Dynein-dynactin segregate meiotic chromosomes in C. elegans spermatocytes

ABSTRACTThe 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.

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Dynein-dynactin segregate meiotic chromosomes in C. elegans spermatocytes

10.1101/2020.10.19.345041 ◽

2020 ◽

Author(s):

Daniel J. Barbosa ◽

Vanessa Teixeira ◽

Joana Duro ◽

Ana X. Carvalho ◽

Reto Gassmann

Keyword(s):

Chromosome Segregation ◽

Protein Misfolding ◽

Meiotic Chromosome ◽

Spindle Assembly ◽

Cell Types ◽

Early Embryo ◽

Loss Of Function ◽

C Elegans ◽

Spindle Elongation

ABSTRACTThe dynactin complex is an essential co-factor of the microtubule-based motor dynein. Dynein-dynactin have well-documented roles in spindle assembly and positioning during C. elegans female meiosis and embryonic mitosis, while dynein-dynactin’s contribution to male meiosis has not been investigated. Here, we characterize the G33S mutation in DNC-1’s N-terminal microtubule binding domain, which corresponds to G59S in the human dynactin subunit p150/Glued that causes motor neuron disease. In spermatocytes, dnc-1(G33S) delays spindle assembly and penetrantly inhibits anaphase spindle elongation in meiosis I, which prevents homologous chromosome segregation and generates aneuploid sperm with an extra centrosome. Consequently, embryos produced by dnc-1(G33S) hermaphrodites exhibit a high incidence of tetrapolar mitotic spindles, yet dnc-1(G33S) embryos with bipolar spindles proceed through early mitotic divisions without errors in chromosome segregation. Deletion of the DNC-1 N-terminus shows that defective meiosis in dnc-1(G33S) spermatocytes is not due to DNC-1’s inability to interact with microtubules. Rather, 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 unusual hypomorphic nature of 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.

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Abstract 18: Synoviolin, an E3 Ubiquitin Ligase, Modulates Cardiac Myocyte Size and Restores Heart Function in Hypertrophic Cardiomyopathy

Circulation Research ◽

10.1161/res.111.suppl_1.a18 ◽

2012 ◽

Vol 111 (suppl_1) ◽

Author(s):

Shirin Doroudgar ◽

Mirko Völkers ◽

Donna J Thuerauf ◽

Ashley Bumbar ◽

Mohsin Khan ◽

...

Keyword(s):

Ubiquitin Ligase ◽

Protein Misfolding ◽

Cardiac Myocyte ◽

Protein Quality ◽

Heart Function ◽

E3 Ubiquitin Ligase ◽

Ubiquitin Ligases ◽

Calcium Handling ◽

Loss Of Function

The endoplasmic reticulum (ER) is essential for protein homeostasis, or proteostasis, which governs the balance of the proteome. In addition to secreted and membrane proteins, proteins bound for many other cellular locations are also made on ER-bound ribosomes, emphasizing the importance of protein quality and quantity control in the ER. Unlike cytosolic E3 ubiquitin ligases studied in the heart, synoviolin/Hrd1, which has not been studied in the heart, is an ER transmembrane E3 ubiquitin ligase, which we found to be upregulated upon protein misfolding in cardiac myocytes. Given the strategic location of synoviolin in the ER membrane, we addressed the hypothesis that synoviolin is critical for regulating the balance of the proteome, and accordingly, myocyte size. We showed that in vitro, adenovirus-mediated overexpression of synoviolin decreased cardiac myocyte size and protein synthesis, but unlike atrophy-related ubiquitin ligases, synoviolin did not increase global protein degradation. Furthermore, targeted gene therapy using adeno-associated virus 9 (AAV9) showed that overexpression of synoviolin in the left ventricle attenuated maladaptive cardiac hypertrophy and preserved cardiac function in mice subjected to trans-aortic constriction (AAV9-control TAC = 22.5 ± 6.2% decrease in EF vs. AAV9-synoviolin TAC at 6 weeks post TAC; P<0.001), and decreased mTOR activity. Since calcium is a major regulator of cardiac myocyte size, we examined the effects of synoviolin gain- or loss-of-function, using AAV9-synoviolin, or an miRNA designed to knock down synoviolin, respectively. While synoviolin gain-of-function did not affect calcium handling in isolated adult myocytes, synoviolin loss-of-function increased calcium transient amplitude (P<0.01), prolonged spark duration (P<0.001), and increased spark width (P<0.001). Spark frequency and amplitude were unaltered upon synoviolin gain- or loss-of-function. Whereas SR calcium load was unaltered by synoviolin loss-of-function, SERCA-mediated calcium removal was reduced (P<0.05). In conclusion, our studies suggest that in the heart, synoviolin is 1) a critical component of proteostasis, 2) a novel determinant of cardiac myocyte size, and 3) necessary for proper calcium handling.

