RESUMO
Cytoplasmic dynein-1 binds dynactin and cargo adaptor proteins to form a transport machine capable of long-distance processive movement along microtubules. However, it is unclear why dynein-1 moves poorly on its own or how it is activated by dynactin. Here, we present a cryoelectron microscopy structure of the complete 1.4-megadalton human dynein-1 complex in an inhibited state known as the phi-particle. We reveal the 3D structure of the cargo binding dynein tail and show how self-dimerization of the motor domains locks them in a conformation with low microtubule affinity. Disrupting motor dimerization with structure-based mutagenesis drives dynein-1 into an open form with higher affinity for both microtubules and dynactin. We find the open form is also inhibited for movement and that dynactin relieves this by reorienting the motor domains to interact correctly with microtubules. Our model explains how dynactin binding to the dynein-1 tail directly stimulates its motor activity.
Assuntos
Dineínas do Citoplasma/química , Complexos Multiproteicos/química , Animais , Microscopia Crioeletrônica , Dineínas do Citoplasma/metabolismo , Dineínas do Citoplasma/ultraestrutura , Dimerização , Complexo Dinactina/química , Complexo Dinactina/metabolismo , Humanos , Camundongos , Microtúbulos/química , Microtúbulos/metabolismo , Modelos Moleculares , Proteínas Motores Moleculares/química , Proteínas Motores Moleculares/metabolismo , Complexos Multiproteicos/metabolismo , Complexos Multiproteicos/ultraestrutura , Células Sf9 , Spodoptera , SuínosRESUMO
Cytoplasmic dynein 1 is an important microtubule-based motor in many eukaryotic cells. Dynein has critical roles both in interphase and during cell division. Here, we focus on interphase cargoes of dynein, which include membrane-bound organelles, RNAs, protein complexes and viruses. A central challenge in the field is to understand how a single motor can transport such a diverse array of cargoes and how this process is regulated. The molecular basis by which each cargo is linked to dynein and its cofactor dynactin has started to emerge. Of particular importance for this process is a set of coiled-coil proteins - activating adaptors - that both recruit dynein-dynactin to their cargoes and activate dynein motility.
Assuntos
Transporte Biológico/fisiologia , Dineínas do Citoplasma/metabolismo , Animais , Movimento Celular/fisiologia , Complexo Dinactina/metabolismo , Humanos , Microtúbulos/metabolismo , Organelas/metabolismoRESUMO
Mitotic spindle position defines the cell-cleavage site during cytokinesis. However, the mechanisms that control spindle positioning to generate equal-sized daughter cells remain poorly understood. Here, we demonstrate that two mechanisms act coordinately to center the spindle during anaphase in symmetrically dividing human cells. First, the spindle is positioned directly by the microtubule-based motor dynein, which we demonstrate is targeted to the cell cortex by two distinct pathways: a Gαi/LGN/NuMA-dependent pathway and a 4.1G/R and NuMA-dependent, anaphase-specific pathway. Second, we find that asymmetric plasma membrane elongation occurs in response to spindle mispositioning to alter the cellular boundaries relative to the spindle. Asymmetric membrane elongation is promoted by chromosome-derived Ran-GTP signals that locally reduce Anillin at the growing cell cortex. In asymmetrically elongating cells, dynein-dependent spindle anchoring at the stationary cell cortex ensures proper spindle positioning. Our results reveal the anaphase-specific spindle centering systems that achieve equal-sized cell division.
