Signaling pathways regulating FSH- and amphiregulin-induced meiotic resumption and cumulus cell expansion in the pig

To define signaling pathways that drive FSH- and epidermal growth factor (EGF)-like peptide-induced cumulus expansion and oocyte meiotic resumption, in vitro cultured pig cumulus–oocyte complexes were treated with specific protein kinase inhibitors. We found that FSH-induced maturation of oocytes was blocked in germinal vesicle (GV) stage by protein kinase A (PKA), MAPK14, MAPK3/1, and EGF receptor (EGFR) tyrosine kinase inhibitors (H89, SB203580, U0126, and AG1478 respectively) whereas phosphoinositide-3-kinase/v-akt murine thymoma viral oncogene homolog (PI3K/AKT) inhibitor (LY294002) blocked maturation of oocytes in metaphase I (MI). Amphiregulin (AREG)-induced maturation of oocytes was efficiently blocked in GV by U0126, AG1478, and low concentrations of LY294002; H89, SB203580, and high concentrations of LY294002 allowed the oocytes to undergo breakdown of GV and blocked maturation in MI. Both FSH- and AREG-induced cumulus expansion was incompletely inhibited by H89 and completely inhibited by SB203580, U0126, AG1478, and LY294002. The inhibitors partially or completely inhibited expression of expansion-related genes (HAS2, PTGS2, and TNFAIP6) with two exceptions: H89 inhibited only TNFAIP6 expression and LY294002 increased expression of PTGS2. The results of this study are consistent with the idea that PKA and MAPK14 pathways are essential for FSH-induced transactivation of the EGFR, and synthesis of EGF-like peptides in cumulus cells and MAPK3/1 is involved in regulation of transcriptional and posttranscriptional events in cumulus cells required for meiotic resumption and cumulus expansion. PI3K/AKT signaling is important for regulation of cumulus expansion, AREG-induced meiotic resumption, and oocyte MI/MII transition. The present data also indicate the existence of an FSH-activated and PKA-independent pathway involved in regulation of HAS2 and PTGS2 expression in cumulus cells.

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Disrupted Function of Tumor Necrosis Factor-α-Stimulated Gene 6 Blocks Cumulus Cell-Oocyte Complex Expansion

Endocrinology ◽

10.1210/en.2003-0487 ◽

2003 ◽

Vol 144 (10) ◽

pp. 4376-4384 ◽

Cited By ~ 101

Author(s):

Scott A. Ochsner ◽

Anthony J. Day ◽

Marilyn S. Rugg ◽

Richard M. Breyer ◽

Richard H. Gomer ◽

...

Keyword(s):

Protein Kinase ◽

Kinase Inhibitors ◽

Cumulus Cell ◽

Cumulus Cells ◽

Mapk Signaling ◽

Protein Kinase Inhibitors ◽

Receptor Subtype ◽

Cumulus Expansion ◽

Specific Antibodies

During ovulation, the oocyte and surrounding somatic cumulus cells contained within a specialized, mucoid matrix are released from the ovary. One matrix component, TNF-α-stimulated gene 6 (TSG-6), is a hyaluronan binding protein induced in cumulus cells of preovulatory follicles by the LH surge and is decreased in cumulus cells of COX-2 and prostaglandin E2 (PGE2) receptor subtype EP2 null mice that exhibit impaired ovulation and cumulus expansion. To determine if TSG-6 was hormonally induced in cumulus cells in vitro and was functional during the formation of the expanded matrix, we established a cumulus cell-oocyte complex (COC) culture system. This system was used to analyze the effects of FSH, PGE2, EP2 receptor, and selected protein kinase inhibitors on TSG-6 production as well as specific antibodies to the TSG-6 link module on TSG-6 function. We document that TSG-6 message and protein are induced by cAMP/protein kinase A/MAPK signaling pathways and that blocking these cascades prevents expansion and the production of TSG-6. FSH but not PGE2 rescued expansion and production of TSG-6 in the EP2 null COCs, indicating that generation of a cAMP signal is essential. Furthermore, disruption of the functional interactions between TSG-6, inter-α trypsin inhibitor, and hyaluronan with specific antibodies severely altered matrix formation and cumulus expansion, as recorded by time-lapse imaging. Collectively, these results indicate that TSG-6 mRNA is induced in cumulus cells in culture by cAMP and that the secreted TSG-6 protein is a key structural component of the mouse COC matrix.

