Park Yonghak, Matsumoto Shigeyuki, Ogata Kosuke, Ma Biao, Kanada Ryo, Isaka Yuta, Arichi Norihito, Liang Xiaowen, Maki Ritsuko, Kozasa Tohru, Okuno Yasushi, Ohno Hiroaki, Ishihama Yasushi, Toyoshima Fumiko
Department of Biosystems Science, Institute for Life and Medical Sciences, Kyoto University, Kyoto, Japan; Department of Mammalian and Regulatory Networks, Graduate School of Biostudies, Kyoto University, Kyoto, Japan.
Department of Biomedical Data Intelligence, Graduate School of Medicine, Kyoto University, Kyoto, Japan.
J Biol Chem. 2025 Feb;301(2):108136. doi: 10.1016/j.jbc.2024.108136. Epub 2024 Dec 25.
Alpha-1-antitrypsin (AAT), a circulating serine protease inhibitor, is an acute inflammatory response protein with anti-inflammatory functions. The C-terminal peptides of AAT are found in various tissues and have been proposed as putative bioactive peptides with multiple functions, but its mechanism of action remains unclear. We previously reported that a mouse AAT C-terminal peptide of 35 amino acids (mAAT-C) penetrates plasma membrane and associates guanine nucleotide-binding protein subunit alpha 13 (Gα13). Here, we show that mAAT-C binds directly to the guanosine diphosphate (GDP)-bound form of Gα13 through the N-terminal region (mAAT-C), thereby facilitating the interaction of Gα13・GDP with its effector proteins. The minimal sequence (mAAT-C) and essential amino acid residue (Phe11) of mAAT-C were identified as being necessary for this effect. A molecular dynamics simulation for the Gα13・GDP-mAAT-C complex model showed that binding of mAAT-C to the region surrounded by switch regions of Gα13 stabilizes the flexible switch II and III regions, thereby maintaining their active conformation. In addition, mAAT-C activates the Gα13 signaling pathway in cells where Phe11 is required. Our study reveals the structure-based mechanism of action of AAT-C peptides in the regulation of Gα13 and demonstrates that AAT-C peptides represent a biological peptide capable of activating G protein signals in a manner that is independent of G-protein-coupled receptors.
α-1-抗胰蛋白酶（AAT）是一种循环丝氨酸蛋白酶抑制剂，是一种具有抗炎功能的急性炎症反应蛋白。AAT的C末端肽存在于各种组织中，并被认为是具有多种功能的假定生物活性肽，但其作用机制仍不清楚。我们之前报道过，一种由35个氨基酸组成的小鼠AAT C末端肽（mAAT-C）可穿透质膜并与鸟嘌呤核苷酸结合蛋白亚基α13（Gα13）结合。在此，我们表明mAAT-C通过其N末端区域（mAAT-C）直接与结合鸟苷二磷酸（GDP）的Gα13形式结合，从而促进Gα13·GDP与其效应蛋白的相互作用。确定了mAAT-C的最小序列（mAAT-C）和必需氨基酸残基（Phe11）对这种效应是必需的。对Gα13·GDP-mAAT-C复合模型的分子动力学模拟表明，mAAT-C与Gα13开关区域包围的区域结合可稳定灵活的开关II和III区域，从而维持它们的活性构象。此外，mAAT-C在需要Phe11的细胞中激活Gα13信号通路。我们的研究揭示了AAT-C肽在调节Gα13中基于结构的作用机制，并证明AAT-C肽代表一种能够以独立于G蛋白偶联受体的方式激活G蛋白信号的生物肽。
