1
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Ravichandran A, Das R. The Thermodynamic Properties of Fat10ylated Proteins Are Regulated by the Fat10ylation Site. ACS OMEGA 2024; 9:22265-22276. [PMID: 38799324 PMCID: PMC11112694 DOI: 10.1021/acsomega.4c01396] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/13/2024] [Revised: 04/24/2024] [Accepted: 04/29/2024] [Indexed: 05/29/2024]
Abstract
Degradation of proteins by the proteasome is crucial in regulating their levels in the cell. Post-translational modifications, such as ubiquitylation and Fat10ylation, trigger proteasomal degradation of the substrate proteins. While ubiquitylation regulates multiple cellular pathways, Fat10ylation functions explicitly in the inflammatory response pathway. At the proteasome, ubiquitin is recycled after being cleaved from the substrate, while Fat10 is degraded simultaneously with its substrate. Although the thermodynamic properties of the substrate are critical for effective proteasomal degradation, they remain poorly understood for the Fat10-proteasome pathway. We studied the thermodynamic properties of the Fat10∼substrate conjugate to uncover mechanistic details of the pathway. First, the mechanical unfolding of Fat10∼substrate was studied by molecular dynamics simulations, which suggested that the unfolding pathway and unfolding energy of the substrate depend on the site of Fat10 modification. We also investigated different pathways for the entry of the Fat10∼substrate into the proteasome core. Our analysis supports a model where the entry of Fat10, followed by the substrate, is the energetically preferred pathway. Further, we studied Fat10's effect on the thermodynamic properties of distinct substrates, considering their size, flexibility, and surface properties. The results uncovered significant entropic destabilization of substrates due to Fat10ylation, particularly in smaller substrates. For larger substrates, multi-monoFat10ylation is necessary to induce destabilization. Our study further reveals that Fat10 modification at negative patches on substrate surfaces is essential for optimal destabilization and subsequent degradation. These findings provide atomistic insights into the degradation mechanisms in the Fat10 proteasome pathway with potential implications for therapeutic interventions.
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Affiliation(s)
- Aravind Ravichandran
- National
Center for Biological Sciences, Tata Institute
of Fundamental Research, Bangalore 560065, India
- SASTRA
University, Thirumalaisamudram, Thanjavur 613401, India
| | - Ranabir Das
- National
Center for Biological Sciences, Tata Institute
of Fundamental Research, Bangalore 560065, India
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2
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Dear AJ, Garcia GA, Meisl G, Collins GA, Knowles TPJ, Goldberg AL. Maximum entropy determination of mammalian proteome dynamics. Proc Natl Acad Sci U S A 2024; 121:e2313107121. [PMID: 38652742 PMCID: PMC11067036 DOI: 10.1073/pnas.2313107121] [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: 08/02/2023] [Accepted: 03/04/2024] [Indexed: 04/25/2024] Open
Abstract
Full understanding of proteostasis and energy utilization in cells will require knowledge of the fraction of cell proteins being degraded with different half-lives and their rates of synthesis. We therefore developed a method to determine such information that combines mathematical analysis of protein degradation kinetics obtained in pulse-chase experiments with Bayesian data fitting using the maximum entropy principle. This approach will enable rapid analyses of whole-cell protein dynamics in different cell types, physiological states, and neurodegenerative disease. Using it, we obtained surprising insights about protein stabilities in cultured cells normally and upon activation of proteolysis by mTOR inhibition and increasing cAMP or cGMP. It revealed that >90% of protein content in dividing mammalian cell lines is long-lived, with half-lives of 24 to 200 h, and therefore comprises much of the proteins in daughter cells. The well-studied short-lived proteins (half-lives < 10 h) together comprise <2% of cell protein mass, but surprisingly account for 10 to 20% of measurable newly synthesized protein mass. Evolution thus appears to have minimized intracellular proteolysis except to rapidly eliminate misfolded and regulatory proteins.
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Affiliation(s)
- Alexander J. Dear
- Department of Cell Biology, Blavatnik Institute, Harvard Medical School, Boston, MA02115
- Department of Chemistry, University of Cambridge, CambridgeCB2 1EW, United Kingdom
| | - Gonzalo A. Garcia
- Department of Chemistry, University of Cambridge, CambridgeCB2 1EW, United Kingdom
| | - Georg Meisl
- Department of Chemistry, University of Cambridge, CambridgeCB2 1EW, United Kingdom
| | - Galen A. Collins
- Department of Cell Biology, Blavatnik Institute, Harvard Medical School, Boston, MA02115
- Department of Biochemistry, Molecular Biology, Entomology & Plant Pathology, Mississippi State University, Starkville, MS39762
| | - Tuomas P. J. Knowles
- Department of Chemistry, University of Cambridge, CambridgeCB2 1EW, United Kingdom
- Cavendish Laboratory, Department of Physics, University of Cambridge, CambridgeCB3 0HE, United Kingdom
| | - Alfred L. Goldberg
- Department of Cell Biology, Blavatnik Institute, Harvard Medical School, Boston, MA02115
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3
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Sun C. Single-Molecule-Resolution Approaches in Synaptic Biology. J Phys Chem B 2024; 128:3061-3068. [PMID: 38513216 DOI: 10.1021/acs.jpcb.3c08026] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/23/2024]
Abstract
Synapses between neurons are the primary loci for information transfer and storage in the brain. An individual neuron, alone, can make over 10000 synaptic contacts. It is, however, not easy to investigate what goes on locally within a synapse because many synaptic compartments are only a few hundred nanometers wide in size─close to the diffraction limit of light. To observe the biomolecular machinery and processes within synapses, in situ single-molecule techniques are emerging as powerful tools. Guided by important biological questions, this Perspective will highlight recent advances in using these techniques to obtain in situ measurements of synaptic molecules in three aspects: the cell-biological machinery within synapses, the synaptic architecture, and the synaptic neurotransmitter receptors. These advances showcase the increasing importance of single-molecule-resolution techniques for accessing subcellular biophysical and biomolecular information related to the brain.
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Affiliation(s)
- Chao Sun
- Danish Research Institute of Translational Neuroscience - DANDRITE, Nordic-EMBL Partnership for Molecular Medicine, Department of Molecular Biology and Genetics, Aarhus University, Universitetsbyen 81, 8000 Aarhus C, Denmark
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4
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VerPlank JJ, Gawron JM, Silvestri NJ, Wrabetz L, Feltri ML. Knockout of PA200 improves proteasomal degradation and myelination in a proteotoxic neuropathy. Life Sci Alliance 2024; 7:e202302349. [PMID: 38320810 PMCID: PMC10847332 DOI: 10.26508/lsa.202302349] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2023] [Revised: 01/29/2024] [Accepted: 01/30/2024] [Indexed: 02/12/2024] Open
Abstract
The cellular response to a decrease in protein degradation by 26S proteasomes in chronic diseases is poorly understood. Pharmacological inhibition of proteasomes increases the expression of proteasome subunits and Proteasome Activator 200 (PA200), an alternative proteasome activator. In the S63del mouse model of the peripheral neuropathy Charcot Marie Tooth 1B (CMT1B), proteasomal protein degradation is decreased and proteasome gene expression is increased. Here, we show an increase in PA200 and PA200-bound proteasomes in the peripheral nerves of S63del mice. To test genetically whether the upregulation of PA200 was compensatory, we generated S63del//PA200-/- mice. Unexpectedly, in the sciatic nerves of these mice, there was greater proteasomal protein degradation than in S63del, less polyubiquitinated proteins and markers of the unfolded protein response, and a greater amount of assembled, active 26S proteasomes. These changes were not seen in PA200-/- controls and were therefore specific to the neuropathy. Furthermore, in S63del//PA200-/- mice, myelin thickness and nerve conduction were restored to WT levels. Thus, the upregulation of PA200 is maladaptive in S63del mice and its genetic ablation prevented neuropathy.
