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de Vreede G, Schoenfeld JD, Windler SL, Morrison H, Lu H, Bilder D. The Scribble module regulates retromer-dependent endocytic trafficking during epithelial polarization. Development 2014; 141:2796-802. [PMID: 25005475 DOI: 10.1242/dev.105403] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Scribble (Scrib) module proteins are major regulators of cell polarity, but how they influence membrane traffic is not known. Endocytosis is also a key regulator of polarity through roles that remain unclear. Here we link Scrib to a specific arm of the endocytic trafficking system. Drosophila mutants that block AP-2-dependent endocytosis share many phenotypes with Scrib module mutants, but Scrib module mutants show intact internalization and endolysosomal transport. However, defective traffic of retromer pathway cargo is seen, and retromer components show strong genetic interactions with the Scrib module. The Scrib module is required for proper retromer localization to endosomes and promotes appropriate cargo sorting into the retromer pathway via both aPKC-dependent and -independent mechanisms. We propose that the Scrib module regulates epithelial polarity by influencing endocytic itineraries of Crumbs and other retromer-dependent cargo.
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Affiliation(s)
- Geert de Vreede
- Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720-3200, USA
| | - Joshua D Schoenfeld
- Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720-3200, USA
| | - Sarah L Windler
- Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720-3200, USA
| | - Holly Morrison
- Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720-3200, USA
| | - Han Lu
- Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720-3200, USA
| | - David Bilder
- Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720-3200, USA
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202
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Matthews JC, Zhang Z, Patterson JD, Bridges PJ, Stromberg AJ, Boling JA. Hepatic transcriptome profiles differ among maturing beef heifers supplemented with inorganic, organic, or mixed (50% inorganic:50% organic) forms of dietary selenium. Biol Trace Elem Res 2014; 160:321-39. [PMID: 24996959 DOI: 10.1007/s12011-014-0050-4] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/18/2014] [Accepted: 06/16/2014] [Indexed: 12/27/2022]
Abstract
Selenium (Se) is an important trace mineral that, due to deficiencies in the soil in many parts of the USA, must be supplemented directly to the diet of foraging cattle. Both organic and inorganic forms of dietary Se supplements are available and commonly used, and it is known that Se form affects tissue assimilation, bioavailability, and physiological responses. However, little is known about the effects of form of dietary Se supplements on gene expression profiles, which ostensibly account for Se form-dependent physiological processes. To determine if hepatic transcriptomes of growing beef (Angus-cross) heifers (0.5 kg gain/day) was altered by form of dietary supplemental Se, none (Control), or 3 mg Se/day as inorganic Se (ISe, sodium selenite), organic (OSe, Sel-Plex®), or a blend of ISe and OSe (1.5 mg:1.5 mg, Mix) Se was fed for 168 days, and the RNA expression profiles from biopsied liver tissues was compared by microarray analysis. The relative abundance of 139 RNA transcripts was affected by Se treatment, with 86 of these with complete gene annotations. Statistical and bioinformatic analysis of the annotated RNA transcripts revealed clear differences among the four Se treatment groups in their hepatic expression profiles, including (1) solely and commonly affected transcripts; (2) Control and OSe profiles being more similar than Mix and ISe treatments; (3) distinct OSe-, Mix-, and ISe-Se treatment-induced "phenotypes" that possessed both common and unique predicted physiological capacities; and (4) expression of three microRNAs were uniquely sensitive to OSe, ISe, or Mix treatments, including increased capacity for redox potential induced by OSe and Mix Se treatments resulting from decreased expression of MiR2300b messenger RNA. These findings indicate that the form of supplemental dietary Se consumed by cattle will affect the composition of liver transcriptomes resulting, presumably, in different physiological capacities.
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Affiliation(s)
- James C Matthews
- Department of Animal and Food Sciences, University of Kentucky, Lexington, KY, 40546, USA,
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203
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Anwer MS. Role of protein kinase C isoforms in bile formation and cholestasis. Hepatology 2014; 60:1090-7. [PMID: 24700589 PMCID: PMC4141907 DOI: 10.1002/hep.27088] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/19/2013] [Accepted: 02/13/2014] [Indexed: 12/11/2022]
Abstract
Transhepatic solute transport provides the osmotic driving force for canalicular bile formation. Choleretic and cholestatic agents affect bile formation, in part, by altering plasma membrane localizations of transporters involved in bile formation. These short-term dynamic changes in transporter location are highly regulated posttranslational events requiring various cellular signaling pathways. Interestingly, both choleretic and cholestatic agents activate the same intracellular signaling kinases, such as phosphoinositide-3-kinase (PI3K), protein kinase C (PKC), and mitogen-activated protein kinase (MAPK). An emerging theme is that choleretic and cholestatic effects may be mediated by different isoforms of these kinases. This is most evident for PKC-mediated regulation of plasma membrane localization of Na+-taurocholate cotransporting polypeptide (NTCP) and multidrug resistance-associated protein 2 (MRP2) by conventional PKCα (cPKCα), novel PKCδ (nPKCδ), nPKCε, and atypical PKCζ (aPKCζ). aPKCζ may mediate choleretic effects by inserting NTCP into the plasma membrane, and nPKCε may mediate cholestatic effects by retrieving MRP2 from the plasma membrane. On the other hand, cPKCα and nPKCδ may be involved in choleretic, cholestatic, and anticholestatic effects by inserting, retrieving, and inhibiting retrieval of transporters, respectively. The effects of PKC isoforms may be mediated by phosphorylation of the transporters, actin binding proteins (radixin and myristoylated alanine-rich C kinase substrate), and Rab proteins. Human NTCP plays an important role in the entry of hepatitis B and D viruses into hepatocytes and consequent infection. Thus, PKCs, by regulating NTCP trafficking, may also play an important role in hepatic viral infections.
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Affiliation(s)
- M Sawkat Anwer
- Department of Biomedical Sciences, Cummings School of Veterinary Medicine at Tufts University, North Grafton, MA
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204
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Messenger SW, Falkowski MA, Thomas DDH, Jones EK, Hong W, Gaisano HY, Giasano HY, Boulis NM, Groblewski GE. Vesicle associated membrane protein 8 (VAMP8)-mediated zymogen granule exocytosis is dependent on endosomal trafficking via the constitutive-like secretory pathway. J Biol Chem 2014; 289:28040-53. [PMID: 25138214 DOI: 10.1074/jbc.m114.593913] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Acinar cell zymogen granules (ZG) express 2 isoforms of the vesicle-associated membrane protein family (VAMP2 and -8) thought to regulate exocytosis. Expression of tetanus toxin to cleave VAMP2 in VAMP8 knock-out (-/-) acini confirmed that VAMP2 and -8 are the primary VAMPs for regulated exocytosis, each contributing ∼50% of the response. Analysis of VAMP8(-/-) acini indicated that although stimulated secretion was significantly reduced, a compensatory increase in constitutive secretion maintained total secretion equivalent to wild type (WT). Using a perifusion system to follow secretion over time revealed VAMP2 mediates an early rapid phase peaking and falling within 2-3 min, whereas VAMP8 controls a second prolonged phase that peaks at 4 min and slowly declines over 20 min to support the protracted secretory response. VAMP8(-/-) acini show increased expression of the endosomal proteins Ti-VAMP7 (2-fold) and Rab11a (4-fold) and their redistribution from endosomes to ZGs. Expression of GDP-trapped Rab11a-S25N inhibited secretion exclusively from the VAMP8 but not the VAMP2 pathway. VAMP8(-/-) acini also showed a >90% decrease in the early endosomal proteins Rab5/D52/EEA1, which control anterograde trafficking in the constitutive-like secretory pathway. In WT acini, short term (14-16 h) culture also results in a >90% decrease in Rab5/D52/EEA1 and a complete loss of the VAMP8 pathway, whereas VAMP2-secretion remains intact. Remarkably, rescue of Rab5/D52/EEA1 expression restored the VAMP8 pathway. Expressed D52 shows extensive colocalization with Rab11a and VAMP8 and partially copurifies with ZG fractions. These results indicate that robust trafficking within the constitutive-like secretory pathway is required for VAMP8- but not VAMP2-mediated ZG exocytosis.
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Affiliation(s)
- Scott W Messenger
- From the Department of Nutritional Sciences, University of Wisconsin, Madison, Wisconsin 53706
| | - Michelle A Falkowski
- From the Department of Nutritional Sciences, University of Wisconsin, Madison, Wisconsin 53706
| | - Diana D H Thomas
- From the Department of Nutritional Sciences, University of Wisconsin, Madison, Wisconsin 53706
| | - Elaina K Jones
- From the Department of Nutritional Sciences, University of Wisconsin, Madison, Wisconsin 53706
| | - Wanjin Hong
- Institute of Molecular and Cellular Biology, National University of Singapore, Singapore 138673
| | | | - Herbert Y Giasano
- Departments of Medicine and Physiology, University of Toronto, Ontario M5S 1A8, Canada, and
| | - Nicholas M Boulis
- Department of Neurosurgery, Georgia Institute of Technology, Atlanta, Georgia 30322
| | - Guy E Groblewski
- From the Department of Nutritional Sciences, University of Wisconsin, Madison, Wisconsin 53706,
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205
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Eaton S, Martin-Belmonte F. Cargo sorting in the endocytic pathway: a key regulator of cell polarity and tissue dynamics. Cold Spring Harb Perspect Biol 2014; 6:a016899. [PMID: 25125399 DOI: 10.1101/cshperspect.a016899] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
The establishment and maintenance of polarized plasma membrane domains is essential for cellular function and proper development of organisms. Epithelial cells polarize along two fundamental axes, the apicobasal and the planar, both depending on finely regulated protein trafficking mechanisms. Newly synthesized proteins destined for either surface domain are processed along the biosynthetic pathway and segregated into distinct subsets of transport carriers emanating from the trans-Golgi network or endosomes. This exocytic trafficking has been identified as essential for proper epithelial polarization. Accumulating evidence now reveals that endocytosis and endocytic recycling play an equally important role in epithelial polarization and the appropriate localization of key polarity proteins. Here, we review recent work in metazoan systems illuminating the connections between endocytosis, postendocytic trafficking, and cell polarity, both apicobasal and planar, in the formation of differentiated epithelial cells, and how these processes regulate tissue dynamics.
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Affiliation(s)
- Suzanne Eaton
- Max Planck Institute of Molecular Cell Biology and Genetics, 01307 Dresden, Germany
| | - Fernando Martin-Belmonte
- Centro de Biología Molecular Severo Ochoa, Consejo Superior de Investigaciones Científicas (CSIC), Madrid 28049, Spain
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206
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Abstract
The endocytic network comprises a vast and intricate system of membrane-delimited cell entry and cargo sorting routes running between biochemically and functionally distinct intracellular compartments. The endocytic network caters to the organization and redistribution of diverse subcellular components, and mediates appropriate shuttling and processing of materials acquired from neighboring cells or the extracellular milieu. Such trafficking logistics, despite their importance, represent only one facet of endocytic function. The endocytic network also plays a key role in organizing, mediating, and regulating cellular signal transduction events. Conversely, cellular signaling processes tightly control the endocytic pathway at different steps. The present article provides a perspective on the intimate relationships that exist between particular endocytic and cellular signaling processes in mammalian cells, within the context of understanding the impact of this nexus on integrated physiology.
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Affiliation(s)
- Pier Paolo Di Fiore
- Department of Experimental Oncology, Istituto Europeo di Oncologia, 20141 Milan, Italy Dipartimento di Scienze della Salute, Università degli Studi di Milano, 20122 Milan, Italy
| | - Mark von Zastrow
- Department of Psychiatry, University of California San Francisco School of Medicine, San Francisco, California 94158 Department of Cellular & Molecular Pharmacology, University of California San Francisco School of Medicine, San Francisco, California 94158
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207
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Nakatsukasa K, Kanada A, Matsuzaki M, Byrne SD, Okumura F, Kamura T. The nutrient stress-induced small GTPase Rab5 contributes to the activation of vesicle trafficking and vacuolar activity. J Biol Chem 2014; 289:20970-8. [PMID: 24923442 DOI: 10.1074/jbc.m114.548297] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Rab family small GTPases regulate membrane trafficking by spatiotemporal recruitment of various effectors. However, it remains largely unclear how the expression and functions of Rab proteins are regulated in response to extracellular or intracellular stimuli. Here we show that Ypt53, one isoform of Rab5 in Saccharomyces cerevisiae, is up-regulated significantly under nutrient stress. Under non-stress conditions, Vps21, a constitutively expressed Rab5 isoform, is crucial to Golgi-vacuole trafficking and to vacuolar hydrolase activity. However, when cells are exposed to nutrient stress for an extended period of time, the up-regulated Ypt53 and the constitutive Vps21 function redundantly to maintain these activities, which, in turn, prevent the accumulation of reactive oxygen species and maintain mitochondrial respiration. Together, our results clarify the relative roles of these constitutive and nutrient stress-inducible Rab5 proteins that ensure adaptable vesicle trafficking and vacuolar hydrolase activity, thereby allowing cells to adapt to environmental changes.
