Hereditary hemochromatosis (HH) is a common inherited disorder. Iron overload results in damage to specific organs including the liver, heart, and pancreas resulting in cirrhosis of the liver, liver cancer, diabetes, cardiomyopathy. Iron also accumulates in joints causing arthritis. The liver is the major iron-sensing organ and controls iron homeostasis in the body. Mutations in transferrin receptor 2 (TfR2), HFE and hemojuvelin (HJV) lead to HH. TfR2 is hypothesized to sense iron in the body. The role that TfR2 plays in sensing iron remains controversial. The association between TfR2 and HFE is still debated. TfR2 also associates with HJV in vitro. We propose to determine the mechanisms by which TfR2 controls iron homeostasis in the body. Adeno- associated viral vectors used in gene therapy trials in combination with protein proximity assays and phosphoproteomic analysis will be utilized to determine the interaction partners of TfR2 in vivo. The long-term goal of this research is to understand how mutations in key proteins that disturb the iron balance in the body, reveal the mechanisms by which the body regulates iron-homeostasis.