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Chen PW, Luo R, Jian X, Randazzo PA. The Arf6 GTPase-activating proteins ARAP2 and ACAP1 define distinct endosomal compartments that regulate integrin α5β1 traffic. J Biol Chem 2014; 289:30237-30248. [PMID: 25225293 DOI: 10.1074/jbc.m114.596155] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Arf6 and the Arf6 GTPase-activating protein (GAP) ACAP1 are established regulators of integrin traffic important to cell adhesion and migration. However, the function of Arf6 with ACAP1 cannot explain the range of Arf6 effects on integrin-based structures. We propose that Arf6 has different functions determined, in part, by the associated Arf GAP. We tested this idea by comparing the Arf6 GAPs ARAP2 and ACAP1. We found that ARAP2 and ACAP1 had opposing effects on apparent integrin β1 internalization. ARAP2 knockdown slowed, whereas ACAP1 knockdown accelerated, integrin β1 internalization. Integrin β1 association with adaptor protein containing a pleckstrin homology (PH) domain, phosphotyrosine-binding (PTB) domain, and leucine zipper motif (APPL)-positive endosomes and EEA1-positive endosomes was affected by ARAP2 knockdown and depended on ARAP2 GAP activity. ARAP2 formed a complex with APPL1 and colocalized with Arf6 and APPL in a compartment distinct from the Arf6/ACAP1 tubular recycling endosome. In addition, although ACAP1 and ARAP2 each colocalized with Arf6, they did not colocalize with each other and had opposing effects on focal adhesions (FAs). ARAP2 overexpression promoted large FAs, but ACAP1 overexpression reduced FAs. Taken together, the data support a model in which Arf6 has at least two sites of opposing action defined by distinct Arf6 GAPs.
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Affiliation(s)
- Pei-Wen Chen
- Laboratory of Cellular and Molecular Biology, NCI, National Institutes of Health, Bethesda, Maryland 20892
| | - Ruibai Luo
- Laboratory of Cellular and Molecular Biology, NCI, National Institutes of Health, Bethesda, Maryland 20892
| | - Xiaoying Jian
- Laboratory of Cellular and Molecular Biology, NCI, National Institutes of Health, Bethesda, Maryland 20892
| | - Paul A Randazzo
- Laboratory of Cellular and Molecular Biology, NCI, National Institutes of Health, Bethesda, Maryland 20892.
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202
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Parks EE, Ceresa BP. Cell surface epidermal growth factor receptors increase Src and c-Cbl activity and receptor ubiquitylation. J Biol Chem 2014; 289:25537-45. [PMID: 25074934 PMCID: PMC4162159 DOI: 10.1074/jbc.m114.579581] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2014] [Revised: 07/07/2014] [Indexed: 11/06/2022] Open
Abstract
There is an established role for the endocytic pathway in regulation of epidermal growth factor receptor (EGFR) signaling to downstream effectors. However, because ligand-mediated EGFR endocytosis utilizes multiple "moving parts," dissecting the spatial versus temporal contributions has been challenging. Blocking all endocytic trafficking can have unintended effects on other receptors as well as give rise to compensatory mechanisms, both of which impact interpretation of EGFR signaling. To overcome these limitations, we used epidermal growth factor (EGF) conjugated to polystyrene beads (EGF beads). EGF beads simultaneously activate the EGFR while blocking its endocytosis and allow analysis of EGFR signaling from the plasma membrane. Human telomerase immortalized corneal epithelial (hTCEpi) cells were used to model normal epithelial cell biology. In hTCEpi cells, both cell surface and intracellular EGFRs exhibited dose-dependent increases in effector activity after 15 min of ligand stimulation, but only the serine phosphorylation of signal transducer and activator of transcription 3 (STAT3) was statistically significant when accounting for receptor phosphorylation. However, over time with physiological levels of receptor phosphorylation, cell surface receptors produced either enhanced or sustained mitogen-activated protein kinase kinase (MEK), Casitas B-lineage lymphoma (c-Cbl), and the pro-oncogene Src activity. These increases in effector communication by cell surface receptors resulted in an increase in EGFR ubiquitylation with sustained ligand incubation. Together, these data indicate that spatial regulation of EGFR signaling may be an important regulatory mechanism in receptor down-regulation.
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Affiliation(s)
- Eileen E Parks
- From the Department of Pharmacology and Toxicology, University of Louisville, Louisville, Kentucky 40202
| | - Brian P Ceresa
- From the Department of Pharmacology and Toxicology, University of Louisville, Louisville, Kentucky 40202
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203
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Zhang A, He X, Zhang L, Yang L, Woodman P, Li W. Biogenesis of lysosome-related organelles complex-1 subunit 1 (BLOS1) interacts with sorting nexin 2 and the endosomal sorting complex required for transport-I (ESCRT-I) component TSG101 to mediate the sorting of epidermal growth factor receptor into endosomal compartments. J Biol Chem 2014; 289:29180-94. [PMID: 25183008 DOI: 10.1074/jbc.m114.576561] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Biogenesis of lysosome-related organelles complex-1 (BLOC-1) is a component of the molecular machinery required for the biogenesis of specialized organelles and lysosomal targeting of cargoes via the endosomal to lysosomal trafficking pathway. BLOS1, one subunit of BLOC-1, is implicated in lysosomal trafficking of membrane proteins. We found that the degradation and trafficking of epidermal growth factor receptor (EGFR) were delayed in BLOS1 knockdown cells, which were rescued through BLOS1 overexpression. A key feature to the delayed EGFR degradation is the accumulation of endolysosomes in BLOS1 knockdown cells or BLOS1 knock-out mouse embryonic fibroblasts. BLOS1 interacted with SNX2 (a retromer subunit) and TSG101 (an endosomal sorting complex required for transport subunit-I) to mediate EGFR lysosomal trafficking. These results suggest that coordination of the endolysosomal trafficking proteins is important for proper targeting of EGFR to lysosomes.
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Affiliation(s)
- Aili Zhang
- From the State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China, the University of Chinese Academy of Sciences, Beijing 100039, China, and
| | - Xin He
- From the State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China
| | - Ling Zhang
- the Faculty of Life Sciences, University of Manchester, Manchester M13 9PT, United Kingdom
| | - Lin Yang
- From the State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China
| | - Philip Woodman
- the Faculty of Life Sciences, University of Manchester, Manchester M13 9PT, United Kingdom
| | - Wei Li
- From the State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China,
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204
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Abstract
OBJECTIVE This article reviews the mechanism by which the low density lipoprotein receptor (LDLR) that has bound proprotein convertase subtilisin/kexin type 9 (PCSK9), is rerouted to intracellular degradation instead of being recycled. METHODS A search of relevant published literature has been conducted. RESULTS PCSK9 binds to the LDLR at the cell surface. It is the catalytic domain of PCSK9 that binds to the epidermal growth factor repeat A of the LDLR. The LDLR:PCSK9 complex is internalized through clathrin-mediated endocytosis. Due to an additional electrostatic interaction at acidic pH between the C-terminal domain of PCSK9 and the ligand-binding domain of the LDLR, PCSK9 remains bound to the LDLR in the sorting endosome. As a consequence, the LDLR fails to adopt a closed conformation and is degraded instead of being recycled. The mechanism for the failure of the LDLR to recycle appears to involve ectodomain cleavage of the extended LDLR by a cysteine cathepsin in the sorting endosome. The cleaved LDLR ectodomain will be confined to the vesicular part of the sorting endosome for degradation in the endosomal/lysosomal tract. CONCLUSION Ectodomain cleavage of an LDLR with bound PCSK9 in the sorting endosome disrupts the normal recycling of the LDLR.
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205
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Qi Y, Marlin MC, Liang Z, Berry WL, Janknecht R, Zhou J, Wang Z, Lu G, Li G. Distinct biochemical and functional properties of two Rab5 homologs from the rice blast fungus Magnaporthe oryzae. J Biol Chem 2014; 289:28299-309. [PMID: 25164815 DOI: 10.1074/jbc.m114.591503] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
Rab5 is a key regulator of early endocytosis by promoting early endosomal fusion and motility. In this study, we have unexpectedly found distinct properties of the two Rab5 homologs (MoRab5A and MoRab5B) from Magnaporthe oryzae, a pathogenic fungus in plants whose infection causes rice blast disease. Like mammalian Rab5, MoRab5A and MoRab5B can bind to several Rab5 effectors in a GTP-dependent manner, including EEA1, Rabenosyn-5, and Rabaptin-5. However, MoRab5A shows distinct binding characteristics in the sense that both the wild-type and the GTP hydrolysis-defective constitutively active mutant bind the effectors equally well in GST pull-down assays, suggesting that MoRab5A is defective in GTP hydrolysis and mostly in the GTP-bound conformation in the cell. Indeed, GTP hydrolysis assays indicate that MoRab5A GTPase activity is dramatically lower than MoRab5B and human Rab5 and is insensitive to RabGAP5 stimulation. We have further identified a Pro residue in the switch I region largely responsible for the distinct MoRab5A properties by characterization of MoRab5A and MoRab5B chimeras and mutagenesis. The differences between MoRab5A and MoRab5B extend to their functions in the cell. Although they both target to early endosomes, only MoRab5B closely resembles human Rab5 in promoting early endosome fusion and stimulating fluid phase endocytosis. In contrast, MoRab5A correlates with another related early endosomal Rab, Rab22, in terms of the presence of the switch I Pro residue and the blocked GTPase activity. Our data thus identify MoRab5B as the Rab5 ortholog and suggest that MoRab5A specializes to perform a non-redundant function in endosomal sorting.
