| 1. |
- Andersson, Rebecca, et al.
(författare)
-
Differential role of cytosolic Hsp70s in longevity assurance and protein quality control
- 2021
-
Ingår i: PLoS Genetics. - : Public Library of Science (PLoS). - 1553-7404 .- 1553-7390. ; 17:1
-
Tidskriftsartikel (refereegranskat)abstract
- 70 kDa heat shock proteins (Hsp70) are essential chaperones of the protein quality control network; vital for cellular fitness and longevity. The four cytosolic Hsp70's in yeast, Ssa1-4, are thought to be functionally redundant but the absence of Ssa1 and Ssa2 causes a severe reduction in cellular reproduction and accelerates replicative aging. In our efforts to identify which Hsp70 activities are most important for longevity assurance, we systematically investigated the capacity of Ssa4 to carry out the different activities performed by Ssa1/2 by overproducing Ssa4 in cells lacking these Hsp70 chaperones. We found that Ssa4, when overproduced in cells lacking Ssa1/2, rescued growth, mitigated aggregate formation, restored spatial deposition of aggregates into protein inclusions, and promoted protein degradation. In contrast, Ssa4 overproduction in the Hsp70 deficient cells failed to restore the recruitment of the disaggregase Hsp104 to misfolded/aggregated proteins, to fully restore clearance of protein aggregates, and to bring back the formation of the nucleolus-associated aggregation compartment. Exchanging the nucleotide-binding domain of Ssa4 with that of Ssa1 suppressed this 'defect' of Ssa4. Interestingly, Ssa4 overproduction extended the short lifespan of ssa1 Delta ssa2 Delta mutant cells to a lifespan comparable to, or even longer than, wild type cells, demonstrating that Hsp104-dependent aggregate clearance is not a prerequisite for longevity assurance in yeast. Author summary All organisms have proteins that network together to stabilize and protect the cell throughout its lifetime. One of these types of proteins are the Hsp70s (heat shock protein 70). Hsp70 proteins take part in folding other proteins to their functional form, untangling proteins from aggregates, organize aggregates inside the cell and ensure that damaged proteins are destroyed. In this study, we investigated three closely related Hsp70 proteins in yeast; Ssa1, 2 and 4, in an effort to describe the functional difference of Ssa4 compared to Ssa1 and 2 and to answer the question: What types of cellular stress protection are necessary to reach a normal lifespan? We show that Ssa4 can perform many of the same tasks as Ssa1 and 2, but Ssa4 doesn't interact in the same manner as Ssa1 and 2 with other types of proteins. This leads to a delay in removing protein aggregates created after heat stress. Ssa4 also cannot ensure that misfolded proteins aggregate correctly inside the nucleus of the cell. However, this turns out not to be necessary for yeast cells to achieve a full lifespan, which shows us that as long as cells can prevent aggregates from forming in the first place, they can reach a full lifespan.
|
|
| 2. |
- Caballero, Antonio, et al.
(författare)
-
Absence of mitochondrial translation control proteins extends life span by activating sirtuin-dependent silencing.
- 2011
-
Ingår i: Molecular cell. - : Elsevier BV. - 1097-4164 .- 1097-2765. ; 42:3, s. 390-400
-
Tidskriftsartikel (refereegranskat)abstract
- Altered mitochondrial functionality can extend organism life span, but the underlying mechanisms are obscure. Here we report that inactivating SOV1, a member of the yeast mitochondrial translation control (MTC) module, causes a robust Sir2-dependent extension of replicative life span in the absence of respiration and without affecting oxidative damage. We found that SOV1 interacts genetically with the cAMP-PKA pathway and the chromatin remodeling apparatus. Consistently, Sov1p-deficient cells displayed reduced cAMP-PKA signaling and an elevated, Sir2p-dependent, genomic silencing. Both increased silencing and life span extension in sov1Δ cells require the PKA/Msn2/4p target Pnc1p, which scavenges nicotinamide, a Sir2p inhibitor. Inactivating other members of the MTC module also resulted in Sir2p-dependent life span extension. The data demonstrate that the nuclear silencing apparatus senses and responds to the absence of MTC proteins and that this response converges with a pathway for life span extension elicited by reducing TOR signaling.
|
|
| 3. |
|
|
| 4. |
- Liu, Beidong, 1972, et al.
(författare)
-
The Polarisome Is Required for Segregation and Retrograde Transport of Protein Aggregates
- 2010
-
Ingår i: Cell. - 0092-8674. ; 140:2, s. 257-267
-
Tidskriftsartikel (refereegranskat)abstract
- The paradigm sirtuin, Sir2p, of budding yeast is required for establishing cellular age asymmetry, which includes the retention of damaged and aggregated proteins in mother cells. By establishing the global genetic interaction network of SIR2 we identified the polarisome, the formin Bni1p, and myosin motor protein Myo2p as essential components of the machinery segregating protein aggregates during mitotic cytokinesis. Moreover, we found that daughter cells can clear themselves of damage by a polarisome- and tropomyosin-dependent polarized flow of aggregates into the mother cell compartment. The role of Sir2p in cytoskeletal functions and polarity is linked to the CCT chaperonin in sir2Δ cells being compromised in folding actin. We discuss the findings in view of recent models hypothesizing that polarity may have evolved to avoid clonal senescence by establishing an aging (soma-like) and rejuvenated (germ-like) lineage.
|
|
| 5. |
- Öling, David, et al.
(författare)
-
Loss of Ubp3 increases Silencing, decreases Unequal Recombination in rDNA, and shortens the Replicative Life Span in Saccharomyces cerevisiae.