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208
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Medina MW, Bauzon F, Naidoo D, Theusch E, Stevens K, Schilde J, Schubert C, Mangravite LM, Rudel LL, Temel RE, Runz H, Krauss RM. Transmembrane protein 55B is a novel regulator of cellular cholesterol metabolism. Arterioscler Thromb Vasc Biol 2014; 34:1917-23. [PMID: 25035345 DOI: 10.1161/atvbaha.113.302806] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
OBJECTIVE Interindividual variation in pathways affecting cellular cholesterol metabolism can influence levels of plasma cholesterol, a well-established risk factor for cardiovascular disease. Inherent variation among immortalized lymphoblastoid cell lines from different donors can be leveraged to discover novel genes that modulate cellular cholesterol metabolism. The objective of this study was to identify novel genes that regulate cholesterol metabolism by testing for evidence of correlated gene expression with cellular levels of 3-hydroxy-3-methylglutaryl-CoA reductase (HMGCR) mRNA, a marker for cellular cholesterol homeostasis, in a large panel of lymphoblastoid cell lines. APPROACH AND RESULTS Expression array profiling was performed on 480 lymphoblastoid cell lines established from participants of the Cholesterol and Pharmacogenetics (CAP) statin clinical trial, and transcripts were tested for evidence of correlated expression with HMGCR as a marker of intracellular cholesterol homeostasis. Of these, transmembrane protein 55b (TMEM55B) showed the strongest correlation (r=0.29; P=4.0E-08) of all genes not previously implicated in cholesterol metabolism and was found to be sterol regulated. TMEM55B knockdown in human hepatoma cell lines promoted the decay rate of the low-density lipoprotein receptor, reduced cell surface low-density lipoprotein receptor protein, impaired low-density lipoprotein uptake, and reduced intracellular cholesterol. CONCLUSIONS Here, we report identification of TMEM55B as a novel regulator of cellular cholesterol metabolism through the combination of gene expression profiling and functional studies. The findings highlight the value of an integrated genomic approach for identifying genes that influence cholesterol homeostasis.
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Affiliation(s)
- Marisa W Medina
- From the Children's Hospital Oakland Research Institute, CA (M.W.M., F.B., D.N., E.T., K.S., R.M.K.); Institute of Human Genetics, University of Heidelberg, Heidelberg, Germany (J.S., H.R.); Sage Bionetworks, Seattle, WA (L.M.M.); Section on Lipid Sciences, Department of Pathology, Wake Forest University Health Sciences, Winston-Salem, NC (L.L.R., R.E.T.); and Molecular Medicine Partnership Unit (MMPU), Heidelberg, Germany (C.S., H.R.).
| | - Frederick Bauzon
- From the Children's Hospital Oakland Research Institute, CA (M.W.M., F.B., D.N., E.T., K.S., R.M.K.); Institute of Human Genetics, University of Heidelberg, Heidelberg, Germany (J.S., H.R.); Sage Bionetworks, Seattle, WA (L.M.M.); Section on Lipid Sciences, Department of Pathology, Wake Forest University Health Sciences, Winston-Salem, NC (L.L.R., R.E.T.); and Molecular Medicine Partnership Unit (MMPU), Heidelberg, Germany (C.S., H.R.)
| | - Devesh Naidoo
- From the Children's Hospital Oakland Research Institute, CA (M.W.M., F.B., D.N., E.T., K.S., R.M.K.); Institute of Human Genetics, University of Heidelberg, Heidelberg, Germany (J.S., H.R.); Sage Bionetworks, Seattle, WA (L.M.M.); Section on Lipid Sciences, Department of Pathology, Wake Forest University Health Sciences, Winston-Salem, NC (L.L.R., R.E.T.); and Molecular Medicine Partnership Unit (MMPU), Heidelberg, Germany (C.S., H.R.)
| | - Elizabeth Theusch
- From the Children's Hospital Oakland Research Institute, CA (M.W.M., F.B., D.N., E.T., K.S., R.M.K.); Institute of Human Genetics, University of Heidelberg, Heidelberg, Germany (J.S., H.R.); Sage Bionetworks, Seattle, WA (L.M.M.); Section on Lipid Sciences, Department of Pathology, Wake Forest University Health Sciences, Winston-Salem, NC (L.L.R., R.E.T.); and Molecular Medicine Partnership Unit (MMPU), Heidelberg, Germany (C.S., H.R.)
| | - Kristen Stevens
- From the Children's Hospital Oakland Research Institute, CA (M.W.M., F.B., D.N., E.T., K.S., R.M.K.); Institute of Human Genetics, University of Heidelberg, Heidelberg, Germany (J.S., H.R.); Sage Bionetworks, Seattle, WA (L.M.M.); Section on Lipid Sciences, Department of Pathology, Wake Forest University Health Sciences, Winston-Salem, NC (L.L.R., R.E.T.); and Molecular Medicine Partnership Unit (MMPU), Heidelberg, Germany (C.S., H.R.)
| | - Jessica Schilde
- From the Children's Hospital Oakland Research Institute, CA (M.W.M., F.B., D.N., E.T., K.S., R.M.K.); Institute of Human Genetics, University of Heidelberg, Heidelberg, Germany (J.S., H.R.); Sage Bionetworks, Seattle, WA (L.M.M.); Section on Lipid Sciences, Department of Pathology, Wake Forest University Health Sciences, Winston-Salem, NC (L.L.R., R.E.T.); and Molecular Medicine Partnership Unit (MMPU), Heidelberg, Germany (C.S., H.R.)
| | - Christian Schubert
- From the Children's Hospital Oakland Research Institute, CA (M.W.M., F.B., D.N., E.T., K.S., R.M.K.); Institute of Human Genetics, University of Heidelberg, Heidelberg, Germany (J.S., H.R.); Sage Bionetworks, Seattle, WA (L.M.M.); Section on Lipid Sciences, Department of Pathology, Wake Forest University Health Sciences, Winston-Salem, NC (L.L.R., R.E.T.); and Molecular Medicine Partnership Unit (MMPU), Heidelberg, Germany (C.S., H.R.)
| | - Lara M Mangravite
- From the Children's Hospital Oakland Research Institute, CA (M.W.M., F.B., D.N., E.T., K.S., R.M.K.); Institute of Human Genetics, University of Heidelberg, Heidelberg, Germany (J.S., H.R.); Sage Bionetworks, Seattle, WA (L.M.M.); Section on Lipid Sciences, Department of Pathology, Wake Forest University Health Sciences, Winston-Salem, NC (L.L.R., R.E.T.); and Molecular Medicine Partnership Unit (MMPU), Heidelberg, Germany (C.S., H.R.)
| | - Lawrence L Rudel
- From the Children's Hospital Oakland Research Institute, CA (M.W.M., F.B., D.N., E.T., K.S., R.M.K.); Institute of Human Genetics, University of Heidelberg, Heidelberg, Germany (J.S., H.R.); Sage Bionetworks, Seattle, WA (L.M.M.); Section on Lipid Sciences, Department of Pathology, Wake Forest University Health Sciences, Winston-Salem, NC (L.L.R., R.E.T.); and Molecular Medicine Partnership Unit (MMPU), Heidelberg, Germany (C.S., H.R.)
| | - Ryan E Temel
- From the Children's Hospital Oakland Research Institute, CA (M.W.M., F.B., D.N., E.T., K.S., R.M.K.); Institute of Human Genetics, University of Heidelberg, Heidelberg, Germany (J.S., H.R.); Sage Bionetworks, Seattle, WA (L.M.M.); Section on Lipid Sciences, Department of Pathology, Wake Forest University Health Sciences, Winston-Salem, NC (L.L.R., R.E.T.); and Molecular Medicine Partnership Unit (MMPU), Heidelberg, Germany (C.S., H.R.)
| | - Heiko Runz
- From the Children's Hospital Oakland Research Institute, CA (M.W.M., F.B., D.N., E.T., K.S., R.M.K.); Institute of Human Genetics, University of Heidelberg, Heidelberg, Germany (J.S., H.R.); Sage Bionetworks, Seattle, WA (L.M.M.); Section on Lipid Sciences, Department of Pathology, Wake Forest University Health Sciences, Winston-Salem, NC (L.L.R., R.E.T.); and Molecular Medicine Partnership Unit (MMPU), Heidelberg, Germany (C.S., H.R.)
| | - Ronald M Krauss
- From the Children's Hospital Oakland Research Institute, CA (M.W.M., F.B., D.N., E.T., K.S., R.M.K.); Institute of Human Genetics, University of Heidelberg, Heidelberg, Germany (J.S., H.R.); Sage Bionetworks, Seattle, WA (L.M.M.); Section on Lipid Sciences, Department of Pathology, Wake Forest University Health Sciences, Winston-Salem, NC (L.L.R., R.E.T.); and Molecular Medicine Partnership Unit (MMPU), Heidelberg, Germany (C.S., H.R.)
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209
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Ruda VM, Chandwani R, Sehgal A, Bogorad RL, Akinc A, Charisse K, Tarakhovsky A, Novobrantseva TI, Koteliansky V. The roles of individual mammalian argonautes in RNA interference in vivo. PLoS One 2014; 9:e101749. [PMID: 24992693 PMCID: PMC4081796 DOI: 10.1371/journal.pone.0101749] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2013] [Accepted: 05/28/2014] [Indexed: 11/26/2022] Open
Abstract
Argonaute 2 (Ago2) is the only mammalian Ago protein capable of mRNA cleavage. It has been reported that the activity of the short interfering RNA targeting coding sequence (CDS), but not 3′ untranslated region (3′UTR) of an mRNA, is solely dependent on Ago2 in vitro. These studies utilized extremely high doses of siRNAs and overexpressed Ago proteins, as well as were directed at various highly expressed reporter transgenes. Here we report the effect of Ago2 in vivo on targeted knockdown of several endogenous genes by siRNAs, targeting both CDS and 3′UTR. We show that siRNAs targeting CDS lose their activity in the absence of Ago2, whereas both Ago1 and Ago3 proteins contribute to residual 3′UTR-targeted siRNA-mediated knockdown observed in the absence of Ago2 in mouse liver. Our results provide mechanistic insight into two components mediating RNAi under physiological conditions: mRNA cleavage dependent and independent. In addition our results contribute a novel consideration for designing most efficacious siRNA molecules with the preference given to 3′UTR targeting as to harness the activity of several Ago proteins.
