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1.
Phys Rev Lett ; 127(10): 108101, 2021 Sep 03.
Artigo em Inglês | MEDLINE | ID: mdl-34533352

RESUMO

We investigate the rheological properties of interpenetrating networks reconstituted from the main cytoskeletal components: filamentous actin, microtubules, and vimentin intermediate filaments. The elastic modulus is determined largely by actin, with little contribution from either microtubules or vimentin. However, vimentin dramatically impacts the relaxation, with even small amounts significantly increasing the relaxation time of the interpenetrating network. This highly unusual decoupling between dissipation and elasticity may reflect weak attractive interactions between vimentin and actin networks.


Assuntos
Filamentos Intermediários/química , Modelos Químicos , Vimentina/química , Actinas/química , Actinas/metabolismo , Citoesqueleto/química , Citoesqueleto/metabolismo , Células Eucarióticas , Filamentos Intermediários/metabolismo , Microtúbulos/química , Microtúbulos/metabolismo , Reologia/métodos , Vimentina/metabolismo
2.
Int J Mol Sci ; 22(16)2021 Aug 04.
Artigo em Inglês | MEDLINE | ID: mdl-34445080

RESUMO

This review extensively reports data from the literature concerning the complex relationships between the stress-induced c-Jun N-terminal kinases (JNKs) and the four main cytoskeleton elements, which are actin filaments, microtubules, intermediate filaments, and septins. To a lesser extent, we also focused on the two membrane-associated cytoskeletons spectrin and ESCRT-III. We gather the mechanisms controlling cytoskeleton-associated JNK activation and the known cytoskeleton-related substrates directly phosphorylated by JNK. We also point out specific locations of the JNK upstream regulators at cytoskeletal components. We finally compile available techniques and tools that could allow a better characterization of the interplay between the different types of cytoskeleton filaments upon JNK-mediated stress and during development. This overview may bring new important information for applied medical research.


Assuntos
Proteínas do Citoesqueleto/metabolismo , Citoesqueleto/metabolismo , Proteínas Quinases JNK Ativadas por Mitógeno/metabolismo , Citoesqueleto de Actina/metabolismo , Actinas/metabolismo , Animais , Complexos Endossomais de Distribuição Requeridos para Transporte/metabolismo , Humanos , Filamentos Intermediários/metabolismo , Microtúbulos/metabolismo , Septinas/metabolismo , Espectrina/metabolismo
3.
Int J Mol Sci ; 22(16)2021 Aug 18.
Artigo em Inglês | MEDLINE | ID: mdl-34445598

RESUMO

Intra-cellular active transport by native cargos is ubiquitous. We investigate the motion of spherical nano-particles (NPs) grafted with flexible polymers that end with a nuclear localization signal peptide. This peptide allows the recruitment of several mammalian dynein motors from cytoplasmic extracts. To determine how motor-motor interactions influenced motility on the single microtubule level, we conducted bead-motility assays incorporating surface adsorbed microtubules and combined them with model simulations that were based on the properties of a single dynein. The experimental and simulation results revealed long time trajectories: when the number of NP-ligated motors Nm increased, run-times and run-lengths were enhanced and mean velocities were somewhat decreased. Moreover, the dependence of the velocity on run-time followed a universal curve, regardless of the system composition. Model simulations also demonstrated left- and right-handed helical motion and revealed self-regulation of the number of microtubule-bound, actively transporting dynein motors. This number was stochastic along trajectories and was distributed mainly between one, two, and three motors, regardless of Nm. We propose that this self-regulation allows our synthetic NPs to achieve persistent motion that is associated with major helicity. Such a helical motion might affect obstacle bypassing, which can influence active transport efficiency when facing the crowded environment of the cell.


