Expression of constitutively active Raf-1 in the mitochondria restores antiapoptotic and leukemogenic potential of a transformation-deficient BCR/ABL mutant.

Published

Journal Article

The oncogenic BCR/ABL protein protects hematopoietic cells from apoptosis induced by growth factor deprivation, but the mechanisms are only partially understood. A BCR/ABL mutant lacking amino acids 176-426 in the BCR domain (p185DeltaBCR) failed to protect interleukin 3-deprived 32Dcl3 myeloid precursor cells from apoptosis, although it possessed tyrosine kinase activity and was capable of activating the Ras-Raf-MAP kinase pathway. Compared to p185 wild-type transfectants, p185DeltaBCR-transfected cells showed markedly reduced levels of Bcl-2 and expressed the hypophosphorylated, proapoptotic form of BAD. Bcl-2 expression in the mitochondrial fraction of p185DeltaBCR cells was also markedly diminished and mitochondrial RAF was undetectable. In p185DeltaBCR cells transfected with a mitochondria-targeted, constitutively active RAF (M-Raf) BAD was expressed in the hyperphosphorylated form and released from the mitochondria into the cytosol. p185DeltaBCR/M-Raf-transfected cells were completely resistant to apoptosis induced by growth factor deprivation in vitro. Moreover, constitutive expression of dominant-negative M-Raf (K375W) enhanced the susceptibility of 32Dcl3 cells expressing wild-type BCR/ABL to apoptosis. In severe combined immunodeficiency (SCID) mice, p185DeltaBCR/M-Raf double transfectants were leukemogenic, whereas cells expressing only p185DeltaBCR showed no leukemogenic potential. Together, these data support the existence of a BCR/ABL-dependent pathway that leads to expression of an active RAF in the mitochondria and promotes antiapoptotic and leukemia-inducing effects of BCR/ABL.

Full Text

Duke Authors

Cited Authors

  • Salomoni, P; Wasik, MA; Riedel, RF; Reiss, K; Choi, JK; Skorski, T; Calabretta, B

Published Date

  • June 15, 1998

Published In

Volume / Issue

  • 187 / 12

Start / End Page

  • 1995 - 2007

PubMed ID

  • 9625759

Pubmed Central ID

  • 9625759

International Standard Serial Number (ISSN)

  • 0022-1007

Digital Object Identifier (DOI)

  • 10.1084/jem.187.12.1995

Language

  • eng

Conference Location

  • United States