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Affiliation(s)
- Vera M. Ruda
- Koch Institute for Integrative Cancer Research, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States of America
- * E-mail: (VMR); (VK)
| | - Rohit Chandwani
- Laboratory of Immune Cell Epigenetics and Signaling, Rockefeller University, New York, New York, United States of America
| | - Alfica Sehgal
- Alnylam Pharmaceuticals, Cambridge, Massachusetts, United States of America
| | - Roman L. Bogorad
- Koch Institute for Integrative Cancer Research, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States of America
| | - Akin Akinc
- Alnylam Pharmaceuticals, Cambridge, Massachusetts, United States of America
| | - Klaus Charisse
- Alnylam Pharmaceuticals, Cambridge, Massachusetts, United States of America
| | - Alexander Tarakhovsky
- Laboratory of Immune Cell Epigenetics and Signaling, Rockefeller University, New York, New York, United States of America
| | | | - Victor Koteliansky
- Koch Institute for Integrative Cancer Research, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States of America
- * E-mail: (VMR); (VK)
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210
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Recent developments in in vitro toxicology: perspectives of European research and Tox21. Arch Toxicol 2014; 87:2043-6. [PMID: 24221536 DOI: 10.1007/s00204-013-1164-8] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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211
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212
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Zhang Z, Zhang T, Wang S, Gong Z, Tang C, Chen J, Ding J. Molecular mechanism for Rabex-5 GEF activation by Rabaptin-5. eLife 2014; 3. [PMID: 24957337 PMCID: PMC4102244 DOI: 10.7554/elife.02687] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2014] [Accepted: 06/20/2014] [Indexed: 01/30/2023] Open
Abstract
Rabex-5 and Rabaptin-5 function together to activate Rab5 and further promote early endosomal fusion in endocytosis. The Rabex-5 GEF activity is autoinhibited by the Rabex-5 CC domain (Rabex-5CC) and activated by the Rabaptin-5 C2-1 domain (Rabaptin-5C21) with yet unknown mechanism. We report here the crystal structures of Rabex-5 in complex with the dimeric Rabaptin-5C21 (Rabaptin-5C212) and in complex with Rabaptin-5C212 and Rab5, along with biophysical and biochemical analyses. We show that Rabex-5CC assumes an amphipathic α-helix which binds weakly to the substrate-binding site of the GEF domain, leading to weak autoinhibition of the GEF activity. Binding of Rabaptin-5C21 to Rabex-5 displaces Rabex-5CC to yield a largely exposed substrate-binding site, leading to release of the GEF activity. In the ternary complex the substrate-binding site of Rabex-5 is completely exposed to bind and activate Rab5. Our results reveal the molecular mechanism for the regulation of the Rabex-5 GEF activity. DOI:http://dx.doi.org/10.7554/eLife.02687.001 Cells need to allow various molecules to pass through the plasma membrane on their surface. Some molecules have to enter the cell, whereas others have to leave. Cells rely on a process called endocytosis to move large molecules into the cell. This involves part of the membrane engulfing the molecule to form a ‘bubble’ around it. This bubble, which is called an endosome, then moves the molecule to final destination inside the cell. A protein called Rab5 controls how a new endosome is produced. However, before this can happen, various other molecules—including two proteins called Rabex-5 and Rabaptin-5—must activate the Rab5 protein. Exactly how these three proteins interact with each other was unknown. Zhang et al. used X-ray crystallography to examine the structures of the complexes formed when Rabex-5 and Rabaptin-5 bind to each other, both when Rab5 is present, and also when it is absent. Biochemical and biophysical experiments confirmed that the Rabex-5/Rabaptin-5 complex is able to activate Rab5. Zhang et al. also found that Rabex-5, on its own, folds so that the site that normally binds to Rab5 instead binds to a different part of Rabex-5, thus preventing endocytosis. However, when Rabaptin-5 forms a complex with Rabex-5, the Rab5 binding site is freed up. The Rabex-5/Rabaptin-5 complex can switch between a V shape and a linear structure. Binding to Rab5 stabilizes the linear form of the complex, which then helps activate Rab5, and subsequently the activated Rab5 can interact with other downstream molecules, triggering endocytosis. DOI:http://dx.doi.org/10.7554/eLife.02687.002
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Affiliation(s)
- Zhe Zhang
- State Key Laboratory of Molecular Biology, Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai, China
| | - Tianlong Zhang
- State Key Laboratory of Molecular Biology, Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai, China
| | - Shanshan Wang
- State Key Laboratory of Molecular Biology, Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai, China
| | - Zhou Gong
- State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan, China
| | - Chun Tang
- State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan, China
| | - Jiangye Chen
- State Key Laboratory of Molecular Biology, Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai, China
| | - Jianping Ding
- State Key Laboratory of Molecular Biology, Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai, China
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213
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Li Y, Low LH, Putz U, Goh CP, Tan SS, Howitt J. Rab5 and Ndfip1 are involved in Pten ubiquitination and nuclear trafficking. Traffic 2014; 15:749-61. [PMID: 24798731 DOI: 10.1111/tra.12175] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2013] [Revised: 04/29/2014] [Accepted: 04/29/2014] [Indexed: 12/18/2022]
Abstract
The spatial regulation of Pten is critical for its role as a tumour suppressor with both nuclear and cytoplasmic locations being implicated with distinct functions. In the cytoplasm, Pten plays a central role in opposing PI3K/Akt cell signalling, whereas in the nucleus, Pten is important for maintaining genome stability and enhancing the tumour suppressor activity of APC-CDH1. Despite this diversity in protein function at different subcellular locations, there is limited knowledge on how Pten is able to find different cellular niches. Here, we report that Rab5 GTPase is required for efficient trafficking and ubiquitination of Pten on endosomes inside the cytosol. Using bimolecular fluorescence complementation (BiFC) for imaging protein interactions, we observed that ubiquitinated Pten is localized to peri-nuclear and nuclear regions of the cell. Nuclear trafficking of Pten required both Rab5 as well as the E3 ligase adaptor protein Ndfip1. Rab5 colocalization with Pten was observed on endosomes and expression of a dominant negative form of Rab5 significantly reduced Pten ubiquitination and nuclear trafficking. Genomic deletion of Ndfip1 abrogated nuclear trafficking of ubiquitinated Pten, even in the presence of Rab5. Our findings show that endosomal trafficking and ubiquitination are important mechanisms for the subcellular distribution of Pten.
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Affiliation(s)
- Yijia Li
- Brain Development and Regeneration Division, Florey Institute of Neuroscience and Mental Health, The University of Melbourne, Parkville, Victoria, 3010, Australia
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214
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Abstract
Live-cell imaging reveals the endolysosomal system as a complex and highly dynamic network of interacting compartments. Distinct types of endosomes are discerned by kinetic, molecular, and morphological criteria. Although none of these criteria, or combinations thereof, can capture the full complexity of the endolysosomal system, they are extremely useful for experimental purposes. Some membrane domain specializations and specific morphological characteristics can only be seen by ultrastructural analysis after preparation for electron microscopy (EM). Immuno-EM allows a further discrimination of seemingly identical compartments by their molecular makeup. In this review we provide an overview of the ultrastructural characteristics and membrane organization of endosomal compartments, along with their organizing machineries.
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Affiliation(s)
- Judith Klumperman
- Department of Cell Biology, University Medical Center Utrecht, Heidelberglaan 100, 3584 CX Utrecht, The Netherlands
| | - Graça Raposo
- Institut Curie, Centre de Recherche, Paris F-75248, France Structure and Membrane Compartments CNRS UMR144, Paris F-75248, France
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215
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Speicher T, Siegenthaler B, Bogorad RL, Ruppert R, Petzold T, Padrissa-Altes S, Bachofner M, Anderson DG, Koteliansky V, Fässler R, Werner S. Knockdown and knockout of β1-integrin in hepatocytes impairs liver regeneration through inhibition of growth factor signalling. Nat Commun 2014; 5:3862. [PMID: 24844558 DOI: 10.1038/ncomms4862] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2013] [Accepted: 04/11/2014] [Indexed: 02/06/2023] Open
Abstract
The liver has a unique regenerative capability, which involves extensive remodelling of cell-cell and cell-matrix contacts. Here we study the role of integrins in mouse liver regeneration using Cre/loxP-mediated gene deletion or intravenous delivery of β1-integrin siRNA formulated into nanoparticles that predominantly target hepatocytes. We show that although short-term loss of β1-integrin has no obvious consequences for normal livers, partial hepatectomy leads to severe liver necrosis and reduced hepatocyte proliferation. Mechanistically, loss of β1-integrin in hepatocytes impairs ligand-induced phosphorylation of the epidermal growth factor and hepatocyte growth factor receptors, thereby attenuating downstream receptor signalling in vitro and in vivo. These results identify a crucial role and novel mechanism of action of β1-integrins in liver regeneration and demonstrate that protein depletion by nanoparticle-based delivery of specific siRNA is a powerful strategy to study gene function in the regenerating liver.
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Affiliation(s)
- Tobias Speicher
- Department of Biology, Institute of Molecular Health Sciences, ETH Zurich,8093, Switzerland
| | - Beat Siegenthaler
- Department of Biology, Institute of Molecular Health Sciences, ETH Zurich,8093, Switzerland
| | - Roman L Bogorad
- David H. Koch Institute for Integrative Cancer Research, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | - Raphael Ruppert
- Department of Molecular Medicine, Max-Planck-Institute of Biochemistry, 82152 Martinsried, Germany
| | - Tobias Petzold
- Department of Molecular Medicine, Max-Planck-Institute of Biochemistry, 82152 Martinsried, Germany
| | - Susagna Padrissa-Altes
- Department of Biology, Institute of Molecular Health Sciences, ETH Zurich,8093, Switzerland
| | - Marc Bachofner
- Department of Biology, Institute of Molecular Health Sciences, ETH Zurich,8093, Switzerland
| | - Daniel G Anderson
- 1] David H. Koch Institute for Integrative Cancer Research, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA [2] Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA [3] Division of Health Science Technology, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | - Victor Koteliansky
- Skolkovo Institute of Science and Technology, ul. Novaya, d.100, Skolkovo 143025, Russian Federation
| | - Reinhard Fässler
- Department of Molecular Medicine, Max-Planck-Institute of Biochemistry, 82152 Martinsried, Germany
| | - Sabine Werner
- Department of Biology, Institute of Molecular Health Sciences, ETH Zurich,8093, Switzerland
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216
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Nanoparticle-formulated siRNA targeting integrins inhibits hepatocellular carcinoma progression in mice. Nat Commun 2014; 5:3869. [PMID: 24844798 PMCID: PMC4107318 DOI: 10.1038/ncomms4869] [Citation(s) in RCA: 68] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2013] [Accepted: 04/11/2014] [Indexed: 02/07/2023] Open
Abstract
Integrins play an important role during development, regulating cell differentiation, proliferation and survival. Here we show that knockdown of integrin subunits slows down the progression of hepatocellular carcinoma (HCC). Using nanoparticulate delivery of short interfering RNAs targeting β1 and αv integrin subunits we downregulate all integrin receptors in hepatocytes. Short-term integrin knockdown (two weeks) does not cause apparent structural or functional perturbations of normal liver tissue. Alterations in liver morphology accumulate upon sustained integrin downregulation (seven weeks). The integrin knockdown leads to significant retardation of HCC progression, reducing proliferation and increasing tumour cell death. This tumour retardation is accompanied by reduced activation of MET oncogene as well as expression of its mature form on the cell surface. Our data suggest that transformed proliferating cells from HCC are more sensitive to knockdown of integrins than normal quiescent hepatocytes, highlighting the potential of siRNA-mediated inhibition of integrins as an anti-cancer therapeutic approach.
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217
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Dimopoulos S, Mayer CE, Rudolf F, Stelling J. Accurate cell segmentation in microscopy images using membrane patterns. Bioinformatics 2014; 30:2644-51. [DOI: 10.1093/bioinformatics/btu302] [Citation(s) in RCA: 103] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
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218
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Rodriguez-Boulan E, Macara IG. Organization and execution of the epithelial polarity programme. Nat Rev Mol Cell Biol 2014; 15:225-42. [PMID: 24651541 DOI: 10.1038/nrm3775] [Citation(s) in RCA: 503] [Impact Index Per Article: 50.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Epithelial cells require apical-basal plasma membrane polarity to carry out crucial vectorial transport functions and cytoplasmic polarity to generate different cell progenies for tissue morphogenesis. The establishment and maintenance of a polarized epithelial cell with apical, basolateral and ciliary surface domains is guided by an epithelial polarity programme (EPP) that is controlled by a network of protein and lipid regulators. The EPP is organized in response to extracellular cues and is executed through the establishment of an apical-basal axis, intercellular junctions, epithelial-specific cytoskeletal rearrangements and a polarized trafficking machinery. Recent studies have provided insight into the interactions of the EPP with the polarized trafficking machinery and how these regulate epithelial polarization and depolarization.
