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Yamaguchi M, Murata T, Ramos JW. The calcium channel agonist Bay K 8644 promotes the growth of human liver cancer HepG2 cells in vitro: suppression with overexpressed regucalcin. Mol Cell Biochem 2020; 472:173-185. [PMID: 32591915 DOI: 10.1007/s11010-020-03795-7] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2020] [Accepted: 06/13/2020] [Indexed: 10/24/2022]
Abstract
Hepatocellular carcinoma is one of the most prevalent malignant diseases and causes a third of cancer-related death. The consequences of altered calcium homeostasis in cancer cells may contribute to tumor progression. Regucalcin plays an inhibitory role in calcium signaling linked to transcription regulation. Regucalcin gene expression is downregulated in the tumor tissues of liver cancer patients, suggesting an involvement as a suppressor in hepatocarcinogenesis. We investigated whether Bay K 8644, an agonist of the L-type Ca2+ channel, promotes the growth of human liver cancer and if the effect of Bay K 8644 is suppressed by overexpressed regucalcin using the HepG2 cell model. The colony formation and growth of HepG2 cells were promoted by culturing with Bay K 8644 (0.1-10 nM). This effect was suppressed by inhibitors of signaling processes linked to cell proliferation, including PD98059 and wortmannin. Death of HepG2 cells was stimulated by Bay K 8644 with higher concentrations (25 and 100 nM). The effects of Bay K 8644 on cell growth and death were abolished by verapamil, an antagonist of calcium channel. Mechanistically, culturing with Bay K 8644 increased levels of mitogen-activated protein kinase (MAPK) and phospho-MAPK. Notably, overexpressed regucalcin suppressed Bay K 8644-promoted growth and death of HepG2 cells. Furthermore, overexpressed regucalcin prevented growth and increased death induced by thapsigargin, which induces the release of intracellular stored calcium. Thus, higher regucalcin expression suppresses calcium signaling linked to the growth of liver cancer cells, providing a novel strategy in treatment of hepatocellular carcinoma with delivery of the regucalcin gene.
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MESH Headings
- 3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester/adverse effects
- Apoptosis
- Calcium Channel Agonists/adverse effects
- Calcium Channels, L-Type/chemistry
- Calcium-Binding Proteins/genetics
- Calcium-Binding Proteins/metabolism
- Carcinoma, Hepatocellular/etiology
- Carcinoma, Hepatocellular/metabolism
- Carcinoma, Hepatocellular/pathology
- Carcinoma, Hepatocellular/prevention & control
- Cell Proliferation
- Humans
- In Vitro Techniques
- Intracellular Signaling Peptides and Proteins/genetics
- Intracellular Signaling Peptides and Proteins/metabolism
- Liver Neoplasms/etiology
- Liver Neoplasms/metabolism
- Liver Neoplasms/pathology
- Liver Neoplasms/prevention & control
- Tumor Cells, Cultured
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Affiliation(s)
- Masayoshi Yamaguchi
- Cancer Biology Program, University of Hawaii Cancer Center, University of Hawaii at Manoa, 701 Ilalo Street, Honolulu, HI, 96813, USA.
