|Budget Amount *help
¥2,200,000 (Direct Cost: ¥2,200,000)
Fiscal Year 1997: ¥2,200,000 (Direct Cost: ¥2,200,000)
1. We have elucidated the roles of each signaling pathways of IL-6 in a variety of cells using a series of gp130 mutant receptors and dominant-negative STA T3. The points made clear are as follows. 1) STA T3 activity is critical in IL-6-induced growth arrest and macrophage differentiation of M1 leukemic cells. STA T3 is involved in both repression of c-myc and c-myb expression and activation of junB and IRF1.2) For proliferative signals, both STA T3-mediated signals and another signals derived from the second tyrosine residue of gp130 are required in BAF/B03 cells. Especially, STA T3 provides anti-apoptotic signals. 3) In collaboration with us, Drs.Fukui and Ihara showed that Ras/MAP kinase pathway is critical in IL-6 induced neutrite outgrowth of PC12 cells which had been pretreated with NGF for 2h. Importantly, STA T3 has a negative effect on the neurite inducing activity. Consistently with this, NGF pretreatment was found to attenuate the subsequent STA T3 activation by IL-6.
2. We showed that the carboxi-terminal region of STA T5 can bind to the kinase-like domain of JAK kinases and presented a model, where JAK kinases activated by IL-6 directly phosphorylate and activate STA T5 without using phsophorylated tyrosine residues of the gp130.
3. We identified two other target genes for STA T3 in M1 cells. Both the p19^<INK4D> gene, a CDK inhibitor, and the stat3 gene itself are activated by STA T3. We further showed that STA T3 rapidly induced transcriptional activation of the stat3 gene through an IL-6 response element, located at -335/-314 in the stat3 gene promoter, which consists of a low-affinity STA T binding element and a CRE.Complex formation containing a STA T3 homo-dimer and an unidentified CRE-binding protein are required for full response. The autoregulatory loop is likely to be involved in the sustained activation of STA T3 observed in IL-6-stimulated M1 cells.