Assuntos
Anáfase , Membrana Celular/metabolismo , Dineínas/metabolismo , Fuso Acromático/metabolismo , Sequência de Aminoácidos , Animais , Antígenos Nucleares/metabolismo , Proteínas de Ciclo Celular , Proteínas do Citoesqueleto/química , Proteínas do Citoesqueleto/metabolismo , Complexo Dinactina , Células HeLa , Humanos , Peptídeos e Proteínas de Sinalização Intracelular/metabolismo , Proteínas de Membrana/química , Proteínas de Membrana/metabolismo , Proteínas Associadas aos Microtúbulos/metabolismo , Dados de Sequência Molecular , Proteínas Associadas à Matriz Nuclear/metabolismo , Alinhamento de SequênciaRESUMO
Cytoplasmic dynein is a microtubule motor that is activated by its cofactor dynactin and a coiled-coil cargo adaptor1-3. Up to two dynein dimers can be recruited per dynactin, and interactions between them affect their combined motile behaviour4-6. Different coiled-coil adaptors are linked to different cargos7,8, and some share motifs known to contact sites on dynein and dynactin4,9-13. There is limited structural information on how the resulting complex interacts with microtubules and how adaptors are recruited. Here we develop a cryo-electron microscopy processing pipeline to solve the high-resolution structure of dynein-dynactin and the adaptor BICDR1 bound to microtubules. This reveals the asymmetric interactions between neighbouring dynein motor domains and how they relate to motile behaviour. We found that two adaptors occupy the complex. Both adaptors make similar interactions with the dyneins but diverge in their contacts with each other and dynactin. Our structure has implications for the stability and stoichiometry of motor recruitment by cargos.
Assuntos
Microscopia Crioeletrônica , Dineínas do Citoplasma , Complexo Dinactina , Microtúbulos , Proteínas Adaptadoras de Transporte Vesicular/química , Proteínas Adaptadoras de Transporte Vesicular/metabolismo , Proteínas Adaptadoras de Transporte Vesicular/ultraestrutura , Dineínas do Citoplasma/química , Dineínas do Citoplasma/metabolismo , Dineínas do Citoplasma/ultraestrutura , Complexo Dinactina/química , Complexo Dinactina/metabolismo , Complexo Dinactina/ultraestrutura , Microtúbulos/química , Microtúbulos/metabolismo , Microtúbulos/ultraestrutura , Ligação ProteicaRESUMO
In a recent study, Chaaban and Carter use cryo-electron microscopy (cryo-EM) and an innovative data-processing pipeline to determine the first high-resolution structure of the dynein-dynactin-BICDR1 complex assembled on microtubules. The structure of the complex reveals novel stoichiometry and provides new mechanistic insight into dynein function and mechanism.
Assuntos
Dineínas , Proteínas Associadas aos Microtúbulos , Dineínas/metabolismo , Proteínas Associadas aos Microtúbulos/análise , Proteínas Associadas aos Microtúbulos/química , Proteínas Associadas aos Microtúbulos/metabolismo , Microscopia Crioeletrônica , Microtúbulos/química , Microtúbulos/metabolismo , Complexo Dinactina/análise , Complexo Dinactina/química , Complexo Dinactina/metabolismoRESUMO
The microtubule motor dynein mediates polarised trafficking of a wide variety of organelles, vesicles and macromolecules. These functions are dependent on the dynactin complex, which helps recruit cargoes to dynein's tail and activates motor movement. How the dynein-dynactin complex orchestrates trafficking of diverse cargoes is unclear. Here, we identify HEATR5B, an interactor of the adaptor protein-1 (AP1) clathrin adaptor complex, as a novel player in dynein-dynactin function. HEATR5B was recovered in a biochemical screen for proteins whose association with the dynein tail is augmented by dynactin. We show that HEATR5B binds directly to the dynein tail and dynactin and stimulates motility of AP1-associated endosomal membranes in human cells. We also demonstrate that the Drosophila HEATR5B homologue is an essential gene that selectively promotes dynein-based transport of AP1-bound membranes to the Golgi apparatus. As HEATR5B lacks the coiled-coil architecture typical of dynein adaptors, our data point to a non-canonical process orchestrating motor function on a specific cargo. We additionally show that HEATR5B promotes association of AP1 with endosomal membranes independently of dynein. Thus, HEATR5B co-ordinates multiple events in AP1-based trafficking.