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Affiliation(s)
- Yaoyao Qi
- From the Key Laboratory of Biopesticides and Chemical Biology, Ministry of Education, Fujian Agriculture and Forestry University, Fuzhou, Fujian, 350002, China, and Departments of Biochemistry and Molecular Biology
| | | | - Zhimin Liang
- Departments of Biochemistry and Molecular Biology
| | | | - Ralf Janknecht
- Cell Biology, and Peggy and Charles Stephenson Cancer Center, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma 73104
| | - Jie Zhou
- From the Key Laboratory of Biopesticides and Chemical Biology, Ministry of Education, Fujian Agriculture and Forestry University, Fuzhou, Fujian, 350002, China, and
| | - Zonghua Wang
- From the Key Laboratory of Biopesticides and Chemical Biology, Ministry of Education, Fujian Agriculture and Forestry University, Fuzhou, Fujian, 350002, China, and
| | - Guodong Lu
- From the Key Laboratory of Biopesticides and Chemical Biology, Ministry of Education, Fujian Agriculture and Forestry University, Fuzhou, Fujian, 350002, China, and
| | - Guangpu Li
- Departments of Biochemistry and Molecular Biology, Peggy and Charles Stephenson Cancer Center, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma 73104
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206
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Davies BA, Norgan AP, Payne JA, Schulz ME, Nichols MD, Tan JA, Xu Z, Katzmann DJ. Vps4 stimulatory element of the cofactor Vta1 contacts the ATPase Vps4 α7 and α9 to stimulate ATP hydrolysis. J Biol Chem 2014; 289:28707-18. [PMID: 25164817 DOI: 10.1074/jbc.m114.580696] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
The endosomal sorting complexes required for transport (ESCRTs) function in a variety of membrane remodeling processes including multivesicular body sorting, abscission during cytokinesis, budding of enveloped viruses, and repair of the plasma membrane. Vps4 ATPase activity modulates ESCRT function and is itself modulated by its cofactor Vta1 and its substrate ESCRT-III. The carboxyl-terminal Vta1/SBP-1/Lip5 (VSL) domain of Vta1 binds to the Vps4 β-domain to promote Vps4 oligomerization-dependent ATP hydrolysis. Additionally, the Vps4 stimulatory element (VSE) of Vta1 contributes to enhancing Vps4 oligomer ATP hydrolysis. The VSE is also required for Vta1-dependent stimulation of Vps4 by ESCRT-III subunits. However, the manner by which the Vta1 VSE contributes to Vps4 activation is unknown. Existing structural data were used to generate a model of the Vta1 VSE in complex with Vps4. This model implicated residues within the small ATPase associated with various activities (AAA) domain, specifically α-helices 7 and 9, as relevant contact sites. Rational generation of Vps4 mutants defective for VSE-mediated stimulation, as well as intergenic compensatory mutations, support the validity of this model. These findings have uncovered the Vps4 surface responsible for coordinating ESCRT-III-stimulated Vta1 input during ESCRT function and identified a novel mechanism of Vps4 stimulation.
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Affiliation(s)
- Brian A Davies
- From the Department of Biochemistry and Molecular Biology, Mayo Clinic College of Medicine, Rochester, Minnesota 55905
| | - Andrew P Norgan
- From the Department of Biochemistry and Molecular Biology, Mayo Clinic College of Medicine, Rochester, Minnesota 55905
| | - Johanna A Payne
- From the Department of Biochemistry and Molecular Biology, Mayo Clinic College of Medicine, Rochester, Minnesota 55905
| | - Mary E Schulz
- From the Department of Biochemistry and Molecular Biology, Mayo Clinic College of Medicine, Rochester, Minnesota 55905, the Department of Biology, Lawrence University, Appleton, Wisconsin 54911
| | - Micah D Nichols
- From the Department of Biochemistry and Molecular Biology, Mayo Clinic College of Medicine, Rochester, Minnesota 55905, Byron High School, Byron, Minnesota 55920, and
| | - Jason A Tan
- From the Department of Biochemistry and Molecular Biology, Mayo Clinic College of Medicine, Rochester, Minnesota 55905
| | - Zhaohui Xu
- Department of Biological Chemistry, University of Michigan Medical School, Ann Arbor, Michigan 48109
| | - David J Katzmann
- From the Department of Biochemistry and Molecular Biology, Mayo Clinic College of Medicine, Rochester, Minnesota 55905,
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207
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Mas C, Norwood SJ, Bugarcic A, Kinna G, Leneva N, Kovtun O, Ghai R, Ona Yanez LE, Davis JL, Teasdale RD, Collins BM. Structural basis for different phosphoinositide specificities of the PX domains of sorting nexins regulating G-protein signaling. J Biol Chem 2014; 289:28554-68. [PMID: 25148684 DOI: 10.1074/jbc.m114.595959] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Sorting nexins (SNXs) or phox homology (PX) domain containing proteins are central regulators of cell trafficking and signaling. A subfamily of PX domain proteins possesses two unique PX-associated domains, as well as a regulator of G protein-coupled receptor signaling (RGS) domain that attenuates Gαs-coupled G protein-coupled receptor signaling. Here we delineate the structural organization of these RGS-PX proteins, revealing a protein family with a modular architecture that is conserved in all eukaryotes. The one exception to this is mammalian SNX19, which lacks the typical RGS structure but preserves all other domains. The PX domain is a sensor of membrane phosphoinositide lipids and we find that specific sequence alterations in the PX domains of the mammalian RGS-PX proteins, SNX13, SNX14, SNX19, and SNX25, confer differential phosphoinositide binding preferences. Although SNX13 and SNX19 PX domains bind the early endosomal lipid phosphatidylinositol 3-phosphate, SNX14 shows no membrane binding at all. Crystal structures of the SNX19 and SNX14 PX domains reveal key differences, with alterations in SNX14 leading to closure of the binding pocket to prevent phosphoinositide association. Our findings suggest a role for alternative membrane interactions in spatial control of RGS-PX proteins in cell signaling and trafficking.
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Affiliation(s)
- Caroline Mas
- From the Institute for Molecular Bioscience, The University of Queensland, St. Lucia, Queensland 4072, Australia
| | - Suzanne J Norwood
- From the Institute for Molecular Bioscience, The University of Queensland, St. Lucia, Queensland 4072, Australia
| | - Andrea Bugarcic
- From the Institute for Molecular Bioscience, The University of Queensland, St. Lucia, Queensland 4072, Australia
| | - Genevieve Kinna
- From the Institute for Molecular Bioscience, The University of Queensland, St. Lucia, Queensland 4072, Australia
| | - Natalya Leneva
- From the Institute for Molecular Bioscience, The University of Queensland, St. Lucia, Queensland 4072, Australia
| | - Oleksiy Kovtun
- From the Institute for Molecular Bioscience, The University of Queensland, St. Lucia, Queensland 4072, Australia
| | - Rajesh Ghai
- From the Institute for Molecular Bioscience, The University of Queensland, St. Lucia, Queensland 4072, Australia
| | - Lorena E Ona Yanez
- From the Institute for Molecular Bioscience, The University of Queensland, St. Lucia, Queensland 4072, Australia
| | - Jasmine L Davis
- From the Institute for Molecular Bioscience, The University of Queensland, St. Lucia, Queensland 4072, Australia
| | - Rohan D Teasdale
- From the Institute for Molecular Bioscience, The University of Queensland, St. Lucia, Queensland 4072, Australia
| | - Brett M Collins
- From the Institute for Molecular Bioscience, The University of Queensland, St. Lucia, Queensland 4072, Australia
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208
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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] [What about the content of this article? (0)] [Affiliation(s)] [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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209
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Amorim NA, da Silva EML, de Castro RO, da Silva-Januário ME, Mendonça LM, Bonifacino JS, da Costa LJ, daSilva LLP. Interaction of HIV-1 Nef protein with the host protein Alix promotes lysosomal targeting of CD4 receptor. J Biol Chem 2014; 289:27744-56. [PMID: 25118280 DOI: 10.1074/jbc.m114.560193] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
Nef is an accessory protein of human immunodeficiency viruses that promotes viral replication and progression to AIDS through interference with various host trafficking and signaling pathways. A key function of Nef is the down-regulation of the coreceptor CD4 from the surface of the host cells. Nef-induced CD4 down-regulation involves at least two independent steps as follows: acceleration of CD4 endocytosis by a clathrin/AP-2-dependent pathway and targeting of internalized CD4 to multivesicular bodies (MVBs) for eventual degradation in lysosomes. In a previous work, we found that CD4 targeting to the MVB pathway was independent of CD4 ubiquitination. Here, we report that this targeting depends on a direct interaction of Nef with Alix/AIP1, a protein associated with the endosomal sorting complexes required for transport (ESCRT) machinery that assists with cargo recruitment and intraluminal vesicle formation in MVBs. We show that Nef interacts with both the Bro1 and V domains of Alix. Depletion of Alix or overexpression of the Alix V domain impairs lysosomal degradation of CD4 induced by Nef. In contrast, the V domain overexpression does not prevent cell surface removal of CD4 by Nef or protein targeting to the canonical ubiquitination-dependent MVB pathway. We also show that the Nef-Alix interaction occurs in late endosomes that are enriched in internalized CD4. Together, our results indicate that Alix functions as an adaptor for the ESCRT-dependent, ubiquitin-independent targeting of CD4 to the MVB pathway induced by Nef.
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Affiliation(s)
- Nathaly A Amorim
- From the Department of Cell and Molecular Biology, Ribeirão Preto Medical School, University of São Paulo, Ribeirão Preto, SP 14049-900, Brazil
| | - Eulália M L da Silva
- From the Department of Cell and Molecular Biology, Ribeirão Preto Medical School, University of São Paulo, Ribeirão Preto, SP 14049-900, Brazil
| | - Rodrigo O de Castro
- From the Department of Cell and Molecular Biology, Ribeirão Preto Medical School, University of São Paulo, Ribeirão Preto, SP 14049-900, Brazil
| | - Mara E da Silva-Januário
- From the Department of Cell and Molecular Biology, Ribeirão Preto Medical School, University of São Paulo, Ribeirão Preto, SP 14049-900, Brazil
| | - Luiza M Mendonça
- the Department of Virology, Institute of Microbiology Paulo de Góes, Federal University of Rio de Janeiro, Rio de Janeiro, RJ 21941-590, Brazil, and
| | - Juan S Bonifacino
- the Cell Biology and Metabolism Program, Eunice Kennedy Shriver NICHD, National Institutes of Health, Bethesda, Maryland 20892
| | - Luciana J da Costa
- the Department of Virology, Institute of Microbiology Paulo de Góes, Federal University of Rio de Janeiro, Rio de Janeiro, RJ 21941-590, Brazil, and
| | - Luis L P daSilva
- From the Department of Cell and Molecular Biology, Ribeirão Preto Medical School, University of São Paulo, Ribeirão Preto, SP 14049-900, Brazil,
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210
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Abstract
Ligand-dependent regulation of adenylyl cyclase by the large family of seven-transmembrane G protein-coupled receptors (GPCRs) represents a deeply conserved and widely deployed cellular signaling mechanism. Studies of adenylyl cyclase regulation by catecholamine receptors have led to a remarkably detailed understanding of the basic biochemistry of G protein-linked signal transduction and have elaborated numerous mechanisms of regulation. Endocytosis of GPCRs plays a significant role in controlling longer-term cellular responses, such as under conditions of prolonged or repeated receptor activation occurring over a course of hours or more. It has been more challenging to investigate regulatory effects occurring over shorter time intervals, within the minutes to tens of minutes spanning the time course of many acute cyclic AMP (cAMP)-mediated signaling processes. A main reason for this is that biochemical methods used traditionally to assay changes in cytoplasmic cAMP concentration are limited in spatiotemporal resolution and typically require perturbing cellular structure and/or function for implementation. Recent developments in engineering genetically encoded cAMP biosensors linked to optical readouts, which can be expressed in cells or tissues and detected without cellular disruption or major functional perturbation, represent a significant step toward overcoming these limitations. Here, we describe the application of two such cAMP biosensors, one based on enzyme complementation and luminescence detection and another using Förster resonance energy transfer and fluorescence detection. We focus on applying these approaches to investigate cAMP signaling by catecholamine receptors and then on combining these analytical approaches with manipulations of receptor endocytic trafficking.
