• Biomedical Science Letters
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• v.12 no.2
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• pp.81-89
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• 2006

The ischemia-responsive 94 gene (irp94) encoding a 94 kDa endoplasmic reticulum resident protein was investigated its molecular properties associated with unfoled protein responses. First, the expression of irp94 mRNA was tested after the reperfusion of the transient forebrain ischemia induction at the central nervous system in three Mongolian gerbils. Second, irp94 expression in PC12 cells, which are derived from transplantable rat pheochromocytoma cultured in the DMEM media, was tested at transcriptional and translational levels. The half life of irp94 mRNA was also determined In PC12 cells. Last, the changes of irp94 mRNA expression were investigated by the addition of various ER stress inducible chemicals (A23187, BFA, tunicamycin, DTT and $H_2O_2$) and proteasome inhibitors, and heat shock. High level expression of irp94 mRNA was detected after 3 hours reperfusion in the both sites of the cerebral cortex and hippocampus of the gerbil brain. The main regulation of irp94 mRNA expression in PC 12 cells was determined at the transcriptional level. The half life of irp94 mRNA in PC12 cells was approximately 5 hours after the initial translation. The remarkable expression of irp94 mRNA was detected by the treatment of tunicamycin, which blocks glycosylation of newly synthesized polypeptides, and $H_2O_2$, which induces apoptosis. When PC12 cells were treated with the cytosol proteasome inhibitors such as ALLN (N-acetyl-leucyl-norleucinal) and MG 132 (methylguanidine), irp94 mRNA expression was increased. These results indicate that expression of irp94 was induced by ER stress including oxidation condition and glycosylation blocking in proteins. Expression of irp94 was increased when the cells were chased after heat shock, suggesting that irp94 may be involved in recovery rather than protection against ER stresses. In addition, irp94 expression was remarkably increased when cytosol proteasomes were inhibited by ALLN and MG 132, suggesting that irp94 plays an important role for maintaining the ERAD (endoplasmic reticulum associated degradation) function.

• Journal of Life Science
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• v.20 no.8
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• pp.1249-1253
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• 2010

Sericin is a type of high molecular weight water-soluble glycoprotein surrounding fibroin (silk protein) that has been used as a cell culture supplement and accelerates cell proliferation in various serum-free media. The purpose of this study was to investigate the enhancing effect of thyroglobulin (Tg) secretion by sericin in thyrocytes, FRTL-5 cells. While Tg-mRNA expression was not enhanced, a secreted form of Tg was obviously increased by sericin. In this status, expression of both endoplasmic reticulum (ER) molecular chaperones (Bip & calreticulin) and ER membrane proteins (IRE1, PERK & ATF6) was enhanced. The proximal step of IRE1, XBP1 mRNA splicing was slightly detected however, the proximal step of PERK, phosphorylation of $eIF2{\alpha}$, was changeless. In addition, sericin enhanced cell viability by the MTT assay. The above results showing the ability of sericin to promote protein production demonstrated its potential usefulness as a new biomaterial.

• Biomedical Science Letters
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• v.11 no.3
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• pp.311-318
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• 2005

Grp78, discovered as one of the putative target genes of Hoxc8, is a highly conserved stress protein and functions as a molecular chaperone in the endoplasmic reticulum (ER). In order to see the stage-specific expression pattern of Grp78 during development, mouse embryos from day 7.5 to 17.5 p.c. were isolated, and RT-PCR as well as in situ hybridization was performed. When RT-PCR was performed using Grp78 specific primers, periodic expression pattern was detected. And also a region-specific expression pattern was detected with a strong expression in the trunk part of day 11.5 p.c. embryo, like that of Hoxc8. When in situ hybridization was performed, Grp78 was revealed to be expressed in the endoderm, somite, neuroepithelium cells of neural tube in early embryos. In the case of late embryos, Grp78 expression was detected in the liver, segmental bronchus within cranial lobe of lung, ossification center within the cartilage primordium of rib and vertebra, submandibular gland, as well as metanephros. These expression patterns are very much similar to those of Hoxc8. Since Hoxc8 has been reported to regulate apoptosis during organogenesis, it might be possible that the apoptotic function could have been conveyed through the expression of Grp78, implying that the Grp78 is one of the Hoxc8 downstream target genes.

• Molecules and Cells
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• v.25 no.3
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• pp.390-396
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• 2008

Calreticulin (CRT) is one of the major $Ca^{2+}$ binding chaperone proteins of the endoplasmic reticulum (ER) and an unusual luminal ER protein. Postnatally elevated expression of CRT leads to impaired development of the cardiac conductive system and may be responsible for the pathology of complete heart block. In this study, the molecular mechanisms that affect $Ca^{2+}$-dependent signal cascades were investigated using CRT-overexpressing cardiomyocytes. In particular, we asked whether calreticulin plays a critical role in the activation of $Ca^{2+}$-dependent apoptosis. In the cells overexpressing CRT, the intracellular calcium concentration was significantly increased and the activity of PKC and level of SECAR2a mRNA were reduced. Phosphorylation of Akt and ERKs decreased compared to control. In addition the activity of the anti-apoptotic factor, Bcl-2, was decreased and the activities of pro-apoptotic factor, Bax, p53 and caspase 8 were increased, leading to a dramatic augmentation of caspase 3 activity. Our results suggest that enhanced CRT expression in mature cardiomyocytes disrupts intracellular calcium regulation, leading to calcium-dependent apoptosis.

• Journal of Life Science
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• v.31 no.6
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• pp.568-573
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• 2021

This study identified genomic factors associated with endoplasmic reticulum protein (ERp)29 gene expression in a genome-wide association study (GWAS) of genetic variants, including single-nucleotide polymorphisms (SNPs). In total, 373 European genes from the 1000 Genomes Project were analyzed. SNPs with an allelic frequency of less than or more than 5% were removed, resulting in 5,913,563 SNPs including in the analysis. The following expression quantitative trait loci (eQTL) from the long noncoding RNA LOC105372577 were strongly associated with ERp29 expression: rs6138266 (p<4.172e10), rs62193420 (p<1.173e10), and rs6138267 (p<2.041e10). These were strongly expressed in the testis and in the brain. The three eQTL were identified through a transcriptome-wide association study (TWAS) and showed a significant association with ERp29 and osteosarcoma amplified 9 (OS9) expression. Upstream sequences of rs6138266 were recognized by ChIP-seq data, while HaploReg was used to demonstrate how its regulatory DNA binds upstream of transcription factor 1 (USF1). There were no changes in the expression of OS9 or USF1 following ER stress.