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Application of a PBPK Model of Rivaroxaban to Prospective Simulations of Drug-Drug-Disease Interactions with Protein Kinase Inhibitors in CA-VTE

10.22541/au.162502338.80368982/v1 ◽

2021 ◽

Author(s):

Eleanor Jing Yi Cheong ◽

Daniel Zhi Wei Ng ◽

Sheng Yuan Chin ◽

Ziteng Wang ◽

Eric Chun Yong Chan

Keyword(s):

Protein Kinase ◽

Kinase Inhibitors ◽

Pbpk Model ◽

Organic Anion ◽

Protein Kinase Inhibitors ◽

Organic Anion Transporter ◽

Pbpk Modelling ◽

Anion Transporter

Background and Purpose Rivaroxaban is emerging as a viable anticoagulant for the pharmacological management of cancer associated venous thromboembolism (CA-VTE). Being eliminated via CYP3A4/2J2-mediated metabolism and organic anion transporter 3 (OAT3)/P-glycoprotein-mediated renal secretion, rivaroxaban is susceptible to drug-drug interactions (DDIs) with protein kinase inhibitors (PKIs), erlotinib and nilotinib. Physiologically based pharmacokinetic (PBPK) modelling was applied to interrogate the DDIs for dose adjustment of rivaroxaban in CA-VTE. Experimental Approach The inhibitory potencies of erlotinib and nilotinib on CYP3A4/2J2-mediated metabolism of rivaroxaban were characterized. Using prototypical OAT3 inhibitor ketoconazole, in vitro OAT3 inhibition assays were optimized to ascertain the in vivo relevance of derived inhibitory constants (K). DDIs between rivaroxaban and erlotinib or nilotinib were investigated using iteratively verified PBPK model. Key Results Mechanism-based inactivation (MBI) of CYP3A4-mediated rivaroxaban metabolism by both PKIs and MBI of CYP2J2 by erlotinib were established. The importance of substrate specificity and nonspecific binding to derive OAT3-inhibitory K values of ketoconazole and nilotinib for the accurate prediction of DDIs was illustrated. When simulated rivaroxaban exposure variations with concomitant erlotinib and nilotinib therapy were evaluated using published dose-exposure equivalence metrics and bleeding risk analyses, dose reductions from 20 mg to 15 mg and 10 mg in normal and mild renal dysfunction, respectively, were warranted. Conclusion and Implications We established the PBPK-DDI platform to prospectively interrogate and manage clinically relevant interactions between rivaroxaban and PKIs in patients with underlying renal impairment. Rational dose adjustments were proposed, attesting to the capacity of PBPK modelling in facilitating precision medicine.

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New tools for carbohydrate sulfation analysis: heparan sulfate 2-O-sulfotransferase (HS2ST) is a target for small-molecule protein kinase inhibitors

Biochemical Journal ◽

10.1042/bcj20180265 ◽

2018 ◽

Vol 475 (15) ◽

pp. 2417-2433 ◽

Cited By ~ 8

Author(s):

Dominic P. Byrne ◽

Yong Li ◽

Krithika Ramakrishnan ◽

Igor L. Barsukov ◽

Edwin A. Yates ◽

...