Assuntos
Movimento Celular , Citoplasma/metabolismo , Dineínas/metabolismo , Microtúbulos/metabolismo , Nanopartículas/metabolismo , Transporte Biológico , Transporte Biológico Ativo , Células HeLa , Humanos , Nanopartículas/química
4.
Nat Commun ; 12(1): 4969, 2021 08 17.
Artigo em Inglês | MEDLINE | ID: mdl-34404787

RESUMO

Multimeric cytoskeletal protein complexes orchestrate normal cellular function. However, protein-complex distributions in stressed, heterogeneous cell populations remain unknown. Cell staining and proximity-based methods have limited selectivity and/or sensitivity for endogenous multimeric protein-complex quantification from single cells. We introduce micro-arrayed, differential detergent fractionation to simultaneously detect protein complexes in hundreds of individual cells. Fractionation occurs by 60 s size-exclusion electrophoresis with protein complex-stabilizing buffer that minimizes depolymerization. Proteins are measured with a ~5-hour immunoassay. Co-detection of cytoskeletal protein complexes in U2OS cells treated with filamentous actin (F-actin) destabilizing Latrunculin A detects a unique subpopulation (~2%) exhibiting downregulated F-actin, but upregulated microtubules. Thus, some cells may upregulate other cytoskeletal complexes to counteract the stress of Latrunculin A treatment. We also sought to understand the effect of non-chemical stress on cellular heterogeneity of F-actin. We find heat shock may dysregulate filamentous and globular actin correlation. In this work, our assay overcomes selectivity limitations to biochemically quantify single-cell protein complexes perturbed with diverse stimuli.


Assuntos
Proteínas do Citoesqueleto/genética , Proteínas do Citoesqueleto/metabolismo , Citoesqueleto/metabolismo , Heterogeneidade Genética , Actinas/genética , Actinas/metabolismo , Animais , Compostos Bicíclicos Heterocíclicos com Pontes/farmacologia , Diferenciação Celular , Linhagem Celular , Resposta ao Choque Térmico , Humanos , Microtúbulos/metabolismo , Modelos Biológicos , Análise de Célula Única/métodos , Tiazolidinas/farmacologia
5.
Int J Mol Sci ; 22(15)2021 Jul 28.
Artigo em Inglês | MEDLINE | ID: mdl-34360874

RESUMO

Osteoarthritis (OA) is still a recalcitrant musculoskeletal disease on account of its complex biochemistry and mechanical stimulations. Apart from stimulation by external mechanical forces, the regulation of intracellular mechanics in chondrocytes has also been linked to OA development. Recently, visfatin has received significant attention because of the clinical finding of the positive correlation between its serum/synovial level and OA progression. However, the precise mechanism involved is still unclear. This study determined the effect of visfatin on intracellular mechanics and catabolism in human primary chondrocytes isolated from patients. The intracellular stiffness of chondrocytes was analyzed by the particle-tracking microrheology method. It was shown that visfatin damages the microtubule and microfilament networks to influence intracellular mechanics to decrease the intracellular elasticity and viscosity via glycogen synthase kinase 3ß (GSK3ß) inactivation induced by p38 signaling. Further, microtubule network destruction in human primary chondrocytes is predominantly responsible for the catabolic effect of visfatin on the cyclooxygenase 2 upregulation. The present study shows a more comprehensive interpretation of OA development induced by visfatin through biochemical and biophysical perspectives. Finally, the role of GSK3ß inactivation, and subsequent regulation of intracellular mechanics, might be considered as theranostic targets for future drug development for OA.


Assuntos
Condrócitos , Citocinas/fisiologia , Glicogênio Sintase Quinase 3 beta/metabolismo , Nicotinamida Fosforribosiltransferase/fisiologia , Osteoartrite , Citoesqueleto de Actina/metabolismo , Células Cultivadas , Condrócitos/metabolismo , Condrócitos/patologia , Humanos , Microtúbulos/metabolismo , Osteoartrite/metabolismo , Osteoartrite/patologia , Cultura Primária de Células
6.
Biophys J ; 120(15): 3192-3210, 2021 08 03.
Artigo em Inglês | MEDLINE | ID: mdl-34197801

