Porphyrin Biosynthesis in Normal and Disease States

描述（由申请人提供）：血红素生物合成是红细胞和非红细胞的重要过程。迟发性皮肤卟啉症（PCT）是血红素生物合成途径第5步的缺陷，是人类最常见的卟啉症。PCT是由于降低了特定活性的尿卟啉原脱羧酶（URO- D），并导致中间产物尿卟啉的大量积累。我们已经证明，abc型转运体负责将尿卟啉转移到酵母的液泡中。我们将通过靶向蛋白质组学和酵母的互补来鉴定哺乳动物转运体。我们将通过敲除细胞中的候选转运蛋白并寻找卟啉定位来确认转运蛋白的身份。我们还将定义细胞将卟啉从溶酶体转移到细胞质的方法。我们的第二个具体目标是利用红细胞生成原卟啉（EPP）的酵母模型来确定将原卟啉从线粒体基质转移到细胞质溶胶所需的转运蛋白。总的来说，这些研究将确定卟啉中间体在细胞内和细胞外运动的运输机制。已确定的转运蛋白是潜在的相关危险因素，可以解释PCT和EPP表型中观察到的表型多样性。

DESCRIPTION (provided by applicant): Heme biosynthesis is an essential process in erythroid and non-erythroid cells. Porphyria cutanea tarda (PCT), a defect in step 5 of the heme biosynthetic pathway, represents the most common form of porphyria in humans. PCT is due reduced specific activity uroporphyrinogen decarboxylase (URO- D), and results in a massive accumulation of the intermediate, uroporphyrin. We have shown that an ABC-type transporter is responsible for moving uroporphyrin into the vacuole in yeast. We will identify the mammalian transporter through targeted proteomics and complementation in yeast. We will confirm the transporter identity by knocking down the candidate in cells and looking for porphyrin localization. We will also define the method used by cells to transfer porphyrins from the lysosome to the cytosol. Our second specific aim will utilize a yeast model of erythropoietic protoporphyria (EPP) to identify the transport protein required to move protoporphyrin from the mitochondrial matrix to the cytosol. Collectively, these studies will define the transport mechanisms involved in the movement of porphyrin intermediates within and from cells. The identified transporters are potential associated risk factors that may explain the phenotypic diversity observed in the PCT and EPP phenotypes.