Exp Hematol. 2007 Dec;35(12):1812-22. Epub 2007 Oct 17.

Constitutive association of MyD88 to IRAK in HTLV-I-transformed T cells.External

Mizobe, T., Tsukada, J., Higashi, T., Mouri, F., Matsuura, A., Tanikawa, R., Minami, Y., Yoshida, Y., Tanaka, Y.,
--- - The First Department of Internal Medicine, School of Medicine, University of Occupational and Environmental Health, Kitakyushu, Japan.
OBJECTIVE: Constitutive activation of nuclear factor (NF)-kappaB is a common feature of human T-cell leukemia virus type I (HTLV-I)-transformed T cells. Inhibition of NF-kappaB activity reduces cell growth and induces apoptosis of HTLV-I-transformed T cells, suggesting a central role of NF-kappaB in their proliferation and survival. In this study, we investigated whether MyD88, an adaptor protein of Toll-like receptor (TLR) signaling, contributes to constitutive NF-kappaB activation in HTLV-I-transformed T cells. MATERIALS AND METHODS: Activation status of MyD88 and interleukin (IL)-1R-associated kinase 1 (IRAK1) in HTLV-I-transformed human T cells, MT2, MT4, and HUT102 was examined by using Western blot and immunoprecipitation. TLR expression was evaluated with reverse transcription polymerase chain reaction. An expression vector encoding a dominant negative MyD88 with a deletion of its death domain (MyD88dn) was transfected into MT2 cells to evaluate roles of MyD88 in spontaneous activation of cytokine gene promoters and transcription factors, proliferation, and apoptosis in HTLV-I-transformed T cells. RESULTS: Constitutive association of MyD88 with IRAK1 was observed in all three of HTLV-I-transformed T cells, but not in HTLV-I-negative T cells, such as Jurkat, HUT78, and MOLT4. MT2 cells showed expression of TLR-1, -6, and -10 mRNAs. Constitutive activation of NF-kappaB and NF-IL-6 and cytokine gene promoters, such as IL-1alpha, interferon-gamma, and tumor necrosis factor-alpha in MT2 cells was inhibited by MyD88dn expression. MyD88dn reduced proliferation and induced apoptosis of MT2 cells. HTLV-I Tax enhanced TLR expression and synergistically activated NF-kappaB with wild-type MyD88. CONCLUSION: Our results show a novel pathway in NF-kappaB activation in HTLV-I-transformed T cells and further demonstrate a critical role of MyD88 in their dysregulated gene activation, survival, and proliferation.
PMID: 17920759External
Arrow2 In vitro interaction Arrow2 In vivo interaction Arrow2 Characterization Arrow2 Functional role Arrow2 top
In vivo interaction
  Endogenous
expression
Overexpression DD1 DD2 Reference
Family DD1 DD2 Method Species Region Species Region
DD IRAK1 Link Myd88 Co-immunoprecipitation MT2 17920759
DD IRAK1 Link Myd88 Co-immunoprecipitation HUT102 17920759
DD IRAK1 Link Myd88 Co-immunoprecipitation MT4 17920759
(Link: click this icon to show interactions only between the two corresponding DDs)