1
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Zlamalova E, Rodger C, Greco F, Cheers SR, Kleniuk J, Nadadhur AG, Kadlecova Z, Reid E. Atlastin-1 regulates endosomal tubulation and lysosomal proteolysis in human cortical neurons. Neurobiol Dis 2024; 199:106556. [PMID: 38851544 PMCID: PMC11300884 DOI: 10.1016/j.nbd.2024.106556] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2024] [Revised: 06/04/2024] [Accepted: 06/05/2024] [Indexed: 06/10/2024] Open
Abstract
Mutation of the ATL1 gene is one of the most common causes of hereditary spastic paraplegia (HSP), a group of genetic neurodegenerative conditions characterised by distal axonal degeneration of the corticospinal tract axons. Atlastin-1, the protein encoded by ATL1, is one of three mammalian atlastins, which are homologous dynamin-like GTPases that control endoplasmic reticulum (ER) morphology by fusing tubules to form the three-way junctions that characterise ER networks. However, it is not clear whether atlastin-1 is required for correct ER morphology in human neurons and if so what the functional consequences of lack of atlastin-1 are. Using CRISPR-inhibition we generated human cortical neurons lacking atlastin-1. We demonstrate that ER morphology was altered in these neurons, with a reduced number of three-way junctions. Neurons lacking atlastin-1 had longer endosomal tubules, suggestive of defective tubule fission. This was accompanied by reduced lysosomal proteolytic capacity. As well as demonstrating that atlastin-1 is required for correct ER morphology in human neurons, our results indicate that lack of a classical ER-shaping protein such as atlastin-1 may cause altered endosomal tubulation and lysosomal proteolytic dysfunction. Furthermore, they strengthen the idea that defective lysosome function contributes to the pathogenesis of a broad group of HSPs, including those where the primary localisation of the protein involved is not at the endolysosomal system.
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Affiliation(s)
- Eliska Zlamalova
- Cambridge Institute for Medical Research, University of Cambridge, Cambridge, UK; Department of Medical Genetics, University of Cambridge, Cambridge, UK
| | - Catherine Rodger
- Cambridge Institute for Medical Research, University of Cambridge, Cambridge, UK; Department of Medical Genetics, University of Cambridge, Cambridge, UK
| | - Francesca Greco
- Department of Biotechnology, University of Verona, Verona, Italy
| | - Samuel R Cheers
- Cambridge Institute for Medical Research, University of Cambridge, Cambridge, UK; Department of Medical Genetics, University of Cambridge, Cambridge, UK
| | - Julia Kleniuk
- Cambridge Institute for Medical Research, University of Cambridge, Cambridge, UK; Department of Medical Genetics, University of Cambridge, Cambridge, UK
| | - Aishwarya G Nadadhur
- Cambridge Institute for Medical Research, University of Cambridge, Cambridge, UK; Department of Medical Genetics, University of Cambridge, Cambridge, UK
| | - Zuzana Kadlecova
- Cambridge Institute for Medical Research, University of Cambridge, Cambridge, UK
| | - Evan Reid
- Cambridge Institute for Medical Research, University of Cambridge, Cambridge, UK; Department of Medical Genetics, University of Cambridge, Cambridge, UK.
