iNOS Aggresome as a Prototype of a Physiologic Aggresome

描述（申请人提供）：蛋白质的错误折叠在几种肺部疾病的发病机制中起重要作用。错误折叠和聚集的蛋白质在细胞中通过伴侣介导的重折叠处理，或被蛋白酶体降解破坏。最近的证据表明，细胞已经进化出了第三种途径，包括将错误折叠的蛋白质隔离到靠近细胞核的专门的“保存站”，称为聚合体。认识到这一主题的重要性，NHLBI召开了一次研讨会来审查蛋白质加工相关问题。讲习班强调需要了解聚合体的性质和作用及其形成的细胞机制。我们已经发现细胞通过聚合体的形成来调节诱导型一氧化氮合酶（iNOS）。这种新发现的iNOS聚集体是首次描述的与蛋白质错误折叠无关的聚集体，我们将其称为“生理性聚集体”。这一发现为一个独特的研究机会奠定了基础。对生理聚合体的研究将揭示关于细胞如何通过聚合体的形成来调节蛋白质的丰富信息。我们假设：A) iNOS生理性聚集体与先前描述的与错误折叠蛋白质相关的“病理性”聚集体具有某些特征。因此，病理性的聚集体可能仅仅代表一个既定的生理调节过程的加速。B)细胞中聚合体形成的调控与细胞及时降解蛋白质的能力有关。每当细胞感觉到由于产生错误折叠的蛋白质或大量的某种蛋白质而可能超过这种能力时，它们就会触发聚合体的形成。细胞依靠聚集体形成的决定导致特定的蛋白质迁移参与聚集体的形成和调节。为了验证这些假设，我们提出了以下具体目标的研究：1)表征iNOS聚集体的形成和调控机制。2) iNOS聚集体形成蛋白的鉴定。3)检测含有与肺部疾病相关的错误折叠突变蛋白（如a1-抗胰蛋白酶突变体）的细胞中iNOS聚集体的调控。提出这些研究的基本原理是，一旦这些机制被理解，它们将大大增加我们对细胞处理错误折叠蛋白质的理解。未来的治疗策略可以设计为在疾病状态下调节这些细胞反应。

DESCRIPTION (provided by applicant): Misfolding of proteins plays an important part in the pathogenesis of several lung diseases. Misfolded and aggregated proteins are handled in the cell through chaperone-mediated refolding, or destroyed by proteasomal degradation. Recent evidence suggests that cells have evolved a third pathway that involves sequestration of misfolded proteins into specialized "holding stations", close to the nucleus, called aggresomes. Recognizing the importance of this topic, the NHLBI convened a workshop to review protein processing related issues. The workshop emphasized the need for understanding the nature and the role of aggresome and the cellular mechanisms of its formation. We have discovered that cells regulate inducible nitric oxide synthase (iNOS) through aggresome formation. This newly discovered iNOS aggresome is the first described occurrence of an aggresome that is not associated with protein misfolding and which we termed "physiologic aggresome". This discovery sets the stage for a unique research opportunity. Study of the physiologic aggresome should reveal a wealth of information regarding how cells regulate proteins through aggresome formation. We hypothesize that: A) iNOS physiologic aggresome shares certain features with what previously described as "pathologic" aggresome associated with misfolded proteins. Thus, pathologic aggresome may merely represent an acceleration of an established physiologic regulatory process. B) The regulation of aggresome formation in cells is linked to cell capacity to degrade proteins in a timely manner. Whenever cells sense that this capacity is likely to be exceeded due to the generation of either a misfolded protein or a large amount of a certain protein, they trigger aggresome formation. The decision of cells to resort to aggresome formation results in specific proteins migrating to participate in the formation and the regulation of the aggresome. To test these hypotheses we propose studies with the following specific aims: 1) Characterization of mechanisms of formation and regulation of iNOS aggresome. 2) Identification of proteins forming iNOS aggresome. 3) Examination of the regulation of iNOS aggresome in cells harboring misfolded mutant proteins related to lung disease such as a1-antitrypsin mutants. The rationale for the proposed studies is that once these mechanisms are understood, they would greatly increase our understanding of cellular handing of misfolded proteins. Future therapeutic strategies can be designed to regulate these cellular responses in disease states.