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Binod Kumar, Dipanjan Dutta, Jawed Iqbal, Mairaj Ahmed Ansari, Arunava Roy, Leela Chikoti, Gina Pisano, Mohanan Valiya Veettil, Bala Chandran
Kaposi's sarcoma-associated herpesvirus (KSHV) binding to the endothelial cell surface heparan sulfate is followed by sequential interactions with α3β1, αVβ3 and αVβ5 integrins and Ephrin A2 receptor tyrosine kinase (EphA2R). These interactions activate host cell pre-existing FAK, Src, PI3-K and RhoGTPase signaling cascades, c-Cbl mediated ubiquitination of receptors, recruitment of CIB1, p130Cas and Crk adaptor molecules, and membrane bleb formation leading to lipid raft dependent macropinocytosis of KSHV into human microvascular dermal endothelial (HMVEC-d) cells...
October 2016: PLoS Pathogens
Kai Xu, Peter D Nagy
Positive-strand RNA viruses build extensive membranous replication compartments to support replication and protect the virus from antiviral responses by the host. These viruses require host factors and various lipids to form viral replication complexes (VRCs). The VRCs built by Tomato bushy stunt virus (TBSV) are enriched with phosphatidylethanolamine (PE) through a previously unknown pathway. To unravel the mechanism of PE enrichment within the TBSV replication compartment, in this paper, the authors demonstrate that TBSV co-opts the guanosine triphosphate (GTP)-bound active form of the endosomal Rab5 small GTPase via direct interaction with the viral replication protein...
October 2016: PLoS Biology
Natalya A Goloviznina, Santhosh Chakkaramakkil Verghese, Young Me Yoon, Oleh Taratula, Daniel L Marks, Peter Kurre
Mesenchymal stromal cells (MSC) present in the bone marrow (BM) microenvironment secrete cytokines and angiogenic factors that support the maintenance and regenerative expansion of hematopoietic stem and progenitor cells (HSPC). Here, we tested the hypothesis that extracellular vesicles (EVs) released by MSC contribute to the paracrine crosstalk that shapes hematopoietic function. We systematically characterized EV release by murine stromal cells and demonstrate that MSC-derived EVs prompt a loss of HSPC quiescence with concomitant expansion of murine myeloid progenitors...
October 7, 2016: Journal of Biological Chemistry
Franziska Wild, Muzamil Majid Khan, Tatjana Straka, Rüdiger Rudolf
Endocytosed nicotinic acetylcholine receptors (CHRN) are degraded via macroautophagy/autophagy during atrophic conditions and are accompanied by the autophagic regulator protein SH3GLB1. The present study addressed the functional role of SH3GLB1 on CHRN trafficking and its implementation. We found an augmented ratio of total SH3GLB1 to threonine-145 phosphorylated SH3GLB1 (SH3GLB1:p-SH3GLB1) under conditions of increased CHRN vesicle numbers. Overexpression of T145 phosphomimetic (T145E) and phosphodeficient (T145A) mutants of SH3GLB1, were found to either slow down or augment the processing of endocytic CHRN vesicles, respectively...
October 7, 2016: Autophagy
Natasha Pashkova, Tabitha A Peterson, Venkatramanan Krishnamani, Patrick Breheny, Mark Stamnes, Robert C Piper
We adapted the yeast 2-hybrid assay to simultaneously uncover multiple transient protein interactions within a single screen by using a strategy termed DEEPN (dynamic enrichment for evaluation of protein networks). This approach incorporates high-throughput DNA sequencing and computation to follow competition among a plasmid population encoding interacting partners. To demonstrate the capacity of DEEPN, we identify a wide range of ubiquitin-binding proteins, including interactors that we verify biochemically...
September 27, 2016: Cell Reports
Kristina Nieding, Veronika Matschke, Sven G Meuth, Florian Lang, Guiscard Seebohm, Nathalie Strutz-Seebohm
BACKGROUND/AIMS: Inherited, autosomal dominant spinocerebellar ataxia type 11 (SCA11) is caused by loss of function mutations of TTBK2 (tau tubulin kinase 2). Mutations observed in patients with SCA11 include truncated TTBK2(450). The present study explored the possibility that TTBK2 influences the function of the glutamate receptor GluK2. METHODS: GluK2 was expressed in Xenopus oocytes without and with additional expression of wild type TTBK2, the truncated mutant TTBK2(450), or the kinase dead mutants TTBK2(KD) and TTBK2(450/KD)...