Keyword(s):

Protein Kinase ◽

Heparan Sulfate ◽

Small Molecule ◽

Kinase Inhibitors ◽

Kinase Inhibitor ◽

Protein Kinase Inhibitors ◽

Fluorescent Substrate ◽

Raf Kinase ◽

Shift Analysis

Sulfation of carbohydrate residues occurs on a variety of glycans destined for secretion, and this modification is essential for efficient matrix-based signal transduction. Heparan sulfate (HS) glycosaminoglycans control physiological functions ranging from blood coagulation to cell proliferation. HS biosynthesis involves membrane-bound Golgi sulfotransferases, including HS 2-O-sulfotransferase (HS2ST), which transfers sulfate from the cofactor PAPS (3′-phosphoadenosine 5′-phosphosulfate) to the 2-O position of α-l-iduronate in the maturing polysaccharide chain. The current lack of simple non-radioactive enzyme assays that can be used to quantify the levels of carbohydrate sulfation hampers kinetic analysis of this process and the discovery of HS2ST inhibitors. In the present paper, we describe a new procedure for thermal shift analysis of purified HS2ST. Using this approach, we quantify HS2ST-catalysed oligosaccharide sulfation using a novel synthetic fluorescent substrate and screen the Published Kinase Inhibitor Set, to evaluate compounds that inhibit catalysis. We report the susceptibility of HS2ST to a variety of cell-permeable compounds in vitro, including polyanionic polar molecules, the protein kinase inhibitor rottlerin and oxindole-based RAF kinase inhibitors. In a related study, published back-to-back with the present study, we demonstrated that tyrosyl protein sulfotranferases are also inhibited by a variety of protein kinase inhibitors. We propose that appropriately validated small-molecule compounds could become new tools for rapid inhibition of glycan (and protein) sulfation in cells, and that protein kinase inhibitors might be repurposed or redesigned for the specific inhibition of HS2ST.

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Identification of Two Kinase Inhibitors with Synergistic Toxicity with Low-Dose Hydrogen Peroxide in Colorectal Cancer Cells In vitro

Cancers ◽

10.3390/cancers12010122 ◽

2020 ◽

Vol 12 (1) ◽

pp. 122 ◽

Cited By ~ 3

Author(s):

Eric Freund ◽

Kim-Rouven Liedtke ◽

Lea Miebach ◽

Kristian Wende ◽

Amanda Heidecke ◽

...

Keyword(s):

Oxidative Stress ◽

Colorectal Cancer ◽

Hydrogen Peroxide ◽

Protein Kinase ◽

Tumor Cells ◽

Low Dose ◽

Kinase Inhibitors ◽

Protein Kinase Inhibitors ◽

Colorectal Cancer Cells

Colorectal carcinoma is among the most common types of cancers. With this disease, diffuse scattering in the abdominal area (peritoneal carcinosis) often occurs before diagnosis, making surgical removal of the entire malignant tissue impossible due to a large number of tumor nodules. Previous treatment options include radiation and its combination with intraperitoneal heat-induced chemotherapy (HIPEC). Both options have strong side effects and are often poor in therapeutic efficacy. Tumor cells often grow and proliferate dysregulated, with enzymes of the protein kinase family often playing a crucial role. The present study investigated whether a combination of protein kinase inhibitors and low-dose induction of oxidative stress (using hydrogen peroxide, H2O2) has an additive cytotoxic effect on murine, colorectal tumor cells (CT26). Protein kinase inhibitors from a library of 80 substances were used to investigate colorectal cancer cells for their activity, morphology, and immunogenicity (immunogenic cancer cell death, ICD) upon mono or combination. Toxic compounds identified in 2D cultures were confirmed in 3D cultures, and additive cytotoxicity was identified for the substances lavendustin A, GF109203X, and rapamycin. Toxicity was concomitant with cell cycle arrest, but except HMGB1, no increased expression of immunogenic markers was identified with the combination treatment. The results were validated for GF109203X and rapamycin but not lavendustin A in the 3D model of different colorectal (HT29, SW480) and pancreatic cancer cell lines (MiaPaca, Panc01). In conclusion, our in vitro data suggest that combining oxidative stress with chemotherapy would be conceivable to enhance antitumor efficacy in HIPEC.

