Structural organization of the C1a-e-c supercomplex within the ciliary central apparatus
Nearly all motile cilia contain a central apparatus (CA) composed of two connected singlet microtubules with attached projections that play crucial roles in regulating ciliary motility. Defects in CA assembly usually result in motility-impaired or paralyzed cilia, which in humans causes disease. Despite their importance, the protein composition and functions of the CA projections are largely unknown. Here, we integrated biochemical and genetic approaches with cryo-electron tomography to compare the CA of wild-type Chlamydomonas with CA mutants. We identified a large (>2 MD) complex, the C1a-e-c supercomplex, that requir...
Source: Journal of Cell Biology - December 1, 2019 Category: Cytology Authors: Fu, G., Zhao, L., Dymek, E., Hou, Y., Song, K., Phan, N., Shang, Z., Smith, E. F., Witman, G. B., Nicastro, D. Tags: Cilia, Migration, Motility, Biophysics, Structural Biology Articles Source Type: research
Mechanosensing during directed cell migration requires dynamic actin polymerization at focal adhesions
The mechanical properties of a cell’s microenvironment influence many aspects of cellular behavior, including cell migration. Durotaxis, the migration toward increasing matrix stiffness, has been implicated in processes ranging from development to cancer. During durotaxis, mechanical stimulation by matrix rigidity leads to directed migration. Studies suggest that cells sense mechanical stimuli, or mechanosense, through the acto-myosin cytoskeleton at focal adhesions (FAs); however, FA actin cytoskeletal remodeling and its role in mechanosensing are not fully understood. Here, we show that the Ena/VASP family member, ...
Source: Journal of Cell Biology - December 1, 2019 Category: Cytology Authors: Puleo, J. I., Parker, S. S., Roman, M. R., Watson, A. W., Eliato, K. R., Peng, L., Saboda, K., Roe, D. J., Ros, R., Gertler, F. B., Mouneimne, G. Tags: Cytoskeleton, Migration, Motility, Biophysics, Cancer Articles Source Type: research
Par-1 controls the composition and growth of cortical actin caps during Drosophila embryo cleavage
Cell structure depends on the cortex, a thin network of actin polymers and additional proteins underlying the plasma membrane. The cell polarity kinase Par-1 is required for cells to form following syncytial Drosophila embryo development. This requirement stems from Par-1 promoting cortical actin caps that grow into dome-like metaphase compartments for dividing syncytial nuclei. We find the actin caps to be a composite material of Diaphanous (Dia)-based actin bundles interspersed with independently formed, Arp2/3-based actin puncta. Par-1 and Dia colocalize along extended regions of the bundles, and both are required for t...
Source: Journal of Cell Biology - December 1, 2019 Category: Cytology Authors: Jiang, T., Harris, T. J. C. Tags: Cytoskeleton, Development Articles Source Type: research
Two S. pombe septation phases differ in ingression rate, septum structure, and response to F-actin loss
In fission yeast, cytokinesis requires a contractile actomyosin ring (CR) coupled to membrane and septum ingression. Septation proceeds in two phases. In anaphase B, the septum ingresses slowly. During telophase, the ingression rate increases, and the CR becomes dispensable. Here, we explore the relationship between the CR and septation by analyzing septum ultrastructure, ingression, and septation proteins in cells lacking F-actin. We show that the two phases of septation correlate with septum maturation and the response of cells to F-actin removal. During the first phase, the septum is immature and, following F-actin remo...
Source: Journal of Cell Biology - December 1, 2019 Category: Cytology Authors: Ramos, M., Cortes, J. C. G., Sato, M., Rincon, S. A., Moreno, M. B., Clemente-Ramos, J. A., Osumi, M., Perez, P., Ribas, J. C. Tags: Cell Cycle and Division, Development Articles Source Type: research
Membrane association but not identity is required for LRRK2 activation and phosphorylation of Rab GTPases
LRRK2 kinase mutations cause familial Parkinson’s disease and increased phosphorylation of a subset of Rab GTPases. Rab29 recruits LRRK2 to the trans-Golgi and activates it there, yet some of LRRK2’s major Rab substrates are not on the Golgi. We sought to characterize the cell biology of LRRK2 activation. Unlike other Rab family members, we show that Rab29 binds nucleotide weakly, is poorly prenylated, and is not bound to GDI in the cytosol; nevertheless, Rab29 only activates LRRK2 when it is membrane bound and GTP bound. Mitochondrially anchored, GTP-bound Rab29 is both a LRRK2 substrate and activator, and it ...