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Affiliation(s)
- Roshanak Irannejad
- Department of Psychiatry, University of California School of Medicine, San Francisco, California, USA; Department of Cellular & Molecular Pharmacology, University of California School of Medicine, San Francisco, California, USA
| | - Sarah J Kotowski
- Department of Psychiatry, University of California School of Medicine, San Francisco, California, USA; Department of Cellular & Molecular Pharmacology, University of California School of Medicine, San Francisco, California, USA
| | - Mark von Zastrow
- Department of Psychiatry, University of California School of Medicine, San Francisco, California, USA; Department of Cellular & Molecular Pharmacology, University of California School of Medicine, San Francisco, California, USA.
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211
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Singh D, Vaughan R, Kao CC. LL-37 peptide enhancement of signal transduction by Toll-like receptor 3 is regulated by pH: identification of a peptide antagonist of LL-37. J Biol Chem 2014; 289:27614-24. [PMID: 25092290 DOI: 10.1074/jbc.m114.582973] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
LL-37 is a peptide secreted by human epithelial cells that can lyse bacteria, suppress signaling by Toll-like receptor 4 (TLR4), and enhance signaling to double-stranded RNA (dsRNA) by TLR3. How LL-37 interacts with dsRNA to affect signal transduction by TLR3 is not completely understood. We determined that LL-37 binds dsRNA and traffics to endosomes and releases the dsRNA in a pH-dependent manner. Using dynamic light scattering spectroscopy and cell-based FRET experiments, LL-37 was found to form higher order complexes independent of dsRNA binding. Upon acidification LL-37 will dissociate from a larger complex. In cells, LL-37 has a half-live of ∼ 1 h. LL-37 half-life was increased by inhibiting endosome acidification or inhibiting cathepsins, which include proteases whose activity are activated by endosome acidification. Residues in LL-37 that contact poly(I:C) and facilitate oligomerization in vitro were mapped. Peptide LL-29, which contains the oligomerization region of LL-37, inhibited LL-37 enhancement of TLR3 signal transduction. LL-29 prevented LL-37 · poly(I:C) co-localization to endosomes containing TLR3. These results shed light on the requirements for LL-37 enhancement of TLR3 signaling.
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Affiliation(s)
- Divyendu Singh
- From the Department of Molecular and Cellular Biochemistry, Indiana University, Bloomington, Indiana 47405
| | - Robert Vaughan
- From the Department of Molecular and Cellular Biochemistry, Indiana University, Bloomington, Indiana 47405
| | - C Cheng Kao
- From the Department of Molecular and Cellular Biochemistry, Indiana University, Bloomington, Indiana 47405
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212
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Xiao X, Wong EWP, Lie PPY, Mruk DD, Wong CKC, Cheng CY. Cytokines, polarity proteins, and endosomal protein trafficking and signaling-the sertoli cell blood-testis barrier system in vitro as a study model. Methods Enzymol 2014; 534:181-94. [PMID: 24359954 DOI: 10.1016/b978-0-12-397926-1.00010-x] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Endosomal signaling is emerging as one of the most important cellular events that regulate signaling function in mammalian cells or an epithelium in response to changes in environment such as the presence of stimuli mediated by cytokines, toxicants, heat, ions during growth and development, and other cellular processes such as cytokinesis and spermatogenesis. Recent studies have shown that protein endocytosis-the initial step of endosomal signaling-involves the participation of polarity proteins, such as partitioning defective protein 6 (Par6), Cdc42 and 14-3-3 (also known as Par5), which in turn is regulated by cytokines (e.g., TGF-β2, TGF-β3) and testosterone at the Sertoli cell blood-testis barrier (BTB) in the mammalian testis. In this short method paper, we provide a detailed protocol of assessing protein endocytosis, the initial and also the most critical step of endosomal signaling at the Sertoli cell BTB. This biochemical endocytosis assay summarizes our experience for the last decade, which should likely be performed in conjunction with the dual-labeled immunofluorescence analysis to assess protein endocytosis. While we are using a Sertoli cell in vitro system that mimics the BTB in vivo, this approach should be applicable to virtually all mammalian cells.
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Affiliation(s)
- Xiang Xiao
- The Mary M. Wohlford Laboratory for Male Contraceptive Research, Center for Biomedical Research, Population Council, New York, USA; Department of Reproductive Physiology, Zhejiang Academy of Medical Sciences, Hangzhou, Zhejiang, China
| | - Elissa W P Wong
- The Mary M. Wohlford Laboratory for Male Contraceptive Research, Center for Biomedical Research, Population Council, New York, USA
| | - Pearl P Y Lie
- The Mary M. Wohlford Laboratory for Male Contraceptive Research, Center for Biomedical Research, Population Council, New York, USA
| | - Dolores D Mruk
- The Mary M. Wohlford Laboratory for Male Contraceptive Research, Center for Biomedical Research, Population Council, New York, USA
| | - Chris K C Wong
- Department of Biology, Hong Kong Baptist University, Hong Kong, China
| | - C Yan Cheng
- The Mary M. Wohlford Laboratory for Male Contraceptive Research, Center for Biomedical Research, Population Council, New York, USA.
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213
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Kimura Y, Kawawaki J, Kakiyama Y, Shimoda A, Tanaka K. The ESCRT-III adaptor protein Bro1 controls functions of regulator for free ubiquitin chains 1 (Rfu1) in ubiquitin homeostasis. J Biol Chem 2014; 289:21760-9. [PMID: 24962567 DOI: 10.1074/jbc.m114.550871] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Yeast Rfu1 (regulator for free ubiquitin chain 1) localizes to endosomes and plays a role in ubiquitin homeostasis by inhibiting the activity of Doa4. We show that Bro1, a member of the class E vacuolar protein sorting proteins that recruits Doa4 to endosomes and stimulates Doa4 deubiquitinating activity, also recruits Rfu1 to endosomes for involvement in ubiquitin homeostasis. This recruitment was mediated by the direct interaction between a region containing the YPEL motif in Rfu1 and the V domain in Bro1, which could be analogous to the interaction between the mammalian Alix V domain and YPXnL motifs of viral and cellular proteins. Furthermore, overexpression of Bro1, particularly the V domain, prevented Rfu1 degradation in response to heat shock. Thus, Bro1, a Doa4 positive regulator, regulated Rfu1, a negative regulator of Doa4. Rfu1 degradation partly involved the proteasome and a ubiquitin ligase Rsp5, suggesting that Rfu1 stability was regulated by ubiquitin-proteasome pathways.
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Affiliation(s)
- Yoko Kimura
- From the Laboratory of Protein Metabolism, Tokyo Metropolitan Institute of Medical Science, Setagaya-ku, Tokyo 113-8613 and the Department of Applied Biological Chemistry, Graduate School of Agriculture, Shizuoka University, Shizuoka 422-8529, Japan
| | - Junko Kawawaki
- From the Laboratory of Protein Metabolism, Tokyo Metropolitan Institute of Medical Science, Setagaya-ku, Tokyo 113-8613 and
| | - Yukie Kakiyama
- From the Laboratory of Protein Metabolism, Tokyo Metropolitan Institute of Medical Science, Setagaya-ku, Tokyo 113-8613 and
| | - Ayumi Shimoda
- From the Laboratory of Protein Metabolism, Tokyo Metropolitan Institute of Medical Science, Setagaya-ku, Tokyo 113-8613 and
| | - Keiji Tanaka
- From the Laboratory of Protein Metabolism, Tokyo Metropolitan Institute of Medical Science, Setagaya-ku, Tokyo 113-8613 and
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214
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Abstract
The retrograde trafficking from endosomes to the trans-Golgi network (TGN) is one of the major endocytic pathways to divert proteins and lipids away from lysosomal degradation. Retrograde transported cargos enter the TGN via two itineraries from either the early endosome/recycling endosome or the late endosome and involve various machinery components such as retromer, sorting nexins, clathrin, small GTPases, tethering factors and SNAREs. Recently, the pathway has been recognized for its role in signal transduction, physiology and pathogenesis of human diseases.
