PubMed Health⌕ Search
Home/Archive/PubMed

PubMed · 11560921

alpha-Synuclein affects the MAPK pathway and accelerates cell death.

A Iwata·M Maruyama·I Kanazawa·N Nukina
View original source ↗Export metadata ↓

Abstract

Insoluble alpha-synuclein accumulates in Parkinson's disease, diffuse Lewy body disease, and multiple system atrophy. However, the relationship between its accumulation and pathogenesis is still unclear. Recently, we reported that overexpression of alpha-synuclein affects Elk-1 phosphorylation in cultured cells, which is mainly performed by mitogen-activated protein kinases (MAPKs). We further examined the relationship between MAPK signaling and the effects of alpha-synuclein expression on ecdysone-inducible neuro2a cell lines and found that cells expressing alpha-synuclein had less phosphorylated MAPKs. Moreover, they showed significant cell death when the concentration of serum in the culture medium was reduced. Under normal serum conditions, the addition of the MAPK inhibitor U0126 also caused cell death in alpha-synuclein-expressing cells. Transfection of constitutively active MEK-1 resulted in MAPK phosphorylation in alpha-synuclein-expressing cells and improved cell viability even under reduced serum conditions. Thus, we conclude that alpha-synuclein regulates the MAPK pathway by reducing the amount of available active MAPK. Our findings suggest a mechanism for pathogenesis and thus offer therapeutic insight into synucleinopathies.

Explore related subjects

14-3-3 ProteinsAmino Acid SequenceApoptosisBlotting, NorthernButadienesCell DeathCell LineCell SurvivalColoring AgentsDNA, ComplementaryDose-Response Relationship, DrugEnzyme InhibitorsGene LibraryGlutathione TransferaseHumansImmunoblottingImmunohistochemistryIn Situ Nick-End LabelingMAP Kinase Signaling SystemMolecular Sequence DataMutationNerve Tissue ProteinsNitrilesPhosphorylationPlasmidsPrecipitin TestsProtein BindingRecombinant Fusion ProteinsSequence Homology, Amino AcidSignal TransductionSynucleinsTetrazolium SaltsThiazolesTime FactorsTransfectionTyrosine 3-Monooxygenasealpha-SynucleinJournal Article

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

A Iwata, M Maruyama, I Kanazawa, N Nukina. 2001-09-17. alpha-Synuclein affects the MAPK pathway and accelerates cell death.. https://doi.org/10.1074/jbc.m103736200

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related citations

PubMed2025

Mathematical modeling suggests 14-3-3 proteins modulate RAF paradoxical activation.

RAF inhibitor "paradoxical activation" (PA) is a phenomenon where RAF kinase inhibitors increase RAF kinase signaling. Through mathematical modeling and experimental data analysis, we recently demonstrated that the combination of conformational autoinhibition (CA) with the disruption of CA by RAF inhibitors plays an important role in PA. 14-3-3 proteins are known to modulate RAF CA and RAF dimerization. We here extend our mathematical model to include both roles of 14-3-3 proteins, and we derive rigorous analytical expressions of RAF signal regulation as modulated by 14-3-3 proteins. We then use the model to investigate how 14-3-3 proteins may modulate PA. We mathematically show 14-3-3 protein stabilization of the autoinhibited form of RAF should potentiate PA, while 14-3-3 protein stabilization of the active RAF dimer should reduce PA. Our analysis suggests that the net-effect will often be a potentiation of PA, and that 14-3-3 proteins may be capable of inducing PA for RAF inhibitors that normally show little to no PA. We test model-based insights experimentally with two different approaches: forced increases in 14-3-3 expression (which we find amplifies PA) and evolved resistance assays (which suggest increased 14-3-3 expression may contribute to resistance to RAF inhibitors). Overall, this work supports a role for 14-3-3 in modulating RAF-inhibitor mediated paradoxical activation.

14-3-3 Proteins↗
PubMed2003

Teleost Fh14-3-3a protein protects Xenopus oocytes from hyperosmolality.

We have previously cloned and characterized a novel 14-3-3 gene from the euryhaline telost Fundulus heteroclitus, Fh14-3-3a (Kültz et al., 2001). The corresponding gene product is osmoregulated and most highly expressed in gill epithelium of this fish. In the present study we have expressed Fh14-3-3a cRNA in Xenopus laevis oocytes and investigated the survival and electrophysiological parameters of Xenopus oocytes in isosmotic and various hyperosmotic media. Xenopus oocytes expressing Fh14-3-3a show no mortality after a 16 hour exposure to hyperosmolality in the form of elevating medium K(+), Na(+), polyethylene glycol, or sorbitol concentrations up to 444 mosmol/kg. In contrast, 16 hours of the same hyperosmolality caused 100% mortality in control Xenopus oocytes injected with water. As a result of hyperosmolality the Xenopus oocyte membrane potential decreased between 10 and 70% in oocytes expressing Fh14-3-3a whereas it was completely abolished in control oocytes. We report that one potential cause for the osmoprotective effect of Fh14-3-3a on Xenopus oocytes could be its inhibition of an endogenous chloride current. Hyperosmotic urea was not as harmful to Xenopus oocytes as hypertonicity and maybe acting through a different mechanism. Coexpression of Fh14-3-3a with a human calcium channel in Xenopus oocytes did not affect the electrophysiological properties of this exogenous channel. Thus, the osmoprotective effect of Fh14-3-3a may prove a valuable tool for the characterization of exogenous ion channels in Xenopus oocytes exposed to hyperosmotic conditions.

14-3-3 Proteins↗
PubMed2003

Alternative splicing as a mechanism for regulating 14-3-3 binding: interactions between hD53 (TPD52L1) and 14-3-3 proteins.

D52 (TPD52)-like proteins are coiled-coil motif-bearing proteins first identified through their expression in human breast carcinoma, which have been proposed to represent signalling intermediates and regulators of vesicle trafficking. D52-like gene transcripts are subject to alternative splicing, with sequences encoding a region termed insert 3 being affected in all three D52-like genes. We have now identified a 14-3-3 binding motif within one of two alternatively spliced exons encoding insert 3. As predicted from the distribution of 14-3-3 binding motifs in four hD52-like bait proteins tested, only a hD53 isoform encoding a 14-3-3 binding motif bound both 14-3-3beta and 14-3-3zeta preys in the yeast two-hybrid system. Since D53 proteins carrying 14-3-3 binding motifs are predicted to be widely expressed, polyclonal antisera were derived to specifically detect these isoforms. Using soluble protein extracts from breast carcinoma cell lines, pull-down assays replicated interactions between recombinant 14-3-3beta and 14-3-3zeta isoforms and exogenously expressed hD53, and co-immunoprecipitation analyses demonstrated interactions between endogenous 14-3-3 and both endogenously and exogenously-expressed hD53 protein. Co-expressed hD53 and 14-3-3 proteins were similarly demonstrated to co-localise within the cytoplasm of breast carcinoma cell lines. These results identify 14-3-3 proteins as partners for hD53, and alternative splicing as a mechanism for regulating 14-3-3 binding.

14-3-3 Proteins↗