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Affiliation(s)
- Enrique Rodriguez-Boulan
- Margaret Dyson Vision Research Institute, Weill Cornell Medical College, 1300 York Avenue, LC-301 New York City, New York 10065, USA
| | - Ian G Macara
- Department of Cell & Developmental Biology, Vanderbilt University Medical Center, 465 21st Avenue South, U 3209 MRB III, Nashville Tennessee 37232, USA
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219
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Steinberg G. Endocytosis and early endosome motility in filamentous fungi. Curr Opin Microbiol 2014; 20:10-8. [PMID: 24835422 PMCID: PMC4148197 DOI: 10.1016/j.mib.2014.04.001] [Citation(s) in RCA: 68] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2014] [Accepted: 04/21/2014] [Indexed: 10/25/2022]
Abstract
Hyphal growth of filamentous fungi requires microtubule-based long-distance motility of early endosomes. Since the discovery of this process in Ustilago maydis, our understanding of its molecular basis and biological function has greatly advanced. Studies in U. maydis and Aspergillus nidulans reveal a complex interplay of the motor proteins kinesin-3 and dynein, which co-operate to support bi-directional motion of early endosomes. Genetic screening has shed light on the molecular mechanisms underpinning motor regulation, revealing Hook protein as general motor adapters on early endosomes. Recently, fascinating insight into unexpected roles for endosome motility has emerged. This includes septin filament formation and cellular distribution of the machinery for protein translation.
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Affiliation(s)
- Gero Steinberg
- Biosciences, University of Exeter, Stocker Road, Exeter EX4 4QD, UK.
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220
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Auffarth K, Arlt H, Lachmann J, Cabrera M, Ungermann C. Tracking of the dynamic localization of the Rab-specific HOPS subunits reveal their distinct interaction with Ypt7 and vacuoles. CELLULAR LOGISTICS 2014; 4:e29191. [PMID: 25210650 PMCID: PMC4156483 DOI: 10.4161/cl.29191] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/03/2014] [Revised: 04/29/2014] [Accepted: 05/09/2014] [Indexed: 12/19/2022]
Abstract
Endosomal and vacuole fusion depends on the two homologous tethering complexes CORVET and HOPS. HOPS binds the activated Rab GTPase Ypt7 via two distinct subunits, Vps39 and Vps41. To understand the participation and possible polarity of Vps41 and Vps39 during tethering, we used an in vivo approach. For this, we established the ligand-induced relocalization to the plasma membrane, using the Mon1-Ccz1 GEF complex that activates Ypt7 on endosomes. We then employed slight overexpression to compare the mobility of the HOPS-specific Vps41 and Vps39 subunits during this process. Our data indicate an asymmetry in the Rab-specific interaction of the two HOPS subunits: Vps39 is more tightly bound to the vacuole, and relocalizes the entire vacuole to the plasma membrane, whereas Vps41 behaved like the more mobile subunit. This is due to their specific Rab binding, as the mobility of both subunits was similar in ypt7∆ cells. In contrast, both HOPS subunits were far less mobile if tagged endogenously, suggesting that the entire HOPS complex is tightly bound to the vacuole in vivo. Similar results were obtained for the endosomal association of CORVET, when we followed its Rab-specific subunit Vps8. Our data provide in vivo evidence for distinct Rab specificity within HOPS, which may explain its function during tethering, and indicate that these tethering complexes are less mobile within the cell than previously anticipated.
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Affiliation(s)
- Kathrin Auffarth
- Biochemistry section; Department of Biology/Chemistry; University of Osnabrück; Osnabrück, Germany
| | - Henning Arlt
- Biochemistry section; Department of Biology/Chemistry; University of Osnabrück; Osnabrück, Germany
| | - Jens Lachmann
- Biochemistry section; Department of Biology/Chemistry; University of Osnabrück; Osnabrück, Germany
| | - Margarita Cabrera
- Biochemistry section; Department of Biology/Chemistry; University of Osnabrück; Osnabrück, Germany
| | - Christian Ungermann
- Biochemistry section; Department of Biology/Chemistry; University of Osnabrück; Osnabrück, Germany
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221
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Qin Y, Deng Y, Ricketts C, Srikantan S, Wang E, Maher E, Dahia PL. The tumor susceptibility gene TMEM127 is mutated in renal cell carcinomas and modulates endolysosomal function. Hum Mol Genet 2014; 23:2428-39. [PMID: 24334765 PMCID: PMC3976335 DOI: 10.1093/hmg/ddt638] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2013] [Revised: 12/10/2013] [Accepted: 12/10/2013] [Indexed: 11/13/2022] Open
Abstract
TMEM127 is an endosome-associated tumor suppressor gene in pheochromocytomas, neuroendocrine tumors that can co-occur with renal cell carcinomas (RCCs). TMEM127 loss leads to increased mTOR signaling. However, the spectrum of tumors with TMEM127 mutation and how TMEM127 and mTOR interact in tumorigenesis remains unknown. Here, we report that germline TMEM127 mutations occur in RCCs and that some mutant proteins, unlike wild-type (WT) TMEM127, fail to cooperate with activated early endosomal GTPase, Rab5, to inhibit mTOR signaling. Tmem127-null mouse embryonic fibroblasts (MEFs) are deficient in generating early-to-late hybrid endosomes upon constitutive Rab5 activation, a defect rescued by WT, but not mutant, TMEM127. This endosomal dysfunction results in diminished mTOR colocalization with Rab5-positive vesicles. Conversely, active, lysosomal-bound mTOR is increased in Tmem127-null MEFs, which also display enhanced lysosomal biogenesis. Our data map the tumor-suppressive properties of TMEM127 to modulation of mTOR function in the endolysosome, a feature that may contribute to both pheochromocytoma and RCC pathogenesis.
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Affiliation(s)
| | - Y. Deng
- Department of Medicine
- Department of Cellular & Structural Biology and
| | - C.J. Ricketts
- Medical and Molecular Genetics, School of Clinical and Experimental Medicine, College of Medical and Dental Sciences and Centre for Rare Diseases and Personalized Medicine, University of Birmingham, Birmingham, UK
| | | | - E. Wang
- Department of Cellular & Structural Biology and
| | - E.R. Maher
- Medical and Molecular Genetics, School of Clinical and Experimental Medicine, College of Medical and Dental Sciences and Centre for Rare Diseases and Personalized Medicine, University of Birmingham, Birmingham, UK
| | - P. L.M. Dahia
- Department of Medicine
- Cancer Therapy and Research Center (CTRC)
- Greehey Children's Cancer Research Institute (GCCRI), University of Texas Health Science Center at San Antonio, San Antonio, TX, USA
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222
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Higuchi Y, Ashwin P, Roger Y, Steinberg G. Early endosome motility spatially organizes polysome distribution. ACTA ACUST UNITED AC 2014; 204:343-57. [PMID: 24493587 PMCID: PMC3912533 DOI: 10.1083/jcb.201307164] [Citation(s) in RCA: 100] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
To distribute the protein translation machinery throughout the cytoplasm, polysomes in the fungus Ustilago maydis associate with mobile early endosomes, resulting in long-range motility along microtubules. Early endosomes (EEs) mediate protein sorting, and their cytoskeleton-dependent motility supports long-distance signaling in neurons. Here, we report an unexpected role of EE motility in distributing the translation machinery in a fungal model system. We visualize ribosomal subunit proteins and show that the large subunits diffused slowly throughout the cytoplasm (Dc,60S = 0.311 µm2/s), whereas entire polysomes underwent long-range motility along microtubules. This movement was mediated by “hitchhiking” on kinesin-3 and dynein-driven EEs, where the polysomes appeared to translate EE-associated mRNA into proteins. Modeling indicates that this motor-driven transport is required for even cellular distribution of newly formed ribosomes. Indeed, impaired EE motility in motor mutants, or their inability to bind EEs in mutants lacking the RNA-binding protein Rrm4, reduced ribosome transport and induced ribosome aggregation near the nucleus. As a consequence, cell growth was severely restricted. Collectively, our results indicate that polysomes associate with moving EEs and that “off- and reloading” distributes the protein translation machinery.
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Affiliation(s)
- Yujiro Higuchi
- Biosciences and 2 Mathematics Research Institute, University of Exeter, Exeter EX4 4QD, England, UK
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223
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Azouz NP, Zur N, Efergan A, Ohbayashi N, Fukuda M, Amihai D, Hammel I, Rothenberg ME, Sagi-Eisenberg R. Rab5 Is a Novel Regulator of Mast Cell Secretory Granules: Impact on Size, Cargo, and Exocytosis. THE JOURNAL OF IMMUNOLOGY 2014; 192:4043-53. [DOI: 10.4049/jimmunol.1302196] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
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224
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Santiago FW, Covaleda LM, Sanchez-Aparicio MT, Silvas JA, Diaz-Vizarreta AC, Patel JR, Popov V, Yu XJ, García-Sastre A, Aguilar PV. Hijacking of RIG-I signaling proteins into virus-induced cytoplasmic structures correlates with the inhibition of type I interferon responses. J Virol 2014; 88:4572-85. [PMID: 24478431 PMCID: PMC3993744 DOI: 10.1128/jvi.03021-13] [Citation(s) in RCA: 94] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2013] [Accepted: 01/20/2014] [Indexed: 12/23/2022] Open
Abstract
UNLABELLED Recognition of viral pathogens by the retinoic acid-inducible gene I (RIG-I)-like receptor (RLR) family results in the activation of type I interferon (IFN) responses. To avoid this response, most viruses have evolved strategies that target different essential steps in the activation of host innate immunity. In this study, we report that the nonstructural protein NSs of the newly described severe fever with thrombocytopenia syndrome virus (SFTSV) is a potent inhibitor of IFN responses. The SFTSV NSs protein was found to inhibit the activation of the beta interferon (IFN-β) promoter induced by viral infection and by a RIG-I ligand. Astonishingly, we found that SFTSV NSs interacts with and relocalizes RIG-I, the E3 ubiquitin ligase TRIM25, and TANK-binding kinase 1 (TBK1) into SFTSV NSs-induced cytoplasmic structures. Interestingly, formation of these SFTSV NSs-induced structures occurred in the absence of the Atg7 gene, a gene essential for autophagy. Furthermore, confocal microscopy studies revealed that these SFTSV NSs-induced structures colocalize with Rab5 but not with Golgi apparatus or endoplasmic reticulum markers. Altogether, the data suggest that sequestration of RIG-I signaling molecules into endosome-like structures may be the mechanism used by SFTSV to inhibit IFN responses and point toward a novel mechanism for the suppression of IFN responses. IMPORTANCE The mechanism by which the newly described SFTSV inhibits host antiviral responses has not yet been fully characterized. In this study, we describe the redistribution of RIG-I signaling components into virus-induced cytoplasmic structures in cells infected with SFTSV. This redistribution correlates with the inhibition of host antiviral responses. Further characterization of the interplay between the viral protein and components of the IFN responses could potentially provide targets for the rational development of therapeutic interventions.