RESUMO

Proper formation and maintenance of the mitotic spindle is required for faithful cell division. Although much work has been done to understand the roles of the key molecular components of the mitotic spindle, identifying the consequences of force perturbations in the spindle remains a challenge. We develop a computational framework accounting for the minimal force requirements of mitotic progression. To reflect early spindle formation, we model microtubule dynamics and interactions with major force-generating motors, excluding chromosome interactions that dominate later in mitosis. We directly integrate our experimental data to define and validate the model. We then use simulations to analyze individual force components over time and their relationship to spindle dynamics, making it distinct from previously published models. We show through both model predictions and biological manipulation that rather than achieving and maintaining a constant bipolar spindle length, fluctuations in pole-to-pole distance occur that coincide with microtubule binding and force generation by cortical dynein. Our model further predicts that high dynein activity is required for spindle bipolarity when kinesin-14 (HSET) activity is also high. To the best of our knowledge, our results provide novel insight into the role of cortical dynein in the regulation of spindle bipolarity.


Assuntos
Dineínas , Fuso Acromático , Segregação de Cromossomos , Dineínas/metabolismo , Cinesina/metabolismo , Proteínas Associadas aos Microtúbulos/metabolismo , Microtúbulos/metabolismo , Mitose , Fuso Acromático/metabolismo
7.
Adv Exp Med Biol ; 1208: 67-77, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-34260022

RESUMO

Autophagy is a major intracellular degradation/recycling system that ubiquitously exists in eukaryotic cells. Autophagy contributes to the turnover of cellular components through engulfing portions of the cytoplasm or organelles and delivering them to the lysosomes/vacuole to be degraded. The trafficking of autophagosomes and their fusion with lysosomes are important steps that complete their maturation and degradation. In cells such as neuron, autophagosomes traffic long distances along the axon, while in other specialized cells such as cardiomyocytes, it is unclear how and even whether autophagosomes are transported. Therefore, it is important to learn more about the processes and mechanisms of autophagosome trafficking to lysosomes/vacuole during autophagy. The mechanisms of autophagosome trafficking are similar to those of other organelles trafficking within cells. The machinery mainly includes cytoskeletal systems such as actin and microtubules, motor proteins such as myosins and the dynein-dynactin complex, and other proteins like LC3 on the membrane of autophagosomes. Factors regulating autophagosome trafficking have not been widely studied. To date the main reagents identified for disrupting autophagosome trafficking include: 1. Microtubule polymerization reagents, which disrupt microtubules by interfering with microtubule dynamics, thus directly influence microtubule-dependent autophagosome trafficking 2. F-actin-depolymerizing drugs, which inhibit autophagosome formation, and also subsequently inhibit autophagosome trafficking 3. Motor protein regulators, which directly affect autophagosome trafficking.


Assuntos
Autofagossomos , Lisossomos , Autofagossomos/metabolismo , Autofagia , Dineínas , Lisossomos/metabolismo , Microtúbulos/metabolismo
8.
Int J Mol Sci ; 22(14)2021 Jul 19.
Artigo em Inglês | MEDLINE | ID: mdl-34299323

RESUMO

Dynein is a ~1.2 MDa cytoskeletal motor protein that carries organelles via retrograde transport in eukaryotic cells. The motor protein belongs to the ATPase family of proteins associated with diverse cellular activities and plays a critical role in transporting cargoes to the minus end of the microtubules. The motor domain of dynein possesses a hexameric head, where ATP hydrolysis occurs. The presented work analyzes the structure-activity relationship (SAR) of dynapyrazole A and B, as well as ciliobrevin A and D, in their various protonated states and their 46 analogues for their binding in the AAA1 subunit, the leading ATP hydrolytic site of the motor domain. This study exploits in silico methods to look at the analogues' effects on the functionally essential subsites of the motor domain of dynein 1, since no similar experimental structural data are available. Ciliobrevin and its analogues bind to the ATP motifs of the AAA1, namely, the walker-A (W-A) or P-loop, the walker-B (W-B), and the sensor I and II. Ciliobrevin A shows a better binding affinity than its D analogue. Although the double bond in ciliobrevin A and D was expected to decrease the ligand potency, they show a better affinity to the AAA1 binding site than dynapyrazole A and B, lacking the bond. In addition, protonation of the nitrogen atom in ciliobrevin A and D, as well as dynapyrazole A and B, at the N9 site of ciliobrevin and the N7 of the latter increased their binding affinity. Exploring ciliobrevin A geometrical configuration suggests the E isomer has a superior binding profile over the Z due to binding at the critical ATP motifs. Utilizing the refined structure of the motor domain obtained through protein conformational search in this study exhibits that Arg1852 of the yeast cytoplasmic dynein could involve in the "glutamate switch" mechanism in cytoplasmic dynein 1 in lieu of the conserved Asn in AAA+ protein family.


