Protein homeostasis is maintained by proteasomes containing PSMB9 induced by EEF1A2 upon mitochondrial stress
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ABSTRACT:
ORGANISM(S): Homo sapiens
PROVIDER: GSE196068 | GEO | 2023/05/31
REPOSITORIES: GEO
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Project description:Perturbed proteostasis and mitochondrial dysfunction are often associated with age-related diseases such as Alzheimer’s and Parkinson’s diseases. However, the link between them remains incompletely understood. Mitochondrial dysfunction causes proteostasis imbalance, and cells respond to restore proteostasis by increasing proteasome activity and molecular chaperons in yeast and C. elegans. Here, we demonstrate the presence of similar responses in humans. Mitochondrial dysfunction upregulates a small heat shock protein HSPB1 and an immunoproteasome subunit PSMB9 leading to an increase in proteasome activity. HSPB1 and PSMB9 are required to prevent protein aggregation upon mitochondrial dysfunction. Moreover, PSMB9 expression is dependent on a translation elongation factor EEF1A2, and PSMB9-containing proteasomes are located near mitochondria, enabling fast local degradation of aberrant proteins. Our findings put a step forward in understanding the stress response triggered by mitochondrial dysfunction, and may be useful for therapeutic strategies to prevent or delay the onset of age-related diseases and attenuate their progression.
2023-07-03 | PXD031374 | Pride
Project description:Perturbed proteostasis and mitochondrial dysfunction are often associated with age-related diseases such as Alzheimer’s and Parkinson’s diseases. However, the link between them remains incompletely understood. Mitochondrial dysfunction causes proteostasis imbalance, and cells respond to restore proteostasis by increasing proteasome activity and molecular chaperons in yeast and C. elegans. Here, we demonstrate the presence of similar responses in humans. Mitochondrial dysfunction upregulates a small heat shock protein HSPB1 and an immunoproteasome subunit PSMB9 leading to an increase in proteasome activity. HSPB1 and PSMB9 are required to prevent protein aggregation upon mitochondrial dysfunction. Moreover, PSMB9 expression is dependent on a translation elongation factor EEF1A2, and PSMB9-containing proteasomes are located near mitochondria, enabling fast local degradation of aberrant proteins. Our findings put a step forward in understanding the stress response triggered by mitochondrial dysfunction, and may be useful for therapeutic strategies to prevent or delay the onset of age-related diseases and attenuate their progression.
2023-07-04 | PXD031282 | Pride
Project description:Protein homeostasis is maintained by proteasomes containing PSMB9 induced by EEF1A2 upon mitochondrial stress
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Project description:Protein degradation in eukaryotic cells is mainly carried out by the 26S proteasome, a macromolecular complex not only present in the cytosol and nucleus but also associated with various membranes. How proteasomes are anchored to the membrane and the biological meaning thereof have been largely unknown in higher organisms. Here, we show that N-myristoylation of the Rpt2 subunit is a general mechanism for proteasome-membrane interaction. Loss of this modification in the Rpt2-G2A mutant cells leads to profound changes in the membrane-associated proteome, perturbs the endomembrane system, and undermines critical cellular processes such as cell adhesion, endoplasmic reticulum-associated degradation and membrane protein trafficking. Rpt2G2A/G2A homozygous mutation is embryonic lethal in mice and is sufficient to abolish tumor growth in a nude mice xenograft model. These findings have defined an evolutionarily conserved mechanism for maintaining membrane protein homeostasis and underscored the significance of compartmentalized protein degradation by myristoyl-anchored proteasomes in health and disease.
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Project description:As the major protein degradation machinery of eukaryotic cells, the 26S proteasome is generally thought to localize in the nucleus and cytosol. A portion of proteasomes are known to associate with various membrane structures of the cell, the mechanism and biological meaning of which have been elusive. Here we show that N-myristoylation of the proteasome subunit Rpt2 is an evolutionarily conserved determinant of proteasome-membrane interaction. Loss of this modification leads to embryonic lethality in mice, significant reduction of migration ability in MEFs and profound changes in the membrane-associated proteome as determined by SILAC-MS, suggesting a key role of membrane-tethered proteasomes in carrying out compartmentalized protein degradation. And the tumorigenicity is reduced in the oncogene-transformed MEF without modification. Serendipitously, we found that the Rpt2-G2A mutation cell lines confers partial resistance to proteasome inhibitors, such as Bortezomib and MG132. Thus, N-myristoylation of Rpt2 determines the localization and activity of the proteasome at the membrane, which is critical for embryogenesis, cellular homeostasis and tumorigenesis.
