CK2在lamin A-缺陷所致早老症中作用机制的研究

Hutchinson-Gilford progeria syndrome (HGPS) and Restrictive dermopathy (RD)are two laminopathies caused by mutations leading to celluar accumulation of prelamin A or one of its truncated forms, progerin, which induces misshapen nuclei, heterochromatin disorganization, genomic instability and premature aging. Our previous study showed that the compromised HP1α phosphorylation at Thr50 site mediates the defective heterochromatin DNA damage response and accelerated senescence in progeriod cells. Based on CK2 (casine kinase 2) is specially phosphorylation of HP1α at Thr50 site, the aim of this study is to investigate the effects of prelamin A/progerin on CK2 homeostasis and enzyme activity in mouse embryonic fibroblasts (MEFs) derived from Zmpste24-dificient mice as well as HEK293 cells, further to explore the functional alternation of CK2 triggers defective heterochromatin DNA damage responses and their contribution to accelerated senescence，evaluating the possibility of reverse early senescence through regulating CK2 activity. These studies will extend the understanding of HGPS, suggesting a potential therapeutic strategy for laminopathy-based premature aging via the intervention of CK2, and also providing evidences for anti- aging.

儿童早老症（HGPS）和限制性皮肤病（RD）是两种由于基因突变所致核纤层蛋白A(lamin A)缺陷性疾病，导致全长或缩短的核纤层蛋白A前体（prelamin A/progerin）在细胞核堆积，引起核形态异常、异染色质结构紊乱、基因组不稳定性和成熟前衰老。我们前期研究发现异染色质蛋白HP1αThr50位点磷酸化水平降低介导了异染色质DNA损伤应答障碍和细胞早老表型。由于蛋白激酶CK2（casine kinase）催化HP1该特异位点磷酸化，本项目以Zmpste24-缺陷小鼠胚胎成纤维细胞（MEFs）及HEK293转染细胞为模拟RD和HGPS的早老模型，拟围绕CK2在早老细胞中稳态和活性改变为中心内容，对CK2引发的异染色质DNA损伤修复障碍与早老表型通路进行探讨，并通过调节CK2活性研究其抗早老的可能性。本项目有利于加深对早老发生机制的认识，为临床治疗早老症和延缓正常衰老提供策略和依据。

核纤层蛋白A异常与早衰发生密切相关，酪蛋白激酶2（CK2）结合核纤层并抑制CK2活性从而促进癌细胞的衰老，由此推测，核纤层蛋白A和CK2在细胞衰老进程中具有重要的调控功能。本项目的研究结果表明CK2的核定位依赖于核纤层蛋白lamin A，并且lamin A蛋白的C-末端结合CK2α的活性中心并抑制其激酶活性。进一步研究表明，Lmna敲除的小鼠胚胎成纤维细胞（MEF）中CK2活性显著增加。相反，在Zmpste24敲出的MEF细胞中prelamin A的积累导致其与CK2α的结合增强并伴随CK2的活性的降低。在野生型MEF细胞中敲低CK2α可加速细胞衰老，而在早老细胞中过表达CK2α可显著降低早老细胞的早老表型。此外，通过亚精胺处理可降低lamin A和CK2之间的结合从而增强其活性，进而促进DNA损伤修复，改善早老表型并延长Zmpste24缺陷小鼠的寿命。以上研究结果揭示了核纤层蛋白lamin A在抑制CK2活性中的新功能，并突出了CK2在调节细胞衰老和机体衰老中的重要作用。本项目的研究成果有利于加深对早老发生机制的认识，为临床治疗早老症和延缓正常衰老提供策略和依据。