometry, thereby conferring its mechanical properties and functional dynamics. While these interfilament linkages are key determinants of cytoskeletal function, their structural mechanisms remain poorly understood. Plastins/fimbrins are an evolutionarily ancient family of tandem calponin-homology domain (CHD) proteins required to construct multiple classes of actin networks, which feature diverse geometries specialized to power cytokinesis, microvilli and stereocilia biogenesis, and persistent cell migration. Here, we focus on the structural basis of actin network assembly by human T-plastin, a ubiquitously expressed isoform necessary for the maintenance of stable cellular protrusions generated by actin polymerization forces. By implementing a machine-learning-enabled cryo-electron microscopy pipeline for visualizing cross-linkers bridging multiple filaments, we uncover a sequential bundling mechanism enabling T-plastin to bridge pairs of actin filaments in both parallel and antiparallel orientations. T-plastin populates distinct structural landscapes in these two bridging orientations that are selectively compatible with actin networks featuring divergent architectures and functions. Our structural, biochemical, and cell biological data highlight inter-CHD linkers as key structural elements underlying flexible but stable cross-linking that are likely to be disrupted by T-plastin mutations that cause hereditary bone diseases.


Assuntos
Actinas , Glicoproteínas de Membrana , Proteínas dos Microfilamentos , Citoesqueleto de Actina/metabolismo , Actinas/química , Microscopia Crioeletrônica , Humanos , Glicoproteínas de Membrana/química , Proteínas dos Microfilamentos/química , Polimerização
6.
J Vis Exp ; (186)2022 08 25.
Artigo em Inglês | MEDLINE | ID: mdl-36094259

RESUMO

The composite cytoskeleton, comprising interacting networks of semiflexible actin filaments and rigid microtubules, restructures and generates forces using motor proteins such as myosin II and kinesin to drive key processes such as migration, cytokinesis, adhesion, and mechanosensing. While actin-microtubule interactions are key to the cytoskeleton's versatility and adaptability, an understanding of their interplay with myosin and kinesin activity is still nascent. This work describes how to engineer tunable three-dimensional composite networks of co-entangled actin filaments and microtubules that undergo active restructuring and ballistic motion, driven by myosin II and kinesin motors, and are tuned by the relative concentrations of actin, microtubules, motor proteins, and passive crosslinkers. Protocols for fluorescence labeling of the microtubules and actin filaments to most effectively visualize composite restructuring and motion using multi-spectral confocal imaging are also detailed. Finally, the results of data analysis methods that can be used to quantitatively characterize non-equilibrium structure, dynamics, and mechanics are presented. Recreating and investigating this tunable biomimetic platform provides valuable insight into how coupled motor activity, composite mechanics, and filament dynamics can lead to myriad cellular processes from mitosis to polarization to mechano-sensation.


Assuntos
Actinas , Cinesinas , Citoesqueleto de Actina/metabolismo , Actinas/metabolismo , Citoesqueleto/metabolismo , Dineínas/metabolismo , Microtúbulos/metabolismo , Miosinas/metabolismo
7.
J Vis Exp ; (186)2022 08 25.
Artigo em Inglês | MEDLINE | ID: mdl-36094272

RESUMO

The actin cytoskeleton, the principal mechanical machinery in the cell, mediates numerous essential physical cellular activities, including cell deformation, division, migration, and adhesion. However, studying the dynamics and structure of the actin network in vivo is complicated by the biochemical and genetic regulation within live cells. To build a minimal model devoid of intracellular biochemical regulation, actin is encapsulated inside giant unilamellar vesicles (GUVs, also called liposomes). The biomimetic liposomes are cell-sized and facilitate a quantitative insight into the mechanical and dynamical properties of the cytoskeleton network, opening a viable route for bottom-up synthetic biology. To generate liposomes for encapsulation, the inverted emulsion method (also referred to as the emulsion transfer method) is utilized, which is one of the most successful techniques for encapsulating complex solutions into liposomes to prepare various cell-mimicking systems. With this method, a mixture of proteins of interest is added to the inner buffer, which is later emulsified in a phospholipid-containing mineral oil solution to form monolayer lipid droplets. The desired liposomes are generated from monolayer lipid droplets crossing a lipid/oil-water interface. This method enables the encapsulation of concentrated actin polymers into the liposomes with desired lipid components, paving the way for in vitro reconstitution of a biomimicking cytoskeleton network.


