Alpha-synuclein (αSyn) misfolding is associated with several devastating neurodegenerative disorders, including Parkinson's 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.Parkinson's disease (PD) is the second most common neurodegenerative disorder (1,2). Accruing evidence points to a causative role for the presynaptic protein alpha-synuclein (αSyn) in PD pathogenesis. αSyn is a major constituent of Lewy Bodies-cellular inclusions that are the hallmark pathological feature of PD and other neurodegenerative disorders collectively

Prion proteins can serve as genetic elements by adopting distinct physical and functional states that are self-perpetuating and heritable. The critical region of one prion protein, Sup35, is initially unstructured in solution and then forms self-seeded amyloid fibers. We examined in vitro the mechanism by which this state is attained and replicated. Structurally fluid oligomeric complexes appear to be crucial intermediates in de novo amyloid nucleus formation. Rapid assembly ensues when these complexes conformationally convert upon association with nuclei. This model for replicating protein-based genetic information, nucleated conformational conversion, may be applicable to other protein assembly processes.

Multivesicular bodies (MVBs) are unique organelles in the endocytic pathway that contain vesicles in their lumen. Sorting and incorporation of material into such vesicles is a critical cellular process that has been intensely studied following discovery of the ESCRT (endosomal sorting complex required for transport) machinery just more than a decade ago. In this review, we summarize current understanding of the cellular functions of MVBs and how the ESCRT machinery contributes to MVB morphogenesis. We also highlight the importance of MVBs and ESCRTs in human health. We identify critical areas in which further mechanistic and spatiotemporal studies in living cells will advance this exciting area of research.

Cells respond to stimuli by changes in various processes, including signaling pathways and gene expression. Efforts to identify components of these responses increasingly depend on mRNA profiling and genetic library screens, yet the functional roles of the genes identified by these assays often remain enigmatic. By comparing the results of these two assays across various cellular responses, we found that they are consistently distinct. Moreover, genetic screens tend to identify response regulators, while mRNA profiling frequently detects metabolic responses. We developed an integrative approach that bridges the gap between these data using known molecular interactions, thus highlighting major response pathways. We harnessed this approach to reveal cellular pathways related to alpha-synuclein, a small lipid-binding protein implicated in several neurodegenerative disorders including Parkinson disease. For this we screened an established yeast model for alphasynuclein toxicity to identify genes that when overexpressed alter cellular survival. Application of our algorithm to these data and data from mRNA profiling provided functional explanations for many of these genes and revealed novel relations between alpha-synuclein toxicity and basic cellular pathways.Cells live in a dynamic environment in which they confront various perturbations such as sudden environmental changes, toxins, and mutations. The response to such perturbations is #To whom correspondence should be addressed. E-mail: lindquist_admin@wi.mit.edu (S. L.); fraenkel-admin@mit.edu (E.F.). 7 Present Address: Department of Cell and Developmental Biology, The University of Pennsylvania, Philadelphia, PA, USA 8 Present Address: Medical College of Georgia, Augusta, GA, USA 9 Present Address: Boston Biomedical Research Institute, Watertown, MA, USA. * These authors contributed equally to this work + These authors contributed equally to this work Summary: A novel approach that integrates genetic hits, differentially expressed genes and known molecular interactions reveals a dramatically enhanced view of cellular responses and was used to create the first cellular map of alpha-synuclein toxicity. NIH Public Access Author ManuscriptNat Genet. Author manuscript; available in PMC 2009 September 1. NIH-PA Author ManuscriptNIH-PA Author Manuscript NIH-PA Author Manuscript typically complex and comprises signaling and metabolic changes, as well as changes in gene expression. Revealing the cellular mechanisms responding to a specific perturbation may unravel its nature, thus illuminating disease mechanisms 1 or a drug's mode of action 2 ,3 , and identify points of intervention with potential therapeutic value 4 .High-throughput experimental techniques including mRNA profiling and genetic screening are commonly used for revealing components of these response pathways because they provide a genome-and proteome-wide view of molecular changes. mRNA profiling experiments rapidly identify genes that are differentially expressed following stimuli. Genetic screening...