2016: Cellular Physiology and Biochemistry
Ya Zhou, Fiona V Howell, Oleg O Glebov, David Albrecht, Gareth Williams, Patrick Doherty
Diacylglycerol lipase alpha (DAGLα) generates the endocannabinoid (eCB) 2-arachidonylglycerol (2-AG) that regulates the proliferation and differentiation of neural stem cells and serves as a retrograde signaling lipid at synapses. Nothing is known about the dynamics of DAGLα expression in cells and this is important as it will govern where 2-AG can be made and released. We have developed a new construct to label DAGLα at the surface of live cells and follow its trafficking. In hippocampal neurons a cell surface pool of DAGLα co-localizes with Homer, a postsynaptic density marker...
October 2016: Molecular and Cellular Neurosciences
Ana Kucera, Oddmund Bakke, Cinzia Progida
The small GTPase Rab9 has long been described as a protein that mediates endosome-to-trans-Golgi Network (TGN) transport, and specifically mannose-6-phospate receptor (MPR) recycling. However, studies have challenged this view by showing that Rab9 also is connected to sorting pathways toward the endolysosomal compartments. We recently characterized the spatio-temporal dynamics of Rab9 and, by using live cell imaging, we showed that it enters the endosomal pathway together with CI-MPR at the transition stage between early, Rab5-positive, and late, Rab7a-positive, endosomes...
July 2016: Communicative & Integrative Biology
Krisztina Hegedűs, Szabolcs Takáts, Attila Boda, András Jipa, Péter Nagy, Kata Varga, Attila L Kovács, Gábor Juhász
The small GTPase Rab5 promotes recruitment of the Ccz1-Mon1 guanosine exchange complex to endosomes to activate Rab7, which facilitates endosome maturation and fusion with lysosomes. How these factors function during autophagy is incompletely understood. Here we show that autophagosomes accumulate due to impaired fusion with lysosomes upon loss of the Ccz1-Mon1-Rab7 module in starved Drosophila fat cells. In contrast, autophagosomes generated in Rab5-null mutant cells normally fuse with lysosomes during the starvation response...
October 15, 2016: Molecular Biology of the Cell
Xiaoli Guo, Ginny G Farías, Rafael Mattera, Juan S Bonifacino
An open question in cell biology is how the general intracellular transport machinery is adapted to perform specialized functions in polarized cells such as neurons. Here we illustrate this adaptation by elucidating a role for the ubiquitous small GTPase Ras-related protein in brain 5 (Rab5) in neuronal polarity. We show that inactivation or depletion of Rab5 in rat hippocampal neurons abrogates the somatodendritic polarity of the transferrin receptor and several glutamate receptor types, resulting in their appearance in the axon...
September 6, 2016: Proceedings of the National Academy of Sciences of the United States of America
David H Murray, Marcus Jahnel, Janelle Lauer, Mario J Avellaneda, Nicolas Brouilly, Alice Cezanne, Hernán Morales-Navarrete, Enrico D Perini, Charles Ferguson, Andrei N Lupas, Yannis Kalaidzidis, Robert G Parton, Stephan W Grill, Marino Zerial
An early step in intracellular transport is the selective recognition of a vesicle by its appropriate target membrane, a process regulated by Rab GTPases via the recruitment of tethering effectors. Membrane tethering confers higher selectivity and efficiency to membrane fusion than the pairing of SNAREs (soluble N-ethylmaleimide-sensitive factor attachment protein receptors) alone. Here we address the mechanism whereby a tethered vesicle comes closer towards its target membrane for fusion by reconstituting an endosomal asymmetric tethering machinery consisting of the dimeric coiled-coil protein EEA1 (refs 6, 7) recruited to phosphatidylinositol 3-phosphate membranes and binding vesicles harbouring Rab5...
August 24, 2016: Nature
Lee Dolat, Elias T Spiliotis
Macropinocytosis, the internalization of extracellular fluid and material by plasma membrane ruffles, is critical for antigen presentation, cell metabolism, and signaling. Macropinosomes mature through homotypic and heterotypic fusion with endosomes and ultimately merge with lysosomes. The molecular underpinnings of this clathrin-independent endocytic pathway are largely unknown. Here, we show that the filamentous septin GTPases associate preferentially with maturing macropinosomes in a phosphatidylinositol 3,5-bisphosphate-dependent manner and localize to their contact/fusion sites with macropinosomes/endosomes...
August 29, 2016: Journal of Cell Biology
Mingqun Lin, Hongyan Liu, Qingming Xiong, Hua Niu, Zhihui Cheng, Akitsugu Yamamoto, Yasuko Rikihisa
Ehrlichia chaffeensis is an obligatory intracellular bacterium that causes a potentially fatal emerging zoonosis, human monocytic ehrlichiosis. E. chaffeensis has a limited capacity for biosynthesis and metabolism and thus depends mostly on host-synthesized nutrients for growth. Although the host cell cytoplasm is rich with these nutrients, as E. chaffeensis is confined within the early endosome-like membrane-bound compartment, only host nutrients that enter the compartment can be used by this bacterium. How this occurs is unknown...
