Devi Shamulailatpam Shreedarshanee, Yadav Rashmi, Arya Ranjana
School of Biotechnology, Jawaharlal Nehru University, New Delhi, India.
Front Cell Dev Biol. 2021 Mar 18;9:603742. doi: 10.3389/fcell.2021.603742. eCollection 2021.
Cell migration is an essential cellular process that requires coordination of cytoskeletal dynamics, reorganization, and signal transduction. The actin cytoskeleton is central in maintaining the cellular structure as well as regulating the mechanisms of cell motility. Glycosylation, particularly sialylation of cell surface proteins like integrins, regulates signal transduction from the extracellular matrix to the cytoskeletal network. The activation of integrin by extracellular cues leads to recruitment of different focal adhesion complex proteins (Src, FAK, paxillin, etc.) and activates the signal including Rho GTPases for the regulation of actin assembly and disassembly. During cell migration, the assembly and disassembly of actin filament provides the essential force for the cell to move. Abnormal sialylation can lead to actin signaling dysfunction leading to aberrant cell migration, one of the main characteristics of cancer and myopathies. In the present study, we have reported altered F-actin to G-actin ratios in GNE mutated cells. These cells exhibit pathologically relevant mutations of GNE (UDP N-acetylneuraminic 2-epimerase/N-acetylmannosamine kinase), a key sialic acid biosynthetic enzyme. It was found that GNE neither affects the actin polymerization nor binds directly to actin. However, mutation in GNE resulted in increased binding of α-actinin to actin filaments. Further, through confocal imaging, GNE was found to be localized in focal adhesion complex along with paxillin. We further elucidated that mutation in GNE resulted in upregulation of RhoA protein and Cofilin activity is downregulated, which could be rescued with Rhosin and chlorogenic acid, respectively. Lastly, mutant in GNE reduced cell migration as implicated from wound healing assay. Our study indicates that molecules altering Cofilin function could significantly revert the cell migration defect due to GNE mutation in sialic acid-deficient cells. We propose cytoskeletal proteins to be alternate drug targets for disorders associated with GNE such as GNE myopathy.
细胞迁移是一个重要的细胞过程，需要细胞骨架动力学、重组和信号转导的协调。肌动蛋白细胞骨架在维持细胞结构以及调节细胞运动机制方面起着核心作用。糖基化，特别是整合素等细胞表面蛋白的唾液酸化，调节从细胞外基质到细胞骨架网络的信号转导。细胞外信号激活整合素会导致不同的粘着斑复合物蛋白（Src、FAK、桩蛋白等）的募集，并激活包括Rho GTPases在内的信号，以调节肌动蛋白的组装和拆卸。在细胞迁移过程中，肌动蛋白丝的组装和拆卸为细胞移动提供了必要的力量。异常的唾液酸化可导致肌动蛋白信号功能障碍，从而导致异常的细胞迁移，这是癌症和肌病的主要特征之一。在本研究中，我们报道了GNE突变细胞中F-肌动蛋白与G-肌动蛋白比例的改变。这些细胞表现出GNE（UDP-N-乙酰神经氨酸2-表异构酶/N-乙酰甘露糖胺激酶）的病理相关突变，GNE是一种关键的唾液酸生物合成酶。研究发现，GNE既不影响肌动蛋白的聚合，也不直接与肌动蛋白结合。然而，GNE突变导致α-辅肌动蛋白与肌动蛋白丝的结合增加。此外，通过共聚焦成像发现，GNE与桩蛋白一起定位于粘着斑复合物中。我们进一步阐明，GNE突变导致RhoA蛋白上调，而丝切蛋白活性下调，分别用Rhosin和绿原酸可以挽救这种情况。最后，如伤口愈合试验所示，GNE突变体减少了细胞迁移。我们的研究表明，改变丝切蛋白功能的分子可以显著逆转唾液酸缺乏细胞中由于GNE突变导致的细胞迁移缺陷。我们提出细胞骨架蛋白可作为与GNE相关疾病（如GNE肌病）的替代药物靶点。
