Molecular characterization and expression analysis of regucalcin in disk abalone (Haliotis discus discus): intramuscular calcium administration stimulates the regucalcin mRNA expression

Protective mechanisms of three antioxidants against T-2 toxin-induced muscle protein deterioration in shrimp

BACKGROUND

Quercetin (Q), tea polyphenols (TP), and rutin (R) are widely used plant-derived active ingredients. They possess antioxidant, anti-inflammatory, and anti-tumor properties, and can reduce the muscle damage caused by mycotoxins. However, few studies have examined the protective mechanisms of quercetin, tea polyphenols, and rutin on muscle quality. To elucidate their protective mechanisms, shrimp were exposed to both T-2 toxin and these three antioxidants for 20 days in a dose-escalating trial. The changes in the protein composition of shrimp muscle were measured. The target proteins associated with T-2 and antioxidants were screened and identified by non-labeled quantitative proteomics.

RESULTS

The T-2 toxin induced abnormal expression of 21 target proteins, leading to the deterioration of muscle proteins in shrimp. The three antioxidants ameliorated the T-2 toxin-induced damage to muscle proteins by increasing the sarcoplasmic and myofibrillar protein content and decreasing the alkali-soluble protein content. Quercetin had the strongest protective effect. The protective processes of these antioxidants involved the upregulation of target proteins involved in carbohydrate metabolism (enolase, malate dehydrogenase), protein translation (elongation factor 1-alpha and eukaryotic translation initiation factor 2 subunit alpha), and cytoskeleton component (actin 2, fast-type skeletal muscle actin 1). Quercetin regulated the largest number of target proteins, making it the best protective agent against T-2 toxin.

CONCLUSION

The T-2 toxin (4.80-24.30 mg/kg feed) induced changes in target proteins and muscle composition of shrimp, leading to a deterioration in muscle proteins. Quercetin (2.00-32.00 g/kg feed) had significant protective effects against this deterioration in muscle protein in shrimp. © 2022 Society of Chemical Industry.

The involvement of a regucalcin in suppressing hemocyte apoptosis in Pacific oyster Crassostrea gigas

Regucalcin (RGN), also known as senescence marker protein-30 (SMP30), plays a vital role in the regulation of Ca²⁺ homeostasis. In the present study, a regucalcin (designated as CgRGN) was identified from Pacific oyster Crassostrea gigas. The complete cDNA sequence of CgRGN was of 1059 bp, containing an open reading frame of 933 bp which encoded a protein of 310 amino acids. The deduced amino acid sequence of CgRGN shared similarity with other RGNs from the genome of C. gigas as well as other species. The mRNA transcripts of CgRGN were universally detected in all tested tissues, with higher level in hepatopancreas, labial palp, and gills. The relative expression level of CgRGN in hemocytes was significantly up-regulated (p < 0.05) at 3, 12, 72, and 96 h after the stimulation of lipopolysaccharide (LPS). After CgRGN expression was interfered by specific CgRGN-dsRNA, the hemocytes apoptosis rate increased dramatically at 12 h post LPS stimulation (1.56 fold, p < 0.01), compared to the control group. The caspase-3 activity in hemocytes and NO concentration in hemolymph increased significantly (p < 0.05) in dsCgRGN injection oysters. These results collectively indicated that CgRGN could suppress LPS-induced apoptosis and be involved in the immune response of oysters.

Physicochemical Properties of Chilled Abalone as Influenced by Washing Pretreatment in Citric Acid Combined with High Pressure Processing

Citric acid pretreatment (2% and 4% citric acid) and high pressure processing (200–400 MPa for 3 min) were conducted to elucidate quality characteristics and shelf life of abalone during chilled storage. Physicochemical properties, total volatile basic nitrogen (TVB-N), and total viable count (TVC) were used as indicators of quality and the shelf life of abalone. Citric acid pretreatment caused a decrease in pH and lightness, and 4% citric acid pretreatment exhibited a positive effect on TVB-N and TVC. Pressurization suppressed the formation of TVB-N and the growth of TVC in abalone. However, excessive modification in physicochemical properties of abalone resulted from processing at a pressure higher than 300 MPa. To achieve microbial inactivation without severe modification in abalone quality, citric acid pretreatment with high pressure processing offered a potential advantage in maintaining characteristics of chilled abalone during prolonged storage period.

