scholarly journals Leptin Suppresses Ghrelin-Induced Activation of Neuropeptide Y Neurons in the Arcuate Nucleus via Phosphatidylinositol 3-Kinase- and Phosphodiesterase 3-Mediated Pathway

Endocrinology ◽  
2007 ◽  
Vol 148 (5) ◽  
pp. 2251-2263 ◽  
Author(s):  
Daisuke Kohno ◽  
Masanori Nakata ◽  
Fumihiko Maekawa ◽  
Ken Fujiwara ◽  
Yuko Maejima ◽  
...  
Keyword(s):  
Adenylate Cyclase ◽  
Neuropeptide Y ◽  
Phospholipase C ◽  
Arcuate Nucleus ◽  
Neuron Activity ◽  
Dependent Manner ◽  
Phosphatidylinositol 3 Kinase ◽  
Adult Rats ◽  
Phosphodiesterase 3 ◽  
Phosphatidylinositol 3

Neuropeptide Y (NPY) neurons in the hypothalamic arcuate nucleus (ARC) play a central role in stimulation of feeding. They sense and integrate peripheral and central signals, including ghrelin and leptin. However, the mechanisms of interaction of these hormones in NPY neurons are largely unknown. This study explored the interaction and underlying signaling cross talk between ghrelin and leptin in NPY neurons. Cytosolic Ca2+ concentration ([Ca2+]i) in single neurons isolated from ARC of adult rats was measured by fura-2 microfluorometry. Ghrelin increased [Ca2+]i in 31% of ARC neurons. The [Ca2+]i increases were inhibited by blockers of phospholipase C, adenylate cyclase, and protein kinase A. Ghrelin-induced [Ca2+]i increases were suppressed by subsequent administration of leptin. Fifteen of 18 ghrelin-activated, leptin-suppressed neurons (83%) contained NPY. Leptin suppression of ghrelin responses was prevented by pretreatment with inhibitors of phosphatidylinositol 3-kinase and phosphodiesterase 3 (PDE3) but not MAPK. ATP-sensitive potassium channel inhibitors and activators did not prevent and mimic leptin suppression, respectively. Although leptin phosphorylated signal-transducer and activator of transcription 3 (STAT3) in NPY neurons, neither STAT3 inhibitor nor genetic STAT3 deletion altered leptin suppression of ghrelin responses. Furthermore, orexigenic effect of intracerebroventricular ghrelin in rats was counteracted by leptin in a PDE3-dependent manner. These findings indicate that ghrelin increases [Ca2+]i via mechanisms depending on phospholipase C and adenylate cyclase-PKA pathways in ARC NPY neurons and that leptin counteracts ghrelin responses via a phosphatidylinositol 3-kinase-PDE3 pathway. This interaction may play an important role in regulating ARC NPY neuron activity and, thereby, feeding.

scholarly journals Efficient coupling with phosphatidylinositol 3-kinase, but not phospholipase C gamma or GTPase-activating protein, distinguishes ErbB-3 signaling from that of other ErbB/EGFR family members.

1994 ◽  
Vol 14 (1) ◽  
pp. 492-500 ◽  
Author(s):  
P Fedi ◽  
J H Pierce ◽  
P P di Fiore ◽  
M H Kraus
Keyword(s):  
Growth Factor ◽  
Phospholipase C ◽  
Recombinant Expression ◽  
Chimeric Receptor ◽  
Phosphatidylinositol 3 Kinase ◽  
Gtpase Activating Protein ◽  
Ligand Activation ◽  
Phospholipase C Gamma ◽  
Nih 3T3 ◽  
Phosphatidylinositol 3

