Additional file 2. Individual data values. Spreadsheets of numerical data for Figures 1, 2, 3, 4 ... more Additional file 2. Individual data values. Spreadsheets of numerical data for Figures 1, 2, 3, 4 and 5 and Supplementary Figures S1-S4.
Background Mitochondrial DNA (mtDNA) is present at high copy numbers in animal cells, and though ... more Background Mitochondrial DNA (mtDNA) is present at high copy numbers in animal cells, and though characterized by a single haplotype in each individual due to maternal germline inheritance, deleterious mutations and intact mtDNA molecules frequently co-exist (heteroplasmy). A number of factors, such as replicative segregation, mitochondrial bottlenecks, and selection, may modulate the exitance of heteroplasmic mutations. Since such mutations may have pathological consequences, they likely survive and are inherited due to functional complementation via the intracellular mitochondrial network. Here, we hypothesized that compromised mitochondrial fusion would hamper such complementation, thereby affecting heteroplasmy inheritance. Results We assessed heteroplasmy levels in three Caenorhabditis elegans strains carrying different heteroplasmic mtDNA deletions (ΔmtDNA) in the background of mutant mitofusin (fzo-1). Animals displayed severe embryonic lethality and developmental delay. Stri...
An amendment to this paper has been published and can be accessed via a link at the top of the pa... more An amendment to this paper has been published and can be accessed via a link at the top of the paper.
One of the critical events that regulates muscle cell differentiation is the replacement of the l... more One of the critical events that regulates muscle cell differentiation is the replacement of the lamin B receptor (LBR)-tether with the lamin A/C (LMNA)-tether to remodel transcription and induce differentiation-specific genes. Here, we report that localization and activity of the LBR-tether are crucially dependent on the muscle-specific chaperone HSPB3 and that depletion of HSPB3 prevents muscle cell differentiation. We further show that HSPB3 binds to LBR in the nucleoplasm and maintains it in a dynamic state, thus promoting the transcription of myogenic genes, including the genes to remodel the extracellular matrix. Remarkably, HSPB3 overexpression alone is sufficient to induce the differentiation of two human muscle cell lines, LHCNM2 cells, and rhabdomyosarcoma cells. We also show that mutant R116P-HSPB3 from a myopathy patient with chromatin alterations and muscle fiber disorganization, forms nuclear aggregates that immobilize LBR. We find that R116P-HSPB3 is unable to induce m...
Chaperone expression is developmentally regulated, establishing tissue-specific networks. However... more Chaperone expression is developmentally regulated, establishing tissue-specific networks. However, the molecular basis underlying this specificity is mainly unknown. Recent evidence suggests that chaperone network rewiring is mediated, in part, by differentiation transcription factors to fit the proteome folding demands, with implications for the tissue-specific manifestation of protein misfolding diseases.
The sensitivity of the protein-folding environment to chaperone disruption can be highly tissue-s... more The sensitivity of the protein-folding environment to chaperone disruption can be highly tissue-specific. Yet, the organization of the chaperone system across physiological human tissues has received little attention. Here, we used human tissue RNA-sequencing profiles to analyze the expression and organization of chaperones across 29 main tissues. We found that relative to protein-coding genes, chaperones were significantly more ubiquitously and highly expressed across all tissues. Nevertheless, differential expression analysis revealed that most chaperones were up- or down-regulated in certain tissues, suggesting that they have tissue-specific roles. In agreement, chaperones that were upregulated in skeletal muscle were highly enriched in mouse myoblasts and in nematode’s muscle tissue, and overlapped significantly with chaperones that are causal for muscle diseases. We also identified a distinct subset of chaperones that formed a uniformly-expressed, cross-family core group conduc...
Caenorhabditis elegans somatic protein homeostasis (proteostasis) is actively remodeled at the on... more Caenorhabditis elegans somatic protein homeostasis (proteostasis) is actively remodeled at the onset of reproduction. This proteostatic collapse is regulated cell-nonautonomously by signals from the reproductive system that transmit the commitment to reproduction to somatic cells. Here, we asked whether the link between the reproductive system and somatic proteostasis could be uncoupled by activating downstream effectors in the gonadal longevity cascade. Specifically, we examined whether over-expression of lipl-4 (lipl-4(oe)), a target gene of the gonadal longevity pathway, or increase in arachidonic acid (AA) levels, associated with lipl-4(oe), modulated proteostasis and reproduction. We found that lipl-4(oe) rescued somatic proteostasis and postponed the onset of aggregation and toxicity in C. elegans models of polyglutamine (polyQ) diseases. However, lipl-4(oe) also disrupted fatty acid transport into developing oocytes and reduced reproductive success. In contrast, diet suppleme...
