CASPASE CLEAVAGE OF BRAIN FODRIN

许多神经病理标志物与阿尔茨海默病有关 (AD)，其中包括总脑胞膜蛋白（非红细胞）的增加 血影蛋白）和这种蛋白质在 退化的神经元 Fodrin是一种外周膜蛋白， 质膜和细胞骨架之间的关键联系， 神经元 AD中的胞衬蛋白沉积与一个显著的 150 kDa分解产物（BDP）增加。 据信， 由钙蛋白酶切割胞衬蛋白的α-亚基产生，和 在AD脑中检测到钙蛋白酶的广泛激活。更 然而，最近，关键细胞蛋白的半胱天冬酶裂解被 被认为是造成形态和功能变化的原因 当细胞发生凋亡时观察到。 胞衬蛋白的裂解， 半胱天冬酶与磷脂酰丝氨酸的暴露直接相关 在细胞表面，也被牵连在触发膜 起泡 一个假定的半胱天冬酶切割位点已被确定， 胞衬蛋白的α亚基，位于主要钙蛋白酶裂解的下游 绝佳的价钱此外，针对钙蛋白酶介导的 胞衬蛋白中的切割位点也识别半胱天冬酶衍生的BDP。这些 令人惊讶的结果加上越来越多的证据表明， 细胞凋亡作为AD神经元丢失的机制，表明更多的 可能有一种以上的机制参与胞衬蛋白BDP的积累， AD. 此外，由于胞衬蛋白BDPs积累稳定， 细胞内沉积物，并由两个不同的家族裂解， 它们代表具有新抗原表位的死亡产物 提供了钙蛋白酶和半胱天冬酶对 神经退行性疾病 我们的主要工作是：1）研究胞衬蛋白BDP 暴露于几种不同的凋亡损伤的神经元的特征， 鉴定胞衬蛋白α-亚基的半胱天冬酶切割位点; 2） 确定β-半胱天冬酶中的假定的半胱天冬酶切割位点是否是 胞衬蛋白的亚基在细胞凋亡期间被切割; 3）确定胞衬蛋白的亚基是否在细胞凋亡期间被切割。 红细胞形式的胞衬蛋白仅限于树突，有些是 也是半胱天冬酶底物;和4）产生裂解胞衬蛋白定点 抗胱天蛋白酶介导的胞衬蛋白的BDPs的抗体， 上述目标。胞衬蛋白的BDPs明显代表了一个独特的特征 发生在AD中的神经病理学变化，以及 特异性识别胱天蛋白酶裂解死亡产物应提供 细胞凋亡在神经退行性变中的作用 疾病

Many neuropathological markers have been linked to Alzheimer s disease (AD), among them is an increase in total brain fodrin (non-erythroid spectrin) and accumulation of abnormal depositions of this protein in degenerating neurons. Fodrin, a peripheral membrane protein, provides a critical link between the plasma membrane and the cytoskeleton in neurons. The fodrin deposits in AD correlate with a significant increase in 150kDa breakdown product (BDP). This fodrin BDP is believed to result from calpain cleavage of the alpha-subunit of fodrin, and widespread activation of calpain has been detected in AD brains. More recently, however, caspase cleavage of critical cellular proteins is believed to be responsible for the morphological and functional changes observed when cells undergo apoptosis. The cleavage of fodrin by caspases has been directly linked to the exposure of phosphatidylserine on the cell surface, and has also been implicated in triggering membrane blebbing. A putative caspase cleavage site has been identified in the alpha-subunit of fodrin, just downstream of the major calpain cleavage site. Moreover, antibodies developed against the calpain-mediated cleavage site in fodrin also recognize the caspase-derived BDP. These surprising results coupled with increasing evidence implicating apoptosis as the mechanism of neuronal loss in AD, suggest that more than one mechanism may be involved in the accumulation of fodrin BDP in AD. Additionally, because the fodrin BDPs accumulate as stable intracellular deposits and are cleaved by two distinct families of proteases they represent death products with novel antigenic epitopes that provide a signature of the contribution of calpain and caspases to neurodegenerative diseases. We propose to: 1) study the fodrin BDP profiles in neurons exposed to several distinct apoptotic insults and identify the caspase cleavage site(s) the alpha-subunit of fodrin; 2) determine whether the putative caspase cleavage sites in the beta- subunit of fodrin are cleaved during apoptosis; 3) determine if the erythroid forms of fodrin that are restricted to dendrites and some are also caspase substrates; and 4) develop cleavage fodrin site-directed antibodies against the caspase-mediated BDPs of fodrin identified in the above aims. The BDPs of fodrin clearly represent a unique signature of the neuropathological changes that occur in AD, and antibodies that specifically recognize caspase cleavage death products should provide insights into the contribution of apoptosis in neurodegenerative diseases.