1
|
Jang HS, Lee Y, Kim Y, Huh WK. The ubiquitin-proteasome system degrades fatty acid synthase under nitrogen starvation when autophagy is dysfunctional in Saccharomyces cerevisiae. Biochem Biophys Res Commun 2024; 733:150423. [PMID: 39053108 DOI: 10.1016/j.bbrc.2024.150423] [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: 07/11/2024] [Revised: 07/15/2024] [Accepted: 07/17/2024] [Indexed: 07/27/2024]
Abstract
Autophagy and the ubiquitin-proteasome system (UPS) are two major protein quality control mechanisms maintaining cellular proteostasis. In Saccharomyces cerevisiae, the de novo synthesis of saturated fatty acids is performed by a multienzyme complex known as fatty acid synthase (FAS). A recent study reported that yeast FAS is preferentially degraded by autophagy under nitrogen starvation. In this study, we examined the fate of FAS during nitrogen starvation when autophagy is dysfunctional. We found that the UPS compensates for FAS degradation in the absence of autophagy. Additionally, we discovered that the UPS-dependent degradation of Fas2 requires the E3 ubiquitin ligase Ubr1. Our findings highlight the complementary relationship between autophagy and the UPS.
Collapse
Affiliation(s)
- Hae-Soo Jang
- School of Biological Sciences, Seoul National University, Seoul, 08826, Republic of Korea
| | - Yongook Lee
- School of Biological Sciences, Seoul National University, Seoul, 08826, Republic of Korea
| | - Yeonsoo Kim
- School of Biological Sciences, Seoul National University, Seoul, 08826, Republic of Korea
| | - Won-Ki Huh
- School of Biological Sciences, Seoul National University, Seoul, 08826, Republic of Korea; Institute of Microbiology, Seoul National University, Seoul, 08826, Republic of Korea.
| |
Collapse
|
2
|
Shen L. Functional interdependence of N6-methyladenosine methyltransferase complex subunits in Arabidopsis. THE PLANT CELL 2023; 35:1901-1916. [PMID: 36890720 PMCID: PMC10226572 DOI: 10.1093/plcell/koad070] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/05/2023] [Revised: 02/22/2023] [Accepted: 02/24/2023] [Indexed: 05/30/2023]
Abstract
Addition of N6-methyladenosine (m6A), the most prevalent internal mRNA modification in eukaryotes, is catalyzed by an evolutionarily conserved m6A methyltransferase complex. In the model plant Arabidopsis thaliana, the m6A methyltransferase complex is composed of 2 core methyltransferases, mRNA adenosine methylase (MTA) and MTB, and several accessory subunits such as FK506-BINDING PROTEIN 12 KD INTERACTING PROTEIN 37KD (FIP37), VIRILIZER (VIR), and HAKAI. It is yet largely unknown whether these accessory subunits influence the functions of MTA and MTB. Herein, I reveal that FIP37 and VIR are indispensable for stabilizing the methyltransferases MTA and MTB, thus functioning as key subunits to maintain the functionality of the m6A methyltransferase complex. Furthermore, VIR affects FIP37 and HAKAI protein accumulation, while MTA and MTB mutually influence each other. In contrast, HAKAI has little effect on protein abundance or localization of MTA, MTB, and FIP37. These findings uncover unique functional interdependence at the post-translational level among individual components in the Arabidopsis m6A methyltransferase complex, suggesting that maintenance of protein homeostasis among various subunits of the m6A methyltransferase complex is essential for maintaining the protein stoichiometry required for the proper function of the m6A methyltransferase complex in m6A deposition in plants.
Collapse
Affiliation(s)
- Lisha Shen
- Temasek Life Sciences Laboratory, National University of Singapore, 1 Research Link, 117604, Singapore, Singapore
- Department of Biological Sciences, Faculty of Science, National University of Singapore, 117543, Singapore, Singapore
| |
Collapse
|
3
|
Pulse labeling reveals the tail end of protein folding by proteome profiling. Cell Rep 2022; 40:111096. [PMID: 35858568 PMCID: PMC9893312 DOI: 10.1016/j.celrep.2022.111096] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2021] [Revised: 05/18/2022] [Accepted: 06/23/2022] [Indexed: 02/04/2023] Open
Abstract
Accurate and efficient folding of nascent protein sequences into their native states requires support from the protein homeostasis network. Herein we probe which newly translated proteins are thermo-sensitive, making them susceptible to misfolding and aggregation under heat stress using pulse-SILAC mass spectrometry. We find a distinct group of proteins that is highly sensitive to this perturbation when newly synthesized but not once matured. These proteins are abundant and highly structured. Notably, they display a tendency to form β sheet secondary structures, have more complex folding topology, and are enriched for chaperone-binding motifs, suggesting a higher demand for chaperone-assisted folding. These polypeptides are also more often components of stable protein complexes in comparison with other proteins. Combining these findings suggests the existence of a specific subset of proteins in the cell that is particularly vulnerable to misfolding and aggregation following synthesis before reaching the native state.