Assuntos
Dineínas , Proteínas Associadas aos Microtúbulos , Humanos , Dineínas/metabolismo , Complexo Dinactina/metabolismo , Proteínas Associadas aos Microtúbulos/genética , Proteínas Associadas aos Microtúbulos/metabolismo , Transporte Biológico/fisiologia , Microtúbulos/metabolismo , Endossomos/metabolismoRESUMO
Chromosome biorientation on the mitotic spindle is prerequisite to errorless genome inheritance. CENP-E (kinesin-7) and dynein-dynactin (DD), microtubule motors with opposite polarity, promote biorientation from the kinetochore corona, a polymeric structure whose assembly requires MPS1 kinase. The corona's building block consists of ROD, Zwilch, ZW10, and the DD adaptor Spindly (RZZS). How CENP-E and DD are scaffolded and mutually coordinated in the corona remains unclear. Here, we show that when corona assembly is prevented through MPS1 inhibition, CENP-E is absolutely required to retain RZZS at kinetochores. An RZZS phosphomimetic mutant bypasses this requirement, demonstrating the existence of a second receptor for polymeric RZZS. With active MPS1, CENP-E is dispensable for corona expansion, but strictly required for physiological kinetochore accumulation of DD. Thus, we identify the corona as an integrated scaffold where CENP-E kinesin controls DD kinetochore loading for coordinated bidirectional transport of chromosome cargo.
Assuntos
Dineínas , Cinetocoros , Dineínas/genética , Dineínas/metabolismo , Cinetocoros/metabolismo , Cinesinas/genética , Proteínas de Ciclo Celular/genética , Proteínas de Ciclo Celular/metabolismo , Fuso Acromático/metabolismo , Microtúbulos/metabolismo , Complexo Dinactina/genética , Mitose , Segregação de CromossomosRESUMO
Cell polarization requires asymmetric localization of numerous mRNAs, proteins and organelles. The movement of cargo towards the minus end of microtubules mostly depends on cytoplasmic dynein motors. In the dynein-dynactin-Bicaudal-D transport machinery, Bicaudal-D (BicD) links the cargo to the motor. Here, we focus on the role of Drosophila BicD-related (BicDR, CG32137) in the development of the long bristles. Together with BicD, it contributes to the organization and stability of the actin cytoskeleton in the not-yet-chitinized bristle shaft. BicD and BicDR also support the stable expression and distribution of Rab6 and Spn-F in the bristle shaft, including the distal tip localization of Spn-F, pointing to the role of microtubule-dependent vesicle trafficking for bristle construction. BicDR supports the function of BicD, and we discuss the hypothesis whereby BicDR might transport cargo more locally, with BicD transporting cargo over long distances, such as to the distal tip. We also identified embryonic proteins that interact with BicDR and appear to be BicDR cargo. For one of them, EF1γ (also known as eEF1γ), we show that the encoding gene EF1γ interacts with BicD and BicDR in the construction of the bristles.
Assuntos
Proteínas de Drosophila , Animais , Proteínas de Drosophila/genética , Proteínas de Drosophila/metabolismo , Dineínas/genética , Dineínas/metabolismo , Drosophila/metabolismo , Microtúbulos/metabolismo , Complexo Dinactina/genética , Complexo Dinactina/metabolismo , Proteínas Associadas aos Microtúbulos/metabolismoRESUMO
Epithelial polarity is critical for proper functions of epithelial tissues, tumorigenesis, and metastasis. The evolutionarily conserved transmembrane protein Crumbs (Crb) is a key regulator of epithelial polarity. Both Crb protein and its transcripts are apically localized in epithelial cells. However, it remains not fully understood how they are targeted to the apical domain. Here, using Drosophila ovarian follicular epithelia as a model, we show that epithelial polarity is lost and Crb protein is absent in the apical domain in follicular cells (FCs) in the absence of Diamond (Dind). Interestingly, Dind is found to associate with different components of the dynactin-dynein complex through co-IP-MS analysis. Dind stabilizes dynactin and depletion of dynactin results in almost identical defects as those observed in dind-defective FCs. Finally, both Dind and dynactin are also required for the apical localization of crb transcripts in FCs. Thus our data illustrate that Dind functions through dynactin/dynein-mediated transport of both Crb protein and its transcripts to the apical domain to control epithelial apico-basal (A/B) polarity.
