• Journal of Embryo Transfer
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• v.24 no.4
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• pp.237-247
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• 2009

Melatonin (N-acetyl-5-methoxytryptamine) is the major neurohormone secreted during the night by the vertebrate pineal gland. The circadian pattern of pineal melatonin secretion is related to the biological clock within the suprachiasmatic nucleus (SCN) of the hypothalamus in mammals. The SCN coordinates the body's rhythms to the environmental light-dark cycle in response to light perceived by the retina, which acts mainly on retinal ganglion cells that contain the photopigment melanopsin. Calbindin-D9k (CaBP-9k) is a member of the S100 family of intracellular calcium- binding proteins, and in this review, we discuss the involvement of melatonin and CaBP-9k with respect to calcium homeostasis and apoptotic cell death. In future studies, we hope to provide important information on the roles played by CaBP-9k in cell signal transduction, cell proliferation, and $Ca^{2+}$ homeostasis in vivo and in vitro.

• Animal cells and systems
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• v.16 no.4
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• pp.269-273
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• 2012

Controlling metabolism throughout life is a necessity for living creatures, and perturbation of energy balance elicits disorders such as type-2 diabetes mellitus and cardiovascular disease. $Ca^{2+}$ plays a key role in regulating energy generation. $Ca^{2+}$ homeostasis of the endoplasmic reticulum (ER) lumen is maintained through the action of $Ca^{2+}$ channels and the $Ca^{2+}$ ATPase pump. Once released from the ER, $Ca^{2+}$ is taken up by mitochondria where it facilitates energy metabolism. Mitochondrial $Ca^{2+}$ serves as a key metabolic regulator and determinant of cell fate, necrosis, and/or apoptosis. Here, we focus on $Ca^{2+}$ transport from the ER to mitochondria, and $Ca^{2+}$-dependent regulation of mitochondrial energy metabolism.

• BMB Reports
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• v.43 no.3
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• pp.151-157
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• 2010

$Ca^{2+}$ is a universal signalling molecule that affects a variety of cellular processes including cardiac development. The majority of intracellular $Ca^{2+}$ is stored in the endoplasmic and sarcoplasmic reticulum of muscle and non-muscle cells. Calreticulin is a well studied $Ca^{2+}$-buffering protein in the endoplasmic reticulum, and calreticulin deficiency is embryonic lethal due to impaired cardiac development. Despite calsequestrin being the most abundant $Ca^{2+}$-buffering protein in the sarcoplasmic reticulum, viability is maintained in embryos without calsequestrin and normal $Ca^{2+}$ release and contractile function is observed. The $Ca^{2+}$ homeostasis regulated by the endoplasmic and sarcoplasmic reticulum is critical for the development and proper function of the heart.

• Asian Pacific Journal of Cancer Prevention
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• v.13 no.8
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• pp.3561-3568
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• 2012

The calcium sensing receptor (CaSR) is a member of the largest family of cell surface receptors, the G protein-coupled receptors involved in calcium homeostasis. The role of the CaSR in neoplasia appears to be homeostatic; loss of normal CaSR-induced response to extracellular calcium is observed in cancers of the colon and ovary, while increased release of PTHrP is observed in cancers of the breast, prostate and Leydig cells. Currently CaSR can be considered as a molecule that can either promote or prevent tumor growth depending on the type of cancer. Therefore, recognition of the multifaceted role of CaSR in gliomas and other malignant tumors in general is fundamental to elucidating the mechanisms of tumor progression and the development of novel therapeutic agents. Emphasis should be placed on development of drug-targeting methods to modulate CaSR activity in cancer cells.

• Journal of Nutrition and Health
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• v.30 no.4
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• pp.394-405
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• 1997

Endogenous zinc is important for maintaining zinc homeostasis because the size of endogenous zinc pool is almost 3-4 times bigger than that of dietary zinc. The purpose of this study was to examine the phytate effect on the reabsorption of endogenous zinc and the additional Ca effect on the phytate effect. Rats were fed a casein-based diet with added sodium phytate containing either high(1.6%) or low(0.8%) Ca concentrations for 4 weeks to reduce the body zinc pool. After the depletion period, $^{65}$ Zn was given by intraperitoneal injection to label the endogenous zinc pool. Rats were then assigned into phytate or non-phytate group within the same Ca group. feces were collected for 2 weeks of the initial collection period and 1 week after dietary crossover. The ratios of excreted fecal $^{65}$ Zn radioactivity of phytate group non-phytate group were determined as a measure of the phytate effect on the endogenous zinc. Mean fecal $^{65}$ Zn radioactivity was higher in the phytate group than in the non-phytate group during the entire 3 weeks of the collection period in the low Ca group, and during the initial collection period in the high Ca group(p <0.0001). This study showed an adverse phytate effect on endogenous zinc at both high and low dietary Ca levels. Elevated dietary Ca levels showed a synergistic effect on the phytate effect on endogenous zinc(p <0.05). These results imply greater phytate effect on zinc homeostasis rather than on zinc bioavailability through complexing with the endogenous zinc which is larger portion than the dietary zinc on zinc homeostasis.

