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https://www.readbyqxmd.com/read/28100639/munc13-4-functions-as-a-ca2-sensor-for-homotypic-secretory-granule-fusion-to-generate-endosomal-exocytic-vacuoles
#1
Sang Su Woo, Declan J James, Thomas F J Martin
Munc13-4 is a Ca(2+)-dependent SNARE- and phospholipid-binding protein that localizes to and primes secretory granules (SGs) for Ca(2+)-evoked secretion in various secretory cells. Studies in mast cell-like RBL-2H3 cells provides direct evidence that Munc13-4 with its two Ca(2+)-binding C2 domains functions as a Ca(2+) sensor for SG exocytosis. Unexpectedly, Ca(2+) stimulation also generated large (>2.4 μm diameter) Munc13-4(+)/Rab7(+)/Rab11(+) endosomal vacuoles. Vacuole generation involved the homotypic fusion of Munc13-4(+)/Rab7(+) SGs followed by a merge with Rab11(+) endosomes, and depended on Ca(2+) binding to Munc13-4...
January 18, 2017: Molecular Biology of the Cell
https://www.readbyqxmd.com/read/28100638/retromer-driven-membrane-tubulation-separates-endosomal-recycling-from-rab7-ypt7-dependent-fusion
#2
Latha Kallur Purushothaman, Henning Arlt, Anne Kuhlee, Stefan Raunser, Christian Ungermann
Endosomes are the major protein sorting hubs of the endocytic pathway. They sort proteins destined for degradation into internal vesicles, while in parallel recycling receptors via tubular carriers back to the Golgi. Tubule formation depends on the Rab7/Ypt7-interacting retromer complex, consisting of the sorting nexin dimer (SNX-BAR) and the trimeric cargo selection complex (CSC). Fusion of mature endosomes with the lysosome-like vacuole also requires Rab7/Ypt7. Here, we now solved a major problem in understanding this dual function of endosomal Rab7/Ypt7 using a fully reconstituted system, including purified, full-length yeast SNX-BAR and CSC, whose overall structure we present...
January 18, 2017: Molecular Biology of the Cell
https://www.readbyqxmd.com/read/28088841/intracellular-fate-of-ureaplasma-parvum-entrapped-by-host-cellular-autophagy
#3
Fumiko Nishiumi, Michinaga Ogawa, Yukiko Nakura, Yusuke Hamada, Masahiro Nakayama, Jiro Mitobe, Atsushi Hiraide, Norio Sakai, Makoto Takeuchi, Tamotsu Yoshimori, Itaru Yanagihara
Genital mycoplasmas, including Ureaplasma spp., are among the smallest human pathogenic bacteria and are associated with preterm birth. Electron microscopic observation of U. parvum showed that these prokaryotes have a regular, spherical shape with a mean diameter of 146 nm. U. parvum was internalized into HeLa cells by clathrin-mediated endocytosis and survived for at least 14 days around the perinuclear region. Intracellular U. parvum reached endosomes in HeLa cells labeled with EEA1, Rab7, and LAMP-1 within 1 to 3 hr...
January 15, 2017: MicrobiologyOpen
https://www.readbyqxmd.com/read/28077646/adenovirus-modulates-toll-like-receptor-4-signaling-by-reprogramming-orp1l-vap-protein-contacts-for-cholesterol-transport-from-endosomes-to-the-endoplasmic-reticulum
#4
Nicholas L Cianciola, Stacey Chung, Danny Manor, Cathleen R Carlin
: Human adenoviruses generally cause mild self-limiting infections but can lead to serious disease and even be fatal in high-risk individuals, underscoring the importance of understanding how the virus counteracts host defense mechanisms. This study had two goals. First, determine the molecular basis of cholesterol homeostatic responses induced by the early region 3 membrane protein RIDα via its direct interaction with the sterol-binding protein ORP1L. Second, determine how this interaction regulates innate immunity to adenovirus...
January 11, 2017: Journal of Virology
https://www.readbyqxmd.com/read/28067668/adaptor-proteins-numb-and-numbl-promote-cell-cycle-withdrawal-by-targeting-erbb2-for-degradation
#5
Maretoshi Hirai, Yoh Arita, C Jane McGlade, Kuo-Fen Lee, Ju Chen, Sylvia M Evans
Failure of trabecular myocytes to undergo appropriate cell cycle withdrawal leads to ventricular noncompaction and heart failure. Signaling of growth factor receptor ERBB2 is critical for myocyte proliferation and trabeculation. However, the mechanisms underlying appropriate downregulation of trabecular ERBB2 signaling are little understood. Here, we have found that the endocytic adaptor proteins NUMB and NUMBL were required for downregulation of ERBB2 signaling in maturing trabeculae. Loss of NUMB and NUMBL resulted in a partial block of late endosome formation, resulting in sustained ERBB2 signaling and STAT5 activation...
