Daesuk Chung - Academia.edu (original) (raw)

Papers by Daesuk Chung

Cell Biology and Toxicology, 2004

Previous studies showed that the pesticide lindane (g-hexachlorocyclohexane) inhibits gap junctio... more Previous studies showed that the pesticide lindane (g-hexachlorocyclohexane) inhibits gap junction intercellular communication in rat myometrial cells. The present study tested the hypothesis that lindane and the phorbol ester 12-O-tetradecanoylphorbol-13-acetate (TPA) inhibit gap junction communication in rat myometrial and liver WB r-F344 cells by the common mechanism of increasing phosphorylation of the gap junction protein connexin43. We evaluated changes of connexin43 phosphorylation using Western blot of standard SDS-PAGE gels and cell immunostaining, and we monitored gap junction communication using microinjection and transfer of Lucifer yellow dye. Exposure of rat myometrial cells to lindane or TPA nearly abolished dye transfer but did not alter the electrophoretic mobility of connexin43, and neither lindane nor TPA increased phosphorylation of connexin43 as assessed by immunoblot with anti-phospho-connexin43 (S368) antibody. However, TPA increased punctate immuno£uorescence staining of phospho-connexin43 (S368) in myometrial cells whereas lindane had no such e¡ect. In WB r-F344 cells, lindane and TPA inhibited dye transfer. Lindane increased immunostaining for phospho-connexin43 (S368) in WB r-F344 cells without altering the abundance, electrophoretic mobility or phosphorylation of connexin43 as detected in immunoblots. TPA intensi¢ed a slower migrating connexin43 band and increased phospho-connexin43 (S368) in immunoblots, and intensi¢ed phospho-connexin43 immunostaining at WB r-F344 cell interfaces and nuclear regions. These results show that phosphorylation of connexin43 at serine 368 occurred in cell and toxicant speci¢c manners and was independent of changes in electrophoretic mobility in standard SDS-PAGE gels. Moreover, lindane inhibited gap junction communication in myometrial cells by a mechanism that was not be explained by changes in phosphorylation of connexin43.

Biology of Reproduction, 2012

Molecular and Cellular Endocrinology, 2015

Toxicological Sciences, 2006

Endocrinology, 2010

An increase in intracellular Ca2+ ([Ca2+]i) as a result of release of Ca2+ from intracellular sto... more An increase in intracellular Ca2+ ([Ca2+]i) as a result of release of Ca2+ from intracellular stores or influx of extracellular Ca2+ contributes to the regulation of smooth muscle contractile activity. Human uterine smooth muscle cells exhibit receptor-, store-, and diacylglycerol (OAG)-mediated extracellular Ca2+-dependent increases in [Ca2+]i (SRCE) and express canonical transient receptor potential-like channels (TRPC) mRNAs (predominantly TRPC1, -4, and -6) that have been implicated in SRCE. To determine the role of TRPC6 in human myometrial SRCE, short hairpin RNA constructs were designed that effectively targeted a TRPC6 mRNA reporter for degradation. One sequence was used to produce an adenovirus construct (TC6sh1). TC6sh1 reduced TRPC6 mRNA but not TRPC1, -3, -4, -5, or -7 mRNAs in PHM1-41 myometrial cells. Compared with uninfected cells or cells infected with empty vector, the increase in [Ca2+]i in response to OAG was specifically inhibited by TC6sh1, whereas SRCE response...

Endocrinology, 2012

Embryo-uterine interaction during early pregnancy critically depends on the coordinated expressio... more Embryo-uterine interaction during early pregnancy critically depends on the coordinated expression of numerous genes at the site of implantation. The epigenetic mechanism through DNA methylation (DNM) plays a major role in the control of gene expression, although this regulatory event remains unknown in uterine implantation sites. Our analysis revealed the presence of DNA methyltransferase 1 (Dnmt1) in mouse endometrial cells on the receptive d 4 of pregnancy and early postattachment (d 5) phase, whereas Dnmt3a had lower abundant expression. Both Dnmt1 and Dnmt3a were coordinately expressed in decidual cells on d 6–8. 5-Methycytosine showed a similar expression pattern to that of Dnmt1. The preimplantation inhibition of DNM by 5-aza-2′-deoxycytodine was not antagonistic for embryonic attachment, although endometrial stromal cell proliferation at the site of implantation was down-regulated, indicating a disturbance with the postattachment decidualization event. Indeed, the peri- or p...

Endocrinology, 2011

Previously, the uterine epithelial-stromal coculture system had limited success mimicking in vivo... more Previously, the uterine epithelial-stromal coculture system had limited success mimicking in vivo ovarian hormone-dependent cell-specific proliferation. Here, we established a mouse primary uterine coculture system, in which cells collected in pseudopregnancy specifically on d 4 are conducive to supporting hormone-induced cell-specific proliferation. When two cell types are placed in coculture without direct contact via cell culture inserts (nonadjacent), as opposed to with contact (adjacent), epithelial cells exhibit significant proliferation by estradiol-17β (E2), whereas progesterone in combination with E2 caused inhibition of epithelial cell proliferation and a major shift in proliferation from epithelial to stromal cells. Epithelial cell integrity, with respect to E-cadherin expression, persisted in nonadjacent, but not adjacent, conditions. In subsequent studies of nonadjacent cocultures, localization of estrogen receptor (ER)α and progesterone receptor (PR), but not ERβ, appe...

