NUB1 suppresses the formation of Lewy body-like inclusions by proteasomal degradation of synphilin-1

Am J Pathol. 2006 Aug;169(2):553-65. doi: 10.2353/ajpath.2006.051067.

Abstract

NUB1 is a potent down-regulator of the ubiquitin-like protein NEDD8, because it targets NEDD8 to the proteasome for proteolytic degradation. From results in this study, we found that NUB1 physically interacts with synphilin-1 through its NEDD8-binding site, implying that NUB1 also targets synphilin-1 to the proteasome for degradation. Synphilin-1 is a major component of inclusion bodies found in the brains of patients with neurodegenerative alpha-synucleinopathies, including Parkinson's disease. In this study, we immunostained sections of brains from patients with Parkinson's disease and other alpha-synucleinopathies and demonstrated that NUB1, as well as synphilin-1, accumulates in the inclusion bodies. To define the role of NUB1 in the formation of these inclusion bodies, we performed a co-transfection assay using cultured HEK293 cells. This assay showed that NUB1 suppresses the formation of synphilin-1-positive inclusions. Further, biochemical assays revealed that NUB1 overexpression leads to the proteasomal degradation of synphilin-1. These results and our previous observations suggest that NUB1 indeed targets synphilin-1 to the proteasome for its efficient degradation, which, because of the resultant reduction in synphilin-1, suppresses the formation of synphilin-1-positive inclusions.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Binding Sites
  • Brain / cytology
  • Brain / pathology
  • Carrier Proteins / metabolism*
  • Cells, Cultured
  • Down-Regulation / genetics
  • Gene Expression Profiling
  • Guanidine / metabolism
  • Humans
  • Lewy Bodies / metabolism*
  • Lewy Bodies / pathology
  • NEDD8 Protein
  • Nerve Tissue Proteins / metabolism*
  • Proteasome Endopeptidase Complex / metabolism*
  • Protein Binding
  • Protein Processing, Post-Translational*
  • Protein Transport
  • RNA Interference
  • RNA, Messenger / genetics
  • RNA, Messenger / metabolism
  • Sodium Dodecyl Sulfate / metabolism
  • Solubility
  • Solutions
  • Transcription Factors / genetics
  • Transcription Factors / metabolism*
  • Ubiquitins / metabolism
  • Urea / metabolism
  • Yeasts / cytology
  • alpha-Synuclein / metabolism

Substances

  • Carrier Proteins
  • NEDD8 Protein
  • NEDD8 protein, human
  • NUB1 protein, human
  • Nerve Tissue Proteins
  • RNA, Messenger
  • SNCAIP protein, human
  • Solutions
  • Transcription Factors
  • Ubiquitins
  • alpha-Synuclein
  • Sodium Dodecyl Sulfate
  • Urea
  • Proteasome Endopeptidase Complex
  • Guanidine