A Powerful Yeast Model to Investigate the Synergistic Interaction of α-Synuclein and Tau in Neurodegeneration

Abstract

Several studies revealed consistent overlap between synucleinopathies and tauopathies, demonstrating that α-synuclein (ASYN) and tau co-localize in neurofibrillary tangles and in Lewy bodies from Alzheimer’s and Parkinson’s disease patients and corresponding animal models. Additionally, it has been shown that ASYN can act as an initiator of tau aggregation and phosphorylation and that these two proteins directly interact. Despite these evidences, the cellular pathway implicated in this synergistic interaction remains to be clarified. The aim of this study was to create a yeast model where the concomitant expression of ASYN and tau can be used to perform genome wide screenings for the identification of genes that modulate this interaction, in order to shed light into the pathological mechanism of cell dysfunction and to provide new targets for future therapeutic intervention. We started by validating the synergistic toxicity of tau and ASYN co-expression in yeast, by developing episomal and integrative strains expressing WT and mutant forms of both proteins, alone or in combination. The episomal strains showed no differences in growth delay upon expression of ASYN isoforms (WT or A53T) alone or in combination with tau 2N/4R isoforms (WT or P301L). However, in these strains, the presence of ASYN led to increased tau insolubility and correlated with increased tau phosphorylation in S396/404, which is mainly mediated by RIM11, the human homolog of GSK3β in yeast. On the other hand, the integrative strains showed a strong synergistic toxic effect upon co-expression of ASYN WT and tau WT, which was related to high levels of intracellular ASYN inclusions and increased tau phosphorylation and aggregation. Taken together, the strains described in the present study are able to mimic relevant pathogenic features involved in neurodegeneration and are powerful tools to identify potential target genes able to modulate the synergistic pathway driven by ASYN and tau interaction.

GSK-3β dysregulation contributes to parkinson’s-like pathophysiology with associated region-specific phosphorylation and accumulation of tau and α-synuclein

“…25,26 The aforementioned studies combined with our current results suggest that hyperactivation of GSK-3β may be the primary mechanism by which this protein is linked to PD (Figure 7). Indeed, a growing body of evidence from our laboratory and others define the important roles, kinases, such as GSK-3β, CK2, PLK2 and 3, and GRK1-5 have in the development and pathology of PD through the phosphorylation of α-Syn and Tau 16,[18][19][20][21][22][23][24][53][54][55][56][57] (Supplementary Table S3 and associated references).…”

“…High levels of p-Tau have also been observed in vivo in several toxin [16][17][18] and transgenic α-Syn models of PD, 19,20 suggesting that p-Tau may be an important common factor in the neurodegeneration of not only tauopathies but also of synucleinopathies, such as PD. [21][22][23][24] Most studies to date have focused on the formation and accumulation of Tau and p-Tau in idiopathic PD. Yet several studies have provided evidence that leucine-rich repeat kinase-2 (LRRK2), a kinase, that when mutated is involved in familial forms of PD, can directly interact with, and activate GSK-3β, resulting in increased p-TAU formation.…”

α-Synuclein Shows High Affinity Interaction with Voltage-dependent Anion Channel, Suggesting Mechanisms of Mitochondrial Regulation and Toxicity in Parkinson Disease

“…Cell lysates were prepared as described (37). Briefly, cells were harvested by centrifugation, washed in double-distilled H 2 O.…”

Signaling pathways and posttranslational modifications of tau in Alzheimer's disease: the humanization of yeast cells

“…Yet, it has been reported that co-expression with the gene encoding synuclein aggravates the toxic effects of overexpression of the latter [88]. More recently, co-expression of tau and α-synuclein genes from genetically stable single-copy yeast integrants confirmed the strong synergistic toxicity [89] which was attributed to the formation of inclusions of α-synuclein and of insoluble cytoplasmic tau aggregates.…”