101
|
Septin6 and Septin7 GTP binding proteins regulate AP-3- and ESCRT-dependent multivesicular body biogenesis. PLoS One 2014; 9:e109372. [PMID: 25380047 PMCID: PMC4224394 DOI: 10.1371/journal.pone.0109372] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2014] [Accepted: 09/04/2014] [Indexed: 11/19/2022] Open
Abstract
Septins (SEPTs) form a family of GTP-binding proteins implicated in cytoskeleton and membrane organization, cell division and host/pathogen interactions. The precise function of many family members remains elusive. We show that SEPT6 and SEPT7 complexes bound to F-actin regulate protein sorting during multivesicular body (MVB) biogenesis. These complexes bind AP-3, an adapter complex sorting cargos destined to remain in outer membranes of maturing endosomes, modulate AP-3 membrane interactions and the motility of AP-3-positive endosomes. These SEPT-AP interactions also influence the membrane interaction of ESCRT (endosomal-sorting complex required for transport)-I, which selects ubiquitinated cargos for degradation inside MVBs. Whereas our findings demonstrate that SEPT6 and SEPT7 function in the spatial, temporal organization of AP-3- and ESCRT-coated membrane domains, they uncover an unsuspected coordination of these sorting machineries during MVB biogenesis. This requires the E3 ubiquitin ligase LRSAM1, an AP-3 interactor regulating ESCRT-I sorting activity and whose mutations are linked with Charcot-Marie-Tooth neuropathies.
Collapse
|
102
|
Zlatic SA, Tornieri K, L'hernault SW, Faundez V. Metazoan cell biology of the HOPS tethering complex. CELLULAR LOGISTICS 2014; 1:111-117. [PMID: 21922076 DOI: 10.4161/cl.1.3.17279] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/19/2011] [Revised: 07/18/2011] [Accepted: 07/20/2011] [Indexed: 01/09/2023]
Abstract
Membrane fusion with vacuoles, the lysosome equivalent of the yeast Saccharomyces cerevisiae, is among the best understood membrane fusion events. Our precise understanding of this fusion machinery stems from powerful genetics and elegant in vitro reconstitution assays. Central to vacuolar membrane fusion is the multi-subunit tether the HO motypic fusion and Protein Sorting (HOPS) complex, a complex of proteins that organizes other necessary components of the fusion machinery. We lack a similarly detailed molecular understanding of membrane fusion with lysosomes or lysosome-related organelles in metazoans. However, it is likely that fundamental principles of how rabs, SNAREs and HOPS tethers work to fuse membranes with lysosomes and related organelles are conserved between Saccharomyces cerevisiae and metazoans. Here, we discuss emerging differences in the coat-dependent mechanisms that govern HOPS complex subcellular distribution between Saccharomyces cerevisiae and metazoans. These differences reside upstream of the membrane fusion event. We propose that the differences in how coats segregate class C Vps/HOPS tethers to organelles and domains of metazoan cells are adaptations to complex architectures that characterize metazoan cells such as those of neuronal and epithelial tissues.
Collapse
Affiliation(s)
- Stephanie A Zlatic
- Graduate Program in Biochemistry, Cell and Developmental Biology; Emory University; Atlanta, GA USA
| | | | | | | |
Collapse
|
103
|
Bultema JJ, Boyle JA, Malenke PB, Martin FE, Dell'Angelica EC, Cheney RE, Di Pietro SM. Myosin vc interacts with Rab32 and Rab38 proteins and works in the biogenesis and secretion of melanosomes. J Biol Chem 2014; 289:33513-28. [PMID: 25324551 DOI: 10.1074/jbc.m114.578948] [Citation(s) in RCA: 54] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Class V myosins are actin-based motors with conserved functions in vesicle and organelle trafficking. Herein we report the discovery of a function for Myosin Vc in melanosome biogenesis as an effector of melanosome-associated Rab GTPases. We isolated Myosin Vc in a yeast two-hybrid screening for proteins that interact with Rab38, a Rab protein involved in the biogenesis of melanosomes and other lysosome-related organelles. Rab38 and its close homolog Rab32 bind to Myosin Vc but not to Myosin Va or Myosin Vb. Binding depends on residues in the switch II region of Rab32 and Rab38 and regions of the Myosin Vc coiled-coil tail domain. Myosin Vc also interacts with Rab7a and Rab8a but not with Rab11, Rab17, and Rab27. Although Myosin Vc is not particularly abundant on pigmented melanosomes, its knockdown in MNT-1 melanocytes caused defects in the trafficking of integral membrane proteins to melanosomes with substantially increased surface expression of Tyrp1, nearly complete loss of Tyrp2, and significant Vamp7 mislocalization. Knockdown of Myosin Vc in MNT-1 cells more than doubled the abundance of pigmented melanosomes but did not change the number of unpigmented melanosomes. Together the data demonstrate a novel role for Myosin Vc in melanosome biogenesis and secretion.
Collapse
Affiliation(s)
- Jarred J Bultema
- From the Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, Colorado 80523, the Department of Chemistry and Biochemistry, University of Colorado, Colorado Springs, Colorado Springs, Colorado 80918
| | - Judith A Boyle
- From the Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, Colorado 80523
| | - Parker B Malenke
- From the Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, Colorado 80523
| | - Faye E Martin
- From the Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, Colorado 80523
| | - Esteban C Dell'Angelica
- the Department of Human Genetics, David Geffen School of Medicine, University of California, Los Angeles, California 90095, and
| | - Richard E Cheney
- the Department of Cell Biology and Physiology, School of Medicine, University of North Carolina, Chapel Hill, North Carolina 27599
| | - Santiago M Di Pietro
- From the Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, Colorado 80523,
| |
Collapse
|
104
|
Holland P, Torgersen ML, Sandvig K, Simonsen A. LYST Affects Lysosome Size and Quantity, but not Trafficking or Degradation Through Autophagy or Endocytosis. Traffic 2014; 15:1390-405. [DOI: 10.1111/tra.12227] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2014] [Revised: 09/08/2014] [Accepted: 09/10/2014] [Indexed: 12/22/2022]
Affiliation(s)
- Petter Holland
- Department of Biochemistry, Institute of Basic Medical Sciences; University of Oslo; PB 1112 Blindern, 0317 Oslo Norway
| | - Maria L. Torgersen
- Department of Biochemistry, Institute of Basic Medical Sciences; University of Oslo; PB 1112 Blindern, 0317 Oslo Norway
- Department of Biochemistry, Institute for Cancer Research; Oslo University Hospital - The Norwegian Radium Hospital; 0379 Osloa Norway
| | - Kirsten Sandvig
- Department of Biochemistry, Institute for Cancer Research; Oslo University Hospital - The Norwegian Radium Hospital; 0379 Osloa Norway
| | - Anne Simonsen
- Department of Biochemistry, Institute of Basic Medical Sciences; University of Oslo; PB 1112 Blindern, 0317 Oslo Norway
| |
Collapse
|
105
|
Matrix proteins of Nipah and Hendra viruses interact with beta subunits of AP-3 complexes. J Virol 2014; 88:13099-110. [PMID: 25210190 DOI: 10.1128/jvi.02103-14] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
UNLABELLED Paramyxoviruses and other negative-strand RNA viruses encode matrix proteins that coordinate the virus assembly process. The matrix proteins link the viral glycoproteins and the viral ribonucleoproteins at virus assembly sites and often recruit host machinery that facilitates the budding process. Using a co-affinity purification strategy, we have identified the beta subunit of the AP-3 adapter protein complex, AP3B1, as a binding partner for the M proteins of the zoonotic paramyxoviruses Nipah virus and Hendra virus. Binding function was localized to the serine-rich and acidic Hinge domain of AP3B1, and a 29-amino-acid Hinge-derived polypeptide was sufficient for M protein binding in coimmunoprecipitation assays. Virus-like particle (VLP) production assays were used to assess the relationship between AP3B1 binding and M protein function. We found that for both Nipah virus and Hendra virus, M protein expression in the absence of any other viral proteins led to the efficient production of VLPs in transfected cells, and this VLP production was potently inhibited upon overexpression of short M-binding polypeptides derived from the Hinge region of AP3B1. Both human and bat (Pteropus alecto) AP3B1-derived polypeptides were highly effective at inhibiting the production of VLPs. VLP production was also impaired through small interfering RNA (siRNA)-mediated depletion of AP3B1 from cells. These findings suggest that AP-3-directed trafficking processes are important for henipavirus particle production and identify a new host protein-virus protein binding interface that could become a useful target in future efforts to develop small molecule inhibitors to combat paramyxoviral infections. IMPORTANCE Henipaviruses cause deadly infections in humans, with a mortality rate of about 40%. Hendra virus outbreaks in Australia, all involving horses and some involving transmission to humans, have been a continuing problem. Nipah virus caused a large outbreak in Malaysia in 1998, killing 109 people, and smaller outbreaks have since occurred in Bangladesh and India. In this study, we have defined, for the first time, host factors that interact with henipavirus M proteins and contribute to viral particle assembly. We have also defined a new host protein-viral protein binding interface that can potentially be targeted for the inhibition of paramyxovirus infections.
Collapse
|
106
|
Abstract
The AP (adaptor protein) complexes are heterotetrameric protein complexes that mediate intracellular membrane trafficking along endocytic and secretory transport pathways. There are five different AP complexes: AP-1, AP-2 and AP-3 are clathrin-associated complexes; whereas AP-4 and AP-5 are not. These five AP complexes localize to different intracellular compartments and mediate membrane trafficking in distinct pathways. They recognize and concentrate cargo proteins into vesicular carriers that mediate transport from a donor membrane to a target organellar membrane. AP complexes play important roles in maintaining the normal physiological function of eukaryotic cells. Dysfunction of AP complexes has been implicated in a variety of inherited disorders, including: MEDNIK (mental retardation, enteropathy, deafness, peripheral neuropathy, ichthyosis and keratodermia) syndrome, Fried syndrome, HPS (Hermansky-Pudlak syndrome) and HSP (hereditary spastic paraplegia).
Collapse
Key Words
- adaptor protein complex
- arf1
- membrane trafficking
- polarized sorting
- signal recognition
- ampa, α-amino-3-hydroxy-5-methylisoxazole-4-propionic acid
- ap, adaptor protein
- app, amyloid precursor protein
- arf, adp-ribosylation factors
- bfa, brefeldin a
- casr, calcium-sensing receptor
- copi, coatamer protein i
- egfr, epidermal growth factor receptor
- fhh3, familial hypocalciuric hypercalcaemia type 3
- hps, hermansky–pudlak syndrome
- hsp, hereditary spastic paraplegia
- lro, lysosome-related organelle
- mednik, mental retardation, enteropathy, deafness, peripheral neuropathy, ichthyosis and keratodermia
- pi4p, phosphatidylinositol 4 phosphate
- pip2, phosphatidylinositol (4,5)-bisphosphate
- re, recycling endosome
- spg, spastic paraplegia
- tgn, trans-golgi network
- vps41, vacuolar protein sorting 41
Collapse
Affiliation(s)
- Sang Yoon Park
- *Cell Biology and Metabolism Program, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland, 20892, U.S.A
| | - Xiaoli Guo
- *Cell Biology and Metabolism Program, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland, 20892, U.S.A
- 1To whom correspondence should be addressed (email )
| |
Collapse
|
107
|
van Meel E, Klumperman J. TGN exit of the cation-independent mannose 6-phosphate receptor does not require acid hydrolase binding. CELLULAR LOGISTICS 2014; 4:e954441. [PMID: 25610721 DOI: 10.4161/21592780.2014.954441] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/23/2013] [Accepted: 08/07/2014] [Indexed: 12/23/2022]
Abstract
The cation-independent mannose 6-phosphate (Man-6-P) receptor (CI-MPR) binds newly synthesized, Man-6-P-containing lysosomal acid hydrolases in the trans-Golgi network (TGN) for clathrin-mediated transport to endosomes. It has remained unresolved, however, whether acid hydrolase binding is required for exit of the CI-MPR from the TGN. To address this question we used a B cell line derived from a Mucolipidosis type II (MLII)/I-cell disease patient. In MLII patients, acid hydrolases do not acquire the Man-6-P recognition marker and as a consequence do not bind to the CI-MPR. This causes secretion of the majority of the acid hydrolases and a decreased lysosomal activity resulting in typical inclusion bodies. In agreement herewith, ultrastructural analysis of the MLII patient derived B cells showed numerous inclusion bodies with undigested material, which we defined as autolysosomes. By quantitative immuno-electron microscopy we then studied the distribution of the CI-MPR in these cells. We found that the level of co-localization of TGN-localized CI-MPR and clathrin was similar in MLII and control B cells. Moreover, the CI-MPR was readily found in endosomes of MLII cells and the TGN-to-early endosome ratio of CI-MPR labeling was unaltered. These data show that there is no block in TGN exit of the CI-MPR in the absence of Man-6-P-modified acid hydrolases. Notably, late endosomes and inclusion bodies in MLII B cells contained increased levels of the CI-MPR, which likely reflects the reduced degradative capacity of these compartments.
