A new brain‐specific 14‐kDa protein is a phosphoprotein

Nakajo, Shigeo; Tsukada, K.; Omata, Kumiko; Nakamura, Yasuharu; Nakaya, Kazuyasu

doi:10.1111/j.1432-1033.1993.tb18337.x

Cited by 155 publications

(116 citation statements)

References 30 publications

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“…They are also potent inhibitors of PLD2 in vitro (16), whereas overexpression of synoretin activates Elk-1 transcription factor (10). It has been also suggested that synucleins can be regulated by phosphorylation (7,16), since bovine ␤-synuclein occurs as a phosphoprotein and can be phosphorylated in vitro by CaMKII (17). Recently, it has been shown that ␣-synuclein is phosphorylated in cells and that phosphosynuclein is rapidly dephosphorylated by okadaic acid-sensitive protein phosphatases (18).…”

Section: Figmentioning

confidence: 99%

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Synucleins Are a Novel Class of Substrates for G Protein-coupled Receptor Kinases

Pronin

Morris²,

Surguchov³

et al. 2000

Journal of Biological Chemistry

370

323

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G protein-coupled receptor kinases (GRKs) specifically recognize and phosphorylate the agonist-occupied form of numerous G protein-coupled receptors (GPCRs), ultimately resulting in desensitization of receptor signaling. Until recently, GPCRs were considered to be the only natural substrates for GRKs. However, the recent discovery that GRKs also phosphorylate tubulin raised the possibility that additional GRK substrates exist and that the cellular role of GRKs may be much broader than just GPCR regulation. Here we report that synucleins are a novel class of GRK substrates. Synucleins (␣, ␤, ␥, and synoretin) are 14-kDa proteins that are highly expressed in brain but also found in numerous other tissues. ␣-Synuclein has been linked to the development of Alzheimer's and Parkinson's diseases. We found that all synucleins are GRK substrates, with GRK2 preferentially phosphorylating the ␣ and ␤ isoforms, whereas GRK5 prefers ␣-synuclein as a substrate. GRK-mediated phosphorylation of synuclein is activated by factors that stimulate receptor phosphorylation, such as lipids (all GRKs) and G␤␥ subunits (GRK2/3), suggesting that GPCR activation may regulate synuclein phosphorylation. GRKs phosphorylate synucleins at a single serine residue within the C-terminal domain. Although the function of synucleins remains largely unknown, recent studies have demonstrated that these proteins can interact with phospholipids and are potent inhibitors of phospholipase D2 (PLD2) in vitro. PLD2 regulates the breakdown of phosphatidylcholine and has been implicated in vesicular trafficking. We found that GRK-mediated phosphorylation inhibits synuclein's interaction with both phospholipids and PLD2. These findings suggest that GPCRs may be able to indirectly stimulate PLD2 activity via their ability to regulate GRK-promoted phosphorylation of synuclein.G protein-coupled receptor kinases (GRKs) 1 are involved in the regulation of G protein-coupled receptor (GPCR) signaling (1, 2). GRKs specifically recognize and phosphorylate agonistoccupied GPCRs. Receptor phosphorylation and subsequent binding of another protein, arrestin, uncouples activated receptor from G protein. These events can also promote receptor endocytosis. Internalized receptors are then either dephosphorylated and recycled back to the cell surface or targeted to lysosomes for degradation. The seven mammalian GRKs that have been identified can be divided into three subfamilies based on their overall structural organization and homology: GRK1 (rhodopsin kinase) and GRK7; GRK2 (␤ARK1) and GRK3 (␤ARK2); and GRK4, GRK5, and GRK6. Common features shared by the GRKs include a centrally localized catalytic domain of ϳ270 amino acids, an N-terminal domain of ϳ190 amino acids that has been implicated in receptor interaction and GRK regulation, and a variable length C-terminal domain of 105-233 amino acids that is involved in phospholipid association.Until recently, GPCRs were considered to be the only natural substrates for GRKs. Common protein kinase substrates, such as casein, pho...

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Section: Figmentioning

confidence: 99%

“…We also tested other kinases that have been shown to phosphorylate synucleins. Calmodulin-dependent protein kinase II (CaMKII) was reported to phosphorylate ␤-synuclein (17), whereas recent studies demonstrated that ␣-synuclein can be phosphorylated by the casein kinases CK1 and CK2 (18). Fig.…”

Section: Phosphorylation and Partial Purification Of A Novel Grkmentioning

confidence: 99%

Synucleins Are a Novel Class of Substrates for G Protein-coupled Receptor Kinases

Pronin

Morris²,

Surguchov³

et al. 2000

Journal of Biological Chemistry

370

323

View full text Add to dashboard Cite

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“…3). Mouse ␣-synuclein and human ␤-synuclein are highly homologous to human ␣-synuclein at their carboxyl termini and undergo phosphorylation on serine (36,37). In contrast, ␥-synuclein has very little homology to ␣-synuclein at its carboxyl terminus, and, therefore, it is not surprising that it was not able to compete with the NP peptide in our pulldown experiments (37).…”

