Jessie Turnbaugh | Washington University in St. Louis (original) (raw)

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Research paper thumbnail of A nine amino acid domain Is essential for mutant prion protein toxicity

Transgenic mice expressing PrP molecules with several different internal deletions display sponta... more Transgenic mice expressing PrP molecules with several different internal deletions display spontaneous neurodegenerative phenotypes that can be dose-dependently suppressed by coexpression of wild-type PrP. Each of these deletions, including the largest one (Δ32-134), retains nine amino acids immediately following the signal peptide cleavage site (residues 23-31; KKRPKPGGW). These residues have been implicated in several biological functions of PrP, including endocytic trafficking and binding of glycosaminoglycans. We report here on our experiments to test the role of this domain in the toxicity of deleted forms of PrP. We find that transgenic mice expressing Δ23-134 PrP display no clinical symptoms or neuropathology, in contrast to mice expressing Δ32-134 PrP, suggesting that residues 23-31 are essential for the toxic phenotype. Using a newly developed cell culture assay, we narrow the essential region to amino acids 23-26, and we show that mutant PrP toxicity is not related to the role of the Nterminal residues in endocytosis or binding to endogenous glycosaminoglycans. However, we find that mutant PrP toxicity is potently inhibited by application of exogenous glycosaminoglycans, suggesting that the latter molecules block an essential interaction between the N-terminus of PrP and a membrane-associated target site. Our results demonstrate that a short segment containing positively charged amino acids at the N-terminus of PrP plays an essential role in mediating PrPrelated neurotoxicity. This finding identifies a protein domain that may serve as a drug target for amelioration of prion neurotoxicity.

Research paper thumbnail of The Toxic Effect of a Mutant Prion Protein is Cell-autonomous, but can be Suppressed in trans by Wild-type Prion Protein

Research paper thumbnail of Prion protein at the crossroads of physiology and disease

Trends in Neurosciences, 2012

The presence of the cellular prion protein (PrP C ) on the cell surface is critical for the neuro... more The presence of the cellular prion protein (PrP C ) on the cell surface is critical for the neurotoxicity of prions. Although a number of biological activities have been attributed to PrP C , a definitive demonstration of its physiological function remains elusive. In this review, we will discuss some of the proposed functions of PrP C , focusing on recently suggested roles in cell adhesion, regulation of ionic currents at the cell membrane, and neuroprotection. We will also discuss recent evidence supporting the idea that PrP C may function as a receptor for soluble oligomers of the amyloid β peptide and possibly other toxic protein aggregates. These data suggest surprising new connections between the physiological function of PrP C and its role in neurodegenerative diseases beyond those caused by prions.

Research paper thumbnail of The N-Terminal, Polybasic Region of PrPC Dictates the Efficiency of Prion Propagation by Binding to PrPSc

Journal of Neuroscience, 2012

Prion propagation involves a templating reaction in which the infectious form of the prion protei... more Prion propagation involves a templating reaction in which the infectious form of the prion protein (PrP Sc ) binds to the cellular form (PrP C ), generating additional molecules of PrP Sc . While several regions of the PrP C molecule have been suggested to play a role in PrP Sc formation based on in vitro studies, the contribution of these regions in vivo is unclear. Here, we report that mice expressing PrP deleted for a short, polybasic region at the N terminus (residues 23-31) display a dramatically reduced susceptibility to prion infection and accumulate greatly reduced levels of PrP Sc . These results, in combination with biochemical data, demonstrate that residues 23-31 represent a critical site on PrP C that binds to PrP Sc and is essential for efficient prion propagation. It may be possible to specifically target this region for treatment of prion diseases as well as other neurodegenerative disorders due to β-sheet-rich oligomers that bind to PrP C .

Research paper thumbnail of The N-Terminal, Polybasic Region Is Critical for Prion Protein Neuroprotective Activity

PLoS ONE, 2011

Several lines of evidence suggest that the normal form of the prion protein, PrP C , exerts a neu... more Several lines of evidence suggest that the normal form of the prion protein, PrP C , exerts a neuroprotective activity against cellular stress or toxicity. One of the clearest examples of such activity is the ability of wild-type PrP C to suppress the spontaneous neurodegenerative phenotype of transgenic mice expressing a deleted form of PrP (D32-134, called F35). To define domains of PrP involved in its neuroprotective activity, we have analyzed the ability of several deletion mutants of PrP (D23-31, D23-111, and D23-134) to rescue the phenotype of Tg(F35) mice. Surprisingly, all of these mutants displayed greatly diminished rescue activity, although D23-31 PrP partially suppressed neuronal loss when expressed at very high levels. Our results pinpoint the N-terminal, polybasic domain as a critical determinant of PrP C neuroprotective activity, and suggest that identification of molecules interacting with this region will provide important clues regarding the normal function of the protein. Small molecule ligands targeting this region may also represent useful therapeutic agents for treatment of prion diseases.