Cell-non-autonomous signals dictate the functional state of cellular quality control systems, rem... more Cell-non-autonomous signals dictate the functional state of cellular quality control systems, remodeling the ability of cells to cope with stress and maintain protein homeostasis (proteostasis). One highly regulated cell-non-autonomous switch controls proteostatic capacity in Caenorhabditis elegans adulthood. Signals from the reproductive system down-regulate cyto-protective pathways, unless countered by signals reporting on germline proliferation disruption. Here, we utilized dihomo-γ-linolenic acid (DGLA) that depletes the C. elegans germline to ask when cell-non-autonomous signals from the reproductive system determine somatic proteostasis and whether such regulation is reversible. We found that diet supplementation of DGLA resulted in the maintenance of somatic proteostasis after the onset of reproduction. DGLA-dependent proteostasis remodeling was only effective if animals were exposed to DGLA during larval development. A short exposure of 16 h during the second to fourth larva...
Protein folding and clearance machineries are required for the maintenance and function of the pr... more Protein folding and clearance machineries are required for the maintenance and function of the proteome. Quality control systems and activation of stress signaling pathways have, therefore, profound consequences on the long-term health of the cell and, by extension, on lifespan. Aging is associated with loss of cellular function, increased vulnerability to stress, and enhanced susceptibility to disease. Over the course of a lifespan, proteome stability is substantially impacted by mutations, by processing errors, and by the acute effects of environmental stresses. Recently, the function of cellular protein quality control networks, as well as stress signaling pathways, was shown to be differentially regulated over the course of life, leading to reduced proteostasis capacity and decreased stress response activation during adulthood. Proteostatic collapse can be partially mitigated by overexpression of stress response transcription factors, such as HSF1, or by enhancing the activity of quality control systems, which can have significant beneficial effects on lifespan extension and suppression of age-related misfolding diseases. However, the link between proteostasis and lifespan can also be uncoupled, for example, by cell-nonautonomous stress signaling. Here, we will examine how proteostasis changes with age. We will then focus on HSF1 and review its roles in lifespan regulation, as well as how HSF1 function is modulated with age. Finally, we will examine the cell-nonautonomous regulation of HSF1, specifically during aging.
Numerous human diseases are associated with the chronic expression of misfolded and aggregation-p... more Numerous human diseases are associated with the chronic expression of misfolded and aggregation-prone proteins. The expansion of polyglutamine residues in unrelated proteins is associated with the early onset of neurodegenerative disease. To understand how the presence of misfolded proteins leads to cellular dysfunction, we employed Caenorhabditis elegans polyglutamine aggregation models. Here, we find that polyglutamine expansions disrupted the global balance of protein folding quality control, resulting in the loss of function of diverse metastable proteins with destabilizing temperature-sensitive mutations. In turn, these proteins, although innocuous under normal physiological conditions, enhanced the aggregation of polyglutamine proteins. Thus, weak folding mutations throughout the genome can function as modifiers of polyglutamine phenotypes and toxicity.
Proceedings of the National Academy of Sciences, 1999
A major activity of molecular chaperones is to prevent aggregation and refold misfolded proteins.... more A major activity of molecular chaperones is to prevent aggregation and refold misfolded proteins. However, when allowed to form, protein aggregates are refolded poorly by most chaperones. We show here that the sequential action of two Escherichia coli chaperone systems, ClpB and DnaK-DnaJ-GrpE, can efficiently solubilize excess amounts of protein aggregates and refold them into active proteins. Measurements of aggregate turbidity, Congo red, and 4,4′-dianilino-1,1′-binaphthyl-5,5′-disulfonic acid binding, and of the disaggregation/refolding kinetics by using a specific ClpB inhibitor, suggest a mechanism where ( i ) ClpB directly binds protein aggregates, ATP induces structural changes in ClpB, which ( ii ) increase hydrophobic exposure of the aggregates and ( iii ) allow DnaK-DnaJ-GrpE to bind and mediate dissociation and refolding of solubilized polypeptides into native proteins. This efficient mechanism, whereby chaperones can catalytically solubilize and refold a wide variety of...
