Differential requirements for JAK2 and TYK2 in T cell proliferation and IFN-γ production induced by IL-12 alone or together with IL-18
✍ Scribed by Naotoshi Sugimoto; Masakiyo Nakahira; Hyun-Jong Ahn; Mark Micallef; Toshiyuki Hamaoka; Masashi Kurimoto; Hiromi Fujiwara
- Publisher
- John Wiley and Sons
- Year
- 2003
- Tongue
- English
- Weight
- 253 KB
- Volume
- 33
- Category
- Article
- ISSN
- 0014-2980
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✦ Synopsis
IL-12 activates TYK2 and Janus kinase (JAK)-2 to induce the phosphorylation of various signal transducers and activators of transcription (STAT) proteins. However, little is known regarding how these JAK exhibit the distinct biological effects of IL-12. Using two JAK inhibitors, tyrphostin A1 (A1) for TYK2 and tyrphostin B42 (B42) for JAK2, we investigated the involvement of JAK2 and TYK2 in IL-12-induced T cell proliferation and IFN-gamma production. B42, but not A1, inhibited T cell proliferation along with down-regulation of IL-12-induced c-Myc expression and STAT5 phosphorylation. In contrast, A1 but not B42 inhibited STAT4/STAT3 phosphorylation and IFN-gamma production. IL-18, but not IL-12, induced activator protein-1 (AP-1) responsible for high levels of IFN-gamma promoter activation. However, this IL-18 effect depended on the interaction of AP-1 with STAT4. A1 prevented AP-1 binding by inhibiting STAT4 involvement and down-regulated synergistic IFN-gamma promoter activation. These results indicate that JAK2 activation is required for IL-12-mediated T cell growth, whereas the TYK2-STAT4 signaling pathway is critical for IFN-gamma expression that is mediated by IL-12 alone and enhanced synergistically by combination with IL-18.