Pilot Studies of Two Possible Iron Uptake Mechanisms in Insect Cells

Abstract

Iron plays an important role in energy metabolism and other essential physiological processes; however, because iron can also be toxic, its uptake by cells must be strictly regulated. In humans, there is a well‐understood pathway of iron uptake and multiple poorly understood pathways. How iron is transported into insect cells is unknown. The goal of this study was to test two models of iron uptake by cultured insect cells. The first model involves endocytic uptake of protein‐bound iron. The second model involves uptake of iron through a ferrous transporter. For our first set of experiments, we used the well‐studied Drosophila melanogaster S2 cell line. We found that S2 cells express rab5 (an essential component of endosomes), secreted ferritin, membrane‐bound transferrin, two ferric reductases, and a ferrous transporter. Treating cells with endocytosis inhibitors had no effect on iron content; therefore, endocytosis does not seem to be required for iron uptake by S2 cells. In contrast, sequestering iron with a ferrous chelator decreased the iron content of treated cells, suggesting that the ferrous form of iron is involved in the uptake process. We wanted to take advantage of a newly developed chemically defined medium (ZB) to learn more about the mechanism of iron uptake, but we were unable to grow S2 cells in ZB medium. We found that Kc167 and Cl.8 cells, which do grow in ZB medium, express the same set of iron‐related genes as S2 cells. To test the hypothesis that endocytosis is involved in iron uptake by D. melanogaster cells, we are in the process of evaluating the effect of RNAi‐mediated knockdown of rab5 on cellular iron content. Toward this goal, we have synthesized dsRNA that targets rab5 and optimized a method to measure cellular iron content. To test the hypothesis that a ferrous transporter is involved in iron uptake, we will measure the effect of RNAi‐mediated knockdown of divalent metal transporter 1 (DMT1) on cellular iron content. Our tentative conclusion is that insect cells take up iron via a mechanism that involves a ferrous transporter. A better understanding of iron uptake in insects could lead to better insect control strategies and also provide insight into the less understood iron uptake mechanisms of humans.Support or Funding InformationNSF IOS 1656388This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.