ferritinbound

Ferritinbound refers to iron that is stored within ferritin, the intracellular protein complex that sequesters iron in a safe, non-toxic form. In many organisms, ferritin forms a hollow, spherical shell made of 24 subunits that can house thousands of iron atoms as a ferrihydrite-like core. This ferritin-bound iron serves as a readily mobilizable reserve that can be accessed when cellular iron demand rises.

Iron enters ferritin through regulated oxidation and mineralization, and it can be released when needed. Mobilization often involves ferritinophagy, a process in which ferritin is delivered to lysosomes in an NCOA4-dependent manner, followed by release of Fe2+ into the cytosol for incorporation into metabolic processes such as heme and nucleotide synthesis. The overall balance of ferritin-bound iron is linked to broader iron homeostasis, including the activity of ferroportin and intracellular iron pools.

Regulation of ferritin synthesis and iron storage is tightly controlled. Ferritin mRNA contains iron-responsive elements that are bound by iron regulatory proteins; high cellular iron promotes ferritin translation, increasing the ferritin-bound iron pool. Inflammation and liver disease can elevate ferritin levels independently of iron stores, reflecting ferritin’s role as an acute-phase protein.

Clinical relevance is often linked to serum ferritin, a common proxy for body iron stores, though it is influenced by inflammation and other conditions. The concept of ferritinbound emphasizes the distinction between stored iron within ferritin and circulating forms such as transferrin-bound iron. In research, distinguishing ferritin-bound iron from other iron pools helps characterize iron metabolism and storage dynamics.