Assuntos
Trifosfato de Adenosina/metabolismo , Dineínas/química , Quinazolinonas/metabolismo , ATPases Associadas a Diversas Atividades Celulares/metabolismo , Sítios de Ligação , Transporte Biológico , Simulação por Computador , Citoplasma/metabolismo , Dineínas do Citoplasma/química , Dineínas do Citoplasma/metabolismo , Dineínas/antagonistas & inibidores , Dineínas/metabolismo , Hidrólise , Microtúbulos/metabolismo , Ligação Proteica , Conformação Proteica , Quinazolinonas/química , Saccharomyces cerevisiae/metabolismo , Proteínas de Saccharomyces cerevisiae/metabolismo , Relação Estrutura-Atividade
9.
J Chem Theory Comput ; 17(8): 5358-5368, 2021 Aug 10.
Artigo em Inglês | MEDLINE | ID: mdl-34251798

RESUMO

Conventional kinesin, a motor protein that transports cargo within cells, walks by taking multiple steps toward the plus end of the microtubule (MT). While significant progress has been made in understanding the details of the walking mechanism of kinesin, there are many unresolved issues. From a computational perspective, a central challenge is the large size of the system, which limits the scope of time scales accessible in standard computer simulations. Here, we create a general multiscale coarse-grained model for motors that enables us to simulate the stepping process of motors on polar tracks (actin and MT) with a focus on kinesin. Our approach greatly shortens the computation times without a significant loss in detail, thus allowing us to better describe the molecular basis of the stepping kinetics. The small number of parameters, which are determined by fitting to experimental data, allows us to develop an accurate method that may be adopted to simulate stepping in other molecular motors. The model enables us to simulate a large number of steps, which was not possible previously. We show in agreement with experiments that due to the docking of the neck linker (NL) of kinesin, sometimes deemed as the power stroke, the space explored diffusively by the tethered head is severely restricted, allowing the step to be completed in tens of microseconds. We predict that increasing the interaction strength between the NL and the motor head, achievable by mutations in the NL, decreases the stepping time but reaches a saturation value. Furthermore, the full three-dimensional dynamics of the cargo are fully resolved in our model, contributing to the predictive power and allowing us to study the important aspects of cargo-motor interactions.


Assuntos
Cinesina/química , Simulação de Acoplamento Molecular , Cinesina/metabolismo , Microtúbulos/química , Microtúbulos/metabolismo
11.
Nat Commun ; 12(1): 4493, 2021 07 23.
Artigo em Inglês | MEDLINE | ID: mdl-34301956

RESUMO

Neuronal function relies on careful coordination of organelle organization and transport. Kinesin-1 mediates transport of the endoplasmic reticulum (ER) and lysosomes into the axon and it is increasingly recognized that contacts between the ER and lysosomes influence organelle organization. However, it is unclear how organelle organization, inter-organelle communication and transport are linked and how this contributes to local organelle availability in neurons. Here, we show that somatic ER tubules are required for proper lysosome transport into the axon. Somatic ER tubule disruption causes accumulation of enlarged and less motile lysosomes at the soma. ER tubules regulate lysosome size and axonal translocation by promoting lysosome homo-fission. ER tubule - lysosome contacts often occur at a somatic pre-axonal region, where the kinesin-1-binding ER-protein P180 binds microtubules to promote kinesin-1-powered lysosome fission and subsequent axonal translocation. We propose that ER tubule - lysosome contacts at a pre-axonal region finely orchestrate axonal lysosome availability for proper neuronal function.


