title: Inhibition of retrograde transport modulates misfolded protein accumulation and clearance in motoneuron diseases.
abstract: Motoneuron diseases, like spinal bulbar muscular atrophy (SBMA) and amyotrophic lateral sclerosis (ALS), are associated with proteins that because of gene mutation or peculiar structures, acquire aberrant (misfolded) conformations toxic to cells. To prevent misfolded protein toxicity, cells activate a protein quality control (PQC) system composed of chaperones and degradative pathways (proteasome and autophagy). Inefficient activation of the PQC system results in misfolded protein accumulation that ultimately leads to neuronal cell death, while efficient macroautophagy/autophagy-mediated degradation of aggregating proteins is beneficial. The latter relies on an active retrograde transport, mediated by dynein and specific chaperones, such as the HSPB8-BAG3-HSPA8 complex. Here, using cellular models expressing aggregate-prone proteins involved in SBMA and ALS, we demonstrate that inhibition of dynein-mediated retrograde transport, which impairs the targeting to autophagy of misfolded species, does not increase their aggregation. Rather, dynein inhibition correlates with a reduced accumulation and an increased clearance of mutant ARpolyQ, SOD1, truncated TARDBP/TDP-43 and expanded polyGP C9ORF72 products. The enhanced misfolded protein clearance is mediated by the proteasome, rather than by autophagy and correlates with the upregulation of the HSPA8 cochaperone BAG1. In line, overexpression of BAG1 increases the proteasome-mediated clearance of these misfolded proteins. Our data suggest that when the misfolded proteins cannot be efficiently transported toward the perinuclear region of the cells, where they are either degraded by autophagy or stored into the aggresome, the cells activate a compensatory mechanism that relies on the induction of BAG1 to target the HSPA8-bound cargo to the proteasome in a dynein-independent manner.
authors.affiliation: a Sezione di Biomedicina ed Endocrinologia, Dipartimento di Scienze Farmacologiche e Biomolecolari (DiSFeB), Centro di Eccellenza sulle Malattie Neurodegenerative , Università degli Studi di Milano , Milano , Italy.
authors.forename: Riccardo
authors.identifier: http://orcid.org/0000-0003-2719-846X
authors.initials: R
authors.lastname: Cristofani
authors.affiliation: a Sezione di Biomedicina ed Endocrinologia, Dipartimento di Scienze Farmacologiche e Biomolecolari (DiSFeB), Centro di Eccellenza sulle Malattie Neurodegenerative , Università degli Studi di Milano , Milano , Italy.|b Center for Research in Neurodegenerative Diseases (CRND) , IRCCS "C. Mondino" Istituto Nazionale Neurologico , Pavia , Italy.
authors.forename: Valeria
authors.identifier: http://orcid.org/0000-0002-3058-5711
authors.initials: V
authors.lastname: Crippa
authors.affiliation: a Sezione di Biomedicina ed Endocrinologia, Dipartimento di Scienze Farmacologiche e Biomolecolari (DiSFeB), Centro di Eccellenza sulle Malattie Neurodegenerative , Università degli Studi di Milano , Milano , Italy.
authors.forename: Paola
authors.identifier: http://orcid.org/0000-0001-9989-0733
authors.initials: P
authors.lastname: Rusmini
authors.affiliation: a Sezione di Biomedicina ed Endocrinologia, Dipartimento di Scienze Farmacologiche e Biomolecolari (DiSFeB), Centro di Eccellenza sulle Malattie Neurodegenerative , Università degli Studi di Milano , Milano , Italy.
authors.forename: Maria Elena
authors.identifier: http://orcid.org/0000-0001-9490-303X
authors.initials: ME
authors.lastname: Cicardi
authors.affiliation: a Sezione di Biomedicina ed Endocrinologia, Dipartimento di Scienze Farmacologiche e Biomolecolari (DiSFeB), Centro di Eccellenza sulle Malattie Neurodegenerative , Università degli Studi di Milano , Milano , Italy.
authors.forename: Marco
authors.identifier: http://orcid.org/0000-0001-6682-4799
authors.initials: M
authors.lastname: Meroni
authors.affiliation: a Sezione di Biomedicina ed Endocrinologia, Dipartimento di Scienze Farmacologiche e Biomolecolari (DiSFeB), Centro di Eccellenza sulle Malattie Neurodegenerative , Università degli Studi di Milano , Milano , Italy.
authors.forename: Nausicaa V
authors.identifier: http://orcid.org/0000-0003-0750-0692
authors.initials: NV
authors.lastname: Licata
authors.affiliation: c School of Medicine and Surgery, NeuroMI Milan Center for Neuroscience , University of Milano-Bicocca , Italy.
