Vascular Biology Center, Medical College of Georgia, Augusta University, Augusta, GA 30912, USA.
Division of Cardiology, Department of Medicine, Medical College of Georgia, Augusta University, Augusta, GA 30912, USA.
Cells. 2023 Jul 25;12(15):1923. doi: 10.3390/cells12151923.
Protein modification by ubiquitin fold modifier 1 (UFM1), termed ufmylation, regulates various physiological and pathological processes. Among emerging UFM1 targets, UFM1 binding protein 1 (UFBP1) is the first identified ufmylation substrate. Recent clinical and animal studies have demonstrated the pivotal roles of UFBP1 in development, hematopoiesis, intestinal homeostasis, chondrogenesis, and neuronal development, which has been linked to its function in maintaining endoplasmic reticulum (ER) homeostasis. However, the importance of UFBP1 ufmylation in these cellular and physiological processes has yet to be determined. It has been proposed that ufmylation of lysine 268 (267 in ) in UFBP1 plays a critical role in mediating the effects of the ufmylation pathway. In this study, we for the first time probe the pathophysiological significance of UFBP1 ufmylation in vivo by creating and characterizing a UFBP1 knockin (KI) model in which the lysine 268 of UFBP1, the amino acid accepting UFM1, was mutated to arginine. Our results showed that the K268R mutation reduced the total ufmylated proteins without altering the expression levels of individual ufmylation enzymes in mouse embryonic fibroblasts. The K268R mutation did not alter ER stress-stimuli-induced ER stress signaling or cell death in mouse embryonic fibroblasts. The homozygous KI mice were viable and morphologically indistinguishable from their littermate wild-type controls up to one year of age. Serial echocardiography revealed no cardiac functional impairment of the homozygous KI mice. Furthermore, the homozygous KI mice exhibited the same susceptibility to dextran sulfate sodium (DSS) -induced colitis as wild-type mice. Taken together, these results suggest that UFBP1 K268 is dispensable for ER stress response, embryonic development, cardiac homeostasis under physiological conditions, and intestinal homeostasis under pathological conditions. Our studies call for future investigations to understand the biological function of UFBP1 ufmylation and offer a new mouse model to determine the roles of UFBP1 ufmylation in different tissues under stress conditions.
泛素样修饰蛋白 1（UFM1）对蛋白质的修饰作用，即 UFM1 化，可调节多种生理和病理过程。在新兴的 UFM1 靶标中，UFM1 结合蛋白 1（UFBP1）是第一个被鉴定的 UFM1 化底物。最近的临床和动物研究表明，UFBP1 在发育、造血、肠道稳态、软骨生成和神经元发育中具有关键作用，这与其在维持内质网（ER）稳态中的功能有关。然而，UFBP1 UFM1 化在这些细胞和生理过程中的重要性仍有待确定。有人提出，UFBP1 赖氨酸 268（ 中的 267）的 UFM1 化在介导 UFM1 化途径的作用中起着关键作用。在这项研究中，我们首次通过创建和表征 UFBP1 敲入（KI）模型，在体内探测 UFBP1 UFM1 化的病理生理意义，该模型中 UFBP1 的赖氨酸 268，即接受 UFM1 的氨基酸，突变为精氨酸。我们的结果表明，K268R 突变降低了总 UFM1 化蛋白，而不改变小鼠胚胎成纤维细胞中单个 UFM1 化酶的表达水平。K268R 突变并未改变 ER 应激刺激诱导的 ER 应激信号或细胞死亡。纯合子 KI 小鼠在 1 岁之前在存活和形态上与同窝野生型对照没有区别。连续超声心动图显示纯合子 KI 小鼠没有心脏功能障碍。此外，纯合子 KI 小鼠对葡聚糖硫酸钠（DSS）诱导的结肠炎的敏感性与野生型小鼠相同。总之，这些结果表明，UFBP1 K268 对于 ER 应激反应、胚胎发育、生理条件下的心脏稳态以及病理条件下的肠道稳态是可有可无的。我们的研究呼吁未来进行研究以了解 UFBP1 UFM1 化的生物学功能，并提供一种新的小鼠模型来确定 UFBP1 UFM1 化在应激条件下不同组织中的作用。