Assuntos
Actinas , Lipossomas Unilamelares , Citoesqueleto de Actina/metabolismo , Actinas/metabolismo , Emulsões/química , Fosfolipídeos/metabolismo , Lipossomas Unilamelares/química
8.
Methods Mol Biol ; 2478: 677-700, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-36063338

RESUMO

The eukaryotic cytoskeleton consists of three different types of biopolymers - microtubules, actin filaments, and intermediate filaments - and provides cells with versatile mechanical properties, combining stability and flexibility. The unique molecular structure of intermediate filaments leads to high extensibility and stability under load. With high laser power dual optical tweezers, the mechanical properties of intermediate filaments may be investigated, while monitoring the extension with fluorescence microscopy. Here, we provide detailed protocols for the preparation of single vimentin intermediate filaments and general measurement protocols for (i) stretching experiments, (ii) repeated loading and relaxation cycles, and (iii) force-clamp experiments. We describe methods for the analysis of the experimental data in combination with computational modeling approaches.


Assuntos
Citoesqueleto , Filamentos Intermediários , Citoesqueleto de Actina , Filamentos Intermediários/química , Microtúbulos , Vimentina/química
9.
J Nanobiotechnology ; 20(1): 406, 2022 Sep 08.
Artigo em Inglês | MEDLINE | ID: mdl-36076230

RESUMO

Nanofabrication technologies have been recently applied to the development of engineered nano-bio interfaces for manipulating complex cellular processes. In particular, vertically configurated nanostructures such as nanoneedles (NNs) have been adopted for a variety of biological applications such as mechanotransduction, biosensing, and intracellular delivery. Despite their success in delivering a diverse range of biomolecules into cells, the mechanisms for NN-mediated cargo transport remain to be elucidated. Recent studies have suggested that cytoskeletal elements are involved in generating a tight and functional cell-NN interface that can influence cargo delivery. In this study, by inhibiting actin dynamics using two drugs-cytochalasin D (Cyto D) and jasplakinolide (Jas), we demonstrate that the actin cytoskeleton plays an important role in mRNA delivery mediated by silicon nanotubes (SiNTs). Specifically, actin inhibition 12 h before SiNT-cellular interfacing (pre-interface treatment) significantly dampens mRNA delivery (with efficiencies dropping to 17.2% for Cyto D and 33.1% for Jas) into mouse fibroblast GPE86 cells, compared to that of untreated controls (86.9%). However, actin inhibition initiated 2 h after the establishment of GPE86 cell-SiNT interface (post-interface treatment), has negligible impact on mRNA transfection, maintaining > 80% efficiency for both Cyto D and Jas treatment groups. The results contribute to understanding potential mechanisms involved in NN-mediated intracellular delivery, providing insights into strategic design of cell-nano interfacing under temporal control for improved effectiveness.


Assuntos
Actinas , Nanotubos , Citoesqueleto de Actina/metabolismo , Actinas/metabolismo , Animais , Citocalasina D/farmacologia , Mecanotransdução Celular , Camundongos , RNA Mensageiro , Silício/química
10.
Proc Natl Acad Sci U S A ; 119(38): e2122969119, 2022 Sep 20.
Artigo em Inglês | MEDLINE | ID: mdl-36095209

RESUMO

Energy is essential for all cellular functions in a living organism. How cells coordinate their physiological processes with energy status and availability is thus an important question. The turnover of actin cytoskeleton between its monomeric and filamentous forms is a major energy drain in eukaryotic cells. However, how actin dynamics are regulated by ATP levels remain largely unknown in plant cells. Here, we observed that seedlings with impaired functions of target of rapamycin complex 1 (TORC1), either by mutation of the key component, RAPTOR1B, or inhibition of TOR activity by specific inhibitors, displayed reduced sensitivity to actin cytoskeleton disruptors compared to their controls. Consistently, actin filament dynamics, but not organization, were suppressed in TORC1-impaired cells. Subcellular localization analysis and quantification of ATP concentration demonstrated that RAPTOR1B localized at cytoplasm and mitochondria and that ATP levels were significantly reduced in TORC1-impaired plants. Further pharmacologic experiments showed that the inhibition of mitochondrial functions led to phenotypes mimicking those observed in raptor1b mutants at the level of both plant growth and actin dynamics. Exogenous feeding of adenine could partially restore ATP levels and actin dynamics in TORC1-deficient plants. Thus, these data support an important role for TORC1 in coordinating ATP homeostasis and actin dynamics in plant cells.