Biology of Reproduction, 2005

The present study examined the hypothesis that inhibition of myometrial gap junctions through MAP... more The present study examined the hypothesis that inhibition of myometrial gap junctions through MAPK1-induced phosphorylation of GJA1 (connexin43) leads to inhibition of spontaneous phasic uterine contractions by 2,2-dichlorobiphenyl (2,2-DCB). Uterine strips from Gestation Day 10-pregnant rats exposed in muscle baths to 2,2-DCB exhibited increased oscillatory frequency and decreased amplitude and synchronization of contractions. To assess effects on gap junctions, Lucifer yellow was injected into myometrial cells and transfer to adjacent cells was scored. After a 1-h treatment, 100 M 2,2-DCB decreased Lucifer yellow intercellular transfer in a concentration-dependent manner. The MAP2K1 inhibitor PD98059 increased percentage of dye transfer to adjacent myometrial cells from 18% in cultures exposed for 1 h to 100 M 2,2-DCB alone to 48% in cultures cotreated with 50 M PD98059 and 100 M 2,2-DCB. In contrast, the conventional PRKC inhibitor Gö 6976 (10 M) had no significant effect on 2,2-DCB-induced inhibition of dye transfer. Western blotting showed about a 4.5-fold increase in phosphorylation of GJA1 at S255, a MAPK1 site, after exposure to 100 M 2,2-DCB compared to untreated and solvent controls. However, there was no difference in phosphorylation of GJA1 at S368, a PRKC site. Cells treated with 2,2-DCB increased phosphorylated MAPK1, implicating the increase of activation of MAPK1. Cotreatment with 100 M 2,2-DCB and 5 M PD98059 reversed 2,2-DCB-induced modification of uterine contractions and increase of pGJA1(S255) in uterine strips. Therefore, this study suggests that 2,2-DCB decreases amplitude and synchronization of uterine contractions mediated through MAPK1-mediated phosphorylation of GJA1 and subsequent inhibition of myometrial gap junctions.

Molecular Endocrinology, 2012

Sik-similar protein (Sik-SP), a small nucleolar ribonucleoprotein, has been shown to be primarily... more Sik-similar protein (Sik-SP), a small nucleolar ribonucleoprotein, has been shown to be primarily involved in ribosome biogenesis. However, its role in the hormone-directed nuclear receptor signaling is largely unknown. Here, we provide novel evidence that Sik-SP is required for appropriate regulation of estrogen receptor (ER)α-mediated estradiol-17β (E2)-dependent uterine physiologic responses in mice. Studies by Western blotting using the newly developed antibodies for Sik-SP showed that this protein is up-regulated in both the ovariectomized wild-type and ERα null uteri by E2. Immunohistochemical analyses in uterine sections showed that this protein is induced in the epithelial and stromal cells. Coimmunoprecipitation studies revealed that E2 directs molecular interaction between Sik-SP and ERα. Furthermore, gel-mobility shift and chromatin immunoprecipitation analyses provided evidence that Sik-SP is recruited with ERα to estrogen-responsive uterine gene promoters. Overexpressio...

Biology of Reproduction, 2011

To explore the relationship between signal-stimulated increases in intracellular calcium ([Ca 2+ ... more To explore the relationship between signal-stimulated increases in intracellular calcium ([Ca 2+ ] i) and depletion and refilling of the endoplasmic reticulum (ER) Ca 2+ stores ([Ca 2+ ] L) in human myometrial cells, we measured simultaneous changes in [Ca 2+ ] i and [Ca 2+ ] L using Fura-2 and Mag-fluo-4, respectively, in PHM1-41 immortalized and primary cells derived from pregnant myometrium and in primary cells derived from nonpregnant tissue. Signal-and extracellular Ca 2+-dependent increases in [Ca 2+ ] i (SRCE) and ER refilling stimulated by oxytocin and cyclopiazonic acid were not inhibited by voltageoperated channel blocker nifedipine or mibefradil, inhibition of Na + /Ca 2+ exchange with KB-R7943, or zero extracellular Na + in PHM1-41 cells. Gadolinium-inhibited oxytocin-and cyclopiazonic acid-induced SRCE and slowed ER store refilling. TRPC1 mRNA knockdown specifically inhibited oxytocin-stimulated SRCE but had no statistically significant effect on ER store refilling and no effect on either parameter following cyclopiazonic acid treatment. Dominant negative STIMDERM expression attenuated oxytocin-and thapsigargin-stimulated SRCE. Both STIM1 and ORAI1-ORAI3 mRNA knockdowns significantly attenuated oxytocin-and cyclopiazonic acid-stimulated SRCE. The data also suggest that reduction in STIM1 or ORAI1-ORAI3 mRNA can impede the rate of ER store refilling following removal of SERCA inhibition. These data provide evidence for both distinct and overlapping influences of TRPC1, STIM1, and ORAI1-ORAI3 on SRCE and ER store refilling in human myometrial cells that may contribute to the regulation of myometrial Ca 2+ dynamics. These findings have important implications for understanding the control of myometrial Ca 2+ dynamics in relation to myometrial contractile function.