Dynamic instability of clathrin assembly provides proofreading control for endocytosis
Clathrin-mediated endocytosis depends on the formation of functional clathrin-coated pits that recruit cargos and mediate the uptake of those cargos into the cell. However, it remains unclear whether the cargos in the growing clathrin-coated pits are actively monitored by the coat assembly machinery. Using a cell-free reconstitution system, we report that clathrin coat formation and cargo sorting can be uncoupled, indicating that a checkpoint is required for functional cargo incorporation. We demonstrate that the ATPase Hsc70 and a dynamic exchange of clathrin during assembly are required for this checkpoint. In the absenc...
Source: Journal of Cell Biology - October 6, 2019 Category: Cytology Authors: Chen, Y., Yong, J., Martinez-Sanchez, A., Yang, Y., Wu, Y., De Camilli, P., Fernandez-Busnadiego, R., Wu, M. Tags: Membrane and Lipid Biology, Trafficking, Biochemistry, Biophysics Reports Source Type: research
Checkpoint signaling and error correction require regulation of the MPS1 T-loop by PP2A-B56
During mitosis, the formation of microtubule–kinetochore attachments is monitored by the serine/threonine kinase monopolar spindle 1 (MPS1). MPS1 is recruited to unattached kinetochores where it phosphorylates KNL1, BUB1, and MAD1 to initiate the spindle assembly checkpoint. This arrests the cell cycle until all kinetochores have been stably captured by microtubules. MPS1 also contributes to the error correction process rectifying incorrect kinetochore attachments. MPS1 activity at kinetochores requires autophosphorylation at multiple sites including threonine 676 in the activation segment or "T-loop." We now demonst...
Source: Journal of Cell Biology - October 6, 2019 Category: Cytology Authors: Hayward, D., Bancroft, J., Mangat, D., Alfonso-Perez, T., Dugdale, S., McCarthy, J., Barr, F. A., Gruneberg, U. Tags: Cell Cycle and Division Reports Source Type: research
Protein quality control in the secretory pathway
Protein folding is inherently error prone, especially in the endoplasmic reticulum (ER). Even with an elaborate network of molecular chaperones and protein folding facilitators, misfolding can occur quite frequently. To maintain protein homeostasis, eukaryotes have evolved a series of protein quality-control checkpoints. When secretory pathway quality-control pathways fail, stress response pathways, such as the unfolded protein response (UPR), are induced. In addition, the ER, which is the initial hub of protein biogenesis in the secretory pathway, triages misfolded proteins by delivering substrates to the proteasome or to...
Source: Journal of Cell Biology - October 6, 2019 Category: Cytology Authors: Sun, Z., Brodsky, J. L. Tags: Review Source Type: research
Eph receptors and ephrins engage in cellular cannibalism
Eph receptors bind ephrins on neighboring cells, oligomerizing into adhesive complexes that recruit signaling molecules. Execution of their signature repulsive program then generates pulling forces, enabling a cell to engulf a piece of another cell. New mechanistic insights by Gong et al. (2019. J. Cell Biol. https://doi.org/10.1083/jcb.201901032) define this process as a form of "cellular cannibalism." (Source: Journal of Cell Biology)
Source: Journal of Cell Biology - October 6, 2019 Category: Cytology Authors: Pasquale, E. B. Tags: Cell Signaling, Development, Neuroscience Spotlight Source Type: research
Kindlin-3 stokes the life span of podosomes
Macrophages and other cell types can form podosomes, highly dynamic adhesive structures that mediate the interaction of these cells with the surrounding matrix. In this issue, Klapproth et al. (2019. J. Cell Biol. https://doi.org/10.1083/jcb.201903109) find that kindlin-3 regulates podosome stability by recruiting leupaxin, with concomitant effects on PTP-PEST phosphatase activity and paxillin phosphorylation. (Source: Journal of Cell Biology)
Source: Journal of Cell Biology - October 6, 2019 Category: Cytology Authors: Zhang, H. Tags: Spotlight Source Type: research
Adult hair follicles keep oncogenic growth in check