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332 GRANULOCYTE-MACROPHAGE COLONY STIMULATING FACTOR (GM-CSF) ENHANCES CUMULUS CELLS EXPANSION OF IN VITRO-MATURED BOVINE CUMULUS - OOCYTE COMPLEXES IN A CHEMICALLY DEFINED MEDIUM

Reproduction Fertility and Development ◽

10.1071/rdv22n1ab332 ◽

2010 ◽

Vol 22 (1) ◽

pp. 322

Author(s):

D. D. Bücher ◽

M. A. Castro ◽

M. E. Silva ◽

M. A. Berland ◽

I. I. Concha ◽

...

Keyword(s):

Cell Viability ◽

In Vitro Maturation ◽

Cumulus Cell ◽

Cumulus Cells ◽

Cell Number ◽

Control Group ◽

Cumulus Expansion ◽

Gm Csf ◽

Nuclear Stage

Granulocyte-macrophage colony stimulating factor (GM-CSF) is a pleiotropic cytokine that stimulates proliferation, differentiation and function in different cells types. We have previously demonstrated (Bücher DD et al. 2008 Reprod. Dom. Anim. 43 (Suppl. 3), 146 abst.) that both subunits of GM-CSF receptor are expressed in granulosa cells from antral follicles in bovine ovaries. Also, we determined that the cytokine enhances glucose uptake through facilitative hexose transporters in granulosa cells in primary culture. The goals of the present study were to characterize the expression of GM-CSF receptor in cumulus cells and oocytes from bovine antral follicles and to determine its effects on in vitro-matured bovine COCs in a chemically defined medium. To determine the presence of a and |5 subunits of GM-CSF receptor, COCs were aspirated from follicles <8 mm in diameter, fixed, and submitted to immunocytochemistry. To study the effect of GM-CSF on in vitro maturation of oocytes, COCs (n =481) were cultured using serum-free medium (SOF) containing 0, 1, 10, and 100 ng mL-1 of human recombinant GM-CSF (R&D Systems, Inc., Minneapolis, MN, USA) for 22 h at 39°C, 5% CO2 in humidified air. Nuclear stage, cumulus expansion, cumulus cell number, and viability were analyzed after in vitro maturation. Cumulus expansion was assessed using the cumulus expansion index (CEI) (Fagbohun C and Down S 1990 Biol. Reprod. 42, 413-423). Nuclear stage was evaluated using aceto-orcein stain. To determine cumulus cell viability and number, COCs (n = 10-12 per group) were transferred into an Eppendorf tube and cumulus cells were removed by vortexing for 3 min, stained with trypan blue and counted with a hemocytometer. The study was conducted in 6 replicates. Data from cumulus expansion and cell number were analyzed by Kruskal-Wallis analysis. Data for nuclear stage and cell viability were analyzed by chi-square analysis and one way ANOVA, respectively. Both receptor subunits were present in cumulus cells and oocytes from COCs. COCs cultured in 10 and 100 ng mL-1 GM-CSF had CEI scores (0.8 and 1.22, respectively) greater (P < 0.01) than controls (0.2), but the proportion of COCs displaying second metaphase did not differ (P = 0.5) among treatment groups. GM-CSF at a concentration of 100 ng mL-1 increased (P < 0.01) cumulus cell viability by more than 20% compared to the control group. Similarly, GM-CSF at concentrations of 10 and 100 ng mL-1 increased (P < 0.05) cumulus cell number by more than 20% and 45%, respectively, from the control group. The use of a specific inhibitor of PI3 kinase (Ly294002; 10 and 100 μM) blocked the stimulatory effect of GM-CSF on cumulus expansion, cell viability, and cell number. In conclusion, the results of the study suggest a plausible modulator role of GM-CSF in the metabolism and function of cumulus cells and oocytes during in vitro maturation. Funding from Faculty of Veterinary Sciences, Universidad Austral de Chile, MECESUP AUS-0005, AUS-0601, and DID D-2006-24 and from Universidad Católica de Temuco, research grant 2007 DGI-CDA-04.