Assuntos
Proteínas de Drosophila , Animais , Polaridade Celular , Drosophila/metabolismo , Drosophila melanogaster/metabolismo , Proteínas de Drosophila/genética , Proteínas de Drosophila/metabolismo , Complexo Dinactina/metabolismo , Dineínas/metabolismo , Células Epiteliais/metabolismo , Proteínas de Membrana/genética , Proteínas de Membrana/metabolismoRESUMO
Experimental studies in flies, mice, and humans suggest a significant role of impaired axonal transport in the pathogenesis of Alzheimer's disease (AD). The mechanisms underlying these impairments in axonal transport, however, remain poorly understood. Here we report that the Swedish familial AD mutation causes a standstill of the amyloid precursor protein (APP) in the axons at the expense of its reduced anterograde transport. The standstill reflects the perturbed directionality of the axonal transport of APP, which spends significantly more time traveling in the retrograde direction. This ineffective movement is accompanied by an enhanced association of dynactin-1 with APP, which suggests that reduced anterograde transport of APP is the result of enhanced activation of the retrograde molecular motor dynein by dynactin-1. The impact of the Swedish mutation on axonal transport is not limited to the APP vesicles since it also reverses the directionality of a subset of early endosomes, which become enlarged and aberrantly accumulate in distal locations. In addition, it also reduces the trafficking of lysosomes due to their less effective retrograde movement. Altogether, our experiments suggest a pivotal involvement of retrograde molecular motors and transport in the mechanisms underlying impaired axonal transport in AD and reveal significantly more widespread derangement of axonal transport pathways in the pathogenesis of AD.
Assuntos
Doença de Alzheimer , Precursor de Proteína beta-Amiloide , Transporte Axonal , Animais , Humanos , Camundongos , Doença de Alzheimer/metabolismo , Doença de Alzheimer/genética , Doença de Alzheimer/patologia , Precursor de Proteína beta-Amiloide/genética , Precursor de Proteína beta-Amiloide/metabolismo , Transporte Axonal/genética , Axônios/metabolismo , Axônios/patologia , Complexo Dinactina/metabolismo , Complexo Dinactina/genética , Dineínas/metabolismo , Endossomos/metabolismo , Endossomos/genética , Lisossomos/metabolismo , Mutação , Variação GenéticaRESUMO
Dynactin is a 1.1 MDa complex that activates the molecular motor dynein for ultra-processive transport along microtubules. In order to do this, it forms a tripartite complex with dynein and a coiled-coil adaptor. Dynactin consists of an actin-related filament whose length is defined by its flexible shoulder domain. Despite previous cryo-EM structures, the molecular architecture of the shoulder and pointed end of the filament is still poorly understood due to the lack of high-resolution information in these regions. Here we combine multiple cryo-EM datasets and define precise masking strategies for particle signal subtraction and 3D classification. This overcomes domain flexibility and results in high-resolution maps into which we can build the shoulder and pointed end. The unique architecture of the shoulder securely houses the p150 subunit and positions the four identical p50 subunits in different conformations to bind dynactin's filament. The pointed end map allows us to build the first structure of p62 and reveals the molecular basis for cargo adaptor binding to different sites at the pointed end.
