scholarly journals Midkine Is an Autocrine Activator of Signal Transducer and Activator of Transcription 3 in 3T3-L1 Cells

Endocrinology ◽  
2007 ◽  
Vol 148 (4) ◽  
pp. 1598-1604 ◽  
Author(s):  
Erin R. Cernkovich ◽  
Jianbei Deng ◽  
Kunjie Hua ◽  
Joyce B. Harp
Keyword(s):  
Tyrosine Phosphorylation ◽  
Neutralizing Antibodies ◽  
Clonal Expansion ◽  
Dependent Manner ◽  
Signal Transducer ◽  
Heparin Binding ◽  
Paracrine Factor ◽  
Signaling Protein ◽  
Mitotic Clonal Expansion ◽  
Transcription 3

Mitotic clonal expansion is believed to be necessary for 3T3-L1 adipocyte formation. Signal transducer and activator of transcription 3 (STAT3), a mitogenic signaling protein, is activated through tyrosine phosphorylation during the proliferative phases of adipogenesis. We hypothesize that this signaling protein plays a key role in mitotic clonal expansion and differentiation. Here we determined that the adipocyte differentiation cocktail containing isobutylmethylxanthine, dexamethasone, and insulin (MDI) induced STAT3 tyrosine phosphorylation indirectly through the synthesis of an autocrine/paracrine factor. We further determined that the factor has heparin binding properties and identified the factor as midkine, a pleiotrophic growth factor previously associated with neuronal development and oncogenesis. Recombinant midkine induced STAT3 tyrosine phosphorylation in a time- and dose-dependent manner and stimulated the proliferation of postconfluent 3T3-L1 cells. Midkine neutralizing antibodies inhibited differentiation-induced STAT3 tyrosine phosphorylation as well as adipogenesis. These results show that MDI-induced synthesis and release of midkine explains the delayed activation of STAT3 during adipogenesis and that the midkine-STAT3 signaling pathway plays a necessary role in mitotic clonal expansion and differentiation.

scholarly journals ZFP217 regulates adipogenesis by controlling mitotic clonal expansion in a METTL3-m6A dependent manner

RNA Biology ◽  
2019 ◽  
Vol 16 (12) ◽  
pp. 1785-1793 ◽  
Author(s):  
Qing Liu ◽  
Yuanling Zhao ◽  
Ruifan Wu ◽  
Qin Jiang ◽  
Min Cai ◽  
...  
Keyword(s):  
Clonal Expansion ◽  
Dependent Manner ◽  
Mitotic Clonal Expansion

scholarly journals IL-6 Up-Regulates the Expression of Rat LH Receptors during Granulosa Cell Differentiation

Endocrinology ◽  
2014 ◽  
Vol 155 (4) ◽  
pp. 1436-1444 ◽  
Author(s):  
Fumiharu Imai ◽  
Hiroshi Kishi ◽  
Kohshiro Nakao ◽  
Toshio Nishimura ◽  
Takashi Minegishi
Keyword(s):  
Mrna Expression ◽  
Granulosa Cells ◽  
Ovarian Function ◽  
Luciferase Assay ◽  
Dependent Manner ◽  
Signal Transducer ◽  
Female Wistar Rats ◽  
Translational Start ◽  
Transcription 3 ◽  
Dose Dependent

IL-6 is produced in granulosa cells under normal physiological conditions, including during ovulation. However, the roles of IL-6 in ovarian function, including regulation of LH receptor (LHR) expression in granulosa cells, have not been explored in detail. The aim of this study was to identify the mechanism underlying the effect of IL-6 on LHR expression in the granulosa cells of female Wistar rats. Our results indicated that IL-6 clearly enhanced the FSH-induced LHR mRNA expression in a dose-dependent manner and did not stimulate cAMP accumulation by itself. The membrane protein level of LHR, assessed by a binding assay, was increased by FSH and was further enhanced by association with IL-6. Results of the luciferase assay, using promoter constructs of LHR 281 bp upstream of the translational start site, revealed that IL-6 increased the promoter activity induced by FSH, but this effect was not observed with treatment by IL-6 alone. This ability of IL-6 to enhance FSH-induced LHR mRNA expression was blocked by the Janus tyrosine kinase (JAK) pathway inhibitor, but not by the ERK1/2 inhibitor. Thus, we speculated that this IL-6 activity might be mediated by the JAK/signal transducer and activator of transcription pathway. In addition, IL-6 augmented FSH-induced IL-6 receptor α mRNA expression and FSH elevated IL-6 production in granulosa cells, which indicates that IL-6 may positively regulate paracrine and autocrine actions in granulosa cells. These results suggest that IL-6 up-regulates FSH-induced LHR production by increasing mRNA transcription, and JAK/signal transducer and activator of transcription 3 signaling is required for up-regulation by IL-6 in granulosa cells.

