XLID CUL4B mutants are defective in promoting TSC2 degradation and positively regulating mTOR signaling in neocortical neurons

Hung Li Wang, Ning Chun Chang, Yi Hsin Weng, Tu Hsueh Yeh

Research output: Contribution to journalArticle

10 Citations (Scopus)

Abstract

Truncating or missense mutation of cullin 4B (CUL4B) is one of the most prevalent causes underlying X-linked intellectual disability (XLID). CUL4B-RING E3 ubiquitin ligase promotes ubiquitination and degradation of various proteins. Consistent with previous studies, overexpression of wild-type CUL4B in 293 cells enhanced ubiquitylation and degradation of TSC2 or cyclin E. The present study shows that XLID mutant (R388X), (R572C) or (V745A) CULB failed to promote ubiquitination and degradation of TSC2 or cyclin E. Adenoviruses-mediated expression of wild-type CUL4B decreased protein level of TSC2 or cyclin E in cultured neocortical neurons of frontal lobe. Furthermore, shRNA-mediated CUL4B knockdown caused an upregulation of TSC2 or cyclin E. XLID mutant (R388X), (R572C) or (V745A) CUL4B did not downregulate protein expression of TSC2 or cyclin E in neocortical neurons. By promoting TSC2 degradation, CUL4B could positively regulate mTOR activity in neocortical neurons of frontal cortex. Consistent with this hypothesis, CUL4B knockdown-induced upregulation of TSC2 in neocortical neurons resulted in a decreased protein level of active phospho-mTORSer2448 and a reduced expression of active phospho-p70S6KThr389 and phospho-4E-BP1Thr37/46, two main substrates of mTOR-mediated phosphorylation. Wild-type CUL4B also increased protein level of active phospho-mTORSer2448, phospho-p70S6KThr389 or phospho-4E-BP1Thr37/46. XLID CUL4B mutants did not affect protein level of active phospho-mTORSer2448, phospho-p70S6KThr389 or phospho-4E-BP1Thr37/46. Our results suggest that XLID CUL4B mutants are defective in promoting TSC2 degradation and positively regulating mTOR signaling in neocortical neurons.

Original languageEnglish
Pages (from-to)585-593
Number of pages9
JournalBiochimica et Biophysica Acta - Molecular Basis of Disease
Volume1832
Issue number4
DOIs
Publication statusPublished - Apr 2013
Externally publishedYes

Keywords

  • Cullin 4B
  • Cyclin E
  • MTOR
  • Neocortical neurons
  • TSC2
  • X-linked intellectual disability

ASJC Scopus subject areas

  • Molecular Biology
  • Molecular Medicine

Fingerprint Dive into the research topics of 'XLID CUL4B mutants are defective in promoting TSC2 degradation and positively regulating mTOR signaling in neocortical neurons'. Together they form a unique fingerprint.

  • Cite this