Iron Regulatory Protein 1 Inhibits Ferritin Translation Responding to OsHV-1 Infection in Ark Clams, Scapharca Broughtonii

A Putative Receptor for Ferritin in Mollusks: Characterization of the Insulin-like Growth Factor Type 1 Receptor

The ferritin secreted by mammals has been well documented, with the protein capable of localizing to cell membranes and facilitating the delivery of iron to cells through endocytosis. However, the presence of ferritin in the circulatory fluid of mollusks and its functions remain largely unknown. In this study, we aimed to investigate the potential interacting proteins of ferritin in the ark clam (SbFn) through the use of a pull-down assay. Our findings revealed the presence of an insulin-like growth factor type 1 receptor (IGF-1R) in ark clams, which was capable of binding to SbFn and was named SbIGF-1R. SbIGF-1R was found to be composed of two leucine-rich repeat domains (L domain), a cysteine-rich domain, three fibronectin type III domains, a transmembrane domain, and a tyrosine kinase domain. The ectodomain of SbIGF-1R was observed to form a symmetrical antiparallel homodimer in the shape of the letter 'A', with the fibronectin type III domains serving as its 'legs'. The mRNA expression of SbIGF-1R gene was detected ubiquitously in various tissues of the ark clam, with the highest expression levels found in hemocytes, as determined by qRT-PCR. Using a confocal microscopic and yeast two-hybrid assays, the interaction between SbIGF-1R and SbFn was further verified. The results showed that SbFn co-localized with SbIGF-1R on the cell membrane, and their interaction was expected to occur on the FNIII domains of the SbIGF-1R. In conclusion, our findings highlight the identification of a putative receptor, SbIGF-1R, for SbFn, demonstrating the versatility of IGF-1R in ark clams.

The Role of Ferritin in Health and Disease: Recent Advances and Understandings

Systemic iron homeostasis needs to be tightly controlled, as both deficiency and excess iron cause major global health concerns, such as iron deficiency anemia, hemochromatosis, etc. In mammals, sufficient dietary acquisition is critical for fulfilling the systemic iron requirement. New questions are emerging about whether and how cellular iron transport pathways integrate with the iron storage mechanism. Ferritin is the intracellular iron storage protein that stores surplus iron after all the cellular needs are fulfilled and releases it in the face of an acute demand. Currently, there is a surge in interest in ferritin research after the discovery of novel pathways like ferritinophagy and ferroptosis. This review emphasizes the most recent ferritin-related discoveries and their impact on systemic iron regulation.