Assuntos
Proteínas de Arabidopsis , Arabidopsis , Citoesqueleto de Actina , Actinas , Trifosfato de Adenosina , Arabidopsis/genética , Proteínas de Arabidopsis/genética , Alvo Mecanístico do Complexo 1 de Rapamicina , Fosfatidilinositol 3-Quinases
11.
STAR Protoc ; 3(3): 101588, 2022 Sep 16.
Artigo em Inglês | MEDLINE | ID: mdl-35990744

RESUMO

Here, we describe a protocol to culture Drosophila S2R+ cells and to extract plasmatocytes from adult flies. The modified seeding approach detailed here, in combination with coating of coverslips with concanvalin A, enables enhanced adhesion and spreading of cells. We describe the steps for confocal microscopy and a detailed quantification pipeline to evaluate changes in cortical actin cytoskeleton dynamics. The protocol can be applied to a variety of genetic or chemical perturbations. For complete details on the use and execution of this protocol, please refer to Nath et al. (2022).


Assuntos
Citoesqueleto de Actina , Drosophila , Animais , Técnicas de Cultura de Células , Microscopia Confocal
12.
Cell Rep ; 40(9): 111261, 2022 Aug 30.
Artigo em Inglês | MEDLINE | ID: mdl-36044862

RESUMO

Compelling evidence indicates that in Huntington's disease (HD), mutation of huntingtin (HTT) alters several aspects of early brain development such as synaptogenesis. It is not clear to what extent the partial loss of wild-type HTT function contributes to these abnormalities. Here we investigate the function of HTT in the formation of spines. Although larger spines normally correlate with more synaptic activity, cell-autonomous depletion of HTT leads to enlarged spines but reduced excitatory synaptic function. We find that HTT is required for the proper turnover of endogenous actin and to recruit AMPA receptors at active synapses; loss of HTT leads to LIM kinase (LIMK) hyperactivation, which maintains cofilin in its inactive state. HTT therefore influences actin dynamics through the LIMK-cofilin pathway. Loss of HTT uncouples spine structure from synaptic function, which may contribute to the ultimate development of HD symptoms.


Assuntos
Fatores de Despolimerização de Actina , Espinhas Dendríticas , Proteína Huntingtina , Citoesqueleto de Actina/metabolismo , Fatores de Despolimerização de Actina/metabolismo , Actinas/metabolismo , Animais , Espinhas Dendríticas/metabolismo , Proteína Huntingtina/genética , Proteína Huntingtina/metabolismo , Doença de Huntington/metabolismo , Camundongos , Sinapses/metabolismo
13.
J Virol ; 96(17): e0107422, 2022 Sep 14.
Artigo em Inglês | MEDLINE | ID: mdl-35938869