Collapse
|
4
|
Hsu KL, Yen HCS, Yeang CH. Cooperative stability renders protein complex formation more robust and controllable. Sci Rep 2022; 12:10490. [PMID: 35729235 PMCID: PMC9213465 DOI: 10.1038/s41598-022-14362-z] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2021] [Accepted: 06/06/2022] [Indexed: 11/19/2022] Open
Abstract
Protein complexes are the fundamental units of many biological functions. Despite their many advantages, one major adverse impact of protein complexes is accumulations of unassembled subunits that may disrupt other processes or exert cytotoxic effects. Synthesis of excess subunits can be inhibited via negative feedback control or they can be degraded more efficiently than assembled subunits, with this latter being termed cooperative stability. Whereas controlled synthesis of complex subunits has been investigated extensively, how cooperative stability acts in complex formation remains largely unexplored. To fill this knowledge gap, we have built quantitative models of heteromeric complexes with or without cooperative stability and compared their behaviours in the presence of synthesis rate variations. A system displaying cooperative stability is robust against synthesis rate variations as it retains high dimer/monomer ratios across a broad range of parameter configurations. Moreover, cooperative stability can alleviate the constraint of limited supply of a given subunit and makes complex abundance more responsive to unilateral upregulation of another subunit. We also conducted an in silico experiment to comprehensively characterize and compare four types of circuits that incorporate combinations of negative feedback control and cooperative stability in terms of eight systems characteristics pertaining to optimality, robustness and controllability. Intriguingly, though individual circuits prevailed for distinct characteristics, the system with cooperative stability alone achieved the most balanced performance across all characteristics. Our study provides theoretical justification for the contribution of cooperative stability to natural biological systems and represents a guideline for designing synthetic complex formation systems with desirable characteristics.
Collapse
Affiliation(s)
- Kuan-Lun Hsu
- Institute of Molecular Biology, Academia Sinica, 128 Academia Road, Section 2, Taipei, Taiwan
| | - Hsueh-Chi S Yen
- Institute of Molecular Biology, Academia Sinica, 128 Academia Road, Section 2, Taipei, Taiwan
| | - Chen-Hsiang Yeang
- Institute of Statistical Science, Academia Sinica, 128 Academia Road, Section 2, Taipei, Taiwan.
| |
Collapse
|
5
|
Kong KYE, Coelho JPL, Feige MJ, Khmelinskii A. Quality control of mislocalized and orphan proteins. Exp Cell Res 2021; 403:112617. [PMID: 33930402 DOI: 10.1016/j.yexcr.2021.112617] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2020] [Revised: 04/10/2021] [Accepted: 04/18/2021] [Indexed: 12/16/2022]
Abstract
A healthy and functional proteome is essential to cell physiology. However, this is constantly being challenged as most steps of protein metabolism are error-prone and changes in the physico-chemical environment can affect protein structure and function, thereby disrupting proteome homeostasis. Among a variety of potential mistakes, proteins can be targeted to incorrect compartments or subunits of protein complexes may fail to assemble properly with their partners, resulting in the formation of mislocalized and orphan proteins, respectively. Quality control systems are in place to handle these aberrant proteins, and to minimize their detrimental impact on cellular functions. Here, we discuss recent findings on quality control mechanisms handling mislocalized and orphan proteins. We highlight common principles involved in their recognition and summarize how accumulation of these aberrant molecules is associated with aging and disease.