Recent research shows that potentially cancerous, somatic mutations can reside in normal cells. Pineda et al. (2019. J. Cell Biol. https://doi.org/10.1083/jcb.201907178) report on a unique management technique by hair follicle stem cells to evade tumorigenesis. (Source: Journal of Cell Biology)
Source: Journal of Cell Biology - October 6, 2019 Category: Cytology Authors: Gay, D., Ito, M. Tags: Spotlight Source Type: research
Brajendra Tripathi: Keeping an eye out for translational research
Tripathi investigates how the tumor suppressor DLC1 is regulated by oncogenic kinases. (Source: Journal of Cell Biology)
Source: Journal of Cell Biology - October 6, 2019 Category: Cytology Authors: ODonnell, M. A. Tags: People & amp;amp; Ideas Source Type: research
Software for lattice light-sheet imaging of FRET biosensors, illustrated with a new Rap1 biosensor
We describe here a new software package, named ImageTank, that is specifically designed for practical imaging of biosensors using LLSM. To demonstrate its capabilities, we use a new biosensor to study the rapid 3D dynamics of the small GTPase Rap1 in vesicles and cell protrusions. (Source: Journal of Cell Biology)
Source: Journal of Cell Biology - September 1, 2019 Category: Cytology Authors: OShaughnessy, E. C., Stone, O. J., LaFosse, P. K., Azoitei, M. L., Tsygankov, D., Heddleston, J. M., Legant, W. R., Wittchen, E. S., Burridge, K., Elston, T. C., Betzig, E., Chew, T.-L., Adalsteinsson, D., Hahn, K. M. Tags: Cell Signaling, Technology Tools Source Type: research
Metalloprotease inhibitor TIMP proteins control FGF-2 bioavailability and regulate skeletal growth
Regulated growth plate activity is essential for postnatal bone development and body stature, yet the systems regulating epiphyseal fusion are poorly understood. Here, we show that the tissue inhibitors of metalloprotease (TIMP) gene family is essential for normal bone growth after birth. Whole-body quadruple-knockout mice lacking all four TIMPs have growth plate closure in long bones, precipitating limb shortening, epiphyseal distortion, and widespread chondrodysplasia. We identify TIMP/FGF-2/IHH as a novel nexus underlying bone lengthening where TIMPs negatively regulate the release of FGF-2 from chondrocytes to allow IH...
Source: Journal of Cell Biology - September 1, 2019 Category: Cytology Authors: Saw, S., Aiken, A., Fang, H., McKee, T. D., Bregant, S., Sanchez, O., Chen, Y., Weiss, A., Dickson, B. C., Czarny, B., Sinha, A., Fosang, A., Dive, V., Waterhouse, P. D., Kislinger, T., Khokha, R. Tags: Cell Signaling, Development Articles Source Type: research
Mechanical stress impairs pheromone signaling via Pkc1-mediated regulation of the MAPK scaffold Ste5
Cells continuously adapt cellular processes by integrating external and internal signals. In yeast, multiple stress signals regulate pheromone signaling to prevent mating under unfavorable conditions. However, the underlying crosstalk mechanisms remain poorly understood. Here, we show that mechanical stress activates Pkc1, which prevents lysis of pheromone-treated cells by inhibiting polarized growth. In vitro Pkc1 phosphorylates conserved residues within the RING-H2 domains of the scaffold proteins Far1 and Ste5, which are also phosphorylated in vivo. Interestingly, Pkc1 triggers dispersal of Ste5 from mating projections ...
Source: Journal of Cell Biology - September 1, 2019 Category: Cytology Authors: van Drogen, F., Mishra, R., Rudolf, F., Walczak, M. J., Lee, S. S., Reiter, W., Hegemann, B., Pelet, S., Dohnal, I., Binolfi, A., Yudina, Z., Selenko, P., Wider, G., Ammerer, G., Peter, M. Tags: Cell Signaling, Biochemistry Articles Source Type: research
{alpha}-Integrins dictate distinct modes of type IV collagen recruitment to basement membranes
Basement membranes (BMs) are cell-associated extracellular matrices that support tissue integrity, signaling, and barrier properties. Type IV collagen is critical for BM function, yet how it is directed into BMs in vivo is unclear. Through live-cell imaging of endogenous localization, conditional knockdown, and misexpression experiments, we uncovered distinct mechanisms of integrin-mediated collagen recruitment to Caenorhabditis elegans postembryonic gonadal and pharyngeal BMs. The putative laminin-binding αINA-1/βPAT-3 integrin was selectively activated in the gonad and recruited laminin, which directed moderat...
