Department of Biochemistry and Molecular Cell Biology, Shanghai Key Laboratory for Tumor Microenvironment and Inflammation, Shanghai Jiao Tong University School of Medicine, Shanghai, 200025, China.
Department of Integrative Biology and Pharmacology, McGovern Medical School, The University of Texas Health Science Center at Houston, Houston, TX, 77030, USA.
Nat Commun. 2023 Sep 14;14(1):5688. doi: 10.1038/s41467-023-41520-2.
Small ubiquitin-like modifier (SUMO) typically conjugates to target proteins through isopeptide linkage to the ε-amino group of lysine residues. This posttranslational modification (PTM) plays pivotal roles in modulating protein function. Cofilins are key regulators of actin cytoskeleton dynamics and are well-known to undergo several different PTMs. Here, we show that cofilin-1 is conjugated by SUMO1 both in vitro and in vivo. Using mass spectrometry and biochemical and genetic approaches, we identify the N-terminal α-amino group as the SUMO-conjugation site of cofilin-1. Common to conventional SUMOylation is that the N-α-SUMOylation of cofilin-1 is also mediated by SUMO activating (E1), conjugating (E2), and ligating (E3) enzymes and reversed by the SUMO deconjugating enzyme, SENP1. Specific to the N-α-SUMOylation is the physical association of the E1 enzyme to the substrate, cofilin-1. Using F-actin co-sedimentation and actin depolymerization assays in vitro and fluorescence staining of actin filaments in cells, we show that the N-α-SUMOylation promotes cofilin-1 binding to F-actin and cofilin-induced actin depolymerization. This covalent conjugation by SUMO at the N-α amino group of cofilin-1, rather than at an internal lysine(s), serves as an essential PTM to tune cofilin-1 function during regulation of actin dynamics.
小泛素样修饰物（SUMO）通常通过与赖氨酸残基的ε-氨基之间的异肽键连接到靶蛋白上。这种翻译后修饰（PTM）在调节蛋白质功能方面起着关键作用。丝切蛋白是肌动蛋白细胞骨架动力学的关键调节剂，并且已知其经历多种不同的 PTM。在这里，我们表明丝切蛋白-1在体外和体内都被 SUMO1 共轭。使用质谱和生化及遗传方法，我们确定了丝切蛋白-1的 N 端α-氨基是 SUMO 共轭的位点。与传统的 SUMOylation 相同的是，丝切蛋白-1的 N-α-SUMOylation 也是由 SUMO 激活酶（E1）、连接酶（E2）和连接酶（E3）介导，并由 SUMO 去共轭酶 SENP1 逆转。N-α-SUMOylation 特异性在于 E1 酶与底物丝切蛋白-1的物理结合。通过体外 F-肌动蛋白共沉淀和肌动蛋白解聚测定以及细胞中肌动蛋白丝的荧光染色，我们表明 N-α-SUMOylation 促进丝切蛋白-1与 F-肌动蛋白的结合以及丝切蛋白诱导的肌动蛋白解聚。这种通过 SUMO 在丝切蛋白-1的 N-α 氨基上的共价结合，而不是在内部赖氨酸上的结合，作为一种重要的 PTM，可调节肌动蛋白动力学调节中丝切蛋白-1的功能。
