Yu-Mi Yang

Yonsei University, Seoul, Seoul, South Korea

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Publications (10)26.92 Total impact

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    ABSTRACT: Homer proteins are scaffold molecules with a domain structure consisting of an N-terminal Ena/VASP homology 1 (EVH) protein-binding domain and C-terminal leucine zipper/coiled-coil domain. The EVH domain recognizes proline-rich motifs and binds multiple Ca(2+) signaling proteins, including G protein-coupled receptors, inositol 1,4,5-triphosphate receptors (IP3Rs), ryanodine receptors (RyRs), and transient receptor potential channels. However, their role in Ca(2+) signaling in non-excitable cells is not well understood. In the present work, we investigated the role of Homer2 on Ca(2+) signaling in parotid gland acinar cells using Homer2 deficient (Homer2(-/-)) mice. Homer2 is localized at the apical pole in acinar cells. Deletion of Homer2 did not affect IP3R localization or channel activity and did not affect the expression and activity of sarco/endoplasmic reticulum Ca(2+) ATPase (SERCA) pumps. In contrast, Homer2 deletion markedly increased expression of plasma membrane Ca(2+) ATPase (PMCA) pumps, in particular PMCA4, at the apical pole. Accordingly, Homer2 deficiency increased Ca(2+) extrusion by acinar cells. These findings were supported by co-immunoprecipitation of Homer2 and PMCA in wild-type parotid cells and transfected human embryonic kidney 293 (HEK293) cells. We identified a Homer binding PPXXF-like motif in the N-terminus of PMCA that is required for interaction with Homer2. Mutation of the PPXXF-like motif did not affect the interaction of PMCA with Homer1, but inhibited its interaction with Homer2 and increased Ca(2+) clearance by PMCA. These findings reveal an important regulation of PMCA by Homer2 that has a central role on PMCA-mediated Ca(2+) signaling in parotid acinar cells.
    The Journal of biological chemistry. 07/2014;
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    ABSTRACT: DA-6034, a eupatilin derivative of flavonoid, has shown potent effects on the protection of gastric mucosa and induced the increases in fluid and glycoprotein secretion in human and rat corneal and conjunctival cells, suggesting that it might be considered as a drug for the treatment of dry eye. However, whether DA-6034 induces Ca(2+) signaling and its underlying mechanism in epithelial cells are not known. In the present study, we investigated the mechanism for actions of DA-6034 in Ca(2+) signaling pathways of the epithelial cells (conjunctival and corneal cells) from human donor eyes and mouse salivary gland epithelial cells. DA-6034 activated Ca(2+)-activated Cl(-) channels (CaCCs) and increased intracellular calcium concentrations ([Ca(2+)]i) in primary cultured human conjunctival cells. DA-6034 also increased [Ca(2+)]i in mouse salivary gland cells and human corneal epithelial cells. [Ca(2+)]i increase of DA-6034 was dependent on the Ca(2+) entry from extracellular and Ca(2+) release from internal Ca(2+) stores. Interestingly, these effects of DA-6034 were related to ryanodine receptors (RyRs) but not phospholipase C/inositol 1,4,5-triphosphate (IP3) pathway and lysosomal Ca(2+) stores. These results suggest that DA-6034 induces Ca(2+) signaling via extracellular Ca(2+) entry and RyRs-sensitive Ca(2+) release from internal Ca(2+) stores in epithelial cells.
    Korean Journal of Physiology and Pharmacology 04/2014; 18(2):89-94. · 1.00 Impact Factor
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    ABSTRACT: Receptor activator of NF-κB ligand (RANKL)-induced osteoclastogenesis is accompanied by intracellular Ca(2+) mobilization in a form of oscillations, which plays essential roles by activating sequentially Ca(2+)/calmodulin-dependent protein kinase, calcineurin and NFATc1, necessary in the osteoclast differentiation. However, it is not known whether Ca(2+) mobilization which is evoked in RANKL-independent way induces to differentiate into osteoclasts. In present study, we investigated Ca(2+) mobilization induced by aluminum fluoride (AlF4 (-)), a G-protein activator, with or without RANKL and the effects of AlF4 (-) on the osteoclastogenesis in primary cultured mouse bone marrow-derived macrophages (BMMs). We show here that AlF4 (-) induces intracellular Ca(2+) concentration ([Ca(2+)]i) oscillations, which is dependent on extracellular Ca(2+) influx. Notably, co-stimulation of AlF4 (-) with RANKL resulted in enhanced NFATc1 expression and formation of tartrate-resistant acid phosphatase (TRAP) positive multinucleated cells. Additionally, we confirmed that mitogen-activated protein kinase (MAPK) is also activated by AlF4 (-). Taken together, these results demonstrate that G-protein would be a novel modulator responsible for [Ca(2+)]i oscillations and MAPK activation which lead to enhancement of RANKL-mediated osteoclastogenesis.
