VprBP targets Merlin to the Roc1-Cul4A-DDB1 E3 ligase complex for degradation

Oncogene. 2008 Jul 3;27(29):4056-64. doi: 10.1038/onc.2008.44. Epub 2008 Mar 10.

Abstract

Inactivation of the neurofibromatosis type 2 (NF2) tumor suppressor gene function has been observed not only in familial schwannomas and other central nervous system tumors, but also in malignant tumors unrelated to the NF2 syndrome, indicating a broader role of NF2 in human tumorigenesis. The NF2-encoded protein Merlin is closely related to the Ezrin-Radixin-Moesin family of membrane/cytoskeleton linker proteins, and has been demonstrated to suppress tumor growth by inhibiting extracellular signal-regulated kinase (ERK) and Rac1 activation. Interestingly, serum deprivation has been shown to regulate Merlin at the protein level, however, exactly how such condition affects Merlin remains elusive. In this study, we provide evidence to show that Merlin is regulated in a Roc1-Cullin4A-DDB1-dependent manner. Following serum stimulation, Merlin is recruited to the E3 ligase complex through a direct interaction with the WD40-containing adaptor protein VprBP. Loading of Merlin to the E3 ubiquitin ligase complex resulted in its polyubiquitination, and consequently its proteasome-mediated degradation. Consistently, VprBP depletion abolished the in vivo interaction of Merlin and Roc1-Cullin4A-DDB1, which resulted in Merlin stabilization and inhibited ERK and Rac activation. Together, our data revealed a novel regulatory mechanism for the tumor suppressor function of Merlin.

Publication types

  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Carrier Proteins / genetics
  • Carrier Proteins / metabolism*
  • Cullin Proteins / genetics
  • Cullin Proteins / metabolism*
  • DNA-Binding Proteins / genetics
  • DNA-Binding Proteins / metabolism*
  • Extracellular Signal-Regulated MAP Kinases / genetics
  • Extracellular Signal-Regulated MAP Kinases / metabolism
  • HeLa Cells
  • Humans
  • Neurilemmoma / genetics
  • Neurilemmoma / metabolism
  • Neurofibromatosis 2 / genetics
  • Neurofibromatosis 2 / metabolism
  • Neurofibromin 2 / genetics
  • Neurofibromin 2 / metabolism*
  • Protein Binding / genetics
  • Protein-Serine-Threonine Kinases
  • Proto-Oncogene Proteins c-akt / genetics
  • Proto-Oncogene Proteins c-akt / metabolism
  • Ubiquitin-Protein Ligases / genetics
  • Ubiquitin-Protein Ligases / metabolism*
  • Ubiquitination*

Substances

  • CUL4A protein, human
  • Carrier Proteins
  • Cullin Proteins
  • DDB1 protein, human
  • DNA-Binding Proteins
  • Neurofibromin 2
  • RBX1 protein, human
  • Ubiquitin-Protein Ligases
  • DCAF1 protein, human
  • Protein-Serine-Threonine Kinases
  • Proto-Oncogene Proteins c-akt
  • Extracellular Signal-Regulated MAP Kinases