The role of regucalcin in bone homeostasis: involvement as a novel cytokine

Regucalcin, which was discovered as a calcium-binding protein in 1978, has been demonstrated to play a multifunctional role in the regulation of various tissues and cell types. Regucalcin plays a pivotal role in the regulation of intracellular calcium homeostasis, various enzyme activities, cell signal transduction, nuclear function and gene expression, and cell proliferation and apoptosis. Moreover, regucalcin has been found to play a role in the regulation of bone homeostasis. Overexpression of regucalcin induces bone loss in regucalcin transgenic rats in vivo and deficiency causes osteomalacia in vivo. Regucalcin mRNA and its protein are expressed in rat femoral tissues, bone marrow cells, and osteoblastic cells. Exogenous regucalcin has suppressive effects on the differentiation and mineralization of osteoblastic MC3T3-E1 cells and stimulates osteoclastogenesis in mouse bone marrow culture in vitro. Moreover, regucalcin has been found to suppress osteoblastogenesis and stimulate adipogenesis in the bone marrow culture system in vitro. Regucalcin shows enhancing effects on activation of NF-κB, which is mediated through tumor necrosis factor-α (TNF-α) or the receptor activator of the NF-κB ligand (RANKL) in preosteoblastic cells and preosteoclastic cells. Exogenous regucalcin may play a pivotal role in the regulation of bone homeostasis as a suppressor in osteoblastogenesis and an enhancer in osteoclastogenesis, suggesting its role as a cytokine.

The diverse roles of calcium-binding protein regucalcin in cell biology: from tissue expression and signalling to disease

Regucalcin (RGN) is a calcium (Ca(2+))-binding protein widely expressed in vertebrate and invertebrate species, which is also known as senescence marker protein 30, due to its molecular weight (33 kDa) and a characteristically diminished expression with the aging process. RGN regulates intracellular Ca(2+) homeostasis and the activity of several proteins involved in intracellular signalling pathways, namely, kinases, phosphatases, phosphodiesterase, nitric oxide synthase and proteases, which highlights its importance in cell biology. In addition, RGN has cytoprotective effects reducing intracellular levels of oxidative stress, also playing a role in the control of cell survival and apoptosis. Multiple factors have been identified regulating the cell levels of RGN transcripts and protein, and an altered expression pattern of this interesting protein has been found in cases of reproductive disorders, neurodegenerative diseases and cancer. Moreover, RGN is a serum-secreted protein, and its levels have been correlated with the stage of disease, which strongly suggests the usefulness of this protein as a potential biomarker for monitoring disease onset and progression. The present review aims to discuss the available information concerning RGN expression and function in distinct cell types and tissues, integrating cellular and molecular mechanisms in the context of normal and pathological conditions. Insight into the cellular actions of RGN will be a key step towards deepening the knowledge of the biology of several human diseases.

Identification and in silico analysis of a novel troponin C like gene from Ruditapes philippinarum (Bivalvia: Veneridae) and its transcriptional response for calcium challenge

Troponin C (TnC) is one of the subunits composing the troponin complex, which is primarily expressed in muscle tissue and plays a major role in regulating contractility. We have identified a novel TnC-like gene (RpTnC) from the Ruditapes philippinarum Manila clam. Sequence analysis indicated that RpTnC has a 450bp coding sequence, encoding a 150 amino acid protein with a molecular mass of 17.4 kDa. The RpTnC protein consisted of four EF-hand motifs (I-IV), each with a Ca2+-binding site. In silico comparative analysis of protein sequence showed that only site IV, demonstrating a conserved stretch (DxDxSx6E), is functionally active for Ca2+-coordination. Moreover, RpTnC was homologically (61.3% identity) and phylogenetically closest to Japanese flying squid TnC. The mRNA expression analysis using quantitative real-time PCR revealed a differential basal-expression of RpTnC transcripts in six different clam tissues, with higher levels in adductor muscle and mantle. Intramuscular administration of CaCl2 caused a prominent upregulation of RpTnC transcripts in adductor muscle (~5 fold). Collectively, our findings suggest that the TnC homolog of Manila clam identified in this study may be involved in important role(s) in clam physiology, mainly in its muscle tissues, and its transcription could be significantly influenced by increased Ca2+ levels.

