COPPER HOMEOSTASIS IN MAMMALS

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The trace metal copper (Cu) is essential for life as a critical co-factor for a wide variety of enzymes that play key roles in processes such as respiration, connective tissue maturation, iron mobilization, oxidative stress protection and neuropeptide processing. The inability of mammals to acquire sufficient Cu is associated with developmental abnormalities of the central nervous system, anemia, defects in angiogenesis and a variety of other defects in growth and development. Although cellular components involved in Cu uptake have been identified in lower eukaryotes, little is known about the identity of proteins that mediate Cu acquisition, nor their mechanisms of action or regulation in mammals. Human and mouse Ctrl complementary DNAs have been isolated based on their ability to suppress growth and biochemical defects associated with baker's yeast cells that are defective in high affinity Cu transport. Although the structure of mammalian Ctrl, its tissue-specific expression and its ability to stimulate Cu acquisition in yeast and cultured human cells are compatible with a role in high affinity Cu transport, the physiological role of Ctrl in mammals, and its mechanisms of action and regulation are unknown. This proposal describes avenues of investigation with the goal of understanding the role and mechanism of action of Ctrl in mammalian Cu acquisition. First, the physiological role of Ctrl in Cu transport will be determined through the creation and analysis of mice lacking a functional Ctrl gene. Second, the tissue-specific expression, developmental regulation and localization of the mouse Ctrl protein will be characterized. Third, the mechanisms by which Ctrl facilitates the transport of Cu across cellular membranes and how this process may be regulated as a function of dietary Cu need will be ascertained. Fourth, the mechanisms by which mammalian Ctr2 protein functions, in concert with Ctrl, to facilitate and perhaps modulate Cu acquisition will be elucidated. These investigations will provide fundamentally important information on how mammals acquire Cu from nutrients and how inappropriate Cu acquisition leads to pathophysiological states that have, as their underlying basis, defects in Cu-dependent biochemical processes.