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Affiliation(s)
- Jordan Js VerPlank
- https://ror.org/01y64my43 Department of Biochemistry, Institute for Myelin and Glia Exploration, Jacobs School of Medicine and Biomedical Sciences, State University of New York at Buffalo, Buffalo, NY, USA
| | - Joseph M Gawron
- https://ror.org/01y64my43 Department of Biochemistry, Institute for Myelin and Glia Exploration, Jacobs School of Medicine and Biomedical Sciences, State University of New York at Buffalo, Buffalo, NY, USA
| | - Nicholas J Silvestri
- Department of Neurology, Institute for Myelin and Glia Exploration, Jacobs School of Medicine and Biomedical Sciences, State University of New York at Buffalo, Buffalo, NY, USA
| | - Lawrence Wrabetz
- https://ror.org/01y64my43 Department of Biochemistry, Institute for Myelin and Glia Exploration, Jacobs School of Medicine and Biomedical Sciences, State University of New York at Buffalo, Buffalo, NY, USA
- Department of Neurology, Institute for Myelin and Glia Exploration, Jacobs School of Medicine and Biomedical Sciences, State University of New York at Buffalo, Buffalo, NY, USA
| | - Maria Laura Feltri
- https://ror.org/01y64my43 Department of Biochemistry, Institute for Myelin and Glia Exploration, Jacobs School of Medicine and Biomedical Sciences, State University of New York at Buffalo, Buffalo, NY, USA
- Department of Neurology, Institute for Myelin and Glia Exploration, Jacobs School of Medicine and Biomedical Sciences, State University of New York at Buffalo, Buffalo, NY, USA
- IRCCS Neurological Institute "Carlo Besta," Milano, Italy
- Department of Medical Biotechnology and Translational Medicine, Universita' degli Studi di Milano, Milano, Italy
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5
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Wang T, Zhang Y, Liu Y, Huang Y, Wang W. Amino Acid-Starved Cancer Cells Utilize Macropinocytosis and Ubiquitin-Proteasome System for Nutrient Acquisition. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2024; 11:e2304791. [PMID: 37983609 PMCID: PMC10767443 DOI: 10.1002/advs.202304791] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/14/2023] [Revised: 10/06/2023] [Indexed: 11/22/2023]
Abstract
To grow in nutrient-deprived tumor microenvironment, cancer cells often internalize and degrade extracellular proteins to refuel intracellular amino acids. However, the nutrient acquisition routes reported by previous studies are mainly restricted in autophagy-lysosomal pathway. It remains largely unknown if other protein degradation systems also contribute to the utilization of extracellular nutrients. Herein, it is demonstrated that under amino acid starvation, extracellular protein internalization through macropinocytosis and protein degradation through ubiquitin-proteasome system are activated as a nutrient supply route, sensitizing cancer cells to proteasome inhibition. By inhibiting both macropinocytosis and ubiquitin-proteasome system, an innovative approach to intensify amino acid starvation for cancer therapy is presented. To maximize therapeutic efficacy and minimize systemic side effects, a pH-responsive polymersome nanocarrier is developed to deliver therapeutic agents specifically to tumor tissues. This nanoparticle system provides an approach to exacerbate amino acid starvation for cancer therapy, which represents a promising strategy for cancer treatment.
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Affiliation(s)
- Tianyi Wang
- State Key Laboratory of Pharmaceutical BiotechnologyThe University of Hong KongHong KongChina
- Department of Pharmacology and PharmacyLi Ka Shing Faculty of MedicineThe University of Hong KongHong KongChina
- Dr. Li Dak‐Sum Research CentreThe University of Hong KongHong KongChina
| | - Yaming Zhang
- State Key Laboratory of Pharmaceutical BiotechnologyThe University of Hong KongHong KongChina
- Department of Pharmacology and PharmacyLi Ka Shing Faculty of MedicineThe University of Hong KongHong KongChina
- Dr. Li Dak‐Sum Research CentreThe University of Hong KongHong KongChina
| | - Yuwei Liu
- State Key Laboratory of Pharmaceutical BiotechnologyThe University of Hong KongHong KongChina
- Department of Pharmacology and PharmacyLi Ka Shing Faculty of MedicineThe University of Hong KongHong KongChina
- Dr. Li Dak‐Sum Research CentreThe University of Hong KongHong KongChina
| | - Yi Huang
- State Key Laboratory of Pharmaceutical BiotechnologyThe University of Hong KongHong KongChina
- Department of Pharmacology and PharmacyLi Ka Shing Faculty of MedicineThe University of Hong KongHong KongChina
- Dr. Li Dak‐Sum Research CentreThe University of Hong KongHong KongChina
| | - Weiping Wang
- State Key Laboratory of Pharmaceutical BiotechnologyThe University of Hong KongHong KongChina
- Department of Pharmacology and PharmacyLi Ka Shing Faculty of MedicineThe University of Hong KongHong KongChina
- Dr. Li Dak‐Sum Research CentreThe University of Hong KongHong KongChina
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6
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Sun C, Desch K, Nassim-Assir B, Giandomenico SL, Nemcova P, Langer JD, Schuman EM. An abundance of free regulatory (19 S) proteasome particles regulates neuronal synapses. Science 2023; 380:eadf2018. [PMID: 37228199 DOI: 10.1126/science.adf2018] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2022] [Accepted: 04/04/2023] [Indexed: 05/27/2023]
Abstract
The proteasome, the major protein-degradation machine in cells, regulates neuronal synapses and long-term information storage. Here, using super-resolution microscopy, we found that the two essential subcomplexes of the proteasome, the regulatory (19S) and catalytic (20S) particles, are differentially distributed within individual rat cortical neurons. We discovered an unexpected abundance of free 19S particles near synapses. The free neuronal 19S particles bind and deubiquitylate lysine 63-ubiquitin (Lys63-ub), a non-proteasome-targeting ubiquitin linkage. Pull-down assays revealed a significant overrepresentation of synaptic molecules as Lys63-ub interactors. Inhibition of the 19S deubiquitylase activity significantly altered excitatory synaptic transmission and reduced the synaptic availability of AMPA receptors at multiple trafficking points in a proteasome-independent manner. Together, these results reveal a moonlighting function of the regulatory proteasomal subcomplex near synapses.
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Affiliation(s)
- Chao Sun
- Max Planck Institute for Brain Research, 60438 Frankfurt am Main, Germany
| | - Kristina Desch
- Max Planck Institute for Brain Research, 60438 Frankfurt am Main, Germany
| | | | | | - Paulina Nemcova
- Max Planck Institute for Brain Research, 60438 Frankfurt am Main, Germany
| | - Julian D Langer
- Max Planck Institute for Brain Research, 60438 Frankfurt am Main, Germany
- Max Planck Institute for Biophysics, 60438 Frankfurt am Main, Germany
| | - Erin M Schuman
- Max Planck Institute for Brain Research, 60438 Frankfurt am Main, Germany
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7
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Pinos I, Yu J, Pilli N, Kane MA, Amengual J. Functional characterization of interleukin 4 and retinoic acid signaling crosstalk during alternative macrophage activation. Biochim Biophys Acta Mol Cell Biol Lipids 2023; 1868:159291. [PMID: 36754230 PMCID: PMC9974901 DOI: 10.1016/j.bbalip.2023.159291] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2022] [Revised: 01/25/2023] [Accepted: 01/28/2023] [Indexed: 02/09/2023]
Abstract
Retinoic acid possesses potent immunomodulatory properties in various cell types, including macrophages. In this study, we first investigated the effects at the transcriptional and functional levels of exogenous retinoic acid in murine bone marrow-derived macrophages (BMDMs) in the presence or absence of interleukin 4 (IL4), a cytokine with potent anti-inflammatory properties. We examined the effect of IL4 on vitamin A homeostasis in macrophages by quantifying retinoid synthesis and secretion. Our RNAseq data show that exogenous retinoic acid synergizes with IL4 to regulate anti-inflammatory pathways such as oxidative phosphorylation and phagocytosis. Efferocytosis and lysosomal degradation assays validated gene expression changes at the functional level. IL4 treatment altered the expression of several genes involved in vitamin A transport and conversion to retinoic acid. Radiolabeling experiments and mass spectrometry assays revealed that IL4 stimulates retinoic acid production and secretion in a signal transducer and activator of transcription 6 (STAT6)-dependent manner. In summary, our studies highlight the key role of exogenous and endogenous retinoic acid in shaping the anti-inflammatory response of macrophages.
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Affiliation(s)
- Ivan Pinos
- Division of Nutritional Sciences, University of Illinois Urbana Champaign, Urbana, IL, United States
| | - Jianshi Yu
- Department of Pharmaceutical Sciences, University of Maryland School of Pharmacy, Baltimore, MD, United States
| | - Nageswara Pilli
- Department of Pharmaceutical Sciences, University of Maryland School of Pharmacy, Baltimore, MD, United States
| | - Maureen A Kane
- Department of Pharmaceutical Sciences, University of Maryland School of Pharmacy, Baltimore, MD, United States
| | - Jaume Amengual
- Division of Nutritional Sciences, University of Illinois Urbana Champaign, Urbana, IL, United States; Department of Food Science and Human Nutrition, University of Illinois Urbana Champaign, Urbana, IL, United States.
