MAPK upstream kinase (MUK)-binding inhibitory protein, a negative regulator of MUK/dual leucine zipper-bearing kinase/leucine zipper protein kinase |
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Authors: | Fukuyama K Yoshida M Yamashita A Deyama T Baba M Suzuki A Mohri H Ikezawa Z Nakajima H Hirai S Ohno S |
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Institution: | Departments of Dermatology, 1st Internal Medicine, Molecular Biology, and Urology, Yokohama City University School of Medicine, 3-9, Fukuura, Kanazawa-ku, Yokohama 236-0004, Japan. |
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Abstract: | Mitogen-activated protein kinase upstream kinase/dual leucine zipper-bearing kinase/leucine-zipper protein kinase (MUK/DLK/ZPK) is a MAPKKK class protein kinase that induces JNK/SAPK activation. We report here a protein named MBIP that binds to MUK/DLK/ZPK. MUK-binding inhibitory protein (MBIP) contains two tandemly orientated leucine-zipper-like motifs with a cluster of basic amino acids located between the two motifs. MBIP interacts with one of the two leucine-zipper-like motifs of MUK/DLK/ZPK and inhibits the activity of MUK/DLK/ZPK to induce JNK/SAPK activation. Notably, no similar effect was observed with another JNK/SAPK-inducing MAPKKK, COT/Tpl-2, showing the specificity of MBIP action. Furthermore, the overexpression of MBIP partially inhibits the activation of JNK by 0.3 m sorbitol in 293T cells. Taken together, these observations indicate that MBIP can function as a regulator of MUK/DLK/ZPK, a finding that may provide a clue to understanding the molecular mechanism of JNK/SAPK activation by hyperosmotic stress. |
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