Richard Morimoto - Profile on Academia.edu (original) (raw)

Papers by Richard Morimoto

Research paper thumbnail of Regulation of the Cellular Heat Shock Response in <i>Caenorhabditis elegans</i> by Thermosensory Neurons

Research paper thumbnail of Polyglutamine aggregates alter protein folding homeostasis in <i>Caenorhabditis elegans</i>

Proceedings of the National Academy of Sciences of the United States of America, May 16, 2000

Expansion of polyglutamine repeats in several unrelated proteins causes neurodegenerative disease... more Expansion of polyglutamine repeats in several unrelated proteins causes neurodegenerative diseases with distinct but related pathologies. To provide a model system for investigating common pathogenic features, we have examined the behavior of polyglutamine expansions expressed in Caenorhabditis elegans. The expression of polyglutamine repeats as green fluorescent protein (GFP)-fusion proteins in body wall muscle cells causes discrete cytoplasmic aggregates that appear early in embryogenesis and correlates with a delay in larval to adult development. The heat shock response is activated idiosyncratically in individual cells in a polyglutamine length-dependent fashion. The toxic effect of polyglutamine expression and the formation of aggregates can be reversed by coexpression of the yeast chaperone Hsp104. The altered homeostasis associated with polyglutamine aggregates causes both the sequestration of an otherwise soluble protein with shorter arrays of glutamine repeats and the relocalization of a nuclear glutamine-rich protein. These observations of induced aggregation and relocalization have implications for disorders involving protein aggregation.

Research paper thumbnail of Dynamic Imaging by Fluorescence Correlation Spectroscopy Identifies Diverse Populations of Polyglutamine Oligomers Formed in Vivo

Journal of Biological Chemistry, Jul 1, 2012

Background: Protein aggregation is implicated in numerous diseases. Results: Polyglutamine oligom... more Background: Protein aggregation is implicated in numerous diseases. Results: Polyglutamine oligomers maintain a heterogeneous distribution that reaches an equilibrium during aging and can be altered by genetic modifiers that suppress aggregation. Conclusion: Shifts in populations of oligomers do not correlate with toxicity. Significance: The dynamics of oligomerization and aggregation to inert species is essential for protein misfolding and toxicity. Protein misfolding and aggregation are exacerbated by aging and diseases of protein conformation including neurodegeneration, metabolic diseases, and cancer. In the cellular environment, aggregates can exist as discrete entities, or heterogeneous complexes of diverse solubility and conformational state. In this study, we have examined the in vivo dynamics of aggregation using imaging methods including fluorescence microscopy, fluorescence recovery after photobleaching (FRAP), and fluorescence correlation spectroscopy (FCS), to monitor the diverse biophysical states of expanded polyglutamine (polyQ) proteins expressed in Caenorhabditis elegans. We show that monomers, oligomers and aggregates co-exist at different concentrations in young and aged animals expressing different polyQ-lengths. During aging, when aggregation and toxicity are exacerbated, FCS-based burst analysis and purified single molecule FCS detected a populational shift toward an increase in the frequency of brighter and larger oligomeric species. Regardless of age or polyQ-length, oligomers were maintained in a heterogeneous distribution that spans multiple orders of magnitude in brightness. We employed genetic suppressors that prevent polyQ aggregation and observed a reduction in visible immobile species with the persistence of heterogeneous oligomers, yet our analysis did not detect the appearance of any discrete oligomeric states associated with toxicity. These studies reveal that the reversible transition from monomers to immobile aggregates is not represented by discrete oligomeric states, but rather suggests that the process of aggregation involves a more complex pattern of molecular interactions of diverse intermediate species that can appear in vivo and contribute to aggregate formation and toxicity.

