Conservative and Atypical Ferritins of Sponges

Abstract

Ferritins comprise a conservative family of proteins found in all species and play an essential role in resistance to redox stress, immune response, and cell differentiation. Sponges (Porifera) are the oldest Metazoa that show unique plasticity and regenerative potential. Here, we characterize the ferritins of two cold-water sponges using proteomics, spectral microscopy, and bioinformatic analysis. The recently duplicated conservative HdF1a/b and atypical HdF2 genes were found in the Halisarca dujardini genome. Multiple related transcripts of HpF1 were identified in the Halichondria panicea transcriptome. Expression of HdF1a/b was much higher than that of HdF2 in all annual seasons and regulated differently during the sponge dissociation/reaggregation. The presence of the MRE and HRE motifs in the HdF1 and HdF2 promotor regions and the IRE motif in mRNAs of HdF1 and HpF indicates that sponge ferritins expression depends on the cellular iron and oxygen levels. The gel electrophoresis combined with specific staining and mass spectrometry confirmed the presence of ferric ions and ferritins in multi-subunit complexes. The 3D modeling predicts the iron-binding capacity of HdF1 and HpF1 at the ferroxidase center and the absence of iron-binding in atypical HdF2. Interestingly, atypical ferritins lacking iron-binding capacity were found in genomes of many invertebrate species. Their function deserves further research.

Structural and Functional Insights into the Roles of Potential Metal-Binding Sites in Apostichopus japonicus Ferritin

“…Ferritin has been widely reported in vertebrates and gradually studied in invertebrates. The 3D structures of ferritins for most species exhibit many similarities; however, in contrast to mammalian ferritins, there are some exceptions for ferritins in invertebrate species [7]. For instance, although both Fer147 and PeFer stemmed from the marine invertebrate Phascolosoma esculenta, the interiors of their three-and four-fold channels were significantly distinct in terms of amino acid composition and electrostatic potential distribution [13].…”

“…Notably, the superfamily of these proteins is usually classified into three different types, i.e., classical ferritins, heme-binding bacterioferritins (Bfr), and DNA-binding proteins from starved cells (Dps) [6]. The typical form of most common ferritins presents as a spherical protein composed of 24 identical or similar subunits with a molecular weight (MW) of ~450−500 kDa [7]. In eukaryotes, ferritin is generally formed by self-assembly with two or three types of highly homologous subunits, namely heavy (H, 21 kDa), middle (M, 20 kDa), and light (L, 19 kDa) chains, in which the M subunit contains both the ferroxidase center and the ferrihydrite nucleation center, in stark contrast to the H and L subunits [4,6].…”

“…Of course, after uptake, the Fe 2+ ions are transported by a series of metal-binding residues toward a specific catalytic site, which is known as the di-iron ferroxidase center and is situated in the subunit four-helix bundle [5,9,[13][14][15]. However, although the amino acid residues located at the ferroxidase center seem to be highly conserved in most eukaryotic ferritins [7,9], the ferroxidase reaction rate may vary. For instance, De Meulenaere et al found that the ferroxidase velocity of the marine invertebrate Chaetopterus ferritin (ChF) was up to eight times faster than that of HuHF, which is known as a conventionally accepted representative ferritin [15].…”

Prognostic Value of Serum Ferritin for Patients with Severe Fever with Thrombocytopenia Syndrome: A Single-Center Retrospective Cohort Study

“…In addition to long-term use as an alternative indicator of iron storage in the body, FER also represents an acute phase protein, which is upregulated and elevated in infectious and noninfectious inflammation [10], including chronic kidney disease [11], diabetes [12], malignant tumors [13] and inflammation [14,15]. Furthermore, there is growing evidence that circulating ferritin may play a pathogenic role in inflammatory diseases through its signal transduction as part of innate immune response and regulation of lymphocyte function [16,17]. Consequently, FER may be a useful biomarker due to its accessibility and correlation with significant inflammatory response secondary to infection.…”

Special Issue: Structure, Function and Evolution of Protein Domains

“…Adameyko et al [ 1 ] performed detailed research on the ferritin family of sponges ( Porifera ), the oldest Metazoa that exhibit unique morphological plasticity and reversible cellular aggregation. Ferritins constitute a conservative family of proteins present ubiquitously in all species and that play important roles in immune response, redox stress, and cellular differentiation.…”