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2
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Choi J, Jang H, Xuan Z, Park D. Emerging roles of ATG9/ATG9A in autophagy: implications for cell and neurobiology. Autophagy 2024:1-15. [PMID: 39099167 DOI: 10.1080/15548627.2024.2384349] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2024] [Revised: 07/01/2024] [Accepted: 07/22/2024] [Indexed: 08/06/2024] Open
Abstract
Atg9, the only transmembrane protein among many autophagy-related proteins, was first identified in the year 2000 in yeast. Two homologs of Atg9, ATG9A and ATG9B, have been found in mammals. While ATG9B shows a tissue-specific expression pattern, such as in the placenta and pituitary gland, ATG9A is ubiquitously expressed. Additionally, ATG9A deficiency leads to severe defects not only at the molecular and cellular levels but also at the organismal level, suggesting key and fundamental roles for ATG9A. The subcellular localization of ATG9A on small vesicles and its functional relevance to autophagy have suggested a potential role for ATG9A in the lipid supply during autophagosome biogenesis. Nevertheless, the precise role of ATG9A in the autophagic process has remained a long-standing mystery, especially in neurons. Recent findings, however, including structural, proteomic, and biochemical analyses, have provided new insights into its function in the expansion of the phagophore membrane. In this review, we aim to understand various aspects of ATG9 (in invertebrates and plants)/ATG9A (in mammals), including its localization, trafficking, and other functions, in nonneuronal cells and neurons by comparing recent discoveries related to ATG9/ATG9A and proposing directions for future research.Abbreviation: AP-4: adaptor protein complex 4; ATG: autophagy related; cKO: conditional knockout; CLA-1: CLArinet (functional homolog of cytomatrix at the active zone proteins piccolo and fife); cryo-EM: cryogenic electron microscopy; ER: endoplasmic reticulum; KO: knockout; PAS: phagophore assembly site; PtdIns3K: class III phosphatidylinositol 3-kinase; PtdIns3P: phosphatidylinositol-3-phosphate; RB1CC1/FIP200: RB1 inducible coiled-coil 1; SV: synaptic vesicle; TGN: trans-Golgi network; ULK: unc-51 like autophagy activating kinase; WIPI2: WD repeat domain, phosphoinositide interacting 2.
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Affiliation(s)
- Jiyoung Choi
- Department of Medical and Biological Sciences, The Catholic University of Korea, Bucheon, South Korea
- Department of Biotechnology, The Catholic University of Korea, Bucheon, South Korea
| | - Haeun Jang
- Department of Medical and Biological Sciences, The Catholic University of Korea, Bucheon, South Korea
| | - Zhao Xuan
- School of Biology and Ecology, University of Maine, Orono, ME, USA
| | - Daehun Park
- Department of Medical and Biological Sciences, The Catholic University of Korea, Bucheon, South Korea
- Department of Biotechnology, The Catholic University of Korea, Bucheon, South Korea
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3
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Holzer E, Martens S, Tulli S. The Role of ATG9 Vesicles in Autophagosome Biogenesis. J Mol Biol 2024; 436:168489. [PMID: 38342428 DOI: 10.1016/j.jmb.2024.168489] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2023] [Revised: 02/02/2024] [Accepted: 02/07/2024] [Indexed: 02/13/2024]
Abstract
Autophagy mediates the degradation and recycling of cellular material in the lysosomal system. Dysfunctional autophagy is associated with a plethora of diseases including uncontrolled infections, cancer and neurodegeneration. In macroautophagy (hereafter autophagy) this material is encapsulated in double membrane vesicles, the autophagosomes, which form upon induction of autophagy. The precursors to autophagosomes, referred to as phagophores, first appear as small flattened membrane cisternae, which gradually enclose the cargo material as they grow. The assembly of phagophores during autophagy initiation has been a major subject of investigation over the past decades. A special focus has been ATG9, the only conserved transmembrane protein among the core machinery. The majority of ATG9 localizes to small Golgi-derived vesicles. Here we review the recent advances and breakthroughs regarding our understanding of how ATG9 and the vesicles it resides in serve to assemble the autophagy machinery and to establish membrane contact sites for autophagosome biogenesis. We also highlight open questions in the field that need to be addressed in the years to come.
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Affiliation(s)
- Elisabeth Holzer
- Max Perutz Labs, Vienna BioCenter Campus (VBC), Vienna, Austria; University of Vienna, Max Perutz Labs, Department of Biochemistry and Cell Biology, Vienna, Austria; Vienna BioCenter PhD Program, Doctoral School of the University of Vienna and Medical University of Vienna, Campus-Vienna-Biocenter 1, Vienna, Austria.
| | - Sascha Martens
- Max Perutz Labs, Vienna BioCenter Campus (VBC), Vienna, Austria; University of Vienna, Max Perutz Labs, Department of Biochemistry and Cell Biology, Vienna, Austria.
| | - Susanna Tulli
- Max Perutz Labs, Vienna BioCenter Campus (VBC), Vienna, Austria; University of Vienna, Max Perutz Labs, Department of Biochemistry and Cell Biology, Vienna, Austria.