Collapse
Affiliation(s)
| | - João P L Coelho
- Department of Chemistry and Institute for Advanced Study, Technical University of Munich, Garching, Germany
| | - Matthias J Feige
- Department of Chemistry and Institute for Advanced Study, Technical University of Munich, Garching, Germany
| | | |
Collapse
|
6
|
Fusing α and β subunits of the fungal fatty acid synthase leads to improved production of fatty acids. Sci Rep 2020; 10:9780. [PMID: 32555375 PMCID: PMC7300031 DOI: 10.1038/s41598-020-66629-y] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2020] [Accepted: 05/25/2020] [Indexed: 01/18/2023] Open
Abstract
Most fungal fatty acid synthases assemble from two multidomain subunits, α and β, into a heterododecameric FAS complex. It has been recently shown that the complex assembly occurs in a cotranslational manner and is initiated by an interaction between the termini of α and β subunits. This initial engagement of subunits may be the rate-limiting phase of the assembly and subject to cellular regulation. Therefore, we hypothesized that bypassing this step by genetically fusing the subunits could be beneficial for biotechnological production of fatty acids. To test the concept, we expressed fused FAS subunits engineered for production of octanoic acid in Saccharomyces cerevisiae. Collectively, our data indicate that FAS activity is a limiting factor of fatty acid production and that FAS fusion proteins show a superior performance compared to their split counterparts. This strategy is likely a generalizable approach to optimize the production of fatty acids and derived compounds in microbial chassis organisms.
Collapse
|
7
|
Metzger MB, Scales JL, Dunklebarger MF, Loncarek J, Weissman AM. A protein quality control pathway at the mitochondrial outer membrane. eLife 2020; 9:51065. [PMID: 32118579 PMCID: PMC7136024 DOI: 10.7554/elife.51065] [Citation(s) in RCA: 33] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2019] [Accepted: 03/01/2020] [Indexed: 12/27/2022] Open
Abstract
Maintaining the essential functions of mitochondria requires mechanisms to recognize and remove misfolded proteins. However, quality control (QC) pathways for misfolded mitochondrial proteins remain poorly defined. Here, we establish temperature-sensitive (ts-) peripheral mitochondrial outer membrane (MOM) proteins as novel model QC substrates in Saccharomyces cerevisiae. The ts- proteins sen2-1HAts and sam35-2HAts are degraded from the MOM by the ubiquitin-proteasome system. Ubiquitination of sen2-1HAts is mediated by the ubiquitin ligase (E3) Ubr1, while sam35-2HAts is ubiquitinated primarily by San1. Mitochondria-associated degradation (MAD) of both substrates requires the SSA family of Hsp70s and the Hsp40 Sis1, providing the first evidence for chaperone involvement in MAD. In addition to a role for the Cdc48-Npl4-Ufd1 AAA-ATPase complex, Doa1 and a mitochondrial pool of the transmembrane Cdc48 adaptor, Ubx2, are implicated in their degradation. This study reveals a unique QC pathway comprised of a combination of cytosolic and mitochondrial factors that distinguish it from other cellular QC pathways.
Collapse
Affiliation(s)
- Meredith B Metzger
- Laboratory of Protein Dynamics and Signaling, Center for Cancer Research, National Cancer Institute at Frederick, Frederick, United States
| | - Jessica L Scales
- Laboratory of Protein Dynamics and Signaling, Center for Cancer Research, National Cancer Institute at Frederick, Frederick, United States
| | - Mitchell F Dunklebarger
- Laboratory of Protein Dynamics and Signaling, Center for Cancer Research, National Cancer Institute at Frederick, Frederick, United States
| | - Jadranka Loncarek
- Laboratory of Protein Dynamics and Signaling, Center for Cancer Research, National Cancer Institute at Frederick, Frederick, United States
| | - Allan M Weissman
- Laboratory of Protein Dynamics and Signaling, Center for Cancer Research, National Cancer Institute at Frederick, Frederick, United States
| |
Collapse
|
8
|
Hegde RS, Zavodszky E. Recognition and Degradation of Mislocalized Proteins in Health and Disease. Cold Spring Harb Perspect Biol 2019; 11:cshperspect.a033902. [PMID: 30833453 DOI: 10.1101/cshperspect.a033902] [Citation(s) in RCA: 38] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
A defining feature of eukaryotic cells is the segregation of complex biochemical processes among different intracellular compartments. The protein targeting, translocation, and trafficking pathways that sustain compartmentalization must recognize a diverse range of clients via degenerate signals. This recognition is imperfect, resulting in polypeptides at incorrect cellular locations. Cells have evolved mechanisms to selectively recognize mislocalized proteins and triage them for degradation or rescue. These spatial quality control pathways maintain cellular protein homeostasis, become especially important during organelle stress, and might contribute to disease when they are impaired or overwhelmed.