Senescence marker protein 30 (SMP30)/regucalcin (RGN) expression decreases with aging, acute liver injuries and tumors in zebrafish

Senescence marker protein 30 (SMP30)/regucalcin (RGN) is known to be related to aging, hepatocyte proliferation and tumorigenesis. However, expression and function of non-mammalian SMP30/RGN is poorly understood. We found that zebrafish SMP30/RGN mRNA expression decreases with aging, partial hepatectomy and thioacetamide-induced acute liver injury. SMP30/RGN expression was also greatly decreased in a zebrafish liver cell line. In addition, we induced liver tumors in adult zebrafish by administering diethylnitrosamine. Decreased expression was observed in foci, hepatocellular carcinomas, cholangiocellular carcinomas and mixed tumors as compared to the surrounding area. We thus showed the importance of SMP30/RGN in liver proliferation and tumorigenesis.

The transcriptional regulation of regucalcin gene expression

Regucalcin, which is discovered as a calcium-binding protein in 1978, has been shown to play a multifunctional role in many tissues and cell types; regucalcin has been proposed to play a pivotal role in keeping cell homeostasis and function for cell response. Regucalcin and its gene are identified in over 15 species consisting of regucalcin family. Comparison of the nucleotide sequences of regucalcin from vertebrate species is highly conserved in their coding region with throughout evolution. The regucalcin gene is localized on the chromosome X in rat and human. The organization of rat regucalcin gene consists of seven exons and six introns and several consensus regulatory elements exist upstream of the 5'-flanking region. AP-1, NF1-A1, RGPR-p117, β-catenin, and other factors have been found to be a transcription factor in the enhancement of regucalcin gene promoter activity. The transcription activity of regucalcin gene is enhanced through intracellular signaling factors that are mediated through the phosphorylation and dephosphorylation of nuclear protein in vitro. Regucalcin mRNA and its protein are markedly expressed in the liver and kidney cortex of rats. The expression of regucalcin mRNA in the liver and kidney cortex has been shown to stimulate by hormonal factors (including calcium, calcitonin, parathyroid hormone, insulin, estrogen, and dexamethasone) in vivo. Regucalcin mRNA expression is enhanced in the regenerating liver after partial hepatectomy of rats in vivo. The expression of regucalcin mRNA in the liver and kidney with pathophysiological state has been shown to suppress, suggesting an involvement of regucalcin in disease. Liver regucalcin expression is down-regulated in tumor cells, suggesting a suppressive role in the development of carcinogenesis. Liver regucalcin is markedly released into the serum of rats with chemically induced liver injury in vivo. Serum regucalcin has a potential sensitivity as a specific biochemical marker of chronic liver injury with hepatitis. Regucalcin has been proposed to be a key molecule in cellular regulation and metabolic disease.

Regucalcin and metabolic disorders: osteoporosis and hyperlipidemia are induced in regucalcin transgenic rats

Regucalcin transgenic (TG) rat has been generated to determine the role in metabolic disorders. Regucalcin homozygote male and female rats induce a prominent increase in regucalcin protein in the various tissues. Bone loss has been found to induce in regucalcin TG rats with growing (5 weeks old) and aging (50 weeks old). Osteoclastogenesis has been shown to stimulate in culture with the bone marrow cells obtained from regucalcin TG rats. Exogenous regucalcin stimulates osteoclastogenesis in mouse marrow culture in vitro. Regucalcin has a suppressive effect on the differentiation and mineralization in osteoblastic MC3T3-E1 cells in vitro. The mechanism by which regucalcin TG rat induces bone loss may result from the enhancement of osteoclastic bone resorption and the suppression of osteoblastic bone formation. Moreover, regucalcin TG rat has been found to induce hyperlipidemia with increasing age (14-50 weeks); serum triglyceride, high-density lipoprotein (HDL)-cholesterol, free fatty acid, albumin and calcium concentrations are markedly increased in regucalcin TG male and female rats with increasing age. The decrease in lipid and glycogen contents in liver tissues is induced in regucalcin TG rats. The gene expression of leptin and adiponectin is suppressed in the TG rats. Overexpression of regucalcin has been shown to enhance glucose utilization and lipid production in the cloned rat hepatoma H4-II-E cells in vitro, and insulin resistance is seen in the cells. The expression of glucose transporter 2 mRNA is increased in the transfectants, while it has been shown to suppress insulin receptor and phosphatidylinositol 3-kinase mRNA expressions that are involved in insulin signaling. This review proposes that regucalcin relates in osteoporosis and hyperlipidemia, and that the regucalcin TG rat model may be useful in determining the pathophysiologic state and the development of therapeutic tool for osteoporosis and hyperlipidemia.