authors.forename: Gessica
authors.identifier: http://orcid.org/0000-0003-3573-7523
authors.initials: G
authors.lastname: Sala
authors.affiliation: a Sezione di Biomedicina ed Endocrinologia, Dipartimento di Scienze Farmacologiche e Biomolecolari (DiSFeB), Centro di Eccellenza sulle Malattie Neurodegenerative , Università degli Studi di Milano , Milano , Italy.
authors.forename: Elisa
authors.identifier: http://orcid.org/0000-0001-7960-0663
authors.initials: E
authors.lastname: Giorgetti
authors.affiliation: d Neurogenetics Branch , National Institute of Neurological Disorders and Stroke, NIH , Bethesda , MD , USA.
authors.forename: Christopher
authors.identifier: http://orcid.org/0000-0003-4994-2472
authors.initials: C
authors.lastname: Grunseich
authors.affiliation: a Sezione di Biomedicina ed Endocrinologia, Dipartimento di Scienze Farmacologiche e Biomolecolari (DiSFeB), Centro di Eccellenza sulle Malattie Neurodegenerative , Università degli Studi di Milano , Milano , Italy.
authors.forename: Mariarita
authors.identifier: http://orcid.org/0000-0003-3250-5591
authors.initials: M
authors.lastname: Galbiati
authors.affiliation: a Sezione di Biomedicina ed Endocrinologia, Dipartimento di Scienze Farmacologiche e Biomolecolari (DiSFeB), Centro di Eccellenza sulle Malattie Neurodegenerative , Università degli Studi di Milano , Milano , Italy.
authors.forename: Margherita
authors.identifier: http://orcid.org/0000-0002-5130-1116
authors.initials: M
authors.lastname: Piccolella
authors.affiliation: a Sezione di Biomedicina ed Endocrinologia, Dipartimento di Scienze Farmacologiche e Biomolecolari (DiSFeB), Centro di Eccellenza sulle Malattie Neurodegenerative , Università degli Studi di Milano , Milano , Italy.
authors.forename: Elio
authors.identifier: http://orcid.org/0000-0002-9515-1463
authors.initials: E
authors.lastname: Messi
authors.affiliation: c School of Medicine and Surgery, NeuroMI Milan Center for Neuroscience , University of Milano-Bicocca , Italy.
authors.forename: Carlo
authors.identifier: http://orcid.org/0000-0002-7499-6600
authors.initials: C
authors.lastname: Ferrarese
authors.affiliation: e Dipartimento di Scienze Biomediche, Metaboliche e Neuroscienze , Università degli Studi di Modena e Reggio Emilia, Centro di Neuroscienze e Neurotecnologie , Modena , Italy.
authors.forename: Serena
authors.identifier: http://orcid.org/0000-0003-0939-0140
authors.initials: S
authors.lastname: Carra
authors.affiliation: a Sezione di Biomedicina ed Endocrinologia, Dipartimento di Scienze Farmacologiche e Biomolecolari (DiSFeB), Centro di Eccellenza sulle Malattie Neurodegenerative , Università degli Studi di Milano , Milano , Italy.|f Centro InterUniversitario sulle Malattie Neurodegenerative , Università degli Studi di Firenze , Roma Tor Vergata and Milano. Genova , Italy.
authors.forename: Angelo
authors.identifier: http://orcid.org/0000-0002-8883-0468
authors.initials: A
authors.lastname: Poletti
mesh_terms: D000818:Animals; D001343:Autophagy; D001692:Biological Transport; D002454:Cell Differentiation; D004268:DNA-Binding Proteins / Q000378:metabolism; D004398:Dyneins / Q000378:metabolism; D020868:Gene Silencing; D050886:HSP20 Heat-Shock Proteins / Q000378:metabolism; D006801:Humans; D057026:Induced Pluripotent Stem Cells / Q000378:metabolism; D051379:Mice; D016472:Motor Neuron Disease / Q000378:metabolism* / Q000473:pathology*; D009046:Motor Neurons / Q000378:metabolism* / Q000473:pathology*; D016716:PC12 Cells; D010455:Peptides / Q000378:metabolism; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D017510:Protein Folding; D059748:Proteolysis; D034741:RNA, Small Interfering / Q000378:metabolism; D051381:Rats; D013482:Superoxide Dismutase / Q000378:metabolism; D014157:Transcription Factors; D025801:Ubiquitin / Q000378:metabolism; D015854:Up-Regulation
chemical_list: C091732:BCL2-associated athanogene 1 protein; D004268:DNA-Binding Proteins; D050886:HSP20 Heat-Shock Proteins; D010455:Peptides; D034741:RNA, Small Interfering; D014157:Transcription Factors; D025801:Ubiquitin; C097188:polyglutamine; D013482:Superoxide Dismutase; D046988:Proteasome Endopeptidase Complex; D004398:Dyneins
keywords: BAG1; BAG3; HSPB8; aggregation; amyotrophic lateral sclerosis; autophagy; misfolded protein; proteasome; protein quality control