Source: Journal of Cell Biology - December 1, 2019 Category: Cytology Authors: Gomez, R. C., Wawro, P., Lis, P., Alessi, D. R., Pfeffer, S. R. Tags: Disease, Trafficking Articles Source Type: research
Disease-associated mutations in Niemann-Pick type C1 alter ER calcium signaling and neuronal plasticity
Niemann-Pick type C1 (NPC1) protein is essential for the transport of externally derived cholesterol from lysosomes to other organelles. Deficiency of NPC1 underlies the progressive NPC1 neurodegenerative disorder. Currently, there are no curative therapies for this fatal disease. Given the Ca2+ hypothesis of neurodegeneration, which posits that altered Ca2+ dynamics contribute to neuropathology, we tested if disease mutations in NPC1 alter Ca2+ signaling and neuronal plasticity. We determine that NPC1 inhibition or disease mutations potentiate store-operated Ca2+ entry (SOCE) due to a presenilin 1 (PSEN1)–dependent ...
Source: Journal of Cell Biology - December 1, 2019 Category: Cytology Authors: Tiscione, S. A., Vivas, O., Ginsburg, K. S., Bers, D. M., Ory, D. S., Santana, L. F., Dixon, R. E., Dickson, E. J. Tags: Disease, Organelles, Cell Signaling, Neuroscience Articles Source Type: research
Stress granules regulate stress-induced paraspeckle assembly
Eukaryotic cells contain a variety of RNA-protein macrocomplexes termed RNP granules. Different types of granules share multiple protein components; however, the crosstalk between spatially separated granules remains unaddressed. Paraspeckles and stress granules (SGs) are prototypical RNP granules localized exclusively in the nucleus and cytoplasm, respectively. Both granules are implicated in human diseases, such as amyotrophic lateral sclerosis. We characterized the composition of affinity-purified paraspeckle-like structures and found a significant overlap between the proteomes of paraspeckles and SGs. We further show t...
Source: Journal of Cell Biology - December 1, 2019 Category: Cytology Authors: An, H., Tan, J. T., Shelkovnikova, T. A. Tags: Disease, Cell Signaling, RNA Biology, Biochemistry Articles Source Type: research
Cell polarity-dependent centrosome separation in the C. elegans embryo
In animal cells, faithful chromosome segregation depends on the assembly of a bipolar spindle driven by the timely separation of the two centrosomes. Here we took advantage of the highly stereotypical cell divisions in Caenorhabditis elegans embryos to identify new regulators of centrosome separation. We find that at the two-cell stage, the somatic AB cell initiates centrosome separation later than the germline P1 cell. This difference is strongly exacerbated by the depletion of the kinesin-13 KLP-7/MCAK, resulting in incomplete centrosome separation at NEBD in AB but not P1. Our genetic and cell biology data indicate that...
Source: Journal of Cell Biology - December 1, 2019 Category: Cytology Authors: Bondaz, A., Cirillo, L., Meraldi, P., Gotta, M. Tags: Cell Cycle and Division, Polarity, Development, Genetics Articles Source Type: research
Confinement hinders motility by inducing RhoA-mediated nuclear influx, volume expansion, and blebbing
Cells migrate in vivo through complex confining microenvironments, which induce significant nuclear deformation that may lead to nuclear blebbing and nuclear envelope rupture. While actomyosin contractility has been implicated in regulating nuclear envelope integrity, the exact mechanism remains unknown. Here, we argue that confinement-induced activation of RhoA/myosin-II contractility, coupled with LINC complex-dependent nuclear anchoring at the cell posterior, locally increases cytoplasmic pressure and promotes passive influx of cytoplasmic constituents into the nucleus without altering nuclear efflux. Elevated nuclear i...
Source: Journal of Cell Biology - December 1, 2019 Category: Cytology Authors: Mistriotis, P., Wisniewski, E. O., Bera, K., Keys, J., Li, Y., Tuntithavornwat, S., Law, R. A., Perez-Gonzalez, N. A., Erdogmus, E., Zhang, Y., Zhao, R., Sun, S. X., Kalab, P., Lammerding, J., Konstantopoulos, K. Tags: Organelles, Migration, Motility, Biophysics, Cancer Articles Source Type: research
Vimentin protects cells against nuclear rupture and DNA damage during migration
Mammalian cells frequently migrate through tight spaces during normal embryogenesis, wound healing, diapedesis, or in pathological situations such as metastasis. Nuclear size and shape are important factors in regulating the mechanical properties of cells during their migration through such tight spaces. At the onset of migratory behavior, cells often initiate the expression of vimentin, an intermediate filament protein that polymerizes into networks extending from a juxtanuclear cage to the cell periphery. However, the role of vimentin intermediate filaments (VIFs) in regulating nuclear shape and mechanics remains unknown...
