脑内松果体生物矿化的分子机制

Acervuli are calcified concretions in the pineal gland (PG). The degree of pineal calcification is associated not only with melatonin secretion, but also with many neurodegenerative disorders, such as Alzheimer's disease, multiple sclerosis, epilepsy, and Schizophrenia. The role of calcification in the pathogenesis of pineal gland dysfunction remains unknown but the available data document that calcification is an organized, regulated process, rather than a passive aging phenomenon. The cellular biology and micro-environmental conditions required for calcification remain poorly understood. The aim of the present study was to inestigate the growth morphology of acervuli in PGs by a direct visualization in 3-dimension (3-D) using a synchrotron X-ray imaging method in rat cerebral infarction model and Alzheimer's disease or Parkinson's disease transgenic mice.Focal cerebral ischemia was induced by middle cerebral artery occlusion (MCAO). Male Sprague-Dawley rats were treated with vehicle or melatonin (5 mg/kg) prior to MCAO, and cerebral cortical tissues were collected 24 hr after MCAO. Fam20C, the archetypical member, phosphorylates secreted proteins within Ser-x-Glu/pSer motifs which dedicated to the phosphorylation of extracellular proteins.Fam20C appears to be the Golgi casein kinase that phosphorylates secretory pathway proteins within S-x-E motifs. Fam20C phosphorylates the caseins and several secreted proteins implicated in biomineralization,including the small integrin-binding ligand, N-linked glycoproteins (SIBLINGs).Melatonin has anti-oxidant activity and it exerts a neuroprotective effects during ischemic brain injury. Calcium-buffering proteins including parvalbumin and hippocalcin are involved in neuronal differentiation and maturation through calcium signaling. These data raise the possibility that Fam20C and melatonin in concert to regulate acervuli in pineal gland. This study is the first to define an essential role for the Fam20 family of secreted protein kinases in pineal calcification and provides a new molecular entry point which will allow researchers to delineate novel protein kinase regulating the process of biomineralization.

松果体是脑内重要神经内分泌器官，通过分泌褪黑素调节机体的生物节律。而存在于人脑松果体内受磷酸激酶调控、以钙离子为特征的生物矿化，在临床上被认为与多种神经系统疾病密切相关，其矿化形成机制、动态过程与病变的关系在国内外研究极少。本课题拟利用脑梗塞与帕金森病等动物模型、松果体神经元和神经胶质细胞，研究脑内松果体矿化机制，在生理环境探讨病理性的脑内松果体无机晶体成核、生长及组装的动态过程，揭示细胞外磷酸激酶启动松果体矿化和褪黑素及受体相互作用促进晶体生长的规律，并结合临床患者脑脊液观察对松果体神经元、胶质细胞、松果体血-脑脊液屏障的生物矿化的影响。本项研究采用现代化学、纳米和医学技术，在无机化学与神经医学的前沿交叉领域开展原创性研究，探讨和揭示"脑内松果体矿化与神经性疾病关系"这一新的科学问题，不仅丰富和拓展生物无机化学中生物矿化的研究内涵，也将为上述神经性疾病的诊断、预防和治疗提供新的解决思路。

松果体是脑内重要神经内分泌器官，通过分泌褪黑素调节机体的生物节律。本课题利用松果体神经元和神经胶质细胞，研究脑内松果体矿化机制。为揭示松果体神经元相关的活性氧物种的细胞内平衡态维持机制及重要线粒体蛋白功能，系统研究了线粒体蛋白MnSOD 的乙酰化影响酶活的机理，发现了决定MnSOD 活性的关键乙酰化位点Lys68，建立了乙酰化调控MnSOD 表面静电势影响超氧阴离子进入超氧清除活性中心的新模型；为了探究68 位赖氨酸乙酰化影响MnSOD 酶活的机理，解析了第一个通过基因密码子扩展方法获得的定点乙酰化修饰的蛋白晶体结构，进一步阐明静电作用影响乙酰化MnSOD 活性的重要机制；为了调控细胞内线粒体的超氧水平，筛选得到线粒体去乙酰化酶SIRT3 的小分子激活剂C12，其与SIRT3 的结合常数Kd 值达到3.9uM，结合能力显著优于白藜芦醇与SIRT3 的亲和力；为了验证化合物C12 在退行性病变中的潜在治疗作用，在原代神经胶质细胞和松果体神经元内发现了化合物C12 依赖于去乙酰化酶SIRT3 对线粒体超氧水平和MnSOD 乙酰化水平的调控，揭示C12 潜在的治疗神经退行性病变的作用。