Assuntos
Axônios/metabolismo , Retículo Endoplasmático/metabolismo , Lisossomos/metabolismo , Neurônios/metabolismo , Animais , Transporte Axonal/fisiologia , Células Cultivadas , Feminino , Cinesina/metabolismo , Microtúbulos/metabolismo , Neurônios/citologia , Ligação Proteica , Ratos Wistar
12.
J Cell Sci ; 134(14)2021 07 15.
Artigo em Inglês | MEDLINE | ID: mdl-34297125

RESUMO

As one of four filament types, microtubules are a core component of the cytoskeleton and are essential for cell function. Yet how microtubules are nucleated from their building blocks, the αß-tubulin heterodimer, has remained a fundamental open question since the discovery of tubulin 50 years ago. Recent structural studies have shed light on how γ-tubulin and the γ-tubulin complex proteins (GCPs) GCP2 to GCP6 form the γ-tubulin ring complex (γ-TuRC). In parallel, functional and single-molecule studies have informed on how the γ-TuRC nucleates microtubules in real time, how this process is regulated in the cell and how it compares to other modes of nucleation. Another recent surprise has been the identification of a second essential nucleation factor, which turns out to be the well-characterized microtubule polymerase XMAP215 (also known as CKAP5, a homolog of chTOG, Stu2 and Alp14). This discovery helps to explain why the observed nucleation activity of the γ-TuRC in vitro is relatively low. Taken together, research in recent years has afforded important insight into how microtubules are made in the cell and provides a basis for an exciting era in the cytoskeleton field.


Assuntos
Proteínas Associadas aos Microtúbulos , Microtúbulos , Proteínas Associadas aos Microtúbulos/metabolismo , Centro Organizador dos Microtúbulos/metabolismo , Microtúbulos/metabolismo , Estrutura Secundária de Proteína , Tubulina (Proteína)/genética , Tubulina (Proteína)/metabolismo
13.
Nat Commun ; 12(1): 4578, 2021 07 28.
Artigo em Inglês | MEDLINE | ID: mdl-34321481

RESUMO

Mitochondria are transported along microtubules by opposing kinesin and dynein motors. Kinesin-1 and dynein-dynactin are linked to mitochondria by TRAK proteins, but it is unclear how TRAKs coordinate these motors. We used single-molecule imaging of cell lysates to show that TRAK2 robustly activates kinesin-1 for transport toward the microtubule plus-end. TRAK2 is also a novel dynein activating adaptor that utilizes a conserved coiled-coil motif to interact with dynein to promote motility toward the microtubule minus-end. However, dynein-mediated TRAK2 transport is minimal unless the dynein-binding protein LIS1 is present at a sufficient level. Using co-immunoprecipitation and co-localization experiments, we demonstrate that TRAK2 forms a complex containing both kinesin-1 and dynein-dynactin. These motors are functionally linked by TRAK2 as knockdown of either kinesin-1 or dynein-dynactin reduces the initiation of TRAK2 transport toward either microtubule end. We propose that TRAK2 coordinates kinesin-1 and dynein-dynactin as an interdependent motor complex, providing integrated control of opposing motors for the proper transport of mitochondria.


Assuntos
Dineínas/metabolismo , Peptídeos e Proteínas de Sinalização Intracelular/metabolismo , Cinesina/metabolismo , Mitocôndrias/metabolismo , Proteínas do Tecido Nervoso/metabolismo , 1-Alquil-2-acetilglicerofosfocolina Esterase , Proteínas de Transporte/metabolismo , Complexo Dinactina/metabolismo , Humanos , Peptídeos e Proteínas de Sinalização Intracelular/genética , Proteínas Associadas aos Microtúbulos , Microtúbulos/metabolismo , Proteínas do Tecido Nervoso/genética , Transporte Proteico/fisiologia , Transcriptoma
14.
Int J Mol Sci ; 22(12)2021 Jun 15.
Artigo em Inglês | MEDLINE | ID: mdl-34203964

RESUMO

Bipolar kinesin-5 motor proteins perform multiple intracellular functions, mainly during mitotic cell division. Their specialized structural characteristics enable these motors to perform their essential functions by crosslinking and sliding apart antiparallel microtubules (MTs). In this review, we discuss the specialized structural features of kinesin-5 motors, and the mechanisms by which these features relate to kinesin-5 functions and motile properties. In addition, we discuss the multiple roles of the kinesin-5 motors in dividing as well as in non-dividing cells, and examine their roles in pathogenetic conditions. We describe the recently discovered bidirectional motility in fungi kinesin-5 motors, and discuss its possible physiological relevance. Finally, we also focus on the multiple mechanisms of regulation of these unique motor proteins.


