Collaborative Research: Mechanisms of Iron Transport in Insects

Metropolitan State University Of Denver, Denver CO

Investigators

Abstract

Iron is essential for many aspects of an animal's life, but iron is also potentially toxic. Because iron is both necessary and harmful, the amount, location and form of iron within an animal must be tightly controlled. In humans and other mammals, the physiological processes that provide the right amount of iron at the right times are partially understood. However, in insects and other invertebrate animals, these processes have not yet been discovered. The goal of this research project is to understand how iron is transported from one cell to another in insects using the fruit fly as a model system. The project will provide research experiences for undergraduate students from diverse backgrounds. Knowledge gained from this research will provide a framework for future studies of iron transport in blood-feeding insects such as mosquitoes, which must cope with a seemingly toxic amount of iron when they ingest a blood meal. A potential outcome of this project is the discovery of a more evolutionarily ancient iron transport mechanism that functions not only in insects but also in other invertebrate animals. In addition, information learned from this research may provide insight into the less-understood mechanisms of iron transport in humans. Finally, because insect management strategies rely on information about insect biology, the results of this project may contribute to the development of a new insect control strategy. The goal of the proposed research is to understand the physiological mechanisms of iron transport in insects. Four models that describe possible mechanisms of iron transport into cells will be tested using Drosophila melanogaster as the model insect species. OBJECTIVE 1: The first objective is to test the hypothesis that receptor-mediated endocytosis of iron-loaded ferritin or ferric-transferrin transports iron from hemolymph into cells. 1A) Ferritin and transferrin will be labeled with a fluorophore and then observed to determine whether cellular uptake occurs. 1B) Confocal microscopy will be used to evaluate whether ferritin or transferrin are present in endosomes. 1C) Essential components of the endocytosis pathways will be blocked, and the effect on iron uptake will be measured. OBJECTIVE 2: The second objective is to test the hypothesis that reduction of ferric ions in hemolymph leads to iron transport into cells. Hemolymph contains iron in the ferric form, but iron transporters in animals are specific to ferrous iron; therefore, iron uptake via an influx transporter is likely to require a reduction step. The functions of a known ferric reductase, CG8399, and a candidate ferric reductase, CG1275, will be studied. 2A) RNAi will be used to determine whether CG8399 or CG1275 contribute to cell surface ferric reductase activity. 2B) RNAi will be used to determine whether the activity of CG8399 or CG1275 influences the iron content of cells. 2C) A membrane-impermeant ferrous chelator will be evaluated for its ability to inhibit iron uptake.