Research paper thumbnail of Cytosolic chaperonin prevents polyglutamine toxicity with altering the aggregation state

Nature Cell Biology, Sep 17, 2006

Research paper thumbnail of Disease-Modifying Pathways in Neurodegeneration

The Journal of Neuroscience, Oct 11, 2006

Research paper thumbnail of Protein homeostasis of a metastable subproteome associated with Alzheimer’s disease

Proceedings of the National Academy of Sciences of the United States of America, Jun 26, 2017

Research paper thumbnail of Selective activation of human heat shock gene transcription by nitrosourea antitumor drugs mediated by isocyanate-induced damage and activation of heat shock transcription factor

Proceedings of the National Academy of Sciences of the United States of America, Jun 1, 1991

Treatment of cultured human tumor cells with the chloroethylnitrosourea antitumor drug 1,3-bis(2-... more Treatment of cultured human tumor cells with the chloroethylnitrosourea antitumor drug 1,3-bis(2- chloroethyl)-l-nitrosourea (BCNU) selectively induces tran- scription and protein synthesis of a subset of the human heat shock or stress-induced genes (HSP90 and HSP70) with little effect on other stress genes or on expression of the c-fos, c-myc, or .8-actin genes. The active component of BCNU and related compounds appears to be the isocyanate moiety that causes carbamoylation of proteins and nucleic acids. Transcriptional activation of the human HSP70 gene by BCNU is dependent on the heat shock element and correlates with the level of heat shock transcription factor and its binding to the heat shock element in vivo. Unlike activation by heat or heavy metals, BCNU-mediated activation is strongly dependent upon new protein synthesis. This suggests that BCNU-induced, isocyanate-mediated damage to newly synthesized protein(s) may be responsible for activation of the heat shock transcription factor and increased transcription of the HSP90 and HSP70 genes.

Research paper thumbnail of HSF1 transcription factor concentrates in nuclear foci during heat shock: relationship with transcription sites

Journal of Cell Science, 1997

In this paper, we show that upon heat shock, HSF1 concentrates in the nucleus of diploid human fi... more In this paper, we show that upon heat shock, HSF1 concentrates in the nucleus of diploid human fibroblasts in two large foci. The relative distribution of HSF1 nuclear foci and active heat shock protein (hsp) genes was investigated by combining fluorescence in situ hybridization (FISH) for the detection of hsp nuclear transcripts and immunofluorescence for the detection of HSF1. We show that the HSF1 foci are distinct from the sites of hsp70 and hsp90 genes transcription. This is the second report of ploidy-dependent foci of transcription factors that are independent of their specific transcription sites. However, the correlation between the number of HSF1 foci and the ploidy of the cells strongly supports the existence of a specific chromosomal target for HSF1 foci.

Research paper thumbnail of Proteotoxic stress and ageing triggers the loss of redox homeostasis across cellular compartments

The EMBO journal, Jan 14, 2015

The cellular proteostasis network integrates the protein folding and clearance machineries in mul... more The cellular proteostasis network integrates the protein folding and clearance machineries in multiple sub-cellular compartments of the eukaryotic cell. The endoplasmic reticulum (ER) is the site of synthesis and folding of membrane and secretory proteins. A distinctive feature of the ER is its tightly controlled redox homeostasis necessary for the formation of inter- and intra-molecular disulphide bonds. Employing genetically encoded in vivo sensors reporting on the redox state in an organelle-specific manner, we show in the nematode Caenorhabditis elegans that the redox state of the ER is subject to profound changes during worm lifetime. In young animals, the ER is oxidizing and this shifts towards reducing conditions during ageing, whereas in the cytosol the redox state becomes more oxidizing with age. Likewise, the redox state in the cytosol and the ER change in an opposing manner in response to proteotoxic challenges in C. elegans and in HeLa cells revealing conservation of red...

Research paper thumbnail of Serotonergic signalling suppresses ataxin 3 aggregation and neurotoxicity in animal models of Machado-Joseph disease

Brain : a journal of neurology, Jan 15, 2015

Polyglutamine diseases are a class of dominantly inherited neurodegenerative disorders for which ... more Polyglutamine diseases are a class of dominantly inherited neurodegenerative disorders for which there is no effective treatment. Here we provide evidence that activation of serotonergic signalling is beneficial in animal models of Machado-Joseph disease. We identified citalopram, a selective serotonin reuptake inhibitor, in a small molecule screen of FDA-approved drugs that rescued neuronal dysfunction and reduced aggregation using a Caenorhabditis elegans model of mutant ataxin 3-induced neurotoxicity. MOD-5, the C. elegans orthologue of the serotonin transporter and cellular target of citalopram, and the serotonin receptors SER-1 and SER-4 were strong genetic modifiers of ataxin 3 neurotoxicity and necessary for therapeutic efficacy. Moreover, chronic treatment of CMVMJD135 mice with citalopram significantly reduced ataxin 3 neuronal inclusions and astrogliosis, rescued diminished body weight and strikingly ameliorated motor symptoms. These results suggest that small molecule mod...

