scholarly journals Dihydrotestosterone Inhibits Insulin-Stimulated Cyclin D2 Messenger Ribonucleic Acid Expression in Rat Ovarian Granulosa Cells by Reducing the Phosphorylation of Insulin Receptor Substrate-1

Endocrinology ◽  
2006 ◽  
Vol 147 (1) ◽  
pp. 464-471 ◽  
Author(s):  
Pradeep P. Kayampilly ◽  
K. M. J. Menon
Keyword(s):  
Cell Proliferation ◽  
Insulin Receptor ◽  
Mrna Expression ◽  
Granulosa Cell ◽  
Insulin Signaling ◽  
Pi3 Kinase ◽  
Insulin Receptor Substrate ◽  
Cyclin D2 ◽  
Insulin Receptor Substrate 1 ◽  
Erk Phosphorylation

The effect of 5α-dihydrotestosterone (DHT) on insulin-stimulated granulosa cell proliferation was examined using cyclin D2 mRNA as a marker. Granulosa cells from 3-d estradiol-treated immature rats showed a concentration-dependent increase in cyclin D2 mRNA expression in response to insulin. Exposure to DHT reduced the insulin-stimulated cyclin D2 mRNA expression. Inhibition of the two insulin-signaling pathways, ERK and phosphatidylinositol 3 kinase (PI3 kinase), by using specific inhibitors, also reduced this insulin-stimulated response. These results suggest that both ERK and PI3 kinase signaling are involved in insulin stimulated granulosa cell proliferation. DHT exposure resulted in reduced insulin-stimulated ERK phosphorylation. DHT treatment also reduced the insulin mediated insulin receptor substrate-1 and Raf-1 phosphorylation, the upstream molecules of ERK in insulin signaling pathway. Additionally, inhibition of insulin stimulated PI3 kinase activation reduced ERK phosphorylation. The present study therefore shows that the inhibitory effect of DHT on insulin-stimulated granulosa cell proliferation occurs early in the signaling pathway at the level of insulin receptor substrate-1 phosphorylation, leading to reduced ERK phosphorylation and subsequent inhibition of cyclin D2 mRNA expression.

scholarly journals Follicle-Stimulating Hormone Inhibits Adenosine 5′-Monophosphate-Activated Protein Kinase Activation and Promotes Cell Proliferation of Primary Granulosa Cells in Culture through an Akt-Dependent Pathway

Endocrinology ◽  
2009 ◽  
Vol 150 (2) ◽  
pp. 929-935 ◽  
Author(s):  
Pradeep P. Kayampilly ◽  
K. M. J. Menon
Keyword(s):  
Cell Cycle ◽  
Cell Proliferation ◽  
Protein Kinase ◽  
Mrna Expression ◽  
Granulosa Cell ◽  
Granulosa Cells ◽  
Ampk Activation ◽  
Cyclin D2 ◽  
Cell Cycle Inhibitor ◽  
Dependent Pathway

FSH, acting through multiple signaling pathways, regulates the proliferation and growth of granulosa cells, which are critical for ovulation. The present study investigated whether AMP-activated protein kinase (AMPK), which controls the energy balance of the cell, plays a role in FSH-mediated increase in granulosa cell proliferation. Cells isolated from immature rat ovaries were grown in serum-free, phenol red free DMEM-F12 and were treated with FSH (50 ng/ml) for 0, 5, and 15 min. Western blot analysis showed a significant reduction in AMPK activation as observed by a reduction of phosphorylation at thr 172 in response to FSH treatment at all time points tested. FSH also reduced AMPK phosphorylation in a dose-dependent manner with maximum inhibition at 100 ng/ml. The chemical activator of AMPK (5-aminoimidazole-4-carboxamide-1-β-D-ribofuranoside, 0.5 mm) increased the cell cycle inhibitor p27 kip expression significantly, whereas the AMPK inhibitor (compound C, 20 μm) and FSH reduced p27kip expression significantly compared with control. FSH treatment resulted in an increase in the phosphorylation of AMPK at ser 485/491 and a reduction in thr 172 phosphorylation. Inhibition of Akt phosphorylation using Akt inhibitor VIII reversed the inhibitory effect of FSH on thr 172 phosphorylation of AMPK, whereas ERK inhibitor U0126 had no effect. These results show that FSH, through an Akt-dependent pathway, phosphorylates AMPK at ser 481/495 and inhibits its activation by reducing thr 172 phosphorylation. AMPK activation by 5-amino-imidazole-4-carboxamide-1-β-d-ribofuranoside treatment resulted in a reduction of cell cycle regulatory protein cyclin D2 mRNA expression, whereas FSH increased the expression by 2-fold. These results suggest that FSH promotes granulosa cell proliferation by increasing cyclin D2 mRNA expression and by reducing p27 kip expression by inhibiting AMPK activation through an Akt-dependent pathway. FSH stimulates granulosa cell proliferation by reducing cell cycle inhibitor p27 kip through AMP kinase inhibition.