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Affiliation(s)
- Felix W. Santiago
- Department of Pathology, University of Texas Medical Branch, Galveston, Texas, USA
| | - Lina M. Covaleda
- Department of Pathology, University of Texas Medical Branch, Galveston, Texas, USA
| | - Maria T. Sanchez-Aparicio
- Department of Microbiology, Icahn School of Medicine at Mount Sinai, New York, New York, USA
- Global Health and Emerging Pathogens Institute, Icahn School of Medicine at Mount Sinai, New York, New York, USA
| | - Jesus A. Silvas
- Department of Pathology, University of Texas Medical Branch, Galveston, Texas, USA
| | | | - Jenish R. Patel
- Department of Microbiology, Icahn School of Medicine at Mount Sinai, New York, New York, USA
- Global Health and Emerging Pathogens Institute, Icahn School of Medicine at Mount Sinai, New York, New York, USA
- Graduate School of Biomedical Sciences, Icahn School of Medicine at Mount Sinai, New York, New York, USA
| | - Vsevolod Popov
- Department of Pathology, University of Texas Medical Branch, Galveston, Texas, USA
- Institute for Human Infection and Immunity, University of Texas Medical Branch, Galveston, Texas, USA
| | - Xue-jie Yu
- Department of Pathology, University of Texas Medical Branch, Galveston, Texas, USA
| | - Adolfo García-Sastre
- Department of Microbiology, Icahn School of Medicine at Mount Sinai, New York, New York, USA
- Global Health and Emerging Pathogens Institute, Icahn School of Medicine at Mount Sinai, New York, New York, USA
- Department of Medicine, Division of Infectious Diseases, Icahn School of Medicine at Mount Sinai, New York, New York, USA
| | - Patricia V. Aguilar
- Department of Pathology, University of Texas Medical Branch, Galveston, Texas, USA
- Institute for Human Infection and Immunity, University of Texas Medical Branch, Galveston, Texas, USA
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225
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Weigert R. Imaging the dynamics of endocytosis in live mammalian tissues. Cold Spring Harb Perspect Biol 2014; 6:a017012. [PMID: 24691962 DOI: 10.1101/cshperspect.a017012] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
In mammalian cells, endocytosis plays a pivotal role in regulating several basic cellular functions. Up to now, the dynamics and the organization of the endocytic pathways have been primarily investigated in reductionist model systems such as cell and organ cultures. Although these experimental models have been fully successful in unraveling the endocytic machinery at a molecular level, our understanding of the regulation and the role of endocytosis in vivo has been limited. Recently, advancements in intravital microscopy have made it possible to extend imaging in live animals to subcellular structures, thus revealing new aspects of the molecular machineries regulating membrane trafficking that were not previously appreciated in vitro. Here, we focus on the use of intravital microscopy to study endocytosis in vivo, and discuss how this approach will allow addressing two fundamental questions: (1) how endocytic processes are organized in mammalian tissues, and (2) how they contribute to organ physiopathology.
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Affiliation(s)
- Roberto Weigert
- Intracellular Membrane Trafficking Unit, Oral and Pharyngeal Cancer Branch, National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, Maryland 20892-4340
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226
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Kiss RS, Nilsson T. Rab proteins implicated in lipid storage and mobilization. J Biomed Res 2014; 28:169-77. [PMID: 25013400 PMCID: PMC4085554 DOI: 10.7555/jbr.28.20140029] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2014] [Accepted: 02/28/2014] [Indexed: 12/28/2022] Open
Abstract
Abnormal intracellular accumulation or transport of lipids contributes greatly to the pathogenesis of human diseases. In the liver, excess accumulation of triacylglycerol (TG) leads to fatty liver disease encompassing steatosis, steatohepatitis and fibrosis. This places individuals at risk of developing cirrhosis, hepatocellular carcinoma or hepatic decompensation and also contributes to the emergence of insulin resistance and dyslipidemias affecting many other organs. Excessive accumulation of TG in adipose tissue contributes to insulin resistance as well as to the release of cytokines attracting leucocytes leading to a pro-inflammatory state. Pathological accumulation of cholesteryl ester (CE) in macrophages in the arterial wall is the progenitor of atherosclerotic plaques and heart disease. Overconsumption of dietary fat, cholesterol and carbohydrates explains why these diseases are on the increase yet offers few clues for how to prevent or treat individuals. Dietary regimes have proven futile and barring surgery, no realistic alternatives are at hand as effective drugs are few and not without side effects. Overweight and obesity-related diseases are no longer restricted to the developed world and as such, constitute a global problem. Development of new drugs and treatment strategies are a priority yet requires as a first step, elucidation of the molecular pathophysiology underlying each associated disease state. The lipid droplet (LD), an up to now overlooked intracellular organelle, appears at the heart of each pathophysiology linking key regulatory and metabolic processes as well as constituting the site of storage of both TGs and CEs. As the molecular machinery and mechanisms of LDs of each cell type are being elucidated, regulatory proteins used to control various cellular processes are emerging. Of these and the subject of this review, small GTPases belonging to the Rab protein family appear as important molecular switches used in the regulation of the intracellular trafficking and storage of lipids.
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Affiliation(s)
- Robert Scott Kiss
- Department of Medicine, McGill University, Montreal, Canada; ; Research Institute of McGill University Health Centre, Montreal, Canada
| | - Tommy Nilsson
- Department of Medicine, McGill University, Montreal, Canada; ; Research Institute of McGill University Health Centre, Montreal, Canada
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227
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Sahini N, Borlak J. Recent insights into the molecular pathophysiology of lipid droplet formation in hepatocytes. Prog Lipid Res 2014; 54:86-112. [PMID: 24607340 DOI: 10.1016/j.plipres.2014.02.002] [Citation(s) in RCA: 77] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2013] [Revised: 02/17/2014] [Accepted: 02/21/2014] [Indexed: 12/11/2022]
Abstract
Triacyglycerols are a major energy reserve of the body and are normally stored in adipose tissue as lipid droplets (LDs). The liver, however, stores energy as glycogen and digested triglycerides in the form of fatty acids. In stressed condition such as obesity, imbalanced nutrition and drug induced liver injury hepatocytes accumulate excess lipids in the form of LDs whose prolonged storage leads to disease conditions most notably non-alcoholic fatty liver disease (NAFLD). Fatty liver disease has become a major health burden with more than 90% of obese, nearly 70% of overweight and about 25% of normal weight patients being affected. Notably, research in recent years has shown LD as highly dynamic organelles for maintaining lipid homeostasis through fat storage, protein sorting and other molecular events studied in adipocytes and other cells of living organisms. This review focuses on the molecular events of LD formation in hepatocytes and the importance of cross talk between different cell types and their signalling in NAFLD as to provide a perspective on molecular mechanisms as well as possibilities for different therapeutic intervention strategies.
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Affiliation(s)
- Nishika Sahini
- Centre for Pharmacology and Toxicology, Hannover Medical School, 30625 Hannover, Germany
| | - Jürgen Borlak
- Centre for Pharmacology and Toxicology, Hannover Medical School, 30625 Hannover, Germany.
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228
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Spencer NY, Engelhardt JF. The basic biology of redoxosomes in cytokine-mediated signal transduction and implications for disease-specific therapies. Biochemistry 2014; 53:1551-64. [PMID: 24555469 PMCID: PMC3985689 DOI: 10.1021/bi401719r] [Citation(s) in RCA: 62] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
![]()
Redox
reactions have been established as major biological players
in many cellular signaling pathways. Here we review mechanisms of
redox signaling with an emphasis on redox-active signaling endosomes.
Signals are transduced by relatively few reactive oxygen species (ROS),
through very specific redox modifications of numerous proteins and
enzymes. Although ROS signals are typically associated with cellular
injury, these signaling pathways are also critical for maintaining
cellular health at homeostasis. An important component of ROS signaling
pertains to localization and tightly regulated signal transduction
events within discrete microenvironments of the cell. One major aspect
of this specificity is ROS compartmentalization within membrane-enclosed
organelles such as redoxosomes (redox-active endosomes) and the nuclear
envelope. Among the cellular proteins that produce superoxide are
the NADPH oxidases (NOXes), transmembrane proteins that are implicated
in many types of redox signaling. NOXes produce superoxide on only
one side of a lipid bilayer; as such, their orientation dictates the
compartmentalization of ROS and the local control of signaling events
limited by ROS diffusion and/or movement through channels associated
with the signaling membrane. NOX-dependent ROS signaling pathways
can also be self-regulating, with molecular redox sensors that limit
the local production of ROS required for effective signaling. ROS
regulation of the Rac-GTPase, a required co-activator of many NOXes,
is an example of this type of sensor. A deeper understanding of redox
signaling pathways and the mechanisms that control their specificity
will provide unique therapeutic opportunities for aging, cancer, ischemia-reperfusion
injury, and neurodegenerative diseases.
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Affiliation(s)
- Netanya Y Spencer
- Department of Anatomy and Cell Biology, The University of Iowa , Iowa City, Iowa 52242-1009, United States
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229
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Abstract
The elongation rate of axons is tightly regulated during development. Recycling of the plasma membrane is known to regulate axon extension; however, the specific molecules involved in recycling within the growth cone have not been fully characterized. Here, we investigated whether the small GTPases Rab4 and Rab5 involved in short-loop recycling regulate the extension of Xenopus retinal axons. We report that, in growth cones, Rab5 and Rab4 proteins localize to endosomes, which accumulate markers that are constitutively recycled. Fluorescence recovery after photo-bleaching experiments showed that Rab5 and Rab4 are recruited to endosomes in the growth cone, suggesting that they control recycling locally. Dynamic image analysis revealed that Rab4-positive carriers can bud off from Rab5 endosomes and move to the periphery of the growth cone, suggesting that both Rab5 and Rab4 contribute to recycling within the growth cone. Inhibition of Rab4 function with dominant-negative Rab4 or Rab4 morpholino and constitutive activation of Rab5 decreases the elongation of retinal axons in vitro and in vivo, but, unexpectedly, does not disrupt axon pathfinding. Thus, Rab5- and Rab4-mediated control of endosome trafficking appears to be crucial for axon growth. Collectively, our results suggest that recycling from Rab5-positive endosomes via Rab4 occurs within the growth cone and thereby supports axon elongation.
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230
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Gautreau A, Oguievetskaia K, Ungermann C. Function and regulation of the endosomal fusion and fission machineries. Cold Spring Harb Perspect Biol 2014; 6:6/3/a016832. [PMID: 24591520 DOI: 10.1101/cshperspect.a016832] [Citation(s) in RCA: 87] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
Organelles within the endomembrane system are connected via vesicle flux. Along the endocytic pathway, endosomes are among the most versatile organelles. They sort cargo through tubular protrusions for recycling or through intraluminal vesicles for degradation. Sorting involves numerous machineries, which mediate fission of endosomal transport intermediates and fusion with other endosomes or eventually with lysosomes. Here we review the recent advances in our understanding of these processes with a particular focus on the Rab GTPases, tethering factors, and retromer. The cytoskeleton has also been recently recognized as a central player in membrane dynamics of endosomes, and this review covers the regulation of the machineries that govern the formation of branched actin networks through the WASH and Arp2/3 complexes in relation with cargo recycling and endosomal fission.
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Affiliation(s)
- Alexis Gautreau
- Laboratoire d'Enzymologie et Biochimie Structurales, CNRS UPR3082, 91190 Gif-sur-Yvette, France
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231
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Chen PI, Schauer K, Kong C, Harding AR, Goud B, Stahl PD. Rab5 isoforms orchestrate a "division of labor" in the endocytic network; Rab5C modulates Rac-mediated cell motility. PLoS One 2014; 9:e90384. [PMID: 24587345 PMCID: PMC3938722 DOI: 10.1371/journal.pone.0090384] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2013] [Accepted: 01/29/2014] [Indexed: 11/30/2022] Open
Abstract
Rab5, the prototypical Rab GTPase and master regulator of the endocytic pathway, is encoded as three differentially expressed isoforms, Rab5A, Rab5B and Rab5C. Here, we examined the differential effects of Rab5 isoform silencing on cell motility and report that Rab5C, but neither Rab5A nor Rab5B, is selectively associated with the growth factor-activation of Rac1 and with enhanced cell motility. Initial observations revealed that silencing of Rab5C expression, but neither Rab5A nor Rab5C, led to spindle-shaped cells that displayed reduced formation of membrane ruffles. When subjected to a scratch wound assay, cells depleted of Rab5C, but not Rab5A or Rab5B, demonstrated reduced cell migration. U937 cells depleted of Rab5C also displayed reduced cell motility in a Transwell plate migration assay. To examine activation of Rac, HeLa cells stably expressing GFP-Rac1 were independently depleted of Rab5A, Rab5B or Rab5C and seeded onto coverslips imprinted with a crossbow pattern. 3-D GFP-Rac1 images of micro-patterned cells show that GFP-Rac1 was less localized to the cell periphery in the absence of Rab5C. To confirm the connection between Rab5C and Rac activation, HeLa cells depleted of Rab5 isoforms were starved and then stimulated with EGF. Rac1 pull-down assays revealed that EGF-stimulated Rac1 activity was significantly suppressed in Rab5C-suppressed cells. To determine whether events upstream of Rac activation were affected by Rab5C, we observed that EGF-stimulated Akt phosphorylation was suppressed in cells depleted of Rab5C. Finally, since spatio-temporal assembly/disassembly of adhesion complexes are essential components of cell migration, we examined the effect of Rab5 isoform depletion on the formation of focal adhesion complexes. Rab5C-depleted HeLa cells have significantly fewer focal adhesion foci, in accordance with the lack of persistent lamellipodial protrusions and reduced directional migration. We conclude that Rab5 isoforms selectively oversee the multiple signaling and trafficking events associated with the endocytic network.