Collapse
Affiliation(s)
- Ramanujan S Hegde
- Medical Research Council Laboratory of Molecular Biology, Cambridge CB2 0QH, United Kingdom
| | - Eszter Zavodszky
- Medical Research Council Laboratory of Molecular Biology, Cambridge CB2 0QH, United Kingdom
| |
Collapse
|
9
|
Ella H, Reiss Y, Ravid T. The Hunt for Degrons of the 26S Proteasome. Biomolecules 2019; 9:biom9060230. [PMID: 31200568 PMCID: PMC6628059 DOI: 10.3390/biom9060230] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2019] [Revised: 06/10/2019] [Accepted: 06/11/2019] [Indexed: 02/05/2023] Open
Abstract
Since the discovery of ubiquitin conjugation as a cellular mechanism that triggers proteasomal degradation, the mode of substrate recognition by the ubiquitin-ligation system has been the holy grail of research in the field. This entails the discovery of recognition determinants within protein substrates, which are part of a degron, and explicit E3 ubiquitin (Ub)-protein ligases that trigger their degradation. Indeed, many protein substrates and their cognate E3′s have been discovered in the past 40 years. In the course of these studies, various degrons have been randomly identified, most of which are acquired through post-translational modification, typically, but not exclusively, protein phosphorylation. Nevertheless, acquired degrons cannot account for the vast diversity in cellular protein half-life times. Obviously, regulation of the proteome is largely determined by inherent degrons, that is, determinants integral to the protein structure. Inherent degrons are difficult to predict since they consist of diverse sequence and secondary structure features. Therefore, unbiased methods have been employed for their discovery. This review describes the history of degron discovery methods, including the development of high throughput screening methods, state of the art data acquisition and data analysis. Additionally, it summarizes major discoveries that led to the identification of cognate E3 ligases and hitherto unrecognized complexities of degron function. Finally, we discuss future perspectives and what still needs to be accomplished towards achieving the goal of understanding how the eukaryotic proteome is regulated via coordinated action of components of the ubiquitin-proteasome system.
Collapse
Affiliation(s)
- Hadar Ella
- Department of Biological Chemistry, Institute of Life Sciences, the Hebrew University of Jerusalem, Jerusalem 91904, Israel.
| | - Yuval Reiss
- Department of Biological Chemistry, Institute of Life Sciences, the Hebrew University of Jerusalem, Jerusalem 91904, Israel.
| | - Tommer Ravid
- Department of Biological Chemistry, Institute of Life Sciences, the Hebrew University of Jerusalem, Jerusalem 91904, Israel.
| |
Collapse
|
10
|
Tran A. The N-end rule pathway and Ubr1 enforce protein compartmentalization via P2-encoded cellular location signals. J Cell Sci 2019; 132:jcs.231662. [PMID: 30940687 DOI: 10.1242/jcs.231662] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2019] [Accepted: 03/22/2019] [Indexed: 12/24/2022] Open
Abstract
The Arg/N-end rule pathway and Ubr1, a ubiquitin E3 ligase conserved from yeast to humans, is involved in the degradation of misfolded proteins in the cytosol. However, the root physiological purpose of this activity is not completely understood. Through a systematic examination of single-residue P2-position mutants of misfolded proteins, and global and targeted bioinformatic analyses of the Saccharomyces cerevisiae proteome, it was determined that Ubr1 preferentially targets mistranslocated secretory and mitochondrial proteins in the cytosol. Degradation by Ubr1 is dependent on the recognition of cellular location signals that are naturally embedded into the second amino acid residue of most proteins. This P2-encoded location signaling mechanism may shed light on how Ubr1 and the N-end rule pathway are involved in neurodegenerative diseases such as Alzheimer's and Parkinson's diseases. A corollary to this discovery is that the N-end rule pathway enforces the compartmentalization of secretory and mitochondrial proteins by degrading those that fail to reach their intended subcellular locations. The N-end rule pathway is therefore likely to have been critical to the evolution of endosymbiotic relationships that paved the way for advanced eukaryotic cellular life. This article has an associated First Person interview with the first author of the paper.