Research paper thumbnail of Modeling Polyglutamine Pathogenesis in C. elegans

Methods in Enzymology, 2006

A growing number of human neurodegenerative diseases are associated with disruption of cellular p... more A growing number of human neurodegenerative diseases are associated with disruption of cellular protein folding homeostasis, leading to the appearance of misfolded proteins and deposition of protein aggregates and inclusions. Recent years have been witness to widespread development of invertebrate systems (specifically Drosophila and Caenorhabditis elegans) to model these disorders, bringing the many advantages of such systems, particularly the power of genetic analysis in a metazoan, to bear on these problems. In this chapter, we describe our studies using the nematode, C. elegans, as a model to study polyglutamine expansions as occur in Huntington's disease and related ataxias. Using fluorescently tagged polyglutamine repeats of different lengths, we have examined the dynamics of aggregate formation both within individual cells and over time throughout the lifetime of individual organisms, identifying aging as an important physiological determinant of aggregation and toxicity. Expanding on these observations, we demonstrate that a genetic pathway regulating longevity can alter the time course of aging-related polyglutamine-mediated phenotypes. To identify novel targets and better understand how cells sense and respond to the appearance of misfolded and aggregation-prone proteins, we use a genome-wide RNA interference-based genetic screen to identify modifiers of age-dependent polyglutamine aggregation. Throughout these studies, we used fluorescence-based, live-cell biological and biophysical methods to study the behavior of these proteins in a complex multicellular environment.

Research paper thumbnail of Disease-Modifying Pathways in Neurodegeneration

The Journal of Neuroscience, 2006

Research paper thumbnail of Regulation of the Cellular Heat Shock Response in Caenorhabditis elegans by Thermosensory Neurons

Science, 2008

Temperature pervasively affects all cellular processes. In response to a rapid increase in temper... more Temperature pervasively affects all cellular processes. In response to a rapid increase in temperature, all cells undergo a heat shock response, an ancient and highly conserved program of stress-inducible gene expression, to reestablish cellular homeostasis. In isolated cells, the heat shock response is initiated by the presence of misfolded proteins and therefore thought to be cell-autonomous. In contrast, we show that within the metazoan Caenorhabditis elegans , the heat shock response of somatic cells is not cell-autonomous but rather depends on the thermosensory neuron, AFD, which senses ambient temperature and regulates temperature-dependent behavior. We propose a model whereby this loss of cell autonomy serves to integrate behavioral, metabolic, and stress-related responses to establish an organismal response to environmental change.

Research paper thumbnail of Selective activation of human heat shock gene transcription by nitrosourea antitumor drugs mediated by isocyanate-induced damage and activation of heat shock transcription factor

Proceedings of the National Academy of Sciences, 1991

Treatment of cultured human tumor cells with the chloroethylnitrosourea antitumor drug 1,3-bis(2-... more Treatment of cultured human tumor cells with the chloroethylnitrosourea antitumor drug 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU) selectively induces transcription and protein synthesis of a subset of the human heat shock or stress-induced genes (HSP90 and HSP70) with little effect on other stress genes or on expression of the c-fos, c-myc, or beta-actin genes. The active component of BCNU and related compounds appears to be the isocyanate moiety that causes carbamoylation of proteins and nucleic acids. Transcriptional activation of the human HSP70 gene by BCNU is dependent on the heat shock element and correlates with the level of heat shock transcription factor and its binding to the heat shock element in vivo. Unlike activation by heat or heavy metals, BCNU-mediated activation is strongly dependent upon new protein synthesis. This suggests that BCNU-induced, isocyanate-mediated damage to newly synthesized protein(s) may be responsible for activation of the heat shock transcripti...