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4
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Paumier JM, Gowrishankar S. Disruptions in axonal lysosome transport and its contribution to neurological disease. Curr Opin Cell Biol 2024; 89:102382. [PMID: 38905918 DOI: 10.1016/j.ceb.2024.102382] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2024] [Revised: 05/23/2024] [Accepted: 05/28/2024] [Indexed: 06/23/2024]
Abstract
Lysosomes are central to the maintenance of protein and organelle homeostasis in cells. Optimal lysosome function is particularly critical for neurons which are long-lived, non-dividing and highly polarized with specialized compartments such as axons and dendrites with distinct architecture, cargo, and turnover requirements. In recent years, there has been a growing appreciation for the role played by axonal lysosome transport in regulating neuronal development, its maintenance and functioning. Perturbations to optimal axonal lysosome abundance leading to either strong accumulations or dearth of lysosomes are both linked to altered neuronal health and functioning. In this review we highlight how two critical regulators of axonal lysosome transport and abundance, the small GTPase Arl8 and the adaptor protein JIP3, aid in maintaining axonal lysosome homeostasis and how alterations to their levels and activity could contribute to neurodevelopmental and neurodegenerative diseases.
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Affiliation(s)
- Jean-Michel Paumier
- Department of Anatomy and Cell Biology, University of Illinois Chicago, 808 S Wood St, Chicago, IL 60612, USA
| | - Swetha Gowrishankar
- Department of Anatomy and Cell Biology, University of Illinois Chicago, 808 S Wood St, Chicago, IL 60612, USA.
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5
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Orlowski A, Karippaparambil J, Paumier JM, Ghanta S, Pallares E, Tandukar J, Gao R, Gowrishankar S. Axonal organelle buildup from loss of AP-4 complex function causes exacerbation of amyloid plaque pathology and gliosis in Alzheimer's disease mouse model. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.03.31.587499. [PMID: 38617351 PMCID: PMC11014495 DOI: 10.1101/2024.03.31.587499] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/16/2024]
Abstract
Lysosomes and related precursor organelles robustly build up in swollen axons that surround amyloid plaques and disrupted axonal lysosome transport has been implicated in worsening Alzheimer's pathology. Our prior studies have revealed that loss of Adaptor protein-4 (AP-4) complex function, linked primarily to Spastic Paraplegia (HSP), leads to a similar build of lysosomes in structures we term "AP-4 dystrophies". Surprisingly, these AP-4 dystrophies were also characterized by enrichment of components of APP processing machinery, β-site cleaving enzyme 1 (BACE1) and Presenilin 2. Our studies examining whether the abnormal axonal lysosome build up resulting from AP-4 loss could lead to amyloidogenesis revealed that the loss of AP-4 complex function in an Alzheimer's disease model resulted in a strong increase in size and abundance of amyloid plaques in the hippocampus and corpus callosum as well as increased microglial association with the plaques. Interestingly, we found a further increase in enrichment of the secretase, BACE1, in the axonal swellings of the plaques of Alzheimer model mice lacking AP-4 complex compared to those having normal AP-4 complex function, suggestive of increased amyloidogenic processing under this condition. Additionally, the exacerbation of plaque pathology was region-specific as it did not increase in the cortex. The burden of the AP-4 linked axonal dystrophies/AP-4 dystrophies was higher in the corpus callosum and hippocampus compared to the cortex, establishing the critical role of AP-4 -dependent axonal lysosome transport and maturation in regulating amyloidogenic amyloid precursor protein processing.
