Cao Jinjing, Aichem Annette, Basler Michael, Alvarez Salinas Gerardo Omar, Schmidtke Gunter
Division of Immunology, Department of Biology, University of Konstanz, 78457 Konstanz, Germany.
Institute of Cell Biology and Immunology Thurgau (BITg), University of Konstanz, 8280 Kreuzlingen, Switzerland.
Biomedicines. 2024 Dec 9;12(12):2795. doi: 10.3390/biomedicines12122795.
: FAT10 is a member of the ubiquitin-like modifier family. Similar to ubiquitin, FAT10 has a distinct enzyme cascade consisting of E1-activating, E2-conjugating, and possibly several E3-ligating enzymes, which will covalently link FAT10 to substrate proteins in order to target them directly for proteasomal degradation. FAT10 was reported to be phosphorylated by IKKβ during infection with influenza A virus. : To assess the difference between the FAT10-dependent degradation of phosphorylated FAT10 and the non-phosphorylated FAT10 wild type (FAT10 WT), a mutated FAT10 that mimicked phosphorylation (FAT10 D) was constructed by replacing several serine residues and one threonine residue with aspartic or glutamic acid. The FAT10 degradation or conjugation was compared between the phospho-mimetic FAT10 and the wild-type FAT10 with respect to the dependence of the E3 ligase TRIM25, the UBL-UBA protein NUB1L, and the proteasomal ubiquitin receptor RPN10. : The phospho-mimetic FAT10 was more efficiently conjugated to substrate proteins as compared to the wild-type FAT10, particularly if TRIM25 was co-expressed. Additionally, the phospho-mimetic FAT10 was not bound by NUB1L. However, this did not affect FAT10 D or FAT10 WT degradation. No differences were found in the binding affinity of phospho-mimetic FAT10 to RPN10. : In brief, the phospho-mimetic FAT10 shows enhanced conjugation efficiency, but phosphorylation does not alter its degradation by the proteasome. This reveals that phosphorylation may fine-tune FAT10's interactions with specific interaction partners without disrupting its core function of proteasomal degradation.
FAT10是类泛素修饰因子家族的一员。与泛素相似，FAT10具有由E1激活酶、E2缀合酶以及可能的几种E3连接酶组成的独特酶级联反应，这些酶会将FAT10共价连接到底物蛋白上，以便将它们直接靶向蛋白酶体降解。据报道，在甲型流感病毒感染期间，FAT10会被IKKβ磷酸化。
为了评估磷酸化FAT10和非磷酸化FAT10野生型（FAT10 WT）在FAT10依赖性降解方面的差异，通过将几个丝氨酸残基和一个苏氨酸残基替换为天冬氨酸或谷氨酸，构建了模拟磷酸化的突变型FAT10（FAT10 D）。就E3连接酶TRIM25、UBL-UBA蛋白NUB1L和蛋白酶体泛素受体RPN10而言，比较了模拟磷酸化FAT10和野生型FAT10之间的FAT10降解或缀合情况。
与野生型FAT10相比，模拟磷酸化FAT10与底物蛋白的缀合效率更高，特别是在共表达TRIM25时。此外，模拟磷酸化FAT10不与NUB1L结合。然而，这并不影响FAT10 D或FAT10 WT的降解。模拟磷酸化FAT10与RPN10的结合亲和力未发现差异。
简而言之，模拟磷酸化FAT10显示出更高的缀合效率，但磷酸化不会改变其被蛋白酶体降解的情况。这表明磷酸化可能会微调FAT10与特定相互作用伙伴的相互作用，而不会破坏其蛋白酶体降解的核心功能。
