Acute myelogenous leukemia-derived SMAD4 mutations target the protein to ubiquitin-proteasome degradation

Lei Yang, Ning Wang, Yi Tang, Xu Cao, Mei Wan

Research output: Contribution to journalArticle

Abstract

Disruption of transforming growth factor-β (TGFB1/IGF-β) signaling contributes to the formation of human hematological malignancies. Smad4, a tumor suppressor, functions as an essential intracellular signal transducer of the TGF-β signaling pathway. Recent studies have demonstrated that some tumor-derived mutations of Smad4 are associated with protein instability; however, the precise mechanism by which mutated Smad4 proteins undergo rapid degradation remains to be elucidated. A missense mutation of the SMAD4 gene in the Mad homology 1 (MH1) domain (c.305C>T, Pro102Leu) and one frameshift mutation resulting in termination in the Mad homology 2 (MH2) domain (c.1447_1448insAATA, Δ483-552) have been identified in acute myelogenous leukemia. It is not known whether protein instability of these SMAD4 mutants is one of the contributors to TGF-β signaling disruption in acute myelogenous leukemia. Here we report that these two acute myelogenous leukemia-derived SMAD4 mutants are degraded rapidly when compared to their wild-type counterpart. We have demonstrated that both mutated proteins exhibit enhanced polyubiquitination (or polyubiquitylation) and proteasomal degradation. Importantly, we found that β-transducin-repeat-containing protein 1 (β-TrCP1), an F-box protein in the ubiquitin E3 ligase Skp1-Cullin-F-box protein (SCF) complex, directly interacts with and acts as a critical determinant for degradation of both mutated SMAD4 proteins. In addition, small interference RNA (siRNA)-triggered endogenous β-TrCP1 suppression increased the protein expression level of both overexpressed SMAD4 mutants and endogenous mutated SMAD4 protein in acute myelogenous leukemia cells. These data suggest that mutated SMAD4 proteins undergo rapid degradation in acute myelogenous leukemia cells via SCF β-TrCP1 E3 ligase-mediated protein ubiquitination (or ubiquitylation) and subsequent proteasomal degradation.

Original languageEnglish (US)
Pages (from-to)897-905
Number of pages9
JournalHuman mutation
Volume27
Issue number9
DOIs
StatePublished - Sep 1 2006
Externally publishedYes

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Keywords

  • Acute myelogenous leukemia
  • Protein instability
  • SMAD4 gene mutation
  • TGF-β
  • TGFB1
  • Ubiquitin-proteasome pathway
  • β-TrCP1

ASJC Scopus subject areas

  • Genetics
  • Genetics(clinical)

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