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Affiliation(s)
- Alex Orlowski
- Department of Anatomy and Cell Biology, College of Medicine, University of Illinois Chicago, Chicago, IL 60612 USA
| | - Joseph Karippaparambil
- Department of Anatomy and Cell Biology, College of Medicine, University of Illinois Chicago, Chicago, IL 60612 USA
| | - Jean-Michel Paumier
- Department of Anatomy and Cell Biology, College of Medicine, University of Illinois Chicago, Chicago, IL 60612 USA
| | - Shraddha Ghanta
- Department of Anatomy and Cell Biology, College of Medicine, University of Illinois Chicago, Chicago, IL 60612 USA
| | - Eduardo Pallares
- Department of Anatomy and Cell Biology, College of Medicine, University of Illinois Chicago, Chicago, IL 60612 USA
| | - Jamuna Tandukar
- Department of Biological Sciences, College of Liberal Arts and Sciences, University of Illinois Chicago, Chicago, IL 60607 USA
| | - Ruixuan Gao
- Department of Biological Sciences, College of Liberal Arts and Sciences, University of Illinois Chicago, Chicago, IL 60607 USA
- Department of Chemistry, College of Liberal Arts and Sciences, University of Illinois Chicago, Chicago, IL 60607 USA
| | - Swetha Gowrishankar
- Department of Anatomy and Cell Biology, College of Medicine, University of Illinois Chicago, Chicago, IL 60612 USA
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6
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Caracci MO, Pizarro H, Alarcón-Godoy C, Fuentealba LM, Farfán P, De Pace R, Santibañez N, Cavieres VA, Pástor TP, Bonifacino JS, Mardones GA, Marzolo MP. The Reelin receptor ApoER2 is a cargo for the adaptor protein complex AP-4: Implications for Hereditary Spastic Paraplegia. Prog Neurobiol 2024; 234:102575. [PMID: 38281682 PMCID: PMC10979513 DOI: 10.1016/j.pneurobio.2024.102575] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2023] [Revised: 01/11/2024] [Accepted: 01/23/2024] [Indexed: 01/30/2024]
Abstract
Adaptor protein complex 4 (AP-4) is a heterotetrameric complex that promotes export of selected cargo proteins from the trans-Golgi network. Mutations in each of the AP-4 subunits cause a complicated form of Hereditary Spastic Paraplegia (HSP). Herein, we report that ApoER2, a receptor in the Reelin signaling pathway, is a cargo of the AP-4 complex. We identify the motif ISSF/Y within the ApoER2 cytosolic domain as necessary for interaction with the canonical signal-binding pocket of the µ4 (AP4M1) subunit of AP-4. AP4E1- knock-out (KO) HeLa cells and hippocampal neurons from Ap4e1-KO mice display increased co-localization of ApoER2 with Golgi markers. Furthermore, hippocampal neurons from Ap4e1-KO mice and AP4M1-KO human iPSC-derived cortical i3Neurons exhibit reduced ApoER2 protein expression. Analyses of biosynthetic transport of ApoER2 reveal differential post-Golgi trafficking of the receptor, with lower axonal distribution in KO compared to wild-type neurons, indicating a role of AP-4 and the ISSF/Y motif in the axonal localization of ApoER2. Finally, analyses of Reelin signaling in mouse hippocampal and human cortical KO neurons show that AP4 deficiency causes no changes in Reelin-dependent activation of the AKT pathway and only mild changes in Reelin-induced dendritic arborization, but reduces Reelin-induced ERK phosphorylation, CREB activation, and Golgi deployment. This work thus establishes ApoER2 as a novel cargo of the AP-4 complex, suggesting that defects in the trafficking of this receptor and in the Reelin signaling pathway could contribute to the pathogenesis of HSP caused by mutations in AP-4 subunits.