Assuntos
Espaço Intracelular/metabolismo , Cinesina/metabolismo , Animais , Humanos , Cinesina/química , Microtúbulos/metabolismo , Modelos Biológicos , Processamento de Proteína Pós-Traducional , Fuso Acromático/metabolismo
15.
BMC Genomics ; 22(1): 570, 2021 Jul 24.
Artigo em Inglês | MEDLINE | ID: mdl-34303338

RESUMO

BACKGROUND: Formin, a highly conserved multi-domain protein, interacts with microfilaments and microtubules. Although specifically expressed formin genes in anthers are potentially significant in research on male sterility and hybrid wheat breeding, similar reports in wheat, especially in thermo-sensitive genic male sterile (TGMS) wheat, remain elusive. RESULTS: Herein, we systematically characterized the formin genes in TGMS wheat line BS366 named TaFormins (TaFHs) and predicted their functions in inducing stress response. In total, 25 TaFH genes were uncovered, majorly localized in 2A, 2B, and 2D chromosomes. According to the neighbor-joining (NJ) method, all TaFH proteins from wheat and other plants clustered in 6 sub-groups (A-F). The modeled 3D structures of TaFH1-A/B, TaFH2-A/B, TaFH3-A/B and TaFH3-B/D were validated. And different numbers of stress and hormone-responsive regulatory elements in their 1500 base pair promoter regions were contained in the TaFH genes copies. TaFHs had specific temporal and spatial expression characteristics, whereby TaFH1, TaFH4, and TaFH5 were expressed highly in the stamen of BS366. Besides, the accumulation of TaFHs was remarkably lower in a low-temperature sterile condition (Nanyang) than fertile condition (Beijing), particularly at the early stamen development stage. The pollen cytoskeleton of BS366 was abnormal in the three stages under sterile and fertile environments. Furthermore, under different stress levels, TaFHs expression could be induced by drought, salt, abscisic acid (ABA), salicylic acid (SA), methyl jasmonate (MeJA), indole-3-acetic acid (IAA), polyethylene glycol (PEG), and low temperature. Some miRNAs, including miR167, miR1120, and miR172, interacts with TaFH genes; thus, we constructed an interaction network between microRNAs, TaFHs, phytohormone responses, and distribution of cytoskeleton to reveal the regulatory association between upstream genes of TaFH family members and sterile. CONCLUSIONS: Collectively, this comprehensive analysis provides novel insights into TaFHs and miRNA resources for wheat breeding. These findings are, therefore, valuable in understanding the mechanism of TGMS fertility conversion in wheat.


Assuntos
Melhoramento Vegetal , Triticum , Citoesqueleto/metabolismo , Fertilidade/genética , Forminas , Regulação da Expressão Gênica de Plantas , Microtúbulos/metabolismo , Proteínas de Plantas/genética , Proteínas de Plantas/metabolismo , Pólen/genética , Pólen/metabolismo , Triticum/genética , Triticum/metabolismo
16.
Int J Mol Sci ; 22(14)2021 Jul 07.
Artigo em Inglês | MEDLINE | ID: mdl-34298924

RESUMO

Coumarin is a phytotoxic natural compound able to affect plant growth and development. Previous studies have demonstrated that this molecule at low concentrations (100 µM) can reduce primary root growth and stimulate lateral root formation, suggesting an auxin-like activity. In the present study, we evaluated coumarin's effects (used at lateral root-stimulating concentrations) on the root apical meristem and polar auxin transport to identify its potential mode of action through a confocal microscopy approach. To achieve this goal, we used several Arabidopsis thaliana GFP transgenic lines (for polar auxin transport evaluation), immunolabeling techniques (for imaging cortical microtubules), and GC-MS analysis (for auxin quantification). The results highlighted that coumarin induced cyclin B accumulation, which altered the microtubule cortical array organization and, consequently, the root apical meristem architecture. Such alterations reduced the basipetal transport of auxin to the apical root apical meristem, inducing its accumulation in the maturation zone and stimulating lateral root formation.