Collapse
Affiliation(s)
- Eline van Meel
- Department of Cell Biology; University Medical Center Utrecht ; Utrecht, The Netherlands
| | - Judith Klumperman
- Department of Cell Biology; University Medical Center Utrecht ; Utrecht, The Netherlands
| |
Collapse
|
108
|
Akasaki K, Shiotsu K, Michihara A, Ide N, Wada I. Constitutive expression of a COOH-terminal leucine mutant of lysosome-associated membrane protein-1 causes its exclusive localization in low density intracellular vesicles. J Biochem 2014; 156:39-49. [PMID: 24695761 DOI: 10.1093/jb/mvu020] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Lysosome-associated membrane protein-1 (LAMP-1) is a type I transmembrane protein with a short cytoplasmic tail that possesses a lysosome-targeting signal of GYQTI(382)-COOH. Wild-type (WT)-LAMP-1 was exclusively localized in high density lysosomes, and efficiency of LAMP-1's transport to lysosomes depends on its COOH-terminal amino acid residue. Among many different COOH-terminal amino acid substitution mutants of LAMP-1, a leucine-substituted mutant (I382L) displays the most efficient targeting to late endosomes and lysosomes [Akasaki et al. (2010) J. Biochem. 148: , 669-679]. In this study, we generated two human hepatoma cell lines (HepG2 cell lines) that stably express WT-LAMP-1 and I382L, and compared their intracellular distributions. The subcellular fractionation study using Percoll density gradient centrifugation revealed that WT-LAMP-1 had preferential localization in the high density secondary lysosomes where endogenous human LAMP-1 was enriched. In contrast, a major portion of I382L was located in a low density fraction. The low density fraction also contained approximately 80% of endogenous human LAMP-1 and significant amounts of endogenous β-glucuronidase and LAMP-2, which probably represents occurrence of low density lysosomes in the I382L-expressing cells. Double immunofluorescence microscopic analyses distinguished I382L-containing intracellular vesicles from endogenous LAMP-1-containing lysosomes and early endosomes. Altogether, constitutive expression of I382L causes its aberrant intracellular localization and generation of low density lysosomes, indicating that the COOH-terminal isoleucine is critical for normal localization of LAMP-1 in the dense lysosomes.
Collapse
Affiliation(s)
- Kenji Akasaki
- Faculty of Pharmacy and Pharmaceutical Sciences, Fukuyama University, Fukuyama, Hiroshima 729-0292; and Department of Cell Science, Institute of Biomedical Sciences, Fukushima Medical University School of Medicine, Fukushima 960-1295, Japan
| | - Keiko Shiotsu
- Faculty of Pharmacy and Pharmaceutical Sciences, Fukuyama University, Fukuyama, Hiroshima 729-0292; and Department of Cell Science, Institute of Biomedical Sciences, Fukushima Medical University School of Medicine, Fukushima 960-1295, Japan
| | - Akihiro Michihara
- Faculty of Pharmacy and Pharmaceutical Sciences, Fukuyama University, Fukuyama, Hiroshima 729-0292; and Department of Cell Science, Institute of Biomedical Sciences, Fukushima Medical University School of Medicine, Fukushima 960-1295, Japan
| | - Norie Ide
- Faculty of Pharmacy and Pharmaceutical Sciences, Fukuyama University, Fukuyama, Hiroshima 729-0292; and Department of Cell Science, Institute of Biomedical Sciences, Fukushima Medical University School of Medicine, Fukushima 960-1295, Japan
| | - Ikuo Wada
- Faculty of Pharmacy and Pharmaceutical Sciences, Fukuyama University, Fukuyama, Hiroshima 729-0292; and Department of Cell Science, Institute of Biomedical Sciences, Fukushima Medical University School of Medicine, Fukushima 960-1295, Japan
| |
Collapse
|
109
|
Kimpler LA, Glosson NL, Downs D, Gonyo P, May NA, Hudson AW. Adaptor protein complexes AP-1 and AP-3 are required by the HHV-7 Immunoevasin U21 for rerouting of class I MHC molecules to the lysosomal compartment. PLoS One 2014; 9:e99139. [PMID: 24901711 PMCID: PMC4047081 DOI: 10.1371/journal.pone.0099139] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2014] [Accepted: 05/08/2014] [Indexed: 11/19/2022] Open
Abstract
The human herpesvirus-7 (HHV-7) U21 gene product binds to class I major histocompatibility complex (MHC) molecules and reroutes them to a lysosomal compartment. Trafficking of integral membrane proteins to lysosomes is mediated through cytoplasmic sorting signals that recruit heterotetrameric clathrin adaptor protein (AP) complexes, which in turn mediate protein sorting in post-Golgi vesicular transport. Since U21 can mediate rerouting of class I molecules to lysosomes even when lacking its cytoplasmic tail, we hypothesize the existence of a cellular protein that contains the lysosomal sorting information required to escort class I molecules to the lysosomal compartment. If such a protein exists, we expect that it might recruit clathrin adaptor protein complexes as a means of lysosomal sorting. Here we describe experiments demonstrating that the μ adaptins from AP-1 and AP-3 are involved in U21-mediated trafficking of class I molecules to lysosomes. These experiments support the idea that a cellular protein(s) is necessary for U21-mediated lysosomal sorting of class I molecules. We also examine the impact of transient versus chronic knockdown of these adaptor protein complexes, and show that the few remaining μ subunits in the cells are eventually able to reroute class I molecules to lysosomes.
Collapse
Affiliation(s)
- Lisa A. Kimpler
- Department of Microbiology and Molecular Genetics, Medical College of Wisconsin, Milwaukee, Wisconsin, United States of America
| | - Nicole L. Glosson
- Department of Microbiology and Molecular Genetics, Medical College of Wisconsin, Milwaukee, Wisconsin, United States of America
| | - Deanna Downs
- Department of Microbiology and Molecular Genetics, Medical College of Wisconsin, Milwaukee, Wisconsin, United States of America
| | - Patrick Gonyo
- Department of Microbiology and Molecular Genetics, Medical College of Wisconsin, Milwaukee, Wisconsin, United States of America
| | - Nathan A. May
- Department of Microbiology and Molecular Genetics, Medical College of Wisconsin, Milwaukee, Wisconsin, United States of America
| | - Amy W. Hudson
- Department of Microbiology and Molecular Genetics, Medical College of Wisconsin, Milwaukee, Wisconsin, United States of America
- * E-mail:
| |
Collapse
|
110
|
D'Souza RS, Semus R, Billings EA, Meyer CB, Conger K, Casanova JE. Rab4 orchestrates a small GTPase cascade for recruitment of adaptor proteins to early endosomes. Curr Biol 2014; 24:1187-98. [PMID: 24835460 PMCID: PMC4059052 DOI: 10.1016/j.cub.2014.04.003] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2014] [Revised: 03/20/2014] [Accepted: 04/01/2014] [Indexed: 12/11/2022]
Abstract
BACKGROUND Early, sorting endosomes are a major crossroad of membrane traffic, at the intersection of the endocytic and exocytic pathways. The sorting of endosomal cargo for delivery to different subcellular destinations is mediated by a number of distinct coat protein complexes, including adaptor protein 1 (AP-1), AP-3, and Golgi-localized, gamma adaptin ear-containing, Arf-binding (GGAs) protein. Ultrastructural studies suggest that these coats assemble onto tubular subdomains of the endosomal membrane, but the mechanisms of coat recruitment and assembly at this site remain poorly understood. RESULTS Here we report that the endosomal Rab protein Rab4 orchestrates a GTPase cascade that results in the sequential recruitment of the ADP-ribosylation factor (Arf)-like protein Arl1; the Arf-specific guanine nucleotide exchange factors BIG1 and BIG2; and the class I Arfs, Arf1 and Arf3. Knockdown of Arf1, or inhibition of BIG1 and BIG2 activity with brefeldin A results in the loss of AP-1, AP-3, and GGA-3, but not Arl1, from endosomal membranes and the formation of elongated tubules. In contrast, depletion of Arl1 randomizes the distribution of Rab4 on endosomal membranes, inhibits the formation of tubular subdomains, and blocks recruitment of BIG1 and BIG2, Arfs, and adaptor protein complexes to the endosome. CONCLUSIONS Together these findings indicate that Arl1 links Rab4-dependent formation of endosomal sorting domains with downstream assembly of adaptor protein complexes that constitute the endosomal sorting machinery.
Collapse
Affiliation(s)
- Ryan S D'Souza
- Department of Cell Biology, University of Virginia Health Sciences Centre, P.O. Box 800732, Charlottesville, VA 22908, USA
| | - Rachel Semus
- Department of Cell Biology, University of Virginia Health Sciences Centre, P.O. Box 800732, Charlottesville, VA 22908, USA
| | - Emily A Billings
- Department of Cell Biology, University of Virginia Health Sciences Centre, P.O. Box 800732, Charlottesville, VA 22908, USA
| | - Corey B Meyer
- Department of Cell Biology, University of Virginia Health Sciences Centre, P.O. Box 800732, Charlottesville, VA 22908, USA
| | - Kathryn Conger
- Department of Cell Biology, University of Virginia Health Sciences Centre, P.O. Box 800732, Charlottesville, VA 22908, USA
| | - James E Casanova
- Department of Cell Biology, University of Virginia Health Sciences Centre, P.O. Box 800732, Charlottesville, VA 22908, USA.
| |
Collapse
|
111
|
Abstract
Live-cell imaging reveals the endolysosomal system as a complex and highly dynamic network of interacting compartments. Distinct types of endosomes are discerned by kinetic, molecular, and morphological criteria. Although none of these criteria, or combinations thereof, can capture the full complexity of the endolysosomal system, they are extremely useful for experimental purposes. Some membrane domain specializations and specific morphological characteristics can only be seen by ultrastructural analysis after preparation for electron microscopy (EM). Immuno-EM allows a further discrimination of seemingly identical compartments by their molecular makeup. In this review we provide an overview of the ultrastructural characteristics and membrane organization of endosomal compartments, along with their organizing machineries.
Collapse
Affiliation(s)
- Judith Klumperman
- Department of Cell Biology, University Medical Center Utrecht, Heidelberglaan 100, 3584 CX Utrecht, The Netherlands
| | - Graça Raposo
- Institut Curie, Centre de Recherche, Paris F-75248, France Structure and Membrane Compartments CNRS UMR144, Paris F-75248, France
| |
Collapse
|
112
|
Poeter M, Brandherm I, Rossaint J, Rosso G, Shahin V, Skryabin BV, Zarbock A, Gerke V, Rescher U. Annexin A8 controls leukocyte recruitment to activated endothelial cells via cell surface delivery of CD63. Nat Commun 2014; 5:3738. [PMID: 24769558 DOI: 10.1038/ncomms4738] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2014] [Accepted: 03/27/2014] [Indexed: 12/26/2022] Open
Abstract
To enable leukocyte adhesion to activated endothelium, the leukocyte receptor P-selectin is released from Weibel-Palade bodies (WPB) to the endothelial cell surface where it is stabilized by CD63. Here we report that loss of annexin A8 (anxA8) in human umbilical vein endothelial cells (HUVEC) strongly decreases cell surface presentation of CD63 and P-selectin, with a concomitant reduction in leukocyte rolling and adhesion. We confirm the compromised leukocyte adhesiveness in inflammatory-activated endothelial venules of anxA8-deficient mice. We find that WPB of anxA8-deficient HUVEC contain less CD63, and that this is caused by improper transport of CD63 from late multivesicular endosomes to WPB, with CD63 being retained in intraluminal vesicles. Consequently, reduced CD63 cell surface levels are seen following WPB exocytosis, resulting in enhanced P-selectin re-internalization. Our data support a model in which anxA8 affects leukocyte recruitment to activated endothelial cells by supplying WPB with sufficient amounts of the P-selectin regulator CD63.