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Affiliation(s)
- Lei Lu
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore 637551, Singapore.
| | - Wanjin Hong
- Institute of Molecular and Cell Biology, 61 Biopolis Drive, Proteos, Singapore 138673, Singapore; School of Pharmaceutical Sciences, Xiamen University, Xiamen, People's Republic of China
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215
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Hislop JN, Islam TA, Eleftheriadou I, Carpentier DCJ, Trabalza A, Parkinson M, Schiavo G, Mazarakis ND. Rabies virus envelope glycoprotein targets lentiviral vectors to the axonal retrograde pathway in motor neurons. J Biol Chem 2014; 289:16148-63. [PMID: 24753246 DOI: 10.1074/jbc.m114.549980] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Rabies pseudotyped lentiviral vectors have great potential in gene therapy, not least because of their ability to transduce neurons following their distal axonal application. However, very little is known about the molecular processes that underlie their retrograde transport and cell transduction. Using multiple labeling techniques and confocal microscopy, we demonstrated that pseudotyping with rabies virus envelope glycoprotein (RV-G) enabled the axonal retrograde transport of two distinct subtypes of lentiviral vector in motor neuron cultures. Analysis of this process revealed that these vectors trafficked through Rab5-positive endosomes and accumulated within a non-acidic Rab7 compartment. RV-G pseudotyped vectors were co-transported with both the tetanus neurotoxin-binding fragment and the membrane proteins thought to mediate rabies virus endocytosis (neural cell adhesion molecule, nicotinic acetylcholine receptor, and p75 neurotrophin receptor), thus demonstrating that pseudotyping with RV-G targets lentiviral vectors for transport along the same pathway exploited by several toxins and viruses. Using motor neurons cultured in compartmentalized chambers, we demonstrated that axonal retrograde transport of these vectors was rapid and efficient; however, it was not able to transduce the targeted neurons efficiently, suggesting that impairment in processes occurring after arrival of the viral vector in the soma is responsible for the low transduction efficiency seen in vivo, which suggests a novel area for improvement of gene therapy vectors.
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Affiliation(s)
- James N Hislop
- From Gene Therapy, Centre for Neuroinflammation and Neurodegeneration, Division of Brain Sciences, Department of Medicine, Imperial College London, Du Cane Road, London W12 0NN, United Kingdom
| | - Tarin A Islam
- From Gene Therapy, Centre for Neuroinflammation and Neurodegeneration, Division of Brain Sciences, Department of Medicine, Imperial College London, Du Cane Road, London W12 0NN, United Kingdom
| | - Ioanna Eleftheriadou
- From Gene Therapy, Centre for Neuroinflammation and Neurodegeneration, Division of Brain Sciences, Department of Medicine, Imperial College London, Du Cane Road, London W12 0NN, United Kingdom
| | - David C J Carpentier
- From Gene Therapy, Centre for Neuroinflammation and Neurodegeneration, Division of Brain Sciences, Department of Medicine, Imperial College London, Du Cane Road, London W12 0NN, United Kingdom
| | - Antonio Trabalza
- From Gene Therapy, Centre for Neuroinflammation and Neurodegeneration, Division of Brain Sciences, Department of Medicine, Imperial College London, Du Cane Road, London W12 0NN, United Kingdom
| | - Michael Parkinson
- Molecular NeuroPathoBiology Laboratory, Cancer Research UK London Research Institute, Lincoln's Inn Fields Laboratories, 44 Lincoln's Inn Fields, London WC2A 3LY, United Kingdom, and
| | - Giampietro Schiavo
- Molecular NeuroPathoBiology Laboratory, Cancer Research UK London Research Institute, Lincoln's Inn Fields Laboratories, 44 Lincoln's Inn Fields, London WC2A 3LY, United Kingdom, and Sobell Department of Motor Neuroscience and Movement Disorders, UCL Institute of Neurology, University College London, Queen Square, London WC1N 3BG, United Kingdom
| | - Nicholas D Mazarakis
- From Gene Therapy, Centre for Neuroinflammation and Neurodegeneration, Division of Brain Sciences, Department of Medicine, Imperial College London, Du Cane Road, London W12 0NN, United Kingdom,
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216
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Lang MJ, Martinez-Marquez JY, Prosser DC, Ganser LR, Buelto D, Wendland B, Duncan MC. Glucose starvation inhibits autophagy via vacuolar hydrolysis and induces plasma membrane internalization by down-regulating recycling. J Biol Chem 2014; 289:16736-47. [PMID: 24753258 DOI: 10.1074/jbc.m113.525782] [Citation(s) in RCA: 68] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Cellular energy influences all aspects of cellular function. Although cells can adapt to a gradual reduction in energy, acute energy depletion poses a unique challenge. Because acute depletion hampers the transport of new energy sources into the cell, the cell must use endogenous substrates to replenish energy after acute depletion. In the yeast Saccharomyces cerevisiae, glucose starvation causes an acute depletion of intracellular energy that recovers during continued glucose starvation. However, how the cell replenishes energy during the early phase of glucose starvation is unknown. In this study, we investigated the role of pathways that deliver proteins and lipids to the vacuole during glucose starvation. We report that in response to glucose starvation, plasma membrane proteins are directed to the vacuole through reduced recycling at the endosomes. Furthermore, we found that vacuolar hydrolysis inhibits macroautophagy in a target of rapamycin complex 1-dependent manner. Accordingly, we found that endocytosis and hydrolysis are required for survival in glucose starvation, whereas macroautophagy is dispensable. Together, these results suggest that hydrolysis of components delivered to the vacuole independent of autophagy is the cell survival mechanism used by S. cerevisiae in response to glucose starvation.
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Affiliation(s)
- Michael J Lang
- From the Department of Cell and Developmental Biology, the University of Michigan, Ann Arbor, Michigan 48109
| | - Jorge Y Martinez-Marquez
- From the Department of Cell and Developmental Biology, the University of Michigan, Ann Arbor, Michigan 48109
| | - Derek C Prosser
- the Department of Biology, the Johns Hopkins University, Baltimore, Maryland 21218, and
| | - Laura R Ganser
- the Department of Biology, the University of North Carolina, Chapel Hill, North Carolina 27599
| | - Destiney Buelto
- the Curriculum in Genetics and Molecular Biology, the University of North Carolina, Chapel Hill, North Carolina 27599
| | - Beverly Wendland
- the Department of Biology, the Johns Hopkins University, Baltimore, Maryland 21218, and
| | - Mara C Duncan
- From the Department of Cell and Developmental Biology, the University of Michigan, Ann Arbor, Michigan 48109, the Department of Biology, the University of North Carolina, Chapel Hill, North Carolina 27599, the Curriculum in Genetics and Molecular Biology, the University of North Carolina, Chapel Hill, North Carolina 27599
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217
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Granger E, McNee G, Allan V, Woodman P. The role of the cytoskeleton and molecular motors in endosomal dynamics. Semin Cell Dev Biol 2014; 31:20-9. [PMID: 24727350 PMCID: PMC4071412 DOI: 10.1016/j.semcdb.2014.04.011] [Citation(s) in RCA: 176] [Impact Index Per Article: 17.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2014] [Revised: 04/01/2014] [Accepted: 04/03/2014] [Indexed: 12/28/2022]
Abstract
The endocytic pathway is essential for processes that define how cells interact with their environment, including receptor signalling, cell adhesion and migration, pathogen entry, membrane protein turnover and nutrient uptake. The spatial organisation of endocytic trafficking requires motor proteins that tether membranes or transport them along the actin and microtubule cytoskeletons. Microtubules, actin filaments and motor proteins also provide force to deform and assist in the scission of membranes, thereby facilitating endosomal sorting and the generation of transport intermediates.
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Affiliation(s)
- Elizabeth Granger
- Faculty of Life Sciences, University of Manchester, Manchester M13 9PT, UK
| | - Gavin McNee
- Faculty of Life Sciences, University of Manchester, Manchester M13 9PT, UK
| | - Victoria Allan
- Faculty of Life Sciences, University of Manchester, Manchester M13 9PT, UK.
| | - Philip Woodman
- Faculty of Life Sciences, University of Manchester, Manchester M13 9PT, UK.
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218
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Abstract
When studying the living endosome one must first recognise that we are not studying a single discrete organelle but rather a highly dynamic interconnected network of membrane-bound compartments. Endocytosed molecules are sorted and transported through various polymorphic intracellular organelles that mature and interact with one another via fusion and fission events in a highly spatially and temporally co-ordinated manner. As such, we recognise that being a dynamic system, it must be studied in a dynamic fashion. Videomicroscopy has provided profound insights into the cell, and its use in the study of the living endosome has exemplified this supplying a unique perspective on this elusive organelle. In this review we will examine some of the seminal observations that this technology has contributed as well as survey the various assays, tools and technologies that can be applied to understanding the living endosome.
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Affiliation(s)
- Markus Kerr
- Institute for Molecular Bioscience, The University of Queensland, St. Lucia, Queensland, Australia.
| | - Rohan D Teasdale
- Institute for Molecular Bioscience, The University of Queensland, St. Lucia, Queensland, Australia
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219
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Yazaki Y, Hara Y, Tamaki H, Fukaya M, Sakagami H. Endosomal localization of FIP3/Arfophilin-1 and its involvement in dendritic formation of mouse hippocampal neurons. Brain Res 2014; 1557:55-65. [PMID: 24576489 DOI: 10.1016/j.brainres.2014.02.018] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2013] [Revised: 02/06/2014] [Accepted: 02/08/2014] [Indexed: 11/26/2022]
Abstract
Endosomal trafficking mediated by Rab11 and Arf6 small GTPases is essential for various neuronal functions. Family of Rab11-interacting protein 3 (FIP3)/Arfophilin-1, also termed Eferin, is a dual effector for Rab11 and Arf6 and implicated in endosomal trafficking during cytokinesis. To understand the neuronal functions of FIP3, we first showed the widespread neuronal expression of FIP3 mRNA in adult mouse brain by in situ hybridization. Immunohistochemical analysis showed the association of FIP3 with a subpopulation of endosomes labeled with EEA1 and syntaxin 12 in hippocampal neurons. Immunoblot analysis showed the progressive increase of FIP3 with a peak around postnatal day 15 during hippocampal development. Furthermore, knockdown of endogenous FIP3 decreased the total dendritic length of cultured hippocampal neurons with a concomitant increase in the number of short (<40μm) primary dendrites. Together, FIP3 is suggested to regulate dendritic formation possibly through Rab11- and Arf6-mediated endosomal trafficking.
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Affiliation(s)
- Yuuki Yazaki
- Department of Anatomy, Kitasato University School of Medicine, Sagamihara, Kanagawa 252-0329, Japan
| | - Yoshinobu Hara
- Department of Anatomy, Kitasato University School of Medicine, Sagamihara, Kanagawa 252-0329, Japan
| | - Hideaki Tamaki
- Department of Anatomy, Kitasato University School of Medicine, Sagamihara, Kanagawa 252-0329, Japan
| | - Masahiro Fukaya
- Department of Anatomy, Kitasato University School of Medicine, Sagamihara, Kanagawa 252-0329, Japan
| | - Hiroyuki Sakagami
- Department of Anatomy, Kitasato University School of Medicine, Sagamihara, Kanagawa 252-0329, Japan.
