Showing papers by "Susan Lindquist published in 2006"

α-Synuclein Blocks ER-Golgi Traffic and Rab1 Rescues Neuron Loss in Parkinson's Models

Abstract: Alpha-synuclein (αSyn) misfolding is associated with several devastating neurodegenerative disorders, including Parkinson9s disease (PD). In yeast cells and in neurons αSyn accumulation is cytotoxic, but little is known about its normal function or pathobiology. The earliest defect following αSyn expression in yeast was a block in endoplasmic reticulum (ER)–to–Golgi vesicular trafficking. In a genomewide screen, the largest class of toxicity modifiers were proteins functioning at this same step, including the Rab guanosine triphosphatase Ypt1p, which associated with cytoplasmic αSyn inclusions. Elevated expression of Rab1, the mammalian YPT1 homolog, protected against αSyn-induced dopaminergic neuron loss in animal models of PD. Thus, synucleinopathies may result from disruptions in basic cellular functions that interface with the unique biology of particular neurons to make them especially vulnerable.

Green tea (−)-epigallocatechin-gallate modulates early events in huntingtin misfolding and reduces toxicity in Huntington's disease models

Abstract: Huntington's disease (HD) is a progressive neurodegenerative disorder for which only symptomatic treatments of limited effectiveness are available. Preventing early misfolding steps and thereby aggregation of the polyglutamine (polyQ)-containing protein huntingtin (htt) in neurons of patients may represent an attractive therapeutic strategy to postpone the onset and progression of HD. Here, we demonstrate that the green tea polyphenol (-)-epigallocatechin-3-gallate (EGCG) potently inhibits the aggregation of mutant htt exon 1 protein in a dose-dependent manner. Dot-blot assays and atomic force microscopy studies revealed that EGCG modulates misfolding and oligomerization of mutant htt exon 1 protein in vitro, indicating that it interferes with very early events in the aggregation process. Also, EGCG significantly reduced polyQ-mediated htt protein aggregation and cytotoxicity in an yeast model of HD. When EGCG was fed to transgenic HD flies overexpressing a pathogenic htt exon 1 protein, photoreceptor degeneration and motor function improved. These results indicate that modulators of htt exon 1 misfolding and oligomerization like EGCG are likely to reduce polyQ-mediated toxicity in vivo. Our studies may provide the basis for the development of a novel pharmacotherapy for HD and related polyQ disorders.

Flanking sequences profoundly alter polyglutamine toxicity in yeast

Abstract: Protein misfolding is the molecular basis for several human diseases. How the primary amino acid sequence triggers misfolding and determines the benign or toxic character of the misfolded protein remains largely obscure. Among proteins that misfold, polyglutamine (polyQ) expansion proteins provide an interesting case: Each causes a distinct neurodegenerative disease that selectively affects different neurons. However, all are broadly expressed and most become toxic when the glutamine expansion exceeds ≈39 glutamine residues. The disease-causing polyQ expansion proteins differ profoundly in the amino acids flanking the polyQ region. We therefore hypothesized that these flanking sequences influence the specific toxic character of each polyQ expansion protein. Using a yeast model, we find that sequences flanking the polyQ region of human huntingtin exon I can convert a benign protein to a toxic species and vice versa. Further, we observe that flanking sequences can direct polyQ misfolding to at least two morphologically distinct types of polyQ aggregates. Very tight aggregates always are benign, whereas amorphous aggregates can be toxic. We thereby establish a previously undescribed systematic characterization of the influence of flanking amino acid sequences on polyQ toxicity.

Prion protein (PrPc) positively regulates neural precursor proliferation during developmental and adult mammalian neurogenesis

Abstract: The misfolding of the prion protein (PrPc) is a central event in prion diseases, yet the normal function of PrPc remains unknown. PrPc has putative roles in many cellular processes including signaling, survival, adhesion, and differentiation. Given the abundance of PrPc in the developing and mature mammalian CNS, we investigated the role of PrPc in neural development and in adult neurogenesis, which occurs constitutively in the dentate gyrus (DG) of the hippocampus and in the olfactory bulb from precursors in the subventricular zone (SVZ)/rostral migratory stream. In vivo, we find that PrPc is expressed immediately adjacent to the proliferative region of the SVZ but not in mitotic cells. In vivo and in vitro studies further find that PrPc is expressed in multipotent neural precursors and mature neurons but is not detectable in glia. Loss- and gain-of-function experiments demonstrate that PrPc levels correlate with differentiation of multipotent neural precursors into mature neurons in vitro and that PrPc levels positively influence neuronal differentiation in a dose-dependent manner. PrPc also increases cellular proliferation in vivo; in the SVZ, PrPc overexpresser (OE) mice have more proliferating cells compared with wild-type (WT) or knockout (KO) mice; in the DG, PrPc OE and WT mice have more proliferating cells compared with KO mice. Our results demonstrate that PrPc plays an important role in neurogenesis and differentiation. Because the final number of neurons produced in the DG is unchanged by PrPc expression, other factors must control the ultimate fate of new neurons.