2023-05-16 | GSE232308 | GEO
Project description:Stemness encompasses the capability of a cell for self-renewal and differentiation. The stem cell maintains a balance between proliferation, quiescence, and regeneration via interactions with the microenvironment. Previously, we showed that ectopic expression of the mitochondrial ribosomal protein S18-2 (MRPS18-2) led to immortalization of primary fibroblasts, accompanied by induction of an embryonic stem cell (ESC) phenotype. Moreover, we demonstrated interaction between S18-2 and the retinoblastoma-associated protein (RB) and hypothesized that the simultaneous expression of RB and S18-2 is essential for maintaining cell stemness. Here, we experimentally investigated the role of S18-2 in cell stemness and differentiation. Concurrent expression of RB and S18-2 resulted in immortalization of Rb1 -/- primary mouse embryonic fibroblasts and in aggressive tumor growth in severe combined immunodeficiency mice. These cells, which express both RB and S18-2 at high levels, exhibited the potential to differentiate into various lineages in vitro, including osteogenic, chondrogenic, and adipogenic lineages. Mechanistically, S18-2 formed a multimeric protein complex with prohibitin and the ring finger protein 2 (RNF2). This molecular complex increased the monoubiquitination of histone H2ALys119, a characteristic trait of ESCs, by enhanced E3-ligase activity of RNF2. Furthermore, we found enrichment of KLF4 at the S18-2 promoter region and that the S18-2 expression is positively correlated with KLF4 levels. Importantly, knockdown of S18-2 in zebrafish larvae led to embryonic lethality. Collectively, our findings suggest an important role for S18-2 in cell stemness and differentiation and potentially also in cancerogenesis.
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Project description:Lipid-anchored Proteasomes Control Membrane Protein Homeostasis
| PRJNA971586 | ENA
Project description:When cells are stressed, bulk translation is often downregulated to reduce energy demands while stress-response proteins are simultaneously upregulated. To promote proteasome assembly and activity and maintain cell viability upon TORC1 inhibition, 19S regulatory-particle assembly chaperones (RPACs) are selectively translated. However, the molecular mechanism for such selective translational upregulation is unclear. Here, using yeast, we discover that remodelling of the actin cytoskeleton is important for RPAC translation following TORC1 inhibition. mRNA of the RPAC ADC17 is associated with actin cables and is enriched at cortical actin patches under stress, dependent upon the early endocytic protein Ede1. ede1∆ cells failed to induce RPACs and proteasome assembly upon TORC1 inhibition. Conversely, artificially tethering ADC17 mRNA to cortical actin patches enhanced its translation upon stress. These findings suggest that actin-dense structures such as cortical actin patches may serve as a translation platform for a subset of stress-induced mRNAs including regulators of proteasome homeostasis.
| S-EPMC9276530 | biostudies-literature
Project description: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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Project description:BackgroundGene regulatory networks control tissue homeostasis and disease progression in a cell type-specific manner. Ubiquitously expressed chromatin regulators modulate these networks, yet the mechanisms governing how tissue specificity of their function is achieved are poorly understood. BRD4 (bromodomain-containing protein 4), a member of the BET (bromo- and extraterminal domain) family of ubiquitously expressed acetyl-lysine reader proteins, plays a pivotal role as a coactivator of enhancer signaling across diverse tissue types in both health and disease and has been implicated as a pharmacological target in heart failure. However, the cell-specific role of BRD4 in adult cardiomyocytes remains unknown.MethodsWe combined conditional mouse genetics, unbiased transcriptomic and epigenomic analyses, and classic molecular biology and biochemical approaches to understand the mechanism by which BRD4 in adult cardiomyocyte homeostasis.ResultsHere, we show that cardiomyocyte-specific deletion of Brd4 in adult mice leads to acute deterioration of cardiac contractile function with mutant animals demonstrating a transcriptomic signature characterized by decreased expression of genes critical for mitochondrial energy production. Genome-wide occupancy data show that BRD4 enriches at many downregulated genes (including the master coactivators Ppargc1a, Ppargc1b, and their downstream targets) and preferentially colocalizes with GATA4 (GATA binding protein 4), a lineage-determining cardiac transcription factor not previously implicated in regulation of adult cardiac metabolism. BRD4 and GATA4 form an endogenous complex in cardiomyocytes and interact in a bromodomain-independent manner, revealing a new functional interaction partner for BRD4 that can direct its locus and tissue specificity.ConclusionsThese results highlight a novel role for a BRD4-GATA4 module in cooperative regulation of a cardiomyocyte-specific gene program governing bioenergetic homeostasis in the adult heart.
| S-EPMC7736290 | biostudies-literature