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8
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Ibrahim B, Akere TH, Chakraborty S, Valsami-Jones E, Ali-Boucetta H. Gold Nanoparticles Induced Size Dependent Cytotoxicity on Human Alveolar Adenocarcinoma Cells by Inhibiting the Ubiquitin Proteasome System. Pharmaceutics 2023; 15:pharmaceutics15020432. [PMID: 36839757 PMCID: PMC9961554 DOI: 10.3390/pharmaceutics15020432] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2022] [Revised: 01/20/2023] [Accepted: 01/25/2023] [Indexed: 01/31/2023] Open
Abstract
Gold nanoparticles (AuNPs) are widely used in biomedicine due to their remarkable therapeutic applications. However, little is known about their cytotoxic effects on the ubiquitin proteasome system (UPS). Herein, the cytotoxicity of different sizes of AuNPs (5, 10, and 80 nm) on the UPS was investigated with a particular focus on deubiquitinating enzymes (DUBs) such as ubiquitin-specific proteases (USP) and ubiquitin carboxyl-terminal hydrolases (UCHL-1) in human alveolar epithelial adenocarcinoma (A549). It was found that all sizes of AuNPs reduced the percentage of viable A549 cells and increased lactate dehydrogenase (LDH) release, measured using the MTT and LDH assays, respectively. Furthermore, the 5 nm AuNPs were found to exhibit greater cytotoxicity than the 10 and 80 nm AuNPs. In addition, apoptosis and necrosis were activated through reactive oxygen species (ROS) generation due to AuNPs exposure. The internalisation of AuNPs in A549 cells increased with increasing particle size (80 > 10 > 5 nm). Interestingly, the expression of USP7, USP8, USP10, and UCHL-1 was significantly (p < 0.001) downregulated upon treatment with 5-30 µg/mL of all the AuNPs sizes compared to control cells. Moreover, the inhibition of these proteins triggered mitochondrial-related apoptosis through the upregulation of poly (ADP-ribose) polymerase (PARP), caspase-3, and caspase-9. Collectively, these results indicate that AuNPs suppress the proliferation of A549 cells and can potentially be used as novel inhibitors of the proteasome.
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Affiliation(s)
- Bashiru Ibrahim
- Nanomedicine, Drug Delivery & Nanotoxicology (NDDN) Laboratory, School of Pharmacy, College of Medical and Dental Sciences, University of Birmingham, Birmingham B15 2TT, UK
- School of Geography, Earth and Environmental Sciences, College of Life and Environmental Sciences, University of Birmingham, Birmingham B15 2TT, UK
| | - Taiwo Hassan Akere
- Nanomedicine, Drug Delivery & Nanotoxicology (NDDN) Laboratory, School of Pharmacy, College of Medical and Dental Sciences, University of Birmingham, Birmingham B15 2TT, UK
- School of Geography, Earth and Environmental Sciences, College of Life and Environmental Sciences, University of Birmingham, Birmingham B15 2TT, UK
| | - Swaroop Chakraborty
- School of Geography, Earth and Environmental Sciences, College of Life and Environmental Sciences, University of Birmingham, Birmingham B15 2TT, UK
| | - Eugenia Valsami-Jones
- School of Geography, Earth and Environmental Sciences, College of Life and Environmental Sciences, University of Birmingham, Birmingham B15 2TT, UK
- Correspondence: (E.V.-J.); (H.A.-B.)
| | - Hanene Ali-Boucetta
- Nanomedicine, Drug Delivery & Nanotoxicology (NDDN) Laboratory, School of Pharmacy, College of Medical and Dental Sciences, University of Birmingham, Birmingham B15 2TT, UK
- Correspondence: (E.V.-J.); (H.A.-B.)
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9
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Chaperone-assisted selective autophagy targets filovirus VP40 as a client and restricts egress of virus particles. Proc Natl Acad Sci U S A 2023; 120:e2210690120. [PMID: 36598950 PMCID: PMC9926251 DOI: 10.1073/pnas.2210690120] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
The filovirus VP40 protein directs virion egress, which is regulated either positively or negatively by select VP40-host interactions. We demonstrate that host BAG3 and HSP70 recognize VP40 as a client and inhibit the egress of VP40 virus-like particles (VLPs) by promoting degradation of VP40 via Chaperone-assisted selective autophagy (CASA). Pharmacological inhibition of either the early stage formation of the VP40/BAG3/HSP70 tripartite complex, or late stage formation of autolysosomes, rescued VP40 VLP egress back to WT levels. The mechanistic target of rapamycin complex 1 (mTORC1) is a master regulator of autophagy, and we found that surface expression of EBOV GP on either VLPs or an infectious VSV recombinant virus, activated mTORC1. Notably, pharmacological suppression of mTORC1 signaling by rapamycin activated CASA in a BAG3-dependent manner to restrict the egress of both VLPs and infectious EBOV in Huh7 cells. In sum, our findings highlight the involvement of the mTORC1/CASA axis in regulating filovirus egress.
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10
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Lee SH, Hou JC, Hamidzadeh A, Yousafzai MS, Ajeti V, Chang H, Odde DJ, Murrell M, Levchenko A. A molecular clock controls periodically driven cell migration in confined spaces. Cell Syst 2022; 13:514-529.e10. [PMID: 35679858 DOI: 10.1016/j.cels.2022.05.005] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2020] [Revised: 09/10/2021] [Accepted: 05/13/2022] [Indexed: 01/25/2023]
Abstract
Navigation through a dense, physically confining extracellular matrix is common in invasive cell spread and tissue reorganization but is still poorly understood. Here, we show that this migration is mediated by cyclic changes in the activity of a small GTPase RhoA, which is dependent on the oscillatory changes in the activity and abundance of the RhoA guanine nucleotide exchange factor, GEF-H1, and triggered by a persistent increase in the intracellular Ca2+ levels. We show that the molecular clock driving these cyclic changes is mediated by two coupled negative feedback loops, dependent on the microtubule dynamics, with a frequency that can be experimentally modulated based on a predictive mathematical model. We further demonstrate that an increasing frequency of the clock translates into a faster cell migration within physically confining spaces. This work lays the foundation for a better understanding of the molecular mechanisms dynamically driving cell migration in complex environments.
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Affiliation(s)
- Sung Hoon Lee
- Yale Systems Biology Institute, Yale University, West Haven, CT 06516, USA; Department of Biomedical Engineering, Yale University, New Haven, CT 06520, USA
| | - Jay C Hou
- Department of Biomedical Engineering, University of Minnesota, Minneapolis, MN 55455, USA
| | - Archer Hamidzadeh
- Yale Systems Biology Institute, Yale University, West Haven, CT 06516, USA; Department of Biomedical Engineering, Yale University, New Haven, CT 06520, USA
| | - M Sulaiman Yousafzai
- Yale Systems Biology Institute, Yale University, West Haven, CT 06516, USA; Department of Biomedical Engineering, Yale University, New Haven, CT 06520, USA; Department of Physics, Yale University, New Haven, CT 06520, USA
| | - Visar Ajeti
- Yale Systems Biology Institute, Yale University, West Haven, CT 06516, USA; Department of Biomedical Engineering, Yale University, New Haven, CT 06520, USA; Department of Physics, Yale University, New Haven, CT 06520, USA; Department of Biomedical Engineering, University of Connecticut Health Center, Farmington, CT 06032, USA
| | - Hao Chang
- Yale Systems Biology Institute, Yale University, West Haven, CT 06516, USA; Department of Biomedical Engineering, Yale University, New Haven, CT 06520, USA
| | - David J Odde
- Department of Biomedical Engineering, University of Minnesota, Minneapolis, MN 55455, USA
| | - Michael Murrell
- Yale Systems Biology Institute, Yale University, West Haven, CT 06516, USA; Department of Biomedical Engineering, Yale University, New Haven, CT 06520, USA; Department of Physics, Yale University, New Haven, CT 06520, USA
| | - Andre Levchenko
- Yale Systems Biology Institute, Yale University, West Haven, CT 06516, USA; Department of Biomedical Engineering, Yale University, New Haven, CT 06520, USA.
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11
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Supramolecular assembly of GSK3α as a cellular response to amino acid starvation. Mol Cell 2022; 82:2858-2870.e8. [PMID: 35732190 PMCID: PMC9357031 DOI: 10.1016/j.molcel.2022.05.025] [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: 02/01/2021] [Revised: 04/13/2022] [Accepted: 05/20/2022] [Indexed: 11/22/2022]
Abstract
The tolerance of amino acid starvation is fundamental to robust cellular fitness. Asparagine depletion is lethal to some cancer cells, a vulnerability that can be exploited clinically. We report that resistance to asparagine starvation is uniquely dependent on an N-terminal low-complexity domain of GSK3α, which its paralog GSK3β lacks. In response to depletion of specific amino acids, including asparagine, leucine, and valine, this domain mediates supramolecular assembly of GSK3α with ubiquitin-proteasome system components in spatially sequestered cytoplasmic bodies. This effect is independent of mTORC1 or GCN2. In normal cells, GSK3α promotes survival during essential amino acid starvation. In human leukemia, GSK3α body formation predicts asparaginase resistance, and sensitivity to asparaginase combined with a GSK3α inhibitor. We propose that GSK3α body formation provides a cellular mechanism to maximize the catalytic efficiency of proteasomal protein degradation in response to amino acid starvation, an adaptive response co-opted by cancer cells for asparaginase resistance.