Collapse
Affiliation(s)
- Michaela Poeter
- 1] Institute of Medical Biochemistry, Center for Molecular Biology of Inflammation, and Interdisciplinary Clinical Research Center, University of Münster, von-Esmarch Strasse 56, 48149 Münster, Germany [2]
| | - Ines Brandherm
- 1] Institute of Medical Biochemistry, Center for Molecular Biology of Inflammation, and Interdisciplinary Clinical Research Center, University of Münster, von-Esmarch Strasse 56, 48149 Münster, Germany [2]
| | - Jan Rossaint
- 1] Department of Anesthesiology, Intensive Care and Pain Medicine, University Hospital Münster, Albert-Schweitzer-Campus 1, 48149 Münster, Germany [2] Department of Vascular Cell Biology, Max-Planck Institute for Molecular Biomedicine, Röntgenstrasse 20, 48149 Münster, Germany
| | - Gonzalo Rosso
- Institute of Physiology II, University of Münster, Robert-Koch-Strasse 27b, 48149 Münster, Germany
| | - Victor Shahin
- Institute of Physiology II, University of Münster, Robert-Koch-Strasse 27b, 48149 Münster, Germany
| | - Boris V Skryabin
- Institute of Experimental Pathology, Center for Molecular Biology of Inflammation, and Interdisciplinary Clinical Research Center, University of Münster, von-Esmarch Strasse 56, 48149 Münster, Germany
| | - Alexander Zarbock
- 1] Department of Anesthesiology, Intensive Care and Pain Medicine, University Hospital Münster, Albert-Schweitzer-Campus 1, 48149 Münster, Germany [2] Department of Vascular Cell Biology, Max-Planck Institute for Molecular Biomedicine, Röntgenstrasse 20, 48149 Münster, Germany
| | - Volker Gerke
- Institute of Medical Biochemistry, Center for Molecular Biology of Inflammation, and Interdisciplinary Clinical Research Center, University of Münster, von-Esmarch Strasse 56, 48149 Münster, Germany
| | - Ursula Rescher
- Institute of Medical Biochemistry, Center for Molecular Biology of Inflammation, and Interdisciplinary Clinical Research Center, University of Münster, von-Esmarch Strasse 56, 48149 Münster, Germany
| |
Collapse
|
113
|
Toshima JY, Nishinoaki S, Sato Y, Yamamoto W, Furukawa D, Siekhaus DE, Sawaguchi A, Toshima J. Bifurcation of the endocytic pathway into Rab5-dependent and -independent transport to the vacuole. Nat Commun 2014; 5:3498. [PMID: 24667230 DOI: 10.1038/ncomms4498] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2013] [Accepted: 02/24/2014] [Indexed: 12/27/2022] Open
Abstract
The yeast Rab5 homologue, Vps21p, is known to be involved both in the vacuolar protein sorting (VPS) pathway from the trans-Golgi network to the vacuole, and in the endocytic pathway from the plasma membrane to the vacuole. However, the intracellular location at which these two pathways converge remains unclear. In addition, the endocytic pathway is not completely blocked in yeast cells lacking all Rab5 genes, suggesting the existence of an unidentified route that bypasses the Rab5-dependent endocytic pathway. Here we show that convergence of the endocytic and VPS pathways occurs upstream of the requirement for Vps21p in these pathways. We also identify a previously unidentified endocytic pathway mediated by the AP-3 complex. Importantly, the AP-3-mediated pathway appears mostly intact in Rab5-disrupted cells, and thus works as an alternative route to the vacuole/lysosome. We propose that the endocytic traffic branches into two routes to reach the vacuole: a Rab5-dependent VPS pathway and a Rab5-independent AP-3-mediated pathway.
Collapse
Affiliation(s)
- Junko Y Toshima
- 1] Faculty of Science and Engineering, Waseda University, Wakamatsu-cho, 2-2, Shinjuku-ku, Tokyo 162-8480, Japan [2] Research Center for RNA Science, RIST, Tokyo University of Science, 6-3-1 Niijyuku, Katsushika-ku, Tokyo 125-8585, Japan
| | - Show Nishinoaki
- Department of Biological Science and Technology, Tokyo University of Science, 6-3-1 Niijyuku, Katsushika-ku, Tokyo 125-8585, Japan
| | - Yoshifumi Sato
- Department of Biological Science and Technology, Tokyo University of Science, 6-3-1 Niijyuku, Katsushika-ku, Tokyo 125-8585, Japan
| | - Wataru Yamamoto
- Department of Biological Science and Technology, Tokyo University of Science, 6-3-1 Niijyuku, Katsushika-ku, Tokyo 125-8585, Japan
| | - Daiki Furukawa
- Department of Biological Science and Technology, Tokyo University of Science, 6-3-1 Niijyuku, Katsushika-ku, Tokyo 125-8585, Japan
| | | | - Akira Sawaguchi
- Department of Anatomy, University of Miyazaki Faculty of Medicine, Miyazaki 889-1692, Japan
| | - Jiro Toshima
- 1] Research Center for RNA Science, RIST, Tokyo University of Science, 6-3-1 Niijyuku, Katsushika-ku, Tokyo 125-8585, Japan [2] Department of Biological Science and Technology, Tokyo University of Science, 6-3-1 Niijyuku, Katsushika-ku, Tokyo 125-8585, Japan
| |
Collapse
|
114
|
Jin RU, Mills JC. RAB26 coordinates lysosome traffic and mitochondrial localization. J Cell Sci 2014; 127:1018-32. [PMID: 24413166 PMCID: PMC3937772 DOI: 10.1242/jcs.138776] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2013] [Accepted: 12/04/2013] [Indexed: 12/29/2022] Open
Abstract
As they mature, professional secretory cells like pancreatic acinar and gastric chief cells induce the transcription factor MIST1 (also known as BHLHA15) to substantially scale up production of large secretory granules in a process that involves expansion of apical cytoplasm and redistribution of lysosomes and mitochondria. How a scaling factor like MIST1 rearranges cellular architecture simply by regulating expression levels of its transcriptional targets is unknown. RAB26 is a MIST1 target whose role in MIST1-mediated secretory cell maturation is also unknown. Here, we confirm that RAB26 expression, unlike most Rabs which are ubiquitously expressed, is tissue specific and largely confined to MIST1-expressing secretory tissues. Surprisingly, functional studies showed that RAB26 predominantly associated with LAMP1/cathepsin D lysosomes and not directly with secretory granules. Moreover, increasing RAB26 expression - by inducing differentiation of zymogen-secreting cells or by direct transfection - caused lysosomes to coalesce in a central, perinuclear region. Lysosome clustering in turn caused redistribution of mitochondria into distinct subcellular neighborhoods. The data elucidate a novel function for RAB26 and suggest a mechanism for how cells could increase transcription of key effectors to reorganize subcellular compartments during differentiation.
Collapse
Affiliation(s)
- Ramon U. Jin
- Division of Gastroenterology, Department of Medicine, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Jason C. Mills
- Division of Gastroenterology, Department of Medicine, Washington University School of Medicine, St. Louis, MO 63110, USA
- Developmental Biology, Washington University School of Medicine, St. Louis, MO 63110, USA
- Pathology & Immunology, Washington University School of Medicine, St. Louis, MO 63110, USA
| |
Collapse
|
115
|
Ham H, Billadeau DD. Human immunodeficiency syndromes affecting human natural killer cell cytolytic activity. Front Immunol 2014; 5:2. [PMID: 24478771 PMCID: PMC3896857 DOI: 10.3389/fimmu.2014.00002] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2013] [Accepted: 01/03/2014] [Indexed: 12/30/2022] Open
Abstract
Natural killer (NK) cells are lymphocytes of the innate immune system that secrete cytokines upon activation and mediate the killing of tumor cells and virus-infected cells, especially those that escape the adaptive T cell response caused by the down regulation of MHC-I. The induction of cytotoxicity requires that NK cells contact target cells through adhesion receptors, and initiate activation signaling leading to increased adhesion and accumulation of F-actin at the NK cell cytotoxic synapse. Concurrently, lytic granules undergo minus-end directed movement and accumulate at the microtubule-organizing center through the interaction with microtubule motor proteins, followed by polarization of the lethal cargo toward the target cell. Ultimately, myosin-dependent movement of the lytic granules toward the NK cell plasma membrane through F-actin channels, along with soluble N-ethylmaleimide-sensitive factor attachment protein receptor-dependent fusion, promotes the release of the lytic granule contents into the cleft between the NK cell and target cell resulting in target cell killing. Herein, we will discuss several disease-causing mutations in primary immunodeficiency syndromes and how they impact NK cell-mediated killing by disrupting distinct steps of this tightly regulated process.
Collapse
Affiliation(s)
- Hyoungjun Ham
- Department of Immunology, College of Medicine, Mayo Clinic , Rochester, MN , USA
| | - Daniel D Billadeau
- Department of Immunology, College of Medicine, Mayo Clinic , Rochester, MN , USA ; Division of Oncology Research and Schulze Center for Novel Therapeutics, College of Medicine, Mayo Clinic , Rochester, MN , USA
| |
Collapse
|
116
|
Guo X, Mattera R, Ren X, Chen Y, Retamal C, González A, Bonifacino JS. The adaptor protein-1 μ1B subunit expands the repertoire of basolateral sorting signal recognition in epithelial cells. Dev Cell 2014; 27:353-66. [PMID: 24229647 DOI: 10.1016/j.devcel.2013.10.006] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2012] [Revised: 07/15/2013] [Accepted: 10/10/2013] [Indexed: 01/05/2023]
Abstract
An outstanding question in protein sorting is why polarized epithelial cells express two isoforms of the μ1 subunit of the AP-1 clathrin adaptor complex: the ubiquitous μ1A and the epithelial-specific μ1B. Previous studies led to the notion that μ1A and μ1B mediate basolateral sorting predominantly from the trans-Golgi network (TGN) and recycling endosomes, respectively. Using improved analytical tools, however, we find that μ1A and μ1B largely colocalize with each other. They also colocalize to similar extents with TGN and recycling endosome markers, as well as with basolateral cargoes transiting biosynthetic and endocytic-recycling routes. Instead, the two isoforms differ in their signal-recognition specificity. In particular, μ1B preferentially binds a subset of signals from cargoes that are sorted basolaterally in a μ1B-dependent manner. We conclude that expression of distinct μ1 isoforms in epithelial cells expands the repertoire of signals recognized by AP-1 for sorting of a broader range of cargoes to the basolateral surface.
Collapse
Affiliation(s)
- Xiaoli Guo
- Cell Biology and Metabolism Program, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA
| | | | | | | | | | | | | |
Collapse
|
117
|
Sirkis DW, Edwards RH, Asensio CS. Widespread dysregulation of peptide hormone release in mice lacking adaptor protein AP-3. PLoS Genet 2013; 9:e1003812. [PMID: 24086151 PMCID: PMC3784564 DOI: 10.1371/journal.pgen.1003812] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2013] [Accepted: 08/06/2013] [Indexed: 12/13/2022] Open
Abstract
The regulated secretion of peptide hormones, neural peptides and many growth factors depends on their sorting into large dense core vesicles (LDCVs) capable of regulated exocytosis. LDCVs form at the trans-Golgi network, but the mechanisms that sort proteins to this regulated secretory pathway and the cytosolic machinery that produces LDCVs remain poorly understood. Recently, we used an RNAi screen to identify a role for heterotetrameric adaptor protein AP-3 in regulated secretion and in particular, LDCV formation. Indeed, mocha mice lacking AP-3 have a severe neurological and behavioral phenotype, but this has been attributed to a role for AP-3 in the endolysosomal rather than biosynthetic pathway. We therefore used mocha mice to determine whether loss of AP-3 also dysregulates peptide release in vivo. We find that adrenal chromaffin cells from mocha animals show increased constitutive exocytosis of both soluble cargo and LDCV membrane proteins, reducing the response to stimulation. We also observe increased basal release of both insulin and glucagon from pancreatic islet cells of mocha mice, suggesting a global disturbance in the release of peptide hormones. AP-3 exists as both ubiquitous and neuronal isoforms, but the analysis of mice lacking each of these isoforms individually and together shows that loss of both is required to reproduce the effect of the mocha mutation on the regulated pathway. In addition, we show that loss of the related adaptor protein AP-1 has a similar effect on regulated secretion but exacerbates the effect of AP-3 RNAi, suggesting distinct roles for the two adaptors in the regulated secretory pathway.
Collapse
Affiliation(s)
- Daniel W. Sirkis
- Graduate Program in Pharmaceutical Sciences and Pharmacogenomics, University of California San Francisco, San Francisco, California, United States of America
- Departments of Physiology and Neurology, University of California San Francisco, San Francisco, California, United States of America
| | - Robert H. Edwards
- Graduate Program in Pharmaceutical Sciences and Pharmacogenomics, University of California San Francisco, San Francisco, California, United States of America
- Departments of Physiology and Neurology, University of California San Francisco, San Francisco, California, United States of America
- * E-mail:
| | - Cédric S. Asensio
- Departments of Physiology and Neurology, University of California San Francisco, San Francisco, California, United States of America
| |
Collapse
|
118
|
Messenger SW, Thomas DDH, Falkowski MA, Byrne JA, Gorelick FS, Groblewski GE. Tumor protein D52 controls trafficking of an apical endolysosomal secretory pathway in pancreatic acinar cells. Am J Physiol Gastrointest Liver Physiol 2013; 305:G439-52. [PMID: 23868405 PMCID: PMC3761242 DOI: 10.1152/ajpgi.00143.2013] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/06/2013] [Accepted: 07/12/2013] [Indexed: 01/31/2023]
Abstract
Zymogen granule (ZG) formation in acinar cells involves zymogen cargo sorting from trans-Golgi into immature secretory granules (ISGs). ISG maturation progresses by removal of lysosomal membrane and select content proteins, which enter endosomal intermediates prior to their apical exocytosis. Constitutive and stimulated secretion through this mechanism is termed the constitutive-like and minor-regulated pathways, respectively. However, the molecular components that control membrane trafficking within these endosomal compartments are largely unknown. We show that tumor protein D52 is highly expressed in endosomal compartments following pancreatic acinar cell stimulation and regulates apical exocytosis of an apically directed endolysosomal compartment. Secretion from the endolysosomal compartment was detected by cell-surface antigen labeling of lysosome-associated membrane protein LAMP1, which is absent from ZGs, and had incomplete overlap with surface labeling of synaptotagmin 1, a marker of ZG exocytosis. Although culturing (16-18 h) of isolated acinar cells is accompanied by a loss of secretory responsiveness, the levels of SNARE proteins necessary for ZG exocytosis were preserved. However, levels of endolysosomal proteins D52, EEA1, Rab5, and LAMP1 markedly decreased with culture. When D52 levels were restored by adenoviral delivery, the levels of these regulatory proteins and secretion of both LAMP1 (endolysosomal) and amylase was strongly enhanced. These secretory effects were absent in alanine and aspartate substitutions of serine 136, the major D52 phosphorylation site, and were inhibited by brefeldin A, which does not directly affect the ZG compartment. Our results indicate that D52 directly regulates apical endolysosomal secretion and are consistent with previous studies, suggesting that this pathway indirectly regulates ZG secretion of digestive enzymes.