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220
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Abstract
The ER is the largest cellular compartment and a major storage site for lipids and ions. In recent years, much attention has focused on contacts between the ER and other organelles, and one particularly intimate relationship is that between the ER and the endosomal system. ER-endosome contacts intensify when endosomes mature, and the ER participates in endosomal processes, such as the termination of surface receptor signaling, multi-vesicular body formation, and transport and fusion events. Cholesterol and Ca(2+) are transferred between the ER and endosomes, possibly acting as messengers for ER-endosome crosstalk. Here, we summarize different types of ER-endosomal communication and discuss membrane contact sites that might facilitate this crosstalk. We review the protein pairs that interact at the ER-endosome interface and find that many of these have a role in cholesterol exchange. We also summarize Ca(2+) exchange between the ER and endosomes, and hypothesize that ER-endosome contacts integrate several cellular functions to guide endosomal maturation. We post the hypothesis that failure in ER-endosome contacts is an unrecognized but important contributor to diseases, such as Niemann-Pick type C disease, Alzheimer's disease and amyotrophic lateral sclerosis.
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Affiliation(s)
- Rik van der Kant
- Department of Cellular and Molecular Medicine, University of California, San Diego, La Jolla, CA 92093, USA
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221
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Cabrera M, Nordmann M, Perz A, Schmedt D, Gerondopoulos A, Barr F, Piehler J, Engelbrecht-Vandré S, Ungermann C. The Mon1-Ccz1 GEF activates the Rab7 GTPase Ypt7 via a longin-fold-Rab interface and association with PI3P-positive membranes. J Cell Sci 2014; 127:1043-51. [PMID: 24413168 DOI: 10.1242/jcs.140921] [Citation(s) in RCA: 62] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
To function in fusion and signaling, Rab GTPases need to be converted into their active GTP form. We previously identified the conserved Mon1-Ccz1 complex as the guanine nucleotide exchange factor (GEF) of the yeast Rab7 GTPase Ypt7. To address the possible GEF mechanism, we generated a homology model of the predicted longin domains of Mon1 and Ccz1 using the Rab-binding surface of the TRAPP complex as a template. On the basis of this, we identified mutations in both yeast Mon1 and Ccz1 that block Ypt7 activation, without affecting heterodimer formation and intracellular localization of Mon1 and Ccz1 at endosomes. Strikingly, the activity of the isolated Mon1-Ccz1 complex for Ypt7 is highly stimulated on membranes, and is promoted by the same anionic phospholipids such as phosphatidylinositol-3-phosphate (PI3P), which also support membrane association of the GEF complex. Our data imply that the GEF activity of the Mon1-Ccz1 complex towards Rab7/Ypt7 requires the interface formed by their longin domains and profits strongly from its association with the organelle surface.
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Affiliation(s)
- Margarita Cabrera
- University of Osnabrück, Department of Biology/Chemistry, Biochemistry section, Barbarastrasse 13, 49076 Osnabrück, Germany
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222
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Hönscher C, Ungermann C. A close-up view of membrane contact sites between the endoplasmic reticulum and the endolysosomal system: from yeast to man. Crit Rev Biochem Mol Biol 2014; 49:262-8. [PMID: 24382115 DOI: 10.3109/10409238.2013.875512] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Maintenance of organelle identity is crucial for the functionality of eukaryotic cells. Hence, transfer reactions between different compartments must be highly efficient and tightly regulated at the same time. Membrane contact sites (MCSs) represent an important route for inter-organelle transport and communication independent of vesicular trafficking. Due to extensive research, the mechanistic understanding of these sites increases constantly. However, how the formation and the versatile functions of MCSs are regulated is mainly unclear. Within this review, we focus on one well-known MCS, the nucleus-vacuole junction in yeast and discuss its analogy to endoplasmic reticulum-late endosome contacts in metazoan. Formation of the junction in yeast requires Vac8, a protein that is involved in various cellular processes at the yeast vacuole and a target of multiple posttranslational modifications. We discuss the possibility that dual functionality of proteins involved in contact formation is a common principle to coordinate inter-organelle transfer with organellar biogenesis.
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Affiliation(s)
- Carina Hönscher
- Department of Biology/Chemistry, Biochemistry Section, University of Osnabrück , Osnabrück , Germany
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223
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Carzaniga R, Domart MC, Duke E, Collinson LM. Correlative cryo-fluorescence and cryo-soft X-ray tomography of adherent cells at European synchrotrons. Methods Cell Biol 2014; 124:151-78. [PMID: 25287841 DOI: 10.1016/b978-0-12-801075-4.00008-2] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Cryo-soft X-ray tomography (cryo-SXT) is a synchrotron-hosted imaging technique used to analyze the ultrastructure of intact, cryo-prepared cells. Correlation of cryo-fluorescence microscopy and cryo-SXT can be used to localize fluorescent proteins to organelles preserved close to native state. Cryo-correlative light and X-ray microscopy (cryo-CLXM) is particularly useful for the study of organelles that are susceptible to chemical fixation artifacts during sample preparation for electron microscopy. In our recent work, we used cryo-CLXM to characterize GFP-LC3-positive early autophagosomes in nutrient-starved HEK293A cells (Duke et al., 2013). Cup-shaped omegasomes were found to form at "hot-spots" on the endoplasmic reticulum. Furthermore, cryo-SXT image stacks revealed the presence of large complex networks of tubulated mitochondria in the starved cells, which would be challenging to model at this scale and resolution using light or electron microscopy. In this chapter, we detail the cryo-CLXM workflow that we developed and optimized for studying adherent mammalian cells. We show examples of data collected at the three European synchrotrons that currently host cryo-SXT microscopes, and describe how raw cryo-SXT datasets are processed into tomoX stacks, modeled, and correlated with cryo-fluorescence data to identify structures of interest.
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Affiliation(s)
- Raffaella Carzaniga
- Electron Microscopy Unit, London Research Institute, Cancer Research UK, London, United Kingdom
| | - Marie-Charlotte Domart
- Electron Microscopy Unit, London Research Institute, Cancer Research UK, London, United Kingdom
| | - Elizabeth Duke
- Diamond Light Source, Harwell Science and Innovation Campus, Didcot, Oxfordshire, United Kingdom
| | - Lucy M Collinson
- Electron Microscopy Unit, London Research Institute, Cancer Research UK, London, United Kingdom
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224
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Abstract
The innate immune system plays key roles in antimicrobial responses by developing the pattern-recognition receptors that recognize microbial components. The endosomal Toll-like receptors (TLRs) and cytosolic RIG-I-like receptors (RLRs) both recognize viral nucleic acids and are essential for antiviral immunity. Recent evidence suggests that compartmentalization of the receptors, and also their adaptor molecule, is important for discrimination between self and nonself and for distinct innate immune signals. TLR3 is a type I transmembrane protein that localizes in the endosomal membrane in myeloid dendritic cells (DCs) and fibroblasts/epithelial cells. TLR3 recognizes extracellular viral double-stranded RNA (dsRNA) and the synthetic dsRNA, poly(I:C). On recognition of dsRNA in the endosomes, TLR3 oligomerizes and induces type I interferon and proinflammatory cytokine production via an adaptor molecule, TICAM-1 (also known as TRIF). Additionally, the TLR3 signal in DCs triggers gene transcription required for DC maturation and the activation of natural killer cells and cytotoxic T lymphocytes. Remarkably, it has been reported that extracellular dsRNA is also recognized by cytosolic RLR. Making a distinction between TLR3-mediated endosomal signaling and RLR-mediated signaling is key to understanding the role of these receptors in innate immunity.
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Affiliation(s)
- Misako Matsumoto
- Department of Microbiology and Immunology, Hokkaido University Graduate School of Medicine, Kita-ku, Sapporo, Japan.
| | - Kenji Funami
- Department of Microbiology and Immunology, Hokkaido University Graduate School of Medicine, Kita-ku, Sapporo, Japan
| | - Megumi Tatematsu
- Department of Microbiology and Immunology, Hokkaido University Graduate School of Medicine, Kita-ku, Sapporo, Japan
| | - Masahiro Azuma
- Department of Microbiology and Immunology, Hokkaido University Graduate School of Medicine, Kita-ku, Sapporo, Japan
| | - Tsukasa Seya
- Department of Microbiology and Immunology, Hokkaido University Graduate School of Medicine, Kita-ku, Sapporo, Japan
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225
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Abstract
While Ras GTPases are best known for mediating growth factor signaling on the plasma membrane, these proteins also have surprisingly complex activities in the endosome. Assisted by a method called bimolecular fluorescent complementation (BiFC), which can detect weak and transient protein-protein interactions and reveal where the binding takes place in live cells, we have identified three effectors, Cdc42, CHMP6, and VPS4A that interact with Ras proteins in endosomes. These effectors are all necessary for Ras-induced transformation, suggesting that for Ras proteins to efficiently induce tumor formation, they must also activate effectors in cytoplasm, such as those in endosomes. Here, we describe how BiFC can be used to detect and screen for Ras effectors and for readily revealing where in the cell the binding occurs.
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226
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Abstract
The nine neurodegenerative disorders including Huntington disease (HD) are caused by the expansion of a trinucleotide CAG repeats (polyQ), which are located within the coding of the affected gene. Previous studies suggested that a gain of toxic function by polyQ repeats is widely thought to have a major role in pathogenesis. PolyQ-expanded htt induced ubiquitinated aggregates cause cell death in neuronal cells. Using a HD cellular model, we demonstrate that Tollip protects cells against the toxicity of polyQ-expanded htt and also protects cells from death (Oguro, Kubota, Shimizu, Ishiura, & Atomi, 2011). Tom1 which belongs to the VHS domain-containing protein family is also found to be directly binding to ubiquitin chains and Tollip (Katoh et al., 2004; Yamakami, Yoshimori, & Yokosawa, 2003). Tollip recruits misfolded protein to aggresome via late endosome. The cell system can be used to determine if your protein of interest is controlled under a part of Tollip pathway or not among other cell homeostatic systems: molecular chaperons, autophagy, and endoplasmic reticulum (ER)-associated degradation (ERAD). Tollip can be used for polyQ cell toxicity sensor by detecting microtubule-dependent trafficking and aggresome colocalization of aggregated protein.
