Gulp1 controls Eph/ephrin trogocytosis and is important for cell rearrangements during development
Trogocytosis, in which cells nibble away parts of neighboring cells, is an intercellular cannibalism process conserved from protozoa to mammals. Its underlying molecular mechanisms are not well understood and are likely distinct from phagocytosis, a process that clears entire cells. Bi-directional contact repulsion induced by Eph/ephrin signaling involves transfer of membrane patches and full-length Eph/ephrin protein complexes between opposing cells, resembling trogocytosis. Here, we show that the phagocytic adaptor protein Gulp1 regulates EphB/ephrinB trogocytosis to achieve efficient cell rearrangements of cultured cell...
Source: Journal of Cell Biology - October 6, 2019 Category: Cytology Authors: Gong, J., Gaitanos, T. N., Luu, O., Huang, Y., Gaitanos, L., Lindner, J., Winklbauer, R., Klein, R. Tags: Cell Signaling, Trafficking, Biochemistry, Development Articles Source Type: research
A kindlin-3-leupaxin-paxillin signaling pathway regulates podosome stability
In conclusion, our findings show that kindlin-3 not only activates and clusters integrins into podosomes but also regulates their lifetime by recruiting leupaxin, which controls PTP-PEST activity and thereby paxillin phosphorylation and downstream signaling. (Source: Journal of Cell Biology)
Source: Journal of Cell Biology - October 6, 2019 Category: Cytology Authors: Klapproth, S., Bromberger, T., Türk, C., Krüger, M., Moser, M. Tags: Adhesion, Cell Signaling, Biochemistry Articles Source Type: research
The role of APC-mediated actin assembly in microtubule capture and focal adhesion turnover
Focal adhesion (FA) turnover depends on microtubules and actin. Microtubule ends are captured at FAs, where they induce rapid FA disassembly. However, actin’s roles are less clear. Here, we use polarization-resolved microscopy, FRAP, live cell imaging, and a mutant of Adenomatous polyposis coli (APC-m4) defective in actin nucleation to investigate the role of actin assembly in FA turnover. We show that APC-mediated actin assembly is critical for maintaining normal F-actin levels, organization, and dynamics at FAs, along with organization of FA components. In WT cells, microtubules are captured repeatedly at FAs as th...
Source: Journal of Cell Biology - October 6, 2019 Category: Cytology Authors: Juanes, M. A., Isnardon, D., Badache, A., Brasselet, S., Mavrakis, M., Goode, B. L. Tags: Cytoskeleton, Genetics Articles Source Type: research
Apical polarity proteins recruit the RhoGEF Cysts to promote junctional myosin assembly
The spatio-temporal regulation of small Rho GTPases is crucial for the dynamic stability of epithelial tissues. However, how RhoGTPase activity is controlled during development remains largely unknown. To explore the regulation of Rho GTPases in vivo, we analyzed the Rho GTPase guanine nucleotide exchange factor (RhoGEF) Cysts, the Drosophila orthologue of mammalian p114RhoGEF, GEF-H1, p190RhoGEF, and AKAP-13. Loss of Cysts causes a phenotype that closely resembles the mutant phenotype of the apical polarity regulator Crumbs. This phenotype can be suppressed by the loss of basolateral polarity proteins, suggesting that Cys...
Source: Journal of Cell Biology - October 6, 2019 Category: Cytology Authors: Silver, J. T., Wirtz-Peitz, F., Simoes, S., Pellikka, M., Yan, D., Binari, R., Nishimura, T., Li, Y., Harris, T. J. C., Perrimon, N., Tepass, U. Tags: Cytoskeleton, Development Articles Source Type: research
Claudins and JAM-A coordinately regulate tight junction formation and epithelial polarity
Tight junctions (TJs) establish the epithelial barrier and are thought to form a membrane fence to regulate epithelial polarity, although the roles of TJs in epithelial polarity remain controversial. Claudins constitute TJ strands in conjunction with the cytoplasmic scaffolds ZO-1 and ZO-2 and play pivotal roles in epithelial barrier formation. However, how claudins and other TJ membrane proteins cooperate to organize TJs remains unclear. Here, we systematically knocked out TJ components by genome editing and show that while ZO-1/ZO-2–deficient cells lacked TJ structures and epithelial barriers, claudin-deficient cel...
Source: Journal of Cell Biology - October 6, 2019 Category: Cytology Authors: Otani, T., Nguyen, T. P., Tokuda, S., Sugihara, K., Sugawara, T., Furuse, K., Miura, T., Ebnet, K., Furuse, M. Tags: Adhesion, Physiology Articles Source Type: research
MT1-MMP recruits the ER-Golgi SNARE Bet1 for efficient MT1-MMP transport to the plasma membrane
Metastasis is a major cause of cancer-related death. Membrane type 1–matrix metalloproteinase (MT1-MMP) is a critical protease for local invasion and metastasis. MT1-MMP is synthesized in the endoplasmic reticulum (ER) and transported in vesicles to invadopodia, specialized subdomains of the plasma membrane, through secretory and endocytic recycling pathways. The molecular mechanism underlying intracellular transport of MT1-MMP has been extensively studied, but is not fully understood. We show that MT1-MMP diverts the SNARE Bet1 from its function in ER-Golgi transport, to promote MT1-MMP trafficking to the cell surfa...