scholarly journals Midkine Is Involved in Kidney Development and in Its Regulation by Retinoids

2002 ◽  
Vol 13 (3) ◽  
pp. 668-676
Author(s):  
José Vilar ◽  
Claude Lalou ◽  
Jean-Paul Duong Van Huyen ◽  
Stéphanie Charrin ◽  
Sylvie Hardouin ◽  
...  
Keyword(s):  
Retinoic Acid ◽  
Neutralizing Antibodies ◽  
Kidney Development ◽  
Vitamin A Deficiency ◽  
Branching Morphogenesis ◽  
Defined Medium ◽  
Dependent Manner ◽  
Heparin Binding

ABSTRACT. In the kidney, in which development depends on epithelial-mesenchymal interactions, it has been shown that retinoids modulate nephrogenesis in a dose-dependent manner in vivo and in vitro. Midkine (MK) is a retinoic acid responsive gene for a heparin-binding growth factor. The aim of the present study was therefore to quantify the expression of MK mRNA during renal development in the rat, to analyze the regulation of MK expression by retinoids in vivo and in vitro, and, finally, to study the role of MK in rat metanephric organ cultures. The spatiotemporal expression of MK in fetal kidney was studied. In control rats, MK expression is ubiquitous at gestational day 14, i.e., at the onset of nephrogenesis. On day 16, MK is expressed in the condensed mesenchyme and in early epithelialized mesenchymal derivatives. On gestational day 21, MK is rather localized in the nonmature glomeruli of the renal cortex. In utero exposure to vitamin A deficiency did not modify the specific spatial and temporal expression pattern of MK gene in the metanephros, although a decrease in mRNA expression occurred. In metanephroi explanted from 14-d-old fetuses and cultured in a defined medium, expression of MK mRNA was found to be stimulated when retinoic acid (100 nM) was added in the culture medium. Finally, in vitro nephrogenesis was strongly inhibited in the presence of neutralizing antibodies for MK: the number of nephrons formed in vitro was reduced by ∼50% without changes in ureteric bud branching morphogenesis. These results indicated that MK is implicated in the regulation of kidney development by retinoids. These results also suggested that MK plays an important role in the molecular cascade of the epithelial conversion of the metanephric blastema.

scholarly journals Acacetin Inhibits the Growth of STAT3-Activated DU145 Prostate Cancer Cells by Directly Binding to Signal Transducer and Activator of Transcription 3 (STAT3)

Molecules ◽  
2021 ◽  
Vol 26 (20) ◽  
pp. 6204
Author(s):  
Sun Yun ◽  
Yu-Jin Lee ◽  
Jiyeon Choi ◽  
Nam Doo Kim ◽  
Dong Cho Han ◽  
...  
Keyword(s):  
Prostate Cancer ◽  
Cancer Cells ◽  
Nuclear Translocation ◽  
Critical Role ◽  
Cancer Drug ◽  
Dependent Manner ◽  
Signal Transducer ◽  
Prostate Cancer Cells ◽  
Stat3 Phosphorylation ◽  
Transcription 3

Signal transducer and activator of transcription 3 (STAT3) plays a critical role in the formation and growth of human cancer. Therefore, STAT3 is a therapeutic target for cancer drug discovery. Acacetin, a flavone present in various plants, inhibits constitutive and inducible STAT3 activation in STAT3-activated DU145 prostate cancer cells. Acacetin inhibits STAT3 activity by directly binding to STAT3, which we confirmed by a pull-down assay with a biotinylated compound and two level-free methods, namely, a drug affinity responsive target stability (DARTS) experiment and a cellular thermal shift assay (CETSA). Acacetin inhibits STAT3 phosphorylation at the tyrosine 705 residue and nuclear translocation in DU145 cells, which leads to the downregulation of STAT3 target genes. Acacetin then induces apoptosis in a time-dependent manner. Interestingly, acacetin induces the production of reactive oxygen species (ROS) that are not involved in the acacetin-induced inhibition of STAT3 activation because the suppressed p-STAT3 level is not rescued by treatment with GSH or NAC, which are general ROS inhibitors. We also found that acacetin inhibits tumor growth in xenografted nude mice. These results suggest that acacetin, as a STAT3 inhibitor, could be a possible drug candidate for targeting STAT3 for the treatment of cancer in humans.

scholarly journals Chronic Tumor Necrosis Factor-α Treatment Causes Insulin Resistance via Insulin Receptor Substrate-1 Serine Phosphorylation and Suppressor of Cytokine Signaling-3 Induction in 3T3-L1 Adipocytes

