response to iron ion

Definition

Target type: biologicalprocess

Any process that results in a change in state or activity of a cell or an organism (in terms of movement, secretion, enzyme production, gene expression, etc.) as a result of an iron ion stimulus. [GOC:sm]

Iron ion response is a complex biological process that involves the regulation of iron uptake, storage, and utilization in cells. It is essential for various cellular functions, including oxygen transport, DNA synthesis, and enzymatic activity. Here's a detailed breakdown of the process:

1. **Iron Uptake:**
- **Transferrin-mediated iron uptake:** The majority of iron in the blood is bound to transferrin, a protein that transports iron to cells. Cells possess transferrin receptors (TfRs) on their surface that bind to transferrin-iron complexes. This binding triggers endocytosis, internalizing the transferrin-iron complex into the cell. Inside the cell, the iron is released from transferrin and transported to other cellular compartments.
- **Non-transferrin-bound iron uptake:** A small amount of iron can enter cells directly through the cell membrane via divalent metal transporter 1 (DMT1). This pathway is less efficient than transferrin-mediated uptake but plays a crucial role in iron absorption from the diet.

2. **Iron Storage and Regulation:**
- **Ferritin:** Iron is stored within cells in the form of ferritin, a protein complex that sequesters iron safely and prevents it from generating harmful free radicals. The levels of ferritin in cells are regulated by the iron regulatory proteins (IRP1 and IRP2), which bind to iron regulatory elements (IREs) in the mRNA of ferritin and other iron-related proteins. When iron levels are high, IRPs are unable to bind to IREs, leading to increased ferritin synthesis and iron storage.
- **Hepcidin:** This hormone produced by the liver plays a central role in regulating iron homeostasis. Hepcidin binds to ferroportin, a protein responsible for exporting iron from cells, leading to its degradation and reduced iron release. Increased hepcidin levels are associated with iron deficiency, while decreased hepcidin levels are associated with iron overload.

3. **Iron Utilization:**
- **Hemoglobin synthesis:** Iron is a crucial component of hemoglobin, the protein responsible for oxygen transport in red blood cells. Iron deficiency can lead to anemia, characterized by a reduction in red blood cells and hemoglobin.
- **Enzyme cofactor:** Iron acts as a cofactor for numerous enzymes involved in various metabolic pathways, including mitochondrial respiration, DNA synthesis, and antioxidant defense.

4. **Iron Sensing Mechanisms:**
- **IRE/IRP system:** The iron regulatory proteins (IRP1 and IRP2) and iron regulatory elements (IREs) play a crucial role in sensing iron levels within cells. When iron levels are low, IRPs bind to IREs, leading to increased expression of proteins involved in iron uptake and decreased expression of proteins involved in iron storage. Conversely, high iron levels lead to the release of IRPs from IREs, resulting in decreased iron uptake and increased iron storage.
- **Other sensing mechanisms:** Several other mechanisms are involved in iron sensing, including the regulation of transcription factors like HIF-1α and the activation of signaling pathways like the MAPK pathway.

Iron ion response is a finely tuned process that ensures the appropriate levels of iron are available for cellular function while preventing iron toxicity. Dysregulation of this process can lead to various pathological conditions, including anemia, iron overload disorders, and neurodegenerative diseases.'
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Proteins (8)

Compounds (530)