[Progresses on immune-related genes and proteins of abalones]

Abalones, belonging to one of the largest marine gastropod mollusks, are economically important seafood in aquaculture worldwide. In recent years, bacterial epidemic infection has been reported in China and other countries, and mass mortality in abalones causes significant economic losses. Immune-related genes and proteins of abalones are seldom reported. However, these functional molecules may play a key role in resisting diseases and maintaining healthy status and are pivotal for studying immunological mechanisms. Here we summarized the advanced research and progresses in abalone immune-related genes and proteins with the purpose of facilitating future study of these target molecules involved in immunological mechanisms.

The secreted salivary proteome of the pea aphid Acyrthosiphon pisum characterised by mass spectrometry

Nine proteins secreted in the saliva of the pea aphid Acyrthosiphon pisum were identified by a proteomics approach using GE-LC-MS/MS and LC-MS/MS, with reference to EST and genomic sequence data for A. pisum. Four proteins were identified by their sequences: a homolog of angiotensin-converting enzyme (an M2 metalloprotease), an M1 zinc-dependant metalloprotease, a glucose-methanol-choline (GMC)-oxidoreductase and a homolog to regucalcin (also known as senescence marker protein 30). The other five proteins are not homologous to any previously described sequence and included an abundant salivary protein (represented by ACYPI009881), with a predicted length of 1161 amino acids and high serine, tyrosine and cysteine content. A. pisum feeds on plant phloem sap and the metalloproteases and regucalcin (a putative calcium-binding protein) are predicted determinants of sustained feeding, by inactivation of plant protein defences and inhibition of calcium-mediated occlusion of phloem sieve elements, respectively. The amino acid composition of ACYPI009881 suggests a role in the aphid salivary sheath that protects the aphid mouthparts from plant defences, and the oxidoreductase may promote gelling of the sheath protein or mediate oxidative detoxification of plant allelochemicals. Further salivary proteins are expected to be identified as more sensitive MS technologies are developed.

Novel protein RGPR-p117: its role as the regucalcin gene transcription factor

RGPR-p117 was originally discovered as a novel protein that binds to a nuclear factor I (NFI) consensus motif TTGGC(N)(6)CC, which is present in the 5'-flanking region of the regucalcin gene (rgn). RGPR-p117 has been identified in human, rat, mouse, bovine, rabbit, and chicken livers. Phylogenetic analysis of six vertebrates shows that RGPR-p117 appears to form a single cluster, indicating a common evolutionary relationship of the RGPR-p117 family. The RGPR-p117 gene consists of at least 26 exons spanning approximately 4.1 kbp and is localized on human chromosome 1q25.2. RGPR-p117 mRNA is expressed in the liver, kidney, heart, spleen, and brain of rats. RGPR-p117 mRNA expression is stimulated through signaling mechanisms. Mammalian RGPR-p117 conserves a leucine zipper motif, which is present in many gene regulatory proteins. RGPR-p117 has been shown to translocate from the cytoplasm to the nucleus in NRK52E cells, a process which is mediated through protein kinase C signaling following hormonal stimulation. The phosphorylated RGPR-p117 binds to the TTGGC motif in the promoter region of the regucalcin gene and enhances regucalcin mRNA expression in the cells, indicating a role as a transcriptional factor. RGPR-p117 is also localized in the plasma membranes, nucleus, mitochondria, microsomes, and cytoplasm. Overexpression of RGPR-p117 has been found to induce a significant decrease in protein and DNA contents in cells, suggesting that RGPR-p117 may regulate the gene expression of other related proteins as well as the transcription factor. Also, overexpression of RGPR-p117 has a suppressive effect on cell death by inhibiting the gene expression of caspase-3, caspase-8, and Fas-associating death domain protein whose TTGGC motif is present in the promoter region of their genes. The novel protein RGPR-p117 has been shown to play an important role as a transcription factor.