Molecular Mechanisms of Active Copper Transport

PROJECT SUMMARY This proposal is to continue studies aimed to understand how absorption of different nutrients is coregulated by small intestine in health and disease. Proper nutrient absorption by gastrointestinal tract is essential for human health; dysregulation of GI function results in a broad spectrum of human disorders and in extreme cases, death. We have discovered an unexpected and tight relationship between copper transport and fat absorption in both healthy intestine and in the animal model of Wilson disease (WD). We demonstrated that copper modulates maturation and trafficking of chylomicrons, the major carriers of dietary fat, and identified specific steps in chylomicron processing that are sensitive to copper levels. Moreover, fatty acids regulate trafficking and localization of Cu transporters in enterocytes, providing a feedback loop. We will now identify the molecular mechanism of this co-regulation and examine how it is altered in human disease. In Specific Aim 1, we will characterize the role of the copper transporters ATP7A and SLC31A1 in chylomicrons secretion by examining the effects of their intracellular localization on ApoB trafficking, lipid content, and chylomicrons secretion. Experiments in Specific Aim 2 will elucidate how intestinal ANKRD9 senses ATP levels and facilitates ApoB and Slc31a1 trafficking in enterocytes; this will be done by characterizing the ANKRD9 macromolecular complexes and identifying ANKRD9 ATP-sensing site(s). Specific Aim 3 will determine how Cu misbalance impacts metabolic status of human intestine in WD by characterizing the duodenal proteomes of non-treated and chelator treated WD patients, as well as non-WD controls. Single cell nuclear sequencing of human WD tissue will establish how Cu misbalance impacts cell speciation in intestine and the metabolic state of human intestine.