| | - Tomiyasu Murata
- Laboratory of Analytical Neurobiology, Faculty of Pharmacy, Meijo University, Yagotoyama 150, Tempaku, Nagoya, 468-8503, Japan
| | - Joe W Ramos
- Cancer Biology Program, University of Hawaii Cancer Center, University of Hawaii at Manoa, 701 Ilalo Street, Honolulu, HI, 96813, USA
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2
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Vaz CV, Rodrigues DB, Socorro S, Maia CJ. Effect of extracellular calcium on regucalcin expression and cell viability in neoplastic and non-neoplastic human prostate cells. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2015; 1853:2621-8. [PMID: 26171977 DOI: 10.1016/j.bbamcr.2015.07.006] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/14/2015] [Revised: 07/06/2015] [Accepted: 07/10/2015] [Indexed: 01/14/2023]
Abstract
Extracellular calcium (Ca2+o) and its receptor, the Ca2+-sensing receptor (CaSR), play an important role in prostate physiology, and it has been shown that the deregulation of Ca2+ homeostasis and the overexpression of CaSR are involved in prostate cancer (PCa). Regucalcin (RGN), a Ca2+-binding protein that plays a relevant role in intracellular Ca2+ homeostasis, was identified as an under-expressed protein in human PCa. Moreover, RGN was associated with suppression of cell proliferation, suggesting that the loss of RGN may favor development and progression of PCa. This work aims to unveil the role of Ca2+o on RGN expression and viability of non-neoplastic (PNT1A) and neoplastic (LNCaP) prostate cell lines. It was demonstrated that Ca2+o up-regulates RGN expression in both cell lines, but important differences were found between cells for dose- and time-responses to Ca2+o treatment. It was also shown that high [Ca2+]o triggers different effects on cell proliferation of neoplastic and non-neoplastic PCa cells, which seems to be related with RGN expression levels. This suggests the involvement of RGN in the regulation of cell proliferation in response to Ca2+o treatment. Also, the effect of Ca2+o on CaSR expression seems to be dependent of RGN expression, which is strengthened by the fact that RGN-knockdown in PNT1A cells increases the CaSR expression, whereas transgenic rats overexpressing RGN exhibit low levels of CaSR. Overall, our results highlighted the importance of RGN as a regulatory protein in Ca2+-dependent signaling pathways and its deregulation of RGN expression by Ca2+o may contribute for onset and progression of PCa.
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Affiliation(s)
- Cátia V Vaz
- CICS-UBI - Health Sciences Research Centre, University of Beira Interior, Av. Infante D. Henrique, 6200-506 Covilhã, Portugal
| | - Daniel B Rodrigues
- CICS-UBI - Health Sciences Research Centre, University of Beira Interior, Av. Infante D. Henrique, 6200-506 Covilhã, Portugal
| | - Sílvia Socorro
- CICS-UBI - Health Sciences Research Centre, University of Beira Interior, Av. Infante D. Henrique, 6200-506 Covilhã, Portugal.
| | - Cláudio J Maia
- CICS-UBI - Health Sciences Research Centre, University of Beira Interior, Av. Infante D. Henrique, 6200-506 Covilhã, Portugal.
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3
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Marques R, Maia CJ, Vaz C, Correia S, Socorro S. The diverse roles of calcium-binding protein regucalcin in cell biology: from tissue expression and signalling to disease. Cell Mol Life Sci 2014; 71:93-111. [PMID: 23519827 PMCID: PMC11113322 DOI: 10.1007/s00018-013-1323-3] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2012] [Revised: 02/21/2013] [Accepted: 03/07/2013] [Indexed: 02/06/2023]
Abstract
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.
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Affiliation(s)
- Ricardo Marques
- CICS-UBI, Health Sciences Research Centre, University of Beira Interior, Covilhã, Portugal
| | - Cláudio J. Maia
- CICS-UBI, Health Sciences Research Centre, University of Beira Interior, Covilhã, Portugal
| | - Cátia Vaz
- CICS-UBI, Health Sciences Research Centre, University of Beira Interior, Covilhã, Portugal
| | - Sara Correia
- CICS-UBI, Health Sciences Research Centre, University of Beira Interior, Covilhã, Portugal
| | - Sílvia Socorro
- CICS-UBI, Health Sciences Research Centre, University of Beira Interior, Covilhã, Portugal
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4
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Regucalcin and cell regulation: role as a suppressor protein in signal transduction. Mol Cell Biochem 2011; 353:101-37. [DOI: 10.1007/s11010-011-0779-4] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2010] [Accepted: 03/07/2011] [Indexed: 12/23/2022]
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Yamaguchi M. The transcriptional regulation of regucalcin gene expression. Mol Cell Biochem 2010; 346:147-71. [PMID: 20936536 DOI: 10.1007/s11010-010-0601-8] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2010] [Accepted: 09/18/2010] [Indexed: 01/15/2023]
Abstract
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.
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Affiliation(s)
- Masayoshi Yamaguchi
- Division of Endocrinology and Metabolism and Lipids, Department of Medicine, Emory University School of Medicine, 101 Woodruff Circle, 1305 WMRB, Atlanta, GA 30322-0001, USA.
