Tax1 Enhances Cancer Cell Proliferation via Ras-Raf-MEK-ERK Signaling Pathway

Erbin is an ErbB2 binding protein, which belongs to the LAP (leucine-rich repeat (LRR) and PDZ domain) protein family. We previously, reported that Tax1, a protein of the human T-cell leukemia virus type I (HTLV-1), associated with Erbin by using Erbin PDZ domain as a bait to screen a human T lymphocyte cDNA library by a yeast two hybrid strategy. In the present study, we demonstrated that Tax1 enhances cancer cell proliferation via Ras-Raf-MEK-ERK signaling pathway by Using molecular section strategy. The pull-down assay showed that the four amino acid domain, that is, Tax1 350-353, might specifically interact with Erbin, but not any other Tax1 deletion mutants. The communoprecipitation assay confirmed that Tax1 350-353 domain bound with Erbin in vivo. Functional study demonstrated that overexpresssion of Tax1 in cancer cell lines of liver cancer SMMC-7721, colon cancer HCT-116, and breast cancer MCF-7 facilitated the cell proliferation. And the transfection of Tax1 353 in MCF-7 cells with endogenous Erbin expression markedly increased phosphorylation of Ras, Raf, MEK1/2, ERK1/2, PI3K, and suggesting that Tax1-enhanced cell proliferation tracks Ras-Raf-MEK-ERK signaling pathway. (C) 2009 IUBMB IUBMB Life, 61(6): 685-692, 2009