Fricke Anna L, Mühlhäuser Wignand W D, Reimann Lena, Zimmermann Johannes P, Reichenbach Christa, Knapp Bettina, Peikert Christian D, Heberle Alexander M, Faessler Erik, Schäuble Sascha, Hahn Udo, Thedieck Kathrin, Radziwill Gerald, Warscheid Bettina
Biochemistry and Functional Proteomics, Institute of Biology II, Faculty of Biology, University of Freiburg, 79104 Freiburg, Germany.
Biochemistry II, Theodor Boveri-Institute, Biocenter, University of Würzburg, 97074 Würzburg, Germany.
J Proteome Res. 2023 Mar 3;22(3):768-789. doi: 10.1021/acs.jproteome.2c00505. Epub 2023 Feb 10.
Phosphorylation-dependent signal transduction plays an important role in regulating the functions and fate of skeletal muscle cells. Central players in the phospho-signaling network are the protein kinases AKT, S6K, and RSK as part of the PI3K-AKT-mTOR-S6K and RAF-MEK-ERK-RSK pathways. However, despite their functional importance, knowledge about their specific targets is incomplete because these kinases share the same basophilic substrate motif RxRxx[ST]. To address this, we performed a multifaceted quantitative phosphoproteomics study of skeletal myotubes following kinase inhibition. Our data corroborate a cross talk between AKT and RAF, a negative feedback loop of RSK on ERK, and a putative connection between RSK and PI3K signaling. Altogether, we report a kinase target landscape containing 49 so far unknown target sites. AKT, S6K, and RSK phosphorylate numerous proteins involved in muscle development, integrity, and functions, and signaling converges on factors that are central for the skeletal muscle cytoskeleton. Whereas AKT controls insulin signaling and impinges on GTPase signaling, nuclear signaling is characteristic for RSK. Our data further support a role of RSK in glucose metabolism. Shared targets have functions in RNA maturation, stability, and translation, which suggests that these basophilic kinases establish an intricate signaling network to orchestrate and regulate processes involved in translation.
磷酸化依赖性信号转导在调节骨骼肌细胞的功能和命运中起着重要作用。磷酸信号网络中的核心成员是蛋白激酶AKT、S6K和RSK，它们是PI3K-AKT-mTOR-S6K和RAF-MEK-ERK-RSK信号通路的一部分。然而，尽管它们具有重要的功能，但关于它们的特定靶点的知识并不完整，因为这些激酶共享相同的嗜碱性底物基序RxRxx[ST]。为了解决这个问题，我们对激酶抑制后的骨骼肌肌管进行了多方面的定量磷酸化蛋白质组学研究。我们的数据证实了AKT和RAF之间的相互作用、RSK对ERK的负反馈环以及RSK和PI3K信号之间的假定联系。总之，我们报告了一个包含49个迄今未知靶点的激酶靶点图谱。AKT、S6K和RSK磷酸化许多参与肌肉发育、完整性和功能的蛋白质，并且信号汇聚于对骨骼肌细胞骨架至关重要的因子。AKT控制胰岛素信号并影响GTPase信号，而核信号是RSK的特征。我们的数据进一步支持了RSK在葡萄糖代谢中的作用。共享靶点在RNA成熟、稳定性和翻译中发挥作用，这表明这些嗜碱性激酶建立了一个复杂的信号网络来协调和调节翻译过程。