Assuntos
Arabidopsis/efeitos dos fármacos , Transporte Biológico/efeitos dos fármacos , Cumarínicos/farmacologia , Ácidos Indolacéticos/metabolismo , Meristema/efeitos dos fármacos , Microtúbulos/efeitos dos fármacos , Raízes de Plantas/efeitos dos fármacos , Arabidopsis/metabolismo , Proteínas de Arabidopsis/metabolismo , Regulação da Expressão Gênica de Plantas/efeitos dos fármacos , Meristema/metabolismo , Microtúbulos/metabolismo , Raízes de Plantas/metabolismo
17.
Cell Mol Life Sci ; 78(16): 6051-6068, 2021 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-34274977

RESUMO

Two modes of motility have been reported for bi-directional kinesin-5 motors: (a) context-dependent directionality reversal, a mode in which motors undergo persistent minus-end directed motility at the single-molecule level and switch to plus-end directed motility in different assays or under different conditions, such as during MT gliding or antiparallel sliding or as a function of motor clustering; and (b) bi-directional motility, defined as movement in two directions in the same assay, without persistent unidirectional motility. Here, we examine how modulation of motor-microtubule (MT) interactions affects these two modes of motility for the bi-directional kinesin-5, Cin8. We report that the large insert in loop 8 (L8) within the motor domain of Cin8 increases the MT affinity of Cin8 in vivo and in vitro and is required for Cin8 intracellular functions. We consistently found that recombinant purified L8 directly binds MTs and L8 induces single Cin8 motors to behave according to context-dependent directionality reversal and bi-directional motility modes at intermediate ionic strength and according to a bi-directional motility mode in an MT surface-gliding assay under low motor density conditions. We propose that the largely unstructured L8 facilitates flexible anchoring of Cin8 to the MTs. This flexible anchoring enables the direct observation of bi-directional motility in motility assays. Remarkably, although L8-deleted Cin8 variants exhibit a strong minus-end directed bias at the single-molecule level, they also exhibit plus-end directed motility in an MT-gliding assay. Thus, L8-induced flexible MT anchoring is required for bi-directional motility of single Cin8 molecules but is not necessary for context-dependent directionality reversal of Cin8 in an MT-gliding assay.


Assuntos
Cinesina/metabolismo , Microtúbulos/metabolismo , Proteínas de Saccharomyces cerevisiae/metabolismo , Sequência de Aminoácidos , Movimento/fisiologia , Saccharomyces cerevisiae/metabolismo
18.
Nat Commun ; 12(1): 4096, 2021 07 02.
Artigo em Inglês | MEDLINE | ID: mdl-34215746

RESUMO

Non-centrosomal microtubule arrays serve crucial functions in cells, yet the mechanisms of their generation are poorly understood. During budding of the epithelial tubes of the salivary glands in the Drosophila embryo, we previously demonstrated that the activity of pulsatile apical-medial actomyosin depends on a longitudinal non-centrosomal microtubule array. Here we uncover that the exit from the last embryonic division cycle of the epidermal cells of the salivary gland placode leads to one centrosome in the cells losing all microtubule-nucleation capacity. This restriction of nucleation activity to the second, Centrobin-enriched, centrosome is key for proper morphogenesis. Furthermore, the microtubule-severing protein Katanin and the minus-end-binding protein Patronin accumulate in an apical-medial position only in placodal cells. Loss of either in the placode prevents formation of the longitudinal microtubule array and leads to loss of apical-medial actomyosin and impaired apical constriction. We thus propose a mechanism whereby Katanin-severing at the single active centrosome releases microtubule minus-ends that are then anchored by apical-medial Patronin to promote formation of the longitudinal microtubule array crucial for apical constriction and tube formation.