scholarly journals Dynamic Functional Relay between Insulin Receptor Substrate 1 and 2 in Hepatic Insulin Signaling during Fasting and Feeding

2008 ◽  
Vol 8 (1) ◽  
pp. 49-64 ◽  
Author(s):  
Naoto Kubota ◽  
Tetsuya Kubota ◽  
Shinsuke Itoh ◽  
Hiroki Kumagai ◽  
Hideki Kozono ◽  
...  
Keyword(s):  
Insulin Receptor ◽  
Insulin Signaling ◽  
Insulin Receptor Substrate ◽  
Insulin Receptor Substrate 1 ◽  
Hepatic Insulin Signaling

scholarly journals Serine Phosphorylation Proximal to Its Phosphotyrosine Binding Domain Inhibits Insulin Receptor Substrate 1 Function and Promotes Insulin Resistance

2004 ◽  
Vol 24 (21) ◽  
pp. 9668-9681 ◽  
Author(s):  
Yan-Fang Liu ◽  
Avia Herschkovitz ◽  
Sigalit Boura-Halfon ◽  
Denise Ronen ◽  
Keren Paz ◽  
...  
Keyword(s):  
Insulin Resistance ◽  
Insulin Receptor ◽  
Insulin Signaling ◽  
Insulin Treatment ◽  
Binding Domain ◽  
Serine Phosphorylation ◽  
Insulin Receptor Substrate ◽  
Control Mechanisms ◽  
Insulin Receptor Substrate 1 ◽  
Phosphotyrosine Binding Domain

ABSTRACT Ser/Thr phosphorylation of insulin receptor substrate (IRS) proteins negatively modulates insulin signaling. Therefore, the identification of serine sites whose phosphorylation inhibit IRS protein functions is of physiological importance. Here we mutated seven Ser sites located proximal to the phosphotyrosine binding domain of insulin receptor substrate 1 (IRS-1) (S265, S302, S325, S336, S358, S407, and S408) into Ala. When overexpressed in rat hepatoma Fao or CHO cells, the mutated IRS-1 protein in which the seven Ser sites were mutated to Ala (IRS-17A), unlike wild-type IRS-1 (IRS-1WT), maintained its Tyr-phosphorylated active conformation after prolonged insulin treatment or when the cells were challenged with inducers of insulin resistance prior to acute insulin treatment. This was due to the ability of IRS-17A to remain complexed with the insulin receptor (IR), unlike IRS-1WT, which underwent Ser phosphorylation, resulting in its dissociation from IR. Studies of truncated forms of IRS-1 revealed that the region between amino acids 365 to 430 is a main insulin-stimulated Ser phosphorylation domain. Indeed, IRS-1 mutated only at S408, which undergoes phosphorylation in vivo, partially maintained the properties of IRS-17A and conferred protection against selected inducers of insulin resistance. These findings suggest that S408 and additional Ser sites among the seven mutated Ser sites are targets for IRS-1 kinases that play a key negative regulatory role in IRS-1 function and insulin action. These sites presumably serve as points of convergence, where physiological feedback control mechanisms, which are triggered by insulin-stimulated IRS kinases, overlap with IRS kinases triggered by inducers of insulin resistance to terminate insulin signaling.

scholarly journals Reconstitution of Insulin Signaling Pathways in Rat 3Y1 Cells Lacking Insulin Receptor and Insulin Receptor Substrate-1

1998 ◽  
Vol 273 (39) ◽  
pp. 25347-25355 ◽  
Author(s):  
Takanobu Imanaka ◽  
Hideki Hayashi ◽  
Kazuhiro Kishi ◽  
Lihong Wang ◽  
Kazuo Ishii ◽  
...  
Keyword(s):  
Insulin Receptor ◽  
Signaling Pathways ◽  
Insulin Signaling ◽  
Insulin Receptor Substrate ◽  
Insulin Receptor Substrate 1

scholarly journals Nutrients Suppress Phosphatidylinositol 3-Kinase/Akt Signaling via Raptor-Dependent mTOR-Mediated Insulin Receptor Substrate 1 Phosphorylation

2006 ◽  
Vol 26 (1) ◽  
pp. 63-76 ◽  
Author(s):  
Alexandros Tzatsos ◽  
Konstantin V. Kandror
Keyword(s):  
Insulin Receptor ◽  
Mammalian Target Of Rapamycin ◽  
Insulin Dependent Diabetes Mellitus ◽  
Akt Signaling ◽  
Pi3 Kinase ◽  
Dependent Diabetes Mellitus ◽  
Insulin Receptor Substrate ◽  
Insulin Receptor Substrate 1 ◽  
Insulin Dependent ◽  
Phosphatidylinositol 3