Section: ␣-Synuclein Interaction Networkmentioning

confidence: 99%

Proteomics Analysis Identifies Phosphorylation-dependent α-Synuclein Protein Interactions

McFarland

Ellis

Markey

et al. 2008

Molecular & Cellular Proteomics

162

143

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Mutations and copy number variation in theHere we used the combination of peptide pulldown assays and mass spectrometry to identify and compare protein-protein interactions of phosphorylated and nonphosphorylated ␣-synuclein. We showed that non-phosphorylated ␣-synuclein carboxyl terminus pulled down protein complexes that were highly enriched for mitochondrial electron transport proteins, whereas ␣-synuclein carboxyl terminus phosphorylated on either Ser-129 or Tyr-125 did not. Instead the set of proteins pulled down by phosphorylated ␣-synuclein was highly enriched in certain cytoskeletal proteins, in vesicular trafficking proteins, and in a small number of enzymes involved in protein serine phosphorylation. This targeted comparative proteomics approach for unbiased identification of protein-protein interactions sug-

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“…␤-Synuclein is another member of the synuclein family (21,22) that lacks the non-amyloidogenic component (NAC) domain that appears to be responsible for the aggregating properties of ␣-synuclein (23). ␤-Synuclein is therefore considered to be a non-amyloidogenic homolog of ␣-synuclein.…”

mentioning

confidence: 99%

β-Synuclein Displays an Antiapoptotic p53-dependent Phenotype and Protects Neurons from 6-Hydroxydopamine-induced Caspase 3 Activation

Costa

Masliah

Checler

2003

Journal of Biological Chemistry

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We have established stable transfectants expressing ␤-synuclein in TSM1 neurons. We show that in basal and staurosporine-induced conditions the number of terminal deoxynucleotidyltransferase-mediated dUTP nick end-labeling (TUNEL)-positive ␤-synuclein-expressing neurons was drastically lower than in mock-transfected TSM1 cells. This was accompanied by a lower DNA fragmentation as evidenced by the reduction of propidium iodide incorporation measured by fluorescence-activated cell sorter analysis. ␤-Synuclein strongly reduces staurosporine-induced caspase 3 activity and immunoreactivity. We establish that ␤-synuclein triggers a drastic reduction of p53 expression and transcriptional activity. This was accompanied by increased Mdm2 immunoreactivity while p38 expression appeared enhanced, indicating that ␤-synuclein-induced p53 downregulation likely occurs at a post-transcriptional level. We showed previously that ␣-synuclein displays an antiapoptotic function that was abolished by the dopaminergic derived toxin 6-hydroxydopamine (6OHDA). Interestingly, ␤-synuclein retains its ability to protect TSM1 neurons even after 6OHDA treatment. Furthermore, ␤-synuclein restores the antiapoptotic function of ␣-synuclein in 6OHDA-treated neurons. Altogether, our data document for the first time that ␤-synuclein protects neurons from staurosporine and 6OHDA-stimulated caspase activation in a p53-dependent manner. Our observation that ␤-synuclein contributes to restoration of the ␣-synuclein antiapoptotic function abolished by 6OHDA may have direct implications for Parkinson's disease pathology. In this context, the cross-talk between these two parent proteins is discussed.Parkinson's disease (PD) 1 is one of the most common and devastating diseases in the elderly (1, 2). This pathology is characterized by intracellular aggregates, called Lewy bodies (LB) (3, 4) that are thought to be responsible for final dementia occurring not only in PD but also in Lewy body diseases. The main component of LB was identified as ␣-synuclein (5), a 140-amino acid-long synaptic protein (6) that accumulates within these neuropathological hallmarks (7-9). The central role of ␣-synuclein in PD pathology has been emphasized by the observation that familial forms of PD were due to two mutations borne by ␣-synuclein (10, 11). Interestingly, these mutations trigger alterations of the biophysical properties of ␣-synuclein, leading to an exacerbation of misfolding and aggregation (12). Therefore, as with many other neurodegenerative diseases such as Alzheimer's and prion diseases, among others (13-15), PD can be documented as a disease associated with protein misfolding. The fact that such aggregates of proteins were recently shown to exhibit an intrinsic toxic potential (16) could lead to a reunifying theory linking misfolding and neurodegeneration.Interestingly, we have shown that ␣-synuclein displays an antiapoptotic phenotype that was abolished by PD-related mutations (17). This antiapoptotic function was also prevented when neuronal cells were expo...

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A new brain‐specific 14‐kDa protein is a phosphoprotein

Cited by 155 publications

References 30 publications

Synucleins Are a Novel Class of Substrates for G Protein-coupled Receptor Kinases

Synucleins Are a Novel Class of Substrates for G Protein-coupled Receptor Kinases

Proteomics Analysis Identifies Phosphorylation-dependent α-Synuclein Protein Interactions

β-Synuclein Displays an Antiapoptotic p53-dependent Phenotype and Protects Neurons from 6-Hydroxydopamine-induced Caspase 3 Activation

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