ANALYSIS OF FUNCTION OF HUMAN BRAIN CARBOXYPEPTIDASE B-SPECIFIC C14-MODULE

为了阐明人脑羧基肽酶B(HBCPB)的病理生理学意义，我们用(1)形态分析和(2)分子生物化学分析方法，对人脑羧基肽酶B(HBCPB)的C14模式进行了分析.(1)通过对5例散发性阿尔茨海默病患者和正常老年人的比较分析，获得了以下形态上的新发现.HBCPB在神经元核周的表达已被确认为内质网，分析了整个神经元。在所有正常大脑中，HBCPB在限制性神经元中表达，包括阿尔茨海默病中高度脆弱的神经元，如海马锥体神经元，也表达在未受累的神经元，如外侧膝状体神经元。然而，在分析的所有五个阿尔茨海默病患者的大脑中，HBCPB在海马区锥体神经元中的表达显著减少，但在外侧膝状体晚期神经元中的表达没有显著下降。在所有阿尔茨海默病患者中，HBCPB-C14-模块的选择性表达减少和在内质网中的非均一表达模式表明，神经元特异性抑制HBCPB的表达在阿尔茨海默病的进展中具有病理生理学意义。(2)利用抗C14-模块抗体对HBCPB-C14-模块的表位分析表明，该模块由两个表位组成(每个表位7个氨基酸残基)：EP1和EP2。前者的表位是高度独立的，并制备了针对EPI多肽的兔抗体(抗C14-EP1)。在HBCPB对合成的Aβ1-42的外切蛋白分析中，EPI肽或抗C14-EP1抗体的共存都抑制了该反应。综上所述，从C14模块分析HBCPB的功能是重要的，并为理解HBCPB作为阿尔茨海默病治疗靶点的意义奠定了坚实的背景。

To clarify a pathophysiological significance of human brain carboxypeptidase B (HBCPB), the specific C-terminal region, C14-moduIe, was analyzed by (1) morphological and (2) molecular-bioc hemical analyses.(1) Through comparative analysis between five cases of sporadic Alzheimer's disease patients and normal aged, the following morphological novel findings were obtained. HBCPB expression in neuronal perikarya, which was already identified as endoplasmic reticulum, was analyzed throughout neurons. In all normal brains, HBCPB is expressed in restricted neurons including highly vulnerable neurons in Alzheimer's disease such as hippocampal pyramidal neuron and also in uninvolved neurons such as lateral geniculate body neurons. In all five Alzheimer's brains analyzed, however, HBCPB expression in hippocampal pyramidal neurons, but not in lateral genicu late body neurons, were significantly decreased. Selective decrease in expressed amount and nonhomogeneous expression pattern in endoplasmic reticulum in all Alzheimer's cases indicate that neuron-specific inhibition of HBCPB expression is of pathophysiological significance in progress ion of Alzheimer's disease.(2) By epitope analysis of HBCPB-C14-module using anti C14-module antibody, it was clarified that the module is composed of two epitopes (each 7- amino' acid residues), EP1 and EP2. The former epitope is highly independent, and an rabbit antibody was raised against EPI peptides (anti C14-EP1). In the exoproteolytic analysis of synthetic Aβ1-42 by HBCPB, both co-existence of EPI peptide or anti C14-EP1 antibody inhibited the reaction.Taken together, it was clarified that functional analysis of HBCPB by focusing on C14-module is important, and a substantial background was establ ished to understand the significance of HBCPB as therapeutical target for Alzheimer's disease.