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60 EFFECTS OF AY9944 A-7 ON MEIOTIC RESUMPTION OF PORCINE OOCYTES AND CUMULUS CELL EXPANSION

Reproduction Fertility and Development ◽

10.1071/rdv28n2ab60 ◽

2016 ◽

Vol 28 (2) ◽

pp. 160

Author(s):

S. Lee ◽

C. Khoirinaya ◽

J.-X. Jin ◽

G. A. Kim ◽

B.-C. Lee

Keyword(s):

Gene Expression ◽

Oocyte Maturation ◽

Cell Expansion ◽

Cholesterol Biosynthesis ◽

Cumulus Cell ◽

Cumulus Cells ◽

Mitogen Activated Protein Kinase ◽

Control Group ◽

Cumulus Expansion

In vitro studies on mammalian oocytes have shown that follicular fluid-meiosis activating sterol (FF-MAS) can overcome the inhibitory effect of hypoxanthine (Hx) on the resumption of meiosis. FF-MAS, an intermediate in the cholesterol biosynthesis pathway, is converted to testis meiosis–activating sterol by a sterol Δ14-reductase. AY9944 A-7, an inhibitor of Δ14-reductase and Δ7-reductase, induces accumulation of FF-MAS by inhibiting its metabolism. The aim of this study was to evaluate the effects of AY9944 A-7 on meiotic resumption of porcine oocytes, cumulus cell expansion, and gene expression related to M-phase-promoting factor (MPF), mitogen-activated protein kinase (MAPK), and oocyte maturation in oocytes and related to cumulus expansion in cumulus cells. In experiment 1, 1136 cumulus-oocyte complexes (COCs) were cultured in IVM media with 4 different concentrations (0, 10, 20, and 40 μM) of AY9944 A-7 in addition to a meiotic inhibitor (Hx, 4 mM) for 44 h. Oocytes treated with 10 and 20 μM AY9944 A-7 in the presence of Hx had significantly higher GVBD and M2 rates than the control group. However, 40 μM AY9944 A-7 significantly decreased GVBD and M2 rates and increased degeneration of oocytes compared with other groups. In experiment 2, 600 COCs were cultured in IVM media with 4 different concentrations (0, 10, 20, and 40 μM) of AY9944 A-7 in the absence of Hx for 44 h. Cumulus expansion of 40 μM AY9944 A-7 treated group was significantly decreased compared with other groups. In experiment 3, we evaluate the effects of AY9944 A-7 on gene expression, and the experiment was replicated four times. Data on gene expression were analysed using Student’s t-test. Oocytes treated with 10 μM AY9944 A-7 increased expression of genes involved in MPF (Cyclin B and Cdc2), MAPK (C-mos), and oocyte maturation (GDF9 and BMP15). Cumulus cells treated with 10 μM AY9944 A-7 decreased cumulus expansion-related genes (Has2, Tnfaip6, Ptgs2, and Ptx-3). In conclusion, our results suggest that although 10 μM AY9944 A-7 decreased cumulus expansion-related genes, there was no difference in cumulus expansion and it induced meiotic resumption of porcine oocytes with increased MPF, MAPK, and oocyte maturation-related genes. Further studies are needed to evaluate the effect of AY9944 A-7 on porcine embryo development. This study was supported by Ministry Of Trade, Industry & Energy (#10048948), Korea IPET (#114059–3), Research Institute for Veterinary Science, TS Corporation, and the BK21 plus program.