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Affiliation(s)
- Mario O Caracci
- Departamento de Biología Celular y Molecular, Facultad de Ciencias Biológicas, P. Universidad Católica de Chile, Santiago, Chile
| | - Héctor Pizarro
- Departamento de Biología Celular y Molecular, Facultad de Ciencias Biológicas, P. Universidad Católica de Chile, Santiago, Chile
| | - Carlos Alarcón-Godoy
- Departamento de Biología Celular y Molecular, Facultad de Ciencias Biológicas, P. Universidad Católica de Chile, Santiago, Chile
| | - Luz M Fuentealba
- Departamento de Biología Celular y Molecular, Facultad de Ciencias Biológicas, P. Universidad Católica de Chile, Santiago, Chile
| | - Pamela Farfán
- Departamento de Biología Celular y Molecular, Facultad de Ciencias Biológicas, P. Universidad Católica de Chile, Santiago, Chile
| | - Raffaella De Pace
- Neurosciences and Cellular and Structural Biology Division, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, USA
| | - Natacha Santibañez
- Instituto de Patología Animal, Facultad de Ciencias Veterinarias, Universidad Austral de Chile, Valdivia, Chile
| | - Viviana A Cavieres
- Departamento de Ciencias Biológicas y Químicas, Fac. Med y Ciencia, USS, Santiago, Chile
| | - Tammy P Pástor
- Escuela de Medicina, Facultad de Medicina y Ciencia, Universidad San Sebastián, Valdivia, Chile
| | - Juan S Bonifacino
- Neurosciences and Cellular and Structural Biology Division, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, USA
| | - Gonzalo A Mardones
- Escuela de Medicina, Facultad de Medicina y Ciencia, Universidad San Sebastián, Valdivia, Chile
| | - María-Paz Marzolo
- Departamento de Biología Celular y Molecular, Facultad de Ciencias Biológicas, P. Universidad Católica de Chile, Santiago, Chile.
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7
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Saffari A, Brechmann B, Böger C, Saber WA, Jumo H, Whye D, Wood D, Wahlster L, Alecu JE, Ziegler M, Scheffold M, Winden K, Hubbs J, Buttermore ED, Barrett L, Borner GHH, Davies AK, Ebrahimi-Fakhari D, Sahin M. High-content screening identifies a small molecule that restores AP-4-dependent protein trafficking in neuronal models of AP-4-associated hereditary spastic paraplegia. Nat Commun 2024; 15:584. [PMID: 38233389 PMCID: PMC10794252 DOI: 10.1038/s41467-023-44264-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2023] [Accepted: 12/06/2023] [Indexed: 01/19/2024] Open
Abstract
Unbiased phenotypic screens in patient-relevant disease models offer the potential to detect therapeutic targets for rare diseases. In this study, we developed a high-throughput screening assay to identify molecules that correct aberrant protein trafficking in adapter protein complex 4 (AP-4) deficiency, a rare but prototypical form of childhood-onset hereditary spastic paraplegia characterized by mislocalization of the autophagy protein ATG9A. Using high-content microscopy and an automated image analysis pipeline, we screened a diversity library of 28,864 small molecules and identified a lead compound, BCH-HSP-C01, that restored ATG9A pathology in multiple disease models, including patient-derived fibroblasts and induced pluripotent stem cell-derived neurons. We used multiparametric orthogonal strategies and integrated transcriptomic and proteomic approaches to delineate potential mechanisms of action of BCH-HSP-C01. Our results define molecular regulators of intracellular ATG9A trafficking and characterize a lead compound for the treatment of AP-4 deficiency, providing important proof-of-concept data for future studies.