Source: Journal of Cell Biology - December 1, 2019 Category: Cytology Authors: Patteson, A. E., Vahabikashi, A., Pogoda, K., Adam, S. A., Mandal, K., Kittisopikul, M., Sivagurunathan, S., Goldman, A., Goldman, R. D., Janmey, P. A. Tags: Cytoskeleton, Migration, Motility, Cancer, Development Articles Source Type: research
Nucleoplasmin is a limiting component in the scaling of nuclear size with cytoplasmic volume
How nuclear size is regulated relative to cell size is a fundamental cell biological question. Reductions in both cell and nuclear sizes during Xenopus laevis embryogenesis provide a robust scaling system to study mechanisms of nuclear size regulation. To test if the volume of embryonic cytoplasm is limiting for nuclear growth, we encapsulated gastrula-stage embryonic cytoplasm and nuclei in droplets of defined volume using microfluidics. Nuclei grew and reached new steady-state sizes as a function of cytoplasmic volume, supporting a limiting component mechanism of nuclear size control. Through biochemical fractionation, w...
Source: Journal of Cell Biology - December 1, 2019 Category: Cytology Authors: Chen, P., Tomschik, M., Nelson, K. M., Oakey, J., Gatlin, J. C., Levy, D. L. Tags: Organelles, Chromatin or Epigenetics, Development Articles Source Type: research
CDK1-mediated CENP-C phosphorylation modulates CENP-A binding and mitotic kinetochore localization
The kinetochore is essential for faithful chromosome segregation during mitosis. To form a functional kinetochore, constitutive centromere-associated network (CCAN) proteins are assembled on the centromere chromatin that contains the centromere-specific histone CENP-A. CENP-C, a CCAN protein, directly interacts with the CENP-A nucleosome to nucleate the kinetochore structure. As CENP-C is a hub protein for kinetochore assembly, it is critical to address how the CENP-A–CENP-C interaction is regulated during cell cycle progression. To address this question, we investigated the CENP-C C-terminal region, including a cons...
Source: Journal of Cell Biology - December 1, 2019 Category: Cytology Authors: Watanabe, R., Hara, M., Okumura, E.-i., Herve, S., Fachinetti, D., Ariyoshi, M., Fukagawa, T. Tags: Cell Cycle and Division, Biochemistry Articles Source Type: research
Rab7 regulates primary cilia disassembly through cilia excision
In this study, we identify the small GTPase Rab7 as a novel regulator of cilia disassembly. Depletion of Rab7 potently induced spontaneous ciliogenesis in proliferating cells and promoted cilia elongation during quiescence. Moreover, Rab7 performs an essential role in cilia disassembly; knockdown of Rab7 blocked serum-induced ciliary resorption, and active Rab7 was required for this process. Further, we demonstrate that Rab7 depletion significantly suppresses cilia tip excision, referred to as cilia ectocytosis, which has been identified as required for cilia disassembly. Mechanically, the failure of F-actin polymerization...
Source: Journal of Cell Biology - December 1, 2019 Category: Cytology Authors: Wang, G., Hu, H.-B., Chang, Y., Huang, Y., Song, Z.-Q., Zhou, S.-B., Chen, L., Zhang, Y.-C., Wu, M., Tu, H.-Q., Yuan, J.-F., Wang, N., Pan, X., Li, A.-L., Zhou, T., Zhang, X.-M., He, K., Li, H.-Y. Tags: Cilia Reports Source Type: research
SIK3 suppresses neuronal hyperexcitability by regulating the glial capacity to buffer K+ and water
Glial regulation of extracellular potassium (K+) helps to maintain appropriate levels of neuronal excitability. While channels and transporters mediating K+ and water transport are known, little is understood about upstream regulatory mechanisms controlling the glial capacity to buffer K+ and osmotically obliged water. Here we identify salt-inducible kinase 3 (SIK3) as the central node in a signal transduction pathway controlling glial K+ and water homeostasis in Drosophila. Loss of SIK3 leads to dramatic extracellular fluid accumulation in nerves, neuronal hyperexcitability, and seizures. SIK3-dependent phenotypes are exa...
Source: Journal of Cell Biology - December 1, 2019 Category: Cytology Authors: Li, H., Russo, A., DiAntonio, A. Tags: Cell Signaling, Neuroscience Reports Source Type: research
Mitochondrial stress causes neuronal dysfunction via an ATF4-dependent increase in L-2-hydroxyglutarate
Mitochondrial stress contributes to a range of neurological diseases. Mitonuclear signaling pathways triggered by mitochondrial stress remodel cellular physiology and metabolism. How these signaling mechanisms contribute to neuronal dysfunction and disease is poorly understood. We find that mitochondrial stress in neurons activates the transcription factor ATF4 as part of the endoplasmic reticulum unfolded protein response (UPR) in Drosophila. We show that ATF4 activation reprograms nuclear gene expression and contributes to neuronal dysfunction. Mitochondrial stress causes an ATF4-dependent increase in the level of the me...
Source: Journal of Cell Biology - December 1, 2019 Category: Cytology Authors: Hunt, R. J., Granat, L., McElroy, G. S., Ranganathan, R., Chandel, N. S., Bateman, J. M. Tags: Organelles, Cell Signaling, Metabolism, Neuroscience Reports Source Type: research