Research paper thumbnail of Polyglutamine aggregates alter protein folding homeostasis in Caenorhabditis elegans

Proceedings of the National Academy of Sciences, 2000

Expansion of polyglutamine repeats in several unrelated proteins causes neurodegenerative disease... more Expansion of polyglutamine repeats in several unrelated proteins causes neurodegenerative diseases with distinct but related pathologies. To provide a model system for investigating common pathogenic features, we have examined the behavior of polyglutamine expansions expressed in Caenorhabditis elegans . The expression of polyglutamine repeats as green fluorescent protein (GFP)-fusion proteins in body wall muscle cells causes discrete cytoplasmic aggregates that appear early in embryogenesis and correlates with a delay in larval to adult development. The heat shock response is activated idiosyncratically in individual cells in a polyglutamine length-dependent fashion. The toxic effect of polyglutamine expression and the formation of aggregates can be reversed by coexpression of the yeast chaperone Hsp104. The altered homeostasis associated with polyglutamine aggregates causes both the sequestration of an otherwise soluble protein with shorter arrays of glutamine repeats and the relo...

Research paper thumbnail of The threshold for polyglutamine-expansion protein aggregation and cellular toxicity is dynamic and influenced by aging in Caenorhabditis elegans

Proceedings of the National Academy of Sciences, 2002

Studies of the mutant gene in Huntington's disease, and for eight related neurodegenerative d... more Studies of the mutant gene in Huntington's disease, and for eight related neurodegenerative disorders, have identified polyglutamine (polyQ) expansions as a basis for cellular toxicity. This finding has led to a disease hypothesis that protein aggregation and cellular dysfunction can occur at a threshold of approximately 40 glutamine residues. Here, we test this hypothesis by expression of fluorescently tagged polyQ proteins (Q29, Q33, Q35, Q40, and Q44) in the body wall muscle cells of Caenorhabditis elegans and show that young adults exhibit a sharp boundary at 35–40 glutamines associated with the appearance of protein aggregates and loss of motility. Surprisingly, genetically identical animals expressing near-threshold polyQ repeats exhibited a high degree of variation in the appearance of protein aggregates and cellular toxicity that was dependent on repeat length and exacerbated during aging. The role of genetically determined aging pathways in the progression of age-depend...

Research paper thumbnail of Spreading of a Prion Domain from Cell-to-Cell by Vesicular Transport in Caenorhabditis elegans

PLoS Genetics, 2013

Prion proteins can adopt self-propagating alternative conformations that account for the infectio... more Prion proteins can adopt self-propagating alternative conformations that account for the infectious nature of transmissible spongiform encephalopathies (TSEs) and the epigenetic inheritance of certain traits in yeast. Recent evidence suggests a similar propagation of misfolded proteins in the spreading of pathology of neurodegenerative diseases including Alzheimer's or Parkinson's disease. Currently there is only a limited number of animal model systems available to study the mechanisms that underlie the cell-to-cell transmission of aggregation-prone proteins. Here, we have established a new metazoan model in Caenorhabditis elegans expressing the prion domain NM of the cytosolic yeast prion protein Sup35, in which aggregation and toxicity are dependent upon the length of oligopeptide repeats in the glutamine/asparagine (Q/N)rich N-terminus. NM forms multiple classes of highly toxic aggregate species and co-localizes to autophagy-related vesicles that transport the prion domain from the site of expression to adjacent tissues. This is associated with a profound cell autonomous and cell non-autonomous disruption of mitochondrial integrity, embryonic and larval arrest, developmental delay, widespread tissue defects, and loss of organismal proteostasis. Our results reveal that the Sup35 prion domain exhibits prion-like properties when expressed in the multicellular organism C. elegans and adapts to different requirements for propagation that involve the autophagy-lysosome pathway to transmit cytosolic aggregation-prone proteins between tissues.

Research paper thumbnail of The life of proteins: the good, the mostly good and the ugly

Nature Structural & Molecular Biology, 2011

Research paper thumbnail of Cytosolic chaperonin prevents polyglutamine toxicity with altering the aggregation state

Nature Cell Biology, 2006

Research paper thumbnail of Activation of Heat Shock Factor 1 DNA Binding Precedes Stress-induced Serine Phosphorylation

Journal of Biological Chemistry, 1996

Exposure of mammalian cells in culture to the antiinflammatory drugs sodium salicylate or indomet... more Exposure of mammalian cells in culture to the antiinflammatory drugs sodium salicylate or indomethacin results in activation of heat shock factor 1 (HSF1) DNA binding activity. We have previously shown that the drug-induced HSF1 becomes associated with the heat shock elements of the hsp70 promoter, yet transcription of the hsp70 gene is not induced (Jurivich, D. A.,