January 9, 2017: Journal of Clinical Investigation
https://www.readbyqxmd.com/read/28052003/mir-138-5p-suppresses-autophagy-in-pancreatic-cancer-by-targeting-sirt1
#6
She Tian, Xingjun Guo, Chao Yu, Chengyi Sun, Jianxin Jiang
The role of microRNA in the aberrant autophagy that occurs in pancreatic cancer remains controversial. Because hypoxia is known to induce autophagy, we screened for differentially expressed microRNAs using a miRNA microarray with pancreatic cancer cells cultured under normoxic and hypoxic conditions. We found that miR-138-5p was among the most downregulated miRNA in hypoxia-stimulated cells, and that overexpression of miR-138-5p substantially reduced expression of autophagy markers. In addition, western blot and immunofluorescence analyses and electron microscopy revealed that miR-138-5p inhibited autophagy in pancreatic cancer cells and blocked serum starvation-induced autophagic flux independently of the typical autophagic signaling pathway...
December 29, 2016: Oncotarget
https://www.readbyqxmd.com/read/28051187/architecture-and-mechanism-of-the-late-endosomal-rab7-like-ypt7-guanine-nucleotide-exchange-factor-complex-mon1-ccz1
#7
Stephan Kiontke, Lars Langemeyer, Anne Kuhlee, Saskia Schuback, Stefan Raunser, Christian Ungermann, Daniel Kümmel
The Mon1-Ccz1 complex (MC1) is the guanine nucleotide exchange factor (GEF) for the Rab GTPase Ypt7/Rab7 and is required for endosomal maturation and fusion at the vacuole/lysosome. Here we present the overall architecture of MC1 from Chaetomium thermophilum, and in combining biochemical studies and mutational analysis in yeast, we identify the domains required for catalytic activity, complex assembly and localization of MC1. The crystal structure of a catalytic MC1 core complex bound to Ypt7 provides mechanistic insight into its function...
January 4, 2017: Nature Communications
https://www.readbyqxmd.com/read/28035045/multiphasic-dynamics-of-phosphatidylinositol-4-phosphate-during-phagocytosis
#8
Roni Levin, Gerald R V Hammond, Tamas Balla, Pietro De Camilli, Gregory D Fairn, Sergio Grinstein
We analyzed the distribution, fate, and functional role of phosphatidylinositol 4-phosphate (PtdIns4P) during phagosome formation and maturation. To this end, we used genetically encoded probes consisting of the PtdIns4P-binding domain of the bacterial effector SidM. PtdIns4P was found to undergo complex, multiphasic changes during phagocytosis. The phosphoinositide, which is present in the plasmalemma before engagement of the target particle, is transiently enriched in the phagosomal cup. Soon after the phagosome seals, PtdIns4P levels drop precipitously due to the hydrolytic activity of Sac2 and phospholipase C, becoming undetectable for ∼10 min...
January 1, 2017: Molecular Biology of the Cell
https://www.readbyqxmd.com/read/28011901/efferocytosis-is-impaired-in-gaucher-macrophages
#9
Elma Aflaki, Daniel K Borger, Richard J Grey, Martha Kirby, Stacie Anderson, Grisel Lopez, Ellen Sidransky
Gaucher disease, the inherited deficiency of lysosomal glucocerebrosidase, is characterized by the presence of glucosylceramide-laden macrophages resulting from impaired digestion of aged erythrocytes or apoptotic leukocytes. Studies of macrophages from patients with type 1 Gaucher disease with genotypes N370S/N370S, N370S/L444P or N370S/c.84dupG revealed that Gaucher macrophages have impaired efferocytosis resulting from reduced levels of p67phox and Rab7. The decreased Rab7 expression leads to impaired fusion of phagosomes with lysosomes...
December 23, 2016: Haematologica
https://www.readbyqxmd.com/read/27994678/the-role-of-bca2-in-the-endocytic-trafficking-of-egfr-and-significance-as-a-prognostic-biomarker-in-cancer
#10
Jennifer M Wymant, Stephen Hiscox, Andrew D Westwell, Sylvie Urbé, Michael J Clague, Arwyn T Jones
Breast Cancer Associated gene 2 (BCA2) is an E3 ubiquitin ligase that is over-expressed in >50% of primary breast cancers, and has been shown to increase in vitro cell proliferation and invasion. The protein has been linked to alterations in EGFR degradation; however there is some dispute as to its role and influence on the biology of this receptor. Our work aimed to ascertain the role of BCA2 in EGFR endocytosis and down-regulation and to examine its links with breast cancer outcome. Data generated with the online expression analysis tool KM-Plotter showed that high BCA2 levels are associated with poor prognosis in ovarian, gastric and breast cancer, particularly HER2 over-expressing breast cancers...
