SLC40A1 (MTP1 aka ferroportin or IREG1) is highly expressed on macrophages where it mediates iron efflux from the breakdown of haem. SLC40A1 colocalises with ceruloplasmin (CP) which stablizes SLC40A1 and is necessary for the efflux reaction to occur. Six copper ions are required by ceruloplasmin as a cofactor.
Defects in SLC40A1 can cause hemochromatosis 4 (HFE4; MIM:606069), a disorder of iron metabolism characterised by iron overload. Excess iron is deposited in a variety of organs leading to their failure, resulting in serious illnesses including cirrhosis, hepatomas, diabetes, cardiomyopathy, arthritis and hypogonadotropic hypogonadism. Severe effects of the disease don't usually appear until after decades of progressive iron overloading (De Domenico et al. 2005, 2006, 2011, Kaplan et al. 2011).