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Molecular Biology of the Cell

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https://www.readbyqxmd.com/read/28720664/dynein-efficiently-navigates-the-dendritic-cytoskeleton-to-drive-the-retrograde-trafficking-of-bdnf-trkb-signaling-endosomes
#1
Swathi Ayloo, Pedro Guedes-Dias, Amy E Ghiretti, Erika L F Holzbaur
The efficient transport of cargoes within axons and dendrites is critical for neuronal function. While we have a basic understanding of axonal transport, much less is known about transport in dendrites. We employed an optogenetic approach to recruit motor proteins to cargo in real time within axons or dendrites in hippocampal neurons. Kinesin-1, a robust axonal motor, moves cargo less efficiently in dendrites. In contrast, cytoplasmic dynein efficiently navigates both axons and dendrites; in both compartments, dynamic microtubule plus-ends enhance dynein-dependent transport...
July 18, 2017: Molecular Biology of the Cell
https://www.readbyqxmd.com/read/28720663/direct-interaction-of-the-golgi-v-atpase-a-subunit-isoform-with-pi-4-p-drives-localization-of-golgi-v-atpases-in-yeast
#2
Subhrajit Banerjee, Patricia M Kane
Luminal pH and phosphoinositide content are fundamental features of organelle identity. V-ATPases drive organelle acidification in all eukaryotes, and membrane-bound a-subunit isoforms of the V-ATPase are implicated in organelle-specific targeting and regulation. Earlier work demonstrated that the endo-lysosomal lipid PI(3,5)P2 activates V-ATPases containing the vacuolar a-subunit isoform in S. cerevisiae Here we demonstrate that PI4P, the predominant Golgi PI species, directly interacts with the cytosolic amino terminal (NT) domain of the yeast Golgi V-ATPase a-isoform, Stv1...
July 18, 2017: Molecular Biology of the Cell
https://www.readbyqxmd.com/read/28720662/proximal-tubule-apical-endocytosis-is-modulated-by-fluid-shear-stress-via-an-mtor-dependent-pathway
#3
Kimberly R Long, Katherine E Shipman, Youssef Rbaibi, Elizabeth V Menshikova, Vladimir B Ritov, Megan L Eshbach, Yu Jiang, Edwin K Jackson, Catherine J Baty, Ora A Weisz
Cells lining the proximal tubule (PT) have unique membrane specializations that are required to maintain the high capacity ion transport and endocytic functions of this nephron segment. PT cells in vivo acutely regulate ion transport in response to changes in glomerular filtration rate (GFR) to maintain glomerulotubular balance. PT cells in culture upregulate endocytic capacity in response to acute changes in fluid shear stress (FSS); however it is not known whether GFR modulates PT endocytosis to enable maximally efficient uptake of filtered proteins in vivo Here we show that cells cultured under continuous FSS develop an expanded apical endocytic pathway as well as increased endocytic capacity and lysosomal biogenesis...
July 18, 2017: Molecular Biology of the Cell
https://www.readbyqxmd.com/read/28720661/stabilization-of-f-actin-by-tropomyosin-isoforms-regulates-the-morphology-and-mechanical-behavior-of-red-blood-cells
#4
Zhenhua Sui, David S Gokhin, Roberta B Nowak, Xinhua Guo, Xiuli An, Velia M Fowler
The short F-actins in the red blood cell (RBC) membrane skeleton are coated along their lengths by an equimolar combination of two tropomyosin isoforms, Tpm1.9 and Tpm3.1. We hypothesized that tropomyosins' ability to stabilize F-actin regulates RBC morphology and mechanical properties. To test this, we examined mice with a targeted deletion in alternatively spliced exon 9d of Tpm3 (Tpm3/9d(-/-) ), which leads to absence of Tpm3.1 in RBCs along with a compensatory increase in Tpm1.9 of sufficient magnitude to maintain normal total tropomyosin content...
July 18, 2017: Molecular Biology of the Cell
https://www.readbyqxmd.com/read/28720660/an-amish-founder-mutation-disrupts-a-pi-3-p-whamm-arp2-3-complex-driven-autophagosome-remodeling-pathway
#5
Alyssa J Mathiowetz, Emma Baple, Ashley J Russo, Alyssa M Coulter, Eric Carrano, Judith D Brown, Robert N Jinks, Andrew H Crosby, Kenneth G Campellone
Actin nucleation factors function to organize, shape, and move membrane-bound organelles, yet they remain poorly defined in relation to disease. Galloway-Mowat syndrome (GMS) is an inherited disorder characterized by microcephaly and nephrosis resulting from mutations in the WDR73 gene. This core clinical phenotype appears frequently in the Amish, where virtually all affected individuals harbor homozygous founder mutations in WDR73 as well as the closely linked WHAMM gene, which encodes a nucleation factor...