Assuntos
Complexo Dinactina/química , Microscopia Crioeletrônica , Complexo Dinactina/metabolismo , Humanos , Simulação de Dinâmica Molecular , Domínios Proteicos , Multimerização Proteica , Subunidades Proteicas/química , Subunidades Proteicas/metabolismoRESUMO
Herpesvirus assembly requires the cytoplasmic association of large macromolecular and membrane structures that derive from both the nucleus and cytoplasmic membrane systems. Results from the study of human cytomegalovirus (HCMV) in cells where it organizes a perinuclear cytoplasmic virus assembly compartment (cVAC) show a clear requirement for the minus-end-directed microtubule motor, dynein, for virus assembly. In contrast, the assembly of herpes simplex virus -1 (HSV-1) in epithelial cells where it forms multiple dispersed, peripheral assembly sites is only mildly inhibited by the microtubule-depolymerizing agent, nocodazole. Here, we make use of a neuronal cell line system in which HSV-1 forms a single cVAC and show that dynein and its co-factor dynactin localize to the cVAC, and dynactin is associated with membranes that contain the virion tegument protein pUL11. We also show that the virus membrane-associated structural proteins pUL51 and the viral envelope glycoprotein gE arrive at the cVAC by different routes. Specifically, gE arrives at the cVAC after retrieval from the plasma membrane, suggesting the need for an intact retrograde transport system. Finally, we demonstrate that inhibition of dynactin function profoundly inhibits cVAC formation and virus production during the cytoplasmic assembly phase of infection.IMPORTANCEMany viruses reorganize cytoplasmic membrane systems and macromolecular transport systems to promote the production of progeny virions. Clarifying the mechanisms by which they accomplish this may reveal novel therapeutic strategies and illustrate mechanisms that are critical for normal cellular organization. Here, we explore the mechanism by which HSV-1 moves macromolecular and membrane cargo to generate a virus assembly compartment in the infected cell. We find that the virus makes use of a well-characterized, microtubule-based transport system that is stabilized against drugs that disrupt microtubules.
Assuntos
Membrana Celular , Complexo Dinactina , Dineínas , Herpesvirus Humano 1 , Proteínas Associadas aos Microtúbulos , Neurônios , Proteínas do Envelope Viral , Montagem de Vírus , Herpesvirus Humano 1/fisiologia , Herpesvirus Humano 1/metabolismo , Dineínas/metabolismo , Membrana Celular/metabolismo , Membrana Celular/virologia , Humanos , Neurônios/virologia , Neurônios/metabolismo , Complexo Dinactina/metabolismo , Proteínas do Envelope Viral/metabolismo , Proteínas Associadas aos Microtúbulos/metabolismo , Linhagem Celular , Animais , Compartimentos de Replicação Viral/metabolismo , Microtúbulos/metabolismoRESUMO
The endocytic adaptor protein 2 (AP-2) complex binds dynactin as part of its noncanonical function, which is necessary for dynein-driven autophagosome transport along microtubules in neuronal axons. The absence of this AP-2-dependent transport causes neuronal morphology simplification and neurodegeneration. The mechanisms that lead to formation of the AP-2-dynactin complex have not been studied to date. However, the inhibition of mammalian/mechanistic target of rapamycin complex 1 (mTORC1) enhances the transport of newly formed autophagosomes by influencing the biogenesis and protein interactions of Rab-interacting lysosomal protein (RILP), another dynein cargo adaptor. We tested effects of mTORC1 inhibition on interactions between the AP-2 and dynactin complexes, with a focus on their two essential subunits, AP-2ß and p150Glued. We found that the mTORC1 inhibitor rapamycin enhanced p150Glued-AP-2ß complex formation in both neurons and non-neuronal cells. Additional analysis revealed that the p150Glued-AP-2ß interaction was indirect and required integrity of the dynactin complex. In non-neuronal cells rapamycin-driven enhancement of the p150Glued-AP-2ß interaction also required the presence of cytoplasmic linker protein 170 (CLIP-170), the activation of autophagy, and an undisturbed endolysosomal system. The rapamycin-dependent p150Glued-AP-2ß interaction occurred on lysosomal-associated membrane protein 1 (Lamp-1)-positive organelles but without the need for autolysosome formation. Rapamycin treatment also increased the acidification and number of acidic organelles and increased speed of the long-distance retrograde movement of Lamp-1-positive organelles. Altogether, our results indicate that autophagy regulates the p150Glued-AP-2ß interaction, possibly to coordinate sufficient motor-adaptor complex availability for effective lysosome transport.
