FOR 2290: Understanding Intramembrane Proteolysis

膜内蛋白酶在膜跨越区域内或附近切割底物。因此，这些不寻常的蛋白酶影响广泛的重要生物学功能，并与几种严重疾病有关，包括最常见的神经退行性疾病阿尔茨海默病（AD）。膜内蛋白水解研究的重要性反映在最近一期的《BBA生物膜中的膜内蛋白酶》特刊（2013年第1828卷）和专门的戈登研究会议“细胞表面蛋白的调节蛋白水解-脱落酶和膜内切割蛋白酶：从基础研究到临床应用”（文图拉，2014年3月30日至4月4日）。然而，尽管经过了十多年的研究，我们既不知道底物的全部功能，也不了解底物的分子特性。因此，在结构方面区分底物与非底物的原因尚不清楚。一方面，已知底物的跨膜结构域表现出巨大的初级结构多样性。另一方面，只有一小部分单跨蛋白被称为底物，它们内部的点突变会强烈干扰它们的蛋白水解。这种看似混杂的底物加工和明确的序列特异性底物加工之间的令人困惑的差异表明，它们的跨膜结构域具有相同的结构特征，允许特定蛋白酶的特异性识别和切割。在本提案中组建的研究小组是唯一有资格解决如何实现膜内蛋白质水解特异性的开放问题。其中一些成员在膜内蛋白水解研究方面有着悠久而成功的历史，并且是该领域的开创者之一，而其他成员在跨膜螺旋的结构/功能分析方面具有杰出的专业知识。他们将共同运用跨学科的方法，i)为不同类型的膜内蛋白酶识别新的底物，ii)探索一些典型案例，了解蛋白质水解与底物/酶的相互作用以及底物跨膜螺旋的结构和构象灵活性之间的关系。这需要调查疾病相关底物突变的影响。由于膜内蛋白酶被认为是各种疾病的相关药物靶点，因此为了开发节省和有效的疾病修饰性膜内蛋白酶抑制剂和/或调节剂，对其裂解机制的深入了解至关重要。

Intramembrane proteases cleave their substrates within or adjacent to membrane-spanning regions. Thereby, these unusual proteases affect a wide range of important biological functions and are implicated in several severe diseases including Alzheimer´s diseases (AD), the most common neurodegenerative disease. The great importance of research on intramembrane proteolysis is reflected by a recent special issue on Intramembrane Proteases in BBA Biomembranes (Vol. 1828, 2013) and a dedicated Gordon Research Conference on “Regulated Proteolysis of Cell Surface Proteins - Sheddases and Intramembrane-Cleaving Proteases: From Basic Research to Clinical Applications” (Ventura, March 30 to April 4, 2014). However, despite of more than a decade of research, we neither know the full repertoire of substrates and their functions nor do we understand the molecular properties that qualify a substrate as such. It is thus unclear what distinguishes substrates from non-substrates in structural terms. On the one hand, the transmembrane domains of known substrates exhibit a tremendous diversity of primary structures. On the other hand, only a fraction of single-span proteins are known as substrates and point mutations within them can strongly interfere with their proteolysis. This puzzling discrepancy between seemingly promiscuous and clearly sequence-specific processing of substrates indicates that their transmembrane domains share structural features that allow for specific recognition and cleavage by a given protease. The research group assembled in this proposal is uniquely qualified to solve the open question of how specificity of intramembrane proteolysis is achieved. Some of its members have a long and successful history in intramembrane proteolysis research and were among those who started the field while others have outstanding expertise in the structure/function analysis of transmembrane helices. Together, they will apply a cross-disciplinary approach to i) identify novel substrates for different types of intramembrane proteases and ii) explore for some paradigmatic cases how proteolysis is related to substrate/enzyme interaction and to the structure and conformational flexibility of the substrate transmembrane helices. This entails investigating the effect of disease-associated substrate mutations. Since intramembrane proteases are considered as relevant drug targets for various diseases a deep knowledge of their cleavage mechanism is crucially required in order to develop save and effective disease-modifying intramembrane protease inhibitors and/or modulators.