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227
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Abstract
The endogenous generation of reactive oxygen species (ROS), previously perceived as a detrimental by-product of cellular processes, is now recognized as a critical component of intracellular signaling. Exploration of these biological signaling functions requires understanding the complex redox biochemistry and recognizing the compartment-specific elements of ROS generation. The endosomal compartment is increasingly recognized as a source for NADPH oxidase (NOX)-generated signaling ROS. Despite this growing understanding, there are significant limitations to the available detection and measurement systems for endogenous ROS. This chapter provides information about specific methodologies and redox-sensitive probes to guide the investigator and define the critical limitations for many of the available approaches. Although measurement continues to be challenging, the rapid growth and development of new detection systems suggests that our capacity to assign specific signaling roles to endosomal ROS will expand markedly in the next several years.
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Affiliation(s)
- A Paige Davis Volk
- Division of Critical Care, Department of Pediatrics and the Inflammation Program, The University of Iowa, Iowa City, Iowa, USA
| | - Jessica G Moreland
- Division of Critical Care, Department of Pediatrics and the Inflammation Program, The University of Iowa, Iowa City, Iowa, USA.
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228
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Ghai R, Mobli M, Collins BM. Measuring interactions of FERM domain-containing sorting Nexin proteins with endosomal lipids and cargo molecules. Methods Enzymol 2014; 534:331-49. [PMID: 24359963 DOI: 10.1016/B978-0-12-397926-1.00019-6] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Endosomal recycling pathways regulate cellular homeostasis via the transport of internalized material back to the plasma membrane. Phox homology (PX) and band 4.1/ezrin/radixin/moesin (FERM) domain-containing proteins are a recently identified subfamily of PX proteins that are critical for the recycling of numerous transmembrane cargo molecules. The PX-FERM subfamily includes three endosome-associated proteins called sorting nexin (SNX) 17, SNX27, and SNX31. These are modular peripheral membrane proteins that act as central scaffolds mediating protein-lipid interactions, cargo binding, and regulatory protein recruitment. This chapter outlines the methodology employed to classify the PX-FERM family using combined bioinformatics and structure prediction tools. It further details the application of isothermal titration calorimetry and nuclear magnetic resonance spectroscopy to understand the mechanisms that underpin their endosomal membrane recruitment and subsequent recognition of NPxY/NxxY peptide sorting motifs, present in many cargo receptors and required for their trafficking. It is now increasingly recognized that the formation of a stable trafficking complex is dictated by a multitude of coordinated protein-protein and protein-lipid interactions, and the approaches highlighted here will be useful for future studies aimed at understanding these biomolecular interactions in greater detail.
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229
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Acharya S, Laupsien P, Wenzl C, Yan S, Großhans J. Function and dynamics of slam in furrow formation in early Drosophila embryo. Dev Biol 2014; 386:371-84. [PMID: 24368071 DOI: 10.1016/j.ydbio.2013.12.022] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2013] [Revised: 12/11/2013] [Accepted: 12/13/2013] [Indexed: 12/31/2022]
Abstract
The Drosophila embryo undergoes a developmental transition in the blastoderm stage switching from syncytial to cellular development. The cleavage furrow, which encloses nuclei into cells, is a prominent morphological feature of this transition. It is not clear how the pattern of the furrow array is defined and how zygotic genes trigger the formation and invagination of interphase furrows. A key to these questions is provided by the gene slam, which has been previously implicated in controlling furrow invagination. Here we investigate the null phenotype of slam, the dynamics of Slam protein, and its control by the recycling endosome. We find that slam is essential for furrow invagination during cellularisation and together with nullo, for specification of the furrow. During cellularisation, Slam marks first the furrow, which is derived from the metaphase furrow of the previous mitosis. Slightly later, Slam accumulates at new furrows between daughter cells early in interphase. Slam is stably associated with the furrow canal except for the onset of cellularisation as revealed by FRAP experiments. Restriction of Slam to the furrow canal and Slam mobility during cellularisation is controlled by the recycling endosome and centrosomes. We propose a three step model. The retracting metaphase furrow leaves an initial mark. This mark and the border between corresponding daughter nuclei are refined by vesicular transport away from pericentrosomal recycling endosome towards the margins of the somatic buds. Following the onset of zygotic gene expression, Slam and Nullo together stabilise this mark and Slam triggers invagination of the cleavage furrow.
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230
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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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231
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Wunderley L, Brownhill K, Stefani F, Tabernero L, Woodman P. The molecular basis for selective assembly of the UBAP1-containing endosome-specific ESCRT-I complex. J Cell Sci 2013; 127:663-72. [PMID: 24284069 PMCID: PMC4007767 DOI: 10.1242/jcs.140673] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
ESCRT-I is essential for the multivesicular body (MVB) sorting of ubiquitylated cargo such as epidermal growth factor receptor, as well as for several cellular functions, such as cell division and retroviral budding. ESCRT-I has four subunits; TSG101, VPS28, VPS37 and MVB12. There are several members of VPS37 and MVB12 families in mammalian cells, and their differential incorporation into ESCRT-I could provide function-specific variants of the complex. However, it remains unclear whether these different forms of VPS37 and MVB12 combine randomly or generate selective pairings within ESCRT-I, and what the mechanistic basis for such pairing would be. Here, we show that the incorporation of two MVB12 members, UBAP1 and MVB12A, into ESCRT-I is highly selective with respect to their VPS37 partners. We map the region mediating selective assembly of UBAP1–VPS37A to the core ESCRT-I-binding domain of VPS37A. In contrast, selective integration of UBAP1 requires both the minimal ESCRT-I-binding region and a neighbouring predicted helix. The biochemical specificity in ESCRT-I assembly is matched by functional specialisation as siRNA-mediated depletion of UBAP1, but not MVB12A and MVB12B, disrupts ubiquitin-dependent sorting at the MVB.
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Affiliation(s)
- Lydia Wunderley
- Faculty of Life Sciences, University of Manchester, Manchester M13 9PT, UK
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232
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Fortian A, Sorkin A. Live-cell fluorescence imaging reveals high stoichiometry of Grb2 binding to the EGF receptor sustained during endocytosis. J Cell Sci 2013; 127:432-44. [PMID: 24259669 DOI: 10.1242/jcs.137786] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Activation of epidermal growth factor (EGF) receptor (EGFR) leads to its interaction with Grb2, a dual-function adapter mediating both signaling through Ras and receptor endocytosis. We used time-lapse three-dimensional imaging by spinning disk confocal microscopy to analyze trafficking of EGFR and Grb2 in living HeLa cells stimulated with low, physiological concentrations of EGFR ligands. Endogenous Grb2 was replaced in these cells by Grb2 fused to yellow fluorescent protein (YFP). After transient residence in the plasma membrane, Rhodamine-conjugated EGF (EGF-Rh) and Grb2-YFP were rapidly internalized and accumulated in endosomes. Quantitative image analysis revealed that on average two Grb2-YFP molecules were colocalized with one EGF-Rh in cells stimulated with 2 ng/ml EGF-Rh, and the excess of Grb2-YFP over EGF-Rh was even higher when a receptor-saturating concentration of EGF-Rh was used. Therefore, we hypothesize that a single EGFR molecule can be simultaneously associated with functionally distinct Grb2 interaction partners during and after endocytosis. Continuous presence of Grb2-YFP in endosomes was also observed when EGFR was activated by transforming growth factor-α and amphiregulin, suggesting that endosomal EGFRs remain ligand occupied and signaling competent, despite the fact that these growth factors are thought to dissociate from the receptor at acidic pH. The prolonged localization and activity of EGFR-Grb2 complexes in endosomes correlated with the sustained activation of extracellular stimulus-regulated kinase 1/2, suggesting that endosomal EGFRs contribute significantly to this signaling pathway. We propose that endosomal EGFRs function to extend signaling in time and space to compensate for rapid downregulation of surface EGFRs in cells with low receptor expression levels.
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Affiliation(s)
- Arola Fortian
- Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA
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233
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Alpy F, Rousseau A, Schwab Y, Legueux F, Stoll I, Wendling C, Spiegelhalter C, Kessler P, Mathelin C, Rio MC, Levine TP, Tomasetto C. STARD3 or STARD3NL and VAP form a novel molecular tether between late endosomes and the ER. J Cell Sci 2013; 126:5500-12. [PMID: 24105263 DOI: 10.1242/jcs.139295] [Citation(s) in RCA: 171] [Impact Index Per Article: 15.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Inter-organelle membrane contacts sites (MCSs) are specific subcellular regions favoring the exchange of metabolites and information. We investigated the potential role of the late-endosomal membrane-anchored proteins StAR related lipid transfer domain-3 (STARD3) and STARD3 N-terminal like (STARD3NL) in the formation of MCSs involving late-endosomes (LEs). We demonstrate that both STARD3 and STARD3NL create MCSs between LEs and the endoplasmic reticulum (ER). STARD3 and STARD3NL use a conserved two phenylalanines in an acidic tract (FFAT)-motif to interact with ER-anchored VAP proteins. Together, they form an LE-ER tethering complex allowing heterologous membrane apposition. This LE-ER tethering complex affects organelle dynamics by altering the formation of endosomal tubules. An in situ proximity ligation assay between STARD3, STARD3NL and VAP proteins identified endogenous LE-ER MCS. Thus, we report here the identification of proteins involved in inter-organellar interaction.