Recombinant expression of a chimeric EGFR/ErbB-3 receptor in NIH 3T3 fibroblasts allowed us to investigate cytoplasmic events associated with ErbB-3 signal transduction upon ligand activation. An EGFR/ErbB-3 chimera was expressed on the surface of NIH 3T3 transfectants as two classes of receptors possessing epidermal growth factor (EGF) binding affinities comparable to those of the wild-type EGF receptor (EGFR). EGF induced autophosphorylation in vivo of the chimeric receptor and DNA synthesis of EGFR/ErbB-3 transfectants with a dose response similar to that of EGFR transfectants. However, the ErbB-3 and EGFR cytoplasmic domains exhibited striking differences in their interactions with several known tyrosine kinase substrates. We demonstrated strong association of phosphatidylinositol 3-kinase activity with the chimeric receptor upon ligand activation comparable in efficiency with that of the platelet-derived growth factor receptor, while the EGFR exhibited a 10- to 20-fold-lower efficiency in phosphatidylinositol 3-kinase recruitment. By contrast, both phospholipase C gamma and GTPase-activating protein failed to associate with or be phosphorylated by the ErbB-3 cytoplasmic domain under conditions in which they coupled with the EGFR. In addition, though certain signal transmitters, including Shc and GRB2, were recruited by both kinases, EGFR and ErbB-3 elicited tyrosine phosphorylation of distinct sets of intracellular substrates. Thus, our findings show that ligand activation of the ErbB-3 kinase triggers a cytoplasmic signaling pathway that hitherto is unique within this receptor subfamily.

scholarly journals T Cell Activation-dependent Association between the p85 Subunit of the Phosphatidylinositol 3-Kinase and Grb2/Phospholipase C-γ1-binding Phosphotyrosyl Protein pp36/38

1995 ◽  
Vol 270 (34) ◽  
pp. 20177-20182 ◽  
Author(s):  
Toru Fukazawa ◽  
Kris A. Reedquist ◽  
Govindaswamy Panchamoorthy ◽  
Stephen Soltoff ◽  
Thomas Trub ◽  
...  
Keyword(s):  
T Cell ◽  
Phospholipase C ◽  
T Cell Activation ◽  
Cell Activation ◽  
Phosphatidylinositol 3 Kinase ◽  
Phosphatidylinositol 3

scholarly journals Oxidative stress increases megalin expression in the renal proximal tubules during the normoalbuminuric stage of diabetes mellitus

2018 ◽  
Vol 314 (3) ◽  
pp. F462-F470 ◽  
Author(s):  
Yoshifumi Kurosaki ◽  
Akemi Imoto ◽  
Fumitaka Kawakami ◽  
Masanori Yokoba ◽  
Tsuneo Takenaka ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Diabetes Mellitus ◽  
Hydrogen Peroxide ◽  
High Glucose ◽  
Renal Cortex ◽  
Dependent Manner ◽  
Phosphatidylinositol 3 Kinase ◽  
Phosphorylated Akt ◽  
Stress Dependent ◽  
Phosphatidylinositol 3

Megalin, an endocytic receptor expressed in proximal tubule cells, plays a critical role in renal tubular protein reabsorption and is associated with the albuminuria observed in diabetic nephropathy. We have previously reported increased oxidant production in the renal cortex during the normoalbuminuric stage of diabetes mellitus (DM); however, the relationship between oxidative stress and renal megalin expression during the normoalbuminuric stage of DM remains unclear. In the present study, we evaluated whether oxidative stress affects megalin expression in the normoalbuminuric stage of DM in a streptozotocin-induced diabetic rat model and in immortalized human proximal tubular cells (HK-2). We demonstrated that increased expression of renal megalin accompanies oxidative stress during the early stage of DM, before albuminuria development. Telmisartan treatment prevented the diabetes-induced elevation in megalin level, possibly through an oxidative stress-dependent mechanism. In HK-2 cells, hydrogen peroxide significantly increased megalin levels in a dose- and time-dependent manner; however, the elevation in megalin expression was decreased following prolonged exposure to severe oxidative stress induced by 0.4 mmol/l hydrogen peroxide. High-glucose treatment also significantly increased megalin expression in HK-2 cells. Concurrent administration of the antioxidant N-acetyl-cysteine blocked the effects of high glucose on megalin expression. Furthermore, the hydrogen peroxide-induced increase in megalin expression was blocked by treatment with phosphatidylinositol 3-kinase and Akt inhibitors. Increase of phosphorylated Akt expression was also seen in the renal cortex of diabetic rats. Taken together, our results indicate that mild oxidative stress increases renal megalin expression through the phosphatidylinositol 3-kinase-Akt pathway in the normoalbuminuric stage of DM.

