Importin-α protein binding to a nuclear localization signal of carbohydrate response element-binding protein (ChREBP)

Qiang Ge, Tsutomu Nakagawa, R. Max Wynn, Yuh Min Chook, Bonnie C. Miller, Kosaku Uyeda

Research output: Contribution to journalArticle

21 Scopus citations

Abstract

Carbohydrate response element-binding protein (ChREBP) is a glucose-responsive transcription factor that plays a critical role in the glucose-mediated induction of genes involved in hepatic glycolysis and lipogenesis. Circulating blood glucose levels affect ChREBP activity in hepatocytes largely by post-translational mechanisms that include phosphorylation-dependent subcellular localization. Previously, we showed that ChREBP is retained in the cytosol by phosphorylation-dependent binding to 14-3-3 protein dimers and identified the α2 helix (residues 125-135) phospho-Ser 140 domain as the primary 14-3-3 binding site (Sakiyama, H., Wynn, R. M., Lee, W. R., Fukasawa, M., Mizuguchi, H., Gardner, K. H., Repa, J. J., and Uyeda, K. (2008) J. Biol. Chem. 283, 24899-24908). To enter the nucleus in response to high glucose, ChREBP must bind importin-α; this heterodimer then forms a complex with importin-β to interact with the nuclear pore complex. In this work, we recharacterized the importin-α binding nuclear localization signal (NLS) of rat ChREBP, identifying it as an extended classical bipartite NLS encompassing minimally residues 158-190. Replacing Lys 159/Lys 190 residues of ChREBP with alanine resulted in loss of importin-α binding, glucose-stimulated transcriptional activity and nuclear localization.Asecondary 14-3-3 protein binding site also was identified, the α3 helix (residues 170-190) phospho-Ser 196 domain. Importin-α and 14-3-3 were found to bind competitively to this secondary site. These results suggest an important mechanism by which importin-α and 14-3-3 control movement of ChREBP in and out of the nucleus in response to changes in glucose levels in liver and thus further suggest that the extended NLS of ChREBP is a critical glucose-sensing, glucose-responsive site.

Original languageEnglish (US)
Pages (from-to)28119-28127
Number of pages9
JournalJournal of Biological Chemistry
Volume286
Issue number32
DOIs
StatePublished - Aug 12 2011

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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