Research paper thumbnail of A Naturally Occurring C-terminal Fragment of the Prion Protein (PrP) Delays Disease and Acts as a Dominant-negative Inhibitor of PrPSc Formation

Journal of Biological Chemistry, 2011

Background: C1 is the main physiological cleavage fragment of PrP, but its role in disease is unk... more Background: C1 is the main physiological cleavage fragment of PrP, but its role in disease is unknown. Results: C1 is not toxic when expressed in mice and delays the onset of disease and PrP Sc formation when co-expressed with WT PrP. Conclusion: C1 is a dominant-negative inhibitor of PrP Sc formation. Significance: Modulation of C1 cleavage may represent a therapeutic strategy for combating PrP Sc infection.

Research paper thumbnail of The toxicity of a mutant prion protein is cell-autonomous, and can be suppressed by wild-type prion protein on adjacent cells

PloS one, 2012

Insight into the normal function of PrP(C), and how it can be subverted to produce neurotoxic eff... more Insight into the normal function of PrP(C), and how it can be subverted to produce neurotoxic effects, is provided by PrP molecules carrying deletions encompassing the conserved central region. The most neurotoxic of these mutants, Δ105-125 (called ΔCR), produces a spontaneous neurodegenerative illness when expressed in transgenic mice, and this phenotype can be dose-dependently suppressed by co-expression of wild-type PrP. Whether the toxic activity of ΔCR PrP and the protective activity or wild-type PrP are cell-autonomous, or can be exerted on neighboring cells, is unknown. To investigate this question, we have utilized co-cultures of differentiated neural stem cells derived from mice expressing ΔCR or wild-type PrP. Cells from the two kinds of mice, which are marked by the presence or absence of GFP, are differentiated together to yield neurons, astrocytes, and oligodendrocytes. As a surrogate read-out of ΔCR PrP toxicity, we assayed sensitivity of the cells to the cationic anti...

Research paper thumbnail of A nine amino acid domain Is essential for mutant prion protein toxicity

Transgenic mice expressing PrP molecules with several different internal deletions display sponta... more Transgenic mice expressing PrP molecules with several different internal deletions display spontaneous neurodegenerative phenotypes that can be dose-dependently suppressed by coexpression of wild-type PrP. Each of these deletions, including the largest one (Δ32-134), retains nine amino acids immediately following the signal peptide cleavage site (residues 23-31; KKRPKPGGW). These residues have been implicated in several biological functions of PrP, including endocytic trafficking and binding of glycosaminoglycans. We report here on our experiments to test the role of this domain in the toxicity of deleted forms of PrP. We find that transgenic mice expressing Δ23-134 PrP display no clinical symptoms or neuropathology, in contrast to mice expressing Δ32-134 PrP, suggesting that residues 23-31 are essential for the toxic phenotype. Using a newly developed cell culture assay, we narrow the essential region to amino acids 23-26, and we show that mutant PrP toxicity is not related to the role of the Nterminal residues in endocytosis or binding to endogenous glycosaminoglycans. However, we find that mutant PrP toxicity is potently inhibited by application of exogenous glycosaminoglycans, suggesting that the latter molecules block an essential interaction between the N-terminus of PrP and a membrane-associated target site. Our results demonstrate that a short segment containing positively charged amino acids at the N-terminus of PrP plays an essential role in mediating PrPrelated neurotoxicity. This finding identifies a protein domain that may serve as a drug target for amelioration of prion neurotoxicity.

Research paper thumbnail of The Toxic Effect of a Mutant Prion Protein is Cell-autonomous, but can be Suppressed in trans by Wild-type Prion Protein

Research paper thumbnail of Prion protein at the crossroads of physiology and disease

Trends in Neurosciences, 2012

The presence of the cellular prion protein (PrP C ) on the cell surface is critical for the neuro... more The presence of the cellular prion protein (PrP C ) on the cell surface is critical for the neurotoxicity of prions. Although a number of biological activities have been attributed to PrP C , a definitive demonstration of its physiological function remains elusive. In this review, we will discuss some of the proposed functions of PrP C , focusing on recently suggested roles in cell adhesion, regulation of ionic currents at the cell membrane, and neuroprotection. We will also discuss recent evidence supporting the idea that PrP C may function as a receptor for soluble oligomers of the amyloid β peptide and possibly other toxic protein aggregates. These data suggest surprising new connections between the physiological function of PrP C and its role in neurodegenerative diseases beyond those caused by prions.