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Affiliation(s)
- Afshin Saffari
- Department of Neurology & F.M. Kirby Neurobiology Center, Boston Children's Hospital, Harvard Medical School, Boston, MA, 02115, USA
- Division of Child Neurology and Inherited Metabolic Diseases, Heidelberg University Hospital, Heidelberg, Germany
| | - Barbara Brechmann
- Department of Neurology & F.M. Kirby Neurobiology Center, Boston Children's Hospital, Harvard Medical School, Boston, MA, 02115, USA
| | - Cedric Böger
- Department of Neurology & F.M. Kirby Neurobiology Center, Boston Children's Hospital, Harvard Medical School, Boston, MA, 02115, USA
| | - Wardiya Afshar Saber
- Department of Neurology & F.M. Kirby Neurobiology Center, Boston Children's Hospital, Harvard Medical School, Boston, MA, 02115, USA
| | - Hellen Jumo
- Department of Neurology & F.M. Kirby Neurobiology Center, Boston Children's Hospital, Harvard Medical School, Boston, MA, 02115, USA
- Rosamund Stone Zander Translational Neuroscience Center, Boston Children's Hospital, Harvard Medical School, Boston, MA, 02115, USA
| | - Dosh Whye
- Rosamund Stone Zander Translational Neuroscience Center, Boston Children's Hospital, Harvard Medical School, Boston, MA, 02115, USA
| | - Delaney Wood
- Rosamund Stone Zander Translational Neuroscience Center, Boston Children's Hospital, Harvard Medical School, Boston, MA, 02115, USA
| | - Lara Wahlster
- Department of Hematology & Oncology, Boston Children's Hospital & Dana-Farber Cancer Institute, Harvard Medical School, Boston, MA, 02115, USA
| | - Julian E Alecu
- Department of Neurology & F.M. Kirby Neurobiology Center, Boston Children's Hospital, Harvard Medical School, Boston, MA, 02115, USA
| | - Marvin Ziegler
- Department of Neurology & F.M. Kirby Neurobiology Center, Boston Children's Hospital, Harvard Medical School, Boston, MA, 02115, USA
| | - Marlene Scheffold
- Department of Neurology & F.M. Kirby Neurobiology Center, Boston Children's Hospital, Harvard Medical School, Boston, MA, 02115, USA
| | - Kellen Winden
- Department of Neurology & F.M. Kirby Neurobiology Center, Boston Children's Hospital, Harvard Medical School, Boston, MA, 02115, USA
| | - Jed Hubbs
- Rosamund Stone Zander Translational Neuroscience Center, Boston Children's Hospital, Harvard Medical School, Boston, MA, 02115, USA
| | - Elizabeth D Buttermore
- Rosamund Stone Zander Translational Neuroscience Center, Boston Children's Hospital, Harvard Medical School, Boston, MA, 02115, USA
| | - Lee Barrett
- Rosamund Stone Zander Translational Neuroscience Center, Boston Children's Hospital, Harvard Medical School, Boston, MA, 02115, USA
| | - Georg H H Borner
- Department of Proteomics and Signal Transduction, Max-Planck-Institute of Biochemistry, Martinsried, 82152, Germany
| | - Alexandra K Davies
- Department of Proteomics and Signal Transduction, Max-Planck-Institute of Biochemistry, Martinsried, 82152, Germany
- School of Biological Sciences, Faculty of Biology, Medicine and Health, Manchester Academic Health Science Centre, University of Manchester, Manchester, M13 9PT, UK
| | - Darius Ebrahimi-Fakhari
- Department of Neurology & F.M. Kirby Neurobiology Center, Boston Children's Hospital, Harvard Medical School, Boston, MA, 02115, USA.
- Movement Disorders Program, Department of Neurology, Boston Children's Hospital, Harvard Medical School, Boston, MA, 02115, USA.
| | - Mustafa Sahin
- Department of Neurology & F.M. Kirby Neurobiology Center, Boston Children's Hospital, Harvard Medical School, Boston, MA, 02115, USA
- Rosamund Stone Zander Translational Neuroscience Center, Boston Children's Hospital, Harvard Medical School, Boston, MA, 02115, USA
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8
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Kersten N, Farías GG. A voyage from the ER: spatiotemporal insights into polarized protein secretion in neurons. Front Cell Dev Biol 2023; 11:1333738. [PMID: 38188013 PMCID: PMC10766823 DOI: 10.3389/fcell.2023.1333738] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2023] [Accepted: 12/04/2023] [Indexed: 01/09/2024] Open
Abstract
To function properly, neurons must maintain a proteome that differs in their somatodendritic and axonal domain. This requires the polarized sorting of newly synthesized secretory and transmembrane proteins into different vesicle populations as they traverse the secretory pathway. Although the trans-Golgi-network is generally considered to be the main sorting hub, this sorting process may already begin at the ER and continue through the Golgi cisternae. At each step in the sorting process, specificity is conferred by adaptors, GTPases, tethers, and SNAREs. Besides this, local synthesis and unconventional protein secretion may contribute to the polarized proteome to enable rapid responses to stimuli. For some transmembrane proteins, some of the steps in the sorting process are well-studied. These will be highlighted here. The universal rules that govern polarized protein sorting remain unresolved, therefore we emphasize the need to approach this problem in an unbiased, top-down manner. Unraveling these rules will contribute to our understanding of neuronal development and function in health and disease.