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Assessment of phagocytic activity in live macrophages-tumor cells co-cultures by Confocal and Nomarski Microscopy

Biology Methods and Protocols ◽

10.1093/biomethods/bpx002 ◽

2017 ◽

Vol 2 (1) ◽

Cited By ~ 5

Author(s):

Dalia Martinez-Marin ◽

Courtney Jarvis ◽

Thomas Nelius ◽

Stéphanie Filleur

Keyword(s):

Tumor Microenvironment ◽

Tumor Cells ◽

Phagocytic Activity ◽

Molecular Mechanisms ◽

Cell Types ◽

Functional Assay ◽

Loss Of Function ◽

Multiple Cancer

Abstract Macrophages have been recognized as the main inflammatory component of the tumor microenvironment. Although often considered as beneficial for tumor growth and disease progression, tumor-associated macrophages have also been shown to be detrimental to the tumor depending on the tumor microenvironment. Therefore, understanding the molecular interactions between macrophages and tumor cells in relation to macrophages functional activities such as phagocytosis is critical for a better comprehension of their tumor-modulating action. Still, the characterization of these molecular mechanisms in vivo remains complicated due to the extraordinary complexity of the tumor microenvironment and the broad range of tumor-associated macrophage functions. Thus, there is an increasing demand for in vitro methodologies to study the role of cell–cell interactions in the tumor microenvironment. In the present study, we have developed live co-cultures of macrophages and human prostate tumor cells to assess the phagocytic activity of macrophages using a combination of Confocal and Nomarski Microscopy. Using this model, we have emphasized that this is a sensitive, measurable, and highly reproducible functional assay. We have also highlighted that this assay can be applied to multiple cancer cell types and used as a selection tool for a variety of different types of phagocytosis agonists. Finally, combining with other studies such as gain/loss of function or signaling studies remains possible. A better understanding of the interactions between tumor cells and macrophages may lead to the identification of new therapeutic targets against cancer.

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Macroautophagy is dispensable for growth of KRAS mutant tumors and chloroquine efficacy

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1515617113 ◽

2015 ◽

Vol 113 (1) ◽

pp. 182-187 ◽

Cited By ~ 124

Author(s):

Christina H. Eng ◽

Zuncai Wang ◽

Diane Tkach ◽

Lourdes Toral-Barza ◽

Savuth Ugwonali ◽

...

Keyword(s):

Anticancer Agents ◽

Kinase Inhibitors ◽

Cell Types ◽

Loss Of Function ◽

Growth And Survival ◽

Oncogenic Mutations ◽

Cellular Context ◽

Genetic Stratification

Macroautophagy is a key stress-response pathway that can suppress or promote tumorigenesis depending on the cellular context. Notably, Kirsten rat sarcoma (KRAS)-driven tumors have been reported to rely on macroautophagy for growth and survival, suggesting a potential therapeutic approach of using autophagy inhibitors based on genetic stratification. In this study, we evaluated whether KRAS mutation status can predict the efficacy to macroautophagy inhibition. By profiling 47 cell lines with pharmacological and genetic loss-of-function tools, we were unable to confirm that KRAS-driven tumor lines require macroautophagy for growth. Deletion of autophagy-related 7 (ATG7) by genome editing completely blocked macroautophagy in several tumor lines with oncogenic mutations in KRAS but did not inhibit cell proliferation in vitro or tumorigenesis in vivo. Furthermore, ATG7 knockout did not sensitize cells to irradiation or to several anticancer agents tested. Interestingly, ATG7-deficient and -proficient cells were equally sensitive to the antiproliferative effect of chloroquine, a lysosomotropic agent often used as a pharmacological tool to evaluate the response to macroautophagy inhibition. Moreover, both cell types manifested synergistic growth inhibition when treated with chloroquine plus the tyrosine kinase inhibitors erlotinib or sunitinib, suggesting that the antiproliferative effects of chloroquine are independent of its suppressive actions on autophagy.