Assuntos
Autofagia , Complexo Dinactina , Lisossomos , Animais , Humanos , Camundongos , Complexo 2 de Proteínas Adaptadoras/metabolismo , Autofagossomos/metabolismo , Complexo Dinactina/metabolismo , Proteína 1 de Membrana Associada ao Lisossomo/metabolismo , Lisossomos/metabolismo , Alvo Mecanístico do Complexo 1 de Rapamicina/metabolismo , Neurônios/metabolismo , Ligação Proteica , Sirolimo/farmacologiaRESUMO
Regulation of organelle transport by molecular motors along the cytoskeletal microtubules is central to maintaining cellular functions. Here, we show that the ubiquitous tau-related microtubule-associated protein 4 (MAP4) can bias the bidirectional transport of organelles toward the microtubule minus-ends. This is concurrent with MAP4 phosphorylation, mediated by the kinase GSK3ß. We demonstrate that MAP4 achieves this bias by tethering the cargo to the microtubules, allowing it to impair the force generation of the plus-end motor kinesin-1. Consistent with this mechanism, MAP4 physically interacts with dynein and dynactin and, when phosphorylated, associates with the cargo-motor complex through its projection domain. Its phosphorylation coincides with the perinuclear accumulation of organelles, a phenotype that is rescued by abolishing the cargo-microtubule MAP4 tether or by the pharmacological inhibition of dynein, confirming the ability of kinesin to inch along, albeit inefficiently, in the presence of phosphorylated MAP4. These findings have broad biological significance because of the ubiquity of MAP4 and the involvement of GSK3ß in multiple diseases, more specifically in cancer, where the MAP4-dependent redistribution of organelles may be prevalent in cancer cells, as we demonstrate here for mitochondria in lung carcinoma epithelial cells.
Assuntos
Dineínas , Cinesinas , Complexo Dinactina/metabolismo , Dineínas/metabolismo , Glicogênio Sintase Quinase 3 beta/genética , Glicogênio Sintase Quinase 3 beta/metabolismo , Proteínas Associadas aos Microtúbulos/genética , Proteínas Associadas aos Microtúbulos/metabolismo , Microtúbulos/metabolismo , Organelas/metabolismoRESUMO
Dynactin subunit 2 (DCTN2) has been reported to play a role in progression of several tumours; however, the involvement of DCTN2 in potential mechanism or the tumour immune microenvironment among various cancers still remains largely unknown. Therefore, the objective of this study was to comprehensively investigate the expression status and potential function of DCTN2 in various malignancies through different database, such as The Cancer Genome Atlas, the Genotype-Tissue Expression and Gene Expression Omnimus databases. We discovered that DCTN2 expression was high in many type of tumours tissues compared to adjacent non-tumour ones. High DCTN2 signified poor prognosis for patients with tumours. Additionally, Gene Set Enrichment Analysis (GSEA) analysis revealed that DCTN2 was positively correlated with oncogenic pathways, including cell cycle, tumour metastasis-related pathway, while it was negatively with anti-tumour immune signalling pathway, such as INF-γ response. More importantly, we elucidated the functional impact of DCTN2 on hepatocellular carcinoma (HCC) progression and its underlying mechanisms. DCTN2 expression was much higher in HCC tissues than in adjacent non-tumour tissues. Silencing DCTN2 dramatically suppressed the proliferative and metastasis capacities of tumour cell in vitro. Mechanistically, DCTN2 exerted tumour-promoting effects by modulating the AKT signalling pathway. DCTN2 knockdown in HCC cells inhibited AKT phosphorylation and its downstream targets as well. Rescue experiments revealed that the anti-tumour effects of DCTN2 knockdown were partially reversed upon AKT pathway activation. Overall, DCTN2 may be a potent biomarker signifying tumour prognosis and a promising therapeutic target for tumour treatment, particularly in HCC.