Endocrinology ◽  
2007 ◽  
Vol 148 (6) ◽  
pp. 2994-3003 ◽  
Author(s):  
Ken Ishizuka ◽  
Isao Usui ◽  
Yukiko Kanatani ◽  
Agussalim Bukhari ◽  
Jianying He ◽  
...  
Keyword(s):  
Insulin Resistance ◽  
Insulin Receptor ◽  
Tyrosine Phosphorylation ◽  
Insulin Signaling ◽  
Serine Phosphorylation ◽  
Cytokine Signaling ◽  
Insulin Receptor Substrate ◽  
Signal Transducer ◽  
Suppressor Of Cytokine Signaling ◽  
Transcription 3

Serine phosphorylation of insulin receptor substrate (IRS)-1 and the induction of suppressor of cytokine signaling 3 (SOCS3) is recently well documented as the mechanisms for the insulin resistance. However, the relationship between these two mechanisms is not fully understood. In this study, we investigated the involvement of SOCS3 and IRS-1 serine phosphorylation in TNFα-induced insulin resistance in 3T3-L1 adipocytes. TNFα transiently stimulated serine phosphorylation of IRS-1 from 10 min to 1 h, whereas insulin-stimulated IRS-1 tyrosine phosphorylation was inhibited only after TNFα treatment longer than 4 h. These results suggest that serine phosphorylation of IRS-1 alone is not the major mechanism for the inhibited insulin signaling by TNFα. TNFα stimulation longer than 4 h enhanced the expression of SOCS3 and signal transducer and activator of transcription-3 phosphorylation, concomitantly with the production of IL-6. Anti-IL-6 neutralizing antibody ameliorated suppressed insulin signaling by 24 h TNFα treatment, when it partially decreased SOCS3 induction and signal transducer and activator of transcription-3 phosphorylation. These results suggest that SOCS3 induction is involved in inhibited insulin signaling by TNFα. However, low-level expression of SOCS3 by IL-6 or adenovirus vector did not affect insulin-stimulated IRS-1 tyrosine phosphorylation. Interestingly, when IRS-1 serine phosphorylation was enhanced by TNFα or anisomycin in the presence of low-level SOCS3, IRS-1 degradation was remarkably enhanced. Taken together, both IRS-1 serine phosphorylation and SOCS3 induction are necessary, but one of the pair is not sufficient for the inhibited insulin signaling. Chronic TNFα may inhibit insulin signaling effectively because it causes both IRS-1 serine phosphorylation and the following SOCS3 induction in 3T3-L1 adipocytes.

scholarly journals Analysis of Stat3 (signal transducer and activator of transcription 3) dimerization by fluorescence resonance energy transfer in living cells

2004 ◽  
Vol 377 (2) ◽  
pp. 289-297 ◽  
Author(s):  
Antje K. KRETZSCHMAR ◽  
Michaela C. DINGER ◽  
Christian HENZE ◽  
Katja BROCKE-HEIDRICH ◽  
Friedemann HORN
Keyword(s):  
Energy Transfer ◽  
Tyrosine Phosphorylation ◽  
Fluorescence Resonance Energy Transfer ◽  
Fusion Proteins ◽  
Fluorescent Protein ◽  
Resonance Energy Transfer ◽  
Resonance Energy ◽  
Sh2 Domain ◽  
Signal Transducer ◽  
Transcription 3

Signal transducer and activator of transcription 3 (Stat3) dimerization is commonly thought to be triggered by its tyrosine phosphorylation in response to interleukin-6 (IL-6) or other cytokines. Accumulating evidence from in vitro studies, however, suggests that cytoplasmic Stat3 may be associated with high-molecular-mass protein complexes and/or dimerize prior to its activation. To directly study Stat3 dimerization and subcellular localization upon cytokine stimulation, we used live-cell fluorescence spectroscopy and imaging microscopy combined with fluorescence resonance energy transfer (FRET). Stat3 fusion proteins with spectral variants of green fluorescent protein (GFP), cyan fluorescent protein (CFP) and yellow fluorescent protein (YFP) were constructed and expressed in human hepatoma cells (HepG2) and human embryonic kidney cells (HEK-293). Like wild-type Stat3, the fusion proteins redistributed from a preferentially cytoplasmic to nuclear localization upon IL-6 stimulation and supported IL-6-dependent target gene expression. FRET studies in cells co-expressing Stat3–CFP and Stat3–YFP demonstrated that Stat3 dimers exist in the absence of tyrosine phosphorylation. IL-6 induced a 2-fold increase of this basal FRET signal, indicating that tyrosine phosphorylation either increases the dimer/monomer ratio of Stat3 or induces a conformational change of the dimer yielding a higher FRET efficiency. Studies using a mutated Stat3 with a non-functional src-homology 2 (SH2) domain showed that the SH2 domain is essential for dimer formation of phosphorylated as well as non-phosphorylated Stat3. Furthermore, our data show that visualization of normalized FRET signals allow insights into the spatiotemporal dynamics of Stat3 signal transduction.

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