Collapse
Affiliation(s)
- Anthony Tran
- National University of Singapore, Department of Biological Sciences, Singapore 117604
| |
Collapse
|
11
|
Cotranslational assembly of protein complexes in eukaryotes revealed by ribosome profiling. Nature 2018; 561:268-272. [PMID: 30158700 PMCID: PMC6372068 DOI: 10.1038/s41586-018-0462-y] [Citation(s) in RCA: 192] [Impact Index Per Article: 32.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2017] [Accepted: 08/02/2018] [Indexed: 02/07/2023]
Abstract
The folding of newly synthesized proteins to the native state is a major
challenge within the crowded cellular environment, as non-productive
interactions can lead to misfolding, aggregation and degradation1. Cells cope with this challenge by
coupling synthesis with polypeptide folding and by using molecular chaperones to
safeguard folding cotranslationally2.
However, although most of the cellular proteome forms oligomeric assemblies3, little is known about the final step of
folding: the assembly of polypeptides into complexes. In prokaryotes, a
proof-of-concept study showed that the assembly of heterodimeric luciferase is
an organized cotranslational process that is facilitated by spatially confined
translation of the subunits encoded on a polycistronic mRNA4. In eukaryotes, however, fundamental
differences—such as the rarity of polycistronic mRNAs and different
chaperone constellations—raise the question of whether assembly is also
coordinated with translation. Here we provide a systematic and mechanistic
analysis of the assembly of protein complexes in eukaryotes using ribosome
profiling. We determined the in vivo interactions of the
nascent subunits from twelve hetero-oligomeric protein complexes of
Saccharomyces cerevisiae at near-residue resolution. We
find nine complexes assemble cotranslationally; the three complexes that do not
show cotranslational interactions are regulated by dedicated assembly
chaperones5–7. Cotranslational assembly often occurs
uni-directionally, with one fully synthesized subunit engaging its nascent
partner subunit, thereby counteracting its propensity for aggregation. The onset
of cotranslational subunit association coincides directly with the full exposure
of the nascent interaction domain at the ribosomal tunnel exit. The
ribosome-associated Hsp70 chaperone Ssb8
is coordinated with assembly. Ssb transiently engages partially synthesized
interaction domains and then dissociates before the onset of partner subunit
association, presumably to prevent premature assembly interactions. Our study
shows that cotranslational subunit association is a prevalent mechanism for the
assembly of hetero-oligomers in yeast and indicates that translation, folding
and assembly of protein complexes are integrated processes in eukaryotes.
Collapse
|
12
|
Abstract
The billions of proteins inside a eukaryotic cell are organized among dozens of sub-cellular compartments, within which they are further organized into protein complexes. The maintenance of both levels of organization is crucial for normal cellular function. Newly made proteins that fail to be segregated to the correct compartment or assembled into the appropriate complex are defined as orphans. In this review, we discuss the challenges faced by a cell of minimizing orphaned proteins, the quality control systems that recognize orphans, and the consequences of excess orphans for protein homeostasis and disease.
Collapse
|
13
|
Wolf DH, Menssen R. Mechanisms of cell regulation - proteolysis, the big surprise. FEBS Lett 2018; 592:2515-2524. [PMID: 29790175 DOI: 10.1002/1873-3468.13109] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2018] [Revised: 05/16/2018] [Accepted: 05/17/2018] [Indexed: 11/09/2022]
Abstract
Precise regulation of cellular processes is essential for life. Regarding proteins, many regulatory mechanisms were explored over the years, such as posttranslational modifications (e.g., phosphorylation), enzyme activation or inhibition by small molecules, and modulation of protein-protein interactions. Complete removal of a protein via proteolysis as a regulatory mechanism, however, was denied for a long time, mainly due to economical considerations. Scientists could not believe that a protein which is synthesized at the expense of a lot of energy could be destroyed again. Here, we discuss the landmark discoveries and the use of yeast as a eukaryotic model organism that finally paved the way for our current understanding of proteolysis as an essential regulatory principle in the cell.