Assuntos
Carcinoma Hepatocelular , Proliferação de Células , Regulação Neoplásica da Expressão Gênica , Neoplasias Hepáticas , Proteínas Proto-Oncogênicas c-akt , Transdução de Sinais , Humanos , Carcinoma Hepatocelular/genética , Carcinoma Hepatocelular/patologia , Carcinoma Hepatocelular/metabolismo , Linhagem Celular Tumoral , Movimento Celular/genética , Proliferação de Células/genética , Complexo Dinactina/metabolismo , Complexo Dinactina/genética , Neoplasias Hepáticas/genética , Neoplasias Hepáticas/patologia , Neoplasias Hepáticas/metabolismo , Prognóstico , Proteínas Proto-Oncogênicas c-akt/metabolismo , Proteínas Proto-Oncogênicas c-akt/genética , Microambiente Tumoral/genéticaRESUMO
Dynein is the primary minus-end-directed microtubule motor protein. To achieve activation, dynein binds to the dynactin complex and an adaptor to form the "activated dynein complex." The protein Lis1 aids activation by binding to dynein and promoting its association with dynactin and the adaptor. Ndel1 and its paralog Nde1 are dynein- and Lis1-binding proteins that help control dynein localization within the cell. Cell-based assays suggest that Ndel1-Nde1 also work with Lis1 to promote dynein activation, although the underlying mechanism is unclear. Using purified proteins and quantitative binding assays, here we found that the C-terminal region of Ndel1 contributes to dynein binding and negatively regulates binding to Lis1. Using single-molecule imaging and protein biochemistry, we observed that Ndel1 inhibits dynein activation in two distinct ways. First, Ndel1 disfavors the formation of the activated dynein complex. We found that phosphomimetic mutations in the C-terminal domain of Ndel1 increase its ability to inhibit dynein-dynactin-adaptor complex formation. Second, we observed that Ndel1 interacts with dynein and Lis1 simultaneously and sequesters Lis1 away from its dynein-binding site. In doing this, Ndel1 prevents Lis1-mediated dynein activation. Together, our work suggests that in vitro, Ndel1 is a negative regulator of dynein activation, which contrasts with cellular studies where Ndel1 promotes dynein activity. To reconcile our findings with previous work, we posit that Ndel1 functions to scaffold dynein and Lis1 together while keeping dynein in an inhibited state. We speculate that Ndel1 release can be triggered in cellular settings to allow for timed dynein activation.
Assuntos
Proteínas de Transporte , Complexo Dinactina , Dineínas , Proteínas Associadas aos Microtúbulos , 1-Alquil-2-acetilglicerofosfocolina Esterase/genética , 1-Alquil-2-acetilglicerofosfocolina Esterase/metabolismo , Citoesqueleto/metabolismo , Complexo Dinactina/genética , Complexo Dinactina/metabolismo , Dineínas/genética , Dineínas/metabolismo , Proteínas Associadas aos Microtúbulos/genética , Proteínas Associadas aos Microtúbulos/metabolismo , Microtúbulos/metabolismo , Humanos , Proteínas de Transporte/genética , Proteínas de Transporte/metabolismoRESUMO
Although subcellular positioning of endosomes significantly impacts on their functions, the molecular mechanisms governing the different steady-state distribution of early endosomes (EEs) and late endosomes (LEs)/lysosomes (LYs) in peripheral and perinuclear eukaryotic cell areas, respectively, are still unsolved. We unveil that such differences arise because, while LE retrograde transport depends on the dynein microtubule (MT) motor only, the one of EEs requires the cooperative antagonism of dynein and kinesin-14 KIFC1, a MT minus end-directed motor involved in cancer progression. Mechanistically, the Ser-x-Ile-Pro (SxIP) motif-mediated interaction of the endoplasmic reticulum transmembrane protein stromal interaction molecule 1 (STIM1) with the MT plus end-binding protein 1 (EB1) promotes its association with the p150Glued subunit of the dynein activator complex dynactin and the distinct location of EEs and LEs/LYs. The peripheral distribution of EEs requires their p150Glued-mediated simultaneous engagement with dynein and SxIP motif-containing KIFC1, via HOOK1 and HOOK3 adaptors, respectively. In sum, we provide evidence that distinct minus end-directed MT motor systems drive the differential transport and subcellular distribution of EEs and LEs in mammalian cells.