Efficient coupling with phosphatidylinositol 3-kinase, but not phospholipase C gamma or GTPase-activating protein, distinguishes ErbB-3 signaling from that of other ErbB/EGFR family members

1994 ◽  
Vol 14 (1) ◽  
pp. 492-500
Author(s):  
P Fedi ◽  
J H Pierce ◽  
P P di Fiore ◽  
M H Kraus
Keyword(s):  
Growth Factor ◽  
Phospholipase C ◽  
Recombinant Expression ◽  
Chimeric Receptor ◽  
Phosphatidylinositol 3 Kinase ◽  
Gtpase Activating Protein ◽  
Ligand Activation ◽  
Phospholipase C Gamma ◽  
Nih 3T3 ◽  
Phosphatidylinositol 3

Recombinant expression of a chimeric EGFR/ErbB-3 receptor in NIH 3T3 fibroblasts allowed us to investigate cytoplasmic events associated with ErbB-3 signal transduction upon ligand activation. An EGFR/ErbB-3 chimera was expressed on the surface of NIH 3T3 transfectants as two classes of receptors possessing epidermal growth factor (EGF) binding affinities comparable to those of the wild-type EGF receptor (EGFR). EGF induced autophosphorylation in vivo of the chimeric receptor and DNA synthesis of EGFR/ErbB-3 transfectants with a dose response similar to that of EGFR transfectants. However, the ErbB-3 and EGFR cytoplasmic domains exhibited striking differences in their interactions with several known tyrosine kinase substrates. We demonstrated strong association of phosphatidylinositol 3-kinase activity with the chimeric receptor upon ligand activation comparable in efficiency with that of the platelet-derived growth factor receptor, while the EGFR exhibited a 10- to 20-fold-lower efficiency in phosphatidylinositol 3-kinase recruitment. By contrast, both phospholipase C gamma and GTPase-activating protein failed to associate with or be phosphorylated by the ErbB-3 cytoplasmic domain under conditions in which they coupled with the EGFR. In addition, though certain signal transmitters, including Shc and GRB2, were recruited by both kinases, EGFR and ErbB-3 elicited tyrosine phosphorylation of distinct sets of intracellular substrates. Thus, our findings show that ligand activation of the ErbB-3 kinase triggers a cytoplasmic signaling pathway that hitherto is unique within this receptor subfamily.

scholarly journals Both Src-Dependent and -Independent Mechanisms Mediate Phosphatidylinositol 3-Kinase Regulation of Colony-Stimulating Factor 1-Activated Mitogen-Activated Protein Kinases in Myeloid Progenitors

2000 ◽  
Vol 20 (18) ◽  
pp. 6779-6798 ◽  
Author(s):  
Angel W.-M. Lee ◽  
David J. States
Keyword(s):  
Kinase Inhibitors ◽  
Pi3 Kinase ◽  
Dominant Negative ◽  
Dependent Manner ◽  
Colony Stimulating Factor ◽  
Phosphatidylinositol 3 Kinase ◽  
Stimulating Factor ◽  
In Cells ◽  
Phosphatidylinositol 3 ◽  
Myeloid Progenitors

ABSTRACT Colony-stimulating factor 1 (CSF-1) supports the proliferation, survival, and differentiation of bone marrow-derived cells of the monocytic lineage. In the myeloid progenitor 32D cell line expressing CSF-1 receptor (CSF-1R), CSF-1 activation of the extracellular signal-regulated kinase (ERK) pathway is both Ras and phosphatidylinositol 3-kinase (PI3-kinase) dependent. PI3-kinase inhibition did not influence events leading to Ras activation. Using the activity of the PI3-kinase effector, Akt, as readout, studies with dominant-negative and oncogenic Ras failed to place PI3-kinase downstream of Ras. Thus, PI3-kinase appears to act in parallel to Ras. PI3-kinase inhibitors enhanced CSF-1-stimulated A-Raf and c-Raf-1 activities, and dominant-negative A-Raf but not dominant-negative c-Raf-1 reduced CSF-1-provoked ERK activation, suggesting that A-Raf mediates a part of the stimulatory signal from Ras to MEK/ERK, acting in parallel to PI3-kinase. Unexpectedly, a CSF-1R lacking the PI3-kinase binding site (ΔKI) remained capable of activating MEK/ERK in a PI3-kinase-dependent manner. To determine if Src family kinases (SFKs) are involved, we demonstrated that CSF-1 activated Fyn and Lyn in cells expressing wild-type (WT) or ΔKI receptors. Moreover, CSF-1-induced Akt activity in cells expressing ΔKI is SFK dependent since Akt activation was prevented by pharmacological or genetic inhibition of SFK activity. The docking protein Gab2 may link SFK to PI3-kinase. CSF-1 induced Gab2 tyrosyl phosphorylation and association with PI3-kinase in cells expressing WT or ΔKI receptors. However, only in ΔKI cells are these events prevented by PP1. Thus in myeloid progenitors, CSF-1 can activate the PI3-kinase/Akt pathway by at least two mechanisms, one involving direct receptor binding and one involving SFKs.