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Genistein reduces tumor necrosis factor alpha-induced plasminogen activator inhibitor-1 transcription but not urokinase expression in human endothelial cells

Blood ◽

10.1182/blood.v84.9.2984.2984 ◽

1994 ◽

Vol 84 (9) ◽

pp. 2984-2991 ◽

Cited By ~ 29

Author(s):

VW van Hinsbergh ◽

M Vermeer ◽

P Koolwijk ◽

J Grimbergen ◽

T Kooistra

Keyword(s):

Endothelial Cells ◽

Protein Kinase ◽

Plasminogen Activator ◽

Kinase Inhibitors ◽

Protein Kinase Inhibitors ◽

Tnf Alpha ◽

Necrosis Factor Alpha ◽

Tyrosine Protein Kinase ◽

Pai 1

Abstract The plasminogen activator inhibitor PAI-1 is markedly elevated in vivo and in vitro upon exposure to the inflammatory mediators tumor necrosis factor alpha (TNF alpha), interleukin-1 (IL-1), and bacterial lipopolysaccharide. Here we report that the isoflavone compound genistein prevents the increase in synthesis of PAI-1 induced by these inflammatory mediators in human endothelial cells in vitro, and partially reduces the basal PAI-1 production by these cells. These effects of genistein were accompanied by a decrease in PAI-1 mRNA and in a suppression of the PAI-1 transcription rate as shown by run-on assay. A specific action of genistein, probably by inhibiting a tyrosine protein kinase, is likely, because the structural genistein analogue daidzein, which has a low tyrosine protein kinase inhibitor activity, did not inhibit PAI-1 synthesis. Vanadate, a tyrosine protein phosphatase inhibitor, increased PAI-1 production. The effect of genistein on PAI-1 synthesis was rather selective. Herbimycin A also reduced PAI-1 synthesis, but several other tyrosine protein kinase inhibitors, namely tyrphostin A47, methyl-2,5-dihydroxy-cinnamate, and compound 5, were unable to do so. All these tyrosine protein kinase inhibitors reduced basic fibroblast growth factor (b-FGF)-induced [3H]thymidine incorporation in endothelial cells. This indicates that the effect of genistein on PAI-1 transcription proceeds independently of its effect on mitogenesis. In contrast to TNF-alpha-induced PAI-1 production, the transcription and synthesis of urokinase-type plasminogen activator (u-PA) was not inhibited by genistein. A TNF- alpha-mutant (Trp32Thr86TNF alpha) that specifically recognizes the 55- kD TNF-receptor, mimicked the effects of TNF alpha on both PAI-1 and u- PA. Because genistein affected PAI-1, but not u-PA induced by this mutant, involvement of different TNF-receptors cannot underlie the difference in the effects of genistein on PAI-1 and u-PA synthesis. Because genistein also inhibited PAI-1 induction by thrombin and IL-4, it is likely that genistein does not act on a TNF alpha-receptor- coupled protein kinase but on the signal transduction pathway enhancing PAI-1 transcription. Our results suggest that the TNF alpha-induced signal transduction pathway of PAI-1 transcription involves a genistein- sensitive step that is not involved in the induction of u-PA by TNF alpha. Given the limited sensitivity to several other tyrosine protein kinase inhibitors, this genistein-sensitive step may be a potential target for pharmacologic intervention to reduce elevated plasma PAI-1 levels.

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Mitogen-activated protein kinase-mediated phosphorylation of peroxiredoxin 6 regulates its phospholipase A2 activity

Biochemical Journal ◽

10.1042/bj20082061 ◽

2009 ◽

Vol 419 (3) ◽

pp. 669-679 ◽

Cited By ~ 65

Author(s):

Yongzheng Wu ◽

Sheldon I. Feinstein ◽

Yefim Manevich ◽

Ibrul Chowdhury ◽

Jhang Ho Pak ◽

...