Research paper thumbnail of Regulation of the Cellular Heat Shock Response in <i>Caenorhabditis elegans</i> by Thermosensory Neurons

Research paper thumbnail of Polyglutamine aggregates alter protein folding homeostasis in <i>Caenorhabditis elegans</i>

Proceedings of the National Academy of Sciences of the United States of America, May 16, 2000

Expansion of polyglutamine repeats in several unrelated proteins causes neurodegenerative disease... more Expansion of polyglutamine repeats in several unrelated proteins causes neurodegenerative diseases with distinct but related pathologies. To provide a model system for investigating common pathogenic features, we have examined the behavior of polyglutamine expansions expressed in Caenorhabditis elegans. The expression of polyglutamine repeats as green fluorescent protein (GFP)-fusion proteins in body wall muscle cells causes discrete cytoplasmic aggregates that appear early in embryogenesis and correlates with a delay in larval to adult development. The heat shock response is activated idiosyncratically in individual cells in a polyglutamine length-dependent fashion. The toxic effect of polyglutamine expression and the formation of aggregates can be reversed by coexpression of the yeast chaperone Hsp104. The altered homeostasis associated with polyglutamine aggregates causes both the sequestration of an otherwise soluble protein with shorter arrays of glutamine repeats and the relocalization of a nuclear glutamine-rich protein. These observations of induced aggregation and relocalization have implications for disorders involving protein aggregation.

Research paper thumbnail of Dynamic Imaging by Fluorescence Correlation Spectroscopy Identifies Diverse Populations of Polyglutamine Oligomers Formed in Vivo

Journal of Biological Chemistry, Jul 1, 2012

Background: Protein aggregation is implicated in numerous diseases. Results: Polyglutamine oligom... more Background: Protein aggregation is implicated in numerous diseases. Results: Polyglutamine oligomers maintain a heterogeneous distribution that reaches an equilibrium during aging and can be altered by genetic modifiers that suppress aggregation. Conclusion: Shifts in populations of oligomers do not correlate with toxicity. Significance: The dynamics of oligomerization and aggregation to inert species is essential for protein misfolding and toxicity. Protein misfolding and aggregation are exacerbated by aging and diseases of protein conformation including neurodegeneration, metabolic diseases, and cancer. In the cellular environment, aggregates can exist as discrete entities, or heterogeneous complexes of diverse solubility and conformational state. In this study, we have examined the in vivo dynamics of aggregation using imaging methods including fluorescence microscopy, fluorescence recovery after photobleaching (FRAP), and fluorescence correlation spectroscopy (FCS), to monitor the diverse biophysical states of expanded polyglutamine (polyQ) proteins expressed in Caenorhabditis elegans. We show that monomers, oligomers and aggregates co-exist at different concentrations in young and aged animals expressing different polyQ-lengths. During aging, when aggregation and toxicity are exacerbated, FCS-based burst analysis and purified single molecule FCS detected a populational shift toward an increase in the frequency of brighter and larger oligomeric species. Regardless of age or polyQ-length, oligomers were maintained in a heterogeneous distribution that spans multiple orders of magnitude in brightness. We employed genetic suppressors that prevent polyQ aggregation and observed a reduction in visible immobile species with the persistence of heterogeneous oligomers, yet our analysis did not detect the appearance of any discrete oligomeric states associated with toxicity. These studies reveal that the reversible transition from monomers to immobile aggregates is not represented by discrete oligomeric states, but rather suggests that the process of aggregation involves a more complex pattern of molecular interactions of diverse intermediate species that can appear in vivo and contribute to aggregate formation and toxicity.