Prion protein is expressed on long-term repopulating hematopoietic stem cells and is important for their self-renewal.

Abstract: Although the wild-type prion protein (PrP) is abundant and widely expressed in various types of tissues and cells, its physiological function(s) remain unknown, and PrP knockout mice do not exhibit overt and undisputed phenotypes. Here we showed that PrP is expressed on the surface of several bone marrow cell populations successively enriched in long-term (LT) hematopoietic stem cells (HSCs) using flow cytometry analysis. Affinity purification of the PrP-positive and -negative fractions from these populations, followed by competitive bone marrow reconstitution assays, shows that all LT HSCs express PrP. HSCs from PrP-null bone marrow exhibited impaired self-renewal in serial transplantation of lethally irradiated mouse recipients both in the presence and absence of competitors. When treated with a cell cycle-specific myelotoxic agent, the animals reconstituted with PrP-null HSCs exhibit increased sensitivity to hematopoietic cell depletion. Ectopic expression of PrP in PrP-null bone marrow cells by retroviral infection rescued the defective hematopoietic engraftment during serial transplantation. Therefore, PrP is a marker for HSCs and supports their self-renewal.

A network of protein interactions determines polyglutamine toxicity.

Abstract: Several neurodegenerative diseases are associated with the toxicity of misfolded proteins. This toxicity must arise from a combination of the amino acid sequences of the misfolded proteins and their interactions with other factors in their environment. A particularly compelling example of how profoundly these intramolecular and intermolecular factors can modulate the toxicity of a misfolded protein is provided by the polyglutamine (polyQ) diseases. All of these disorders are caused by glutamine expansions in proteins that are broadly expressed, yet the nature of the proteins that harbor the glutamine expansions and the particular pathologies they produce are very different. We find, using a yeast model, that amino acid sequences that modulate polyQ toxicity in cis can also do so in trans. Furthermore, the prion conformation of the yeast protein Rnq1 and the level of expression of a suite of other glutamine-rich proteins profoundly affect polyQ toxicity. They can convert polyQ expansion proteins from toxic to benign and vice versa. Our work presents a paradigm for how a complex, dynamic interplay between intramolecular features of polyQ proteins and intermolecular factors in the cellular environment might determine the unique pathobiologies of polyQ expansion proteins.

Genetic Architecture of Hsp90-Dependent Drug Resistance

Abstract: Hsp90 potentiates the evolution of azole resistance in the model yeast Saccharomyces cerevisiae and the opportunistic pathogen Candida albicans via calcineurin Here, we explored effectors downstream of calcineurin regulating this Hsp90-dependent trait Using S cerevisiae erg3 mutants as a model, we determined that both Crz1 and Hph1 modulate azole resistance

Modulators of alpha-synuclein toxicity

Abstract: Disclosed are genes that, when overexpressed in cells expressing alpha-synuclein, either suppress or enhance alpha-synuclein mediated cellular toxicity. Compounds that modulate expression of these genes or activity of the encoded proteins can be used to inhibit alpha-synuclein mediated toxicity and used to treat or prevent synucleinopathies such as Parkinson's disease. Also disclosed are methods of identifying inhibitors of alpha-synuclein mediated toxicity.

Devices from prion-like proteins

Abstract: The present invention provides novel polypeptides comprising a prion- aggregation domain and a second domain; novel polynucleotides encoding such polypeptides; host cells transformed or transfected with such polynucleotides; novel fibrils with specific functionalities and unusually high chemical and thermal stability; and methods of making and using the foregoing in, for example, the production of nanoscale devices.

Dispositifs produits a partir de proteines de type prionique

Abstract: La presente invention concerne de nouveaux polypeptides comprenant un domaine d'agregation de prions et un second domaine, de nouveaux polynucleotides codant pour ces polypeptides, des cellules hotes transformees ou transfectees avec ces polynucleotides, de nouvelles fibrilles presentant des fonctionnalites specifiques et une stabilite chimique et thermique exceptionnellement elevee, ainsi que des procedes de fabrication et d'utilisation de ceux-ci, notamment dans la production de dispositifs nanometriques.