Assuntos
Transporte Biológico/fisiologia , Endossomos/metabolismo , Microtúbulos/metabolismo , Adesão Celular , Linhagem Celular , Citoesqueleto , Complexo Dinactina/metabolismo , Dineínas/metabolismo , Retículo Endoplasmático/metabolismo , Inativação Gênica , Humanos , Cinesinas/genética , Cinesinas/metabolismo , Lisossomos/metabolismo , Proteínas de Membrana/metabolismo , Proteínas Associadas aos Microtúbulos/metabolismo , Proteínas de Neoplasias , Molécula 1 de Interação Estromal/genética , Molécula 1 de Interação Estromal/metabolismoRESUMO
Proper mitotic spindle orientation depends on the correct anchorage of astral microtubules to the cortex. It relies on the remodeling of the cell cortex, a process not fully understood. Annexin A2 (Anx2; also known as ANXA2) is a protein known to be involved in cortical domain remodeling. Here, we report that in HeLa cell early mitosis, Anx2 recruits the scaffold protein Ahnak at the cell cortex facing spindle poles, and the distribution of both proteins is controlled by cell adhesion. Depletion of either protein or impaired cortical Ahnak localization result in delayed anaphase onset and unstable spindle anchoring, which leads to altered spindle orientation. We find that Ahnak is present in a complex with dynein-dynactin. Furthermore, Ahnak and Anx2 are required for correct dynein and NuMA (also known as NUMA1) cortical localization and dynamics. We propose that the Ahnak-Anx2 complex influences the cortical organization of the astral microtubule-anchoring complex, and thereby mitotic spindle positioning in human cells. This article has an associated First Person interview with the first author of the paper.
Assuntos
Anexina A2 , Dineínas , Anáfase , Anexina A2/genética , Anexina A2/metabolismo , Proteínas de Ciclo Celular/genética , Proteínas de Ciclo Celular/metabolismo , Complexo Dinactina/metabolismo , Dineínas/metabolismo , Células HeLa , Humanos , Proteínas de Membrana/genética , Proteínas de Membrana/metabolismo , Proteínas Associadas aos Microtúbulos/genética , Proteínas Associadas aos Microtúbulos/metabolismo , Microtúbulos/metabolismo , Mitose , Proteínas de Neoplasias/metabolismo , Fuso Acromático/metabolismoRESUMO
The microtubule motor cytoplasmic dynein 1 (dynein) and its essential activator dynactin have conserved roles in spindle assembly and positioning during female meiosis and mitosis, but their contribution to male meiosis remains poorly understood. Here, we characterize the G33S mutation in the C. elegans dynactin subunit DNC-1, which corresponds to G59S in human p150Glued that causes motor neuron disease. In spermatocytes, dnc-1(G33S) delays spindle assembly and penetrantly inhibits anaphase spindle elongation in meiosis I, which prevents the segregation of homologous chromosomes. By contrast, chromosomes segregate without errors in the early dnc-1(G33S) embryo. Deletion of the DNC-1 N-terminus shows that defective meiosis in dnc-1(G33S) spermatocytes is not due to the inability of DNC-1 to interact with microtubules. Instead, our results suggest that the DNC-1(G33S) protein, which is aggregation prone in vitro, is less stable in spermatocytes than the early embryo, resulting in different phenotypic severity in the two dividing tissues. Thus, the dnc-1(G33S) mutant reveals that dynein-dynactin drive meiotic chromosome segregation in spermatocytes and illustrates that the extent to which protein misfolding leads to loss of function can vary significantly between cell types.