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Open AccessArticle

The Ubiquitin Proteasome System Is a Key Regulator of Pluripotent Stem Cell Survival and Motor Neuron Differentiation

1
Illawarra Health and Medical Research Institute, Northfields Avenue, Wollongong, NSW 2522, Australia
2
School of Chemistry and Molecular Bioscience, University of Wollongong, Northfields Avenue, Wollongong, NSW 2522, Australia
3
School of Medical Sciences, University of New South Wales, Sydney, NSW 2052, Australia
4
School of Medical Sciences, Faculty of Medicine and Health, The University of Sydney, Camperdown, NSW 2050, Australia
*
Authors to whom correspondence should be addressed.
These authors contributed equally to this work.
Cells 2019, 8(6), 581; https://doi.org/10.3390/cells8060581
Received: 13 May 2019 / Revised: 31 May 2019 / Accepted: 4 June 2019 / Published: 13 June 2019
(This article belongs to the Special Issue iPS Cells for Disease Modeling)
The ubiquitin proteasome system (UPS) plays an important role in regulating numerous cellular processes, and a dysfunctional UPS is thought to contribute to motor neuron disease. Consequently, we sought to map the changing ubiquitome in human iPSCs during their pluripotent stage and following differentiation to motor neurons. Ubiquitinomics analysis identified that spliceosomal and ribosomal proteins were more ubiquitylated in pluripotent stem cells, whilst proteins involved in fatty acid metabolism and the cytoskeleton were specifically ubiquitylated in the motor neurons. The UPS regulator, ubiquitin-like modifier activating enzyme 1 (UBA1), was increased 36-fold in the ubiquitome of motor neurons compared to pluripotent stem cells. Thus, we further investigated the functional consequences of inhibiting the UPS and UBA1 on motor neurons. The proteasome inhibitor MG132, or the UBA1-specific inhibitor PYR41, significantly decreased the viability of motor neurons. Consistent with a role of the UPS in maintaining the cytoskeleton and regulating motor neuron differentiation, UBA1 inhibition also reduced neurite length. Pluripotent stem cells were extremely sensitive to MG132, showing toxicity at nanomolar concentrations. The motor neurons were more resilient to MG132 than pluripotent stem cells but demonstrated higher sensitivity than fibroblasts. Together, this data highlights the important regulatory role of the UPS in pluripotent stem cell survival and motor neuron differentiation. View Full-Text
Keywords: ubiquitin; ubiquitinomics; UBA1; induced pluripotent stem cell; motor neuron; motor neurone disease; amyotrophic lateral sclerosis ubiquitin; ubiquitinomics; UBA1; induced pluripotent stem cell; motor neuron; motor neurone disease; amyotrophic lateral sclerosis
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Bax, M.; McKenna, J.; Do-Ha, D.; Stevens, C.H.; Higginbottom, S.; Balez, R.; Cabral-da-Silva, M.C.; Farrawell, N.E.; Engel, M.; Poronnik, P.; Yerbury, J.J.; Saunders, D.N.; Ooi, L. The Ubiquitin Proteasome System Is a Key Regulator of Pluripotent Stem Cell Survival and Motor Neuron Differentiation. Cells 2019, 8, 581.

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    Doi: 10.5281/zenodo.3235944
    Link: https://zenodo.org/deposit/3235944
    Description: Supplementary Tables and Figure Supplementary Table 1: Ubiquitome data from iPSC and motor neurons. Supplementary Table 2: Functional analysis of ubiquitome proteins via enrichment in KEGG pathways. Supplementary Figure 1: Functional enrichment supporting data Abundance of individual proteins within enriched functional groups (KEGG pathways) identified in the ubiquitomes of iPSC and motor neurons. (A) Synaptic proteins (B) Metabolism (C) Cell/matrix interaction (D) Spliceosome.
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