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6
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Doran P, Dowling P, Donoghue P, Buffini M, Ohlendieck K. Reduced expression of regucalcin in young and aged mdx diaphragm indicates abnormal cytosolic calcium handling in dystrophin-deficient muscle. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2006; 1764:773-85. [PMID: 16483859 DOI: 10.1016/j.bbapap.2006.01.007] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/11/2005] [Revised: 12/09/2005] [Accepted: 01/02/2006] [Indexed: 11/16/2022]
Abstract
The cytosolic Ca2+ -binding protein regucalcin is involved in intracellular signaling and present in high abundance in the liver. Here, we could show by comparative mass spectrometry-based proteomics screening of normal versus dystrophic fibres that regucalcin of 33.9 kDa and pI5.2 also exists in diaphragm muscle. Since the expression of sarcolemmal Ca2+ -leak channels and luminal Ca2+ -binding elements is altered in dystrophin-deficient muscle, we initiated this study in order to determine whether additional soluble muscle proteins involved in Ca2+ -handling are affected in muscular dystrophy. Following separation by two-dimensional gel electrophoresis, the spot pattern of the normal versus the mdx diaphragm muscle proteome was evaluated by densitometry. The expression levels of 20 major protein spots were shown to change and their identity determined by mass spectrometry. A 2-fold reduction of regucalcin in mdx diaphragm, as well as in dystrophic limb muscle and heart, was confirmed by immunoblotting in both young and aged mdx mice. The results from our proteomics analysis of dystrophic diaphragm support the concept that abnormal Ca2+ -handling is involved in x-linked muscular dystrophy. The reduction in key Ca2+ -handling proteins may result in an insufficient maintenance of Ca2+ -homeostasis and an abnormal regulation of Ca2+ -dependent enzymes resulting in disturbed intracellular signaling mechanisms in dystrophinopathies.
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Affiliation(s)
- Philip Doran
- Department of Biology, National University of Ireland, Maynooth, Co. Kildare, Ireland
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7
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Bauer M, Hamm AC, Bonaus M, Jacob A, Jaekel J, Schorle H, Pankratz MJ, Katzenberger JD. Starvation response in mouse liver shows strong correlation with life-span-prolonging processes. Physiol Genomics 2004; 17:230-44. [PMID: 14762175 DOI: 10.1152/physiolgenomics.00203.2003] [Citation(s) in RCA: 123] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
We have monitored global changes in gene expression in mouse liver in response to fasting and sugar-fed conditions using high-density microarrays. From ∼20,000 different genes, the significantly regulated ones were grouped into specific signaling and metabolic pathways. Striking changes in lipid signaling cascade, insulin and dehydroepiandrosterone (DHEA) hormonal pathways, urea cycle and S-adenosylmethionine-based methyl transfer systems, and cell apoptosis regulators were observed. Since these pathways have been implicated to play a role in the aging process, and since we observe significant overlap of genes regulated upon starvation with those regulated upon caloric restriction, our analysis suggests that starvation may elicit a stress response that is also elicited during caloric restriction. Therefore, many of the signaling and metabolic components regulated during fasting may be the same as those which mediate caloric restriction-dependent life-span extension.
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Affiliation(s)
- Matthias Bauer
- Institut fuer Genetik, Forschungszentrum Karlsruhe, 76021 Karlsruhe, , Germany
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8
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Day JC, Bailey MJ. Structure and evolution of the luciferin-regenerating enzyme (LRE) gene from the firefly Photinus pyralis. INSECT MOLECULAR BIOLOGY 2003; 12:365-372. [PMID: 12864916 DOI: 10.1046/j.1365-2583.2003.00418.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
To study the structural features of genes for the luciferin-regenerating enzyme (LRE), the entire gene along with 524 bp of upstream sequence was determined from Photinus pyralis (Coleoptera: Lampyridae). The LRE gene revealed an open reading frame composed of five exons divided by four introns ranging in size from 47 to 904 bp. The deduced LRE amino acid sequence showed identity to senescence marker protein-30 (SMP30) from a number of insects and mammals including four putative SMP30 sequences from Anopheles gambiae. Gene structure comparisons showed some intron/exon site conservation with A. gambiae and mammalian SMP30 proteins but not Drosophila. LRE and luciferase sequence comparisons revealed two conserved putative luciferin-binding sites. The evolution of LRE was discussed in relation to its function.
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Affiliation(s)
- J C Day
- CEH-Oxford, Mansfield Road, Oxford OX1 3SR, UK.
