RalGTPases contribute to Schwann cell repair after nerve injury via regulation of process formation
RalA and RalB are small GTPases that are involved in cell migration and membrane dynamics. We used transgenic mice in which one or both GTPases were genetically ablated to investigate the role of RalGTPases in the Schwann cell (SC) response to nerve injury and repair. RalGTPases were dispensable for SC function in the naive uninjured state. Ablation of both RalA and RalB (but not individually) in SCs resulted in impaired axon remyelination and target reinnervation following nerve injury, which resulted in slowed recovery of motor function. Ral GTPases were localized to the leading lamellipodia in SCs and were required for ...
Source: Journal of Cell Biology - June 30, 2019 Category: Cytology Authors: Galino, J., Cervellini, I., Zhu, N., Stöberl, N., Hütte, M., Fricker, F. R., Lee, G., McDermott, L., Lalli, G., Bennett, D. L. H. Tags: Migration, Motility, Polarity, Neuroscience Articles Source Type: research
Ral GTPases in Schwann cells promote radial axonal sorting in the peripheral nervous system
Small GTPases of the Rho and Ras families are important regulators of Schwann cell biology. The Ras-like GTPases RalA and RalB act downstream of Ras in malignant peripheral nerve sheath tumors. However, the physiological role of Ral proteins in Schwann cell development is unknown. Using transgenic mice with ablation of one or both Ral genes, we report that Ral GTPases are crucial for axonal radial sorting. While lack of only one Ral GTPase was dispensable for early peripheral nerve development, ablation of both RalA and RalB resulted in persistent radial sorting defects, associated with hallmarks of deficits in Schwann cel...
Source: Journal of Cell Biology - June 30, 2019 Category: Cytology Authors: Ommer, A., Figlia, G., Pereira, J. A., Datwyler, A. L., Gerber, J., DeGeer, J., Lalli, G., Suter, U. Tags: Cell Signaling, Development, Neuroscience Articles Source Type: research
Regulation of axon growth by myosin II-dependent mechanocatalysis of cofilin activity
We report that myosin II activity is regulated by PKC during 5-HT responses and that PKC activity is necessary for increases in traction force normally associated with these growth responses. 5-HT simultaneously induces cofilin-dependent decreases in actin network density and PKC-dependent increases in point contact density. These reciprocal effects facilitate increases in traction force production in domains exhibiting decreased actin network density. Interestingly, when PKC activity was up-regulated, 5-HT treatments resulted in myosin II hyperactivation accompanied by catastrophic cofilin-dependent decreases in actin fil...
Source: Journal of Cell Biology - June 30, 2019 Category: Cytology Authors: Zhang, X.-F., Ajeti, V., Tsai, N., Fereydooni, A., Burns, W., Murrell, M., De La Cruz, E. M., Forscher, P. Tags: Cytoskeleton, Migration, Motility, Biophysics, Neuroscience Articles Source Type: research
Patronin-mediated minus end growth is required for dendritic microtubule polarity
Microtubule minus ends are thought to be stable in cells. Surprisingly, in Drosophila and zebrafish neurons, we observed persistent minus end growth, with runs lasting over 10 min. In Drosophila, extended minus end growth depended on Patronin, and Patronin reduction disrupted dendritic minus-end-out polarity. In fly dendrites, microtubule nucleation sites localize at dendrite branch points. Therefore, we hypothesized minus end growth might be particularly important beyond branch points. Distal dendrites have mixed polarity, and reduction of Patronin lowered the number of minus-end-out microtubules. More strikingly, extra P...
Source: Journal of Cell Biology - June 30, 2019 Category: Cytology Authors: Feng, C., Thyagarajan, P., Shorey, M., Seebold, D. Y., Weiner, A. T., Albertson, R. M., Rao, K. S., Sagasti, A., Goetschius, D. J., Rolls, M. M. Tags: Polarity, Neuroscience Articles Source Type: research
A specific isoform of Pyd/ZO-1 mediates junctional remodeling and formation of slit diaphragms
The podocyte slit diaphragm (SD), responsible for blood filtration in vertebrates, is a major target of injury in chronic kidney disease. The damage includes severe morphological changes with destabilization of SDs and their replacement by junctional complexes between abnormally broadened foot processes. In Drosophila melanogaster, SDs are present in nephrocytes, which filter the fly's hemolymph. Here, we show that a specific isoform of Polychaetoid/ZO-1, Pyd-P, is essential for Drosophila SDs, since, in pyd mutants devoid of Pyd-P, SDs do not form and the SD component Dumbfounded accumulates at ectopic septate-like juncti...