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Evidence that myosin does not contribute to force production in chromosome movement.

The Journal of Cell Biology ◽

10.1083/jcb.94.1.165 ◽

1982 ◽

Vol 94 (1) ◽

pp. 165-178 ◽

Cited By ~ 74

Author(s):

D P Kiehart ◽

I Mabuchi ◽

S Inoué

Keyword(s):

Gamma Globulin ◽

Meiotic Chromosome ◽

Force Production ◽

Chromosome Movement ◽

Actomyosin Interaction ◽

Dividing Cells ◽

Spindle Elongation ◽

Chromosome Movements

Antibody against cytoplasmic myosin, when microinjected into actively dividing cells, provides a physiological test for the role of actin and myosin in chromosome movement. Anti-Asterias egg myosin, characterized by Mabuchi and Okuno (1977, J. Cell Biol., 74:251), completely and specifically inhibits the actin activated Mg++ -ATPase of myosin in vitro and, when microinjected, inhibits cytokinesis in vivo. Here, we demonstrate that microinjected antibody has no observable effect on the rate or extent of anaphase chromosome movements. Neither central spindle elongation nor chromosomal fiber shortening is affected by doses up to eightfold higher than those require to uniformly inhibit cytokinesis in all injected cells. We calculate that such doses are sufficient to completely inhibit myosin ATPase activity in these cells. Cells injected with buffer alone, with myosin-absorbed antibody, or with nonimmune gamma-globulin, proceed normally through both mitosis and cytokinesis. Control gamma-globulin, labeled with fluorescein, diffuses to homogeneity throughout the cytoplasm in 2-4 min and remains uniformly distributed. Antibody is not excluded from the spindle region. Prometaphase chromosome movements, fertilization, pronuclear migration, and pronuclear fusion are also unaffected by microinjected antimyosin. These experiments demonstrate that antimyosin blocks the actomyosin interaction thought to be responsible for force production in cytokinesis but has no effect on mitotic or meiotic chromosome motion. They provide direct physiological evidence that myosin is not involved in force production for chromosome movement.

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Intracellular organelles mediate cytoplasmic pulling force for centrosome centration in the Caenorhabditis elegans early embryo

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1013275108 ◽

2010 ◽

Vol 108 (1) ◽

pp. 137-142 ◽

Cited By ~ 89

Author(s):

Kenji Kimura ◽

Akatsuki Kimura

Keyword(s):

Caenorhabditis Elegans ◽

Mammalian Cells ◽

Cytoplasmic Dynein ◽

Early Embryo ◽

Organelle Transport ◽

Animal Cells ◽

C Elegans ◽

Cell Functions ◽

Intracellular Organelles ◽

Pulling Force

The centrosome is generally maintained at the center of the cell. In animal cells, centrosome centration is powered by the pulling force of microtubules, which is dependent on cytoplasmic dynein. However, it is unclear how dynein brings the centrosome to the cell center, i.e., which structure inside the cell functions as a substrate to anchor dynein. Here, we provide evidence that a population of dynein, which is located on intracellular organelles and is responsible for organelle transport toward the centrosome, generates the force required for centrosome centration in Caenorhabditis elegans embryos. By using the database of full-genome RNAi in C. elegans, we identified dyrb-1, a dynein light chain subunit, as a potential subunit involved in dynein anchoring for centrosome centration. DYRB-1 is required for organelle movement toward the minus end of the microtubules. The temporal correlation between centrosome centration and the net movement of organelle transport was found to be significant. Centrosome centration was impaired when Rab7 and RILP, which mediate the association between organelles and dynein in mammalian cells, were knocked down. These results indicate that minus end-directed transport of intracellular organelles along the microtubules is required for centrosome centration in C. elegans embryos. On the basis of this finding, we propose a model in which the reaction forces of organelle transport generated along microtubules act as a driving force that pulls the centrosomes toward the cell center. This is the first model, to our knowledge, providing a mechanical basis for cytoplasmic pulling force for centrosome centration.

