Intracellular Pathways of Manganese Trafficking

描述（由申请人提供）：锰是一种必需的微量营养素，也有潜在的毒性。在哺乳动物中，锰是一种强效的神经毒素，与帕金森病样综合征有关。然而，令人惊讶的是，人们对这种金属的细胞生物学及其毒性机制知之甚少。我们一直在利用面包酵母酿酒酵母作为模型系统来表征控制锰稳态的真核因子。在过去的资助期内，我们已经确定了许多这样的因素，包括：Smf2p，一种定位于细胞内囊泡并在锰运输中起核心作用的NRAMP金属转运体；Mtm1p，一种假定的线粒体锰转运蛋白；磷酸盐代谢因子是锰毒性的关键决定因素。通过四个具体目标，我们将继续我们的研究这些和其他锰稳态因素。我们的目标是：(1)定义Smf2p锰运输囊泡的性质，并解决内吞作用在锰的摄取和细胞内运输中的作用；(2)阐明酵母和人Mtm1p在锰转运到线粒体基质中的作用；(3)确定磷酸盐代谢途径如何调节细胞对锰毒性的抗性；(4)利用酵母遗传学鉴定新的锰稳态因子，包括假定的锰金属伴侣。总的来说，这些研究将结合酵母分子遗传学，生物化学和细胞生物学的不同学科，为必需但潜在有毒的锰离子的动态平衡提供新的见解。

DESCRIPTION (provided by applicant): Manganese is an essential trace nutrient that is also potentially toxic. In mammals, manganese is a potent neurotoxin and has been implicated in Parkinson's disease-like syndromes. Yet surprisingly little is known regarding the cell biology of this metal and its mechanisms of toxicity. We have been exploiting the bakers' yeast S. cerevisiae as a model system to characterize eukaryotic factors that control manganese homeostasis. Over the past funding period, we have identified a number of such factors including: Smf2p, a NRAMP metal transporter that localizes to intracellular vesicles and plays a central role in manganese trafficking; Mtm1p, a putative manganese transporter for the mitochondria; and phosphate metabolism factors that are critical determinants of manganese toxicity. Through four specific aims, we will continue our investigations of these and other manganese homeostasis factors. Our goals are to (1) Define the nature of the Smf2p manganese transport vesicles and to address the role of endocytosis in the uptake and intracellular trafficking of manganese; (2) Elucidate the role of yeast and human Mtm1p in the transport of manganese into the mitochondrial matrix; (3) Determine how phosphate metabolism pathways modulate cellular resistance to manganese toxicity; and (4) Employ yeast genetics to identify new manganese homeostasis factors, including putative manganese metallochaperones. Overall, these studies will combine diverse disciplines of yeast molecular genetics, biochemistry and cell biology to provide new insight into the homeostasis of essential, but potentially toxic manganese ions.