Keyword(s):

Protein Kinase ◽

Phospholipase A2 ◽

Kinase Inhibitors ◽

Phosphorylation Site ◽

Protein Kinase Inhibitors ◽

Mitogen Activated Protein Kinase ◽

Alveolar Type ◽

Peroxiredoxin 6 ◽

Mitogen Activated Protein

Prdx6 (peroxiredoxin 6), a bifunctional protein with both GSH peroxidase and PLA2 (phospholipase A2) [aiPLA2 (acidic calcium-independent PLA2)] activities, is responsible for the metabolism of lung surfactant phospholipids. We propose that the aiPLA2 activity of the enzyme is regulated through phosphorylation. Incubation of isolated rat alveolar type II cells (AECII) with PMA, a PKC (protein kinase C) agonist, had no effect on Prdx6 expression but led to ∼75% increase in aiPLA2 activity that was abolished by pretreatment of cells with the MAPK (mitogen-activated protein kinase) inhibitors, SB202190 or PD98059. Prdx6 phosphorylation after incubation of AECII with PMA was demonstrated by autoradiography after immunoprecipitation with either anti-phosphothreonine o-phosphoserine antibodies. in vitro, several active isoforms of ERK (extracellular-signal-regulated kinase) and p38 phosphorylated Prdx6, resulting in an 11-fold increase in aiPLA2 activity. The increased activity was calcium-independent and was abolished by the aiPLA2 inhibitors, surfactant protein A and hexadecyl-3-trifluorethylglycero-sn-2-phospho-methanol (MJ33). The peroxidase activity of Prdx6 was unaffected by phosphorylation. Mass spectroscopic analysis of in vitro phosphorylated Prdx6 showed a unique phosphorylation site at Thr-177 and mutation of this residue abolished protein phosphorylation and the increase in MAPK-mediated activity. These results show that the MAPKs can mediate phosphorylation of Prdx6 at Thr-177 with a consequent marked increase in its aiPLA2 activity.

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Epidermal growth factor receptor downregulation in cultured bovine cumulus cells: reconstitution of calcium signaling and stimulated membrane permeabilization

Reproduction ◽

10.1530/rep.1.00420 ◽

2005 ◽

Vol 130 (4) ◽

pp. 517-528 ◽

Cited By ~ 5

Author(s):

Zhong Zhao ◽

Damien Garbett ◽

Julia L Hill ◽

David J Gross

Keyword(s):

Growth Factor ◽

Epidermal Growth Factor ◽

Egf Receptor ◽

Cumulus Cell ◽

Growth Factor Receptor ◽

Cumulus Cells ◽

Membrane Permeabilization ◽

Egf Receptors ◽

Epidermal Growth

Cumulus cell–oocyte complexes (COCs), culturedin vitro, are competent for maturation and fertilization. Inclusion of epidermal growth factor (EGF) in the COC culture medium enhancesin vitromaturation and subsequent embryonic development. It has been shown that isolated COCs exposed to EGF respond with a prolonged and pulsatile release of Ca2+into the extra-cellular medium and that cumulus cells (CCs) of complexes exhibit both a slow rise in intracellular [Ca2+] ([Ca2+]i) and plasma membrane permeabilization in response to EGF. These unusual signaling responses were examined in isolated, cultured bovine CCs. Few individual CCs showed [Ca2+]iincreases; the lack of response was found to be due to decrease of expression of endogenous EGF receptors after dissociation. CCs transfected with a human EGF receptor–GFP fusion protein showed robust, prolonged, EGF-stimulated [Ca2+]ielevations characteristic of CC responses in intact COCs. Many CCs that responded to EGF stimulation with a [Ca2+]irise also released entrapped fura-2 dye at the peak of the [Ca2+]iresponse, suggesting that CC permeabilization and death follows activation of the EGF receptor. The [Ca2+]ielevation due to EGF stimulation and subsequent membrane permeabilization was shown to be mediated by the inositol triphosphate signaling pathway.

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