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Oxidative stress-induced parkin misfolding, aggregation, and toxicity

10.21203/rs.3.rs-33898/v1 ◽

2020 ◽

Author(s):

Martin Duennwald ◽

Gary S. Shaw ◽

Mohammad A. Esmaeili ◽

Jane R. Rylett ◽

Susanne Schmid ◽

...

Keyword(s):

Oxidative Stress ◽

Disulfide Bonds ◽

Protein Misfolding ◽

Protein Quality ◽

Normal Growth ◽

Growth Conditions ◽

Cellular Protein ◽

Loss Of Function ◽

Underlying Mechanisms

Abstract Background: Excess oxidative stress and protein misfolding are major hallmarks of neurodegenerative disease, including Parkinson’s disease (PD). Mutations in the genes encoding the ubiquitin ligase parkin cause autosomal recessive juvenile forms of Parkinsonism by the loss of parkin function in mitochondrial homeostasis and cellular protein quality control, generally. Dysfunction of parkin might also contribute to sporadic forms of PD, yet the underlying mechanisms remain mostly unexplored. Methods: We obtained key results from studies in human PD brains, a mouse model, yeast, cultured neuronal cells, and in vitro biochemistry. Human postmortem Medial Temporal Gyrus tissue was fixed for immunohistochemistry. We performed biochemical analyses of protein lysates from human brain, mouse brain, yeast and cells to assess parkin modification by oxidative stress under normal growth conditions and more so under oxidative stress. Results: Our results reveal that oxidative stress damages parkin by inducing the formation of aberrant intra- and inter-molecular disulfide bonds, leading to parkin misfolding and inclusion formation, which is toxic to cells. We furthermore find that parkin is most severely oxidized in its active conformation. Conclusion: Collectively, our study identifies a mechanism by which protein oxidation can contribute to neurodegeneration in PD by combining loss of function with toxic gain of function mechanisms.

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Acentrosomal spindle assembly and stability in C. elegans oocytes requires a kinesin-12 non-motor microtubule interaction domain

10.1101/2021.06.17.448874 ◽

2021 ◽

Author(s):

Ian Daniel Wolff ◽

Jeremy Alden Hollis ◽

Sarah Marie Wignall

Keyword(s):

Adaptor Protein ◽

Direct Interaction ◽

Spindle Assembly ◽

Meiotic Spindle ◽

Interaction Domain ◽

Microtubule Binding ◽

C Elegans ◽

Insight Into

During the meiotic divisions in oocytes, microtubules are sorted and organized by motor proteins to generate a bipolar spindle in the absence of centrosomes. In most organisms, kinesin-5 family members crosslink and slide microtubules to generate outward force that promotes acentrosomal spindle bipolarity. However, the mechanistic basis for how other kinesin families act on acentrosomal spindles has not been explored. We investigated this question in C. elegans oocytes, where kinesin-5 is not required to generate outward force. Instead, the kinesin-12 family motor KLP-18 performs this function. KLP-18 acts with adaptor protein MESP-1 (meiotic spindle 1) to sort microtubule minus ends to the periphery of a microtubule array, where they coalesce into spindle poles. If either of these proteins is depleted, outward sorting of microtubules is lost and minus ends converge to form a monoaster. Here we use a combination of in vitro biochemical assays and in vivo mutant analysis to provide insight into the mechanism by which these proteins collaborate to promote acentrosomal spindle assembly. We identify a microtubule binding site on the C-terminal stalk of KLP-18 and demonstrate that a direct interaction between the KLP-18 stalk and MESP-1 activates non-motor microtubule binding. We also provide evidence that this C-terminal domain is required for KLP-18 activity during spindle assembly and show that KLP-18 is continuously required to maintain spindle bipolarity. This study thus provides new insight into the construction and maintenance of the oocyte acentrosomal spindle as well as into kinesin-12 mechanism and regulation.