August 19, 2016: Autophagy
Daniel M Houslay, Karen E Anderson, Tamara Chessa, Suhasini Kulkarni, Ralph Fritsch, Julian Downward, Jonathan M Backer, Len R Stephens, Phillip T Hawkins
Class I phosphoinositide 3-kinases (PI3Ks) catalyze production of the lipid messenger phosphatidylinositol 3,4,5-trisphosphate (PIP3), which plays a central role in a complex signaling network regulating cell growth, survival, and movement. This network is overactivated in cancer and inflammation, and there is interest in determining the PI3K catalytic subunit (p110α, p110β, p110γ, or p110δ) that should be targeted in different therapeutic contexts. Previous studies have defined unique regulatory inputs for p110β, including direct interaction with Gβγ subunits, Rac, and Rab5...
2016: Science Signaling
Bao-Jun Shi, Chun-Chun Liu, Jing Zhou, Shi-Qi Wang, Zhi-Can Gao, Xiao-Min Zhang, Bin Zhou, Pu-Yan Chen
UNLABELLED: Classical swine fever virus (CSFV), a member of the genus Pestivirus within the family Flaviviridae, is a small, enveloped, positive-strand RNA virus. Due to its economic importance to the pig industry, the biology and pathogenesis of CSFV have been investigated extensively. However, the mechanisms of CSFV entry into cells are not well characterized. In this study, we used systematic approaches to dissect CSFV cell entry. We first observed that CSFV infection was inhibited by chloroquine and NH4Cl, suggesting that viral entry required a low-pH environment...
October 15, 2016: Journal of Virology
Loredana Saveanu, Sophie Lotersztajn
No abstract text is available yet for this article.
September 1, 2016: American Journal of Physiology. Cell Physiology
Brian Spencer, Paula A Desplats, Cassia R Overk, Elvira Valera-Martin, Robert A Rissman, Chengbiao Wu, Michael Mante, Anthony Adame, Jazmin Florio, Edward Rockenstein, Eliezer Masliah
UNLABELLED: Alzheimer's disease (AD) is characterized by the progressive accumulation of amyloid β (Aβ) and microtubule associate protein tau, leading to the selective degeneration of neurons in the neocortex, limbic system, and nucleus basalis, among others. Recent studies have shown that α-synuclein (α-syn) also accumulates in the brains of patients with AD and interacts with Aβ and tau, forming toxic hetero-oligomers. Although the involvement of α-syn has been investigated extensively in Lewy body disease, less is known about the role of this synaptic protein in AD...
July 27, 2016: Journal of Neuroscience: the Official Journal of the Society for Neuroscience
Sandra Oetjen, Dietmar Kuhl, Guido Hermey
Juvenile Neuronal Ceroid Lipofuscinosis (JNCL), the most common neurodegenerative disease affecting children, is caused by mutations of the CLN3 gene encoding CLN3, a transmembrane protein with so far undefined function. The embryonic expression of the gene has not been studied in detail before. Moreover, the protein CLN3 was mostly localized on the subcellular level to lysosomes but the exclusiveness is still under debate. Here, we analyze the expression pattern of murine CLN3 at different developmental stages by in situ hybridizations...
July 25, 2016: Journal of Neurochemistry
E R Mingazov, M V Ugrumov
It is assumed that one of the causes of the degeneration of dopaminergic neurons is the dysregulation of the vesicle cycle, which is ensured by a number of proteins including syntaxin I, synaptotagmin I, complexins I and II, and Rab5. It was shown that there is a compensatory increase in gene expression of proteins responsible for exocytosis at the preclinical stage of Parkinson's disease (PD) in the in substantia nigra (SN) in mice. Conversely, in the model of the clinical stage of PD, the decreases of gene expression of proteins responsible for exocytosis, endocytosis, and neuronal survival, which may be among the triggers of motor dysfunctions...
May 2016: Doklady. Biochemistry and Biophysics
Teresa Garcia-Aguilar, Patricia Espinosa-Cueto, Alejandro Magallanes-Puebla, Raúl Mancilla
Upon Mycobacterium tuberculosis infection, macrophages may undergo apoptosis, which has been considered an innate immune response. The pathways underlying the removal of dead cells in homeostatic apoptosis have been extensively studied, but little is known regarding how cells that undergo apoptotic death during mycobacterial infection are removed. This study shows that macrophages induced to undergo apoptosis with mycobacteria cell wall proteins are engulfed by J-774A.1 monocytic cells through the mannose receptor...
2016: Journal of Immunology Research
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