Collapse
Affiliation(s)
- Dieter H Wolf
- Department of Biochemistry, Institute of Biochemistry and Technical Biochemistry, Stuttgart University, Germany
| | - Ruth Menssen
- Department of Biochemistry, Institute of Biochemistry and Technical Biochemistry, Stuttgart University, Germany
| |
Collapse
|
14
|
Xu Y, Anderson DE, Ye Y. The HECT domain ubiquitin ligase HUWE1 targets unassembled soluble proteins for degradation. Cell Discov 2016; 2:16040. [PMID: 27867533 PMCID: PMC5102030 DOI: 10.1038/celldisc.2016.40] [Citation(s) in RCA: 51] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2016] [Accepted: 10/17/2016] [Indexed: 12/18/2022] Open
Abstract
In eukaryotes, many proteins function in multi-subunit complexes that require
proper assembly. To maintain complex stoichiometry, cells use the endoplasmic
reticulum-associated degradation system to degrade unassembled membrane
subunits, but how unassembled soluble proteins are eliminated is undefined. Here
we show that degradation of unassembled soluble proteins (referred to as
unassembled soluble protein degradation, USPD) requires the ubiquitin selective
chaperone p97, its co-factor nuclear protein localization protein 4 (Npl4), and
the proteasome. At the ubiquitin ligase level, the previously identified protein
quality control ligase UBR1 (ubiquitin protein ligase E3 component n-recognin 1)
and the related enzymes only process a subset of unassembled soluble proteins.
We identify the homologous to the E6-AP carboxyl terminus (homologous to the
E6-AP carboxyl terminus) domain-containing protein HUWE1 as a ubiquitin ligase
for substrates bearing unshielded, hydrophobic segments. We used a stable
isotope labeling with amino acids-based proteomic approach to identify
endogenous HUWE1 substrates. Interestingly, many HUWE1 substrates form
multi-protein complexes that function in the nucleus although HUWE1 itself is
cytoplasmically localized. Inhibition of nuclear entry enhances HUWE1-mediated
ubiquitination and degradation, suggesting that USPD occurs primarily in the
cytoplasm. Altogether, these findings establish a new branch of the cytosolic
protein quality control network, which removes surplus polypeptides to control
protein homeostasis and nuclear complex assembly.
Collapse
Affiliation(s)
- Yue Xu
- Laboratory of Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health , Bethesda, MD, USA
| | - D Eric Anderson
- Advanced Mass Spectrometry Core Facility, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health , Bethesda, MD, USA
| | - Yihong Ye
- Laboratory of Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health , Bethesda, MD, USA
| |
Collapse
|
15
|
Harper JW, Bennett EJ. Proteome complexity and the forces that drive proteome imbalance. Nature 2016; 537:328-38. [PMID: 27629639 DOI: 10.1038/nature19947] [Citation(s) in RCA: 163] [Impact Index Per Article: 20.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2016] [Accepted: 07/29/2016] [Indexed: 12/28/2022]
Abstract
The cellular proteome is a complex microcosm of structural and regulatory networks that requires continuous surveillance and modification to meet the dynamic needs of the cell. It is therefore crucial that the protein flux of the cell remains in balance to ensure proper cell function. Genetic alterations that range from chromosome imbalance to oncogene activation can affect the speed, fidelity and capacity of protein biogenesis and degradation systems, which often results in proteome imbalance. An improved understanding of the causes and consequences of proteome imbalance is helping to reveal how these systems can be targeted to treat diseases such as cancer.
Collapse
Affiliation(s)
- J Wade Harper
- Department of Cell Biology, Harvard Medical School, Boston, Massachusetts 02115, USA
| | - Eric J Bennett
- Section of Cell and Developmental Biology, Division of Biological Sciences, University of California, San Diego, La Jolla, California 92093, USA
| |
Collapse
|
16
|
Characterization of protein quality control components via dual reporter-containing misfolded cytosolic model substrates. Anal Biochem 2016; 515:14-21. [PMID: 27670725 DOI: 10.1016/j.ab.2016.09.012] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2016] [Revised: 08/26/2016] [Accepted: 09/14/2016] [Indexed: 11/20/2022]
Abstract
Protein misfolding and protein aggregation are causes of severe diseases as neurodegenerative disorders, diabetes and cancer. Therefore, the cell has to constantly monitor the folding status of its proteome. Chaperones and components of the ubiquitin-proteasome system are key players in the cellular protein quality control process. In order to characterize components of the protein quality control system in a well-established model eukaryote - the yeast Saccharomyces cerevisiae - we established new cytosolic model substrates based on firefly luciferase and β-isopropylmalate dehydrogenase (Leu2). The use of these two different enzymes arranged in tandem as reporters enabled us to analyse the folding status and the degradation propensity of these new model substrates in yeast cells mutated in components of the cellular protein quality control system. The Hsp70 chaperone system known to be essential in the cellular protein quality control was chosen as a model for showing the high value of the luciferase-based model substrates in the characterization of components of the cytosolic protein quality control system in yeast.