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12
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26S proteasomes become stably activated upon heat shock when ubiquitination and protein degradation increase. Proc Natl Acad Sci U S A 2022; 119:e2122482119. [PMID: 35704754 PMCID: PMC9231471 DOI: 10.1073/pnas.2122482119] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Heat shock (HS) promotes protein unfolding, and cells respond by stimulating HS gene expression, ubiquitination of cell proteins, and proteolysis by the proteasome. Exposing HeLa and other cells to 43 °C for 2 h caused a twofold increase in the 26S proteasomes' peptidase activity assayed at 37 °C. This increase in activity occurred without any change in proteasome amount and did not require new protein synthesis. After affinity-purification from HS cells, 26S proteasomes still hydrolyzed peptides, adenosine 5'-triphosphate, and ubiquitinated substrates more rapidly without any evident change in subunit composition, postsynthetic modification, or association with reported proteasome-activating proteins. After returning HS cells to 37 °C, ubiquitin conjugates and proteolysis fell rapidly, but proteasome activity remained high for at least 16 h. Exposure to arsenite, which also causes proteotoxic stress in the cytosol, but not tunicamycin, which causes endoplasmic reticulum stress, also increased ubiquitin conjugate levels and 26S proteasome activity. Although the molecular basis for the enhanced proteasomal activity remains elusive, we studied possible signaling mechanisms. Proteasome activation upon proteotoxic stress required the accumulation of ubiquitinated proteins since blocking ubiquitination by E1 inhibition during HS or arsenite exposure prevented the stimulation of 26S activity. Furthermore, increasing cellular content of ubiquitin conjugates at 37 °C by inhibiting deubiquitinating enzymes with RA190 or b-AP15 also caused proteasome activation. Thus, cells respond to proteotoxic stresses, apparently in response to the accumulation of ubiquitinated proteins, by activating 26S proteasomes, which should help promote the clearance of damaged cell proteins.
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13
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Kandolf S, Grishkovskaya I, Belačić K, Bolhuis DL, Amann S, Foster B, Imre R, Mechtler K, Schleiffer A, Tagare HD, Zhong ED, Meinhart A, Brown NG, Haselbach D. Cryo-EM structure of the plant 26S proteasome. PLANT COMMUNICATIONS 2022; 3:100310. [PMID: 35576154 PMCID: PMC9251434 DOI: 10.1016/j.xplc.2022.100310] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/07/2022] [Revised: 02/01/2022] [Accepted: 03/04/2022] [Indexed: 05/17/2023]
Abstract
Targeted proteolysis is a hallmark of life. It is especially important in long-lived cells that can be found in higher eukaryotes, like plants. This task is mainly fulfilled by the ubiquitin-proteasome system. Thus, proteolysis by the 26S proteasome is vital to development, immunity, and cell division. Although the yeast and animal proteasomes are well characterized, there is only limited information on the plant proteasome. We determined the first plant 26S proteasome structure from Spinacia oleracea by single-particle electron cryogenic microscopy at an overall resolution of 3.3 Å. We found an almost identical overall architecture of the spinach proteasome compared with the known structures from mammals and yeast. Nevertheless, we noticed a structural difference in the proteolytic active β1 subunit. Furthermore, we uncovered an unseen compression state by characterizing the proteasome's conformational landscape. We suspect that this new conformation of the 20S core protease, in correlation with a partial opening of the unoccupied gate, may contribute to peptide release after proteolysis. Our data provide a structural basis for the plant proteasome, which is crucial for further studies.
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Affiliation(s)
- Susanne Kandolf
- Research Institute of Molecular Pathology (IMP), Vienna BioCenter (VBC), Campus-Vienna-BioCenter 1, 1030 Vienna, Austria
| | - Irina Grishkovskaya
- Research Institute of Molecular Pathology (IMP), Vienna BioCenter (VBC), Campus-Vienna-BioCenter 1, 1030 Vienna, Austria
| | - Katarina Belačić
- Research Institute of Molecular Pathology (IMP), Vienna BioCenter (VBC), Campus-Vienna-BioCenter 1, 1030 Vienna, Austria; Vienna BioCenter PhD Program, Doctoral School of the University at Vienna and Medical University of Vienna, Vienna BioCenter (VBC), Vienna, Austria
| | - Derek L Bolhuis
- Department of Pharmacology and Lineberger Comprehensive Cancer Center, University of North Carolina School of Medicine, Chapel Hill, NC 27599, USA
| | - Sascha Amann
- Research Institute of Molecular Pathology (IMP), Vienna BioCenter (VBC), Campus-Vienna-BioCenter 1, 1030 Vienna, Austria; Vienna BioCenter PhD Program, Doctoral School of the University at Vienna and Medical University of Vienna, Vienna BioCenter (VBC), Vienna, Austria
| | - Brent Foster
- Department of Radiology and Biomedical Imaging, Yale University, New Haven, CT 06510, USA
| | - Richard Imre
- Research Institute of Molecular Pathology (IMP), Vienna BioCenter (VBC), Campus-Vienna-BioCenter 1, 1030 Vienna, Austria
| | - Karl Mechtler
- Research Institute of Molecular Pathology (IMP), Vienna BioCenter (VBC), Campus-Vienna-BioCenter 1, 1030 Vienna, Austria
| | - Alexander Schleiffer
- Research Institute of Molecular Pathology (IMP), Vienna BioCenter (VBC), Campus-Vienna-BioCenter 1, 1030 Vienna, Austria
| | - Hemant D Tagare
- Department of Radiology and Biomedical Imaging, Yale University, New Haven, CT 06510, USA
| | - Ellen D Zhong
- Computer Science and Artificial Intelligence Laboratory, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Anton Meinhart
- Research Institute of Molecular Pathology (IMP), Vienna BioCenter (VBC), Campus-Vienna-BioCenter 1, 1030 Vienna, Austria
| | - Nicholas G Brown
- Department of Pharmacology and Lineberger Comprehensive Cancer Center, University of North Carolina School of Medicine, Chapel Hill, NC 27599, USA
| | - David Haselbach
- Research Institute of Molecular Pathology (IMP), Vienna BioCenter (VBC), Campus-Vienna-BioCenter 1, 1030 Vienna, Austria; Institute of Physical Chemistry, University of Freiburg, Albertstraße 21, Freiburg 79104, Germany; CIBSS Centre for Integrative Biological Signalling Studies, University of Freiburg, Freiburg, Germany.
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14
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Gubat J, Selvaraju K, Sjöstrand L, Kumar Singh D, Turkina MV, Schmierer B, Sabatier P, Zubarev RA, Linder S, D’Arcy P. Comprehensive Target Screening and Cellular Profiling of the Cancer-Active Compound b-AP15 Indicate Abrogation of Protein Homeostasis and Organelle Dysfunction as the Primary Mechanism of Action. Front Oncol 2022; 12:852980. [PMID: 35530310 PMCID: PMC9076133 DOI: 10.3389/fonc.2022.852980] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2022] [Accepted: 03/17/2022] [Indexed: 12/11/2022] Open
Abstract
Dienone compounds have been demonstrated to display tumor-selective anti-cancer activity independently of the mutational status of TP53. Previous studies have shown that cell death elicited by this class of compounds is associated with inhibition of the ubiquitin-proteasome system (UPS). Here we extend previous findings by showing that the dienone compound b-AP15 inhibits proteasomal degradation of long-lived proteins. We show that exposure to b-AP15 results in increased association of the chaperones VCP/p97/Cdc48 and BAG6 with proteasomes. Comparisons between the gene expression profile generated by b-AP15 to those elicited by siRNA showed that knock-down of the proteasome-associated deubiquitinase (DUB) USP14 is the closest related to drug response. USP14 is a validated target for b-AP15 and we show that b-AP15 binds covalently to two cysteines, Cys203 and Cys257, in the ubiquitin-binding pocket of the enzyme. Consistent with this, deletion of USP14 resulted in decreased sensitivity to b-AP15. Targeting of USP14 was, however, found to not fully account for the observed proteasome inhibition. In search for additional targets, we utilized genome-wide CRISPR/Cas9 library screening and Proteome Integral Solubility Alteration (PISA) to identify mechanistically essential genes and b-AP15 interacting proteins respectively. Deletion of genes encoding mitochondrial proteins decreased the sensitivity to b-AP15, suggesting that mitochondrial dysfunction is coupled to cell death induced by b-AP15. Enzymes known to be involved in Phase II detoxification such as aldo-ketoreductases and glutathione-S-transferases were identified as b-AP15-targets using PISA. The finding that different exploratory approaches yielded different results may be explained in terms of a “target” not necessarily connected to the “mechanism of action” thus highlighting the importance of a holistic approach in the identification of drug targets. We conclude that b-AP15, and likely also other dienone compounds of the same class, affect protein degradation and proteasome function at more than one level.