RESUMO

Rotavirus (RV) viroplasms are cytosolic inclusions where both virus genome replication and primary steps of virus progeny assembly take place. A stabilized microtubule cytoskeleton and lipid droplets are required for the viroplasm formation, which involves several virus proteins. The viral spike protein VP4 has not previously been shown to have a direct role in viroplasm formation. However, it is involved with virus-cell attachment, endocytic internalization, and virion morphogenesis. Moreover, VP4 interacts with actin cytoskeleton components, mainly in processes involving virus entrance and egress, and thereby may have an indirect role in viroplasm formation. In this study, we used reverse genetics to construct a recombinant RV, rRV/VP4-BAP, that contains a biotin acceptor peptide (BAP) in the K145-G150 loop of the VP4 lectin domain, permitting live monitoring. The recombinant virus was replication competent but showed a reduced fitness. We demonstrate that rRV/VP4-BAP infection, as opposed to rRV/wt infection, did not lead to a reorganized actin cytoskeleton as viroplasms formed were insensitive to drugs that depolymerize actin and inhibit myosin. Moreover, wild-type (wt) VP4, but not VP4-BAP, appeared to associate with actin filaments. Similarly, VP4 in coexpression with NSP5 and NSP2 induced a significant increase in the number of viroplasm-like structures. Interestingly, a small peptide mimicking loop K145-G150 rescued the phenotype of rRV/VP4-BAP by increasing its ability to form viroplasms and hence improve virus progeny formation. Collectively, these results provide a direct link between VP4 and the actin cytoskeleton to catalyze viroplasm assembly. IMPORTANCE The spike protein VP4 participates in diverse steps of the rotavirus (RV) life cycle, including virus-cell attachment, internalization, modulation of endocytosis, virion morphogenesis, and virus egress. Using reverse genetics, we constructed for the first time a recombinant RV, rRV/VP4-BAP, harboring a heterologous peptide in the lectin domain (loop K145-G150) of VP4. The rRV/VP4-BAP was replication competent but with reduced fitness due to a defect in the ability to reorganize the actin cytoskeleton, which affected the efficiency of viroplasm assembly. This defect was rescued by adding a permeable small-peptide mimicking the wild-type VP4 loop K145-G150. In addition to revealing a new role of VP4, our findings suggest that rRV harboring an engineered VP4 could be used as a new dual vaccination platform providing immunity against RV and additional heterologous antigens.


Assuntos
Citoesqueleto de Actina , Proteínas do Capsídeo , Rotavirus , Citoesqueleto de Actina/metabolismo , Proteínas do Capsídeo/metabolismo , Humanos , Lectinas , Genética Reversa , Rotavirus/genética , Rotavirus/fisiologia , Infecções por Rotavirus , Compartimentos de Replicação Viral , Replicação Viral
14.
Nature ; 609(7927): 597-604, 2022 09.
Artigo em Inglês | MEDLINE | ID: mdl-35978196

RESUMO

A key event at the onset of development is the activation of a contractile actomyosin cortex during the oocyte-to-embryo transition1-3. Here we report on the discovery that, in Caenorhabditis elegans oocytes, actomyosin cortex activation is supported by the emergence of thousands of short-lived protein condensates rich in F-actin, N-WASP and the ARP2/3 complex4-8 that form an active micro-emulsion. A phase portrait analysis of the dynamics of individual cortical condensates reveals that condensates initially grow and then transition to disassembly before dissolving completely. We find that, in contrast to condensate growth through diffusion9, the growth dynamics of cortical condensates are chemically driven. Notably, the associated chemical reactions obey mass action kinetics that govern both composition and size. We suggest that the resultant condensate dynamic instability10 suppresses coarsening of the active micro-emulsion11, ensures reaction kinetics that are independent of condensate size and prevents runaway F-actin nucleation during the formation of the first cortical actin meshwork.


Assuntos
Actinas , Actomiosina , Citoesqueleto de Actina/metabolismo , Actinas/metabolismo , Actomiosina/metabolismo , Animais , Caenorhabditis elegans/metabolismo , Emulsões
15.
Biosci Rep ; 42(9)2022 09 30.
Artigo em Inglês | MEDLINE | ID: mdl-36043949

RESUMO

Cell homeostasis is maintained in all organisms by the constant adjustment of cell constituents and organisation to account for environmental context. Fine-tuning of the optimal balance of proteins for the conditions, or protein homeostasis, is critical to maintaining cell homeostasis. Actin, a major constituent of the cytoskeleton, forms many different structures which are acutely sensitive to the cell environment. Furthermore, actin structures interact with and are critically important for the function and regulation of multiple factors involved with mRNA and protein production and degradation, and protein regulation. Altogether, actin is a key, if often overlooked, regulator of protein homeostasis across eukaryotes. In this review, we highlight these roles and how they are altered following cell stress, from mRNA transcription to protein degradation.