Additional file 2. Individual data values. Spreadsheets of numerical data for Figures 1, 2, 3, 4 ... more Additional file 2. Individual data values. Spreadsheets of numerical data for Figures 1, 2, 3, 4 and 5 and Supplementary Figures S1-S4.
Background Mitochondrial DNA (mtDNA) is present at high copy numbers in animal cells, and though ... more Background Mitochondrial DNA (mtDNA) is present at high copy numbers in animal cells, and though characterized by a single haplotype in each individual due to maternal germline inheritance, deleterious mutations and intact mtDNA molecules frequently co-exist (heteroplasmy). A number of factors, such as replicative segregation, mitochondrial bottlenecks, and selection, may modulate the exitance of heteroplasmic mutations. Since such mutations may have pathological consequences, they likely survive and are inherited due to functional complementation via the intracellular mitochondrial network. Here, we hypothesized that compromised mitochondrial fusion would hamper such complementation, thereby affecting heteroplasmy inheritance. Results We assessed heteroplasmy levels in three Caenorhabditis elegans strains carrying different heteroplasmic mtDNA deletions (ΔmtDNA) in the background of mutant mitofusin (fzo-1). Animals displayed severe embryonic lethality and developmental delay. Stri...
An amendment to this paper has been published and can be accessed via a link at the top of the pa... more An amendment to this paper has been published and can be accessed via a link at the top of the paper.
One of the critical events that regulates muscle cell differentiation is the replacement of the l... more One of the critical events that regulates muscle cell differentiation is the replacement of the lamin B receptor (LBR)-tether with the lamin A/C (LMNA)-tether to remodel transcription and induce differentiation-specific genes. Here, we report that localization and activity of the LBR-tether are crucially dependent on the muscle-specific chaperone HSPB3 and that depletion of HSPB3 prevents muscle cell differentiation. We further show that HSPB3 binds to LBR in the nucleoplasm and maintains it in a dynamic state, thus promoting the transcription of myogenic genes, including the genes to remodel the extracellular matrix. Remarkably, HSPB3 overexpression alone is sufficient to induce the differentiation of two human muscle cell lines, LHCNM2 cells, and rhabdomyosarcoma cells. We also show that mutant R116P-HSPB3 from a myopathy patient with chromatin alterations and muscle fiber disorganization, forms nuclear aggregates that immobilize LBR. We find that R116P-HSPB3 is unable to induce m...
Chaperone expression is developmentally regulated, establishing tissue-specific networks. However... more Chaperone expression is developmentally regulated, establishing tissue-specific networks. However, the molecular basis underlying this specificity is mainly unknown. Recent evidence suggests that chaperone network rewiring is mediated, in part, by differentiation transcription factors to fit the proteome folding demands, with implications for the tissue-specific manifestation of protein misfolding diseases.
The sensitivity of the protein-folding environment to chaperone disruption can be highly tissue-s... more The sensitivity of the protein-folding environment to chaperone disruption can be highly tissue-specific. Yet, the organization of the chaperone system across physiological human tissues has received little attention. Here, we used human tissue RNA-sequencing profiles to analyze the expression and organization of chaperones across 29 main tissues. We found that relative to protein-coding genes, chaperones were significantly more ubiquitously and highly expressed across all tissues. Nevertheless, differential expression analysis revealed that most chaperones were up- or down-regulated in certain tissues, suggesting that they have tissue-specific roles. In agreement, chaperones that were upregulated in skeletal muscle were highly enriched in mouse myoblasts and in nematode’s muscle tissue, and overlapped significantly with chaperones that are causal for muscle diseases. We also identified a distinct subset of chaperones that formed a uniformly-expressed, cross-family core group conduc...
Caenorhabditis elegans somatic protein homeostasis (proteostasis) is actively remodeled at the on... more Caenorhabditis elegans somatic protein homeostasis (proteostasis) is actively remodeled at the onset of reproduction. This proteostatic collapse is regulated cell-nonautonomously by signals from the reproductive system that transmit the commitment to reproduction to somatic cells. Here, we asked whether the link between the reproductive system and somatic proteostasis could be uncoupled by activating downstream effectors in the gonadal longevity cascade. Specifically, we examined whether over-expression of lipl-4 (lipl-4(oe)), a target gene of the gonadal longevity pathway, or increase in arachidonic acid (AA) levels, associated with lipl-4(oe), modulated proteostasis and reproduction. We found that lipl-4(oe) rescued somatic proteostasis and postponed the onset of aggregation and toxicity in C. elegans models of polyglutamine (polyQ) diseases. However, lipl-4(oe) also disrupted fatty acid transport into developing oocytes and reduced reproductive success. In contrast, diet suppleme...