scholarly journals Wortmannin, a specific inhibitor of phosphatidylinositol-3-kinase, induces accumulation of DNA double-strand breaks

2020 ◽  
Vol 61 (2) ◽  
pp. 171-176 ◽  
Author(s):  
Makoto Ihara ◽  
Kazuko Shichijo ◽  
Satoshi Takeshita ◽  
Takashi Kudo
Keyword(s):  
Dna Damage ◽  
Specific Inhibitor ◽  
Double Strand Breaks ◽  
Dependent Manner ◽  
Dna Double Strand Breaks ◽  
Phosphatidylinositol 3 Kinase ◽  
Strand Breaks ◽  
Γ Ray ◽  
Scid Cells ◽  
Phosphatidylinositol 3

Abstract Wortmannin, a fungal metabolite, is a specific inhibitor of the phosphatidylinositol 3-kinase (PI3K) family, which includes double-stranded DNA dependent protein kinase (DNA-PK) and ataxia telangiectasia mutated kinase (ATM). We investigated the effects of wortmannin on DNA damage in DNA-PK-deficient cells obtained from severe combined immunodeficient mice (SCID cells). Survival of wortmannin-treated cells decreased in a concentration-dependent manner. After treatment with 50 μM wortmannin, survival decreased to 60% of that of untreated cells. We observed that treatment with 20 and 50 μM wortmannin induced DNA damage equivalent to that by 0.37 and 0.69 Gy, respectively, of γ-ray radiation. The accumulation of DNA double-strand breaks (DSBs) in wortmannin-treated SCID cells was assessed using pulsed-field gel electrophoresis. The maximal accumulation was observed 4 h after treatment. Moreover, the presence of DSBs was confirmed by the ability of nuclear extracts from γ-ray-irradiated SCID cells to produce in vitro phosphorylation of histone H2AX. These results suggest that wortmannin induces cellular toxicity by accumulation of spontaneous DSBs through inhibition of ATM.

scholarly journals Statin-induced Ras Activation Integrates the Phosphatidylinositol 3-Kinase Signal to Akt and MAPK for Bone Morphogenetic Protein-2 Expression in Osteoblast Differentiation

2006 ◽  
Vol 282 (7) ◽  
pp. 4983-4993 ◽  
Author(s):  
Nandini Ghosh-Choudhury ◽  
Chandi Charan Mandal ◽  
Goutam Ghosh Choudhury
Keyword(s):  
Bone Morphogenetic Protein ◽  
Osteoblast Differentiation ◽  
Dominant Negative ◽  
Bone Morphogenetic Protein 2 ◽  
Regulatory Subunit ◽  
Type I ◽  
Dependent Manner ◽  
Phosphatidylinositol 3 Kinase ◽  
Morphogenetic Protein ◽  
Phosphatidylinositol 3

Lovastatin promotes osteoblast differentiation by increasing bone morphogenetic protein-2 (BMP-2) expression. We demonstrate that lovastatin stimulates tyrosine phosphorylation of the p85 regulatory subunit of phosphatidylinositol 3-kinase (PI3K), leading to an increase in its kinase activity in osteoblast cells. Inhibition of PI3K ameliorated expression of the osteogenic markers alkaline phosphatase, type I collagen, osteopontin, and BMP-2. Expression of dominant-negative PI3K and PTEN, an inhibitor of PI3K signaling, significantly attenuated lovastatin-induced transcription of BMP-2. Akt kinase was also activated in a PI3K-dependent manner. However, our data suggest involvement of an additional signaling pathway. Lovastatin-induced Erk1/2 activity contributed to BMP-2 transcription. Inhibition of PI3K abrogated Erk1/2 activity in response to lovastatin, indicating the presence of a signal relay between them. We provide, as a mechanism of this cross-talk, the first evidence that lovastatin stimulates rapid activation of Ras, which associates with and activates PI3K in the plasma membrane, which in turn regulates Akt and Erk1/2 to induce BMP-2 expression for osteoblast differentiation.