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Affiliation(s)
- Johannes Gubat
- Department of Biomedical and Clinical Sciences, Linköping University, Linköping, Sweden
| | - Karthik Selvaraju
- Department of Biomedical and Clinical Sciences, Linköping University, Linköping, Sweden
| | - Linda Sjöstrand
- Department of Biomedical and Clinical Sciences, Linköping University, Linköping, Sweden
| | - Dhananjay Kumar Singh
- Department of Biomedical and Clinical Sciences, Linköping University, Linköping, Sweden
- Department of Pharmacy, Central University of South Bihar, Gaya, India
| | - Maria V. Turkina
- Department of Biomedical and Clinical Sciences, Linköping University, Linköping, Sweden
| | - Bernhard Schmierer
- Department of Medical Biochemistry and Biophysics, Division of Chemical Biology, Karolinska Institutet, Stockholm, Sweden
| | - Pierre Sabatier
- Department of Medical Biochemistry and Biophysics, Division of Physiological Chemistry I, Karolinska Institutet, Stockholm, Sweden
| | - Roman A. Zubarev
- Department of Medical Biochemistry and Biophysics, Division of Physiological Chemistry I, Karolinska Institutet, Stockholm, Sweden
- Department of Pharmacological and Technological Chemistry, I.M. Sechenov First Moscow State Medical University, Moscow, Russia
| | - Stig Linder
- Department of Biomedical and Clinical Sciences, Linköping University, Linköping, Sweden
- Department of Oncology-Pathology, Karolinska Institutet, Stockholm, Sweden
| | - Pádraig D’Arcy
- Department of Biomedical and Clinical Sciences, Linköping University, Linköping, Sweden
- *Correspondence: Pádraig D’Arcy,
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15
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Mammalian Ddi2 is a shuttling factor containing a retroviral protease domain that influences binding of ubiquitylated proteins and proteasomal degradation. J Biol Chem 2022; 298:101875. [PMID: 35358511 PMCID: PMC9062259 DOI: 10.1016/j.jbc.2022.101875] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2021] [Revised: 03/10/2022] [Accepted: 03/11/2022] [Indexed: 11/24/2022] Open
Abstract
Although several proteasome subunits have been shown to bind ubiquitin (Ub) chains, many ubiquitylated substrates also associate with 26S proteasomes via “shuttling factors.” Unlike the well-studied yeast shuttling factors Rad23 and Dsk2, vertebrate homologs Ddi2 and Ddi1 lack a Ub-associated domain; therefore, it is unclear how they bind Ub. Here, we show that deletion of Ddi2 leads to the accumulation of Ub conjugates with K11/K48 branched chains. We found using affinity copurifications that Ddi2 binds Ub conjugates through its Ub-like domain, which is also required for Ddi2 binding to proteasomes. Furthermore, in cell extracts, adding Ub conjugates increased the amount of Ddi2 associated with proteasomes, and adding Ddi2 increased the binding of Ub conjugates to purified proteasomes. In addition, Ddi2 also contains a retroviral protease domain with undefined cellular roles. We show that blocking the endoprotease activity of Ddi2 either genetically or with the HIV protease inhibitor nelfinavir increased its binding to Ub conjugates but decreased its binding to proteasomes and reduced subsequent protein degradation by proteasomes leading to further accumulation of Ub conjugates. Finally, nelfinavir treatment required Ddi2 to induce the unfolded protein response. Thus, Ddi2 appears to function as a shuttling factor in endoplasmic reticulum–associated protein degradation and delivers K11/K48-ubiquitylated proteins to the proteasome. We conclude that the protease activity of Ddi2 influences this shuttling factor activity, promotes protein turnover, and helps prevent endoplasmic reticulum stress, which may explain nelfinavir’s ability to enhance cell killing by proteasome inhibitors.
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16
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Oxidative distress in aging and age-related diseases: Spatiotemporal dysregulation of protein oxidation and degradation. Biochimie 2021; 195:114-134. [PMID: 34890732 DOI: 10.1016/j.biochi.2021.12.002] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2021] [Revised: 12/03/2021] [Accepted: 12/04/2021] [Indexed: 12/31/2022]
Abstract
The concept of oxidative distress had arisen from the assessment of cellular response to high concentrations of reactive species that result from an imbalance between oxidants and antioxidants and cause biomolecular damage. The intracellular distribution and flux of reactive species dramatically change in time and space contributing to the remodeling of the redox landscape and sensitivity of protein residues to oxidants. Here, we hypothesize that compromised spatiotemporal control of generation, conversions, and removal of reactive species underlies protein damage and dysfunction of protein degradation machineries. This leads to the accumulation of oxidatively damaged proteins resulted in an age-dependent decline in the organismal adaptability to oxidative stress. We highlight recent data obtained with the use of various cell cultures, animal models, and patients on irreversible and non-repairable oxidation of key redox-sensitive residues. Multiple reaction products include peptidyl hydroperoxides, alcohols, carbonyls, and carbamoyl moieties as well as Tyr-Tyr, Trp-Tyr, Trp-Trp, Tyr-Cys, His-Lys, His-Arg, and Tyr-Lys cross-links. These lead to protein fragmentation, misfolding, covalent cross-linking, oligomerization, aggregation, and ultimately, causing impaired protein function and turnover. 20S proteasome and autophagy-lysosome pathways are two major types of machinery for the degradation and elimination of oxidatively damaged proteins. Spatiotemporal dysregulation of these pathways under oxidative distress conditions is implicated in aging and age-related disorders such as neurodegenerative and cardiovascular diseases and diabetes. Future investigations in this field allow the discovery of new drugs to target components of dysregulated cell signaling and protein degradation machinery to combat aging and age-related chronic diseases.
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17
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Hommen F, Bilican S, Vilchez D. Protein clearance strategies for disease intervention. J Neural Transm (Vienna) 2021; 129:141-172. [PMID: 34689261 PMCID: PMC8541819 DOI: 10.1007/s00702-021-02431-y] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2021] [Accepted: 10/10/2021] [Indexed: 02/06/2023]
Abstract
Protein homeostasis, or proteostasis, is essential for cell function and viability. Unwanted, damaged, misfolded and aggregated proteins are degraded by the ubiquitin–proteasome system (UPS) and the autophagy-lysosome pathway. Growing evidence indicates that alterations in these major proteolytic mechanisms lead to a demise in proteostasis, contributing to the onset and development of distinct diseases. Indeed, dysregulation of the UPS or autophagy is linked to several neurodegenerative, infectious and inflammatory disorders as well as cancer. Thus, modulation of protein clearance pathways is a promising approach for therapeutics. In this review, we discuss recent findings and open questions on how targeting proteolytic mechanisms could be applied for disease intervention.
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Affiliation(s)
- Franziska Hommen
- Cologne Excellence Cluster for Cellular Stress Responses in Aging-Associated Diseases (CECAD), University of Cologne, Joseph Stelzmann Strasse 26, 50931, Cologne, Germany
| | - Saygın Bilican
- Cologne Excellence Cluster for Cellular Stress Responses in Aging-Associated Diseases (CECAD), University of Cologne, Joseph Stelzmann Strasse 26, 50931, Cologne, Germany
| | - David Vilchez
- Cologne Excellence Cluster for Cellular Stress Responses in Aging-Associated Diseases (CECAD), University of Cologne, Joseph Stelzmann Strasse 26, 50931, Cologne, Germany. .,Center for Molecular Medicine Cologne (CMMC), University of Cologne, Cologne, Germany. .,Faculty of Medicine, University Hospital Cologne, Cologne, Germany.
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18
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Mechanisms That Activate 26S Proteasomes and Enhance Protein Degradation. Biomolecules 2021; 11:biom11060779. [PMID: 34067263 PMCID: PMC8224753 DOI: 10.3390/biom11060779] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2021] [Revised: 05/11/2021] [Accepted: 05/12/2021] [Indexed: 02/07/2023] Open
Abstract
Although ubiquitination is widely assumed to be the only regulated step in the ubiquitin–proteasome pathway, recent studies have demonstrated several important mechanisms that regulate the activities of the 26S proteasome. Most proteasomes in cells are inactive but, upon binding a ubiquitinated substrate, become activated by a two-step mechanism requiring an association of the ubiquitin chain with Usp14 and then a loosely folded protein domain with the ATPases. The initial activation step is signaled by Usp14’s UBL domain, and many UBL-domain-containing proteins (e.g., Rad23, Parkin) also activate the proteasome. ZFAND5 is a distinct type of activator that binds ubiquitin conjugates and the proteasome and stimulates proteolysis during muscle atrophy. The proteasome’s activities are also regulated through subunit phosphorylation. Agents that raise cAMP and activate PKA stimulate within minutes Rpn6 phosphorylation and enhance the selective degradation of short-lived proteins. Likewise, hormones, fasting, and exercise, which raise cAMP, activate proteasomes and proteolysis in target tissues. Agents that raise cGMP and activate PKG also stimulate 26S activities but modify different subunit(s) and stimulate also the degradation of long-lived cell proteins. Both kinases enhance the selective degradation of aggregation-prone proteins that cause neurodegenerative diseases. These new mechanisms regulating proteolysis thus have clear physiological importance and therapeutic potential.