Cell-non-autonomous signals dictate the functional state of cellular quality control systems, rem... more Cell-non-autonomous signals dictate the functional state of cellular quality control systems, remodeling the ability of cells to cope with stress and maintain protein homeostasis (proteostasis). One highly regulated cell-non-autonomous switch controls proteostatic capacity in Caenorhabditis elegans adulthood. Signals from the reproductive system down-regulate cyto-protective pathways, unless countered by signals reporting on germline proliferation disruption. Here, we utilized dihomo-γ-linolenic acid (DGLA) that depletes the C. elegans germline to ask when cell-non-autonomous signals from the reproductive system determine somatic proteostasis and whether such regulation is reversible. We found that diet supplementation of DGLA resulted in the maintenance of somatic proteostasis after the onset of reproduction. DGLA-dependent proteostasis remodeling was only effective if animals were exposed to DGLA during larval development. A short exposure of 16 h during the second to fourth larva...
Protein folding and clearance machineries are required for the maintenance and function of the pr... more Protein folding and clearance machineries are required for the maintenance and function of the proteome. Quality control systems and activation of stress signaling pathways have, therefore, profound consequences on the long-term health of the cell and, by extension, on lifespan. Aging is associated with loss of cellular function, increased vulnerability to stress, and enhanced susceptibility to disease. Over the course of a lifespan, proteome stability is substantially impacted by mutations, by processing errors, and by the acute effects of environmental stresses. Recently, the function of cellular protein quality control networks, as well as stress signaling pathways, was shown to be differentially regulated over the course of life, leading to reduced proteostasis capacity and decreased stress response activation during adulthood. Proteostatic collapse can be partially mitigated by overexpression of stress response transcription factors, such as HSF1, or by enhancing the activity of quality control systems, which can have significant beneficial effects on lifespan extension and suppression of age-related misfolding diseases. However, the link between proteostasis and lifespan can also be uncoupled, for example, by cell-nonautonomous stress signaling. Here, we will examine how proteostasis changes with age. We will then focus on HSF1 and review its roles in lifespan regulation, as well as how HSF1 function is modulated with age. Finally, we will examine the cell-nonautonomous regulation of HSF1, specifically during aging.
Numerous human diseases are associated with the chronic expression of misfolded and aggregation-p... more Numerous human diseases are associated with the chronic expression of misfolded and aggregation-prone proteins. The expansion of polyglutamine residues in unrelated proteins is associated with the early onset of neurodegenerative disease. To understand how the presence of misfolded proteins leads to cellular dysfunction, we employed Caenorhabditis elegans polyglutamine aggregation models. Here, we find that polyglutamine expansions disrupted the global balance of protein folding quality control, resulting in the loss of function of diverse metastable proteins with destabilizing temperature-sensitive mutations. In turn, these proteins, although innocuous under normal physiological conditions, enhanced the aggregation of polyglutamine proteins. Thus, weak folding mutations throughout the genome can function as modifiers of polyglutamine phenotypes and toxicity.
Proceedings of the National Academy of Sciences, 1999
A major activity of molecular chaperones is to prevent aggregation and refold misfolded proteins.... more A major activity of molecular chaperones is to prevent aggregation and refold misfolded proteins. However, when allowed to form, protein aggregates are refolded poorly by most chaperones. We show here that the sequential action of two Escherichia coli chaperone systems, ClpB and DnaK-DnaJ-GrpE, can efficiently solubilize excess amounts of protein aggregates and refold them into active proteins. Measurements of aggregate turbidity, Congo red, and 4,4′-dianilino-1,1′-binaphthyl-5,5′-disulfonic acid binding, and of the disaggregation/refolding kinetics by using a specific ClpB inhibitor, suggest a mechanism where ( i ) ClpB directly binds protein aggregates, ATP induces structural changes in ClpB, which ( ii ) increase hydrophobic exposure of the aggregates and ( iii ) allow DnaK-DnaJ-GrpE to bind and mediate dissociation and refolding of solubilized polypeptides into native proteins. This efficient mechanism, whereby chaperones can catalytically solubilize and refold a wide variety of...
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