Regulation of glioma migration and invasion via modification of Rap2a activity by the ubiquitin ligase Nedd4-1

Oncol Rep. 2017 May;37(5):2565-2574. doi: 10.3892/or.2017.5572. Epub 2017 Apr 11.

Abstract

Νeuronal precursor cell expressed and developmentally downregulated protein (Nedd4-1) is an E3 ubiquitin ligase with critical roles in the pathogenesis of cancer. Herein, we demonstrated that Nedd4-1 protein was upregulated in glioma tissues vs. that in non-cancerous tissues by western blotting and immunohistochemistry. Scratch migration and Transwell chamber assays indicated that downregulation of Nedd4-1 significantly reduced the migration and invasion of the glioma cell lines U251 and U87. Conversely, overexpression of Nedd4-1 obviously enhanced the migratory and invasive capacities in both cell lines. To investigate the role of Nedd4-1 and the intracellular pathways involved, we performed pull-down and co-immunoprecipitation assays, and recognized that Nedd4-1, TNIK and Rap2a formed a complex. Moreover, Nedd4-1 selectively ubiquitinated its specific substrates, the wild-type Rap2a (WT-Rap2a) and dominant-active Rap2a (DA-Rap2a) rather than the dominant-negative Rap2a (DN-Rap2a) in the U251 cells. Subsequently, we demonstrated that Rap2a was robustly ubiquitinated by Nedd4-1 along with the K63-linked, but not the K48-linked ubiquitin chain, which significantly inhibited GTP-Rap2a activity by GST-RalGDS pull-down assay. To further verify whether the ubiquitination of Rap2a by Nedd4-1 regulated the migration and invasion of glioma cells, Nedd4-1, HA-tagged ubiquitin and its mutants as well as WT-Rap2a were co-transfected in the U251 and U87 cell lines. The results confirmed that Nedd4-1 inhibited GTP-Rap2a activity, and promoted the migration and invasion of glioma cells. In brief, our findings demonstrated the important role of Nedd4-1 in regulating the migration and invasion of glioma cells via the Nedd4-1/Rap2a pathway, which may qualify Nedd4-1 as a viable therapeutic target for glioma.

MeSH terms

  • Brain Neoplasms / metabolism
  • Brain Neoplasms / pathology*
  • Cell Line, Tumor
  • Cell Movement
  • Endosomal Sorting Complexes Required for Transport / genetics
  • Endosomal Sorting Complexes Required for Transport / metabolism*
  • Glioma / metabolism
  • Glioma / pathology*
  • Humans
  • Nedd4 Ubiquitin Protein Ligases
  • Ubiquitin-Protein Ligases / genetics
  • Ubiquitin-Protein Ligases / metabolism*
  • Ubiquitination
  • rap GTP-Binding Proteins / genetics
  • rap GTP-Binding Proteins / metabolism*

Substances

  • Endosomal Sorting Complexes Required for Transport
  • Nedd4 Ubiquitin Protein Ligases
  • Nedd4 protein, human
  • Ubiquitin-Protein Ligases
  • RAP2A protein, human
  • rap GTP-Binding Proteins