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9
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Gomi K, Hirokawa K, Kajiyama N. Molecular cloning and expression of the cDNAs encoding luciferin-regenerating enzyme from Luciola cruciata and Luciola lateralis. Gene 2002; 294:157-66. [PMID: 12234677 DOI: 10.1016/s0378-1119(02)00764-3] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
In the firefly light organ, oxyluciferin, a product of the light-emitting reaction of firefly luciferase, is thought to be converted into luciferin. Previously, we isolated the luciferin-regenerating enzyme (LRE) from Photinus pyralis. LRE plays an important role in the recycling of oxyluciferin into luciferin. We have cloned two cDNAs encoding LRE, G-LRE and H-LRE, from poly(A)+ RNA of the lanterns of Luciola cruciata and Luciola lateralis, using reverse transcription-polymerase chain reaction, 5'-RACE (5'-rapid amplification of cDNA ends) and 3'-RACE. The putative translation products have molecular masses of 33,804 and 34,285 Da, corresponding to 309 and 307 amino acids, respectively. The deduced amino acid sequence of G-LRE shows 57 and 56% identity with H-LRE and A-LRE (P. pyralis), respectively. LRE (G-LRE, H-LRE, A-LRE) shows at most 39% amino acid sequence identity with insect anterior fat protein (AFP) and mammalian senescence marker protein-30 (SMP30). G-LRE and H-LRE were successfully expressed under the control of the lac promoter in Escherichia coli.
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Affiliation(s)
- Keiko Gomi
- Research and Development Division, Kikkoman Corporation, 399 Noda, Noda-shi, 278-0037, Chiba, Japan.
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10
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Abstract
Regucalcin was discovered in 1978 as a Ca(2+)-binding protein that does not contain EF-hand motif of Ca(2+)-binding domain [Yamaguchi, M., and Yamamoto T., Chem. Pharm. Bull. 26, 1915-1918, 1978]. The name regucalcin was proposed for this Ca(2+)-binding protein, which can regulate liver cell functions related to Ca(2+). Regucalcin has been demonstrated to play a multifunctional role in liver and kidney cells, for which regucalcin mRNA expression and its protein content are pronounced. Hepatic regucalcin mRNA expression has been shown to be mediated through signaling pathway of Ca(2+)/calmodulin-dependent protein kinase, protein kinase C, and tyrosine kinase. AP-1- and NF-1-like factors can bind to the promotor region of the rat regucalcin gene to mediate the Ca(2+) response for transcriptional activation. Growing evidence supports the view, moreover, that regucalcin plays an important role in the regulation of Ca(2+) signaling from the cytoplasm to nuclei in the proliferative cells of regenerating rat liver. Also, regucalcin has been demonstrated to be transported to liver nucleus, and it can inhibit nuclear protein kinase, protein phosphatase, and DNA and RNA synthesis in regenerating liver. Regucalcin plays a physiologic role in the control for overexpression of proliferative cells. Regucalcin has been proposed to be an important regulatory protein in nuclear signaling system.
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Affiliation(s)
- M Yamaguchi
- Laboratory of Endocrinology and Molecular Metabolism, Graduate School of Nutritional Sciences, University of Shizuoka, 52-1 Yada, Shizuoka, 422-8526, Japan
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Abstract
Regucalcin was discovered in 1978 as a calcium-binding protein that does not contain EF-hand motif of Ca(2+)-binding domain [M. Yamaguchi and T. Yamamoto, Chem. Pharm. Bull. 26 1915-1918 (1978)]. In recent years, regucalcin has been demonstrated to play an important role as a regulatory protein in Ca2+ signaling in rat liver and kidney cells. The organization of the rat regucalcin gene consists of seven exons and six introns. The mRNA is mainly present in liver and kidney with a size of 1.8 kb. Hepatic regucalcin mRNA expression has been shown to be stimulated by various factors including calcium, calcitonin, insulin, and estrogen in rats. The mRNA is also expressed in hepatoma cells (Morris hepatoma, HepG2, and rat hepatoma H4-II-E cells). Regucalcin plays a role in the maintenance of intracellular Ca2+ homeostasis due to activating Ca2+ pump enzymes in the plasma membrane (basolateral membrane) and microsomes of liver and renal cortex cells. Moreover, regucalcin has an inhibitory effect on the activation of Ca2+/calmodulin-dependent enzymes and protein kinase C. Also, regucalcin has been demonstrated to regulate nuclear function in liver cells; it can inhibit Ca(2+)-activated DNA fragmentation, DNA and RNA synthesis, protein kinase and protein phosphatase activities in the nuclei. Such an effect is also seen in the nuclei of regenerating rat liver. Regucalcin may play a physiological role in the control for overexpression of proliferative cells. Regucalcin has been proposed to be an important regulatory protein in Ca2+ signaling system, and it plays a multifunctional role in liver and kidney cells.