Collapse
Affiliation(s)
- Scott W Messenger
- Univ. of Wisconsin, Dept. of Nutritional Sciences, 1415 Linden Dr., Madison, WI 53706.
| | | | | | | | | | | |
Collapse
|
119
|
Popova N, Deyev I, Petrenko A. Clathrin-mediated endocytosis and adaptor proteins. Acta Naturae 2013; 5:62-73. [PMID: 24307937 PMCID: PMC3848845] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022] Open
Abstract
Macromolecules gain access to the cytoplasm of eukaryotic cells using one of several ways of which clathrin-dependent endocytosis is the most researched. Although the mechanism of clathrin-mediated endocytosis is well understood in general, novel adaptor proteins that play various roles in ensuring specific regulation of the mentioned process are being discovered all the time. This review provides a detailed account of the mechanism of clathrin-mediated internalization of activated G protein-coupled receptors, as well as a description of the major proteins involved in this process.
Collapse
Affiliation(s)
- N.V. Popova
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry of the Russian Academy of Sciences, Miklukho-Maklaya St., 16/10, Moscow, Russia, 117997
| | - I.E. Deyev
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry of the Russian Academy of Sciences, Miklukho-Maklaya St., 16/10, Moscow, Russia, 117997
| | - A.G. Petrenko
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry of the Russian Academy of Sciences, Miklukho-Maklaya St., 16/10, Moscow, Russia, 117997
| |
Collapse
|
120
|
Zlatic SA, Grossniklaus EJ, Ryder PV, Salazar G, Mattheyses AL, Peden AA, Faundez V. Chemical-genetic disruption of clathrin function spares adaptor complex 3-dependent endosome vesicle biogenesis. Mol Biol Cell 2013; 24:2378-88. [PMID: 23761069 PMCID: PMC3727930 DOI: 10.1091/mbc.e12-12-0860] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Clathrin–AP-3 association is dispensable for AP-3 vesicle budding from endosomes, which suggests that AP-3–clathrin interactions differ from those by which AP-1 and AP-2 adaptors productively engage clathrin in vesicle biogenesis. A role for clathrin in AP-3–dependent vesicle biogenesis has been inferred from biochemical interactions and colocalization between this adaptor and clathrin. The functionality of these molecular associations, however, is controversial. We comprehensively explore the role of clathrin in AP-3–dependent vesicle budding, using rapid chemical-genetic perturbation of clathrin function with a clathrin light chain–FKBP chimera oligomerizable by the drug AP20187. We find that AP-3 interacts and colocalizes with endogenous and recombinant FKBP chimeric clathrin polypeptides in PC12-cell endosomes. AP-3 displays, however, a divergent behavior from AP-1, AP-2, and clathrin chains. AP-3 cofractionates with clathrin-coated vesicle fractions isolated from PC12 cells even after clathrin function is acutely inhibited by AP20187. We predicted that AP20187 would inhibit AP-3 vesicle formation from endosomes after a brefeldin A block. AP-3 vesicle formation continued, however, after brefeldin A wash-out despite impairment of clathrin function by AP20187. These findings indicate that AP-3–clathrin association is dispensable for endosomal AP-3 vesicle budding and suggest that endosomal AP-3–clathrin interactions differ from those by which AP-1 and AP-2 adaptors productively engage clathrin in vesicle biogenesis.
Collapse
|
121
|
Lacruz RS, Brookes SJ, Wen X, Jimenez JM, Vikman S, Hu P, White SN, Lyngstadaas SP, Okamoto CT, Smith CE, Paine ML. Adaptor protein complex 2-mediated, clathrin-dependent endocytosis, and related gene activities, are a prominent feature during maturation stage amelogenesis. J Bone Miner Res 2013; 28:672-87. [PMID: 23044750 PMCID: PMC3562759 DOI: 10.1002/jbmr.1779] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/23/2012] [Revised: 09/14/2012] [Accepted: 09/18/2012] [Indexed: 12/14/2022]
Abstract
Molecular events defining enamel matrix removal during amelogenesis are poorly understood. Early reports have suggested that adaptor proteins (AP) participate in ameloblast-mediated endocytosis. Enamel formation involves the secretory and maturation stages, with an increase in resorptive function during the latter. Here, using real-time PCR, we show that the expression of clathrin and adaptor protein subunits are upregulated in maturation stage rodent enamel organ cells. AP complex 2 (AP-2) is the most upregulated of the four distinct adaptor protein complexes. Immunolocalization confirms the presence of AP-2 and clathrin in ameloblasts, with strongest reactivity at the apical pole. These data suggest that the resorptive functions of enamel cells involve AP-2 mediated, clathrin-dependent endocytosis, thus implying the likelihood of specific membrane-bound receptor(s) of enamel matrix protein debris. The mRNA expression of other endocytosis-related gene products is also upregulated during maturation including: lysosomal-associated membrane protein 1 (Lamp1); cluster of differentiation 63 and 68 (Cd63 and Cd68); ATPase, H(+) transporting, lysosomal V0 subunit D2 (Atp6v0d2); ATPase, H(+) transporting, lysosomal V1 subunit B2 (Atp6v1b2); chloride channel, voltage-sensitive 7 (Clcn7); and cathepsin K (Ctsk). Immunohistologic data confirms the expression of a number of these proteins in maturation stage ameloblasts. The enamel of Cd63-null mice was also examined. Despite increased mRNA and protein expression in the enamel organ during maturation, the enamel of Cd63-null mice appeared normal. This may suggest inherent functional redundancies between Cd63 and related gene products, such as Lamp1 and Cd68. Ameloblast-like LS8 cells treated with the enamel matrix protein complex Emdogain showed upregulation of AP-2 and clathrin subunits, further supporting the existence of a membrane-bound receptor-regulated pathway for the endocytosis of enamel matrix proteins. These data together define an endocytotic pathway likely used by ameloblasts to remove the enamel matrix during enamel maturation.
Collapse
Affiliation(s)
- Rodrigo S Lacruz
- Center for Craniofacial Molecular Biology, Herman Ostrow School of Dentistry, University of Southern California, Los Angeles, CA 90605, USA
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
122
|
Mardones GA, Burgos PV, Lin Y, Kloer DP, Magadán JG, Hurley JH, Bonifacino JS. Structural basis for the recognition of tyrosine-based sorting signals by the μ3A subunit of the AP-3 adaptor complex. J Biol Chem 2013; 288:9563-71. [PMID: 23404500 DOI: 10.1074/jbc.m113.450775] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Tyrosine-based signals fitting the YXXØ motif mediate sorting of transmembrane proteins to endosomes, lysosomes, the basolateral plasma membrane of polarized epithelial cells, and the somatodendritic domain of neurons through interactions with the homologous μ1, μ2, μ3, and μ4 subunits of the corresponding AP-1, AP-2, AP-3, and AP-4 complexes. Previous x-ray crystallographic analyses identified distinct binding sites for YXXØ signals on μ2 and μ4, which were located on opposite faces of the proteins. To elucidate the mode of recognition of YXXØ signals by other members of the μ family, we solved the crystal structure at 1.85 Å resolution of the C-terminal domain of the μ3 subunit of AP-3 (isoform A) in complex with a peptide encoding a YXXØ signal (SDYQRL) from the trans-Golgi network protein TGN38. The μ3A C-terminal domain consists of an immunoglobulin-like β-sandwich organized into two subdomains, A and B. The YXXØ signal binds in an extended conformation to a site on μ3A subdomain A, at a location similar to the YXXØ-binding site on μ2 but not μ4. The binding sites on μ3A and μ2 exhibit similarities and differences that account for the ability of both proteins to bind distinct sets of YXXØ signals. Biochemical analyses confirm the identification of the μ3A site and show that this protein binds YXXØ signals with 14-19 μm affinity. The surface electrostatic potential of μ3A is less basic than that of μ2, in part explaining the association of AP-3 with intracellular membranes having less acidic phosphoinositides.
Collapse
Affiliation(s)
- Gonzalo A Mardones
- Instituto de Fisiología, Facultad de Medicina, and Centro de Investigación Sur-Austral en Enfermedades del Sistema Nervioso, Universidad Austral de Chile, Valdivia 5110566, Chile
| | | | | | | | | | | | | |
Collapse
|
123
|
New insights into roles of acidocalcisomes and contractile vacuole complex in osmoregulation in protists. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2013; 305:69-113. [PMID: 23890380 DOI: 10.1016/b978-0-12-407695-2.00002-0] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
While free-living protists are usually subjected to hyposmotic environments, parasitic protists are also in contact with hyperosmotic habitats. Recent work in one of these parasites, Trypanosoma cruzi, has revealed that its contractile vacuole complex, which usually collects and expels excess water as a mechanism of regulatory volume decrease after hyposmotic stress, has also a role in cell shrinking when the cells are submitted to hyperosmotic stress. Trypanosomes also have an acidic calcium store rich in polyphosphate (polyP), named the acidocalcisome, which is involved in their response to osmotic stress. Here, we review newly emerging insights on the role of acidocalcisomes and the contractile vacuole complex in the cellular response to hyposmotic and hyperosmotic stresses. We also review the current state of knowledge on the composition of these organelles and their other roles in calcium homeostasis and protein trafficking.
Collapse
|
124
|
Pols MS, van Meel E, Oorschot V, ten Brink C, Fukuda M, Swetha MG, Mayor S, Klumperman J. hVps41 and VAMP7 function in direct TGN to late endosome transport of lysosomal membrane proteins. Nat Commun 2013; 4:1361. [PMID: 23322049 DOI: 10.1038/ncomms2360] [Citation(s) in RCA: 118] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2012] [Accepted: 12/05/2012] [Indexed: 12/18/2022] Open
Abstract
Targeted delivery of lysosome-associated membrane proteins is important for lysosome stability and function. Here we identify a pathway for transport of lysosome-associated membrane proteins directly from the trans-Golgi network to late endosomes, which exists in parallel to mannose 6-phosphate receptor and clathrin-dependent transport of lysosomal enzymes to early endosomes. By immunoelectron microscopy we localized endogenous LAMP-1 and -2 as well as LAMP-1-mGFP to non-coated, biosynthetic carriers at the trans-Golgi network and near late endosomes. These LAMP carriers were negative for mannose 6-phosphate receptor, adaptor-protein complex-1, secretory albumin and endocytic markers, but contained the homotypic fusion and protein sorting complex component hVps41 and the soluble N-ethylmaleimide-sensitive factor attachment protein receptors protein VAMP7. Knockdown of hVps41 or VAMP7 resulted in the accumulation of lysosome-associated membrane protein carriers, whereas knockdown of hVps39 or hVps18 did not, indicating that the effect of hVps41 is independent of CORVET/HOPS. Mannose 6-phosphate receptor carriers remained unaffected upon hVps41 or VAMP7 knockdown, implicating that hVps41 and VAMP7 are specifically involved in the fusion of trans-Golgi network-derived lysosome-associated membrane protein carriers with late endosomes.
Collapse
Affiliation(s)
- Maaike S Pols
- Department of Cell Biology, University Medical Centre Utrecht, AZU Room H02.313, Heidelberglaan 100, Utrecht 3584 CX, The Netherlands
| | | | | | | | | | | | | | | |
Collapse
|
125
|
Bultema JJ, Di Pietro SM. Cell type-specific Rab32 and Rab38 cooperate with the ubiquitous lysosome biogenesis machinery to synthesize specialized lysosome-related organelles. Small GTPases 2012; 4:16-21. [PMID: 23247405 PMCID: PMC3620096 DOI: 10.4161/sgtp.22349] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Lysosome-related organelles (LROs) exist in specialized cells to serve specific functions and typically co-exist with conventional lysosomes. The biogenesis of LROs is known to utilize much of the common protein machinery used in the transport of integral membrane proteins to lysosomes. Consequently, an outstanding question in the field has been how specific cargoes are trafficked to LROs instead of lysosomes, particularly in cells that simultaneously produce both organelles. One LRO, the melanosome, is responsible for the production of the pigment melanin and has long been used as a model system to study the formation of specialized LROs. Importantly, melanocytes, where melanosomes are synthesized, are a cell type that also produces lysosomes and must therefore segregate traffic to each organelle. Two small GTPases, Rab32 and Rab38, are key proteins in the biogenesis of melanosomes and were recently shown to redirect the ubiquitous machinery—BLOC-2, AP-1 and AP-3—to traffic specialized cargoes to melanosomes in melanocytes. In addition, the study revealed Rab32 and Rab38 have both redundant and unique roles in the trafficking of melanin-producing enzymes and overall melanosome biogenesis. Here we review these findings, integrate them with previous knowledge on melanosome biogenesis and discuss their implications for biogenesis of other LROs.
