Kidney Cu Homeostasis and Ceruloplasmin during Infection and Inflammation

点击翻译按钮获取中文摘要

Project Summary Cu is an essential micronutrient that can also be toxic to biological systems. Mammalian cells therefore need to tightly control Cu homeostasis. The kidney appears particularly effective at regulating Cu because this organ displays some of the smallest magnitude of Cu fluctuations during conditions of Cu excess or Cu limitation. However, recently published work in the Culotta lab has shown that kidney Cu levels can fluctuate during infection and inflammation. Specifically in a murine model of disseminated candidiasis, infection with the fungal pathogen Candida albicans stimulated a drop in kidney Cu and the invading pathogen responded by activating a fungal Cu starvation stress response. Concurrent to this drop in kidney Cu, serum Cu levels rose. In my preliminary studies, I discovered that the cause of this high serum Cu is a strong elevation in serum ceruloplasmin (Cp), an acute phase protein. Ceruloplasmin is a multi-copper oxidase for controlling Fe homeostasis and I observed increases in both Cp protein levels and Cp activity that can account for virtually all the elevated serum Cu. I hypothesize that during C. albicans infection, the demand for high Cu in producing ceruloplasmin triggers a loss in Cu from the kidney, and this drop in Cu is mediated through regulation of kidney Cu uptake or efflux. To investigate this hypothesis I will carry out the following aims. Aim 1: To define the host and fungal Cu responses as a function of infection severity. I will identify the level of infection required to stimulate the host Cu response (elevating serum Cp and decreasing kidney Cu) as well as the fungal Cu response (activate the Cu starvation stress response). Aim 2: To understand the mechanism for kidney Cu loss during infection. I will investigate the mechanism by which kidney Cu decrease occurs: does this involve reduced Cu uptake or enhanced Cu efflux? I will scrutinize both protein levels and localization of the Cu uptake transporter CTR1 and the Cu efflux transporter ATP7A in an effort to answer this question. Aim 3: Determine the signal for Cu loss in the kidney. To determine whether serum Cp is sufficient to induce kidney loss of Cu without fungal infection, I will inject mice with lipopolysaccharide and heat-killed C. ablicans cells, both of which will induce an inflammatory response including Cp induction without infection. Furthermore I will test if the phenomenon of kidney Cu loss occurs in Cp-/- homozygous deletion mice infected with C. albicans. Together these studies will provide insight into the mechanisms by which kidney Cu homeostasis is affected by infection and inflammation.