FUNCTIONAL ASPECTS OF MULTICATALYTIC PROTEINASE

多催化蛋白酶复合物（MPC），也称为多催化蛋白酶复合物。 蛋白酶体，是一种高分子量（约700 kDa） 由28至32个低分子量亚基组成细胞内颗粒 (22 34 kDa），其中13个是不相同的。MPC的重要性 对于基本细胞功能的研究表明， 存在于所有真核细胞中，它是高度保守的 进化，它参与抗原加工， 构成了泛素依赖性途径的“蛋白水解核心” 细胞内蛋白水解，它是不可或缺的细胞 生存和增殖。MPC表达的变化 与恶性肿瘤的病理生理学有关， 在患者血清中发现了抗MPC的自身抗体 系统性红斑狼疮MPC显示出三种不同的 蛋白水解活性切割羧基侧的肽键， 碱性、酸性和疏水性氨基酸残基，它们都对 通过3，4-二氯异香豆素（DCI）（一种通用丝氨酸）灭活 蛋白酶抑制剂我们最近发现了第四种， 在支链的羧基侧上切割肽键的组分 链氨基酸，并构成了降解的主要因素， 蛋白质和天然肽。该实验室的主要目标是 确定MPC的哪些子单元和多少个子单元是 蛋白水解活性，以确定其特异性和蛋白水解 机制，以检查调节蛋白水解活性的因素 并合成特异性抑制剂， 研究复合物在细胞功能中的作用。的目的 这一建议是：1）评估的特异性和监管 第四种DCI抗性成分的活性，2）确定是否存在 最近鉴定的脯氨酰氨基肽酶样活性表达为 MPG的一种新成分，如果是这样， 和特异性，3）确定最近鉴定的脯氨酰- 内肽酶样活性是由于一种独特的组分，如果是这样， 检查其属性和特异性，4）调查 一组肽的结构要求和动力学， 激活MPC，5）在完整细胞中检查MPC的功能 通过研究特异性抑制剂对细胞内蛋白质的影响， 降解和细胞增殖。

The multicatalytic proteinase complex (MPC), also referred to as the proteasome, is a high molecular mass (approximately 700 kDa) intracellular particle composed of 28 to 32 low molecular mass subunits (22 to 34 kDa) of which 13 are nonidentical. The importance of the MPC for fundamental cell functions is indicated by the finding that it is present in all eukaryotic cells, that it is highly conserved in evolution, that it is involved in antigen processing, that it constitutes the 'proteolytic core' of the ubiquitin-dependent pathway for intracellular proteolysls and that it is indispensable for cell survival and proliferation. Changes in the expression of the MPC have been implicated in the pathophysiology of malignancies, and autoantibodies against the MPC have been found in serum of patients with systemic lupus erythematosus. The MPC exhibits three distinct proteolytic activities cleaving peptide bonds on the carboxyl side of basic, acid and hydrophobic amino acid residues, all sensitive to inactivation by 3,4-dichloroisocoumarin (DCI), a general serine protease inhibitor. We have recently identified a fourth, DCI resistant component that cleaves peptide bonds on the carboxyl side of branched chain amino acids, and constitutes a major factor in the degradation of proteins and natural peptides. Major goals of this laboratory are to determine which and how many of the subunits of the MPC are proteolytically active, to identify their specificity and proteolytic mechanism, to examine factors that regulate the proteolytic activity and to synthesize specific inhibitors that could be used as probes in studies on the role of the complex in cellular functions. The aims of this proposal are: 1) to evaluate the specificity and regulation of activity of the fourth, DCI resistant component, 2) to determine if a recently identified prolyl aminopeptidase-like activity is expressed by a novel component of the MPG, and if so to investigate its properties and specificity, 3) to determine if a recently identified prolyl- endopeptidase-like activity is due to a unique component, and if so to examine its properties and specificity, 4) to investigate the structural requirements and kinetics of a group of peptides that activate the MPC, 5) to examine the function of the MPC in intact cells by studying the effect of specific inhibitors on intracellular protein degradation and on cell proliferation.