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Meiotic Chromosome Synapsis and XY-Body Formation In Vitro

Frontiers in Endocrinology ◽

10.3389/fendo.2021.761249 ◽

2021 ◽

Vol 12 ◽

Author(s):

Qijing Lei ◽

Eden Zhang ◽

Ans M. M. van Pelt ◽

Geert Hamer

Keyword(s):

Culture System ◽

Meiotic Chromosome ◽

Cell Types ◽

Germline Stem Cells ◽

Culture Dish ◽

Body Formation ◽

Xy Body ◽

Chromosome Synapsis

To achieve spermatogenesis in vitro, one of the most challenging processes to mimic is meiosis. Meiotic problems, like incomplete synapsis of the homologous chromosomes, or impaired homologous recombination, can cause failure of crossover formation and subsequent chromosome nondisjunction, eventually leading to aneuploid sperm. These meiotic events are therefore strictly monitored by meiotic checkpoints that initiate apoptosis of aberrant spermatocytes and lead to spermatogenic arrest. However, we recently found that, in vitro derived meiotic cells proceeded to the first meiotic division (MI) stage, despite displaying incomplete chromosome synapsis, no discernible XY-body and lack of crossover formation. We therefore optimized our in vitro culture system of meiosis from male germline stem cells (mGSCs) in order to achieve full chromosome synapsis, XY-body formation and meiotic crossovers. In comparison to previous culture system, the in vitro-generated spermatocytes were transferred after meiotic initiation to a second culture dish. This dish already contained a freshly plated monolayer of proliferatively inactivated immortalized Sertoli cells supporting undifferentiated mGSCs. In this way we aimed to simulate the multiple layers of germ cell types that support spermatogenesis in vivo in the testis. We found that in this optimized culture system, although independent of the undifferentiated mGSCs, meiotic chromosome synapsis was complete and XY body appeared normal. However, meiotic recombination still occurred insufficiently and only few meiotic crossovers were formed, leading to MI-spermatocytes displaying univalent chromosomes (paired sister chromatids). Therefore, considering that meiotic checkpoints are not necessarily fully functional in vitro, meiotic crossover formation should be closely monitored when mimicking gametogenesis in vitro to prevent generation of aneuploid gametes.

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Pharmacological and functional similarities of the human neuropeptide Y system in C. elegans challenges phylogenetic views on the FLP/NPR system

Cell Communication and Signaling ◽

10.1186/s12964-019-0436-1 ◽

2019 ◽

Vol 17 (1) ◽

Author(s):

Miron Mikhailowitsch Gershkovich ◽

Victoria Elisabeth Groß ◽

Anette Kaiser ◽

Simone Prömel

Keyword(s):

Neuropeptide Y ◽

Pharmacological Study ◽

Receptor Activation ◽

Cross Reactivity ◽

Model Organisms ◽

Loss Of Function ◽

C Elegans ◽

Molecular Studies

Abstract Background The neuropeptide Y system affects various processes, among others food intake, and is frequently discussed in the context of targeting obesity. Studies in model organisms are indispensable to enable molecular studies in a physiological context. Although the NPY system is evolutionarily conserved in all bilaterians, in the widely used model Caenorhabditis elegans there is controversy on the existence of NPY orthologous molecules. While the FMRFamide-like peptide (FLP)/Neuropeptide receptor-Resemblance (NPR) system in the nematode was initially suggested to be orthologous to the mammalian NPY system, later global phylogenetic studies indicate that FLP/NPR is protostome-specific. Methods We performed a comprehensive pharmacological study of the FLP/NPR system in transfected cells in vitro, and tested for functional substitution in C. elegans knockout strains. Further, we phenotypically compared different flp loss-of-function strains. Differences between groups were compared by ANOVA and post-hoc testing (Dunnett, Bonferroni). Results Our pharmacological analysis of the FLP/NPR system including formerly functionally uncharacterized NPY-like peptides from C. elegans demonstrates that G protein-coupling and ligand requirements for receptor activation are similar to the human NPY system. In vitro and in vivo analyses show cross-reactivity of NPY with the FLP/NPR system manifesting in the ability of the human GPCRs to functionally substitute FLP/NPR signaling in vivo. The high pharmacological/functional similarities enabled us to identify C. elegans FLP-14 as a key molecule in avoidance behavior. Conclusions Our data demonstrate the pharmacological and functional similarities of human NPY and C. elegans NPR systems. This adds a novel perspective to current phylogenetic reconstructions of the neuropeptide Y system. NPY and NPR receptors are pharmacologically so similar that the human receptors can functionally compensate for the C. elegans ones, suggesting orthologous relationships. This is also underlined by the presence of NPY-like peptides and parallels in peptide requirements for receptor activation. Further, the results presented here highlight the potential of this knowledge for physiological as well as molecular studies on neuropeptide GPCRs such as the NPY system in the future.

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