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 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

α-Synuclein – Regulator of Exocytosis, Endocytosis, or Both?

“…Furthermore, a-synuclein could this way influence the proximity of synaptic vesicles to voltage-gated calcium channels in the plasma membrane, which has been shown to regulate the mode of exo-and endocytosis by influencing the local calcium environment [23]. [17,24,25]. However, on the other side, there is strong evidence that a-synuclein is a positive modulator of SNAREcomplex assembly, as shown in mice with a knockout of the cysteine-string protein a (CSPa).…”

“…Intriguingly, overexpression of Rab proteins has been shown to rescue a-synuclein toxicity [24,25,71]. Rab proteins are key players in the endosomal sorting of vesicles, and they are therefore crucial for retrieving new functional synaptic vesicles.…”

A Predictable Worm: Application of Caenorhabditis elegans for Mechanistic Investigation of Movement Disorders

“…The combined use of multiple animal models supported the roles of these proteins in α-syn toxicity. Suppression of cytotoxicity was identified in Drosophila (Rab1), rat neuronal cell cultures (Rab1 and Rab8A), and in C. elegans (Rab1 and Rab8A), where we showed that elevated expression of these specific Rab GTPases rescues DA degeneration induced by human α-syn overexpression [24,25] (Fig. 3b).…”

“…(b) Yeast screens for suppressors of α-synuclein toxicity have yielded gene candidates that were subsequently examined in C. elegans and drosophila for the ability to reduce the neurodegeneration associated with α-synuclein overexpression. Candidates that reduce toxicity in both yeast and invertebrate neuronal systems also protected rat primary neurons from degeneration following transfection with A53T α-synuclein [24,28]. (c) A C. elegans hypothesis-based RNA interference (RNAi) screen for effectors of α-synuclein protein misfolding [14] identified candidates that were reported to cause neurodegeneration in a mouse knockout model (ATG7 [37]), as a risk factor for PD (ULK2 [36]), or neuroprotective in human cells when overexpressed (VPS41 [33]).…”

A suite of Gateway® cloning vectors for high‐throughput genetic analysis in Saccharomyces cerevisiae

“…In addition, the yeast genome is very well characterized and amenable to genetic manipulation. Methods are available to rapidly overexpress or knock out almost every gene, and efforts to generate a collection of haploid strains, each harbouring a single mutation, as well as a collection of expression plasmids with each yeast ORF under the control of an inducible promoter, have recently come to fruition (Cooper et al, 2006;Sopko et al, 2006). The availability of these tools turns yeast into a robust new system for investigating, on a genome-wide scale, the mechanisms underlying many cellular processes, with direct relevance to human disease and for the discovery of novel drug targets for therapeutic intervention.…”