NMMHCⅡA介导HMGA1促进GSK-3β泛素化降解进而诱导胶质瘤细胞干性

NMMHCⅡA promoted glioma cell EMT and stemness, and GSK-3β was probably interacting protein of NMMHCⅡA detected by Co-IP. Considering multiple ubiquitin locus of GSK-3β predicted by bioinformatics analysis and the ubiquitination of GSK-3β promoted nuclear translocation of β-catenin demonstrated by previous studies, we hypothesized NMMHCⅡA induced glioma cell stemness by promoting ubiquitination of GSK-3β and nuclear translocation of β-catenin. Besides, early investigation found HMGA1 promoted glioma cell stemness, knocking down expression of HMGA1 inactivated PI3K/Akt/c-Jun pathway and inhibited the expression of NMMHCⅡA. Further bioinformatics prediction indicated that binding sites of c-Jun existed in the promoter region of NMMHCⅡA. Thus, we also presumed NMMHCⅡA could be regulated by HMGA1/PI3K/Akt/c-Jun directly. Subsequent study mainly focused on the regulating relationship between NMMHCⅡA, GSK-3β and HMGA1. These findings will provide a new sight for clarifying the molecular mechanism of glioma stemness.

前期研究发现NMMHCⅡA（MHA）促进胶质瘤细胞EMT及干性，同时GSK-3β可能是其相互作用蛋白，干扰MHA表达能促进GSK-3β的蛋白表达而不影响其mRNA表达。生物信息学分析显示GSK-3β存在多个泛素化修饰位点，同时文献报道GSK-3β泛素化能促进β-catenin入核，据此推测MHA在胶质瘤中与GSK-3β相互作用并促进其泛素化降解，进一步诱导β-catenin入核从而促进细胞的EMT和干性。此外课题组早期研究发现HMGA1调控胶质瘤干性，干扰其表达后抑制PI3K/Akt/c-Jun通路和MHA的表达。进一步生物信息学预测显示MHA启动子存在c-Jun结合位点，因此推测MHA在胶质瘤中又可被HMGA1/PI3K/Akt/c-Jun靶向调控。随后的工作主要围绕MHA、GSK-3β和HMGA1三者的调控关系展开。若本课题顺利开展，将为阐明胶质瘤干性的分子机制提供一个新的思路。

HMGA1和MYH9在胶质瘤中高表达，并与肿瘤的WHO分级呈正相关。同时，HMGA1和MYH9在胶质瘤中的表达高低与患者总生存时间成负相关，即表达低的患者总生存时间更长，而高表达HMGA1和MYH9的胶质瘤患者总生存时间较短。细胞功能学实验表明，HMGA1在胶质瘤中促进细胞的增殖、侵袭和迁移能力，并能维持细胞的干性和化疗抵抗。进一步探索发现HMGA1可以通过PI3K/Akt/c-Jun通路影响MYH9和GSK-3β的表达。生物信息学分析提示，MYH9上游的启动子区域存在c-Jun的潜在结合位点，而随后的机制研究证实转录因子c-Jun与MYH9基因的启动子区域并促进MYH9蛋白的表达。细胞功能回复实验也证实HMGA1可以通过MYH9增强胶质瘤细胞的恶性表型和化疗抵抗能力。而对MYH9的进一步机制研究表明，MYH9能与GSK-3β蛋白相互作用，通过影响其27K泛素化位点，进而促进GSK-3β蛋白的泛素化降解，从而发挥增强胶质瘤细胞的恶性表型和化疗抵抗能力的作用。通过本研究的开展，为阐明胶质瘤发生及发展的分子机制提供一个新的思路，同时为肿瘤的诊治、预后及药物筛选提供了一个潜在的新靶点。

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