Microdomain abnormalities due to aberrant glycolipids

本课题拟探讨鞘糖脂在肿瘤细胞和神经细胞上表达对生物信号的调控作用，并阐明其异常的发病机制。为了实现这些目标，我们分析了；1. 基于糖基化模式重塑的黑素瘤和小细胞肺癌中脂质信号的调控机制。糖基转移酶基因敲除小鼠异常表型的建立与分析，以阐明糖脂在体内的作用。在黑色素瘤细胞中，GD3的特征性表达诱导了p130Cas和paxillin等接头分子酪氨酸磷酸化的增强，并增加了细胞生长和侵袭活性。此外，GD3+细胞的局灶黏附激酶（FAK）活性也比GD3-细胞强。另一方面，GD2的表达增强了小细胞肺癌细胞的增殖和侵袭能力，与抗GD2抗体结合可触发小细胞肺癌细胞凋亡。然后，证明抗gd2抗体可以诱导FAK的去磷酸化和p38的激活，从而导致anoikis。由此得出结论，抗GD2抗体可触发疾病，必须破坏维持GD2的分子复合体。整合素和FAK作为癌症治疗的有效策略。关于鞘糖脂在神经组织中的作用，基于其高水平的表达，人们一直怀疑酸性鞘糖脂在神经系统的发育和功能中起重要作用。为了明确它们在神经组织中的作用，我们建立了基因敲除小鼠系，即GM2/GD2合成酶敲除小鼠、GD3合成酶敲除小鼠、两者的双敲除小鼠、GM3合成酶敲除小鼠和乳糖神经酰胺合成酶敲除小鼠。作为这些突变小鼠的表型分析结果，我们已经证明它们根据神经节苷脂结构缺陷的范围表现出异常的表型变化。一般来说，酸性糖脂在维持神经组织的完整性和神经元损伤后的修复中似乎是必不可少的。此外，通过对比野生型和双敲除小鼠神经组织的基因表达谱，我们发现突变小鼠的神经退行性改变不仅仅是萎缩性改变，而是伴随炎症过程的活动力改变，这可以通过互补系统的激活和细胞因子的产生或分泌来体现。少

In this project, we have tried to investigate roles of glycosphingolipids expressed on cancer cells and neuronal cells in the regulation of biosignals, and to clarify mechanisms for the pathogenesis due to their abnormalities. In order to achieve these aims, we analysed ; 1. regulatory mechanisms of signaling with glycilipids in melanomas and small cell lung cancers based on the remodeling of glycosylation patterns, 2. establishment and analysis of abnormal phenotypes of gene knockout mice of glycosyltransferases to elucidate roles of glycolipids in vivo. In melanoma cells, characteristic expression of GD3 induced enhancement of tyrosine phosphorylation of adaptor molecules such as p130Cas and paxillin, and increased cell growth and invasion activity. Furthermore, focal adhesion kinase (FAK) was also activated more strongly in GD3+ cells than in GD3- cells. On the other hand, GD2 expression resulted in the enhancement of cell proliferation and invasion in small cell lung cancer cells, … More and binding of anti-GD2 antibodies could trigger apoptosis of small cell lung cancer cells. It was, then, demonstrated that anti-GD2 antibodies could induce dephosphorylation of FAK and activation of p38, leading to anoikis. Consequently, it was concluded that anti-GD2 antibodies trigger anoikis, and it was essential to destroy molecular complex sonsisting of GD2. Integrin and FAK as an efficient strategy toward cancer therapeutics.As for roles of glycosphingolipids in nervous tissues, it has been suspected that acidic glycosphingolipids paly important roles in the development and function of nervous systems based on their high levels of expression. In order to clarify their roles in the nervous tissues, we generated gene knockout mice lines, i. e. knockout mice of GM2/GD2 synthase, GD3 synthase, double knockout of those two, GM3 synthase, and lactosylceramide synthase. As results of phenotypic analyses of these mutant mice, we have demonstrated that they showed abnormal phenotypic changes according to the range of defects in ganglioside structures. Generally, acidic glycolipids appeared to be essential in the maintenance of the integrity of the nervous tissues and repair after neuronal damages. Furthermore, comparison of gene expression profiles in the nerve tissues between wild type and double knockout mice revealed that neurodegeneration detected in the mutant mice are not mere atrophic changes, but active changes with inflammatory process as indicated by the activation of complementary system and cytokine production or secretion. Less