REGULATION OF LIVER CYTOCHROME P450 TURNOVER/HEPATIC DEGRADATION OF P450 ENZYMES

这个子项目是利用资源的许多研究子项目之一。 由NIH/NCRR资助的中心拨款提供。对子项目的主要支持 子项目的首席调查员可能是由其他来源提供的， 包括美国国立卫生研究院的其他来源。为子项目列出的总成本可能 表示该子项目使用的中心基础设施的估计数量， 不是由NCRR赠款提供给次级项目或次级项目工作人员的直接资金。 肝微体血球蛋白细胞色素P450(P450)包括多种组成酶和诱导酶。在各种生理上相关的内生生物和外生生物的氧化/还原代谢中起作用。这些底物可以通过转录/翻译机制诱导各种P450的含量，也可以通过蛋白质稳定，即抑制其蛋白降解来诱导。这种降解通过泛素依赖的蛋白酶体降解(UPD)、自噬-溶酶体降解(ALD)或在某些情况下通过这两种途径进行。我们研究的长期目标集中在分子水平上对这些过程的表征：标记这些蛋白质进行细胞处理的退化和翻译后修饰以及参与其中的分子伙伴。具体地说，我们希望使用质谱学和/或蛋白质组学分析来表征P450泛素化的位点、伴侣和参与其降解的因素。与Burlingame、Medzihradszky和Maltby博士合作的研究正在进行中，以确定泛素化的P450蛋白的准确氨基酸残基。同时，我们的研究还集中在血红素在调节肝脏P450合成和周转中的作用。拟议的研究集中在生理上相关但被忽视的P450生物学方面。由于P450是一种完整的内质网膜蛋白，对其代谢的研究将为其他内质网居住者提供一个生物学原型。此外，这些研究集中在P450 3A4，这是人类主要的肝脏和肠道酶及其大鼠的同源物，负责超过60%的临床处方药物的代谢，特别容易受到这种生物命运的影响。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. The hepatic microsomal hemoproteins cytochromes P450 (P450) include multiple constitutive and inducible enzymes. that are instrumental in the oxidative/reductive metabolism of various physiologically relevant endobiotics and xenobiotics. These substrates can induce the content of various P450s via transcriptional/translational mechanisms but also via protein stabilization i.e. inhibition of its proteolytic degradation. This degradation proceeds via ubiquitin-dependent proteasomal degradation (UPD), autophagic-lysosomal degradation (ALD) or in some cases by both pathways. The long-term goals of our research are centered on the characterization of these processes at the molecular level: the degrons and posttranslational modifications that mark these proteins for cellular disposal and the molecular partners involved therein. Specifically, using mass spectrometric and/or proteomic analyses we wish to characterize the sites of P450 ubiquitination, the chaperones and factors involved in their degradation. Studies are in progress in collaboration with Drs. Burlingame, Medzihradszky and Maltby to identify the precise amino acid residue of the P450 protein that is ubiquitinated. In parallel our studies also focus on the role of heme in regulating the synthesis and turnover of hepatic P450s. The proposed studies center on a physiologically relevant but neglected aspect of P450 biology. Because P450s are integral ER-membrane proteins, elucidation of its turnover will provide a biological prototype for other ER-residents. Furthermore, these studies are focussed on P450 3A4, the major human liver and intestinal enzyme and its rat orthologs, which are responsible for the metabolism of over 60% of clinically prescribed drugs, and are particularly susceptible to this biological fate.