Source: Journal of Cell Biology - October 6, 2019 Category: Cytology Authors: Miyagawa, T., Hasegawa, K., Aoki, Y., Watanabe, T., Otagiri, Y., Arasaki, K., Wakana, Y., Asano, K., Tanaka, M., Yamaguchi, H., Tagaya, M., Inoue, H. Tags: Organelles, Membrane and Lipid Biology, Cancer Articles Source Type: research
VPS37A directs ESCRT recruitment for phagophore closure
The process of phagophore closure requires the endosomal sorting complex required for transport III (ESCRT-III) subunit CHMP2A and the AAA ATPase VPS4, but their regulatory mechanisms remain unknown. Here, we establish a FACS-based HaloTag-LC3 autophagosome completion assay to screen a genome-wide CRISPR library and identify the ESCRT-I subunit VPS37A as a critical component for phagophore closure. VPS37A localizes on the phagophore through the N-terminal putative ubiquitin E2 variant domain, which is found to be required for autophagosome completion but dispensable for ESCRT-I complex formation and the degradation of epid...
Source: Journal of Cell Biology - October 6, 2019 Category: Cytology Authors: Takahashi, Y., Liang, X., Hattori, T., Tang, Z., He, H., Chen, H., Liu, X., Abraham, T., Imamura-Kawasawa, Y., Buchkovich, N. J., Young, M. M., Wang, H.-G. Tags: Cell Death and Autophagy, Biochemistry Articles Source Type: research
Lipid droplet size directs lipolysis and lipophagy catabolism in hepatocytes
Lipid droplet (LD) catabolism in hepatocytes is mediated by a combination of lipolysis and a selective autophagic mechanism called lipophagy, but the relative contributions of these seemingly distinct pathways remain unclear. We find that inhibition of lipolysis, lipophagy, or both resulted in similar overall LD content but dramatic differences in LD morphology. Inhibition of the lipolysis enzyme adipose triglyceride lipase (ATGL) resulted in large cytoplasmic LDs, whereas lysosomal inhibition caused the accumulation of numerous small LDs within the cytoplasm and degradative acidic vesicles. Combined inhibition of ATGL and...
Source: Journal of Cell Biology - October 6, 2019 Category: Cytology Authors: Schott, M. B., Weller, S. G., Schulze, R. J., Krueger, E. W., Drizyte-Miller, K., Casey, C. A., McNiven, M. A. Tags: Cell Metabolism, Trafficking, Biochemistry, Metabolism Articles Source Type: research
A molecular recognition feature mediates ribosome-induced SRP-receptor assembly during protein targeting
Molecular recognition features (MoRFs) provide interaction motifs in intrinsically disordered protein regions to mediate diverse cellular functions. Here we report that a MoRF element, located in the disordered linker domain of the mammalian signal recognition particle (SRP) receptor and conserved among eukaryotes, plays an essential role in sensing the ribosome during cotranslational protein targeting to the endoplasmic reticulum. Loss of the MoRF in the SRP receptor (SR) largely abolishes the ability of the ribosome to activate SRP-SR assembly and impairs cotranslational protein targeting. These results demonstrate a nov...
Source: Journal of Cell Biology - October 6, 2019 Category: Cytology Authors: Hwang Fu, Y.-H., Chandrasekar, S., Lee, J. H., Shan, S.-o. Tags: Protein Homeostasis, Biochemistry Articles Source Type: research
FIGNL1 associates with KIF1B{beta} and BICD1 to restrict dynein transport velocity during axon navigation
Neuronal connectivity relies on molecular motor-based axonal transport of diverse cargoes. Yet the precise players and regulatory mechanisms orchestrating such trafficking events remain largely unknown. We here report the ATPase Fignl1 as a novel regulator of bidirectional transport during axon navigation. Using a yeast two-hybrid screen and coimmunoprecipitation assays, we showed that Fignl1 binds the kinesin Kif1bβ and the dynein/dynactin adaptor Bicaudal D-1 (Bicd1) in a molecular complex including the dynactin subunit dynactin 1. Fignl1 colocalized with Kif1bβ and showed bidirectional mobility in zebrafish ax...