2016: Journal of Cancer
https://www.readbyqxmd.com/read/27927752/vesicular-ptdins-3-4-5-p3-and-rab-7-are-key-effectors-of-zygote-nuclear-membrane-fusion
#11
Marta G Lete, Richard D Byrne, Alicia Alonso, Dominic Poccia, Banafshé Larijani
Regulation of nuclear envelope (NE) dynamics is an important example of the universal phenomena of membrane fusion. The signalling molecules involved in nuclear membrane fusion may also be conserved in the formation of both pronuclear and zygote NEs in the fertilised egg. Here, we determine that Class I PI3-kinases are needed for in vitro nuclear envelope formation. We show that, in vivo, PtdIns(3,4,5)P3 is transiently located in vesicles around the male pronucleus at the time of nuclear envelope formation and around male and female pronuclei prior to membrane fusion...
December 7, 2016: Journal of Cell Science
https://www.readbyqxmd.com/read/27903237/leucine-rich-repeat-kinase-2-lrrk2-regulates-%C3%AE-synuclein-clearance-in-microglia
#12
Tatsunori Maekawa, Toshikuni Sasaoka, Sadahiro Azuma, Takafumi Ichikawa, Heather L Melrose, Matthew J Farrer, Fumiya Obata
BACKGROUND: α-Synuclein (αSYN) has been genetically implicated in familial and sporadic Parkinson's disease (PD), and is associated with disease susceptibility, progression and pathology. Excess amounts of αSYN are toxic to neurons. In the brain, microglial αSYN clearance is closely related to neuronal survival. Leucine-rich repeat kinase 2 (LRRK2) is the one of the other genes implicated in familial and sporadic PD. While LRRK2 is known to be expressed in microglia, its true function remains to be elucidated...
November 30, 2016: BMC Neuroscience
https://www.readbyqxmd.com/read/27882110/intermittent-fasting-is-neuroprotective-in-focal-cerebral-ischemia-by-minimizing-autophagic-flux-disturbance-and-inhibiting-apoptosis
#13
Ji Heun Jeong, Kwang Sik Yu, Dong Ho Bak, Je Hun Lee, Nam Seob Lee, Young Gil Jeong, Dong Kwan Kim, Jwa-Jin Kim, Seung-Yun Han
Previous studies have demonstrated that autophagy induced by caloric restriction (CR) is neuroprotective against cerebral ischemia. However, it has not been determined whether intermittent fasting (IF), a variation of CR, can exert autophagy-related neuroprotection against cerebral ischemia. Therefore, the neuroprotective effect of IF was evaluated over the course of two weeks in a rat model of focal cerebral ischemia, which was induced by middle cerebral artery occlusion and reperfusion (MCAO/R). Specifically, the role of autophagy modulation as a potential underlying mechanism for this phenomenon was investigated...
November 2016: Experimental and Therapeutic Medicine
https://www.readbyqxmd.com/read/27881733/lysosomal-trafficking-regulator-lyst-links-membrane-trafficking-to-toll-like-receptor-mediated-inflammatory-responses
#14
Andreas Westphal, Weijia Cheng, Jinbo Yu, Guntram Grassl, Martina Krautkrämer, Otto Holst, Niko Föger, Kyeong-Hee Lee
Subcellular compartmentalization of receptor signaling is an emerging principle in innate immunity. However, the functional integration of receptor signaling pathways into membrane trafficking routes and its physiological relevance for immune responses is still largely unclear. In this study, using Lyst-mutant beige mice, we show that lysosomal trafficking regulator Lyst links endolysosomal organization to the selective control of toll-like receptor 3 (TLR3)- and TLR4-mediated proinflammatory responses. Consequently, Lyst-mutant mice showed increased susceptibility to bacterial infection and were largely resistant to endotoxin-induced septic shock...
January 2017: Journal of Experimental Medicine
https://www.readbyqxmd.com/read/27852901/multivalent-rab-interactions-determine-tether-mediated-membrane-fusion
#15
Anna Lürick, Jieqiong Gao, Anne Kuhlee, Erdal Yavavli, Lars Langemeyer, Angela Perz, Stefan Raunser, Christian Ungermann
Membrane fusion at endomembranes requires cross-talk between Rab GTPases and tethers to drive SNARE-mediated lipid bilayer mixing. Several tethers have multiple Rab-binding sites with largely untested function. Here we dissected the lysosomal HOPS complex as a tethering complex with just two binding sites for the Rab7-like Ypt7 protein to determine their relevance for fusion. Using tethering and fusion assays combined with HOPS mutants, we show that HOPS-dependent fusion requires both Rab-binding sites, with Vps39 being the stronger Ypt7 interactor than Vps41...
