Lysosomal degradation of ferritin found crucial to iron homeostasis

A study published by the Harvard Medical School, Dana-Farber Cancer Institute and Beth Israel Deaconess Medical Center demonstrated a lysosome-dependent mechanism for iron storage and release in cells, according to medicalxpress.com .

Although cells need iron, especially red blood cells that depend on iron (II) to carry oxygen, too much iron free radicals lose in the cells can cause iron overload that transfers to and damages organs. A more complete analysis of iron-related health concerns can be found  in Jane Brody's New York Times health blog article published in 2012, "A Host of Ills When Iron’s Out of Balance."

The basic science behind the maintenance of iron levels can be traced to ferritin, a protein that surrounds unused iron ions and stores them. 

This diagram, retrieved on April 2nd from the Memorial University of Newfoundland Website shows the production of the ferritin, which is regulated by an iron-activated regulator protein. In the picture on the left (a), the active IRE binding protein is blocking the expression of the iron response element. In the picture on the right (b), when iron levels are high, iron binds to the active IRE binding protein, changing it's shape and causing it to detach from the mRNA. The mRNA that follows it, the ferritin encoding sequence, is then expressed in order to bind and store the iron.

However, the new study published in Nature looks at the next stage, after expression of the ferritin protein, when iron levels decrease. After someone has been seriously injured, given blood, or even menstruated, iron levels can become low. The cell then requires a mechanism to retrieve iron from the ferritin protein.

The study suggests that phagocytosis occurs as the lysosome digests the ferritin protein to release the iron contained within its cage-like structure. The scientists also found the cargo carrier that constitutes the ferritin's specific pathway of ferritin to lysosomal degradation.

Read Elizabeth Cooney's medicalxpress article for more information. Additionally, the abstract and images are available from nature.com.