Abstract
Ferritins are conserved iron-binding proteins that are primarily involved in iron storage, detoxification and the immune response. Despite the importance of ferritin in organisms, little is known about their roles in the eri-silkworm (Samia cynthia ricini). We previously identified a ferritin heavy chain subunit named ScFerHCH in the S. c. ricini transcriptome database. The full-length S. c. ricini ferritin heavy chain subunit (ScFerHCH) was 1863 bp and encoded a protein of 231 amino acids with a deduced molecular weight of 25.89 kDa. Phylogenetic analysis revealed that ScFerHCH shared a high amino acid identity with the Bombyx mori and Danaus plexippus heavy chain subunits. Higher ScFerHCH expression levels were found in the silk gland, fat body and midgut of S. c. ricini by reverse transcription quantitative polymerase chain reaction (RT-qPCR) and Western blotting. Injection of Staphylococcus aureus and Pseudomonas aeruginosa was associated with an upregulation of ScFerHCH in the midgut, fat body and hemolymph, indicating that ScFerHCH may contribute to the host’s defense against invading pathogens. In addition, the anti-oxidation activity and iron-binding capacity of recombinant ScFerHCH protein were examined. Taken together, our results suggest that the ferritin heavy chain subunit from eri-silkworm may play critical roles not only in innate immune defense, but also in organismic iron homeostasis.
Highlights
Iron is an essential nutrient element for almost all living organisms, including hosts and invaders [1], because of its important role in various biological processes, including growth and differentiation, oxygen transport and storage, DNA synthesis and the cell cycle
The tight regulation of iron metabolism maintains a balance between its benefits and toxic effects, and it is accomplished by the iron-binding proteins (IBPs) such as transferrin and ferritin
The results revealed that synthesis of ferritin heavy chain homologs (HCHs) subunit mRNAs may be important under conditions of iron overload due to the absence of an iron responsive element (IRE) [25]
Summary
Iron is an essential nutrient element for almost all living organisms, including hosts and invaders [1], because of its important role in various biological processes, including growth and differentiation, oxygen transport and storage, DNA synthesis and the cell cycle. Ferritin is a 450-kDa storage protein that was first identified in the midgut epithelial cells of Philaenus spumarius [9] This protein is ubiquitous in a wide variety of organisms, including bacteria, fungi, invertebrates and vertebrates, showing several conserved features [10,11,12,13]. Otho et al identified a silkworm ferritin one heavy chain that played a crucial role in regulating the haemolymph iron homeostasis in defense against bacterial infection [24]. Our results suggest that ScFerHCH is likely to play an important role in iron storage, antioxidation, and innate immune defense against pathogens in S. c. These results will lay a foundation for further characterization of ScFerHCH functions
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