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Affiliation(s)
- Pin-I Chen
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, Missouri, United States of America
| | - Kristine Schauer
- Molecular Mechanisms of Intracellular Transport, Institut Curie, Paris, France
| | - Chen Kong
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, Missouri, United States of America
| | - Andrew R. Harding
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, Missouri, United States of America
| | - Bruno Goud
- Molecular Mechanisms of Intracellular Transport, Institut Curie, Paris, France
| | - Philip D. Stahl
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, Missouri, United States of America
- * E-mail:
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232
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Escudero CA, Lazo OM, Galleguillos C, Parraguez JI, Lopez-Verrilli MA, Cabeza C, Leon L, Saeed U, Retamal C, Gonzalez A, Marzolo MP, Carter BD, Court FA, Bronfman FC. The p75 neurotrophin receptor evades the endolysosomal route in neuronal cells, favouring multivesicular bodies specialised for exosomal release. J Cell Sci 2014; 127:1966-79. [PMID: 24569882 DOI: 10.1242/jcs.141754] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
The p75 neurotrophin receptor (p75, also known as NGFR) is a multifaceted signalling receptor that regulates neuronal physiology, including neurite outgrowth, and survival and death decisions. A key cellular aspect regulating neurotrophin signalling is the intracellular trafficking of their receptors; however, the post-endocytic trafficking of p75 is poorly defined. We used sympathetic neurons and rat PC12 cells to study the mechanism of internalisation and post-endocytic trafficking of p75. We found that p75 internalisation depended on the clathrin adaptor protein AP2 and on dynamin. More surprisingly, p75 evaded the lysosomal route at the level of the early endosome, instead accumulating in two different types of endosomes, Rab11-positive endosomes and multivesicular bodies (MVBs) positive for CD63, a marker of the exosomal pathway. Consistently, depolarisation by KCl induced the liberation of previously endocytosed full-length p75 into the extracellular medium in exosomes. Thus, p75 defines a subpopulation of MVBs that does not mature to lysosomes and is available for exosomal release by neuronal cells.
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Affiliation(s)
- Claudia A Escudero
- Faculty of Biological Sciences, Physiology Department, Pontificia Universidad Católica, Santiago, CP 8331010, Chile
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233
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Rotaviruses reach late endosomes and require the cation-dependent mannose-6-phosphate receptor and the activity of cathepsin proteases to enter the cell. J Virol 2014; 88:4389-402. [PMID: 24501398 DOI: 10.1128/jvi.03457-13] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
UNLABELLED Rotaviruses (RVs) enter cells through different endocytic pathways. Bovine rotavirus (BRV) UK uses clathrin-mediated endocytosis, while rhesus rotavirus (RRV) employs an endocytic process independent of clathrin and caveolin. Given the differences in the cell internalization pathway used by these viruses, we tested if the intracellular trafficking of BRV UK was the same as that of RRV, which is known to reach maturing endosomes (MEs) to infect the cell. We found that BRV UK also reaches MEs, since its infectivity depends on the function of Rab5, the endosomal sorting complex required for transport (ESCRT), and the formation of endosomal intraluminal vesicles (ILVs). However, unlike RRV, the infectivity of BRV UK was inhibited by knocking down the expression of Rab7, indicating that it has to traffic to late endosomes (LEs) to infect the cell. The requirement for Rab7 was also shared by other RV strains of human and porcine origin. Of interest, most RV strains that reach LEs were also found to depend on the activities of Rab9, the cation-dependent mannose-6-phosphate receptor (CD-M6PR), and cathepsins B, L, and S, suggesting that cellular factors from the trans-Golgi network (TGN) need to be transported by the CD-M6PR to LEs to facilitate RV cell infection. Furthermore, using a collection of UK × RRV reassortant viruses, we found that the dependence of BRV UK on Rab7, Rab9, and CD-M6PR is associated with the spike protein VP4. These findings illustrate the elaborate pathway of RV entry and reveal a new process (Rab9/CD-M6PR/cathepsins) that could be targeted for drug intervention. IMPORTANCE Rotavirus is an important etiological agent of severe gastroenteritis in children. In most instances, viruses enter cells through an endocytic pathway that delivers the viral particle to vesicular organelles known as early endosomes (EEs). Some viruses reach the cytoplasm from EEs, where they start to replicate their genome. However, other viruses go deeper into the cell, trafficking from EEs to late endosomes (LEs) to disassemble and reach the cytoplasm. In this work, we show that most RV strains have to traffic to LEs, and the transport of endolysosomal proteases from the Golgi complex to LEs, mediated by the mannose-6-phosphate receptor, is necessary for the virus to exit the vesicular compartment and efficiently start viral replication. We also show that this deep journey into the cell is associated with the virus spike protein VP4. These findings illustrate the elaborate pathway of RV entry that could be used for drug intervention.
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234
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Ezougou CN, Ben-Rached F, Moss DK, Lin JW, Black S, Knuepfer E, Green JL, Khan SM, Mukhopadhyay A, Janse CJ, Coppens I, Yera H, Holder AA, Langsley G. Plasmodium falciparum Rab5B is an N-terminally myristoylated Rab GTPase that is targeted to the parasite's plasma and food vacuole membranes. PLoS One 2014; 9:e87695. [PMID: 24498355 PMCID: PMC3912013 DOI: 10.1371/journal.pone.0087695] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2013] [Accepted: 12/28/2013] [Indexed: 12/21/2022] Open
Abstract
Plasmodium falciparum (Pf) has a family of 11 Rab GTPases to regulate its vesicular transport. However, PfRab5B is unique in lacking a C-terminal geranyl-geranylation motif, while having N-terminal palmitoylation and myristoylation motifs. We show that the N-terminal glycine is required for PfRab5B myristoylation in vitro and when an N-terminal PfRab5B fragment possessing both acylation motifs is fused to GFP and expressed in transgenic P. falciparum parasites, the chimeric PfRab5B protein localizes to the plasma membrane. Upon substitution of the modified glycine by alanine the staining becomes diffuse and GFP is found in soluble subcellular fractions. Immuno-electron microscopy shows endogenous PfRab5B decorating the parasite's plasma and food vacuole membranes. Using reverse genetics rab5b couldn't be deleted from the haploid genome of asexual blood stage P. berghei parasites. The failure of PbRab5A or PbRab5C to complement for loss of PbRab5B function indicates non-overlapping roles for the three Plasmodium Rab5s, with PfRab5B involved in trafficking MSP1 to the food vacuole membrane and CK1 to the plasma membrane. We discuss similarities between Plasmodium Rab5B and Arabidopsis thaliana ARA6, a similarly unusual Rab5-like GTPase of plants.
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Affiliation(s)
- Carinne Ndjembo Ezougou
- Laboratoire de Biologie Cellulaire Comparative des Apicomplexes, Département d'Immunologie, Inflammation et Infection, Faculté de Médicine, Université Paris Descartes - Sorbonne Paris Cité, Paris, France
- Institut National de Recherche Médicale U1016, Centre National Recherche Scientifique UMR8104, Cochin Institute, Paris, France
| | - Fathia Ben-Rached
- Laboratoire de Biologie Cellulaire Comparative des Apicomplexes, Département d'Immunologie, Inflammation et Infection, Faculté de Médicine, Université Paris Descartes - Sorbonne Paris Cité, Paris, France
- Institut National de Recherche Médicale U1016, Centre National Recherche Scientifique UMR8104, Cochin Institute, Paris, France
| | - David K. Moss
- Division of Parasitology, MRC National Institute for Medical Research, Mill Hill, London, United Kingdom
| | - Jing-wen Lin
- Parasitology, Center of Infectious Diseases, Leiden University Medical Center, Leiden, The Netherlands
- Division of Parasitology, MRC National Institute for Medical Research, Mill Hill, London, United Kingdom
| | - Sally Black
- Division of Parasitology, MRC National Institute for Medical Research, Mill Hill, London, United Kingdom
| | - Ellen Knuepfer
- Division of Parasitology, MRC National Institute for Medical Research, Mill Hill, London, United Kingdom
| | - Judith L. Green
- Division of Parasitology, MRC National Institute for Medical Research, Mill Hill, London, United Kingdom
| | - Shahid M. Khan
- Parasitology, Center of Infectious Diseases, Leiden University Medical Center, Leiden, The Netherlands
| | | | - Chris J. Janse
- Parasitology, Center of Infectious Diseases, Leiden University Medical Center, Leiden, The Netherlands
| | - Isabelle Coppens
- Department of Molecular Microbiology and Immunology, Johns Hopkins University Bloomberg School of Public Health, Baltimore, Maryland, United States of America
| | - Hélène Yera
- Laboratoire de Biologie Cellulaire Comparative des Apicomplexes, Département d'Immunologie, Inflammation et Infection, Faculté de Médicine, Université Paris Descartes - Sorbonne Paris Cité, Paris, France
- Institut National de Recherche Médicale U1016, Centre National Recherche Scientifique UMR8104, Cochin Institute, Paris, France
| | - Anthony A. Holder
- Division of Parasitology, MRC National Institute for Medical Research, Mill Hill, London, United Kingdom
| | - Gordon Langsley
- Laboratoire de Biologie Cellulaire Comparative des Apicomplexes, Département d'Immunologie, Inflammation et Infection, Faculté de Médicine, Université Paris Descartes - Sorbonne Paris Cité, Paris, France
- Institut National de Recherche Médicale U1016, Centre National Recherche Scientifique UMR8104, Cochin Institute, Paris, France
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235
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Abstract
Peroxisomes carry out various oxidative reactions that are tightly regulated to adapt to the changing needs of the cell and varying external environments. Accordingly, they are remarkably fluid and can change dramatically in abundance, size, shape and content in response to numerous cues. These dynamics are controlled by multiple aspects of peroxisome biogenesis that are coordinately regulated with each other and with other cellular processes. Ongoing studies are deciphering the diverse molecular mechanisms that underlie biogenesis and how they cooperate to dynamically control peroxisome utility. These important challenges should lead to an understanding of peroxisome dynamics that can be capitalized upon for bioengineering and the development of therapies to improve human health.
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Affiliation(s)
- Jennifer J Smith
- 1] Seattle Biomedical Research Institute, 307 Westlake Avenue North, 98109-5240, USA. [2] Institute for Systems Biology, 401 Terry Avenue North, Seattle, Washington 98109-5219, USA
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236
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Groen AJ, Sancho-Andrés G, Breckels LM, Gatto L, Aniento F, Lilley KS. Identification of trans-golgi network proteins in Arabidopsis thaliana root tissue. J Proteome Res 2014; 13:763-76. [PMID: 24344820 PMCID: PMC3929368 DOI: 10.1021/pr4008464] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/03/2022]
Abstract
![]()
Knowledge of protein
subcellular localization assists in the elucidation
of protein function and understanding of different biological mechanisms
that occur at discrete subcellular niches. Organelle-centric proteomics
enables localization of thousands of proteins simultaneously. Although
such techniques have successfully allowed organelle protein catalogues
to be achieved, they rely on the purification or significant enrichment
of the organelle of interest, which is not achievable for many organelles.
Incomplete separation of organelles leads to false discoveries, with
erroneous assignments. Proteomics methods that measure the distribution
patterns of specific organelle markers along density gradients are
able to assign proteins of unknown localization based on comigration
with known organelle markers, without the need for organelle purification.
These methods are greatly enhanced when coupled to sophisticated computational
tools. Here we apply and compare multiple approaches to establish
a high-confidence data set of Arabidopsis root tissue
trans-Golgi network (TGN) proteins. The method employed involves immunoisolations
of the TGN, coupled to probability-based organelle proteomics techniques.