Collapse
Affiliation(s)
- Jarred J Bultema
- Department of Biochemistry and Molecular Biology; Colorado State University; Fort Collins, CO USA
| | | |
Collapse
|
126
|
Zheng L, Saunders CA, Sorensen EB, Waxmonsky NC, Conner SD. Notch signaling from the endosome requires a conserved dileucine motif. Mol Biol Cell 2012; 24:297-307. [PMID: 23171551 PMCID: PMC3564540 DOI: 10.1091/mbc.e12-02-0081] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Notch signaling is reliant on γ-secretase–mediated processing, although the subcellular location where it cleaves Notch to initiate signaling remains unresolved. Findings here support a model in which Notch signaling in mammalian systems is initiated from either the plasma membrane or lysosome, but not the early endosome. Notch signaling is reliant on γ-secretase–mediated processing, although the subcellular location where γ-secretase cleaves Notch to initiate signaling remains unresolved. Accumulating evidence demonstrates that Notch signaling is modulated by endocytosis and endosomal transport. In this study, we investigated the relationship between Notch transport itinerary and signaling capacity. In doing so, we discovered a highly conserved dileucine sorting signal encoded within the cytoplasmic tail that directs Notch to the limiting membrane of the lysosome for signaling. Mutating the dileucine motif led to receptor accumulation in cation-dependent mannose-phosphate receptor–positive tubular early endosomes and a reduction in Notch signaling capacity. Moreover, truncated receptor forms that mimic activated Notch were readily cleaved by γ-secretase within the endosome; however, the cleavage product was proteasome-sensitive and failed to contribute to robust signaling. Collectively these results indicate that Notch signaling from the lysosome limiting membrane is conserved and that receptor targeting to this compartment is an active process. Moreover, the data support a model in which Notch signaling in mammalian systems is initiated from either the plasma membrane or lysosome, but not the early endosome.
Collapse
Affiliation(s)
- Li Zheng
- Department of Genetics, Cell Biology, and Development, University of Minnesota, Minneapolis, MN 55455, USA
| | | | | | | | | |
Collapse
|
127
|
Ambrosio AL, Boyle JA, Di Pietro SM. Mechanism of platelet dense granule biogenesis: study of cargo transport and function of Rab32 and Rab38 in a model system. Blood 2012; 120:4072-81. [PMID: 22927249 PMCID: PMC3496959 DOI: 10.1182/blood-2012-04-420745] [Citation(s) in RCA: 74] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2012] [Accepted: 08/12/2012] [Indexed: 12/21/2022] Open
Abstract
Dense granules are important in platelet aggregation to form a hemostatic plug as evidenced by the increased bleeding time in mice and humans with dense granule deficiency. Dense granules also are targeted by antiplatelet agents because of their role in thrombus formation. Therefore, the molecular understanding of the dense granule and its biogenesis is of vital importance. In this work, we establish a human megakaryocytic cell line (MEG-01) as a model system for the study of dense granule biogenesis using a variety of cell biology and biochemical approaches. Using this model system, we determine the late endocytic origin of these organelles by colocalization of the internalized fluid phase marker dextran with both mepacrine and transmembrane dense granule proteins. By mistargeting of mutant dense granule proteins, we demonstrate that sorting signals recognized by adaptor protein-3 are necessary for normal transport to dense granules. Furthermore, we show that tissue-specific Rab32 and Rab38 are crucial for the fusion of vesicles containing dense granule cargo with the maturing organelle. This work sheds light on the biogenesis of dense granules at the molecular level and opens the possibility of using this powerful model system for the investigation of new components of the biogenesis machinery.
Collapse
Affiliation(s)
- Andrea L Ambrosio
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, CO 80523-1870, USA
| | | | | |
Collapse
|
128
|
Ivan V, Martinez-Sanchez E, Sima LE, Oorschot V, Klumperman J, Petrescu SM, van der Sluijs P. AP-3 and Rabip4' coordinately regulate spatial distribution of lysosomes. PLoS One 2012; 7:e48142. [PMID: 23144738 PMCID: PMC3483219 DOI: 10.1371/journal.pone.0048142] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2012] [Accepted: 09/20/2012] [Indexed: 11/19/2022] Open
Abstract
The RUN and FYVE domain proteins rabip4 and rabip4' are encoded by RUFY1 and differ in a 108 amino acid N-terminal extension in rabip4'. Their identical C terminus binds rab5 and rab4, but the function of rabip4s is incompletely understood. We here found that silencing RUFY1 gene products promoted outgrowth of plasma membrane protrusions, and polarized distribution and clustering of lysosomes at their tips. An interactor screen for proteins that function together with rabip4' yielded the adaptor protein complex AP-3, of which the hinge region in the β3 subunit bound directly to the FYVE domain of rabip4'. Rabip4' colocalized with AP-3 on a tubular subdomain of early endosomes and the extent of colocalization was increased by a dominant negative rab4 mutant. Knock-down of AP-3 had an ever more dramatic effect and caused accumulation of lysosomes in protrusions at the plasma membrane. The most peripheral lysosomes were localized beyond microtubules, within the cortical actin network. Our results uncover a novel function for AP-3 and rabip4' in regulating lysosome positioning through an interorganellar pathway.
Collapse
Affiliation(s)
- Viorica Ivan
- Department of Cell Biology, University Medical Center Utrecht, Utrecht, The Netherlands
- Department of Molecular Cell Biology, Institute of Biochemistry of the Romanian Academy, Bucharest, Romania
| | - Emma Martinez-Sanchez
- Department of Cell Biology, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Livia E. Sima
- Department of Molecular Cell Biology, Institute of Biochemistry of the Romanian Academy, Bucharest, Romania
| | - Viola Oorschot
- Department of Cell Biology, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Judith Klumperman
- Department of Cell Biology, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Stefana M. Petrescu
- Department of Molecular Cell Biology, Institute of Biochemistry of the Romanian Academy, Bucharest, Romania
| | - Peter van der Sluijs
- Department of Cell Biology, University Medical Center Utrecht, Utrecht, The Netherlands
- * E-mail:
| |
Collapse
|
129
|
Kural C, Tacheva-Grigorova SK, Boulant S, Cocucci E, Baust T, Duarte D, Kirchhausen T. Dynamics of intracellular clathrin/AP1- and clathrin/AP3-containing carriers. Cell Rep 2012; 2:1111-9. [PMID: 23103167 DOI: 10.1016/j.celrep.2012.09.025] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2011] [Revised: 06/05/2012] [Accepted: 09/19/2012] [Indexed: 12/13/2022] Open
Abstract
Clathrin/AP1- and clathrin/AP3-coated vesicular carriers originate from endosomes and the trans-Golgi network. Here, we report the real-time visualization of these structures in living cells reliably tracked by rapid, three-dimensional imaging with the use of a spinning-disk confocal microscope. We imaged relatively sparse, diffraction-limited, fluorescent objects containing chimeric fluorescent protein (clathrin light chain, σ adaptor subunits, or dynamin2) with a spatial precision of up to ~30 nm and a temporal resolution of ~1 s. The dynamic characteristics of the intracellular clathrin/AP1 and clathrin/AP3 carriers are similar to those of endocytic clathrin/AP2 pits and vesicles; the clathrin/AP1 coats are, on average, slightly shorter-lived than their AP2 and AP3 counterparts. We confirmed that although dynamin2 is recruited as a burst to clathrin/AP2 pits immediately before their budding from the plasma membrane, we found no evidence supporting a similar association of dynamin2 with clathrin/AP1 or clathrin/AP3 carriers at any stage during their lifetime. We found no effects of chemical inhibitors of dynamin function or the K44A dominant-negative mutant of dynamin on AP1 and AP3 dynamics. This observation suggests that an alternative budding mechanism, yet to be discovered, is responsible for the scission step of clathrin/AP1 and clathrin/AP3 carriers.
Collapse
Affiliation(s)
- Comert Kural
- Department of Cell Biology, Harvard Medical School, Boston and Program in Cellular and Molecular Medicine at Boston Children's Hospital, Boston, MA 02115, USA
| | | | | | | | | | | | | |
Collapse
|
130
|
Young LR, Gulleman PM, Bridges JP, Weaver TE, Deutsch GH, Blackwell TS, McCormack FX. The alveolar epithelium determines susceptibility to lung fibrosis in Hermansky-Pudlak syndrome. Am J Respir Crit Care Med 2012; 186:1014-24. [PMID: 23043085 DOI: 10.1164/rccm.201207-1206oc] [Citation(s) in RCA: 82] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
RATIONALE Hermansky-Pudlak syndrome (HPS) is a family of recessive disorders of intracellular trafficking defects that are associated with highly penetrant pulmonary fibrosis. Naturally occurring HPS mice reliably model important features of the human disease, including constitutive alveolar macrophage activation and susceptibility to profibrotic stimuli. OBJECTIVES To decipher which cell lineage(s) in the alveolar compartment is the predominant driver of fibrotic susceptibility in HPS. METHODS We used five different HPS and Chediak-Higashi mouse models to evaluate genotype-specific fibrotic susceptibility. To determine whether intrinsic defects in HPS alveolar macrophages cause fibrotic susceptibility, we generated bone marrow chimeras in HPS and wild-type mice. To directly test the contribution of the pulmonary epithelium, we developed a transgenic model with epithelial-specific correction of the HPS2 defect in an HPS mouse model. MEASUREMENTS AND MAIN RESULTS Bone marrow transplantation experiments demonstrated that both constitutive alveolar macrophage activation and increased susceptibility to bleomycin-induced fibrosis were conferred by the genotype of the lung epithelium, rather than that of the bone marrow-derived, cellular compartment. Furthermore, transgenic epithelial-specific correction of the HPS defect significantly attenuated bleomycin-induced alveolar epithelial apoptosis, fibrotic susceptibility, and macrophage activation. Type II cell apoptosis was genotype specific, caspase dependent, and correlated with the degree of fibrotic susceptibility. CONCLUSIONS We conclude that pulmonary fibrosis in naturally occurring HPS mice is driven by intracellular trafficking defects that lower the threshold for pulmonary epithelial apoptosis. Our findings demonstrate a pivotal role for the alveolar epithelium in the maintenance of alveolar homeostasis and regulation of alveolar macrophage activation.
Collapse
Affiliation(s)
- Lisa R Young
- Division of Pulmonary Medicine, Department of Pediatrics, Vanderbilt University School of Medicine, 2200 Children's Way, 11215 Doctor's Office Tower, Nashville, TN 37232, USA.
| | | | | | | | | | | | | |
Collapse
|
131
|
Defective HIV-1 particle assembly in AP-3-deficient cells derived from patients with Hermansky-Pudlak syndrome type 2. J Virol 2012; 86:11242-53. [PMID: 22875976 DOI: 10.1128/jvi.00544-12] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Adaptor protein complex 3 (AP-3) is a heterotetramer that is involved in signal-mediated protein sorting to endosomal-lysosomal organelles. AP-3 deficiency in humans, induced by mutations in the AP3B1 gene, which encodes the β3A subunit of the AP-3 complex, results in Hermansky-Pudlak syndrome 2 (HPS2), which is a rare genetic disorder with defective lysosome-related organelles. In a previous study, we identified the AP-3 complex as an important contributor to HIV-1 assembly and release. We hypothesized that cells from patients affected by HPS2 should demonstrate abnormalities of HIV-1 assembly. Here we report that HIV-1 particle assembly and release are indeed diminished in HPS2 fibroblast cultures. Transient or stable expression of the full-length wild-type β3A subunit in HPS2 fibroblasts restored the impaired virus assembly and release. In contrast, virus-like particle release mediated by MA-deficient Gag mutants lacking the AP-3 binding site was not altered in HPS2 cells, indicating that the MA domain serves as the major viral determinant required for the recruitment of the AP-3 complex. AP-3 deficiency decreased HIV-1 Gag localization at the plasma membrane and late endosomes and increased the accumulation of HIV-1 Gag at an intermediate step between early and late endosomes. Blockage of the clathrin-mediated endocytic pathway in HPS2 cells did not reverse the inhibited virus assembly and release imposed by the AP-3 deficiency. These results demonstrate that the intact and stable AP-3 complex is required for HIV-1 assembly and release, and the involvement of the AP-3 complex in late stages of the HIV-1 replication cycle is independent of clathrin-mediated endocytosis.
