CUL2-mediated clearance of misfolded TDP-43 is paradoxically affected by VHL in oligodendrocytes in ALS

Sci Rep. 2016 Jan 11:6:19118. doi: 10.1038/srep19118.

Abstract

The molecular machinery responsible for cytosolic accumulation of misfolded TDP-43 in amyotrophic lateral sclerosis (ALS) remains elusive. Here we identified a cullin-2 (CUL2) RING complex as a novel ubiquitin ligase for fragmented forms of TDP-43. The von Hippel Lindau protein (VHL), a substrate binding component of the complex, preferentially recognized misfolded TDP-43 at Glu246 in RNA-recognition motif 2. Recombinant full-length TDP-43 was structurally fragile and readily cleaved, suggesting that misfolded TDP-43 is cleared by VHL/CUL2 in a step-wise manner via fragmentation. Surprisingly, excess VHL stabilized and led to inclusion formation of TDP-43, as well as mutant SOD1, at the juxtanuclear protein quality control center. Moreover, TDP-43 knockdown elevated VHL expression in cultured cells, implying an aberrant interaction between VHL and mislocalized TDP-43 in ALS. Finally, cytoplasmic inclusions especially in oligodendrocytes in ALS spinal cords were immunoreactive to both phosphorylated TDP-43 and VHL. Thus, our results suggest that an imbalance in VHL and CUL2 may underlie oligodendrocyte dysfunction in ALS, and highlight CUL2 E3 ligase emerges as a novel therapeutic potential for ALS.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amyotrophic Lateral Sclerosis / metabolism*
  • Amyotrophic Lateral Sclerosis / pathology
  • Animals
  • Cullin Proteins / metabolism*
  • DNA-Binding Proteins / chemistry
  • DNA-Binding Proteins / metabolism*
  • Epitopes / metabolism
  • HEK293 Cells
  • HeLa Cells
  • Humans
  • Hypoxia-Inducible Factor 1, alpha Subunit / metabolism
  • Immunohistochemistry
  • Inclusion Bodies / metabolism
  • Mice, Transgenic
  • Models, Biological
  • Mutant Proteins / metabolism
  • Oligodendroglia / metabolism*
  • Phosphorylation
  • Proteasome Endopeptidase Complex / metabolism
  • Protein Aggregates
  • Protein Binding
  • Protein Domains
  • Protein Folding*
  • Protein Stability
  • Proteolysis
  • Rats
  • Superoxide Dismutase / metabolism
  • Ubiquitin / metabolism
  • Ubiquitination
  • Von Hippel-Lindau Tumor Suppressor Protein / metabolism*

Substances

  • CUL2 protein, human
  • Cullin Proteins
  • DNA-Binding Proteins
  • Epitopes
  • HIF1A protein, human
  • Hypoxia-Inducible Factor 1, alpha Subunit
  • Mutant Proteins
  • Protein Aggregates
  • TARDBP protein, human
  • Ubiquitin
  • Superoxide Dismutase
  • Von Hippel-Lindau Tumor Suppressor Protein
  • Proteasome Endopeptidase Complex
  • VHL protein, human