title: Inducible HSP70 is critical in preventing the aggregation and enhancing the processing of PMP22.
abstract: Chaperones, also called heat shock proteins (HSPs), transiently interact with proteins to aid their folding, trafficking, and degradation, thereby directly influencing the transport of newly synthesized molecules. Induction of chaperones provides a potential therapeutic approach for protein misfolding disorders, such as peripheral myelin protein 22 (PMP22)-associated peripheral neuropathies. Cytosolic aggregates of PMP22, linked with a demyelinating Schwann cell phenotype, result in suppression of proteasome activity and activation of proteostatic mechanisms, including the heat shock pathway. Although the beneficial effects of chaperones in preventing the aggregation and improving the trafficking of PMP22 have been repeatedly observed, the requirement for HSP70 in events remains elusive. In this study, we show that activation of the chaperone pathway in fibroblasts from PMP22 duplication-associated Charcot-Marie-Tooth disease type 1A patient with an FDA-approved small molecule increases HSP70 expression and attenuates proteasome dysfunction. Using cells from an HSP70.1/3(-/-) (inducible HSP70) mouse model, we demonstrate that under proteotoxic stress, this chaperone is critical in preventing the aggregation of PMP22, and this effect is aided by macroautophagy. When examined at steady-state, HSP70 appears to play a minor role in the trafficking of wild-type-PMP22, while it is crucial for preventing the buildup of the aggregation-prone Trembler-J-PMP22. HSP70 aids the processing of Trembler-J-PMP22 through the Golgi and its delivery to lysosomes via Rab7-positive vesicles. Together, these results demonstrate a key role for inducible HSP70 in aiding the processing and hindering the accumulation of misfolded PMP22, which in turn alleviates proteotoxicity within the cells.
authors.affiliation: Departments of Neuroscience and Neurology, College of Medicine, McKnight Brain Institute, University of Florida, Gainesville, FL, USA.
authors.forename: Vinita G
authors.initials: VG
authors.lastname: Chittoor-Vinod
authors.affiliation: Departments of Neuroscience and Neurology, College of Medicine, McKnight Brain Institute, University of Florida, Gainesville, FL, USA.
authors.forename: Sooyeon
authors.initials: S
authors.lastname: Lee
authors.affiliation: Department of Physical Therapy, College of Public Health & Health Professions, University of Florida, Gainesville, FL, USA.
authors.forename: Sarah M
authors.initials: SM
authors.lastname: Judge
authors.affiliation: Departments of Neuroscience and Neurology, College of Medicine, McKnight Brain Institute, University of Florida, Gainesville, FL, USA notterpek@ufl.edu.
authors.forename: Lucia
authors.initials: L
authors.lastname: Notterpek
mesh_terms: D000111:Acetylcysteine / Q000031:analogs & derivatives / Q000494:pharmacology; D000225:Adenine / Q000031:analogs & derivatives / Q000494:pharmacology; D000818:Animals; D001343:Autophagy / Q000187:drug effects / Q000235:genetics; D002478:Cells, Cultured; D002607:Charcot-Marie-Tooth Disease / Q000473:pathology; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D004622:Embryo, Mammalian; D005347:Fibroblasts / Q000187:drug effects; D005786:Gene Expression Regulation / Q000187:drug effects / Q000235:genetics / Q000502:physiology*; D018840:HSP70 Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D051379:Mice; D008822:Mice, Transgenic; D008875:Middle Aged; D009185:Myelin Proteins / Q000378:metabolism*; D046988:Proteasome Endopeptidase Complex / Q000235:genetics / Q000378:metabolism; D066263:Protein Aggregation, Pathological / Q000378:metabolism* / Q000517:prevention & control; D021381:Protein Transport / Q000187:drug effects / Q000235:genetics; D011725:Pyridines / Q000494:pharmacology; D015398:Signal Transduction / Q000187:drug effects / Q000235:genetics; D012867:Skin / Q000473:pathology; D025801:Ubiquitin / Q000235:genetics / Q000378:metabolism
chemical_list: C521963:6-chloro-9-(4-methoxy-3,5-dimethylpyridin-2-ylmethyl)-9H-purin-2-ylamine; D015853:Cysteine Proteinase Inhibitors; D018840:HSP70 Heat-Shock Proteins; D009185:Myelin Proteins; C073687:PMP22 protein, human; D011725:Pyridines; D025801:Ubiquitin; C067713:lactacystin; D046988:Proteasome Endopeptidase Complex; D000225:Adenine; D000111:Acetylcysteine
keywords: Charcot–Marie–Tooth disease; Trembler-J; chaperones; neuropathy; proteasome