July 18, 2017: Molecular Biology of the Cell
https://www.readbyqxmd.com/read/28701349/actin-cytoskeleton-dependent-regulation-of-corticotropin-releasing-factor-receptor-heteromers
#6
Burcu Hasdemir, Shilpi Mahajan, Juan Oses-Prieto, Shreya Chand, Michael Woolley, Alma Burlingame, Dimitris K Grammatopoulos, Aditi Bhargava
Stress responses are highly nuanced and variable, but how this diversity is achieved by modulating receptor function, is largely unknown. Corticotropin-releasing factor receptors (CRFRs), class B GPCRs, are pivotal in mediating stress responses. Here we show that the two known CRFRs interact to form heteromeric complexes in HEK293 cells co-expressing both CRFRs and in vivo in mouse pancreas. Co-immunoprecipitation and mass spectrometry confirmed the presence of both CRF1R and CRF2βR, along with actin in these heteromeric complexes...
July 12, 2017: Molecular Biology of the Cell
https://www.readbyqxmd.com/read/28701348/dna-damage-regulates-direct-association-of-tor-kinase-with-the-rna-polymerase-ii-transcribed-hmo1-gene
#7
Arvind Panday, Ashish Gupta, Kavitha Srinivasa, Lijuan Xiao, Mathew D Smith, Anne Grove
The mechanistic target of rapamycin complex 1 (mTORC1) senses nutrient sufficiency and cellular stress. When mTORC1 is inhibited, protein synthesis is reduced in an intricate process that includes a concerted downregulation of genes encoding rRNA and ribosomal proteins. The Saccharomyces cerevisiae high mobility group protein Hmo1p has been implicated in coordinating this response to mTORC1 inhibition. We show here that Tor1p binds directly to the HMO1 gene (but not to genes that are not linked to ribosome biogenesis) and that presence of Tor1p is associated with activation of gene activity...
July 12, 2017: Molecular Biology of the Cell
https://www.readbyqxmd.com/read/28701347/a-casein-kinase-1-prevents-expulsion-of-the-oocyte-meiotic-spindle-into-a-polar-body-by-regulating-cortical-contractility
#8
Jonathan R Flynn, Francis J McNally
During female meiosis, haploid eggs are generated from diploid oocytes. This reduction in chromosome number occurs through two highly asymmetric cell divisions resulting in one large egg and two small polar bodies. Unlike mitosis, where an actomyosin contractile ring forms between the sets of segregating chromosomes, the meiotic contractile ring forms on the cortex adjacent to one spindle pole, then ingresses down the length of the spindle to position itself at the exact midpoint between the two sets of segregating chromosomes...
July 12, 2017: Molecular Biology of the Cell
https://www.readbyqxmd.com/read/28701346/the-n-terminus-of-ift46-mediates-intraflagellar-transport-of-outer-arm-dynein-and-its-cargo-adaptor-oda16
#9
Yuqing Hou, George B Witman
Cilia are assembled via intraflagellar transport (IFT). The IFT machinery is composed of motors and multi-subunit particles, termed IFT-A and IFT-B, that carry cargo into the cilium. Knowledge of how the IFT subunits interact with their cargo is of critical importance for understanding how the unique ciliary domain is established. We previously reported a Chlamydomonas mutant, ift46-1, that fails to express the IFT-B protein IFT46, has greatly reduced levels of other IFT-B proteins, and assembles only very short flagella...
July 12, 2017: Molecular Biology of the Cell
https://www.readbyqxmd.com/read/28701345/trim9-dependent-ubiquitination-of-dcc-constrains-kinase-signaling-exocytosis-and-axon-branching
#10
Melissa Plooster, Shalini Menon, Cortney C Winkle, Fabio L Urbina, Caroline Monkiewicz, Kristen D Phend, Richard J Weinberg, Stephanie L Gupton
Extracellular netrin-1 and its receptor DCC promote axon branching in developing cortical neurons. Netrin-dependent morphogenesis is preceded by multimerization of DCC, activation of FAK and Src family kinases, and increases in exocytic vesicle fusion, yet how these occurrences are linked is unknown. Here we demonstrate that TRIM9-dependent ubiquitination of DCC blocks the interaction with and phosphorylation of FAK. Upon netrin-1 stimulation TRIM9 promotes DCC multimerization, but TRIM9-dependent ubiquitination of DCC is reduced, which promotes an interaction with FAK and subsequent FAK activation...