- 2014
-
Ingår i: Molecular Biology of the Cell. - 1059-1524. ; 25:12, s. 1916-1924
-
Tidskriftsartikel (refereegranskat)abstract
- Ubp3 is a conserved ubiquitin protease that acts as an antisilencing factor in MAT and telomeric regions. Here we show that ubp3∆ mutants also display increased silencing in ribosomal DNA (rDNA). Consistent with this, RNA polymerase II occupancy is lower in cells lacking Ubp3 than in wild-type cells in all heterochromatic regions. Moreover, in a ubp3∆ mutant, unequal recombination in rDNA is highly suppressed. We present genetic evidence that this effect on rDNA recombination, but not silencing, is entirely dependent on the silencing factor Sir2. Further, ubp3∆ sir2∆ mutants age prematurely at the same rate as sir2∆ mutants. Thus our data suggest that recombination negatively influences replicative life span more so than silencing. However, in ubp3∆ mutants, recombination is not a prerequisite for aging, since cells lacking Ubp3 have a shorter life span than isogenic wild-type cells. We discuss the data in view of different models on how silencing and unequal recombination affect replicative life span and the role of Ubp3 in these processes.
|
|
| 6. |
- Öling, David
(författare)
-
On aging and the role of Ubp3 in heterochromatic gene silencing and protein quality control
- 2014
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Aging is characterized by a build-up of damage in organisms ranging from protists to multi-cellular species. This damage adversely affects core components such as DNA and proteins which are necessary to sustain life. Remarkably, as an old yeast cell divides, its daughter cell is fully rejuvenated suggesting that age-related damage can be asymmetrically inherited and/or completely ameliorated. This thesis approaches the central question of how cells combat such damage to allow longevity. Specific interest was directed towards the deubiquitinating enzyme Ubp3 which had already been shown to be tightly linked to regulation of transcription and proteome surveillance, both of which are essential in cells adaptation to stress. In this thesis, I show that cells lacking Ubp3 are short-lived despite displaying decreased unequal recombination at rDNA and increased silencing at all three heterochromatic regions in S. cerevisiae subjected to transcriptional silencing. These findings are at odds with existing aging-models in yeast, highlighting that increased silencing at rDNA is associated with long lifespan. Instead, our data suggest that premature aging in cells devoid of UBP3 is caused by a pathway other than rDNA recombination/silencing. Indeed, I found that Ubp3 has an important dual role in protein quality control by saving or destroying aberrant protein species depending on the stage at which the damaged protein is committed for proteasomal destruction. Furthermore, in virgin and young cells lacking UBP3, aggregated proteins accumulated prematurely at a juxta-nuclear position whereas wild-type cells showed no indication of protein damage. In middle-aged and older cells in the same mutant, more aggregates accumulated at a peripheral location. This accumulation of peripheral aggregates correlated, in time, with a decline in mutant cell survival. Similar to Ubp3, the well-characterized silencing-factor Sir2 is known to regulate other aging-processes unlinked to silencing. We show that Sir2-deficient cells display increased daughter cell inheritance of stress and age-induced misfolded proteins deposited in aggregates and inclusion bodies. This asymmetric inheritance has been argued to take place in a passive manner due to slow and random diffusion of aggregates. We present evidence that this is not a plausible scenario. The control of damage inheritance is more likely mediated by Sir2-dependent regulation of the chaperonin CCT which is required for folding actin and feeding the polarisome with properly folded substrates. We discuss data underlying these conflicting models and seek to understand which model best explains how damage asymmetry is achieved.
|
|
| 7. |
- Öling, David, et al.
(författare)
-
Opposing roles of Ubp3-dependent deubiquitination regulate replicative life span and heat resistance
- 2014
-
Ingår i: Embo Journal. - : Wiley. - 0261-4189 .- 1460-2075. ; 33:7, s. 747-761
-
Tidskriftsartikel (refereegranskat)abstract
- Abstract The interplay between molecular chaperones, ubiquitin/deubiquitinating enzymes, and proteasomes is a critical element in protein homeostasis. Among these factors, the conserved deubiquitinase, Ubp3, has the interesting ability, when overproduced, to suppress the requirement for the major cytosolic Hsp70 chaperones. Here, we show that Ubp3 overproduction counteracts deficiency of Hsp70s by the removal of damaged proteins deposited in inclusion bodies (JUNQ) during both aging and heat stress. Consistent with this, Ubp3 destabilized, deubiquitinated, and diminished the toxicity of the JUNQ-associated misfolded protein Ubc9(ts) in a proteasome-dependent manner. In contrast, another misfolded model protein, increment ssCPY*, was stabilized by Ubp3-dependent deubiquitination demonstrating a dual role for Ubp3, saving or destroying aberrant protein species depending on the stage at which the damaged protein is committed for destruction. We present genetic evidence for the former of these activities being key to Ubp3-dependent suppression of heat sensitivity in Hsp70-deficient cells, whereas protein destruction suppresses accelerated aging. We discuss the data in view of how heat stress and aging might elicit differential damage and challenges on the protein homeostasis network. The conserved deubiquitinase Ubp3 regulates both heat stress resistance and replicative life span in yeast through dual roles in cellular protein homeostasis. Ubp3 aids removal of damaged proteins either by stabilizing them in a rescue pathway or by accelerating their proteasome-mediated degradation. Ubp3 promotes the removal of damaged proteins deposited in JUNQ inclusion bodies. Misfolded model proteins are either stabilized or degraded by Ubp3 overproduction. Ubp3 suppresses heat sensitivity in Hsp70-deficient cells by diverting damaged proteins from destruction. Ubp3-mediated proteasomal degradation of cytotoxic proteins suppresses accelerated replicative aging.
|
|