Assuntos
Divisão Celular/fisiologia , Centrossomo/metabolismo , Microtúbulos/metabolismo , Actinas , Actomiosina/metabolismo , Animais , Centrossomo/ultraestrutura , Proteínas do Citoesqueleto/metabolismo , Drosophila , Katanina , Masculino , Proteínas dos Microfilamentos/metabolismo , Proteínas Associadas aos Microtúbulos/metabolismo , Microtúbulos/ultraestrutura , Morfogênese , Glândulas Salivares , Tubulina (Proteína)/metabolismo
19.
Nat Commun ; 12(1): 4113, 2021 07 05.
Artigo em Inglês | MEDLINE | ID: mdl-34226540

RESUMO

Tri-methylation on lysine 40 of α-tubulin (α-TubK40me3) is a recently identified post-translational modification involved in mitosis and cytokinesis. However, knowledge about α-TubK40me3 in microtubule function and post-mitotic cells remains largely incomplete. Here, we report that α-TubK40me3 is required for neuronal polarization and migration by promoting microtubule formation. α-TubK40me3 is enriched in mouse cerebral cortex during embryonic day (E)14 to E16. Knockdown of α-tubulin methyltransferase SETD2 at E14 leads to the defects in neuronal migration, which could be restored by overexpressing either a cytoplasm-localized SETD2 truncation or α-TubK40me3-mimicking mutant. Furthermore, α-TubK40me3 is preferably distributed on polymerized microtubules and potently promotes tubulin nucleation. Downregulation of α-TubK40me3 results in reduced microtubule abundance in neurites and disrupts neuronal polarization, which could be rescued by Taxol. Additionally, α-TubK40me3 is increased after losing α-tubulin K40 acetylation (α-TubK40ac) and largely rescues α-TubK40ac function. This study reveals a critical role of α-TubK40me3 in microtubule formation and neuronal development.


Assuntos
Movimento Celular , Microtúbulos/metabolismo , Neurônios/metabolismo , Tubulina (Proteína)/metabolismo , Acetilação , Animais , Córtex Cerebral , Citocinese , Técnicas de Silenciamento de Genes , Histona-Lisina N-Metiltransferase/genética , Histona-Lisina N-Metiltransferase/metabolismo , Lisina/metabolismo , Metilação , Camundongos , Mitose , Neurogênese , Paclitaxel , Processamento de Proteína Pós-Traducional
20.
Nat Commun ; 12(1): 4639, 2021 07 30.
Artigo em Inglês | MEDLINE | ID: mdl-34330922

RESUMO

The silica cell wall of diatoms, a widespread group of unicellular microalgae, is an exquisite example for the ability of organisms to finely sculpt minerals under strict biological control. The prevailing paradigm for diatom silicification is that this is invariably an intracellular process, occurring inside specialized silica deposition vesicles that are responsible for silica precipitation and morphogenesis. Here, we study the formation of long silicified extensions that characterize many diatom species. We use cryo-electron tomography to image silica formation in situ, in 3D, and at a nanometer-scale resolution. Remarkably, our data suggest that, contradictory to the ruling paradigm, these intricate structures form outside the cytoplasm. In addition, the formation of these silica extensions is halted at low silicon concentrations that still support the formation of other cell wall elements, further alluding to a different silicification mechanism. The identification of this unconventional strategy expands the suite of mechanisms that diatoms use for silicification.


Assuntos
Parede Celular/metabolismo , Diatomáceas/metabolismo , Espaço Extracelular/metabolismo , Dióxido de Silício/metabolismo , Ciclo Celular , Membrana Celular/metabolismo , Membrana Celular/ultraestrutura , Parede Celular/ultraestrutura , Microscopia Crioeletrônica/métodos , Diatomáceas/ultraestrutura , Tomografia com Microscopia Eletrônica/métodos , Microscopia Eletrônica de Varredura/métodos , Microscopia Eletrônica de Transmissão/métodos , Microtúbulos/metabolismo , Microtúbulos/ultraestrutura
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