July 12, 2017: Molecular Biology of the Cell
https://www.readbyqxmd.com/read/28701344/syp1-regulates-the-clathrin-mediated-and-clathrin-independent-endocytosis-of-multiple-cargo-proteins-through-a-novel-sorting-motif
#11
Amanda Reider Apel, Kyle Hoban, Silvia Chuartzman, Raffi Tonikian, Sachdev Sidhu, Maya Schuldiner, Beverly Wendland, Derek Prosser
Internalization of proteins from the plasma membrane (PM) allows for cell-surface composition regulation, signaling network modulation, and nutrient uptake. Clathrin-mediated endocytosis (CME) is a major internalization route for PM proteins. During CME, endocytic adaptor proteins bind cargos at the cell surface and link them to the PM and clathrin coat. Muniscins are a conserved family of endocytic adaptors, including Syp1 in budding yeast and its mammalian ortholog, FCHo1. These adaptors bind cargo via a C-terminal ì-homology domain (ìHD); however, few cargos exhibiting muniscin-dependent endocytosis have been identified, and the sorting sequence recognized by the μHD is unknown...
July 12, 2017: Molecular Biology of the Cell
https://www.readbyqxmd.com/read/28701343/let-99-functions-in-the-astral-furrowing-pathway-where-it-is-required-for-myosin-enrichment-in-the-contractile-ring
#12
Kari L Price, Lesilee S Rose
The anaphase spindle determines the position of the cytokinesis furrow, such that the contractile ring assembles in an equatorial zone between the two spindle poles. Contractile ring formation is mediated by RhoA activation at the equator by the centralspindlin complex and midzone microtubules. Astral microtubules also inhibit RhoA accumulation at the poles. In the C. elegans one-cell embryo, the astral microtubule dependent pathway requires anillin, NOP-1 and LET-99. LET-99 is well characterized for generating the asymmetric cortical localization of the Gα-dependent force-generating complex that positions the spindle during asymmetric division...
July 12, 2017: Molecular Biology of the Cell
https://www.readbyqxmd.com/read/28701342/activating-transcription-factor-3-promotes-loss-of-the-acinar-cell-phenotype-in-response-to-cerulein-induced-pancreatitis-in-mice
#13
Elena N Fazio, Claire C Young, Jelena Toma, Michael Levy, Kurt R Berger, Charis L Johnson, Rashid Mehmood, Patrick Swan, Alphonse Chu, Sean P Cregan, F Jeffrey Dilworth, Christopher J Howlett, Christopher L Pin
Pancreatitis is a debilitating disease of the exocrine pancreas that, under chronic conditions, is a major susceptibility factor for pancreatic ductal adenocarcinoma (PDAC). While down-regulation of genes that promote the mature acinar cell fate is required to reduce injury associated with pancreatitis, the factors that promote this repression are unknown. Activating transcription factor 3 (ATF3) is a key mediator of the unfolded protein response, a pathway rapidly activated during pancreatic insult. Using chromatin immunoprecipitation followed by Next Generation Sequencing, we show that ATF3 is bound to the transcriptional regulatory regions of more than 30% of differentially expressed genes during the initiation of pancreatitis...
July 12, 2017: Molecular Biology of the Cell
https://www.readbyqxmd.com/read/28701341/computer-simulations-reveal-mechanisms-that-organize-nuclear-dynein-forces-to-separate-centrosomes
#14
Alessandro De Simone, Pierre Gönczy
Centrosome separation along the surface of the nucleus at the onset of mitosis is critical for bipolar spindle assembly. Dynein anchored on the nuclear envelope is known to be important for centrosome separation, but it is unclear how nuclear dynein forces are organized in an anisotropic manner to promote the movement of centrosomes away from each other. Here, we use computational simulations of C. elegans embryos to address this fundamental question, testing three potential mechanisms by which nuclear dynein may act...
July 12, 2017: Molecular Biology of the Cell
https://www.readbyqxmd.com/read/28701340/cenp-f-couples-cargo-to-growing-and-shortening-microtubule-ends
#15
Gil Kanfer, Martin Peterka, Vladimir K Arzhanik, Alexei L Drobyshev, Fazly I Ataullakhanov, Vladimir A Volkov, Benoît Kornmann
Dynamic microtubule ends exert pulling and pushing forces on intracellular membranes and organelles. However, the mechanical linkage of microtubule tips to their cargoes is poorly understood. CENP-F is a non-motor microtubule-binding protein that participates in microtubule binding at kinetochores and in the mitotic redistribution of the mitochondrial network. CENP-F-driven mitochondrial transport is linked to growing microtubule tips, but the underlying molecular mechanisms are unknown. Here we show that CENP-F tracks growing microtubule ends in living cells...