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19
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Pei J, Schuldt M, Nagyova E, Gu Z, El Bouhaddani S, Yiangou L, Jansen M, Calis JJA, Dorsch LM, Blok CS, van den Dungen NAM, Lansu N, Boukens BJ, Efimov IR, Michels M, Verhaar MC, de Weger R, Vink A, van Steenbeek FG, Baas AF, Davis RP, Uh HW, Kuster DWD, Cheng C, Mokry M, van der Velden J, Asselbergs FW, Harakalova M. Multi-omics integration identifies key upstream regulators of pathomechanisms in hypertrophic cardiomyopathy due to truncating MYBPC3 mutations. Clin Epigenetics 2021; 13:61. [PMID: 33757590 PMCID: PMC7989210 DOI: 10.1186/s13148-021-01043-3] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2020] [Accepted: 02/28/2021] [Indexed: 12/13/2022] Open
Abstract
BACKGROUND Hypertrophic cardiomyopathy (HCM) is the most common genetic disease of the cardiac muscle, frequently caused by mutations in MYBPC3. However, little is known about the upstream pathways and key regulators causing the disease. Therefore, we employed a multi-omics approach to study the pathomechanisms underlying HCM comparing patient hearts harboring MYBPC3 mutations to control hearts. RESULTS Using H3K27ac ChIP-seq and RNA-seq we obtained 9310 differentially acetylated regions and 2033 differentially expressed genes, respectively, between 13 HCM and 10 control hearts. We obtained 441 differentially expressed proteins between 11 HCM and 8 control hearts using proteomics. By integrating multi-omics datasets, we identified a set of DNA regions and genes that differentiate HCM from control hearts and 53 protein-coding genes as the major contributors. This comprehensive analysis consistently points toward altered extracellular matrix formation, muscle contraction, and metabolism. Therefore, we studied enriched transcription factor (TF) binding motifs and identified 9 motif-encoded TFs, including KLF15, ETV4, AR, CLOCK, ETS2, GATA5, MEIS1, RXRA, and ZFX. Selected candidates were examined in stem cell-derived cardiomyocytes with and without mutated MYBPC3. Furthermore, we observed an abundance of acetylation signals and transcripts derived from cardiomyocytes compared to non-myocyte populations. CONCLUSIONS By integrating histone acetylome, transcriptome, and proteome profiles, we identified major effector genes and protein networks that drive the pathological changes in HCM with mutated MYBPC3. Our work identifies 38 highly affected protein-coding genes as potential plasma HCM biomarkers and 9 TFs as potential upstream regulators of these pathomechanisms that may serve as possible therapeutic targets.
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Affiliation(s)
- J Pei
- Division Heart and Lungs, Department of Cardiology, University Medical Center Utrecht, University of Utrecht, 3584 CT, Utrecht, The Netherlands
- Regenerative Medicine Utrecht (RMU), University Medical Center Utrecht, University of Utrecht, 3584 CT, Utrecht, The Netherlands
- Department of Nephrology and Hypertension, DIG-D, UMC Utrecht, University of Utrecht, Utrecht, The Netherlands
| | - M Schuldt
- Department of Physiology, Amsterdam UMC, Vrije Universiteit Amsterdam, Amsterdam, The Netherlands
| | - E Nagyova
- Laboratory of Clinical Chemistry and Hematology, UMC Utrecht, Utrecht, The Netherlands
| | - Z Gu
- Department of Biostatistics and Research Support, UMC Utrecht, University of Utrecht, Utrecht, The Netherlands
| | - S El Bouhaddani
- Department of Biostatistics and Research Support, UMC Utrecht, University of Utrecht, Utrecht, The Netherlands
| | - L Yiangou
- Department of Anatomy and Embryology, LUMC, Leiden, The Netherlands
| | - M Jansen
- Department of Genetics, Division of Laboratories, Pharmacy and Biomedical Genetics, UMC Utrecht, University of Utrecht, Utrecht, The Netherlands
| | - J J A Calis
- Division Heart and Lungs, Department of Cardiology, University Medical Center Utrecht, University of Utrecht, 3584 CT, Utrecht, The Netherlands
- Regenerative Medicine Utrecht (RMU), University Medical Center Utrecht, University of Utrecht, 3584 CT, Utrecht, The Netherlands
| | - L M Dorsch
- Department of Physiology, Amsterdam UMC, Vrije Universiteit Amsterdam, Amsterdam, The Netherlands
| | - C Snijders Blok
- Division Heart and Lungs, Department of Cardiology, University Medical Center Utrecht, University of Utrecht, 3584 CT, Utrecht, The Netherlands
| | - N A M van den Dungen
- Laboratory of Clinical Chemistry and Hematology, UMC Utrecht, Utrecht, The Netherlands
| | - N Lansu
- Laboratory of Clinical Chemistry and Hematology, UMC Utrecht, Utrecht, The Netherlands
| | - B J Boukens
- Department of Medical Biology, AMC, Amsterdam, The Netherlands
| | - I R Efimov
- Department of Biomedical Engineering, GWU, Washington, DC, USA
| | - M Michels
- Department of Cardiology, Thoraxcentre, Erasmus Medical Centre, Rotterdam, The Netherlands
| | - M C Verhaar
- Regenerative Medicine Utrecht (RMU), University Medical Center Utrecht, University of Utrecht, 3584 CT, Utrecht, The Netherlands
- Department of Nephrology and Hypertension, DIG-D, UMC Utrecht, University of Utrecht, Utrecht, The Netherlands
| | - R de Weger
- Department of Pathology, UMC Utrecht, University of Utrecht, Utrecht, The Netherlands
| | - A Vink
- Department of Pathology, UMC Utrecht, University of Utrecht, Utrecht, The Netherlands
| | - F G van Steenbeek
- Division Heart and Lungs, Department of Cardiology, University Medical Center Utrecht, University of Utrecht, 3584 CT, Utrecht, The Netherlands
- Regenerative Medicine Utrecht (RMU), University Medical Center Utrecht, University of Utrecht, 3584 CT, Utrecht, The Netherlands
- Department of Clinical Sciences, Faculty of Veterinary Medicine, University of Utrecht, Utrecht, The Netherlands
| | - A F Baas
- Department of Genetics, Division of Laboratories, Pharmacy and Biomedical Genetics, UMC Utrecht, University of Utrecht, Utrecht, The Netherlands
| | - R P Davis
- Department of Anatomy and Embryology, LUMC, Leiden, The Netherlands
| | - H W Uh
- Department of Biostatistics and Research Support, UMC Utrecht, University of Utrecht, Utrecht, The Netherlands
| | - D W D Kuster
- Department of Physiology, Amsterdam UMC, Vrije Universiteit Amsterdam, Amsterdam, The Netherlands
| | - C Cheng
- Regenerative Medicine Utrecht (RMU), University Medical Center Utrecht, University of Utrecht, 3584 CT, Utrecht, The Netherlands
- Department of Nephrology and Hypertension, DIG-D, UMC Utrecht, University of Utrecht, Utrecht, The Netherlands
- Department of Biomedical Engineering, GWU, Washington, DC, USA
| | - M Mokry
- Division Heart and Lungs, Department of Cardiology, University Medical Center Utrecht, University of Utrecht, 3584 CT, Utrecht, The Netherlands
- Regenerative Medicine Utrecht (RMU), University Medical Center Utrecht, University of Utrecht, 3584 CT, Utrecht, The Netherlands
- Laboratory of Clinical Chemistry and Hematology, UMC Utrecht, Utrecht, The Netherlands
- Division of Paediatrics, UMC Utrecht, University of Utrecht, Utrecht, The Netherlands
| | - J van der Velden
- Department of Physiology, Amsterdam UMC, Vrije Universiteit Amsterdam, Amsterdam, The Netherlands
| | - F W Asselbergs
- Division Heart and Lungs, Department of Cardiology, University Medical Center Utrecht, University of Utrecht, 3584 CT, Utrecht, The Netherlands.
- Health Data Research UK and Institute of Health Informatics, University College London, London, UK.
- Institute of Cardiovascular Science, Faculty of Population Health Sciences, University College London, London, UK.