Assuntos
Actinas , Proteostase , Citoesqueleto de Actina/metabolismo , Actinas/genética , Actinas/metabolismo , Citoesqueleto/metabolismo , Homeostase , RNA Mensageiro/genética , RNA Mensageiro/metabolismo
16.
Biophys J ; 121(17): 3200-3212, 2022 Sep 06.
Artigo em Inglês | MEDLINE | ID: mdl-35927959

RESUMO

Actin networks rely on nucleation mechanisms to generate new filaments because spontaneous nucleation is kinetically disfavored. Branching nucleation of actin filaments by actin-related protein (Arp2/3), in particular, is critical for actin self-organization. In this study, we use the simulation platform for active matter MEDYAN to generate 2000 s long stochastic trajectories of actin networks, under varying Arp2/3 concentrations, in reaction volumes of biologically meaningful size (>20 µm3). We find that the dynamics of Arp2/3 increase the abundance of short filaments and increases network treadmilling rate. By analyzing the density fields of F-actin, we find that at low Arp2/3 concentrations, F-actin is organized into a single connected and contractile domain, while at elevated Arp2/3 levels (10 nM and above), such high-density actin domains fragment into smaller domains spanning a wide range of volumes. These fragmented domains are extremely dynamic, continuously merging and splitting, owing to the high treadmilling rate of the underlying actin network. Treating the domain dynamics as a drift-diffusion process, we find that the fragmented state is stochastically favored, and the network state slowly drifts toward the fragmented state with considerable diffusion (variability) in the number of domains. We suggest that tuning the Arp2/3 concentration enables cells to transition from a globally coherent cytoskeleton, whose response involves the entire cytoplasmic network, to a fragmented cytoskeleton, where domains can respond independently to locally varying signals.


Assuntos
Citoesqueleto de Actina , Actinas , Citoesqueleto de Actina/metabolismo , Complexo 2-3 de Proteínas Relacionadas à Actina/metabolismo , Actinas/metabolismo , Citoesqueleto/metabolismo , Difusão
17.
Life Sci Alliance ; 5(12)2022 12.
Artigo em Inglês | MEDLINE | ID: mdl-35940847

RESUMO

Actin filament polymerization can be branched or linear, which depends on the associated regulatory proteins. Competition for actin monomers occurs between proteins that induce branched or linear actin polymerization. Cell specialization requires the regulation of actin filaments to allow the formation of cell type-specific structures, like cuticular hairs in Drosophila, formed by linear actin filaments. Here, we report the functional analysis of CG34401/pelado, a gene encoding a SWIM domain-containing protein, conserved throughout the animal kingdom, called ZSWIM8 in mammals. Mutant pelado epithelial cells display actin hair elongation defects. This phenotype is reversed by increasing actin monomer levels or by either pushing linear actin polymerization or reducing branched actin polymerization. Similarly, in hemocytes, Pelado is essential to induce filopodia, a linear actin-based structure. We further show that this function of Pelado/ZSWIM8 is conserved in human cells, where Pelado inhibits branched actin polymerization in a cell migration context. In summary, our data indicate that the function of Pelado/ZSWIM8 in regulating actin cytoskeletal dynamics is conserved, favoring linear actin polymerization at the expense of branched filaments.


Assuntos
Citoesqueleto de Actina , Actinas , Ubiquitina-Proteína Ligases/metabolismo , Citoesqueleto de Actina/metabolismo , Actinas/metabolismo , Animais , Citoesqueleto/metabolismo , Humanos , Mamíferos/metabolismo , Polimerização , Pseudópodes/metabolismo
18.
Front Immunol ; 13: 883178, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-36032170

RESUMO

Cancer immunotherapy uses the immune system to achieve therapeutic effects; however, its effect is still limited. Therefore, in addition to immune checkpoint-based treatment, the development of other strategies that can inhibit cancer cells from resisting immune cytotoxicity is important. There are currently few studies on the mechanism of tumors using cytoskeletal proteins reorganization to participate in immune escape. In this study, we identified cancer cell lines that were sensitive or resistant to natural killer cells in urothelial and lung cancer using the natural killer cell sensitivity assay. We found that immunoresistant cancer cells avoid natural killer cell-mediated cytotoxicity by upregulation of vimentin and remodeling of actin cytoskeleton. Immunofluorescence staining showed that immune cells promoted the formation of actin filaments at the immune synapse, which was not found in immunosensitive cancer cells. Pretreatment of the actin polymerization inhibitors latrunculin B increased the cytotoxicity of natural killer cells, suggesting that cytoskeleton remodeling plays a role in resisting immune cell attack. In addition, silencing of vimentin with shRNA potentiated the cytotoxicity of natural killer cells. Interestingly, the upregulation and extension of vimentin was found in tumor islands of upper tract urothelial carcinoma infiltrated by natural killer cells. Conversely, tumors without natural killer cell invasion showed less vimentin signal. The expression level of vimentin was highly correlated with natural killer cell infiltration. In summary, we found that when immune cells attack cancer cells, the cancer cells resist immune cytotoxicity through upregulated vimentin and actin reorganization. In addition, this immune resistance mechanism was also found in patient tumors, indicating the possibility that they can be applied to evaluate the immune response in clinical diagnosis.