Source: Journal of Cell Biology - June 30, 2019 Category: Cytology Authors: Carrasco-Rando, M., Prieto-Sanchez, S., Culi, J., Tutor, A. S., Ruiz-Gomez, M. Tags: Trafficking, Development Articles Source Type: research
Scribble, Erbin, and Lano redundantly regulate epithelial polarity and apical adhesion complex
The basolateral protein Scribble (Scrib), a member of the LAP protein family, is essential for epithelial apicobasal polarity (ABP) in Drosophila. However, a conserved function for this protein in mammals is unclear. Here we show that the crucial role for Scrib in ABP has remained obscure due to the compensatory function of two other LAP proteins, Erbin and Lano. A combined Scrib/Erbin/Lano knockout disorganizes the cell–cell junctions and the cytoskeleton. It also results in mislocalization of several apical (Par6, aPKC, and Pals1) and basolateral (Llgl1 and Llgl2) identity proteins. These defects can be rescued by ...
Source: Journal of Cell Biology - June 30, 2019 Category: Cytology Authors: Choi, J., Troyanovsky, R. B., Indra, I., Mitchell, B. J., Troyanovsky, S. M. Tags: Polarity, Development Articles Source Type: research
TORC2 controls endocytosis through plasma membrane tension
Target of rapamycin complex 2 (TORC2) is a conserved protein kinase that regulates multiple plasma membrane (PM)–related processes, including endocytosis. Direct, chemical inhibition of TORC2 arrests endocytosis but with kinetics that is relatively slow and therefore inconsistent with signaling being mediated solely through simple phosphorylation cascades. Here, we show that in addition to and independently from regulation of the phosphorylation of endocytic proteins, TORC2 also controls endocytosis by modulating PM tension. Elevated PM tension, upon TORC2 inhibition, impinges on endocytosis at two different levels b...
Source: Journal of Cell Biology - June 30, 2019 Category: Cytology Authors: Riggi, M., Bourgoint, C., Macchione, M., Matile, S., Loewith, R., Roux, A. Tags: Membrane and Lipid Biology, Biophysics Articles Source Type: research
The exocyst controls lysosome secretion and antigen extraction at the immune synapse of B cells
B lymphocytes capture antigens from the surface of presenting cells by forming an immune synapse. Local secretion of lysosomes, which are guided to the synaptic membrane by centrosome repositioning, can facilitate the extraction of immobilized antigens. However, the molecular basis underlying their delivery to precise domains of the plasma membrane remains elusive. Here we show that microtubule stabilization, triggered by engagement of the B cell receptor, acts as a cue to release centrosome-associated Exo70, which is redistributed to the immune synapse. This process is coupled to the recruitment and activation of GEF-H1, ...
Source: Journal of Cell Biology - June 30, 2019 Category: Cytology Authors: Saez, J. J., Diaz, J., Ibanez, J., Bozo, J. P., Cabrera Reyes, F., Alamo, M., Gobert, F.-X., Obino, D., Bono, M. R., Lennon-Dumenil, A.-M., Yeaman, C., Yuseff, M.-I. Tags: Polarity Articles Source Type: research
Rab46 integrates Ca2+ and histamine signaling to regulate selective cargo release from Weibel-Palade bodies
Endothelial cells selectively release cargo stored in Weibel-Palade bodies (WPBs) to regulate vascular function, but the underlying mechanisms are poorly understood. Here we show that histamine evokes the release of the proinflammatory ligand, P-selectin, while diverting WPBs carrying non-inflammatory cargo away from the plasma membrane to the microtubule organizing center. This differential trafficking is dependent on Rab46 (CRACR2A), a newly identified Ca2+-sensing GTPase, which localizes to a subset of P-selectin–negative WPBs. After acute stimulation of the H1 receptor, GTP-bound Rab46 evokes dynein-dependent ret...
Source: Journal of Cell Biology - June 30, 2019 Category: Cytology Authors: Miteva, K. T., Pedicini, L., Wilson, L. A., Jayasinghe, I., Slip, R. G., Marszalek, K., Gaunt, H. J., Bartoli, F., Deivasigamani, S., Sobradillo, D., Beech, D. J., McKeown, L. Tags: Cell Signaling, Trafficking, Physiology Articles Source Type: research
RAB6 and microtubules restrict protein secretion to focal adhesions
To ensure their homeostasis and sustain differentiated functions, cells continuously transport diverse cargos to various cell compartments and in particular to the cell surface. Secreted proteins are transported along intracellular routes from the endoplasmic reticulum through the Golgi complex before reaching the plasma membrane along microtubule tracks. Using a synchronized secretion assay, we report here that exocytosis does not occur randomly at the cell surface but on localized hotspots juxtaposed to focal adhesions. Although microtubules are involved, the RAB6-dependent machinery plays an essential role. We observed ...