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Affiliation(s)
- Fabien Alpy
- Institut de Génétique et de Biologie Moléculaire et Cellulaire (IGBMC), Functional Genomics and Cancer Department, 1 rue Laurent Fries, Illkirch, 67404, France
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234
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Huang J, Sun SQ, Lu WT, Xu J, Gan SW, Chen Z, Qiu GP, Huang SQ, Zhuo F, Liu Q, Xu SY. The internalization and lysosomal degradation of brain AQP4 after ischemic injury. Brain Res 2013; 1539:61-72. [PMID: 24070677 DOI: 10.1016/j.brainres.2013.09.022] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2013] [Revised: 08/19/2013] [Accepted: 09/18/2013] [Indexed: 11/25/2022]
Abstract
The membrane-bound water channel aquaporin-4 (AQP4) plays a significant role in maintaining brain water homeostasis. In ischemic brain, changes in the expression level of AQP4 have been reported. Previous studies suggest that the internalization of several membrane-bound proteins, including AQP4, may occur with or without lysosomal degradation. In this study, the internalization of AQP4 was detected in the ischemic rat brain via double immunofluorescence labeling. Specifically, AQP4 and early endosome antigen-1 (EEA1) co-localized after 1 h post-ischemic injury. Moreover, the co-expression of AQP4 and lysosomal-associated membrane protein-1 (LAMP1) was observed after 3 h post-ischemia. These findings suggest that AQP4 is internalized and the lysosome is involved in degrading the internalized AQP4 in the ischemic brain. AQP4 is known to be downregulated by the protein kinase C activator phorbol 12-myristate 13-acetate (PMA) in vivo and in vitro. The results in this study displayed that PMA infusion could decrease brain edema accompanied by AQP4 downregulation in ischemic brain. However, compared with vehicle infusion, PKC activator infusion did not increase the ratio of internalized or lysosomal degraded AQP4. That is, we have not found out evidence to prove protein kinase C activator PMA can promote the internalization or lysosomal degradation of AQP4 in the ischemic brain.
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Affiliation(s)
- Juan Huang
- Institute of Neuroscience, Chongqing Medical University, Chongqing 400016, People's Republic of China; Department of Anatomy, Chongqing Medical University, Chongqing 400016, People's Republic of China
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235
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Lall P, Horgan CP, Oda S, Franklin E, Sultana A, Hanscom SR, McCaffrey MW, Khan AR. Structural and functional analysis of FIP2 binding to the endosome-localised Rab25 GTPase. Biochim Biophys Acta 2013; 1834:2679-90. [PMID: 24056041 DOI: 10.1016/j.bbapap.2013.09.005] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/27/2013] [Revised: 09/08/2013] [Accepted: 09/12/2013] [Indexed: 11/30/2022]
Abstract
Rab small GTPases are the master regulators of intracellular trafficking in eukaryotes. They mediate spatial and temporal recruitment of effector proteins to distinct cellular compartments through GTP-induced changes in their conformation. Despite numerous structural studies, the molecular basis for Rab/effector specificity and subsequent biological activity remains poorly understood. Rab25, also known as Rab11c, which is epithelial-specific, has been heavily implicated in ovarian cancer development and independently appears to act as a tumour suppressor in the context of a distinct subset of carcinomas. Here, we show that Rab25 associates with FIP2 and can recruit this effector protein to endosomal membranes. We report the crystal structure of Rab25 in complex with the C-terminal region of FIP2, which consists of a central dimeric FIP2 coiled-coil that mediates a heterotetrameric Rab25-(FIP2)2-Rab25 complex. Thermodynamic analyses show that, despite a relatively conserved interface, FIP2 binds to Rab25 with an approximate 3-fold weaker affinity than to Rab11a. Reduced affinity is mainly associated with lower enthalpic gains for Rab25:FIP2 complex formation, and can be attributed to subtle differences in the conformations of switch 1 and switch 2. These cellular, structural and thermodynamic studies provide insight into the Rab11/Rab25 subfamily of small GTPases that regulate endosomal trafficking pathways in eukaryotes.
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Affiliation(s)
- Patrick Lall
- School of Biochemistry and Immunology, Trinity College, Dublin 2, Ireland
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236
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Huang ZJ, Kang ST, Leu JH, Chen LL. Endocytic pathway is indicated for white spot syndrome virus (WSSV) entry in shrimp. Fish Shellfish Immunol 2013; 35:707-15. [PMID: 23747417 DOI: 10.1016/j.fsi.2013.05.028] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/06/2013] [Revised: 05/27/2013] [Accepted: 05/28/2013] [Indexed: 05/08/2023]
Abstract
The white spot syndrome virus (WSSV) has had a serious economic impact on the global shrimp aquaculture industry in the past two decades. Although research has clarified a lot about its genome and structure, the mechanism of how WSSV enters a cell is still unclear. In this study to determine this mechanism, primary cultured hemocytes were used as an experimental model to observe the process of WSSV entry because the stable shrimp cell lines for WSSV infection are lacking. After labeling virions and endosomes with fluorescent dyes followed by observation with a confocal microscope, the results show that the WSSV colocalizes with early endosomes. Hemocytes are further treated with different endocytic inhibitors, methyl-β-cyclodextrin (MβCD) and chlorpromazine (CPZ). WSSV still can be detected in the hemocytes treated with CPZ, but not in the hemocytes treated with MβCD. Thus, we conclude that WSSV adopts the caveolae-mediated endocytosis to enter the shrimp cell.
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Affiliation(s)
- Zih-Jhan Huang
- Institute of Marine Biology, National Taiwan Ocean University, No. 2, Pei-Ning Road, Keelung 20224, Taiwan, ROC
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237
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Danson C, Brown E, Hemmings OJ, McGough IJ, Yarwood S, Heesom KJ, Carlton JG, Martin-Serrano J, May MT, Verkade P, Cullen PJ. SNX15 links clathrin endocytosis to the PtdIns3P early endosome independently of the APPL1 endosome. J Cell Sci 2013; 126:4885-99. [PMID: 23986476 DOI: 10.1242/jcs.125732] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
Sorting nexins (SNXs) are key regulators of the endosomal network. In designing an RNAi-mediated loss-of-function screen, we establish that of 30 human SNXs only SNX3, SNX5, SNX9, SNX15 and SNX21 appear to regulate EGF receptor degradative sorting. Suppression of SNX15 results in a delay in receptor degradation arising from a defect in movement of newly internalised EGF-receptor-labelled vesicles into early endosomes. Besides a phosphatidylinositol 3-phosphate- and PX-domain-dependent association to early endosomes, SNX15 also associates with clathrin-coated pits and clathrin-coated vesicles by direct binding to clathrin through a non-canonical clathrin-binding box. From live-cell imaging, it was identified that the activated EGF receptor enters distinct sub-populations of SNX15- and APPL1-labelled peripheral endocytic vesicles, which do not undergo heterotypic fusion. The SNX15-decorated receptor-containing sub-population does, however, undergo direct fusion with the Rab5-labelled early endosome. Our data are consistent with a model in which the EGF receptor enters the early endosome following clathrin-mediated endocytosis through at least two parallel pathways: maturation through an APPL1-intermediate compartment and an alternative more direct fusion between SNX15-decorated endocytic vesicles and the Rab5-positive early endosome.
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Affiliation(s)
- Chris Danson
- The Henry Wellcome Integrated Signalling Laboratories, School of Biochemistry, Medical Sciences Building, University of Bristol, Bristol BS8 1TD, UK
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238
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Gurbaxani B, Dostalek M, Gardner I. Are endosomal trafficking parameters better targets for improving mAb pharmacokinetics than FcRn binding affinity? Mol Immunol 2013; 56:660-74. [PMID: 23917469 DOI: 10.1016/j.molimm.2013.05.008] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2012] [Revised: 05/09/2013] [Accepted: 05/14/2013] [Indexed: 12/21/2022]
Abstract
F.W.R. Brambell deduced the existence of a protective receptor for IgG, the neonatal Fc receptor (FcRn), long before its discovery in the early to mid-1990s. With the coincident, explosive development of IgG-based drugs, FcRn became a popular target for tuning the pharmacokinetics of monoclonal antibodies (mAbs). One aspect of Brambell's initial observation, however, that is seldom discussed since the discovery of the receptor, is the compliance in the mechanism that Brambell observed (saturating at 10s-100s of μM concentration), vs. the comparative stiffness of the receptor kinetics (saturating in the nM range for most species). Although some studies reported that increasing the already very high Fc-FcRn affinity at pH 6.0 further improved mAb half-life, in fact the results were mixed, with later studies increasingly implicating non-FcRn-dependent mechanisms as determinants of mAb pharmacokinetics. Mathematical modelling of the FcRn system has also indicated that the processes determining the pharmacokinetics of mAbs have more nuances than had at first been hypothesised. We propose, in keeping with the latest modelling and experimental evidence reviewed here, that the dynamics of endosomal sorting and trafficking have important roles in the compliant salvage mechanism that Brambell first observed nearly 50 years ago, and therefore also in the pharmacokinetics of mAbs. These ideas lead to many open questions regarding the endosomal trafficking of both FcRn and mAbs and also to what properties of a mAb can be altered to achieve an improvement in pharmacokinetics.
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Affiliation(s)
- Brian Gurbaxani
- Chronic Viral Diseases Branch, Division of High-Consequence Pathogens and Pathology, National Centre for Emerging and Zoonotic Infectious Diseases, Centres for Disease Control and Prevention, Atlanta, GA, USA.
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239
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Miras SL, Merino MC, Gottig N, Rópolo AS, Touz MC. The giardial VPS35 retromer subunit is necessary for multimeric complex assembly and interaction with the vacuolar protein sorting receptor. Biochim Biophys Acta 2013; 1833:2628-2638. [PMID: 23810936 DOI: 10.1016/j.bbamcr.2013.06.015] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/24/2013] [Revised: 06/15/2013] [Accepted: 06/17/2013] [Indexed: 11/15/2022]
Abstract
The retromer is a pentameric protein complex that mediates the retrograde transport of acid hydrolase receptors between endosomes and the trans-Golgi network and is conserved across all eukaryotes. Unlike other eukaryotes, the endomembrane system of Giardia trophozoite is simple and is composed only of the endoplasmic reticulum and peripheral vesicles (PVs), which may represent an ancient organellar system converging compartments such as early and late endosomes and lysosomes. Sorting and trafficking of membrane proteins and soluble hydrolases from the endoplasmic reticulum to the PVs have been described as specific and conserved but whether the giardial retromer participates in receptor recycling remains elusive. Homologs of the retromer Vacuolar Protein Sorting (Vps35p, Vps26p, and Vps29p) have been identified in this parasite. Cloning the GlVPS35 subunit and antisera production enabled the localization of this protein in the PVs as well as in the cytosol. Tagged expression of the subunits was used to demonstrate their association with membranes, and immunofluorescence confocal laser scanning revealed high degrees of colabeling between the retromer subunits and also with the endoplasmic reticulum and PV compartment markers. Protein-protein interaction data revealed interaction between the subunits of GlVPS35 and the cytosolic domain of the hydrolase receptor GlVps. Altogether our data provide original information on the molecular interactions that mediate assembly of the cargo-selective retromer subcomplex and its involvement in the recycling of the acid hydrolase receptor in this parasite.