ABSTRACT Nutritional excess and/or obesity represent well-known predisposition factors for the development of non-insulin-dependent diabetes mellitus (NIDDM). However, molecular links between obesity and NIDDM are only beginning to emerge. Here, we demonstrate that nutrients suppress phosphatidylinositol 3 (PI3)-kinase/Akt signaling via Raptor-dependent mTOR (mammalian target of rapamycin)-mediated phosphorylation of insulin receptor substrate 1 (IRS-1). Raptor directly binds to and serves as a scaffold for mTOR-mediated phosphorylation of IRS-1 on Ser636/639. These serines lie close to the Y632MPM motif that is implicated in the binding of p85α/p110α PI3-kinase to IRS-1 upon insulin stimulation. Phosphomimicking mutations of these serines block insulin-stimulated activation of IRS-1-associated PI3-kinase. Knockdown of Raptor as well as activators of the LKB1/AMPK pathway, such as the widely used antidiabetic compound metformin, suppress IRS-1 Ser636/639 phosphorylation and reverse mTOR-mediated inhibition on PI3-kinase/Akt signaling. Thus, diabetes-related hyperglycemia hyperactivates the mTOR pathway and may lead to insulin resistance due to suppression of IRS-1-dependent PI3-kinase/Akt signaling.

scholarly journals Enhancement or inhibition of insulin signaling by insulin receptor substrate 1 is cell context dependent.

1994 ◽  
Vol 14 (7) ◽  
pp. 4427-4434 ◽  
Author(s):  
K Yamauchi ◽  
J E Pessin
Keyword(s):  
Insulin Receptor ◽  
Reporter Gene ◽  
Insulin Signaling ◽  
Transcriptional Activation ◽  
Cho Cells ◽  
Chinese Hamster ◽  
Insulin Receptor Substrate ◽  
Expression Plasmid ◽  
Insulin Receptor Substrate 1 ◽  
Downstream Signaling

Insulin treatment of Chinese hamster ovary (CHO) cells expressing high levels of the insulin receptor (CHO/IR cells) activates both c-fos serum response element and activator protein 1 (AP-1) reporter genes approximately 10-fold. In contrast, parental CHO cells display only two- to threefold insulin stimulation of reporter gene activity. Transient transfection of parental CHO cells with an insulin receptor substrate 1 (IRS1) expression plasmid enhanced insulin downstream signaling in a biphasic manner, whereas IRS1 transfection of CHO/IR cells inhibited insulin signaling in a dose-dependent fashion. Further, expression of Grb2 in parental CHO cells had no effect on insulin signaling, whereas Grb2 increased insulin activation of reporter gene expression in CHO/IR cells. These data suggest that the expression levels of various effector molecules can either enhance or inhibit insulin downstream signaling events. To assess the relative effects of various insulin receptor, IRS1, and Grb2 levels on insulin signaling, parental CHO cells were transiently transfected with various combinations of expression plasmids encoding these proteins. Although expression of IRS1 resulted in a biphasic increase of insulin signaling in parental CHO cells, coexpression of IRS1 with the insulin receptor resulted in inhibition of signaling. This inhibition of insulin signaling directly correlated with an increased association of Grb2 with IRS1 and a concomitant sequestration of Grb2 away from Shc. Consistent with the Shc-Grb2 pathway as the major route for insulin-stimulated c-Fos and AP-1 transcriptional activation, the IRS1-mediated inhibition was reversed by transfection with an expression plasmid for Grb2. These data demonstrate that the extent of insulin-stimulated downstream signaling was dependent not only on the levels of individual signaling molecules but also on the formation of multiprotein complexes with specific stoichiometries.

scholarly journals MicroRNA 144 Impairs Insulin Signaling by Inhibiting the Expression of Insulin Receptor Substrate 1 in Type 2 Diabetes Mellitus

PLoS ONE ◽  
2011 ◽  
Vol 6 (8) ◽  
pp. e22839 ◽  
Author(s):  
Dwi Setyowati Karolina ◽  
Arunmozhiarasi Armugam ◽  
Subramaniam Tavintharan ◽  
Michael T. K. Wong ◽  
Su Chi Lim ◽  
...  
Keyword(s):  
Diabetes Mellitus ◽  
Type 2 Diabetes ◽  
Type 2 Diabetes Mellitus ◽  
Insulin Receptor ◽  
Insulin Signaling ◽  
Insulin Receptor Substrate ◽  
Insulin Receptor Substrate 1

scholarly journals Phosphorylation of Human Insulin Receptor Substrate-1 at Serine 629 Plays a Positive Role in Insulin Signaling

Endocrinology ◽  
2007 ◽  
Vol 148 (10) ◽  
pp. 4895-4905 ◽  
Author(s):  
Moulun Luo ◽  
Paul Langlais ◽  
Zhengping Yi ◽  
Natalie Lefort ◽  
Elena A. De Filippis ◽  
...  
Keyword(s):  
Insulin Receptor ◽  
Human Insulin ◽  
Insulin Signaling ◽  
Insulin Receptor Substrate ◽  
Insulin Receptor Substrate 1 ◽  
Positive Role ◽  
Human Insulin Receptor
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