Functional Analysis of Hsp33-a Redox Regulated Chaperone

描述(由申请人提供)：在过去的几年里，在理解氧化应激及其对蛋白质等大分子的影响方面取得了良好的进展。氧化修饰的蛋白质已被证明在衰老、癌症和许多其他病理条件下积累。这进一步增加了人们对压力环境的兴趣，这种压力对于生活在无氧生活方式的有机体来说是不可避免的。现在，已经确定了一些利用氧化应激作为其功能活性调节的蛋白质。这些蛋白质具有共同的高活性半胱氨酸，可以感知环境氧化还原电位的变化，并将其转化为蛋白质构象和活性的变化。我们发现这些新的氧化还原调节蛋白之一是分子伴侣Hsp33。Hsp33是一种折叠辅助蛋白，似乎专门保护细胞免受氧化应激的致命影响。现在，我们将分析HSP33如何执行此任务。我们将确定伴随着Hsp33激活和失活过程的构象重排，并将确定底物识别的潜在机制。我们将定义什么是热休克蛋白33的S底物在热和氧化应激条件下。这不仅使我们能够鉴定和分类受HSP33保护的氧化敏感蛋白，还可以解释HSP33的S底物专一性与其他分子伴侣的不同。我们将探索Hsp33将其一些底物蛋白递送到细胞的蛋白水解系统的可能性。众所周知，许多氧化修饰的蛋白质是不可逆转的损伤，需要被降解，然后它们才能作为有害的、不可溶的蛋白质聚集体积累在细胞中。由于HSP33对蛋白质折叠中间体有很高的亲和力，这种底物转移到细胞内的蛋白酶可能也解释了为什么在非应激条件下HSP33的S伴侣活性需要下调。否则，Hsp33有可能通过过早地将折叠蛋白呈现给细胞的蛋白分解系统来干扰正常的蛋白质折叠过程。

DESCRIPTION (provided by applicant): Over the past few years, good progress has been made in understanding oxidative stress and its consequences for macromolecules such as proteins. Oxidatively modified proteins have been shown to accumulate during aging, cancer and many other pathological conditions. This has further increased the interest in a stress situation that is simply unavoidable for organisms that live an anaerobic lifestyle. Now, a number of proteins have been identified which use oxidative stress as a regulator for their functional activity. These proteins have in common highly reactive cysteines that sense the changes in the redox potential of the environment and translate them into changes of protein conformation and activity. We discovered that one of these novel redox regulated proteins is the molecular chaperone Hsp33. Hsp33 is a folding-helper protein that appears to be specialized to protect cells against the otherwise lethal effects of oxidative stress. We will now analyze how Hsp33 performs this task. We will identify the conformational rearrangements that accompany the activation and inactivation process of Hsp33 and we will determine the underlying mechanism of substrate recognition. We will define what Hsp33's substrates are under heat and oxidative stress conditions. This will not only allow us to identify and classify oxidation sensitive proteins which are protected by Hsp33 but may also explain how Hsp33's substrate specificity differs from that of other molecular chaperones. We will explore the possibility that Hsp33 presents some of its substrate proteins to the proteolytic system of the cell. It is known that many oxidatively modified proteins are irreversibly damaged and need to be degraded before they can accumulate as harmful, insoluble protein aggregates in the cell. Since Hsp33 has a very high affinity to protein folding intermediates, this substrate transfer to cellular proteases might also explain why Hsp33's chaperone activity needs to be down regulated under non stress conditions. Otherwise, Hsp33 has the potential of interfering with ,the normal protein folding process by prematurely presenting folding proteins to the proteolytic system of the cell.