INVESTIGATING THE ROLE OF CERULOPLASMIN AND FERROPORTIN IN BRAIN IRON METABOLISM. RELEVANCE TO ACERULOPLASMINEMIA AND OTHER NEURODEGENERATIVE DISORDERS

OBJECTIVES. Our studies will be aimed at clarifying the role of ceruloplasmin (CP) in relation to ferroportin (FPN) in brain iron metabolism. BACKGROUND. Numerous neurodegenerative disorders are associated with brain iron overload. Among these, aceruloplasminemia is a rare autosomal recessive disease caused by mutations in the CP gene; it is characterized also by retinal degeneration, diabetes mellitus and neurologic symptoms (ataxia, involuntary movements and dementia). CP is an enzyme with ferroxidase activity, which is is produced by the liver and secreted into the plasma, where it is thought to promote iron release from cells in combination with the iron exporter FPN. A novel GPI-anchored CP has been identified on the plasma membrane of astrocytes, which is the main CP isoform in the brain. As brain iron deposition and neurodegeneration are evident in aceruloplasminemia, CP-GPI must play an important role. Our hypothesis is that the molecular status of CP affects the correct targeting of FPN. DESCRIPTION OF THE PROJECT. 1) analysis of the subcellular localization of FPN when an inactive CP is being synthesized, i.e. in cells deprived of copper; 2) gene silencing of CP or FPN in cells expressing both proteins to examine the subcellular localization of the surviving partner; 3) test of the possibility that secreted CP can replace CP-GPI in cells transfected to express FPN in the presence or absence of CP-GPI or secreted CP; 4) functional analysis of CP-GPI wt and disease-associated missense mutants in model cell systems co-expressing recombinant CP-GPI and FPN; 5) mapping of the CP-GPI/FPN molecular interaction; 6) study of factors affecting expression of CP and FPN in astrocytes. ANTICIPATED OUTPUT. Understanding the molecular details of the role of CP and FPN in brain iron metabolism will allow to devise specific therapeutic strategies for treatment of aceruloplasminemia and other neurodegenerative pathologies in which brain iron dysmetabolism occurs.