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Affiliation(s)
- M Yamaguchi
- Laboratory of Endocrinology and Molecular Metabolism, Graduate School of Nutritional Sciences, University of Shizuoka, Shizuoka City, Japan.
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Yamaguchi M, Hanahisa Y, Murata T. Expression of calcium-binding protein regucalcin and microsomal Ca2+-ATPase regulation in rat brain: attenuation with increasing age. Mol Cell Biochem 1999; 200:43-9. [PMID: 10569182 DOI: 10.1023/a:1006928402184] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
The expression of calcium-binding protein regucalcin and its effect on the microsomal Ca2+-ATPase activity in rat brain tissues was investigated. The expression of regucalcin mRNA was demonstrated by reverse transcription-polymerase chain reaction (RT-PCR) analysis in brain tissues using rat regucalcin-specific primers. Regucalcin concentration in the brain tissues was about 5 x 10(-9)) M as measured using enzyme-linked immunoadsorbent assay (ELISA), and this level was lowered with increasing age (50 weeks old). The presence of regucalcin (10(-9) to 10(-7) M) in the enzyme reaction mixture caused a significant decrease in Ca2+-ATPase activity in the brain microsomes of young rats (5 weeks old). Meanwhile, the enzyme activity was not significantly altered by the addition of calmodulin (1 or 50 microg/ml), calbindin (1 or 10 microg/ml), and S-100 A protein (5 or 25 microg/ml), which are other Ca2+-binding proteins in rat brain. The effect of regucalcin to inhibit microsomal Ca2+-ATPase activity was weakened in the brain of rats with increasing age (50 weeks old). The present study demonstrates that regucalcin is expressed in the brain, and that it can uniquely inhibit Ca2+-ATPase activity in the brain microsomes of rats. The findings suggest that regucalcin plays a role in the regulation of microsomal Ca2+-ATPase activity in rat brain tissues.
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Affiliation(s)
- M Yamaguchi
- Laboratory of Endocrinology and Molecular Metabolism, Graduate School of Nutritional Sciences, University of Shizuoka, Shizuoka City, Japan
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13
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Abstract
Regucalcin is a novel calcium-binding protein which does not contain EF-hand motif as a Ca2+ -binding domain. The organization of the rat regucalcin gene consists of seven exons and six introns. Its mRNA is mainly present in liver but slightly in kidney with a size of 1.8 kb. Hepatic regucalcin mRNA expression is stimulated by various factors including calcium, calcitonin, insulin, and oestrogen in rats. The mRNA is also expressed in hepatoma cells (Morris hepatoma and HepG2). Regucalcin plays a role in the maintenance of cytosolic Ca2+ homeostasis in liver cells. Moreover, regucalcin has an inhibitory effect on Ca2+ /calmodulin-dependent enzyme activation, protein kinase C activation, and many Ca2+ -activated enzymes, indicating a role in the regulation of the Ca2+ -signalling system. Recently, regucalcin has been demonstrated to regulate nuclear function in liver cells. Regucalcin can inhibit Ca2+ -activated nuclear DNA fragmentation in rat isolated liver nuclei. Furthermore, the liver nuclear DNA and RNA syntheses are inhibited by regucalcin. Such an effect of regucalcin is also seen in the nuclei of regenerating rat liver. The regucalcin mRNA level is increased in regenerating liver. These findings suggest that regucalcin plays a regulatory role in the suppression for overexpression of proliferative cells.
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Affiliation(s)
- Masayoshi Yamaguchi
- Laboratory of Endocrinology and Molecular Metabolism, Graduate School of Nutritional Sciences, University of Shizuoka, Shizuoka City, Japan
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