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Affiliation(s)
- Noortje Kersten
- Cell Biology, Neurobiology and Biophysics, Department of Biology, Faculty of Science, Utrecht University, Utrecht, Netherlands
| | - Ginny G Farías
- Cell Biology, Neurobiology and Biophysics, Department of Biology, Faculty of Science, Utrecht University, Utrecht, Netherlands
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9
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Caracci MO, Pizarro H, Alarcón-Godoy C, Fuentealba LM, Farfán P, Pace RD, Santibañez N, Cavieres VA, Pástor TP, Bonifacino JS, Mardones GA, Marzolo MP. The Reelin Receptor ApoER2 is a Cargo for the Adaptor Protein Complex AP-4: Implications for Hereditary Spastic Paraplegia. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.12.21.572896. [PMID: 38187774 PMCID: PMC10769347 DOI: 10.1101/2023.12.21.572896] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/09/2024]
Abstract
Adaptor protein complex 4 (AP-4) is a heterotetrameric complex that promotes protein export from the trans -Golgi network. Mutations in each of the AP-4 subunits cause a complicated form of Hereditary Spastic Paraplegia (HSP). Herein, we report that ApoER2, a receptor in the Reelin signaling pathway, is a cargo of the AP-4 complex. We identify the motif ISSF/Y within the ApoER2 cytosolic domain as necessary for interaction with the canonical signal-binding pocket of the µ4 (AP4M1) subunit of AP-4. AP4E1 -knock-out (KO) HeLa cells and hippocampal neurons from Ap4e1 -KO mice display increased Golgi localization of ApoER2. Furthermore, hippocampal neurons from Ap4e1 -KO mice and AP4M1 -KO human iPSC-derived cortical i3Neurons exhibit reduced ApoER2 protein expression. Analyses of biosynthetic transport of ApoER2 reveal differential post-Golgi trafficking of the receptor, with lower axonal distribution in KO compared to wild-type neurons, indicating a role of AP-4 and the ISSF/Y motif in the axonal localization of ApoER2. Finally, analyses of Reelin signaling in mouse hippocampal and human cortical KO neurons show that AP4 deficiency causes no changes in Reelin-dependent activation of the AKT pathway and only mild changes in Reelin-induced dendritic arborization, but reduces Reelin-induced ERK phosphorylation, CREB activation, and Golgi deployment. Altogether, this work establishes ApoER2 as a novel cargo of the AP-4 complex, suggesting that defects in the trafficking of this receptor and in the Reelin signaling pathway could contribute to the pathogenesis of HSP caused by mutations in AP-4 subunits.
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10
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Li Y, Zhang C, Peng G. Ap4s1 truncation leads to axonal defects in a zebrafish model of spastic paraplegia 52. Int J Dev Neurosci 2023; 83:753-764. [PMID: 37767851 DOI: 10.1002/jdn.10303] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2023] [Revised: 08/11/2023] [Accepted: 09/08/2023] [Indexed: 09/29/2023] Open
Abstract
Biallelic mutations in AP4S1, the σ4 subunit of the adaptor protein complex 4 (AP-4), lead to autosomal recessive spastic paraplegia 52 (SPG52). It is a subtype of AP-4-associated hereditary spastic paraplegia (AP-4-HSP), a complex childhood-onset neurogenetic disease characterized by progressive spastic paraplegia of the lower limbs. This disease has so far lacked effective treatment, in part due to a lack of suitable animal models. Here, we used CRISPR/Cas9 technology to generate a truncation mutation in the ap4s1 gene in zebrafish. The ap4s1 truncation led to motor impairment, delayed neurodevelopment, and distal axonal degeneration. This animal model is useful for further research into AP-4 and AP-4-HSP.