Research paper thumbnail of Cytosolic chaperonin prevents polyglutamine toxicity with altering the aggregation state

Nature Cell Biology, Sep 17, 2006

Research paper thumbnail of Disease-Modifying Pathways in Neurodegeneration

The Journal of Neuroscience, Oct 11, 2006

Research paper thumbnail of Protein homeostasis of a metastable subproteome associated with Alzheimer’s disease

Proceedings of the National Academy of Sciences of the United States of America, Jun 26, 2017

Research paper thumbnail of Selective activation of human heat shock gene transcription by nitrosourea antitumor drugs mediated by isocyanate-induced damage and activation of heat shock transcription factor

Proceedings of the National Academy of Sciences of the United States of America, Jun 1, 1991

Treatment of cultured human tumor cells with the chloroethylnitrosourea antitumor drug 1,3-bis(2-... more Treatment of cultured human tumor cells with the chloroethylnitrosourea antitumor drug 1,3-bis(2- chloroethyl)-l-nitrosourea (BCNU) selectively induces tran- scription and protein synthesis of a subset of the human heat shock or stress-induced genes (HSP90 and HSP70) with little effect on other stress genes or on expression of the c-fos, c-myc, or .8-actin genes. The active component of BCNU and related compounds appears to be the isocyanate moiety that causes carbamoylation of proteins and nucleic acids. Transcriptional activation of the human HSP70 gene by BCNU is dependent on the heat shock element and correlates with the level of heat shock transcription factor and its binding to the heat shock element in vivo. Unlike activation by heat or heavy metals, BCNU-mediated activation is strongly dependent upon new protein synthesis. This suggests that BCNU-induced, isocyanate-mediated damage to newly synthesized protein(s) may be responsible for activation of the heat shock transcription factor and increased transcription of the HSP90 and HSP70 genes.

Research paper thumbnail of HSF1 transcription factor concentrates in nuclear foci during heat shock: relationship with transcription sites

Journal of Cell Science, 1997

In this paper, we show that upon heat shock, HSF1 concentrates in the nucleus of diploid human fi... more In this paper, we show that upon heat shock, HSF1 concentrates in the nucleus of diploid human fibroblasts in two large foci. The relative distribution of HSF1 nuclear foci and active heat shock protein (hsp) genes was investigated by combining fluorescence in situ hybridization (FISH) for the detection of hsp nuclear transcripts and immunofluorescence for the detection of HSF1. We show that the HSF1 foci are distinct from the sites of hsp70 and hsp90 genes transcription. This is the second report of ploidy-dependent foci of transcription factors that are independent of their specific transcription sites. However, the correlation between the number of HSF1 foci and the ploidy of the cells strongly supports the existence of a specific chromosomal target for HSF1 foci.

Research paper thumbnail of Proteotoxic stress and ageing triggers the loss of redox homeostasis across cellular compartments

The EMBO journal, Jan 14, 2015

The cellular proteostasis network integrates the protein folding and clearance machineries in mul... more The cellular proteostasis network integrates the protein folding and clearance machineries in multiple sub-cellular compartments of the eukaryotic cell. The endoplasmic reticulum (ER) is the site of synthesis and folding of membrane and secretory proteins. A distinctive feature of the ER is its tightly controlled redox homeostasis necessary for the formation of inter- and intra-molecular disulphide bonds. Employing genetically encoded in vivo sensors reporting on the redox state in an organelle-specific manner, we show in the nematode Caenorhabditis elegans that the redox state of the ER is subject to profound changes during worm lifetime. In young animals, the ER is oxidizing and this shifts towards reducing conditions during ageing, whereas in the cytosol the redox state becomes more oxidizing with age. Likewise, the redox state in the cytosol and the ER change in an opposing manner in response to proteotoxic challenges in C. elegans and in HeLa cells revealing conservation of red...

Research paper thumbnail of Serotonergic signalling suppresses ataxin 3 aggregation and neurotoxicity in animal models of Machado-Joseph disease

Brain : a journal of neurology, Jan 15, 2015

Polyglutamine diseases are a class of dominantly inherited neurodegenerative disorders for which ... more Polyglutamine diseases are a class of dominantly inherited neurodegenerative disorders for which there is no effective treatment. Here we provide evidence that activation of serotonergic signalling is beneficial in animal models of Machado-Joseph disease. We identified citalopram, a selective serotonin reuptake inhibitor, in a small molecule screen of FDA-approved drugs that rescued neuronal dysfunction and reduced aggregation using a Caenorhabditis elegans model of mutant ataxin 3-induced neurotoxicity. MOD-5, the C. elegans orthologue of the serotonin transporter and cellular target of citalopram, and the serotonin receptors SER-1 and SER-4 were strong genetic modifiers of ataxin 3 neurotoxicity and necessary for therapeutic efficacy. Moreover, chronic treatment of CMVMJD135 mice with citalopram significantly reduced ataxin 3 neuronal inclusions and astrogliosis, rescued diminished body weight and strikingly ameliorated motor symptoms. These results suggest that small molecule mod...