Source: Journal of Cell Biology - September 1, 2019 Category: Cytology Authors: Jayadev, R., Chi, Q., Keeley, D. P., Hastie, E. L., Kelley, L. C., Sherwood, D. R. Tags: Adhesion, Membrane and Lipid Biology, Development Articles Source Type: research
Spatiotemporal dynamics of GEF-H1 activation controlled by microtubule- and Src-mediated pathways
Rho family GTPases are activated with precise spatiotemporal control by guanine nucleotide exchange factors (GEFs). Guanine exchange factor H1 (GEF-H1), a RhoA activator, is thought to act as an integrator of microtubule (MT) and actin dynamics in diverse cell functions. Here we identify a GEF-H1 autoinhibitory sequence and exploit it to produce an activation biosensor to quantitatively probe the relationship between GEF-H1 conformational change, RhoA activity, and edge motion in migrating cells with micrometer- and second-scale resolution. Simultaneous imaging of MT dynamics and GEF-H1 activity revealed that autoinhibited...
Source: Journal of Cell Biology - September 1, 2019 Category: Cytology Authors: Azoitei, M. L., Noh, J., Marston, D. J., Roudot, P., Marshall, C. B., Daugird, T. A., Lisanza, S. L., Sandi, M.-J., Ikura, M., Sondek, J., Rottapel, R., Hahn, K. M., Danuser, G. Tags: Cytoskeleton, Migration, Motility, Systems and Computational Biology Articles Source Type: research
SRC and ERK cooperatively phosphorylate DLC1 and attenuate its Rho-GAP and tumor suppressor functions
SRC and ERK kinases control many cell biological processes that promote tumorigenesis by altering the activity of oncogenic and tumor suppressor proteins. We identify here a physiological interaction between DLC1, a focal adhesion protein and tumor suppressor, with SRC and ERK. The tumor suppressor function of DLC1 is attenuated by phosphorylation of tyrosines Y451 and Y701 by SRC, which down-regulates DLC1’s tensin-binding and Rho-GAP activities. ERK1/2 phosphorylate DLC1 on serine S129, which increases both the binding of SRC to DLC1 and SRC-dependent phosphorylation of DLC1. SRC inhibitors exhibit potent antitumor...
Source: Journal of Cell Biology - September 1, 2019 Category: Cytology Authors: Tripathi, B. K., Anderman, M. F., Qian, X., Zhou, M., Wang, D., Papageorge, A. G., Lowy, D. R. Tags: Cell Signaling, Cancer Articles Source Type: research
SNX3 drives maturation of Borrelia phagosomes by forming a hub for PI(3)P, Rab5a, and galectin-9
The spirochete Borrelia burgdorferi, the causative agent of Lyme disease, is internalized by macrophages and processed in phagolysosomes. Phagosomal compaction, a crucial step in phagolysosome maturation, is driven by contact of Rab5a-positive vesicles with the phagosomal coat. We show that the sorting nexin SNX3 is transported with Rab5a vesicles and that its PX domain enables vesicle–phagosome contact by binding to PI(3)P in the phagosomal coat. Moreover, the C-terminal region of SNX3 recruits galectin-9, a lectin implicated in protein and membrane recycling, which we identify as a further regulator of phagosome co...
Source: Journal of Cell Biology - September 1, 2019 Category: Cytology Authors: Klose, M., Salloum, J. E., Gonschior, H., Linder, S. Tags: Trafficking, Immunology Articles Source Type: research
Retromer and TBC1D5 maintain late endosomal RAB7 domains to enable amino acid-induced mTORC1 signaling
Retromer is an evolutionarily conserved multiprotein complex that orchestrates the endocytic recycling of integral membrane proteins. Here, we demonstrate that retromer is also required to maintain lysosomal amino acid signaling through mTORC1 across species. Without retromer, amino acids no longer stimulate mTORC1 translocation to the lysosomal membrane, which leads to a loss of mTORC1 activity and increased induction of autophagy. Mechanistically, we show that its effect on mTORC1 activity is not linked to retromer’s role in the recycling of transmembrane proteins. Instead, retromer cooperates with the RAB7-GAP TBC...
Source: Journal of Cell Biology - September 1, 2019 Category: Cytology Authors: Kvainickas, A., Nägele, H., Qi, W., Dokladal, L., Jimenez-Orgaz, A., Stehl, L., Gangurde, D., Zhao, Q., Hu, Z., Dengjel, J., De Virgilio, C., Baumeister, R., Steinberg, F. Tags: Trafficking Articles Source Type: research