Assuntos
Carcinoma de Células de Transição , Neoplasias da Bexiga Urinária , Citoesqueleto de Actina , Actinas , Humanos , Células Matadoras Naturais , Vimentina
19.
Adv Exp Med Biol ; 1382: 29-38, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-36029402

RESUMO

Several classes of post-translational modifications (PTMs) regulate various processes that occur during neurodevelopment. The first of these processes is the regulation of the cytoskeleton and cytoskeleton-associating proteins, responsible for the stability, reorganization, and binding of microtubules and actin filaments. Dysregulations in these PTMs lead to dysregulated brain volume and composition, structural defects, behavioral defects, and dendrite growth. The second class of processes involves gene regulation, from chromatin modulation to protein turnover and degradation. Proper gene expression during neurodevelopment is critical to ensure correctly matured cells; dysregulation of PTMs in these pathways leads to various altered morphological and behavioral phenotypes. The third class of processes that are affected by PTMs is cell signaling and signal transduction, vital to cell migration and axonal guidance. Neurodevelopment is a complex sequence of spatially and temporally regulated processes, and PTMs play important roles in this regulation. Most of the known modifications have yet to be studied in depth and much remains undiscovered about their roles in neurodevelopment and otherwise.


Assuntos
Cromatina , Processamento de Proteína Pós-Traducional , Citoesqueleto de Actina , Encéfalo , Citoesqueleto
20.
J Cell Sci ; 135(15)2022 08 01.
Artigo em Inglês | MEDLINE | ID: mdl-35971979

RESUMO

Cell migration frequently involves the formation of lamellipodia induced by Rac GTPases activating WAVE regulatory complex (WRC) to drive Arp2/3 complex-dependent actin assembly. Previous genome editing studies in B16-F1 melanoma cells solidified the view of an essential, linear pathway employing the aforementioned components. Here, disruption of the WRC subunit Nap1 (encoded by Nckap1) and its paralog Hem1 (encoded by Nckap1l) followed by serum and growth factor stimulation, or active GTPase expression, revealed a pathway to formation of Arp2/3 complex-dependent lamellipodia-like structures (LLS) that requires both Rac and Cdc42 GTPases, but not WRC. These phenotypes were independent of the WRC subunit eliminated and coincided with the lack of recruitment of Ena/VASP family actin polymerases. Moreover, aside from Ena/VASP proteins, LLS contained all lamellipodial regulators tested, including cortactin (also known as CTTN), the Ena/VASP ligand lamellipodin (also known as RAPH1) and FMNL subfamily formins. Rac-dependent but WRC-independent actin remodeling could also be triggered in NIH 3T3 fibroblasts by growth factor (HGF) treatment or by gram-positive Listeria monocytogenes usurping HGF receptor signaling for host cell invasion. Taken together, our studies thus establish the existence of a signaling axis to Arp2/3 complex-dependent actin remodeling at the cell periphery that operates without WRC and Ena/VASP.


Assuntos
Actinas , Pseudópodes , Citoesqueleto de Actina/metabolismo , Complexo 2-3 de Proteínas Relacionadas à Actina/genética , Complexo 2-3 de Proteínas Relacionadas à Actina/metabolismo , Actinas/metabolismo , Movimento Celular/fisiologia , Pseudópodes/metabolismo , Família de Proteínas da Síndrome de Wiskott-Aldrich/genética , Família de Proteínas da Síndrome de Wiskott-Aldrich/metabolismo
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