Overload of the heat-shock protein H11/HspB8 triggers melanoma cell apoptosis through activation of transforming growth factor-beta-activated kinase 1.
Molecular therapeutics is a recognized promising approach for melanoma, but relevant target genes remain elusive. We report that overload of the recently cloned H11/HspB8 induces apoptosis in 55% of examined melanoma cultures. Apoptosis was determined by activation of caspases-9 and -3 and terminal deoxynucleotidyltransferase-mediated dUTP nick end labeling (TUNEL), and was not seen in normal melanocytes. It was associated with H11/HspB8 complexation with transforming growth factor-beta-activated kinase (TAK) 1 and activation of TAK1 and p38 mitogen activated protein 3 kinases. TAK1 was not bound, nor activated by the H11/HspB8 mutant W51C, which has dominant antiapoptotic activity. beta-Catenin was phosphorylated by activated TAK1, inhibiting its nuclear accumulation and mictophthalmia-associated transcription factor and cyclin dependent kinase 2 expression. The dominant-negative TAK1 mutant K63W inhibited beta-catenin phosphorylation and caspase activation. The data indicate that H11/HspB8 overload causes melanoma growth arrest and apoptosis through TAK1 activation and suggest that H11/HspB8 is a promising molecular therapy target.[1]References
- Overload of the heat-shock protein H11/HspB8 triggers melanoma cell apoptosis through activation of transforming growth factor-beta-activated kinase 1. Li, B., Smith, C.C., Laing, J.M., Gober, M.D., Liu, L., Aurelian, L. Oncogene (2007) [Pubmed]
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