July 12, 2017: Molecular Biology of the Cell
https://www.readbyqxmd.com/read/28659416/haspin-inhibition-reveals-functional-differences-of-interchromatid-axis-localized-aurkb-and-aurkc
#16
Suzanne M Quartuccio, Shweta S Dipali, Karen Schindler
Aneuploidy is the leading genetic abnormality contributing to infertility, and chromosome segregation errors are common during female mammalian meiosis I (MI). Previous results indicate that haspin kinase regulates resumption of meiosis from prophase arrest, chromosome condensation, and kinetochore-microtubule attachments during early prometaphase of MI. Here, we report that haspin inhibition in late prometaphase I causes acceleration of MI, bypass of the spindle assembly checkpoint (SAC), and loss of interchromatid axis localized Aurora kinase C...
June 28, 2017: Molecular Biology of the Cell
https://www.readbyqxmd.com/read/28659415/single-molecule-imaging-of-the-bar-domain-protein-pil1p-reveals-filament-end-dynamics
#17
Michael M Lacy, David Baddeley, Julien Berro
Molecular assemblies can have highly heterogeneous dynamics within the cell, but the limitations of conventional fluorescence microscopy can mask nanometer-scale features. Here we adapt a single-molecule strategy to perform Single-molecule Recovery After Photobleaching (SRAP) within dense macromolecular assemblies to reveal and characterize binding and unbinding dynamics within such assemblies. We applied this method to study the eisosome, a stable assembly of BAR-domain proteins on the cytoplasmic face of the plasma membrane in fungi...
June 28, 2017: Molecular Biology of the Cell
https://www.readbyqxmd.com/read/28637769/potential-contribution-of-tandem-circadian-enhancers-to-nonlinear-oscillations-in-clock-gene-expression
#18
Isao T Tokuda, Akihiko Okamoto, Ritsuko Matsumura, Toru Takumi, Makoto Akashi
Limit cycle oscillations require the presence of nonlinear processes. Although mathematical studies have long suggested that multiple nonlinear processes are required for autonomous circadian oscillation in clock gene expression, the underlying mechanism remains controversial. Here, we experimentally show that cell-autonomous circadian transcription of a mammalian clock gene requires a functionally interdependent tandem E-box motif; the lack of either of the two E-boxes results in arrhythmic transcription. Although previous studies have indicated the role of the tandem motifs in increasing circadian amplitude, enhancing amplitude does not explain the mechanism for limit cycle oscillations in transcription...
June 21, 2017: Molecular Biology of the Cell
https://www.readbyqxmd.com/read/28637768/vrk2a-is-an-a-type-lamin-dependent-nuclear-envelope-kinase-that-phosphorylates-baf
#19
K C Birendra, Danielle G May, Benjamin V Benson, Dae In Kim, Winnie G Shivega, Manaal H Ali, Randolph S Faustino, Alexandre R Campos, Kyle J Roux
The nuclear envelope (NE) is critical for numerous fundamental cellular functions and mutations in several NE constituents can lead to a heterogeneous spectrum of diseases. We used proximity biotinylation to uncover new constituents of the inner nuclear membrane (INM) by comparative BioID analysis of lamin-A, Sun2 and a minimal INM-targeting motif. These studies identified vaccinia-related kinase-2 (VRK2) as a candidate constituent of the INM. We determined that the transmembrane VRK2A isoform is retained at the NE by association with A-type lamins...
June 21, 2017: Molecular Biology of the Cell
https://www.readbyqxmd.com/read/28637767/a-short-region-upstream-of-the-yeast-vacuolar-qa-snare-heptad-repeats-promotes-membrane-fusion-through-enhanced-snare-complex-assembly
#20
Hongki Song, William Wickner
While SNARE heptad-repeats are well studied, SNAREs also have upstream N-domains of indeterminate function. The assembly of yeast vacuolar SNAREs into complexes for fusion can be studied in chemically-defined reactions. Complementary proteoliposomes bearing a Rab:GTP and either the vacuolar R-SNARE or one of the 3 integrally-anchored Q-SNAREs were incubated with the tethering/SM protein complex HOPS and the two other soluble SNAREs (lacking a trans-membrane anchor) or their SNARE heptad-repeat domains. Fusion required a trans-membrane anchored R-SNARE on one membrane and an anchored Q-SNARE on the other...
June 21, 2017: Molecular Biology of the Cell
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