    Korean Journal of Physiology and Pharmacology 10/2013; 17(5):427-33. · 1.00 Impact Factor
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    ABSTRACT: The transient receptor potential melastatin type 7 (TRPM7) channel is a widely expressed non-selective cation channel with fusion to the C-terminal alpha kinase domain and regarded as a key regulator of whole body Mg(2+) homeostasis in mammals. However, the roles of TRPM7 during osteoclastogenesis in RAW264.7 cells and bone marrow-derived monocyte/macrophage precursor cells (BMMs) are not clear. In the present study, we investigate the roles of TRPM7 in osteoclastogenesis using methods of small interfering RNA (siRNA), RT-PCR, patch-clamp, and calcium imaging. RANKL (receptor activator of NF-κB ligand) stimulation did not affect the TRPM7 expression and TRPM7-mediated current was activated in HEK293, RAW264.7, and BMM cells by the regulation of Mg(2+). Knock-down of TRPM7 by siTRPM7 reduced intracellular Ca(2+) concentration ([Ca(2+)](i)) increases by 0 mM [Mg(2+)](e) in HEK293 cells and inhibited the generation of RANKL-induced Ca(2+) oscillations in RAW264.7 cells. Finally, knock-down of TRPM7 suppressed RANKL-mediated osteoclastogenesis such as activation and translocation of NFATc1, formation of multinucleated cells, and the bone resorptive activity, sequentially. These results suggest that TRPM7 plays an essential role in the RANKL-induced [Ca(2+)](i) oscillations that triggers the late stages of osteoclastogenesis.
    Korean Journal of Physiology and Pharmacology 02/2013; 17(1):65-71. · 1.00 Impact Factor
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    ABSTRACT: Protease-activated receptor 2 (PAR2), a G protein-coupled receptor expressed in airway epithelia and smooth muscle, plays an important role in airway inflammation. In this study, we demonstrated that activation of PAR2 induces mucus secretion from the human airway gland and examined the underlying mechanism using the porcine and murine airway glands. The mucosa with underlying submucosal glands were dissected from the cartilage of tissues, pinned with the mucosal side up at the gas/bath solution interface of a physiological chamber, and covered with oil so that secretions from individual glands could be visualized as spherical bubbles in the oil. Secretion rates were determined by optical monitoring of the bubble diameter. The Ca(2+)-sensitive dye Fura2-AM was used to determine intracellular Ca(2+) concentration ([Ca(2+)](i)) by means of spectrofluorometry. Stimulation of human tracheal mucosa with PAR2-activating peptide (PAR2-AP) elevated intracellular Ca(2+) and induced glandular secretion equal to approximately 30% of the carbachol response in the human airway. Porcine gland tissue was more sensitive to PAR2-AP, and this response was dependent on Ca(2+) and anion secretion. When the mouse trachea were exposed to PAR2-AP, large amounts of secretion were observed in both wild type and ΔF508 cystic fibrosis transmembrane conductance regulator mutant mice but there is no secretion from PAR-2 knock out mice. In conclusion, PAR2-AP is an agonist for mucus secretion from the airway gland that is Ca(2+)-dependent and cystic fibrosis transmembrane conductance regulator-independent.
