Casein kinase II-mediated phosphorylation regulates alpha-synuclein/synphilin-1 interaction and inclusion body formation.

Genetic Pharmacology Unit, NINDS, National Institutes of Health, Bethesda, Maryland 20824, USA.
Alpha-synuclein is a phosphoprotein that accumulates as a major component of Lewy bodies in the brains of patients with Parkinson disease. Synphilin-1, which is also present in Lewy bodies, binds with alpha-synuclein and forms cytoplasmic inclusions in transfected cells. Yet the molecular determinants of this protein-protein interaction are unknown. Here we report that casein kinase II (CKII) phosphorylates synphilin-1 and that the beta subunit of this enzyme complex binds to synphilin-1. Additionally, both CKII alpha and beta subunits are present within cytoplasmic inclusions in cells that overexpress synphilin-1. Notably, the interaction between synphilin-1 and alpha-synuclein is markedly dependent on phosphorylation. Inhibition of CKII activity by 5,6-dichloro-1-beta-D-ribofuranosylbenzimidazole blocks the binding between these two proteins and significantly reduces the percentage of cells that contain eosinophilic cytoplasmic inclusions. Mutation of the major CKII phosphorylation site in alpha-synuclein (S129A) has no significant impact on the binding between alpha-synuclein and synphilin-1 or on the formation of synphilin-1/alpha-synuclein-positive inclusions. These data suggest that the CKII-mediated phosphorylation of synphilin-1 rather than that of alpha-synuclein is critical in modulating their tendency to aggregate into inclusions. These observations collectively indicate that a ubiquitous post-translational modification such as phosphorylation can regulate inclusion body formation in the context of alpha-synuclein and synphilin-1 interaction.
Mesh Terms:
Animals, Binding Sites, Blotting, Western, Carrier Proteins, Casein Kinase II, Cell Line, Cytoplasm, Dichlororibofuranosylbenzimidazole, Humans, Immunohistochemistry, Microscopy, Fluorescence, Mutation, Nerve Tissue Proteins, PC12 Cells, Phosphorylation, Protein Binding, Protein Processing, Post-Translational, Protein-Serine-Threonine Kinases, Rats, Serine, Synucleins, Transfection, alpha-Synuclein
J. Biol. Chem. Feb. 20, 2004; 279(8);6834-9 [PUBMED:14645218]
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