Collapse
|
17
|
Amm I, Wolf DH. Molecular mass as a determinant for nuclear San1-dependent targeting of misfolded cytosolic proteins to proteasomal degradation. FEBS Lett 2016; 590:1765-75. [PMID: 27173001 DOI: 10.1002/1873-3468.12213] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2015] [Revised: 05/04/2016] [Accepted: 05/08/2016] [Indexed: 11/08/2022]
Abstract
Most misfolded cytosolic proteins in the cell are eliminated by the ubiquitin-proteasome system. In yeast, polyubiquitination of misfolded cytosolic proteins is triggered mainly by the action of two ubiquitin ligases Ubr1, formerly discovered as recognition component of the N-end rule pathway, and the nuclear ubiquitin ligase San1. For San1-mediated targeting to proteasomal degradation, cytosolic proteins have to be imported into the nucleus. Selection of misfolded substrates for import into the nucleus had remained elusive. This study shows that an increasing molecular mass of substrates prevents nuclear San1-triggered proteasomal degradation but renders them susceptible to cytoplasmic Ubr1-triggered degradation.
Collapse
Affiliation(s)
- Ingo Amm
- Institut für Biochemie, Universität Stuttgart, Germany
| | - Dieter H Wolf
- Institut für Biochemie, Universität Stuttgart, Germany
| |
Collapse
|
18
|
Lee KE, Heo JE, Kim JM, Hwang CS. N-Terminal Acetylation-Targeted N-End Rule Proteolytic System: The Ac/N-End Rule Pathway. Mol Cells 2016; 39:169-78. [PMID: 26883906 PMCID: PMC4794598 DOI: 10.14348/molcells.2016.2329] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2015] [Revised: 01/11/2016] [Accepted: 01/14/2016] [Indexed: 12/12/2022] Open
Abstract
Although Nα-terminal acetylation (Nt-acetylation) is a pervasive protein modification in eukaryotes, its general functions in a majority of proteins are poorly understood. In 2010, it was discovered that Nt-acetylation creates a specific protein degradation signal that is targeted by a new class of the N-end rule proteolytic system, called the Ac/N-end rule pathway. Here, we review recent advances in our understanding of the mechanism and biological functions of the Ac/N-end rule pathway, and its crosstalk with the Arg/N-end rule pathway (the classical N-end rule pathway).
Collapse
Affiliation(s)
- Kang-Eun Lee
- Department of Life Sciences, Pohang University of Science and Technology, Pohang, Gyeongbuk 790–784,
Korea
| | - Ji-Eun Heo
- Department of Life Sciences, Pohang University of Science and Technology, Pohang, Gyeongbuk 790–784,
Korea
| | - Jeong-Mok Kim
- Department of Life Sciences, Pohang University of Science and Technology, Pohang, Gyeongbuk 790–784,
Korea
| | - Cheol-Sang Hwang
- Department of Life Sciences, Pohang University of Science and Technology, Pohang, Gyeongbuk 790–784,
Korea
| |
Collapse
|
19
|
Failure of RQC machinery causes protein aggregation and proteotoxic stress. Nature 2016; 531:191-5. [DOI: 10.1038/nature16973] [Citation(s) in RCA: 147] [Impact Index Per Article: 18.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2015] [Accepted: 01/07/2016] [Indexed: 12/12/2022]
|
20
|
Chen L, Zhang YH, Huang T, Cai YD. Identifying novel protein phenotype annotations by hybridizing protein-protein interactions and protein sequence similarities. Mol Genet Genomics 2016; 291:913-34. [PMID: 26728152 DOI: 10.1007/s00438-015-1157-9] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2015] [Accepted: 12/08/2015] [Indexed: 01/18/2023]
Abstract
Studies of protein phenotypes represent a central challenge of modern genetics in the post-genome era because effective and accurate investigation of protein phenotypes is one of the most critical procedures to identify functional biological processes in microscale, which involves the analysis of multifactorial traits and has greatly contributed to the development of modern biology in the post genome era. Therefore, we have developed a novel computational method that identifies novel proteins associated with certain phenotypes in yeast based on the protein-protein interaction network. Unlike some existing network-based computational methods that identify the phenotype of a query protein based on its direct neighbors in the local network, the proposed method identifies novel candidate proteins for a certain phenotype by considering all annotated proteins with this phenotype on the global network using a shortest path (SP) algorithm. The identified proteins are further filtered using both a permutation test and their interactions and sequence similarities to annotated proteins. We compared our method with another widely used method called random walk with restart (RWR). The biological functions of proteins for each phenotype identified by our SP method and the RWR method were analyzed and compared. The results confirmed a large proportion of our novel protein phenotype annotation, and the RWR method showed a higher false positive rate than the SP method. Our method is equally effective for the prediction of proteins involving in all the eleven clustered yeast phenotypes with a quite low false positive rate. Considering the universality and generalizability of our supporting materials and computing strategies, our method can further be applied to study other organisms and the new functions we predicted can provide pertinent instructions for the further experimental verifications.