Collapse
|
132
|
Sitaram A, Marks MS. Mechanisms of protein delivery to melanosomes in pigment cells. Physiology (Bethesda) 2012; 27:85-99. [PMID: 22505665 DOI: 10.1152/physiol.00043.2011] [Citation(s) in RCA: 93] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Vertebrate pigment cells in the eye and skin are useful models for cell types that use specialized endosomal trafficking pathways to partition cargo proteins to unique lysosome-related organelles such as melanosomes. This review describes current models of protein trafficking required for melanosome biogenesis in mammalian melanocytes.
Collapse
Affiliation(s)
- Anand Sitaram
- Cell and Molecular Biology Graduate Group, Department of Pathology and Laboratory Medicine, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | | |
Collapse
|
133
|
Dores MR, Paing MM, Lin H, Montagne WA, Marchese A, Trejo J. AP-3 regulates PAR1 ubiquitin-independent MVB/lysosomal sorting via an ALIX-mediated pathway. Mol Biol Cell 2012; 23:3612-23. [PMID: 22833563 PMCID: PMC3442409 DOI: 10.1091/mbc.e12-03-0251] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
A GPCR ubiquitin-independent MVB/lysosomal sorting pathway is regulated by the adaptor protein complex-3 (AP-3) and ALIX, a noncanonical ESCRT component. AP-3 binds to a PAR1 C-tail–localized, tyrosine-based motif and mediates PAR1 lysosomal degradation. AP-3 also facilitates PAR1 interaction with ALIX, suggesting that AP-3 functions before PAR1 engagement of ALIX and MVB/lysosomal sorting. The sorting of signaling receptors within the endocytic system is important for appropriate cellular responses. After activation, receptors are trafficked to early endosomes and either recycled or sorted to lysosomes and degraded. Most receptors trafficked to lysosomes are modified with ubiquitin and recruited into an endosomal subdomain enriched in hepatocyte growth factor–regulated tyrosine kinase substrate (HRS), a ubiquitin-binding component of the endosomal-sorting complex required for transport (ESCRT) machinery, and then sorted into intraluminal vesicles (ILVs) of multivesicular bodies (MVBs)/lysosomes. However, not all receptors use ubiquitin or the canonical ESCRT machinery to sort to MVBs/lysosomes. This is exemplified by protease-activated receptor-1 (PAR1), a G protein–coupled receptor for thrombin, which sorts to lysosomes independent of ubiquitination and HRS. We recently showed that the adaptor protein ALIX binds to PAR1, recruits ESCRT-III, and mediates receptor sorting to ILVs of MVBs. However, the mechanism that initiates PAR1 sorting at the early endosome is not known. We now report that the adaptor protein complex-3 (AP-3) regulates PAR1 ubiquitin-independent sorting to MVBs through an ALIX-dependent pathway. AP-3 binds to a PAR1 cytoplasmic tail–localized tyrosine-based motif and mediates PAR1 lysosomal degradation independent of ubiquitination. Moreover, AP-3 facilitates PAR1 interaction with ALIX, suggesting that AP-3 functions before PAR1 engagement of ALIX and MVB/lysosomal sorting.
Collapse
Affiliation(s)
- Michael R Dores
- Department of Pharmacology, School of Medicine, University of California, San Diego, La Jolla, CA 92093, USA
| | | | | | | | | | | |
Collapse
|
134
|
Sitaram A, Dennis MK, Chaudhuri R, De Jesus-Rojas W, Tenza D, Setty SRG, Wood CS, Sviderskaya EV, Bennett DC, Raposo G, Bonifacino JS, Marks MS. Differential recognition of a dileucine-based sorting signal by AP-1 and AP-3 reveals a requirement for both BLOC-1 and AP-3 in delivery of OCA2 to melanosomes. Mol Biol Cell 2012; 23:3178-92. [PMID: 22718909 PMCID: PMC3418312 DOI: 10.1091/mbc.e11-06-0509] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
OCA2 is used as a model melanosome cargo protein to define primary sequence elements required for acidic dileucine–motif binding to adaptors AP-1 and AP-3. OCA2 must bind to AP-3 for melanosome localization. BLOC-1 is also required and thus can cooperate with either adaptor for cargo delivery to lysosome-related organelles. Cell types that generate unique lysosome-related organelles (LROs), such as melanosomes in melanocytes, populate nascent LROs with cargoes that are diverted from endosomes. Cargo sorting toward melanosomes correlates with binding via cytoplasmically exposed sorting signals to either heterotetrameric adaptor AP-1 or AP-3. Some cargoes bind both adaptors, but the relative contribution of each adaptor to cargo recognition and their functional interactions with other effectors during transport to melanosomes are not clear. Here we exploit targeted mutagenesis of the acidic dileucine–based sorting signal in the pigment cell–specific protein OCA2 to dissect the relative roles of AP-1 and AP-3 in transport to melanosomes. We show that binding to AP-1 or AP-3 depends on the primary sequence of the signal and not its position within the cytoplasmic domain. Mutants that preferentially bound either AP-1 or AP-3 each trafficked toward melanosomes and functionally complemented OCA2 deficiency, but AP-3 binding was necessary for steady-state melanosome localization. Unlike tyrosinase, which also engages AP-3 for optimal melanosomal delivery, both AP-1– and AP-3–favoring OCA2 variants required BLOC-1 for melanosomal transport. These data provide evidence for distinct roles of AP-1 and AP-3 in OCA2 transport to melanosomes and indicate that BLOC-1 can cooperate with either adaptor during cargo sorting to LROs.
Collapse
Affiliation(s)
- Anand Sitaram
- Department of Pathology and Laboratory Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
135
|
Mantegazza AR, Guttentag SH, El-Benna J, Sasai M, Iwasaki A, Shen H, Laufer TM, Marks MS. Adaptor protein-3 in dendritic cells facilitates phagosomal toll-like receptor signaling and antigen presentation to CD4(+) T cells. Immunity 2012; 36:782-94. [PMID: 22560444 DOI: 10.1016/j.immuni.2012.02.018] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2011] [Revised: 12/08/2011] [Accepted: 02/09/2012] [Indexed: 01/17/2023]
Abstract
Effective major histocompatibility complex-II (MHC-II) antigen presentation from phagocytosed particles requires phagosome-intrinsic Toll-like receptor (TLR) signaling, but the molecular mechanisms underlying TLR delivery to phagosomes and how signaling regulates antigen presentation are incompletely understood. We show a requirement in dendritic cells (DCs) for adaptor protein-3 (AP-3) in efficient TLR recruitment to phagosomes and MHC-II presentation of antigens internalized by phagocytosis but not receptor-mediated endocytosis. DCs from AP-3-deficient pearl mice elicited impaired CD4(+) T cell activation and Th1 effector cell function to particulate antigen in vitro and to recombinant Listeria monocytogenes infection in vivo. Whereas phagolysosome maturation and peptide:MHC-II complex assembly proceeded normally in pearl DCs, peptide:MHC-II export to the cell surface was impeded. This correlated with reduced TLR4 recruitment and proinflammatory signaling from phagosomes by particulate TLR ligands. We propose that AP-3-dependent TLR delivery from endosomes to phagosomes and subsequent signaling mobilize peptide:MHC-II export from intracellular stores.
Collapse
Affiliation(s)
- Adriana R Mantegazza
- Department of Pathology & Laboratory Medicine, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | | | | | | | | | | | | | | |
Collapse
|
136
|
Kent HM, Evans PR, Schäfer IB, Gray SR, Sanderson CM, Luzio JP, Peden AA, Owen DJ. Structural basis of the intracellular sorting of the SNARE VAMP7 by the AP3 adaptor complex. Dev Cell 2012; 22:979-88. [PMID: 22521722 PMCID: PMC3549491 DOI: 10.1016/j.devcel.2012.01.018] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2011] [Revised: 12/14/2011] [Accepted: 01/26/2012] [Indexed: 11/15/2022]
Abstract
VAMP7 is involved in the fusion of late endocytic compartments with other membranes. One possible mechanism of VAMP7 delivery to these late compartments is via the AP3 trafficking adaptor. We show that the linker of the δ-adaptin subunit of AP3 binds the VAMP7 longin domain and determines the structure of their complex. Mutation of residues on both partners abolishes the interaction in vitro and in vivo. The binding of VAMP7 to δ-adaptin requires the VAMP7 SNARE motif to be engaged in SNARE complex formation and hence AP3 must transport VAMP7 when VAMP7 is part of a cis-SNARE complex. The absence of δ-adaptin causes destabilization of the AP3 complex in mouse mocha fibroblasts and mislocalization of VAMP7. The mislocalization can be rescued by transfection with wild-type δ-adaptin but not by δ-adaptin containing mutations that abolish VAMP7 binding, despite in all cases intact AP3 being present and LAMP1 trafficking being rescued.
Collapse
Affiliation(s)
- Helen M Kent
- Medical Research Council Laboratory of Molecular Biology, Hills Road, Cambridge CB2 2QH, UK
| | | | | | | | | | | | | | | |
Collapse
|
137
|
Bultema JJ, Ambrosio AL, Burek CL, Di Pietro SM. BLOC-2, AP-3, and AP-1 proteins function in concert with Rab38 and Rab32 proteins to mediate protein trafficking to lysosome-related organelles. J Biol Chem 2012; 287:19550-63. [PMID: 22511774 DOI: 10.1074/jbc.m112.351908] [Citation(s) in RCA: 100] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Lysosome-related organelles (LROs) are synthesized in specialized cell types where they largely coexist with conventional lysosomes. Most of the known cellular transport machinery involved in biogenesis are ubiquitously expressed and shared between lysosomes and LROs. Examples of common components are the adaptor protein complex-3 (AP-3) and biogenesis of lysosome-related organelle complex (BLOC)-2. These protein complexes control sorting and transport of newly synthesized integral membrane proteins from early endosomes to both lysosomes and LROs such as the melanosome. However, it is unknown what factors cooperate with the ubiquitous transport machinery to mediate transport to LROs in specialized cells. Focusing on the melanosome, we show that the ubiquitous machinery interacts with cell type-specific Rab proteins, Rab38 and Rab32, to facilitate transport to the maturing organelle. BLOC-2, AP-3, and AP-1 coimmunoprecipitated with Rab38 and Rab32 from MNT-1 melanocytic cell extracts. BLOC-2, AP-3, AP-1, and clathrin partially colocalized with Rab38 and Rab32 by confocal immunofluorescence microscopy in MNT-1 cells. Rab38- and Rab32-deficient MNT-1 cells displayed abnormal trafficking and steady state levels of known cargoes of the BLOC-2, AP-3, and AP-1 pathways, the melanin-synthesizing enzymes tyrosinase and tyrosinase-related protein-1. These observations support the idea that Rab38 and Rab32 are the specific factors that direct the ubiquitous machinery to mediate transport from early endosomes to maturing LROs. Additionally, analysis of tyrosinase-related protein-2 and total melanin production indicates that Rab32 has unique functions that cannot be carried out by Rab38 in melanosome biogenesis.
Collapse
Affiliation(s)
- Jarred J Bultema
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, Colorado 80523, USA
| | | | | | | |
Collapse
|
138
|
Baron M. Endocytic routes to Notch activation. Semin Cell Dev Biol 2012; 23:437-42. [PMID: 22285298 DOI: 10.1016/j.semcdb.2012.01.008] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2012] [Accepted: 01/17/2012] [Indexed: 01/16/2023]
Abstract
It is well established that Notch signalling is activated in response to ligand binding through a series of proteolytic cleavages that release the Notch intracellular domain, allowing it to translocate to the nucleus to regulate downstream target gene expression. However there is still much to learn about the mechanisms that can bring about these proteolytic events in the numerous physiological contexts in which signal activation occurs. A number of studies have suggested that endocytosis of Notch contributes to the signal activation process, but the molecular details are unclear and controversial. There is conflicting data as to whether endocytosis of the receptor is essential for ligand-induced signalling or supplements it. Other studies have revealed that Notch can be activated in the endosomal pathway, independently of its ligands, through the activity of Deltex, a Ring-domain Ubiquitin ligase that binds to the Notch intracellular domain. However, it is unclear how the Deltex-activation mechanism relates to that of ligand-induced signalling, or to ectopic Notch signalling brought about by disruption of ESCRT complexes that affect multivesicular body formation. This review will address these issues and argue that the data are best reconciled by proposing distinct activation mechanisms in different cellular locations that contribute to the cellular pool of the soluble Notch intracellular domain. The resulting signalling network may provide developmental robustness to environmental and genetic variation.
