title: Molecular dynamics of STAT3 on IL-6 signaling pathway in living cells.
abstract: Signal transducer and activator of transcription 3 (STAT3) is a critical signal transducer of interleukin-6 (IL-6) signaling. To investigate the mobility and the dynamics of STAT3 complex on IL-6 signaling in living cells, we generated a chimeric gene consisting of STAT3 fused to enhanced green fluorescence protein, STAT3-GFP. STAT3-GFP was expressed in Hep3B cells and the dynamics of this protein were analyzed by fluorescence correlation spectroscopy. After IL-6 stimulation, STAT3 translocated from the cytoplasm to the nucleus, as shown previously. According to the analysis of STAT3 diffusion in stable transformants, the number of STAT3 molecules at the cytoplasmic membrane and in the cytoplasm decreased after IL-6 stimulation. In the nucleus, the diffusion speed of STAT3 complex strongly decreased after IL-6 stimulation. Furthermore, we found that STAT3 existed as a complex whose molecular weight was less than 400kDa before IL-6 addition. However, IL-6 stimulation induced the formation of STAT3 dimer as a megacomplex form whose molecular weight was more than 1MDa at the cytoplasm and a very slow diffusion complex in the nucleus.
authors.affiliation: Division of Molecular Immunology, Institute for Genetic Medicine, Hokkaido University, N15 W7, Kita-ku, Sapporo 060-0815, Japan.
authors.forename: Kenji
authors.initials: K
authors.lastname: Watanabe
authors.forename: Kenta
authors.initials: K
authors.lastname: Saito
authors.forename: Masataka
authors.initials: M
authors.lastname: Kinjo
authors.forename: Tadashi
authors.initials: T
authors.lastname: Matsuda
authors.forename: Mamoru
authors.initials: M
authors.lastname: Tamura
authors.forename: Shigeyuki
authors.initials: S
authors.lastname: Kon
authors.forename: Tadaaki
authors.initials: T
authors.lastname: Miyazaki
authors.forename: Toshimitsu
authors.initials: T
authors.lastname: Uede
mesh_terms: D045744:Cell Line, Tumor; D004268:DNA-Binding Proteins / Q000032:analysis*; D004058:Diffusion; D049452:Green Fluorescent Proteins / Q000032:analysis / Q000737:chemistry; D006801:Humans; D015850:Interleukin-6 / Q000494:pharmacology*; D007700:Kinetics; D018613:Microscopy, Confocal; D050796:STAT3 Transcription Factor; D015398:Signal Transduction; D013050:Spectrometry, Fluorescence; D015534:Trans-Activators / Q000032:analysis*
chemical_list: D004268:DNA-Binding Proteins; D015850:Interleukin-6; D050796:STAT3 Transcription Factor; C494086:STAT3 protein, human; D015534:Trans-Activators; D049452:Green Fluorescent Proteins