Specifically, the technique known as LOPIT (localization of organelle
protein by isotope tagging), couples density centrifugation with quantitative
mass-spectometry-based proteomics using isobaric labeling and targeted
methods with semisupervised machine learning methods. We demonstrate
that while the immunoisolation method gives rise to a significant
data set, the approach is unable to distinguish cargo proteins and
persistent contaminants from full-time residents of the TGN. The LOPIT
approach, however, returns information about many subcellular niches
simultaneously and the steady-state location of proteins. Importantly,
therefore, it is able to dissect proteins present in more than one
organelle and cargo proteins en route to other cellular destinations
from proteins whose steady-state location favors the TGN. Using this
approach, we present a robust list of Arabidopsis TGN proteins.
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Affiliation(s)
- Arnoud J Groen
- Cambridge Centre for Proteomics, Cambridge Systems Biology Centre, Department of Biochemistry, University of Cambridge , 80 Tennis Court Road, Cambridge CB2 1GA, United Kingdom
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237
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Girard E, Chmiest D, Fournier N, Johannes L, Paul JL, Vedie B, Lamaze C. Rab7 is functionally required for selective cargo sorting at the early endosome. Traffic 2014; 15:309-26. [PMID: 24329906 DOI: 10.1111/tra.12143] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2013] [Revised: 12/04/2013] [Accepted: 12/10/2013] [Indexed: 12/26/2022]
Abstract
The small GTPases of the Rab family act as a molecular switch regulating various aspects of membrane trafficking through the selective recruitment of effector proteins. Whereas Rab7 has been classically involved in the regulation of transport within the endolysosomal network, persistent controversy remains as to whether Rab7 also plays a role in earlier steps of endosomal trafficking. In this study, we show that Rab7 depletion or inactivation results in enlargement of both early and late endosomes. Rab7 depletion led to the retention of a significant fraction of internalized low-density lipoproteins (LDL) mainly in enlarged early endosomes (EE). As a result, LDL processing and the transcriptional regulation of sterol-sensitive genes were impaired. We found that Rab7 activity was also required for the sorting of the mannose-6-phosphate receptor, the interferon alpha-receptor and the Shiga toxin B-subunit. In contrast, epidermal growth factor (EGF) sorting at the EE or the recycling of transferrin and LDL-R were not affected by Rab7 depletion. Our findings demonstrate that in addition to regulating late endosomes (LE) to lysosomes transport, Rab7 plays a functional role in the selective sorting of distinct cargos at the EE and that the Rab5 to Rab7 exchange occurs early in the endosomal maturation process.
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Affiliation(s)
- Emmanuelle Girard
- AP-HP (Assistance Publique - Hôpitaux de Paris), Hôpital Européen Georges Pompidou, Service de Biochimie, 75015, Paris, France; Université Paris-Sud, EA 4529, UFR de Pharmacie, 92296, Châtenay-Malabry, France; CNRS UMR144, 75248 Paris cedex 05, France; Institut Curie, Centre de Recherche, Laboratoire Trafic, Signalisation et Ciblage Intracellulaires, 75248, Paris Cedex 05, France
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238
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Jean-Alphonse F, Bowersox S, Chen S, Beard G, Puthenveedu MA, Hanyaloglu AC. Spatially restricted G protein-coupled receptor activity via divergent endocytic compartments. J Biol Chem 2013; 289:3960-77. [PMID: 24375413 PMCID: PMC3924264 DOI: 10.1074/jbc.m113.526350] [Citation(s) in RCA: 80] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Postendocytic sorting of G protein-coupled receptors (GPCRs) is driven by their interactions between highly diverse receptor sequence motifs with their interacting proteins, such as postsynaptic density protein (PSD95), Drosophila disc large tumor suppressor (Dlg1), zonula occludens-1 protein (zo-1) (PDZ) domain proteins. However, whether these diverse interactions provide an underlying functional specificity, in addition to driving sorting, is unknown. Here we identify GPCRs that recycle via distinct PDZ ligand/PDZ protein pairs that exploit their recycling machinery primarily for targeted endosomal localization and signaling specificity. The luteinizing hormone receptor (LHR) and β2-adrenergic receptor (B2AR), two GPCRs sorted to the regulated recycling pathway, underwent divergent trafficking to distinct endosomal compartments. Unlike B2AR, which traffics to early endosomes (EE), LHR internalizes to distinct pre-early endosomes (pre-EEs) for its recycling. Pre-EE localization required interactions of the LHR C-terminal tail with the PDZ protein GAIP-interacting protein C terminus, inhibiting its traffic to EEs. Rerouting the LHR to EEs, or EE-localized GPCRs to pre-EEs, spatially reprograms MAPK signaling. Furthermore, LHR-mediated activation of MAPK signaling requires internalization and is maintained upon loss of the EE compartment. We propose that combinatorial specificity between GPCR sorting sequences and interacting proteins dictates an unprecedented spatiotemporal control in GPCR signal activity.
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Affiliation(s)
- Frederic Jean-Alphonse
- From the Institute of Reproductive and Developmental Biology, Department of Surgery and Cancer, Imperial College London, London W12 0NN, United Kingdom and
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239
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Balderhaar HJK, Ungermann C. CORVET and HOPS tethering complexes - coordinators of endosome and lysosome fusion. J Cell Sci 2013; 126:1307-16. [PMID: 23645161 DOI: 10.1242/jcs.107805] [Citation(s) in RCA: 364] [Impact Index Per Article: 33.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Protein and lipid transport along the endolysosomal system of eukaryotic cells depends on multiple fusion and fission events. Over the past few years, the molecular constituents of both fission and fusion machineries have been identified. Here, we focus on the mechanism of membrane fusion at endosomes, vacuoles and lysosomes, and in particular on the role of the two homologous tethering complexes called CORVET and HOPS. Both complexes are heterohexamers; they share four subunits, interact with Rab GTPases and soluble NSF attachment protein receptors (SNAREs) and can tether membranes. Owing to the presence of specific subunits, CORVET is a Rab5 effector complex, whereas HOPS can bind efficiently to late endosomes and lysosomes through Rab7. Based on the recently described overall structure of the HOPS complex and a number of in vivo and in vitro analyses, important insights into their function have been obtained. Here, we discuss the general function of both complexes in yeast and in metazoan cells in the context of endosomal biogenesis and maturation.
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Affiliation(s)
- Henning J kleine Balderhaar
- University of Osnabrück, Department of Biology/Chemistry, Biochemistry Section, Barbarastrasse 13, 49076 Osnabrück, Germany
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240
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Nomachi A, Yoshinaga M, Liu J, Kanchanawong P, Tohyama K, Thumkeo D, Watanabe T, Narumiya S, Hirata T. Moesin controls clathrin-mediated S1PR1 internalization in T cells. PLoS One 2013; 8:e82590. [PMID: 24358210 PMCID: PMC3865155 DOI: 10.1371/journal.pone.0082590] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2012] [Accepted: 11/04/2013] [Indexed: 11/21/2022] Open
Abstract
The lipid mediator sphingosine 1-phosphate (S1P) regulates a wide range of cellular activities, including vascular maturation, angiogenesis, and immune-cell trafficking. Among the five known receptors for S1P (S1PR1-S1PR5), S1PR1 is a critical regulator of lymphocyte trafficking: its signaling is required for lymphocyte egress from lymphoid organs, while its down-modulation by agonist-induced internalization is a prerequisite for lymphocyte entry into lymphoid organs from the bloodstream. Despite the importance of S1PR1 down-regulation in determining lymphocyte behavior, the molecular mechanism of its internalization in lymphocytes has not been defined. Here we show that agonist-induced S1PR1 internalization in T cells occurs via clathrin-mediated endocytosis and is regulated by moesin, an ezrin-radixin-moesin (ERM) family member. In S1P-stimulated T cells, S1PR1 relocalized within clathrin-coated vesicles (CCVs) and early endosomes, and S1PR1 internalization was blocked when clathrin was pharmacologically inhibited. Stimulating moesin-deficient T cells with S1P failed to induce S1PR1 internalization and CCV formation. Furthermore, treating moesin-deficient mice with FTY720, an S1P receptor agonist known to internalize S1PR1, caused delayed lymphopenia, and lymphocytes isolated from FTY720-treated moesin-deficient mice still responded to S1P ex vivo in chemotaxis assays. These results reveal a novel role for moesin in regulating clathrin-dependent S1PR1 internalization through CCV formation.
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Affiliation(s)
- Akira Nomachi
- Center for Innovation in Immunoregulative Technology and Therapeutics, Kyoto University Graduate School of Medicine, Kyoto, Japan
| | - Masanori Yoshinaga
- Department of Pharmacology, Kyoto University Graduate School of Medicine, Kyoto, Japan
| | - Jaron Liu
- Mechanobiology Institute, Singapore, Singapore
| | - Pakorn Kanchanawong
- Mechanobiology Institute, Singapore, Singapore
- Department of Bioengineering, National University of Singapore, Singapore, Singapore
| | - Kiyoshi Tohyama
- Department of Pharmacology, Kyoto University Graduate School of Medicine, Kyoto, Japan
| | - Dean Thumkeo
- Department of Pharmacology, Kyoto University Graduate School of Medicine, Kyoto, Japan
| | - Takeshi Watanabe
- Center for Innovation in Immunoregulative Technology and Therapeutics, Kyoto University Graduate School of Medicine, Kyoto, Japan
| | - Shuh Narumiya
- Center for Innovation in Immunoregulative Technology and Therapeutics, Kyoto University Graduate School of Medicine, Kyoto, Japan
- Department of Pharmacology, Kyoto University Graduate School of Medicine, Kyoto, Japan
| | - Takako Hirata
- Department of Fundamental Biosciences, Shiga University of Medical Science, Otsu, Shiga, Japan
- * E-mail:
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241
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Akematsu T, Fukuda Y, Attiq R, Pearlman RE. Role of class III phosphatidylinositol 3-kinase during programmed nuclear death of Tetrahymena thermophila. Autophagy 2013; 10:209-25. [PMID: 24280724 PMCID: PMC5396089 DOI: 10.4161/auto.26929] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Programmed nuclear death (PND) in the ciliate protozoan Tetrahymena thermophila is a novel type of autophagy that occurs during conjugation, in which only the parental somatic macronucleus is destined to die and is then eliminated from the progeny cytoplasm. Other coexisting nuclei, however, such as new micro- and macronuclei are unaffected. PND starts with condensation in the nucleus followed by apoptotic DNA fragmentation, lysosomal acidification, and final resorption. Because of the peculiarity in the process and the absence of some ATG genes in this organism, the mechanism of PND has remained unclear. In this study, we focus on the role of class III phosphatidylinositol 3-kinase (PtdIns3K, corresponding to yeast Vps34) in order to identify central regulators of PND. We identified the sole Tetrahymena thermophila ortholog (TtVPS34) to yeast Vps34 and human PIK3C3 (the catalytic subunit of PtdIns3K), through phylogenetic analysis, and generated the gene knockdown mutant for functional analysis. Loss of TtVPS34 activity prevents autophagosome formation on the parental macronucleus, and this nucleus escapes from the lysosomal pathway. In turn, DNA fragmentation and final resorption of the nucleus are drastically impaired. These phenotypes are similar to the situation in the ATG8Δ mutants of Tetrahymena, implying an inextricable link between TtVPS34 and TtATG8s in controlling PND as well as general macroautophagy. On the other hand, TtVPS34 does not appear responsible for the nuclear condensation and does not affect the progeny nuclear development. These results demonstrate that TtVPS34 is critically involved in the nuclear degradation events of PND in autophagosome formation rather than with an involvement in commitment to the death program.
