Dominant negative form of alpha4 inhibits the BCR crosslinking-induced phosphorylation of Bcl-xL and apoptosis in an immature B cell line WEHI-231

Biomed Res. 2015;36(2):97-102. doi: 10.2220/biomedres.36.97.

Abstract

We previously demonstrated that c-Jun N-terminal kinase (JNK) phosphorylates serine 62 of Bcl-xL to induce the degradation of Bcl-xL and apoptosis in WEHI-231 cells upon BCR crosslinking. In order to elucidate the regulatory mechanisms underlying the phosphorylation of Bcl-xL, we prepared an assay system in which JNK phosphorylated Bcl-xL in HEK293T cells. Consequently, we found that a signal transduction molecule, alpha4, enhanced the phosphorylation of Bcl-xL by JNK, while the co-expression of C-terminal alpha4 (220-340) diminished the phosphorylation of Bcl-xL induced by JNK. Furthermore, full-length alpha4 associated with both JNK and Bcl-xL, whereas C-terminal alpha4 (220-340) associated only with Bcl-xL, not JNK. In addition, WEHI-231 cells transfected with the cDNA of C-terminal alpha4 (220-340) exhibited decreased phosphorylation of Bcl-xL and stronger resistance to apoptosis induced by BCR crosslinking. These results indicate that alpha4 is an important regulatory molecule of apoptosis induced by BCR crosslinking in WEHI-231 cells and that C-terminal alpha4 (220-340) functions as a dominant negative form.

MeSH terms

  • Adaptor Proteins, Signal Transducing
  • Apoptosis
  • HEK293 Cells
  • Humans
  • Intracellular Signaling Peptides and Proteins / physiology*
  • Molecular Chaperones
  • Phosphorylation
  • Precursor Cells, B-Lymphoid / physiology*
  • Protein Processing, Post-Translational
  • Proto-Oncogene Proteins c-bcr / physiology*
  • bcl-X Protein / metabolism*

Substances

  • Adaptor Proteins, Signal Transducing
  • BCL2L1 protein, human
  • IGBP1 protein, human
  • Intracellular Signaling Peptides and Proteins
  • Molecular Chaperones
  • bcl-X Protein
  • BCR protein, human
  • Proto-Oncogene Proteins c-bcr