Collapse
Affiliation(s)
- Lei Chen
- School of Life Sciences, Shanghai University, Shanghai, 200444, People's Republic of China. .,College of Information Engineering, Shanghai Maritime University, Shanghai, 201306, People's Republic of China.
| | - Yu-Hang Zhang
- Institute of Health Sciences, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai, 200031, People's Republic of China
| | - Tao Huang
- Institute of Health Sciences, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai, 200031, People's Republic of China
| | - Yu-Dong Cai
- School of Life Sciences, Shanghai University, Shanghai, 200444, People's Republic of China.
| |
Collapse
|
21
|
Amm I, Norell D, Wolf DH. Absence of the Yeast Hsp31 Chaperones of the DJ-1 Superfamily Perturbs Cytoplasmic Protein Quality Control in Late Growth Phase. PLoS One 2015; 10:e0140363. [PMID: 26466368 PMCID: PMC4605529 DOI: 10.1371/journal.pone.0140363] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2015] [Accepted: 09/24/2015] [Indexed: 01/26/2023] Open
Abstract
The Saccharomyces cerevisiae heat shock proteins Hsp31, Hsp32, Hsp33 and Hsp34 belong to the DJ-1/ThiJ/PfpI superfamily which includes the human protein DJ-1 (PARK7) as the most prominent member. Mutations in the DJ-1 gene are directly linked to autosomal recessive, early-onset Parkinson's disease. DJ-1 acts as an oxidative stress-induced chaperone preventing aggregation and fibrillation of α-synuclein, a critical factor in the development of the disease. In vivo assays in Saccharomyces cerevisiae using the model substrate ΔssCPY*Leu2myc (ΔssCL*myc) as an aggregation-prone misfolded cytoplasmic protein revealed an influence of the Hsp31 chaperone family on the steady state level of this substrate. In contrast to the ubiquitin ligase of the N-end rule pathway Ubr1, which is known to be prominently involved in the degradation process of misfolded cytoplasmic proteins, the absence of the Hsp31 chaperone family does not impair the degradation of newly synthesized misfolded substrate. Also degradation of substrates with strong affinity to Ubr1 like those containing the type 1 N-degron arginine is not affected by the absence of the Hsp31 chaperone family. Epistasis analysis indicates that one function of the Hsp31 chaperone family resides in a pathway overlapping with the Ubr1-dependent degradation of misfolded cytoplasmic proteins. This pathway gains relevance in late growth phase under conditions of nutrient limitation. Additionally, the Hsp31 chaperones seem to be important for maintaining the cellular Ssa Hsp70 activity which is important for Ubr1-dependent degradation.
Collapse
Affiliation(s)
- Ingo Amm
- Institut für Biochemie, Universität Stuttgart, Pfaffenwaldring 55, Stuttgart, Germany
| | - Derrick Norell
- Institut für Biochemie, Universität Stuttgart, Pfaffenwaldring 55, Stuttgart, Germany
| | - Dieter H. Wolf
- Institut für Biochemie, Universität Stuttgart, Pfaffenwaldring 55, Stuttgart, Germany
| |
Collapse
|