Smad inhibition by the Ste20 kinase Misshapen

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 108; no. 27; pp. 11127 - 11132
• Main Authors: Kaneko, Satoshi, Chen, Xiaochu, Lu, Peiyuan, Yao, Xiaohao, Wright, Theodore G, Rajurkar, Mihir, Kariya, Ken-ichi, Mao, Junhao, Ip, Y. Tony, Xu, Lan
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences 05-07-2011; National Acad Sciences
• Subjects: Amino Acid Sequence; Animals; Animals, Genetically Modified; Antibodies; Binding Sites; bioactive properties; Biological Sciences; Bone Morphogenetic Protein Receptors - metabolism; Bone Morphogenetic Proteins - metabolism; Cell culture techniques; Cell Line; Cell lines; DNA-Binding Proteins - antagonists & inhibitors; DNA-Binding Proteins - genetics; DNA-Binding Proteins - metabolism; Drosophila; Drosophila melanogaster - genetics; Drosophila melanogaster - growth & development; Drosophila melanogaster - metabolism; Drosophila Proteins - antagonists & inhibitors; Drosophila Proteins - deficiency; Drosophila Proteins - genetics; Drosophila Proteins - metabolism; Epithelial cells; Gene expression regulation; genes; Genes, Insect; genetically modified organisms; Homeostasis; Humans; Insects; Kinases; mammals; Mass spectroscopy; mitogen-activated protein kinase; mitogen-activated protein kinase kinase kinase; Molecular Sequence Data; Phosphorylation; Protein Structure, Secondary; Protein-Serine-Threonine Kinases - antagonists & inhibitors; Protein-Serine-Threonine Kinases - deficiency; Protein-Serine-Threonine Kinases - genetics; Protein-Serine-Threonine Kinases - metabolism; Receptors; RNA Interference; screening; Sequence Homology, Amino Acid; Signal Transduction; Smad Proteins - antagonists & inhibitors; Smad Proteins - chemistry; Smad Proteins - genetics; Smad Proteins - metabolism; Small interfering RNA; tissue culture; Transcription Factors - antagonists & inhibitors; Transcription Factors - genetics; Transcription Factors - metabolism; Transforming Growth Factor beta - metabolism
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.1104128108

The level of TGF-β/bone morphogenetic protein (BMP) signaling through Smad is tightly regulated to ensure proper embryonic patterning and homeostasis. Here we show that Smad activation by TGF-β/BMP is blocked by a highly conserved phosphorylation event in the α-helix 1 region of Smad [T312 in Drosophila Smad1 (MAD)]. α-helix 1 phosphorylation reduces Smad interaction with TGF-β/BMP receptor kinase and affects all receptor-activated Smads except Smad3. Tissue culture and transgenic studies in Drosophila further demonstrate that the biological activity of MAD is repressed by T312 phosphorylation in vivo. Through RNAi screening of the kinome, we have identified Misshapen (Msn) and the mammalian orthologs TNIK, MINK1, and MAP4K4 as the kinases responsible for α-helix 1 phosphorylation. Targeted expression of an active form of Msn in the wing imaginal disk disrupted activation of endogenous MAD by Dpp and expression of the Dpp/MAD target gene. Msn kinases belong to the Ste20 kinase family that has been shown to act as MAP kinase kinase kinase kinase (MAP4K). Our findings thus reveal a function of Msn independent of its impact on MAP kinase cascades. This Smad inhibition mechanism by Msn likely has important implications for development and disease.