Chen Lixiang, Wang Ting, Wang Yaomei, Zhang Jingxin, Qi Yuanming, Weng Haibo, Kang Qiaozhen, Guo Xinhua, Baines Anthony J, Mohandas Narla, An Xiuli
From the College of Life Science, Zhengzhou University, Science Road 100, Zhengzhou 450001, China, the Red Cell Physiology Laboratory and.
From the College of Life Science, Zhengzhou University, Science Road 100, Zhengzhou 450001, China.
J Biol Chem. 2016 Jan 29;291(5):2170-80. doi: 10.1074/jbc.M115.658591. Epub 2015 Dec 7.
Protein 4.1G is a membrane skeletal protein that can serve as an adapter between transmembrane proteins and the underlying membrane skeleton. The function of 4.1G remains largely unexplored. Here, using 4.1G knockout mouse embryonic fibroblasts (MEFs) as a model system, we explored the function of 4.1G in motile cells. We show that the adhesion, spreading, and migration of 4.1G(-/-) MEF cells are impaired significantly. We further show that, although the total cellular expression of β1 integrin is unchanged, the surface expression of β1 integrin and its active form are decreased significantly in 4.1G(-/-) MEF cells. Moreover, the phosphorylation of focal adhesion kinase, a downstream component of the integrin-mediated signal transduction pathway, is suppressed in 4.1G(-/-) MEF cells. Co-immunoprecipitation experiments and in vitro binding assays showed that 4.1G binds directly to β1 integrin via its membrane-binding domain. These findings identified a novel role of 4.1G in cell adhesion, spreading, and migration in MEF cells by modulating the surface expression of β1 integrin and subsequent downstream signal transduction.
蛋白质4.1G是一种膜骨架蛋白，可作为跨膜蛋白与下层膜骨架之间的衔接子。4.1G的功能在很大程度上仍未得到探索。在此，我们以4.1G基因敲除小鼠胚胎成纤维细胞（MEF）为模型系统，探究了4.1G在运动细胞中的功能。我们发现，4.1G基因敲除的MEF细胞的黏附、铺展和迁移能力均显著受损。我们进一步发现，尽管β1整合素的总细胞表达量未变，但在4.1G基因敲除的MEF细胞中，β1整合素的表面表达及其活性形式均显著降低。此外，在4.1G基因敲除的MEF细胞中，整合素介导的信号转导途径的下游成分——黏着斑激酶的磷酸化受到抑制。免疫共沉淀实验和体外结合试验表明，4.1G通过其膜结合结构域直接与β1整合素结合。这些发现确定了4.1G在MEF细胞的细胞黏附、铺展和迁移中的新作用，即通过调节β1整合素的表面表达及随后的下游信号转导来发挥作用。