Research paper thumbnail of The N-Terminal, Polybasic Region of PrPC Dictates the Efficiency of Prion Propagation by Binding to PrPSc

Journal of Neuroscience, 2012

Prion propagation involves a templating reaction in which the infectious form of the prion protei... more Prion propagation involves a templating reaction in which the infectious form of the prion protein (PrP Sc ) binds to the cellular form (PrP C ), generating additional molecules of PrP Sc . While several regions of the PrP C molecule have been suggested to play a role in PrP Sc formation based on in vitro studies, the contribution of these regions in vivo is unclear. Here, we report that mice expressing PrP deleted for a short, polybasic region at the N terminus (residues 23-31) display a dramatically reduced susceptibility to prion infection and accumulate greatly reduced levels of PrP Sc . These results, in combination with biochemical data, demonstrate that residues 23-31 represent a critical site on PrP C that binds to PrP Sc and is essential for efficient prion propagation. It may be possible to specifically target this region for treatment of prion diseases as well as other neurodegenerative disorders due to β-sheet-rich oligomers that bind to PrP C .

Research paper thumbnail of The N-Terminal, Polybasic Region Is Critical for Prion Protein Neuroprotective Activity

PLoS ONE, 2011

Several lines of evidence suggest that the normal form of the prion protein, PrP C , exerts a neu... more Several lines of evidence suggest that the normal form of the prion protein, PrP C , exerts a neuroprotective activity against cellular stress or toxicity. One of the clearest examples of such activity is the ability of wild-type PrP C to suppress the spontaneous neurodegenerative phenotype of transgenic mice expressing a deleted form of PrP (D32-134, called F35). To define domains of PrP involved in its neuroprotective activity, we have analyzed the ability of several deletion mutants of PrP (D23-31, D23-111, and D23-134) to rescue the phenotype of Tg(F35) mice. Surprisingly, all of these mutants displayed greatly diminished rescue activity, although D23-31 PrP partially suppressed neuronal loss when expressed at very high levels. Our results pinpoint the N-terminal, polybasic domain as a critical determinant of PrP C neuroprotective activity, and suggest that identification of molecules interacting with this region will provide important clues regarding the normal function of the protein. Small molecule ligands targeting this region may also represent useful therapeutic agents for treatment of prion diseases.

Research paper thumbnail of A Naturally Occurring C-terminal Fragment of the Prion Protein (PrP) Delays Disease and Acts as a Dominant-negative Inhibitor of PrPSc Formation

Journal of Biological Chemistry, 2011

Background: C1 is the main physiological cleavage fragment of PrP, but its role in disease is unk... more Background: C1 is the main physiological cleavage fragment of PrP, but its role in disease is unknown. Results: C1 is not toxic when expressed in mice and delays the onset of disease and PrP Sc formation when co-expressed with WT PrP. Conclusion: C1 is a dominant-negative inhibitor of PrP Sc formation. Significance: Modulation of C1 cleavage may represent a therapeutic strategy for combating PrP Sc infection.

Research paper thumbnail of The toxicity of a mutant prion protein is cell-autonomous, and can be suppressed by wild-type prion protein on adjacent cells

PloS one, 2012

Insight into the normal function of PrP(C), and how it can be subverted to produce neurotoxic eff... more Insight into the normal function of PrP(C), and how it can be subverted to produce neurotoxic effects, is provided by PrP molecules carrying deletions encompassing the conserved central region. The most neurotoxic of these mutants, Δ105-125 (called ΔCR), produces a spontaneous neurodegenerative illness when expressed in transgenic mice, and this phenotype can be dose-dependently suppressed by co-expression of wild-type PrP. Whether the toxic activity of ΔCR PrP and the protective activity or wild-type PrP are cell-autonomous, or can be exerted on neighboring cells, is unknown. To investigate this question, we have utilized co-cultures of differentiated neural stem cells derived from mice expressing ΔCR or wild-type PrP. Cells from the two kinds of mice, which are marked by the presence or absence of GFP, are differentiated together to yield neurons, astrocytes, and oligodendrocytes. As a surrogate read-out of ΔCR PrP toxicity, we assayed sensitivity of the cells to the cationic anti...