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Affiliation(s)
- Yiduo Li
- State Key Laboratory of Medical Neurobiology, Ministry of Education Frontiers Center for Brain Science, and Institutes of Brain Science, Fudan University, Shanghai, China
| | - Cuizhen Zhang
- State Key Laboratory of Medical Neurobiology, Ministry of Education Frontiers Center for Brain Science, and Institutes of Brain Science, Fudan University, Shanghai, China
| | - Gang Peng
- State Key Laboratory of Medical Neurobiology, Ministry of Education Frontiers Center for Brain Science, and Institutes of Brain Science, Fudan University, Shanghai, China
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11
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Saffari A, Brechmann B, Boeger C, Saber WA, Jumo H, Whye D, Wood D, Wahlster L, Alecu J, Ziegler M, Scheffold M, Winden K, Hubbs J, Buttermore E, Barrett L, Borner G, Davies A, Sahin M, Ebrahimi-Fakhari D. High-Content Small Molecule Screen Identifies a Novel Compound That Restores AP-4-Dependent Protein Trafficking in Neuronal Models of AP-4-Associated Hereditary Spastic Paraplegia. RESEARCH SQUARE 2023:rs.3.rs-3036166. [PMID: 37398196 PMCID: PMC10312991 DOI: 10.21203/rs.3.rs-3036166/v1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/04/2023]
Abstract
Unbiased phenotypic screens in patient-relevant disease models offer the potential to detect novel therapeutic targets for rare diseases. In this study, we developed a high-throughput screening assay to identify molecules that correct aberrant protein trafficking in adaptor protein complex 4 (AP-4) deficiency, a rare but prototypical form of childhood-onset hereditary spastic paraplegia, characterized by mislocalization of the autophagy protein ATG9A. Using high-content microscopy and an automated image analysis pipeline, we screened a diversity library of 28,864 small molecules and identified a lead compound, C-01, that restored ATG9A pathology in multiple disease models, including patient-derived fibroblasts and induced pluripotent stem cell-derived neurons. We used multiparametric orthogonal strategies and integrated transcriptomic and proteomic approaches to delineate putative molecular targets of C-01 and potential mechanisms of action. Our results define molecular regulators of intracellular ATG9A trafficking and characterize a lead compound for the treatment of AP-4 deficiency, providing important proof-of-concept data for future Investigational New Drug (IND)-enabling studies.
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Affiliation(s)
| | | | | | | | | | - Dosh Whye
- Boston Children's Hospital, Harvard Medical School
| | - Delaney Wood
- Boston Children's Hospital, Harvard Medical School
| | | | - Julian Alecu
- Boston Children's Hospital, Harvard Medical School
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Synaptic vesicle proteins and ATG9A self-organize in distinct vesicle phases within synapsin condensates. Nat Commun 2023; 14:455. [PMID: 36709207 PMCID: PMC9884207 DOI: 10.1038/s41467-023-36081-3] [Citation(s) in RCA: 9] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2022] [Accepted: 01/16/2023] [Indexed: 01/30/2023] Open
Abstract
Ectopic expression in fibroblasts of synapsin 1 and synaptophysin is sufficient to generate condensates of vesicles highly reminiscent of synaptic vesicle (SV) clusters and with liquid-like properties. Here we show that unlike synaptophysin, other major integral SV membrane proteins fail to form condensates with synapsin, but co-assemble into the clusters formed by synaptophysin and synapsin in this ectopic expression system. Another vesicle membrane protein, ATG9A, undergoes activity-dependent exo-endocytosis at synapses, raising questions about the relation of ATG9A traffic to the traffic of SVs. We find that both in fibroblasts and in nerve terminals ATG9A does not co-assemble into synaptophysin-positive vesicle condensates but localizes on a distinct class of vesicles that also assembles with synapsin but into a distinct phase. Our findings suggest that ATG9A undergoes differential sorting relative to SV proteins and also point to a dual role of synapsin in controlling clustering at synapses of SVs and ATG9A vesicles.
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