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Affiliation(s)
- Silvana L Miras
- Instituto de Investigación Médica Mercedes y Martín Ferreyra, INIMEC-Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Universidad Nacional de Córdoba, Córdoba, Argentina
| | - María C Merino
- Instituto de Investigación Médica Mercedes y Martín Ferreyra, INIMEC-Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Universidad Nacional de Córdoba, Córdoba, Argentina
| | - Natalia Gottig
- Facultad de Ciencias Bioquímicas y Farmacéuticas, Instituto de Biología Molecular y Celular de Rosario, CONICET, Universidad Nacional de Rosario, Rosario, Argentina
| | - Andrea S Rópolo
- Instituto de Investigación Médica Mercedes y Martín Ferreyra, INIMEC-Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Universidad Nacional de Córdoba, Córdoba, Argentina
| | - María C Touz
- Instituto de Investigación Médica Mercedes y Martín Ferreyra, INIMEC-Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Universidad Nacional de Córdoba, Córdoba, Argentina.
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240
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Xu J, Xu T, Wu B, Ye Y, You X, Shu X, Pei D, Liu J. Structure of sorting nexin 11 (SNX11) reveals a novel extended phox homology (PX) domain critical for inhibition of SNX10-induced vacuolation. J Biol Chem 2013; 288:16598-16605. [PMID: 23615901 DOI: 10.1074/jbc.m112.449306] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Sorting nexins are phox homology (PX) domain-containing proteins involved in diverse intracellular endosomal trafficking pathways. The PX domain binds to certain phosphatidylinositols and is recruited to vesicles rich in these lipids. The structure of the PX domain is highly conserved, containing a three-stranded β-sheet, followed by three α-helices. Here, we report the crystal structures of truncated human SNX11 (sorting nexin 11). The structures reveal that SNX11 contains a novel PX domain, hereby named the extended PX (PXe) domain, with two additional α-helices at the C terminus. We demonstrate that these α-helices are indispensible for the in vitro functions of SNX11. We propose that this PXe domain is present in SNX10 and is responsible for the vacuolation activity of SNX10. Thus, this novel PXe domain constitutes a structurally and functionally important PX domain subfamily.
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Affiliation(s)
- Jinxin Xu
- State Key Laboratory of Respiratory Disease, Guangzhou Institutes of Biomedicine and Health, Chinese Academy of Sciences, Guangzhou 510530; School of Life Sciences, University of Science and Technology of China, Hefei 230026
| | - Tingting Xu
- State Key Laboratory of Respiratory Disease, Guangzhou Institutes of Biomedicine and Health, Chinese Academy of Sciences, Guangzhou 510530; School of Life Sciences, University of Science and Technology of China, Hefei 230026
| | - Bin Wu
- Key Laboratory of Regenerative Biology, South China Institute for Stem Cell Biology and Regenerative Medicine, Guangzhou Institutes of Biomedicine and Health, Chinese Academy of Sciences, Guangzhou 510530, China
| | - Yinghua Ye
- Key Laboratory of Regenerative Biology, South China Institute for Stem Cell Biology and Regenerative Medicine, Guangzhou Institutes of Biomedicine and Health, Chinese Academy of Sciences, Guangzhou 510530, China
| | - Xiaojuan You
- State Key Laboratory of Respiratory Disease, Guangzhou Institutes of Biomedicine and Health, Chinese Academy of Sciences, Guangzhou 510530
| | - Xiaodong Shu
- Key Laboratory of Regenerative Biology, South China Institute for Stem Cell Biology and Regenerative Medicine, Guangzhou Institutes of Biomedicine and Health, Chinese Academy of Sciences, Guangzhou 510530, China
| | - Duanqing Pei
- Key Laboratory of Regenerative Biology, South China Institute for Stem Cell Biology and Regenerative Medicine, Guangzhou Institutes of Biomedicine and Health, Chinese Academy of Sciences, Guangzhou 510530, China
| | - Jinsong Liu
- State Key Laboratory of Respiratory Disease, Guangzhou Institutes of Biomedicine and Health, Chinese Academy of Sciences, Guangzhou 510530; School of Life Sciences, University of Science and Technology of China, Hefei 230026.
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241
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Hunt SD, Townley AK, Danson CM, Cullen PJ, Stephens DJ. Microtubule motors mediate endosomal sorting by maintaining functional domain organization. J Cell Sci 2013; 126:2493-501. [PMID: 23549789 PMCID: PMC3679488 DOI: 10.1242/jcs.122317] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
Many microtubule motors have been shown to couple to endosomal membranes. These motors include dynein in addition to many different kinesin family members. Sorting nexins (SNXs) are central to the organization and function of endosomes. These proteins can actively shape endosomal membranes and couple directly or indirectly to the minus-end microtubule motor dynein. Motor proteins acting on endosomes drive their motility, dictate their morphology and affect cargo segregation. We have used well-characterized members of the SNX family to elucidate motor coupling using high-resolution light microscopy coupled with depletion of specific microtubule motors. Endosomal domains labelled with SNX1, SNX4 and SNX8 couple to discrete combinations of dynein and kinesin motors. These specific combinations govern the structure and motility of each SNX-coated membrane in addition to the segregation of distinct functional endosomal subdomains. Taken together, our data show that these key features of endosome dynamics are governed by the same set of opposing microtubule motors. Thus, microtubule motors help to define the mosaic layout of endosomes that underpins cargo sorting.
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Affiliation(s)
- Sylvie D Hunt
- Cell Biology Laboratories, School of Biochemistry, Medical Sciences Building, University of Bristol, University Walk, Bristol BS8 1TD, UK
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242
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Abdoli A, Soleimanjahi H, Tavassoti Kheiri M, Jamali A, Jamaati A. Determining influenza virus shedding at different time points in madin-darby canine kidney cell line. Cell J 2013; 15:130-5. [PMID: 23862114 PMCID: PMC3712773] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/25/2012] [Accepted: 12/22/2012] [Indexed: 11/08/2022]
Abstract
OBJECTIVE Monitoring of influenza virus shedding and optimization of multiplicities of infection (MOI) is important in the investigation of a virus one step growth cycle and for obtaining a high yield of virus in vaccine development and conventional basic diagnostic methods. However, eluted infectious viruses may still be present immediately after virus inoculation and when cells are washed following virus cultivation which may lead to a false positive virus infectivity assay. MATERIALS AND METHODS In this experimental study, we investigated influenza virus progeny production in Madin-Darby canine kidney (MDCK) cells with five different MOI at determined time points. The results were analyzed by end point titration tests and immunofluorescence assay. RESULTS Higher titers of eluted virus were observed following a high MOI inoculation of virus in cell culture. Most probably, this was the result of sialic acid residues from viral hemagglutin in proteins that were cleaved by neuraminidase glycoproteins on the surface of the influenza virus, which promoted viral spread from the host cell to the culture supernatant or during endocytosis, where viruses recycle to the cell surface by recycling endosomes which culminated in virus shedding without replication. CONCLUSION We demonstrated that the pattern of influenza virus progeny production was dose-dependent and not uniform. This production was influenced by several factors, particularly MOI. Understanding the exact features of viral particle propagation has a major impact in producing high virus yields in the development of vaccines. Use of lower MOI (0.01) could result in accurate, precise quantitative assays in virus diagnosis and titration methods.
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Affiliation(s)
- Asghar Abdoli
- Department of Virology, Faculty of Medical Science, Tarbiat Modares University, Tehran, Iran
| | - Hoorieh Soleimanjahi
- Department of Virology, Faculty of Medical Science, Tarbiat Modares University, Tehran, Iran,
* Corresponding Address: P.O.Box: 14115-331Department of VirologyFaculty of Medical ScienceTarbiat Modares UniversityTehranIran
P.O.Box: 1316943551Department of VirologyInfluenza Research LaboratoryPasteur Institute of IranTehranIran
| | - Masoumeh Tavassoti Kheiri
- Department of Virology, Influenza Research Laboratory, Pasteur Institute of Iran, Tehran, Iran,
* Corresponding Address: P.O.Box: 14115-331Department of VirologyFaculty of Medical ScienceTarbiat Modares UniversityTehranIran
P.O.Box: 1316943551Department of VirologyInfluenza Research LaboratoryPasteur Institute of IranTehranIran
| | - Abbas Jamali
- Department of Virology, Influenza Research Laboratory, Pasteur Institute of Iran, Tehran, Iran
| | - Azam Jamaati
- Department of Virology, Faculty of Medical Science, Tarbiat Modares University, Tehran, Iran
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Hassink G, Slotman J, Oorschot V, Van Der Reijden BA, Monteferrario D, Noordermeer SM, Van Kerkhof P, Klumperman J, Strous GJ. Identification of the ubiquitin ligase Triad1 as a regulator of endosomal transport. Biol Open 2012; 1:607-14. [PMID: 23213454 PMCID: PMC3509441 DOI: 10.1242/bio.2012778] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
The ubiquitin system plays an important role in trafficking of signaling receptors from the plasma membrane to lysosomes. Triad1 is a ubiquitin ligase that catalyzes the formation of poly-ubiquitin chains linked via lysine-48 as well as lysine-63 residues. We show that depletion of Triad1 affects the sorting of both growth hormone and epidermal growth factor. Triad1-depleted cells accumulate both ligands in endosomes. While fluid phase transport to the lysosomes is reduced in the absence of Triad1, growth hormone receptor can recycle back to the plasma membrane together with transferrin. Using immune electron microscopy we show that Triad1 depletion results in enlarged endosomes with enlarged and irregular shaped intraluminal vesicles. The endosomes display prominent clathrin coats and show increased levels of growth hormone label. We conclude that Triad1 is required for the proper function of multivesicular bodies.
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Affiliation(s)
- Gerco Hassink
- Department of Cell Biology and Institute of Biomembranes, University Medical Center Utrecht , 3584 CX Utrecht , The Netherlands
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