- Division Heart and Lungs, Department of Cardiology, University Medical Center Utrecht, Room E03.818, P.O. Box 85500, 3508 GA, Utrecht, The Netherlands.
| | - M Harakalova
- Division Heart and Lungs, Department of Cardiology, University Medical Center Utrecht, University of Utrecht, 3584 CT, Utrecht, The Netherlands.
- Regenerative Medicine Utrecht (RMU), University Medical Center Utrecht, University of Utrecht, 3584 CT, Utrecht, The Netherlands.
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20
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Cui L, Song W, Zeng Y, Wu Q, Fan Z, Huang T, Zeng B, Zhang M, Ni Q, Li Y, Wang T, Li D, Mao X, Lian T, Yang D, Yang M, Fan X. Deubiquitinase USP7 regulates Drosophila aging through ubiquitination and autophagy. Aging (Albany NY) 2020; 12:23082-23095. [PMID: 33221768 PMCID: PMC7746378 DOI: 10.18632/aging.104067] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2020] [Accepted: 08/14/2020] [Indexed: 02/04/2023]
Abstract
Ubiquitination-mediated protein degradation is the selective degradation of diverse forms of damaged proteins that are tagged with ubiquitin, while deubiquitinating enzymes reverse ubiquitination-mediated protein degradation by removing the ubiquitin chain from the target protein. The interactions of ubiquitinating and deubiquitinating enzymes are required to maintain protein homeostasis. The ubiquitin-specific protease USP7 is a deubiquitinating enzyme that indirectly plays a role in repairing DNA damage and development. However, the mechanism of its participation in aging has not been fully explored. Regarding this issue, we found that USP7 was necessary to maintain the normal lifespan of Drosophila melanogaster, and knockdown of dusp7 shortened the lifespan and reduced the ability of Drosophila to cope with starvation, oxidative stress and heat stress. Furthermore, we showed that the ability of USP7 to regulate aging depends on the autophagy and ubiquitin signaling pathways. Furthermore, 2,5-dimethyl-celecoxib (DMC), a derivative of celecoxib, can partially restore the shortened lifespan and aberrant phenotypes caused by dusp7 knockdown. Our results suggest that USP7 is an important factor involved in the regulation of aging, and related components in this regulatory pathway may become new targets for anti-aging treatments.
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Affiliation(s)
- Lang Cui
- Institute of Animal Genetics and Breeding, Sichuan Agricultural University, Chengdu, Sichuan, P. R. China
| | - Wenhao Song
- Institute of Animal Genetics and Breeding, Sichuan Agricultural University, Chengdu, Sichuan, P. R. China
| | - Yao Zeng
- Institute of Animal Genetics and Breeding, Sichuan Agricultural University, Chengdu, Sichuan, P. R. China
| | - Qi Wu
- Institute of Animal Genetics and Breeding, Sichuan Agricultural University, Chengdu, Sichuan, P. R. China
| | - Ziqiang Fan
- Institute of Animal Genetics and Breeding, Sichuan Agricultural University, Chengdu, Sichuan, P. R. China
| | - Tiantian Huang
- Institute of Animal Genetics and Breeding, Sichuan Agricultural University, Chengdu, Sichuan, P. R. China
| | - Bo Zeng
- Institute of Animal Genetics and Breeding, Sichuan Agricultural University, Chengdu, Sichuan, P. R. China.,Farm Animal Genetic Resources Exploration and Innovation Key Laboratory of Sichuan Province, Sichuan Agricultural University, Chengdu, Sichuan, China
| | - Mingwang Zhang
- Institute of Animal Genetics and Breeding, Sichuan Agricultural University, Chengdu, Sichuan, P. R. China.,Farm Animal Genetic Resources Exploration and Innovation Key Laboratory of Sichuan Province, Sichuan Agricultural University, Chengdu, Sichuan, China
| | - Qingyong Ni
- Institute of Animal Genetics and Breeding, Sichuan Agricultural University, Chengdu, Sichuan, P. R. China.,Farm Animal Genetic Resources Exploration and Innovation Key Laboratory of Sichuan Province, Sichuan Agricultural University, Chengdu, Sichuan, China
| | - Yan Li
- Institute of Animal Genetics and Breeding, Sichuan Agricultural University, Chengdu, Sichuan, P. R. China.,Farm Animal Genetic Resources Exploration and Innovation Key Laboratory of Sichuan Province, Sichuan Agricultural University, Chengdu, Sichuan, China
| | - Tao Wang
- Institute of Animal Genetics and Breeding, Sichuan Agricultural University, Chengdu, Sichuan, P. R. China.,Farm Animal Genetic Resources Exploration and Innovation Key Laboratory of Sichuan Province, Sichuan Agricultural University, Chengdu, Sichuan, China
| | - Diyan Li
- Institute of Animal Genetics and Breeding, Sichuan Agricultural University, Chengdu, Sichuan, P. R. China.,Farm Animal Genetic Resources Exploration and Innovation Key Laboratory of Sichuan Province, Sichuan Agricultural University, Chengdu, Sichuan, China
| | - Xueping Mao
- Institute of Animal Genetics and Breeding, Sichuan Agricultural University, Chengdu, Sichuan, P. R. China.,Farm Animal Genetic Resources Exploration and Innovation Key Laboratory of Sichuan Province, Sichuan Agricultural University, Chengdu, Sichuan, China
| | - Ting Lian
- Institute of Animal Genetics and Breeding, Sichuan Agricultural University, Chengdu, Sichuan, P. R. China.,Farm Animal Genetic Resources Exploration and Innovation Key Laboratory of Sichuan Province, Sichuan Agricultural University, Chengdu, Sichuan, China
| | - Deying Yang
- Institute of Animal Genetics and Breeding, Sichuan Agricultural University, Chengdu, Sichuan, P. R. China.,Farm Animal Genetic Resources Exploration and Innovation Key Laboratory of Sichuan Province, Sichuan Agricultural University, Chengdu, Sichuan, China
| | - Mingyao Yang
- Institute of Animal Genetics and Breeding, Sichuan Agricultural University, Chengdu, Sichuan, P. R. China.,Farm Animal Genetic Resources Exploration and Innovation Key Laboratory of Sichuan Province, Sichuan Agricultural University, Chengdu, Sichuan, China
| | - Xiaolan Fan
- Institute of Animal Genetics and Breeding, Sichuan Agricultural University, Chengdu, Sichuan, P. R. China.,Farm Animal Genetic Resources Exploration and Innovation Key Laboratory of Sichuan Province, Sichuan Agricultural University, Chengdu, Sichuan, China
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21
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Multiple myeloma cells are exceptionally sensitive to heat shock, which overwhelms their proteostasis network and induces apoptosis. Proc Natl Acad Sci U S A 2020; 117:21588-21597. [PMID: 32817432 DOI: 10.1073/pnas.2001323117] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Proteasome inhibitors, such as bortezomib (BTZ), are highly effective and widely used treatments for multiple myeloma. One proposed reason for myeloma cells' exceptional sensitivity to proteasome inhibition is that they produce and continually degrade unusually large amounts of abnormal immunoglobulins. We, therefore, hypothesized that, heat shock may also be especially toxic to myeloma cells by causing protein unfolding, increasing further the substrate load on proteasomes, and, thus, putting further stress on their capacity for protein homeostasis. After a shift from 37 to 43 °C, all four myeloma lines studied underwent extensive apoptosis in 4 h, unlike 13 nonmyeloma cell lines, even though the myeloma cells induced heat-shock proteins and increased protein degradation similar to other cells. Furthermore, two myeloma lines resistant to proteasome inhibitors were also more resistant to 43 °C. Shifting myeloma cells to 43, 41, or 39 °C (which was not cytotoxic) dramatically increased their killing by proteasome inhibitors and inhibitors of ubiquitination or p97/VCP. Combining increased temperature with BTZ increased the accumulation of misfolded proteins and substrate load on the 26S proteasome. The apoptosis seen at 43 °C and at 39 °C with BTZ was mediated by caspase-9 and was linked to an accumulation of the proapoptotic Bcl-2-family member Noxa. Thus, myeloma cells are exceptionally sensitive to increased temperatures, which greatly increase substrate load on the ubiquitin-proteasome system and eventually activate the intrinsic apoptotic pathway. Consequently, for myeloma, mild hyperthermia may be a beneficial approach to enhance the therapeutic efficacy of proteasome inhibitors.