    PLoS ONE 01/2012; 7(8):e43188. · 3.73 Impact Factor
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    ABSTRACT: Human and pig airway submucosal glands secrete mucus in response to substance P (SubP), but in pig tracheal glands the response to SubP is >10-fold greater than in humans and shares features with cholinergically produced secretion. CFTR-deficient pigs provide a model for human cystic fibrosis (CF), and in newborn CF pigs the response of tracheal glands to SubP is significantly reduced (Joo et al. J Clin Invest 120: 3161-3166, 2010). To further define features of SubP-mediated gland secretion, we optically measured secretion rates from individual adult porcine glands in isolated tracheal tissues in response to mucosal capsaicin and serosal SubP. Mucosal capsaicin (EC(50) = 19 μM) stimulated low rates of secretion that were partially inhibited by tetrodotoxin and by inhibitors for muscarinic, VIP, and SubP receptors, suggesting reflex stimulation of secretion by multiple transmitters. Secretion in response to mucosal capsaicin was inhibited by CFTR(inh)-172, but not by niflumic acid. Serosal SubP (EC(50) = 230 nM) stimulated 10-fold more secretion than mucosal capsaicin, with a V(max) similar to that of carbachol. Secretion rates peaked within 5 min and then declined to a lower sustained rate. SubP-stimulated secretion was inhibited 75% by bumetanide, 53% by removal of HCO(3)(-), and 85% by bumetanide + removal of HCO(3)(-); it was not inhibited by atropine but was inhibited by niflumic acid, clotrimazole, BAPTA-AM, nominally Ca(2+)-free bath solution, and the adenylate cyclase inhibitor MDL-12330A. Ratiometric measurements of fura 2 fluorescence in dissociated gland cells showed that SubP and carbachol increased intracellular Ca(2+) concentration by similar amounts. SubP produced rapid volume loss by serous and mucous cells, expansion of gland lumina, mucus flow, and exocytosis but little or no contraction of myoepithelial cells. These and prior results suggest that SubP stimulates pig gland secretion via CFTR- and Ca(2+)-activated Cl(-) channels.
    AJP Lung Cellular and Molecular Physiology 12/2010; 300(3):L370-9. · 3.52 Impact Factor
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    ABSTRACT: RANKL (receptor activator of NF-kappaB ligand) induces osteoclastogenesis by activating multiple signaling pathways in osteoclast precursor cells, chief among which is induction of long lasting oscillations in the intracellular concentration of Ca(2+) ([Ca(2+)](i)). The [Ca(2+)](i) oscillations activate calcineurin, which activates the transcription factor NFATc1. The pathway by which RANKL induces [Ca(2+)](i) oscillations and osteoclastogenesis is poorly understood. Here we report the discovery of a novel pathway induced by RANKL to cause a long lasting increase in reactive oxygen species (ROS) and [Ca(2+)](i) oscillations that is essential for differentiation of bone marrow-derived monocytes into osteoclasts. The pathway includes RANKL-mediated stimulation of Rac1 to generate ROS, which stimulate phospholipase Cgamma1 to evoke [Ca(2+)](i) oscillations by stimulating Ca(2+) release from the inositol 1,4,5-trisphosphate pool and STIM1-regulated Ca(2+) influx. Induction and activation of the pathway is observed only after 24-h stimulation with RANKL and lasts for at least 3 days. The physiological role of the pathway is demonstrated in mice with deletion of the Peroxiredoxin II gene and results in a mark increase is ROS and, consequently, a decrease in bone density. Moreover, bone marrow-derived monocytes in PrxII(-/-) primary culture show increased ROS and spontaneous [Ca(2+)](i) oscillations. These findings identify the primary RANKL-stimulated pathway to trigger the late stages of osteoclastogenesis and regulate bone resorption.
    Journal of Biological Chemistry 03/2010; 285(10):6913-21. · 4.65 Impact Factor
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    ABSTRACT: Adequate fluid secretion from airway mucosa is essential for maintaining mucociliary clearance, and fluid hypersecretion is a prominent feature of inflammatory airway diseases such as allergic rhinitis. House dust mite extract (HDM) has been reported to activate protease-activated receptors (PARs), which play various roles in airway epithelia. However, the role of HDM in regulating ion transporters and fluid secretion has not been investigated. We examined the effect of HDM on ion transport in human primary nasal epithelial cells. The Ca(2+)-sensitive dye Fura2-AM was used to determine intracellular Ca(2+) concentration ([Ca(2+)](i)) by means of spectrofluorometry in human normal nasal epithelial cells (NHNE). Short-circuit current (Isc) was measured using Ussing chambers. Fluid secretion from porcine airway mucosa was observed by optical measurement. HDM extract (10 microg/Ml) effectively cleaved the PAR-2 peptide and induced an increase of [Ca(2+)](i) that was abolished by desensitization with trypsin, but not with thrombin. Apical application of HDM-induced Isc sensitive to both a cystic fibrosis transmembrane conductance regulator (CFTR) inhibitor and a Ca(2+)-activated Cl(-) channel (CaCC) inhibitor. HDM extract also stimulated fluid secretion from porcine airway mucosa. HDM extract activated PAR-2 and apical Cl(-) secretion via CaCC and CFTR, and HDM-induced fluid secretion in porcine airway mucosa. Our results suggest a role for PAR-2 in mucociliary clearance and fluid hypersecretion of airway mucosa in response to air-borne allergens such as HDM.