• Journal of Life Science
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• v.5 no.1
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• pp.33-44
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• 1995

• Toxicological Research
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• v.20 no.3
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• pp.241-250
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• 2004

We previously found that bisphenol A (BPA) caused neurotoxic behavioral alteration. Since disturbance of calcium homeostasis is an implicated contributor in the neurotoxic mechanism of environmental toxicants, we investigated whether BPA alters calcium homeostasis. Unlike other neurotoxic agents which cause increase of intracellular calcium level, BPA decreased $[Ca^{2+}]_i$ dose-dependently in PC12 cells and cortical neuronal cells regardless of the calcium existence in buffer. BPA at greater concentrations than 100 $\mu\textrm{M}$ reduced cell viability significantly in both types of cells. BPA also suppressed L-glutamate (L-type channel activator, 30 mM) and trifluoperazine (calmodulin antagonist, 30 $\mu\textrm{M}$)-induced increase of $[Ca^{2+}]_i$. BPA further lowered caffeine (RYR activator, 100 $\mu\textrm{M}$)-decreased $[Ca^{2+}]_i$, but did not alter dantrolene (RYR inhibitor, 100 $\mu\textrm{M}$), heparin (IP3 inhibitor, 200 units/ml) and xestospongin C (IP3 inhibitor, 5 $\mu\textrm{M}$)-decreased $[Ca^{2+}]_i$. Cell viability was not directly related to intracellular calcium change by bisphenol A that alternation of intracellular calcium may not be a direct causal factor of BPA-induced neuronal cell death.

• Molecules and Cells
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• v.41 no.12
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• pp.1000-1007
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• 2018

Mitochondria and endoplasmic reticulum (ER) are essential organelles in eukaryotic cells, which play key roles in various biological pathways. Mitochondria are responsible for ATP production, maintenance of $Ca^{2+}$ homeostasis and regulation of apoptosis, while ER is involved in protein folding, lipid metabolism as well as $Ca^{2+}$ homeostasis. These organelles have their own functions, but they also communicate via mitochondrial-associated ER membrane (MAM) to provide another level of regulations in energy production, lipid process, $Ca^{2+}$ buffering, and apoptosis. Hence, defects in MAM alter cell survival and death. Here, we review components forming the molecular junctions of MAM and how MAM regulates cellular functions. Furthermore, we discuss the effects of impaired ER-mitochondrial communication in various neurodegenerative diseases.

• Biomolecules & Therapeutics
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• v.17 no.2
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• pp.125-132
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• 2009

Calbindin-$D_{9k}$ (CaBP-9k), a cytosolic calcium-binding protein, is expressed in a variety of tissues, i.e., the duodenum, uterus, placenta, kidney and pituitary gland. Duodenal CaBP-9k is involved in intestinal calcium absorption, and is regulated at transcriptional and post-transcriptional levels by 1,25-dihydroxyvitamin D3, the hormonal form of vitamin D, and glucocorticoids (GCs). Uterine CaBP-9k has been implicated in the regulation of myometrial action(s) through modulation of intracellular calcium, and steroid hormones appear to be the main regulators in its uterine and placental regulation. Because phenotypes of CaBP-9k-null mice appear to be normal, other calcium-transporter genes may compensate for its gene deletion and physiological function in knockout mice. Previous studies indicate that CaBP-9k may be controlled in a tissue-specific fashion. In this review, we summarize the current information on calcium homeostasis related to CaBP-9k gene regulation by GCs, vitamin D and its receptors, and its molecular regulatory mechanism. In addition, we present related data from our current research.

• Biomolecules & Therapeutics
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• v.20 no.2
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• pp.171-176
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• 2012

HaCaT cells are the immortalized human keratinocytes and have been extensively used to study the epidermal homeostasis and its pathophysiology. T helper cells play a role in various chronic dermatological conditions and they can affect skin barrier homeostasis. To evaluate whether HaCaT cells can be used as a model cell system to study abnormal skin barrier development in various dermatologic diseases, we analyzed the gene expression profile of epidermal differentiation markers of HaCaT cells in response to major T helper (Th) cell cytokines, such as $IFN{\gamma}$, IL-4, IL-17A and IL-22. The gene transcriptional profile of cornified envelope-associated proteins, such as filaggrin, loricrin, involucrin and keratin 10 (KRT10), in HaCaT cells was generally different from that in normal human keratinocytes (NHKs). This suggests that HaCaT cells have a limitation as a model system to study the pathophysiological mechanism associated with the Th cell cytokine-dependent changes in cornified envelope-associated proteins which are essential for normal skin barrier development. In contrast, the gene transcription profile change of human ${\beta}2$-defensin (HBD2) in response to $IFN{\gamma}$, IL-4 or IL-17A in HaCaT cells was consistent with the expression pattern of NHKs. $IFN{\gamma}$ also up-regulated transglutaminase 2 (TGM2) gene transcription in both HaCaT cells and NHKs. As an alternative cell culture system for NHKs, HaCaT cells can be used to study molecular mechanisms associated with abnormal HBD2 and TGM2 expression in response to $IFN{\gamma}$, IL-4 or IL-17A.