Research paper thumbnail of Modeling Polyglutamine Pathogenesis in C. elegans

Methods in Enzymology, 2006

A growing number of human neurodegenerative diseases are associated with disruption of cellular p... more A growing number of human neurodegenerative diseases are associated with disruption of cellular protein folding homeostasis, leading to the appearance of misfolded proteins and deposition of protein aggregates and inclusions. Recent years have been witness to widespread development of invertebrate systems (specifically Drosophila and Caenorhabditis elegans) to model these disorders, bringing the many advantages of such systems, particularly the power of genetic analysis in a metazoan, to bear on these problems. In this chapter, we describe our studies using the nematode, C. elegans, as a model to study polyglutamine expansions as occur in Huntington's disease and related ataxias. Using fluorescently tagged polyglutamine repeats of different lengths, we have examined the dynamics of aggregate formation both within individual cells and over time throughout the lifetime of individual organisms, identifying aging as an important physiological determinant of aggregation and toxicity. Expanding on these observations, we demonstrate that a genetic pathway regulating longevity can alter the time course of aging-related polyglutamine-mediated phenotypes. To identify novel targets and better understand how cells sense and respond to the appearance of misfolded and aggregation-prone proteins, we use a genome-wide RNA interference-based genetic screen to identify modifiers of age-dependent polyglutamine aggregation. Throughout these studies, we used fluorescence-based, live-cell biological and biophysical methods to study the behavior of these proteins in a complex multicellular environment.

Research paper thumbnail of Disease-Modifying Pathways in Neurodegeneration

The Journal of Neuroscience, 2006

Research paper thumbnail of Regulation of the Cellular Heat Shock Response in Caenorhabditis elegans by Thermosensory Neurons

Science, 2008

Temperature pervasively affects all cellular processes. In response to a rapid increase in temper... more Temperature pervasively affects all cellular processes. In response to a rapid increase in temperature, all cells undergo a heat shock response, an ancient and highly conserved program of stress-inducible gene expression, to reestablish cellular homeostasis. In isolated cells, the heat shock response is initiated by the presence of misfolded proteins and therefore thought to be cell-autonomous. In contrast, we show that within the metazoan Caenorhabditis elegans , the heat shock response of somatic cells is not cell-autonomous but rather depends on the thermosensory neuron, AFD, which senses ambient temperature and regulates temperature-dependent behavior. We propose a model whereby this loss of cell autonomy serves to integrate behavioral, metabolic, and stress-related responses to establish an organismal response to environmental change.

Research paper thumbnail of Selective activation of human heat shock gene transcription by nitrosourea antitumor drugs mediated by isocyanate-induced damage and activation of heat shock transcription factor

Proceedings of the National Academy of Sciences, 1991

Treatment of cultured human tumor cells with the chloroethylnitrosourea antitumor drug 1,3-bis(2-... more Treatment of cultured human tumor cells with the chloroethylnitrosourea antitumor drug 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU) selectively induces transcription and protein synthesis of a subset of the human heat shock or stress-induced genes (HSP90 and HSP70) with little effect on other stress genes or on expression of the c-fos, c-myc, or beta-actin genes. The active component of BCNU and related compounds appears to be the isocyanate moiety that causes carbamoylation of proteins and nucleic acids. Transcriptional activation of the human HSP70 gene by BCNU is dependent on the heat shock element and correlates with the level of heat shock transcription factor and its binding to the heat shock element in vivo. Unlike activation by heat or heavy metals, BCNU-mediated activation is strongly dependent upon new protein synthesis. This suggests that BCNU-induced, isocyanate-mediated damage to newly synthesized protein(s) may be responsible for activation of the heat shock transcripti...