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22
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Chidamide epigenetically represses autophagy and exerts cooperative antimyeloma activity with bortezomib. Cell Death Dis 2020; 11:297. [PMID: 32341332 PMCID: PMC7186232 DOI: 10.1038/s41419-020-2414-3] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2019] [Revised: 03/13/2020] [Accepted: 03/16/2020] [Indexed: 12/14/2022]
Abstract
Autophagy and ubiquitin proteasome system are two distinct and cooperative proteolytic pathways. The dual-pathway suppression represents a promising therapeutic strategy for multiple myeloma. Chidamide is a novel benzamide inhibitor of histone deacetylase, and shows potent antimyeloma activity. Here, we revealed the autophagy-suppressive role of chidamide in myeloma cells. We then demonstrated that chidamide treatment markedly downregulated histone deacetylase SIRT1, and simultaneously resulted in dose-dependent upregulation of acetyltransferase hMOF and histone methyltransferase EZH2, which contributed to an increase in global levels of histone H4 lysine 16 acetylation (H4k16ac) and histone H3 lysine 27 trimethylation (H3k27me3). We next confirmed concomitant upregulation of H4k16ac and H3k27me3 in the same promoter regions of the autophagy-related gene LC3B, reinforcing the specific roles for H4k16ac and H3k27me3 in mediating chidamide-induced transcriptional repression of LC3B. Finally, we provided experimental evidence that co-treatment with chidamide and proteasome inhibitor bortezomib induced clear synergistic cytotoxicity against MM cells, which was associated with increased accumulation of ubiquitinated proteins and excessive endoplasmic reticulum stress or dysregulated unfolded protein response. Our results altogether suggest that chidamide cooperatively potentiates antimyeloma activity of bortezomib, at least in part, by epigenetically repressing autophagic degradation of ubiquitinated proteins.
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23
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Gewehr MCF, Silverio R, Rosa-Neto JC, Lira FS, Reckziegel P, Ferro ES. Peptides from Natural or Rationally Designed Sources Can Be Used in Overweight, Obesity, and Type 2 Diabetes Therapies. Molecules 2020; 25:E1093. [PMID: 32121443 PMCID: PMC7179135 DOI: 10.3390/molecules25051093] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2020] [Revised: 02/20/2020] [Accepted: 02/25/2020] [Indexed: 12/18/2022] Open
Abstract
Overweight and obesity are among the most prominent health problems in the modern world, mostly because they are either associated with or increase the risk of other diseases such as type 2 diabetes, hypertension, and/or cancer. Most professional organizations define overweight and obesity according to individual body-mass index (BMI, weight in kilograms divided by height squared in meters). Overweight is defined as individuals with BMI from 25 to 29, and obesity as individuals with BMI ≥30. Obesity is the result of genetic, behavioral, environmental, physiological, social, and cultural factors that result in energy imbalance and promote excessive fat deposition. Despite all the knowledge concerning the pathophysiology of obesity, which is considered a disease, none of the existing treatments alone or in combination can normalize blood glucose concentration and prevent debilitating complications from obesity. This review discusses some new perspectives for overweight and obesity treatments, including the use of the new orally active cannabinoid peptide Pep19, the advantage of which is the absence of undesired central nervous system effects usually experienced with other cannabinoids.
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Affiliation(s)
- Mayara C. F. Gewehr
- Department of Pharmacology, Biomedical Sciences Institute, University of São Paulo (USP), São Paulo 05508-000, Brazil;
| | - Renata Silverio
- Department of Pharmacology, Center of Biological Sciences, Federal University of Santa Catarina (UFSC), Florianópolis 88040-900, Brazil;
| | - José Cesar Rosa-Neto
- Department of Cell and Developmental Biology, Biomedical Sciences Institute, University of São Paulo (USP), São Paulo 05508-000, Brazil;
| | - Fabio S. Lira
- Department of Physical Education, São Paulo State University (UNESP), Presidente Prudente 19060-900, Brazil;
| | - Patrícia Reckziegel
- Department of Pharmacology, National Institute of Pharmacology and Molecular Biology (INFAR), Federal University of São Paulo (UNIFESP), São Paulo 05508-000, Brazil;
| | - Emer S. Ferro
- Department of Pharmacology, Biomedical Sciences Institute, University of São Paulo (USP), São Paulo 05508-000, Brazil;
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24
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Coleman RA, Trader DJ. Methods to Discover and Evaluate Proteasome Small Molecule Stimulators. Molecules 2019; 24:molecules24122341. [PMID: 31242677 PMCID: PMC6630500 DOI: 10.3390/molecules24122341] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2019] [Revised: 06/18/2019] [Accepted: 06/22/2019] [Indexed: 11/25/2022] Open
Abstract
Protein accumulation has been identified as a characteristic of many degenerative conditions, such as neurodegenerative diseases and aging. In most cases, these conditions also present with diminished protein degradation. The ubiquitin-proteasome system (UPS) is responsible for the degradation of the majority of proteins in cells; however, the activity of the proteasome is reduced in these disease states, contributing to the accumulation of toxic protein. It has been hypothesized that proteasome activity, both ubiquitin-dependent and -independent, can be chemically stimulated to reduce the load of protein in diseased cells. Several methods exist to identify and characterize stimulators of proteasome activity. In this review, we detail the ways in which protease activity can be enhanced and analyze the biochemical and cellular methods of identifying stimulators of both the ubiquitin-dependent and -independent proteasome activities.
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Affiliation(s)
- Rachel A Coleman
- Department of Medicinal Chemistry and Molecular Pharmacology, Purdue University, 610 Purdue Mall, West Lafayette, IN 47907, USA.
| | - Darci J Trader
- Department of Medicinal Chemistry and Molecular Pharmacology, Purdue University, 610 Purdue Mall, West Lafayette, IN 47907, USA.
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25
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Abstract
The ubiquitin proteasome system (UPS) degrades individual proteins in a highly regulated fashion and is responsible for the degradation of misfolded, damaged, or unneeded cellular proteins. During the past 20 years, investigators have established a critical role for the UPS in essentially every cellular process, including cell cycle progression, transcriptional regulation, genome integrity, apoptosis, immune responses, and neuronal plasticity. At the center of the UPS is the proteasome, a large and complex molecular machine containing a multicatalytic protease complex. When the efficiency of this proteostasis system is perturbed, misfolded and damaged protein aggregates can accumulate to toxic levels and cause neuronal dysfunction, which may underlie many neurodegenerative diseases. In addition, many cancers rely on robust proteasome activity for degrading tumor suppressors and cell cycle checkpoint inhibitors necessary for rapid cell division. Thus, proteasome inhibitors have proven clinically useful to treat some types of cancer, especially multiple myeloma. Numerous cellular processes rely on finely tuned proteasome function, making it a crucial target for future therapeutic intervention in many diseases, including neurodegenerative diseases, cystic fibrosis, atherosclerosis, autoimmune diseases, diabetes, and cancer. In this review, we discuss the structure and function of the proteasome, the mechanisms of action of different proteasome inhibitors, various techniques to evaluate proteasome function in vitro and in vivo, proteasome inhibitors in preclinical and clinical development, and the feasibility for pharmacological activation of the proteasome to potentially treat neurodegenerative disease.
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Affiliation(s)
- Tiffany A Thibaudeau
- Department of Biochemistry, West Virginia University School of Medicine, Morgantown, West Virginia
| | - David M Smith
- Department of Biochemistry, West Virginia University School of Medicine, Morgantown, West Virginia
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26
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26S Proteasomes are rapidly activated by diverse hormones and physiological states that raise cAMP and cause Rpn6 phosphorylation. Proc Natl Acad Sci U S A 2019; 116:4228-4237. [PMID: 30782827 DOI: 10.1073/pnas.1809254116] [Citation(s) in RCA: 78] [Impact Index Per Article: 15.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Pharmacological agents that raise cAMP and activate protein kinase A (PKA) stimulate 26S proteasome activity, phosphorylation of subunit Rpn6, and intracellular degradation of misfolded proteins. We investigated whether a similar proteasome activation occurs in response to hormones and under various physiological conditions that raise cAMP. Treatment of mouse hepatocytes with glucagon, epinephrine, or forskolin stimulated Rpn6 phosphorylation and the 26S proteasomes' capacity to degrade ubiquitinated proteins and peptides. These agents promoted the selective degradation of short-lived proteins, which are misfolded and regulatory proteins, but not the bulk of cell proteins or lysosomal proteolysis. Proteasome activities and Rpn6 phosphorylation increased similarly in working hearts upon epinephrine treatment, in skeletal muscles of exercising humans, and in electrically stimulated rat muscles. In WT mouse kidney cells, but not in cells lacking PKA, treatment with antidiuretic hormone (vasopressin) stimulated within 5-minutes proteasomal activity, Rpn6 phosphorylation, and the selective degradation of short-lived cell proteins. In livers and muscles of mice fasted for 12-48 hours cAMP levels, Rpn6 phosphorylation, and proteasomal activities increased without any change in proteasomal content. Thus, in vivo cAMP-PKA-mediated proteasome activation is a common cellular response to diverse endocrine stimuli and rapidly enhances the capacity of target tissues to degrade regulatory and misfolded proteins (e.g., proteins damaged upon exercise). The increased destruction of preexistent regulatory proteins may help cells adapt their protein composition to new physiological conditions.
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