Source: Journal of Cell Biology - October 6, 2019 Category: Cytology Authors: Atkins, M., Gasmi, L., Bercier, V., Revenu, C., Del Bene, F., Hazan, J., Fassier, C. Tags: Cytoskeleton, Trafficking, Development, Neuroscience Articles Source Type: research
Cell and tissue morphology determine actin-dependent nuclear migration mechanisms in neuroepithelia
Correct nuclear position is crucial for cellular function and tissue development. Depending on cell context, however, the cytoskeletal elements responsible for nuclear positioning vary. While these cytoskeletal mechanisms have been intensely studied in single cells, how nuclear positioning is linked to tissue morphology is less clear. Here, we compare apical nuclear positioning in zebrafish neuroepithelia. We find that kinetics and actin-dependent mechanisms of nuclear positioning vary in tissues of different morphology. In straight neuroepithelia, nuclear positioning is controlled by Rho-ROCK–dependent myosin contra...
Source: Journal of Cell Biology - October 6, 2019 Category: Cytology Authors: Yanakieva, I., Erzberger, A., Matejcic, M., Modes, C. D., Norden, C. Tags: Cytoskeleton, Organelles, Development Articles Source Type: research
Coronin 1A depletion restores the nuclear stability and viability of Aip1/Wdr1-deficient neutrophils
Actin dynamics is central for cells, and especially for the fast-moving leukocytes. The severing of actin filaments is mainly achieved by cofilin, assisted by Aip1/Wdr1 and coronins. We found that in Wdr1-deficient zebrafish embryos, neutrophils display F-actin cytoplasmic aggregates and a complete spatial uncoupling of phospho-myosin from F-actin. They then undergo an unprecedented gradual disorganization of their nucleus followed by eruptive cell death. Their cofilin is mostly unphosphorylated and associated with F-actin, thus likely outcompeting myosin for F-actin binding. Myosin inhibition reproduces in WT embryos the ...
Source: Journal of Cell Biology - October 6, 2019 Category: Cytology Authors: Bowes, C., Redd, M., Yousfi, M., Tauzin, M., Murayama, E., Herbomel, P. Tags: Disease, Cytoskeleton, Development Articles Source Type: research
Enrichment of Aurora B kinase at the inner kinetochore controls outer kinetochore assembly
Outer kinetochore assembly enables chromosome attachment to microtubules and spindle assembly checkpoint (SAC) signaling in mitosis. Aurora B kinase controls kinetochore assembly by phosphorylating the Mis12 complex (Mis12C) subunit Dsn1. Current models propose Dsn1 phosphorylation relieves autoinhibition, allowing Mis12C binding to inner kinetochore component CENP-C. Using Xenopus laevis egg extracts and biochemical reconstitution, we found that autoinhibition of the Mis12C by Dsn1 impedes its phosphorylation by Aurora B. Our data indicate that the INCENP central region increases Dsn1 phosphorylation by enriching Aurora B...
Source: Journal of Cell Biology - October 6, 2019 Category: Cytology Authors: Bonner, M. K., Haase, J., Swinderman, J., Halas, H., Miller Jenkins, L. M., Kelly, A. E. Tags: Cytoskeleton, Cell Cycle and Division, Biochemistry Articles Source Type: research
Aurora B kinase activity is regulated by SET/TAF1 on Sgo2 at the inner centromere
The accurate regulation of phosphorylation at the kinetochore is essential for establishing chromosome bi-orientation. Phosphorylation of kinetochore proteins by the Aurora B kinase destabilizes improper kinetochore–microtubule attachments, whereas the phosphatase PP2A has a counteracting role. Imbalanced phosphoregulation leads to error-prone chromosome segregation and aneuploidy, a hallmark of cancer cells. However, little is known about the molecular events that control the balance of phosphorylation at the kinetochore. Here, we show that localization of SET/TAF1, an oncogene product, to centromeres maintains Auro...
Source: Journal of Cell Biology - October 6, 2019 Category: Cytology Authors: Asai, Y., Fukuchi, K., Tanno, Y., Koitabashi-Kiyozuka, S., Kiyozuka, T., Noda, Y., Matsumura, R., Koizumi, T., Watanabe, A., Nagata, K., Watanabe, Y., Terada, Y. Tags: Cell Cycle and Division, Cancer Articles Source Type: research
Hair follicle regeneration suppresses Ras-driven oncogenic growth
Mutations associated with tumor development in certain tissues can be nontumorigenic in others, yet the mechanisms underlying these different outcomes remains poorly understood. To address this, we targeted an activating Hras mutation to hair follicle stem cells and discovered that Hras mutant cells outcompete wild-type neighbors yet are integrated into clinically normal skin hair follicles. In contrast, targeting the Hras mutation to the upper noncycling region of the skin epithelium leads to benign outgrowths. Follicular Hras mutant cells autonomously and nonautonomously enhance regeneration, which directs mutant cells i...
Source: Journal of Cell Biology - October 6, 2019 Category: Cytology Authors: Pineda, C. M., Gonzalez, D. G., Matte-Martone, C., Boucher, J., Lathrop, E., Gallini, S., Fons, N. R., Xin, T., Tai, K., Marsh, E., Nguyen, D. X., Suozzi, K. C., Beronja, S., Greco, V. Tags: Stem Cells, Cell Signaling, Cancer Reports Source Type: research