Research paper thumbnail of Polyglutamine aggregates alter protein folding homeostasis in Caenorhabditis elegans

Proceedings of the National Academy of Sciences, 2000

Expansion of polyglutamine repeats in several unrelated proteins causes neurodegenerative disease... more Expansion of polyglutamine repeats in several unrelated proteins causes neurodegenerative diseases with distinct but related pathologies. To provide a model system for investigating common pathogenic features, we have examined the behavior of polyglutamine expansions expressed in Caenorhabditis elegans . The expression of polyglutamine repeats as green fluorescent protein (GFP)-fusion proteins in body wall muscle cells causes discrete cytoplasmic aggregates that appear early in embryogenesis and correlates with a delay in larval to adult development. The heat shock response is activated idiosyncratically in individual cells in a polyglutamine length-dependent fashion. The toxic effect of polyglutamine expression and the formation of aggregates can be reversed by coexpression of the yeast chaperone Hsp104. The altered homeostasis associated with polyglutamine aggregates causes both the sequestration of an otherwise soluble protein with shorter arrays of glutamine repeats and the relo...

Research paper thumbnail of The threshold for polyglutamine-expansion protein aggregation and cellular toxicity is dynamic and influenced by aging in Caenorhabditis elegans

Proceedings of the National Academy of Sciences, 2002

Studies of the mutant gene in Huntington's disease, and for eight related neurodegenerative d... more Studies of the mutant gene in Huntington's disease, and for eight related neurodegenerative disorders, have identified polyglutamine (polyQ) expansions as a basis for cellular toxicity. This finding has led to a disease hypothesis that protein aggregation and cellular dysfunction can occur at a threshold of approximately 40 glutamine residues. Here, we test this hypothesis by expression of fluorescently tagged polyQ proteins (Q29, Q33, Q35, Q40, and Q44) in the body wall muscle cells of Caenorhabditis elegans and show that young adults exhibit a sharp boundary at 35–40 glutamines associated with the appearance of protein aggregates and loss of motility. Surprisingly, genetically identical animals expressing near-threshold polyQ repeats exhibited a high degree of variation in the appearance of protein aggregates and cellular toxicity that was dependent on repeat length and exacerbated during aging. The role of genetically determined aging pathways in the progression of age-depend...

Research paper thumbnail of Spreading of a Prion Domain from Cell-to-Cell by Vesicular Transport in Caenorhabditis elegans

PLoS Genetics, 2013

Prion proteins can adopt self-propagating alternative conformations that account for the infectio... more Prion proteins can adopt self-propagating alternative conformations that account for the infectious nature of transmissible spongiform encephalopathies (TSEs) and the epigenetic inheritance of certain traits in yeast. Recent evidence suggests a similar propagation of misfolded proteins in the spreading of pathology of neurodegenerative diseases including Alzheimer's or Parkinson's disease. Currently there is only a limited number of animal model systems available to study the mechanisms that underlie the cell-to-cell transmission of aggregation-prone proteins. Here, we have established a new metazoan model in Caenorhabditis elegans expressing the prion domain NM of the cytosolic yeast prion protein Sup35, in which aggregation and toxicity are dependent upon the length of oligopeptide repeats in the glutamine/asparagine (Q/N)rich N-terminus. NM forms multiple classes of highly toxic aggregate species and co-localizes to autophagy-related vesicles that transport the prion domain from the site of expression to adjacent tissues. This is associated with a profound cell autonomous and cell non-autonomous disruption of mitochondrial integrity, embryonic and larval arrest, developmental delay, widespread tissue defects, and loss of organismal proteostasis. Our results reveal that the Sup35 prion domain exhibits prion-like properties when expressed in the multicellular organism C. elegans and adapts to different requirements for propagation that involve the autophagy-lysosome pathway to transmit cytosolic aggregation-prone proteins between tissues.

Research paper thumbnail of The life of proteins: the good, the mostly good and the ugly

Nature Structural & Molecular Biology, 2011

Research paper thumbnail of Cytosolic chaperonin prevents polyglutamine toxicity with altering the aggregation state

Nature Cell Biology, 2006

Research paper thumbnail of Activation of Heat Shock Factor 1 DNA Binding Precedes Stress-induced Serine Phosphorylation

Journal of Biological Chemistry, 1996

Exposure of mammalian cells in culture to the antiinflammatory drugs sodium salicylate or indomet... more Exposure of mammalian cells in culture to the antiinflammatory drugs sodium salicylate or indomethacin results in activation of heat shock factor 1 (HSF1) DNA binding activity. We have previously shown that the drug-induced HSF1 becomes associated with the heat shock elements of the hsp70 promoter, yet transcription of the hsp70 gene is not induced (Jurivich, D. A.,