Source: Journal of Cell Biology - June 30, 2019 Category: Cytology Authors: Fourriere, L., Kasri, A., Gareil, N., Bardin, S., Bousquet, H., Pereira, D., Perez, F., Goud, B., Boncompain, G., Miserey-Lenkei, S. Tags: Trafficking, Technology Articles Source Type: research
PTEN reduces endosomal PtdIns(4,5)P2 in a phosphatase-independent manner via a PLC pathway
The tumor suppressor PTEN dephosphorylates PtdIns(3,4,5)P3 into PtdIns(4,5)P2. Here, we make the unexpected discovery that in Drosophila melanogaster PTEN reduces PtdIns(4,5)P2 levels on endosomes, independently of its phosphatase activity. This new PTEN function requires the enzymatic action of dPLCXD, an atypical phospholipase C. Importantly, we discovered that this novel PTEN/dPLCXD pathway can compensate for depletion of dOCRL, a PtdIns(4,5)P2 phosphatase. Mutation of OCRL1, the human orthologue of dOCRL, causes oculocerebrorenal Lowe syndrome, a rare multisystemic genetic disease. Both OCRL1 and dOCRL loss have been s...
Source: Journal of Cell Biology - June 30, 2019 Category: Cytology Authors: Mondin, V. E., Ben El Kadhi, K., Cauvin, C., Jackson-Crawford, A., Belanger, E., Decelle, B., Salomon, R., Lowe, M., Echard, A., Carreno, S. Tags: Disease, Cell Signaling, Membrane and Lipid Biology Articles Source Type: research
SFI1 promotes centriole duplication by recruiting USP9X to stabilize the microcephaly protein STIL
In mammals, centrioles participate in brain development, and human mutations affecting centriole duplication cause microcephaly. Here, we identify a role for the mammalian homologue of yeast SFI1, involved in the duplication of the yeast spindle pole body, as a critical regulator of centriole duplication in mammalian cells. Mammalian SFI1 interacts with USP9X, a deubiquitylase associated with human syndromic mental retardation. SFI1 localizes USP9X to the centrosome during S phase to deubiquitylate STIL, a critical regulator of centriole duplication. USP9X-mediated deubiquitylation protects STIL from degradation. Consisten...
Source: Journal of Cell Biology - June 30, 2019 Category: Cytology Authors: Kodani, A., Moyer, T., Chen, A., Holland, A., Walsh, C. A., Reiter, J. F. Tags: Disease, Cytoskeleton, Cell Cycle and Division, Neuroscience Articles Source Type: research
Intrinsic checkpoint deficiency during cell cycle re-entry from quiescence
To maintain tissue homeostasis, cells transition between cell cycle quiescence and proliferation. An essential G1 process is minichromosome maintenance complex (MCM) loading at DNA replication origins to prepare for S phase, known as origin licensing. A p53-dependent origin licensing checkpoint normally ensures sufficient MCM loading before S phase entry. We used quantitative flow cytometry and live cell imaging to compare MCM loading during the long first G1 upon cell cycle entry and the shorter G1 phases in the second and subsequent cycles. We discovered that despite the longer G1 phase, the first G1 after cell cycle re-...
Source: Journal of Cell Biology - June 30, 2019 Category: Cytology Authors: Matson, J. P., House, A. M., Grant, G. D., Wu, H., Perez, J., Cook, J. G. Tags: Cell Cycle and Division, DNA Biology Articles Source Type: research
Augmin accumulation on long-lived microtubules drives amplification and kinetochore-directed growth
Dividing cells reorganize their microtubule cytoskeleton into a bipolar spindle, which moves one set of sister chromatids to each nascent daughter cell. Early spindle assembly models postulated that spindle pole–derived microtubules search the cytoplasmic space until they randomly encounter a kinetochore to form a stable attachment. More recent work uncovered several additional, centrosome-independent microtubule generation pathways, but the contributions of each pathway to spindle assembly have remained unclear. Here, we combined live microscopy and mathematical modeling to show that most microtubules nucleate at no...
Source: Journal of Cell Biology - June 30, 2019 Category: Cytology Authors: David, A. F., Roudot, P., Legant, W. R., Betzig, E., Danuser, G., Gerlich, D. W. Tags: Cytoskeleton, Cell Cycle and Division Articles Source Type: research
Repair of nuclear ruptures requires barrier-to-autointegration factor
Cell nuclei rupture following exposure to mechanical force and/or upon weakening of nuclear integrity, but nuclear ruptures are repairable. Barrier-to-autointegration factor (BAF), a small DNA-binding protein, rapidly localizes to nuclear ruptures; however, its role at these rupture sites is unknown. Here, we show that it is predominantly a nonphosphorylated cytoplasmic population of BAF that binds nuclear DNA to rapidly and transiently localize to the sites of nuclear rupture, resulting in BAF accumulation in the nucleus. BAF subsequently recruits transmembrane LEM-domain proteins, causing their accumulation at rupture si...
Source: Journal of Cell Biology - June 30, 2019 Category: Cytology Authors: Halfmann, C. T., Sears, R. M., Katiyar, A., Busselman, B. W., Aman, L. K., Zhang, Q., OBryan, C. S., Angelini, T. E., Lele, T. P., Roux, K. J. Tags: Organelles, Development Reports Source Type: research
