Pseudolaric acid B-driven phosphorylation of c-Jun impairs its role in stabilizing HIF-1alpha: a novel function-converter model

J Mol Med (Berl). 2012 Aug;90(8):971-81. doi: 10.1007/s00109-012-0865-4. Epub 2012 Mar 10.

Abstract

We have recently discovered that c-Jun executes a non-transcriptional function to stabilize hypoxia inducible factor 1α (HIF-1α) and that pseudolaric acid B (PAB) accelerates HIF-1α degradation and phosphorylates c-Jun at Ser63/73. In this study, PAB was used as a probe to investigate whether and how the Ser63/73 phosphorylation of c-Jun regulates its functions. The PAB-induced reduction of HIF-1α protein was rescued through supplying additional non-phosphorylated c-Jun. However, c-Jun siRNA, which reduced both the PAB-driven phosphorylated c-Jun and the total c-Jun protein, did not prevent the PAB-induced decrease in HIF-1α. HIF-1α was revealed to be co-immunoprecipitated only with the non-phosphorylated c-Jun. PAB increased the phosphorylated c-Jun while reducing the non-phosphorylated c-Jun at Ser63/73, which impaired its function in stabilizing HIF-1α. Consequently, PAB led to the degradation of HIF-1α, thus resulting in the decreased HIF-1α-dependent expression of mdr-1 and VEGF. We accordingly propose a function-converter model of c-Jun: the Ser63/73 phosphorylation serves as a function converter to convert c-Jun from its non-transcriptional function to its transcriptional function.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Blotting, Western
  • Diterpenes / pharmacology*
  • Enzyme-Linked Immunosorbent Assay
  • HeLa Cells
  • Hep G2 Cells
  • Humans
  • Hypoxia-Inducible Factor 1, alpha Subunit / metabolism*
  • Immunoprecipitation
  • Phosphorylation / drug effects
  • Protein Binding / drug effects
  • Protein Stability / drug effects
  • Proto-Oncogene Proteins c-jun / metabolism*
  • Reverse Transcriptase Polymerase Chain Reaction

Substances

  • Diterpenes
  • Hypoxia-Inducible Factor 1, alpha Subunit
  • Proto-Oncogene Proteins c-jun
  • pseudolaric acid B