Collapse
Affiliation(s)
- Martin Baron
- Faculty of Life Sciences, University of Manchester, Michael Smith Building, Oxford Road, Manchester M13 9PT, UK.
| |
Collapse
|
139
|
Larimore J, Tornieri K, Ryder PV, Gokhale A, Zlatic SA, Craige B, Lee JD, Talbot K, Pare JF, Smith Y, Faundez V. The schizophrenia susceptibility factor dysbindin and its associated complex sort cargoes from cell bodies to the synapse. Mol Biol Cell 2011; 22:4854-67. [PMID: 21998198 PMCID: PMC3237628 DOI: 10.1091/mbc.e11-07-0592] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2011] [Revised: 09/08/2011] [Accepted: 10/07/2011] [Indexed: 11/11/2022] Open
Abstract
Dysbindin assembles into the biogenesis of lysosome-related organelles complex 1 (BLOC-1), which interacts with the adaptor protein complex 3 (AP-3), mediating a common endosome-trafficking route. Deficiencies in AP-3 and BLOC-1 affect synaptic vesicle composition. However, whether AP-3-BLOC-1-dependent sorting events that control synapse membrane protein content take place in cell bodies upstream of nerve terminals remains unknown. We tested this hypothesis by analyzing the targeting of phosphatidylinositol-4-kinase type II α (PI4KIIα), a membrane protein present in presynaptic and postsynaptic compartments. PI4KIIα copurified with BLOC-1 and AP-3 in neuronal cells. These interactions translated into a decreased PI4KIIα content in the dentate gyrus of dysbindin-null BLOC-1 deficiency and AP-3-null mice. Reduction of PI4KIIα in the dentate reflects a failure to traffic from the cell body. PI4KIIα was targeted to processes in wild-type primary cultured cortical neurons and PC12 cells but failed to reach neurites in cells lacking either AP-3 or BLOC-1. Similarly, disruption of an AP-3-sorting motif in PI4KIIα impaired its sorting into processes of PC12 and primary cultured cortical neuronal cells. Our findings indicate a novel vesicle transport mechanism requiring BLOC-1 and AP-3 complexes for cargo sorting from neuronal cell bodies to neurites and nerve terminals.
Collapse
Affiliation(s)
| | - Karine Tornieri
- Department of Cell Biology, Emory University, Atlanta, GA 30322
| | - Pearl V. Ryder
- Department of Cell Biology, Emory University, Atlanta, GA 30322
- Graduate Program in Biochemistry, Cell, and Developmental Biology, Emory University, Atlanta, GA 30322
| | - Avanti Gokhale
- Department of Cell Biology, Emory University, Atlanta, GA 30322
| | - Stephanie A. Zlatic
- Department of Cell Biology, Emory University, Atlanta, GA 30322
- Graduate Program in Biochemistry, Cell, and Developmental Biology, Emory University, Atlanta, GA 30322
| | - Branch Craige
- Department of Cell Biology, Emory University, Atlanta, GA 30322
- Graduate Program in Biochemistry, Cell, and Developmental Biology, Emory University, Atlanta, GA 30322
| | - Joshua D. Lee
- Center for Neurobiology and Behavior, Department of Psychiatry, University of Pennsylvania, Philadelphia, PA 19104
| | - Konrad Talbot
- Center for Neurobiology and Behavior, Department of Psychiatry, University of Pennsylvania, Philadelphia, PA 19104
| | | | - Yoland Smith
- Department of Neurology and Yerkes National Primate Research Center
| | - Victor Faundez
- Department of Cell Biology, Emory University, Atlanta, GA 30322
- Graduate Program in Biochemistry, Cell, and Developmental Biology, Emory University, Atlanta, GA 30322
- Center for Neurodegenerative Disease, Emory University, Atlanta, GA 30322
| |
Collapse
|
140
|
van Weering JRT, Verkade P, Cullen PJ. SNX-BAR-mediated endosome tubulation is co-ordinated with endosome maturation. Traffic 2011; 13:94-107. [PMID: 21973056 DOI: 10.1111/j.1600-0854.2011.01297.x] [Citation(s) in RCA: 123] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Endosomal sorting is essential for cell homeostasis. Proteins targeted for degradation are retained in the maturing endosome vacuole while others are recycled to the cell surface or sorted to the biosynthetic pathway via tubular transport carriers. Sorting nexin (SNX) proteins containing a BAR (for Bin-Amphiphysin-Rvs) domain are key regulators of phosphoinositide-mediated, tubular-based endosomal sorting, but how such sorting is co-ordinated with endosomal maturation is not known. Here, using well-defined Rab GTPases as endosomal compartment markers, we have analyzed the localization of SNX1 [endosome-to-trans-Golgi network (TGN) transport as part of the SNX-BAR-retromer complex], SNX4 (cargo-recycling from endosomes to the plasma membrane) and SNX8 (endosomes-to-TGN trafficking in a retromer-independent manner). We show that these SNX-BARs are primarily localized to early endosomes, but display the highest frequency of tubule formation at the moment of early-to-late endosome transition: the Rab5-to-Rab7 switch. Perturbing this switch shifts SNX-BAR tubulation to early endosomes, resulting in SNX1-decorated tubules that lack retromer components VPS26 and VPS35, suggesting that both early and late endosomal characteristics of the endosome are important for SNX-BAR-retromer-tubule formation. We also establish that SNX4, but not SNX1 and SNX8, is associated with the Rab11-recycling endosomes and that a high frequency of SNX4-mediated tubule formation is observed as endosomes undergo Rab4-to-Rab11 transition. Our study therefore provides evidence for fine-tuning between the processes of endosomal maturation and the formation of endosomal tubules. As tubulation is required for SNX1-, SNX4- and SNX8-mediated sorting, these data reveal a previously unrecognized co-ordination between maturation and tubular-based sorting.
Collapse
Affiliation(s)
- Jan R T van Weering
- Henry Wellcome Integrated Signalling Laboratories, School of Biochemistry, Medical Sciences Building, University of Bristol, University Walk, Bristol, UK
| | | | | |
Collapse
|
141
|
Huang G, Fang J, Sant'Anna C, Li ZH, Wellems DL, Rohloff P, Docampo R. Adaptor protein-3 (AP-3) complex mediates the biogenesis of acidocalcisomes and is essential for growth and virulence of Trypanosoma brucei. J Biol Chem 2011; 286:36619-30. [PMID: 21880705 PMCID: PMC3196089 DOI: 10.1074/jbc.m111.284661] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2011] [Revised: 08/24/2011] [Indexed: 12/19/2022] Open
Abstract
Acidocalcisomes are acidic calcium and polyphosphate storage organelles found in a diverse range of organisms. Here we present evidence that the biogenesis of acidocalcisomes in Trypanosoma brucei is linked to the expression of adaptor protein-3 (AP-3) complex. Localization studies in cell lines expressing β3 and δ subunits of AP-3 fused to epitope tags revealed their partial co-localization with the vacuolar proton pyrophosphatase, a marker of acidocalcisomes, with the Golgi marker Golgi reassembly and stacking protein, and with antibodies against the small GTPase Rab11. Ablation of the β3 subunit by RNA interference (RNAi) resulted in disappearance of acidocalcisomes from both procyclic and bloodstream form trypanosomes, as revealed by immmunofluorescence and electron microscopy assays, with no alterations in trafficking of different markers to lysosomes. Knockdown of the β3 subunit resulted in lower acidic calcium, pyrophosphate, and polyphosphate content as well as defects in growth in culture, resistance to osmotic stress, and virulence in mice. Similar results were obtained by knocking down the expression of the δ subunit of AP-3. These results indicate that AP-3 is essential for the biogenesis of acidocalcisomes and for growth and virulence of T. brucei.
Collapse
Affiliation(s)
- Guozhong Huang
- From the Center for Tropical and Emerging Global Diseases and Department of Cellular Biology, University of Georgia, Athens, Georgia 30602
| | - Jianmin Fang
- From the Center for Tropical and Emerging Global Diseases and Department of Cellular Biology, University of Georgia, Athens, Georgia 30602
| | - Celso Sant'Anna
- From the Center for Tropical and Emerging Global Diseases and Department of Cellular Biology, University of Georgia, Athens, Georgia 30602
| | - Zhu-Hong Li
- From the Center for Tropical and Emerging Global Diseases and Department of Cellular Biology, University of Georgia, Athens, Georgia 30602
| | - Dianne L. Wellems
- From the Center for Tropical and Emerging Global Diseases and Department of Cellular Biology, University of Georgia, Athens, Georgia 30602
| | - Peter Rohloff
- From the Center for Tropical and Emerging Global Diseases and Department of Cellular Biology, University of Georgia, Athens, Georgia 30602
| | - Roberto Docampo
- From the Center for Tropical and Emerging Global Diseases and Department of Cellular Biology, University of Georgia, Athens, Georgia 30602
| |
Collapse
|
142
|
Hirst J, D. Barlow L, Francisco GC, Sahlender DA, Seaman MNJ, Dacks JB, Robinson MS. The fifth adaptor protein complex. PLoS Biol 2011; 9:e1001170. [PMID: 22022230 PMCID: PMC3191125 DOI: 10.1371/journal.pbio.1001170] [Citation(s) in RCA: 214] [Impact Index Per Article: 16.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2011] [Accepted: 08/30/2011] [Indexed: 11/18/2022] Open
Abstract
Adaptor protein (AP) complexes sort cargo into vesicles for transport from one membrane compartment of the cell to another. Four distinct AP complexes have been identified, which are present in most eukaryotes. We report the existence of a fifth AP complex, AP-5. Tagged AP-5 localises to a late endosomal compartment in HeLa cells. AP-5 does not associate with clathrin and is insensitive to brefeldin A. Knocking down AP-5 subunits interferes with the trafficking of the cation-independent mannose 6-phosphate receptor and causes the cell to form swollen endosomal structures with emanating tubules. AP-5 subunits can be found in all five eukaryotic supergroups, but they have been co-ordinately lost in many organisms. Concatenated phylogenetic analysis provides robust resolution, for the first time, into the evolutionary order of emergence of the adaptor subunit families, showing AP-3 as the basal complex, followed by AP-5, AP-4, and AP-1 and AP-2. Thus, AP-5 is an evolutionarily ancient complex, which is involved in endosomal sorting, and which has links with hereditary spastic paraplegia. Adaptor protein (AP) complexes facilitate the trafficking of cargo from one membrane compartment of the cell to another by recruiting other proteins to particular types of vesicles. For over 10 years, it has been assumed that there are four, and only four, distinct AP complexes in eukaryotic cells. We report the existence of a fifth AP complex, AP-5. Immunolocalisation and RNAi knockdown experiments both indicate that AP-5 is involved in trafficking proteins from endosomes towards other membranous compartments. There are genetic links between AP-5 and hereditary spastic paraplegia, a group of human genetic disorders characterised by progressive spasticity in the lower limbs. Phylogenetic analyses indicate that AP-5 was already present in the last eukaryotic common ancestor over a billion years ago.
Collapse
Affiliation(s)
- Jennifer Hirst
- University of Cambridge, Cambridge Institute for Medical Research, Cambridge, United Kingdom
| | - Lael D. Barlow
- Department of Cell Biology, University of Alberta, Edmonton, Canada
| | | | - Daniela A. Sahlender
- University of Cambridge, Cambridge Institute for Medical Research, Cambridge, United Kingdom
| | - Matthew N. J. Seaman
- University of Cambridge, Cambridge Institute for Medical Research, Cambridge, United Kingdom
| | - Joel B. Dacks
- Department of Cell Biology, University of Alberta, Edmonton, Canada
- * E-mail: (MSR); (JBD)
| | - Margaret S. Robinson
- University of Cambridge, Cambridge Institute for Medical Research, Cambridge, United Kingdom
- * E-mail: (MSR); (JBD)
| |
Collapse
|
143
|
Autophagosome precursor maturation requires homotypic fusion. Cell 2011; 146:303-17. [PMID: 21784250 PMCID: PMC3171170 DOI: 10.1016/j.cell.2011.06.023] [Citation(s) in RCA: 297] [Impact Index Per Article: 22.8] [Reference Citation Analysis] [Abstract] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2010] [Revised: 01/27/2011] [Accepted: 06/13/2011] [Indexed: 11/23/2022]
Abstract
Autophagy is a catabolic process in which lysosomes degrade intracytoplasmic contents transported in double-membraned autophagosomes. Autophagosomes are formed by the elongation and fusion of phagophores, which can be derived from preautophagosomal structures coming from the plasma membrane and other sites like the endoplasmic reticulum and mitochondria. The mechanisms by which preautophagosomal structures elongate their membranes and mature toward fully formed autophagosomes still remain unknown. Here, we show that the maturation of the early Atg16L1 precursors requires homotypic fusion, which is essential for subsequent autophagosome formation. Atg16L1 precursor homotypic fusion depends on the SNARE protein VAMP7 together with partner SNAREs. Atg16L1 precursor homotypic fusion is a critical event in the early phases of autophagy that couples membrane acquisition and autophagosome biogenesis, as this step regulates the size of the vesicles, which in turn appears to influence their subsequent maturation into LC3-positive autophagosomes.
