Tyrosine kinase 2 interacts with and phosphorylates receptor for activated C kinase-1, a WD motif-containing protein |
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Authors: | Haro Takashi Shimoda Kazuya Kakumitsu Haruko Kamezaki Kenjirou Numata Akihiko Ishikawa Fumihiko Sekine Yuichi Muromoto Ryuta Matsuda Tadashi Harada Mine |
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Institution: | First Department of Internal Medicine, Faculty of Medicine, and Medicine and Biosystemic Science, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan. |
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Abstract: | Receptor for activated C kinase (Rack)-1 is a protein kinase C-interacting protein, and contains a WD repeat but has no enzymatic activity. In addition to protein kinase C, Rack-1 also binds to Src, phospholipase Cgamma, and ras-GTPase-activating proteins. Thus, Rack-1 is thought to function as a scaffold protein that recruits specific signaling elements. In a cytokine signaling cascade, Rack-1 has been reported to interact with the IFN-alphabeta receptor and Stat1. In addition, we show here that Rack-1 associates with a member of Jak, tyrosine kinase 2 (Tyk2). Rack-1 interacts weakly with the kinase domain and interacts strongly with the pseudokinase domain of Tyk2. Rack-1 associates with Tyk2 via two regions, one in the N terminus and one in the middle portion (aa 138-203) of Rack-1. Jak activation causes the phosphorylation of tyrosine 194 on Rack-1. After phosphorylation, Rack-1 is translocated toward the perinuclear region. In addition to functioning as a scaffolding protein, these results raise the possibility that Rack-1 functions as a signaling molecule in cytokine signaling cascades. |
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