January 15, 2017: Molecular Biology of the Cell
https://www.readbyqxmd.com/read/27852225/a-functional-endosomal-pathway-is-necessary-for-lysosome-biogenesis-in-drosophila
#16
Anne-Claire Jacomin, Marie-Odile Fauvarque, Emmanuel Taillebourg
BACKGROUND: Lysosomes are the major catabolic compartment within eukaryotic cells, and their biogenesis requires the integration of the biosynthetic and endosomal pathways. Endocytosis and autophagy are the primary inputs of the lysosomal degradation pathway. Endocytosis is specifically needed for the degradation of membrane proteins whereas autophagy is responsible for the degradation of cytoplasmic components. We previously identified the deubiquitinating enzyme UBPY/USP8 as being necessary for lysosomal biogenesis and productive autophagy in Drosophila...
November 16, 2016: BMC Cell Biology
https://www.readbyqxmd.com/read/27848911/phospholipase-d-activity-couples-plasma-membrane-endocytosis-with-retromer-dependent-recycling
#17
Rajan Thakur, Aniruddha Panda, Elise Coessens, Nikita Raj, Shweta Yadav, Sruthi Balakrishnan, Qifeng Zhang, Plamen Georgiev, Bishal Basak, Renu Pasricha, Michael Jo Wakelam, Nicholas T Ktistakis, Padinjat Raghu
During illumination, the light-sensitive plasma membrane (rhabdomere) of Drosophila photoreceptors undergoes turnover with consequent changes in size and composition. However, the mechanism by which illumination is coupled to rhabdomere turnover remains unclear. We find that photoreceptors contain a light-dependent phospholipase D (PLD) activity. During illumination, loss of PLD resulted in an enhanced reduction in rhabdomere size, accumulation of Rab7 positive, rhodopsin1-containing vesicles (RLVs) in the cell body and reduced rhodopsin protein...
November 16, 2016: ELife
https://www.readbyqxmd.com/read/27827364/structural-and-mechanistic-insights-into-regulation-of-the-retromer-coat-by-tbc1d5
#18
Da Jia, Jin-San Zhang, Fang Li, Jing Wang, Zhihui Deng, Mark A White, Douglas G Osborne, Christine Phillips-Krawczak, Timothy S Gomez, Haiying Li, Amika Singla, Ezra Burstein, Daniel D Billadeau, Michael K Rosen
Retromer is a membrane coat complex that is recruited to endosomes by the small GTPase Rab7 and sorting nexin 3. The timing of this interaction and consequent endosomal dynamics are thought to be regulated by the guanine nucleotide cycle of Rab7. Here we demonstrate that TBC1d5, a GTPase-activating protein (GAP) for Rab7, is a high-affinity ligand of the retromer cargo selective complex VPS26/VPS29/VPS35. The crystal structure of the TBC1d5 GAP domain bound to VPS29 and complementary biochemical and cellular data show that a loop from TBC1d5 binds to a conserved hydrophobic pocket on VPS29 opposite the VPS29-VPS35 interface...
November 9, 2016: Nature Communications
https://www.readbyqxmd.com/read/27815878/analysis-of-lc3-associated-phagocytosis-and-antigen-presentation
#19
Laure-Anne Ligeon, Susana Romao, Christian Münz
The noncanonical macroautophagy pathway, LC3-associated phagocytosis (LAP) has recently emerged as an important catabolic process involved during exogenous antigen processing. It has been described that in human macrophages and dendritic cells the direct recruitment of LC3 to the phagosomal membrane is associated with its maturation impairment, allowing the stabilization of the cargo to prolong antigen presentation on major histocompatibility complex (MHC) class II molecules.In this chapter, we describe methods to monitor, manipulate, and understand the role of LAP during MHC class II presentation...
2017: Methods in Molecular Biology
https://www.readbyqxmd.com/read/27799422/monensin-sensitivity1-mon1-calcium-caffeine-zinc-sensitivity1-ccz1-mediated-rab7-activation-regulates-tapetal-programmed-cell-death-and-pollen-development
#20
Yong Cui, Qiong Zhao, Hong-Tao Xie, Wing Shing Wong, Xiangfeng Wang, Caiji Gao, Yu Ding, Yuqi Tan, Takashi Ueda, Yan Zhang, Liwen Jiang
Programmed cell death (PCD)-triggered degradation of plant tapetum is essential for microspore development and pollen coat formation; however, little is known about the cellular mechanism regulating tapetal PCD Here, we demonstrate that Rab7-mediated vacuolar transport of tapetum degradation-related cysteine proteases is crucial for tapetal PCD and pollen development in Arabidopsis (Arabidopsis thaliana), with the following evidence: (1) The monensin sensitivity1 (mon1) mutants, which are defective in Rab7 activation, showed impaired male fertility due to a combined defect in both tapetum and male gametophyte development...
January 2017: Plant Physiology
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