    Journal of Cellular Biochemistry 02/2010; 109(6):1254-63. · 3.06 Impact Factor
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    ABSTRACT: A mutation of Atp2a2 gene encoding the sarco/endoplasmic reticulum Ca(2+)-ATPase 2 (SERCA2) causes Darier's disease in human and null mutation in one copy of Atp2a2 leads to a high incidence of squamous cell tumor in a mouse model. In SERCA2 heterozygote (SERCA2(+/-)) mice keratinocytes, mechanisms involved in partial depletion of SERCA2 gene and its related tumor induction have not been studied. In this study, we investigated Ca(2+) signaling and differential gene expression in primary cultured keratinocytes from SERCA2(+/-) mice. SERCA2(+/-) keratinocytes showed reduced initial increases in intracellular concentration of calcium in response to ATP, a G-protein coupled receptor agonist, and higher store-operated Ca(2+) entry with the treatment of thapsigargin, an inhibitor of SERCA, compared to wild type kerationcytes. Protein expressions of plasma membrane Ca(2+) ATPases, NFATc1, phosphorylated ERK, JNK, and phospholipase gamma1 were increased in SERCA2(+/-) keratinocytes. Using the gene fishing system, we first found in SERCA2(+/-) keratinocytes that gene level of tumor-associated calcium signal transducer 1, crystalline alphaB, procollagen XVIII alpha1, and nuclear factor I-B were increased. Expression of involucrin, a marker of keratinocyte differentiation, was decreased in SERCA2(+/-) keratinocytes. These results suggest that the alterations of Ca(2+) signaling by SERCA2 haploinsufficiency alternate the gene expression of tumor induction and differentiation in keratinocytes.
    Progress in Biophysics and Molecular Biology 10/2009; 103(1):81-7. · 2.91 Impact Factor
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    ABSTRACT: RANKL is essential for the terminal differentiation of monocytes/macrophages into osteoclasts. RANKL induces long-lasting oscillations in the intracellular concentration of Ca(2+) ([Ca(2+)](i)) only after 24 h of stimulation. These Ca(2+) oscillations play a switch-on role in NFATc1 expression and osteoclast differentiation. Which Ca(2+) transporting pathway is induced by RANKL to evoke the Ca(2+) oscillations and its specific role in RANKL-mediated osteoclast differentiation is not known. This study examined the effect of a partial loss of sarco/endoplasmic reticulum Ca(2+) ATPase type 2 (SERCA2) on osteoclast differentiation in SERCA2 heterozygote mice (SERCA2(+/-)). The BMD in the tibias of SERCA2(+/-) mice increased >1.5-fold compared with wildtype mice (WT). RANKL-induced [Ca(2+)](i) oscillations were generated 48 h after RANKL treatment in the WT mice but not in the SERCA2(+/-) bone marrow-derived macrophages (BMMs). Forty-eight hours after RANKL treatment, there was a lower level of NFATc1 protein expression and markedly reduced translocation of NFATc1 into the nucleus during osteoclastogenesis of the SERCA2(+/-) BMMs. In addition, RANKL treatment of SERCA2(+/-) BMMs incompletely induced formation of multinucleated cells, leading to reduced bone resorption activity. These results suggest that RANKL-mediated induction of SERCA2 plays a critical role in the RANKL-induced [Ca(2+)](i) oscillations that are essential for osteoclastogenesis.
    Journal of bone and mineral research: the official journal of the American Society for Bone and Mineral Research 06/2009; 24(10):1763-9. · 6.04 Impact Factor