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Affiliation(s)
| | - Yasuhiro Fukuda
- Department of Biodiversity Science; Division of Biological Resource Science; Graduate School of Agricultural Science; Tohoku University, Oosaki, Japan
| | - Rizwan Attiq
- Department of Biology; York University; Toronto, CA
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242
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Palamidessi A, Frittoli E, Ducano N, Offenhauser N, Sigismund S, Kajiho H, Parazzoli D, Oldani A, Gobbi M, Serini G, Di Fiore PP, Scita G, Lanzetti L. The GTPase-activating protein RN-tre controls focal adhesion turnover and cell migration. Curr Biol 2013; 23:2355-64. [PMID: 24239119 DOI: 10.1016/j.cub.2013.09.060] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2012] [Revised: 09/02/2013] [Accepted: 09/30/2013] [Indexed: 10/26/2022]
Abstract
BACKGROUND Integrin-mediated adhesion of cells to the extracellular matrix (ECM) relies on the dynamic formation of focal adhesions (FAs), which are biochemical and mechanosensitive platforms composed of a large variety of cytosolic and transmembrane proteins. During migration, there is a constant turnover of ECM contacts that initially form as nascent adhesions at the leading edge, mature into FAs as actomyosin tension builds up, and are then disassembled at the cell rear, thus allowing for cell detachment. Although the mechanisms of FA assembly have largely been defined, the molecular circuitry that regulates their disassembly still remains elusive. RESULTS Here, we show that RN-tre, a GTPase-activating protein (GAP) for Rabs including Rab5 and Rab43, is a novel regulator of FA dynamics and cell migration. RN-tre localizes to FAs and to a pool of Rab5-positive vesicles mainly associated with FAs undergoing rapid remodeling. We found that RN-tre inhibits endocytosis of β1, but not β3, integrins and delays the turnover of FAs, ultimately impairing β1-dependent, but not β3-dependent, chemotactic cell migration. All of these effects are mediated by its GAP activity and rely on Rab5. CONCLUSIONS Our findings identify RN-tre as the Rab5-GAP that spatiotemporally controls FA remodeling during chemotactic cell migration.
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Affiliation(s)
- Andrea Palamidessi
- IFOM, Fondazione Istituto FIRC di Oncologia Molecolare, Via Adamello 16, 20139 Milano, Italy
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243
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Taniguchi Ishikawa E, Chang KH, Nayak R, Olsson HA, Ficker AM, Dunn SK, Madhu MN, Sengupta A, Whitsett JA, Grimes HL, Cancelas JA. Klf5 controls bone marrow homing of stem cells and progenitors through Rab5-mediated β1/β2-integrin trafficking. Nat Commun 2013; 4:1660. [PMID: 23552075 PMCID: PMC3627399 DOI: 10.1038/ncomms2645] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2012] [Accepted: 02/22/2013] [Indexed: 01/05/2023] Open
Abstract
Kruppel-like factor 5 (Klf5) regulates pluripotent stem cell self-renewal but its role in somatic stem cells is unknown. Here we show that Klf5 deficient haematopoietic stem cells and progenitors (HSC/P) fail to engraft after transplantation. This HSC/P defect is associated with impaired bone marrow homing and lodging and decreased retention in bone marrow, and with decreased adhesion to fibronectin and expression of membrane-bound β1/β2-integrins. In vivo inducible gain-of-function of Klf5 in HSCs increases HSC/P adhesion. The expression of Rab5 family members, mediators of β1/β2-integrin recycling in the early endosome, is decreased in Klf5Δ/Δ HSC/Ps. Klf5 binds directly to the promoter of Rab5a/b and overexpression of Rab5b rescues the expression of activated β1/β2-integrins, adhesion and bone marrow homing of Klf5Δ/Δ HSC/Ps. Altogether, these data indicate that Klf5 is indispensable for adhesion, homing, lodging and retention of HSC/Ps in the bone marrow through Rab5-dependent post-translational regulation of β1/β2 integrins.
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Affiliation(s)
- E Taniguchi Ishikawa
- Hoxworth Blood Center, University of Cincinnati College of Medicine, Cincinnati, Ohio 45267-0055, USA
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244
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Morgan JR, Comstra HS, Cohen M, Faundez V. Presynaptic membrane retrieval and endosome biology: defining molecularly heterogeneous synaptic vesicles. Cold Spring Harb Perspect Biol 2013; 5:a016915. [PMID: 24086045 DOI: 10.1101/cshperspect.a016915] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
The release and uptake of neurotransmitters by synaptic vesicles is a tightly controlled process that occurs in response to diverse stimuli at morphologically disparate synapses. To meet these architectural and functional synaptic demands, it follows that there should be diversity in the mechanisms that control their secretion and retrieval and possibly in the composition of synaptic vesicles within the same terminal. Here we pay particular attention to areas where such diversity is generated, such as the variance in exocytosis/endocytosis coupling, SNAREs defining functionally diverse synaptic vesicle populations and the adaptor-dependent sorting machineries capable of generating vesicle diversity. We argue that there are various synaptic vesicle recycling pathways at any given synapse and discuss several lines of evidence that support the role of the endosome in synaptic vesicle recycling.
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Affiliation(s)
- Jennifer R Morgan
- Eugene Bell Center for Regenerative Biology and Tissue Engineering, Marine Biological Laboratory, Woods Hole, Massachusetts 02543
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245
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Berg-Larsen A, Landsverk OJB, Progida C, Gregers TF, Bakke O. Differential regulation of Rab GTPase expression in monocyte-derived dendritic cells upon lipopolysaccharide activation: a correlation to maturation-dependent functional properties. PLoS One 2013; 8:e73538. [PMID: 24039975 PMCID: PMC3764041 DOI: 10.1371/journal.pone.0073538] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2013] [Accepted: 07/21/2013] [Indexed: 12/25/2022] Open
Abstract
The regulation of Rab expression to modulate cellular function has recently been proposed. Dendritic cells are a prototypic example of cells that drastically alter their function in response to environmental cues by reducing endocytosis, secreting cytokines, changing surface protein repertoires and altering morphology and migration. This is not a binary event, but is subject to fluctuations through the activation process, termed maturation. Consequently, DCs transiently increase endocytosis and production of major histocompatibility complex class II molecules, and secrete inflammatory cytokines in infected tissues before migrating to secondary lymph nodes and releasing T cell polarizing factors. All these cellular processes rely on intracellular membrane transport, which is regulated by Rab family GTPases and their diverse effectors. Here we examine how the Rabs likely to be involved in these functions are regulated throughout DC maturation. We find that Rab expression is altered upon lipopolysaccharide-induced activation, and discuss how this correlates to the reported functions of these cells during maturation.
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Affiliation(s)
- Axel Berg-Larsen
- Centre for Immune Regulation, Department of Biosciences, University of Oslo, Oslo, Norway
| | - Ole J. B. Landsverk
- Centre for Immune Regulation, Department of Biosciences, University of Oslo, Oslo, Norway
- * E-mail:
| | - Cinzia Progida
- Centre for Immune Regulation, Department of Biosciences, University of Oslo, Oslo, Norway
| | - Tone F. Gregers
- Centre for Immune Regulation, Department of Biosciences, University of Oslo, Oslo, Norway
| | - Oddmund Bakke
- Centre for Immune Regulation, Department of Biosciences, University of Oslo, Oslo, Norway
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246
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The virtual liver: possibilities to simulate mechanisms of toxicity and predict drug targets. Toxicol Lett 2013. [DOI: 10.1016/j.toxlet.2013.06.029] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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247
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Goodridge JP, Lee N, Burian A, Pyo CW, Tykodi SS, Warren EH, Yee C, Riddell SR, Geraghty DE. HLA-F and MHC-I open conformers cooperate in a MHC-I antigen cross-presentation pathway. THE JOURNAL OF IMMUNOLOGY 2013; 191:1567-77. [PMID: 23851683 DOI: 10.4049/jimmunol.1300080] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Peptides that are presented by MHC class I (MHC-I) are processed from two potential sources, as follows: newly synthesized endogenous proteins for direct presentation on the surface of most nucleated cells and exogenous proteins for cross-presentation typically by professional APCs. In this study, we present data that implicate the nonclassical HLA-F and open conformers of MHC-I expressed on activated cells in a pathway for the presentation of exogenous proteins by MHC-I. This pathway is distinguished from the conventional endogenous pathway by its independence from TAP and tapasin and its sensitivity to inhibitors of lysosomal enzymes, and further distinguished by its dependence on MHC-I allotype-specific epitope recognition for Ag uptake. Thus, our data from in vitro experiments collectively support a previously unrecognized model of Ag cross-presentation mediated by HLA-F and MHC-I open conformers on activated lymphocytes and monocytes, which may significantly contribute to the regulation of immune system functions and the immune defense.
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Affiliation(s)
- Jodie P Goodridge
- Clinical Research Division, Fred Hutchinson Cancer Research Center, Seattle, WA 98109, USA
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248
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Image-based analysis of lipid nanoparticle-mediated siRNA delivery, intracellular trafficking and endosomal escape. Nat Biotechnol 2013; 31:638-46. [PMID: 23792630 DOI: 10.1038/nbt.2612] [Citation(s) in RCA: 953] [Impact Index Per Article: 86.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2013] [Accepted: 05/13/2013] [Indexed: 01/22/2023]
Abstract
Delivery of short interfering RNAs (siRNAs) remains a key challenge in the development of RNA interference (RNAi) therapeutics. A better understanding of the mechanisms of siRNA cellular uptake, intracellular transport and endosomal release could critically contribute to the improvement of delivery methods. Here we monitored the uptake of lipid nanoparticles (LNPs) loaded with traceable siRNAs in different cell types in vitro and in mouse liver by quantitative fluorescence imaging and electron microscopy. We found that LNPs enter cells by both constitutive and inducible pathways in a cell type-specific manner using clathrin-mediated endocytosis as well as macropinocytosis. By directly detecting colloidal-gold particles conjugated to siRNAs, we estimated that escape of siRNAs from endosomes into the cytosol occurs at low efficiency (1-2%) and only during a limited window of time when the LNPs reside in a specific compartment sharing early and late endosomal characteristics. Our results provide insights into LNP-mediated siRNA delivery that can guide development of the next generation of delivery systems for RNAi therapeutics.
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249
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Signals from the lysosome: a control centre for cellular clearance and energy metabolism. Nat Rev Mol Cell Biol 2013; 14:283-96. [PMID: 23609508 DOI: 10.1038/nrm3565] [Citation(s) in RCA: 1142] [Impact Index Per Article: 103.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
For a long time, lysosomes were considered merely to be cellular 'incinerators' involved in the degradation and recycling of cellular waste. However, now there is compelling evidence indicating that lysosomes have a much broader function and that they are involved in fundamental processes such as secretion, plasma membrane repair, signalling and energy metabolism. Furthermore, the essential role of lysosomes in autophagic pathways puts these organelles at the crossroads of several cellular processes, with significant implications for health and disease. The identification of a master regulator, transcription factor EB (TFEB), that regulates lysosomal biogenesis and autophagy has revealed how the lysosome adapts to environmental cues, such as starvation, and targeting TFEB may provide a novel therapeutic strategy for modulating lysosomal function in human disease.
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250
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Shapira I, Lee A, Vora R, Budman DR. P53 mutations in triple negative breast cancer upregulate endosomal recycling of epidermal growth factor receptor (EGFR) increasing its oncogenic potency. Crit Rev Oncol Hematol 2013; 88:284-92. [PMID: 23755891 DOI: 10.1016/j.critrevonc.2013.05.003] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2012] [Revised: 04/03/2013] [Accepted: 05/02/2013] [Indexed: 01/03/2023] Open
Abstract
There is no available targeted therapy for triple-negative or its more aggressive subtype, basal-like breast cancer. Multiple therapeutic strategies based on translational knowledge have not improved the treatment options for triple negative patients. As understanding of molecular pathways that drive tumor development is rapidly increasing, it is imperative to adapt our treatment strategies to perturbations in molecular pathways driving the malignant process. Basal-like breast cancers over-express EGFR (without mutations or EGFR gene amplifications) and have p53 mutations. While EGFR drives the malignant behavior in triple negative breast cancer (TNBC), anti-EGFR therapies have fallen short of the expected results in clinical trials. Here we bring evidence that the less than optimal results of the anti-EGFR therapies may be explained in part by the increased potency of the EGFR signaling due to increased endosomal recycling. The functional connection between EGFR and endosomal trafficking in TNBC is mutant p53 found in the most aggressive forms of TNBC. Mutant p53 acquires oncogenic functions and binds p63 protein, a member of p53 family with tumor suppressor activities. In the absence of functional p63 there is an upregulation of endosomal recycling EGFR and integrin to the membrane with increased proinvasive abilities of cancer cells. Blocking endosomal trafficking combined with anti-EGFR treatments may result in better clinical outcomes in TNBC.
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Affiliation(s)
- Iuliana Shapira
- Monter Cancer Center, Don Monti Division of Oncology, Division of Hematology, Hofstra North Shore Long Island Jewish School of Medicine, United States.
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