Collapse
|
144
|
Scheuring D, Viotti C, Krüger F, Künzl F, Sturm S, Bubeck J, Hillmer S, Frigerio L, Robinson DG, Pimpl P, Schumacher K. Multivesicular bodies mature from the trans-Golgi network/early endosome in Arabidopsis. THE PLANT CELL 2011; 23:3463-81. [PMID: 21934143 PMCID: PMC3203422 DOI: 10.1105/tpc.111.086918] [Citation(s) in RCA: 200] [Impact Index Per Article: 15.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/30/2011] [Revised: 08/19/2011] [Accepted: 08/31/2011] [Indexed: 05/17/2023]
Abstract
The plant trans-Golgi network/early endosome (TGN/EE) is a major hub for secretory and endocytic trafficking with complex molecular mechanisms controlling sorting and transport of cargo. Vacuolar transport from the TGN/EE to multivesicular bodies/late endosomes (MVBs/LEs) is assumed to occur via clathrin-coated vesicles, although direct proof for their participation is missing. Here, we present evidence that post-TGN transport toward lytic vacuoles occurs independently of clathrin and that MVBs/LEs are derived from the TGN/EE through maturation. We show that the V-ATPase inhibitor concanamycin A significantly reduces the number of MVBs and causes TGN and MVB markers to colocalize in Arabidopsis thaliana roots. Ultrastructural analysis reveals the formation of MVBs from the TGN/EE and their fusion with the vacuole. The localization of the ESCRT components VPS28, VPS22, and VPS2 at the TGN/EE and MVBs/LEs indicates that the formation of intraluminal vesicles starts already at the TGN/EE. Accordingly, a dominant-negative mutant of VPS2 causes TGN and MVB markers to colocalize and blocks vacuolar transport. RNA interference-mediated knockdown of the annexin ANNAT3 also yields the same phenotype. Together, these data indicate that MVBs originate from the TGN/EE in a process that requires the action of ESCRT for the formation of intraluminal vesicles and annexins for the final step of releasing MVBs as a transport carrier to the vacuole.
Collapse
Affiliation(s)
- David Scheuring
- Plant Cell Biology, Centre for Organismal Studies, University of Heidelberg, 69120 Heidelberg, Germany
| | - Corrado Viotti
- Developmental Biology of Plants, Centre for Organismal Studies, University of Heidelberg, 69120 Heidelberg, Germany
| | - Falco Krüger
- Plant Cell Biology, Centre for Organismal Studies, University of Heidelberg, 69120 Heidelberg, Germany
| | - Fabian Künzl
- Developmental Genetics, Centre for Plant Molecular Biology, University of Tübingen, 72076 Tuebingen, Germany
| | - Silke Sturm
- Plant Cell Biology, Centre for Organismal Studies, University of Heidelberg, 69120 Heidelberg, Germany
| | - Julia Bubeck
- Developmental Biology of Plants, Centre for Organismal Studies, University of Heidelberg, 69120 Heidelberg, Germany
| | - Stefan Hillmer
- Plant Cell Biology, Centre for Organismal Studies, University of Heidelberg, 69120 Heidelberg, Germany
| | - Lorenzo Frigerio
- Department of Biological Sciences, University of Warwick, Coventry CV4 7AL, United Kingdom
| | - David G. Robinson
- Plant Cell Biology, Centre for Organismal Studies, University of Heidelberg, 69120 Heidelberg, Germany
| | - Peter Pimpl
- Plant Cell Biology, Centre for Organismal Studies, University of Heidelberg, 69120 Heidelberg, Germany
- Developmental Genetics, Centre for Plant Molecular Biology, University of Tübingen, 72076 Tuebingen, Germany
- Address correspondence to
| | - Karin Schumacher
- Developmental Biology of Plants, Centre for Organismal Studies, University of Heidelberg, 69120 Heidelberg, Germany
| |
Collapse
|
145
|
Jelcic I, Reichel J, Schlude C, Treutler E, Sinzger C, Steinle A. The polymorphic HCMV glycoprotein UL20 is targeted for lysosomal degradation by multiple cytoplasmic dileucine motifs. Traffic 2011; 12:1444-56. [PMID: 21689255 DOI: 10.1111/j.1600-0854.2011.01236.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Human cytomegalovirus (HCMV) is a widespread and persistent beta-herpesvirus. The large DNA genome of HCMV encodes many proteins that are non-essential for viral replication including numerous proteins subverting host immunosurveillance. One of them is the barely characterized UL20, which is encoded adjacent to the well-defined immunoevasins UL16 and UL18. UL20 is a type I transmembrane glycoprotein with an immunoglobulin-like ectodomain that is highly polymorphic among HCMV strains. Here, we show that the homodimeric UL20, by virtue of its cytoplasmic domain, does not reach the cell surface but is targeted to endosomes and lysosomes. Accordingly, UL20 exhibits a short half-life because of rapid lysosomal degradation. Trafficking of UL20 to lysosomes is determined by several, independently functioning dileucine-based sorting motifs in the cytoplasmic domain of UL20 and involves the adaptor protein (AP) complex AP-1. Combined substitution of three dileucine motifs allowed strong cell surface expression of UL20 comparable to UL20 mutants lacking the cytoplasmic tail. Finally, we show that the intracellularly located UL20 also is subject to lysosomal degradation in the context of viral infection. Altogether, from these data, we hypothesize that UL20 is destined to efficiently sequester yet-to-be defined cellular proteins for degradation in lysosomes.
Collapse
Affiliation(s)
- Ivan Jelcic
- Institute for Molecular Medicine, Goethe-University Frankfurt am Main, 60590 Frankfurt am Main, Germany
| | | | | | | | | | | |
Collapse
|
146
|
Abstract
Since its first visualization in 1898, the Golgi has been a topic of intense morphological research. A typical mammalian Golgi consists of a pile of stapled cisternae, the Golgi stack, which is a key station for modification of newly synthesized proteins and lipids. Distinct stacks are interconnected by tubules to form the Golgi ribbon. At the entrance site of the Golgi, the cis-Golgi, vesicular tubular clusters (VTCs) form the intermediate between the endoplasmic reticulum and the Golgi stack. At the exit site of the Golgi, the trans-Golgi, the trans-Golgi network (TGN) is the major site of sorting proteins to distinct cellular locations. Golgi functioning can only be understood in light of its complex architecture, as was revealed by a range of distinct electron microscopy (EM) approaches. In this article, a general concept of mammalian Golgi architecture, including VTCs and the TGN, is described.
Collapse
Affiliation(s)
- Judith Klumperman
- Department of Cell Biology, University Medical Center Utrecht, Heidelberglaan 100, 3584CX Utrecht, The Netherlands.
| |
Collapse
|
147
|
Hayes MJ, Bryon K, Satkurunathan J, Levine TP. Yeast homologues of three BLOC-1 subunits highlight KxDL proteins as conserved interactors of BLOC-1. Traffic 2011; 12:260-8. [PMID: 21159114 DOI: 10.1111/j.1600-0854.2010.01151.x] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Biogenesis of lysosome-related organelle complex-1 (BLOC-1) is one of the four multi-subunit complexes implicated in sorting cargo to lysosome-related organelles, as loss of function of any of these complexes causes Hermansky-Pudlak syndrome. Eight subunits of BLOC-1 interact with each other and with many other proteins. Identifying new interactors of BLOC-1 will increase understanding of its mechanism of action, and studies in model organisms are useful for finding such interactors. PSI-BLAST searches identify homologues in diverse model organisms, but there are significant gaps for BLOC-1, with none of its eight subunits found in Saccharomyces cerevisiae. Here we use more sensitive searches to identify distant homologues for three BLOC-1 subunits in S. cerevisiae: Blos1, snapin and cappuccino (cno). Published data on protein interactions show that in yeast these are likely to form a complex with three other proteins. One of these is the yeast homologue of the previously uncharacterized KxDL protein, which also interacts with Blos1 and cno in higher eukaryotes, suggesting that KxDL proteins are key interactors with BLOC-1.
Collapse
Affiliation(s)
- Matthew J Hayes
- Department of Cell Biology, UCL Institute of Ophthalmology, Bath Street, London EC1V9EL, UK
| | | | | | | |
Collapse
|
148
|
Laulagnier K, Schieber NL, Maritzen T, Haucke V, Parton RG, Gruenberg J. Role of AP1 and Gadkin in the traffic of secretory endo-lysosomes. Mol Biol Cell 2011; 22:2068-82. [PMID: 21525240 PMCID: PMC3113771 DOI: 10.1091/mbc.e11-03-0193] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2011] [Revised: 04/12/2011] [Accepted: 04/19/2011] [Indexed: 11/11/2022] Open
Abstract
Whereas lysosome-related organelles (LRO) of specialized cells display both exocytic and endocytic features, lysosomes in nonspecialized cells can also acquire the property to fuse with the plasma membrane upon an acute rise in cytosolic calcium. Here, we characterize this unconventional secretory pathway in fibroblast-like cells, by monitoring the appearance of Lamp1 on the plasma membrane and the release of lysosomal enzymes into the medium. After sequential ablation of endocytic compartments in living cells, we find that donor membranes primarily derive from a late compartment, but that an early compartment is also involved. Strikingly, this endo-secretory process is not affected by treatments that inhibit endosome dynamics (microtubule depolymerization, cholesterol accumulation, overexpression of Rab7 or its effector Rab-interacting lysosomal protein [RILP], overexpression of Rab5 mutants), but depends on Rab27a, a GTPase involved in LRO secretion, and is controlled by F-actin. Moreover, we find that this unconventional endo-secretory pathway requires the adaptor protein complexes AP1, Gadkin (which recruits AP1 by binding to the γ1 subunit), and AP2, but not AP3. We conclude that a specific fraction of the AP2-derived endocytic pathway is dedicated to secretory purposes under the control of AP1 and Gadkin.
Collapse
Affiliation(s)
- Karine Laulagnier
- Department of Biochemistry, University of Geneva, 1211-Geneva-4, Switzerland
| | - Nicole L. Schieber
- Institute for Molecular Bioscience and Center for Microscopy and Microanalysis, The University of Queensland, Brisbane 4072, Australia
| | - Tanja Maritzen
- Laboratory of Membrane Biochemistry, Freie Universitaet Berlin, 14195 Berlin, Germany
| | - Volker Haucke
- Laboratory of Membrane Biochemistry, Freie Universitaet Berlin, 14195 Berlin, Germany
| | - Robert G. Parton
- Institute for Molecular Bioscience and Center for Microscopy and Microanalysis, The University of Queensland, Brisbane 4072, Australia
| | - Jean Gruenberg
- Department of Biochemistry, University of Geneva, 1211-Geneva-4, Switzerland
| |
Collapse
|
149
|
Ebrahim R, Thilo L. Kinetic evidence that newly-synthesized endogenous lysosome-associated membrane protein-1 (LAMP-1) first transits early endosomes before it is delivered to lysosomes. Mol Membr Biol 2011; 28:227-42. [PMID: 21457058 DOI: 10.3109/09687688.2011.572567] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
After de novo synthesis of lysosome-associated membrane proteins (LAMPs), they are sorted in the trans-Golgi network (TGN) for delivery to lysosomes. Opposing views prevail on whether LAMPs are targeted to lysosomes directly, or indirectly via prelysosomal stages of the endocytic pathway, in particular early endosomes. Conflicting evidence is based on kinetic measurements with too limited quantitative data for sufficient temporal and organellar resolution. Using cells of the mouse macrophage cell line, P338D(1), this study presents detailed kinetic data that describe the extent of, and time course for, the appearance of newly-synthesized LAMP-1 in organelles of the endocytic pathway, which had been loaded selectively with horse-radish peroxidase (HRP) by appropriate periods of endocytosis. After a 5-min pulse of metabolic labelling, LAMP-1 was trapped in the respective organelles by HRP-catalyzed crosslinking with membrane-permeable diaminobenzidine (DAB). These kinetic observations provide sufficient quantitative evidence that in P338D(1) cells the bulk of newly-synthesized endogenous LAMP-1 first appeared in early endosomes, before it was delivered to late endosomes and lysosomes about 25 min later.
Collapse
Affiliation(s)
- Roshan Ebrahim
- Department of Medical Biochemistry, Faculty of Health Sciences, University of Cape Town, South Africa.
| | | |
Collapse
|
150
|
Burgess J, Jauregui M, Tan J, Rollins J, Lallet S, Leventis PA, Boulianne GL, Chang HC, Le Borgne R, Krämer H, Brill JA. AP-1 and clathrin are essential for secretory granule biogenesis in Drosophila. Mol Biol Cell 2011; 22:2094-105. [PMID: 21490149 PMCID: PMC3113773 DOI: 10.1091/mbc.e11-01-0054] [Citation(s) in RCA: 66] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Regulated secretion of hormones, digestive enzymes, and other biologically active molecules requires the formation of secretory granules. Clathrin and the clathrin adaptor protein complex 1 (AP-1) are necessary for maturation of exocrine, endocrine, and neuroendocrine secretory granules. However, the initial steps of secretory granule biogenesis are only minimally understood. Powerful genetic approaches available in the fruit fly Drosophila melanogaster were used to investigate the molecular pathway for biogenesis of the mucin-containing "glue granules" that form within epithelial cells of the third-instar larval salivary gland. Clathrin and AP-1 colocalize at the trans-Golgi network (TGN) and clathrin recruitment requires AP-1. Furthermore, clathrin and AP-1 colocalize with secretory cargo at the TGN and on immature granules. Finally, loss of clathrin or AP-1 leads to a profound block in secretory granule formation. These findings establish a novel role for AP-1- and clathrin-dependent trafficking in the biogenesis of mucin-containing secretory granules.
Collapse
Affiliation(s)
- Jason Burgess
- Department of Molecular Genetics, University of Toronto, Ontario, Canada
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|