Many ALS associated proteins, as SOD1, TDP-43, DPRs from C9orf72, etc. tend to misfold and accumulate into aggregates in neurons. Protein quality control system maintains cellular protein homeostasis preventing protein aggregation and counteracting their toxicity by enhancing degradation via proteasome and/or autophagy. The chaperone assisted selective autophagy (CASA) with its complex formed by HSP70, HSPB8, BAG3 and CHIP is mainly involved in the misfolded protein degradation. Moreover, an efficient dynein mediated transport of misfolded proteins to the site of degradation is required as key point to control their aggregation and degradation. In fact, we found an alteration of SQSTM1/p62 and LC3 expression accompanied by altered localization and a reduction of autophagosome number per cell when the dynein retrograde transport of HSPB8/BAG3 substrates are blocked. Despite this, blockage of dynein function reduced the PBS insoluble fraction of mutated misfolded proteins (SOD1, TDP-43 and DPRs). Dynein inhibition selectively increased the mRNA level of the nucleotide exchange factor BAG1, both in NSC34 and in motoneuron derived from iPS cells. Notably, exogenous BAG1 overexpression reduced misfolded species aggregation increasing UPS dependent degradation of proteins recognized by HSP70. Notably, a dysregulation of HSP70 levels has been recently identified in peripheral cells from ALS patients and its downregulation increases TDP-43 protein levels. 13 Moreover, dynein inhibition increased mRNA and protein levels of the chaperone mediated autophagy (CMA) receptor Lamp2A, suggesting that CMA may restore misfolded proteins degradation. As we observed in dynein depleted cells, BAG1 mRNA is increased also in Lamp2A depleted cells. We measured the protein levels of alpha-synuclein as CMA substrate. We found that BAG1 overexpression reduced alpha-synuclein level, while BAG1 depletion has an opposite effect. In parallel, Lamp2A depleted cells retained a very efficient proteasome system that rapidly cleared soluble alpha- synuclein, even if we observed alpha-synuclein PBS insoluble species accumulation. Collectively, these data suggest that BAG1 is an important player to assist the degradation via proteasome and CMA of ALS related misfolded protein.

The BAG1 molecular chaperone regulators prevent ALS related neurotoxic misfolded proteins accumulation via proteasome and chaperone mediated autophagy / R.M. Cristofani, P. Rusmini, B. Tedesco, V. Ferrari, E. Casarotto, M. Chierichetti, M. Cozzi, M. Galbiati, V. Crippa, A. Poletti. ((Intervento presentato al 31. convegno International symposium on ALS/MND-Amyotrophic Lateral Sclerosis/Motor Neurone Disease tenutosi a online nel 2020.

The BAG1 molecular chaperone regulators prevent ALS related neurotoxic misfolded proteins accumulation via proteasome and chaperone mediated autophagy

R.M. Cristofani
Primo
;
P. Rusmini;B. Tedesco;V. Ferrari;E. Casarotto;M. Chierichetti;M. Cozzi;M. Galbiati;V. Crippa;A. Poletti
Ultimo
2020

Abstract

Many ALS associated proteins, as SOD1, TDP-43, DPRs from C9orf72, etc. tend to misfold and accumulate into aggregates in neurons. Protein quality control system maintains cellular protein homeostasis preventing protein aggregation and counteracting their toxicity by enhancing degradation via proteasome and/or autophagy. The chaperone assisted selective autophagy (CASA) with its complex formed by HSP70, HSPB8, BAG3 and CHIP is mainly involved in the misfolded protein degradation. Moreover, an efficient dynein mediated transport of misfolded proteins to the site of degradation is required as key point to control their aggregation and degradation. In fact, we found an alteration of SQSTM1/p62 and LC3 expression accompanied by altered localization and a reduction of autophagosome number per cell when the dynein retrograde transport of HSPB8/BAG3 substrates are blocked. Despite this, blockage of dynein function reduced the PBS insoluble fraction of mutated misfolded proteins (SOD1, TDP-43 and DPRs). Dynein inhibition selectively increased the mRNA level of the nucleotide exchange factor BAG1, both in NSC34 and in motoneuron derived from iPS cells. Notably, exogenous BAG1 overexpression reduced misfolded species aggregation increasing UPS dependent degradation of proteins recognized by HSP70. Notably, a dysregulation of HSP70 levels has been recently identified in peripheral cells from ALS patients and its downregulation increases TDP-43 protein levels. 13 Moreover, dynein inhibition increased mRNA and protein levels of the chaperone mediated autophagy (CMA) receptor Lamp2A, suggesting that CMA may restore misfolded proteins degradation. As we observed in dynein depleted cells, BAG1 mRNA is increased also in Lamp2A depleted cells. We measured the protein levels of alpha-synuclein as CMA substrate. We found that BAG1 overexpression reduced alpha-synuclein level, while BAG1 depletion has an opposite effect. In parallel, Lamp2A depleted cells retained a very efficient proteasome system that rapidly cleared soluble alpha- synuclein, even if we observed alpha-synuclein PBS insoluble species accumulation. Collectively, these data suggest that BAG1 is an important player to assist the degradation via proteasome and CMA of ALS related misfolded protein.
9-dic-2020
Settore BIO/09 - Fisiologia
Settore BIO/13 - Biologia Applicata
Motor Neurone Disease Association
International Alliance of ALS/MND-Amyotrophic Lateral Sclerosis/Motor Neurone Disease Associations
The BAG1 molecular chaperone regulators prevent ALS related neurotoxic misfolded proteins accumulation via proteasome and chaperone mediated autophagy / R.M. Cristofani, P. Rusmini, B. Tedesco, V. Ferrari, E. Casarotto, M. Chierichetti, M. Cozzi, M. Galbiati, V. Crippa, A. Poletti. ((Intervento presentato al 31. convegno International symposium on ALS/MND-Amyotrophic Lateral Sclerosis/Motor Neurone Disease tenutosi a online nel 2020.
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/2434/798333
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