343 PHOSPHATIDYLINOSITOL 3-KINASE IS INVOLVED IN THE MAINTENANCE OF METAPHASE II ARREST IN PORCINE OOCYTES MATURED IN VITRO

2010 ◽  
Vol 22 (1) ◽  
pp. 328
Author(s):  
N. Kashiwazaki ◽  
M. Shimada ◽  
J. Ito
Keyword(s):  
Protein Kinase ◽  
Time Dependent ◽  
Kinase Assay ◽  
Dependent Manner ◽  
Phosphatidylinositol 3 Kinase ◽  
Mapk Activity ◽  
Pronuclear Formation ◽  
Pkb Phosphorylation ◽  
Phosphatidylinositol 3

It has been reported that phosphatidylinositol 3-kinase (PI3K)-protein kinase B (PKB) pathway plays a crucial role in the meiotic resumption and progression to the metaphase II (MII) stage of oocytes. However, the role of this pathway in meiotic arrest at the MII stage (cytostatic activity) is not well understood. In this study, the effect of a PI3K inhibitor, LY294002, on the mitogen-activated protein kinase (MAPK) and p34cdc2 kinase activities of matured porcine oocytes was examined. Immature oocytes were collected from ovaries and cultured in modified NCSU37 up to 48 hr. After culture, cumulus cells were removed and oocytes were cultured up to 24 h in medium supplemented with 25 or 50 μM LY294002. Groups of 10 or 20 oocytes were collected at each culture period for in vitro kinase assay of p34cdc2 kinase and MAPK, respectively. Groups of 40 oocytes were also used for detection of PKB phosphorylation by Western blotting. After maturation culture, both the p34cdc2 kinase and MAPK activities in the oocytes were gradually decreased in a time-dependent manner. Although 25 μM LY294002 did not affect either the p34cdc2 kinase or MAPK activities, 50 μM LY294002 suppressed the PKB phosphorylation and slightly decreased MAPK activity, but not the p34cdc2 kinase activity. Next, the effect of 10 μM Ca2+ ionophore which was reported as inducing a transient decrease of p342+ kinase but not MAPK activities, was examined in LY294002-treated oocytes. Pronuclear formation of the oocytes was also evaluated by the aceto-orcein staining. By additional treatment with LY294002 after Ca2+ ionophore, both the MAPK and p34cdc2 kinase activities were decreased in a time-dependent manner, concomitantly with improvement of pronuclear formation. Therefore, we concluded that PI3K is possibly involved in the maintenance of MAPK activity in matured porcine oocytes. The work was supported in part by Grant-in-Aid for Scientific Research from JSPS (KAKENHI) (21789253) to J.I. This work was also supported in part by the Promotion and Mutual Aid Corporation for Private Schools of Japan through a Grant-in-Aid for Matching Fund Subsidy for Private Universities to J.I. and N.K.

Leptin Constrains Phospholipase C-Protein Kinase C-Induced Insulin Secretion via a Phosphatidylinositol 3-Kinase-Dependent Pathway

2003 ◽  
Vol 228 (2) ◽  
pp. 175-182 ◽  
Author(s):  
Joo-Won Lee ◽  
Andrew G. Swick ◽  
Dale R. Romsos
Keyword(s):  
Protein Kinase C ◽  
Insulin Secretion ◽  
Protein Kinase ◽  
Phospholipase C ◽  
Phosphatidylinositol 3 Kinase ◽  
C Protein ◽  
Kinase C ◽  
Pka Pathway ◽  
Stimulation Of ◽  
Phosphatidylinositol 3

Leptin-deficient Lepob/Lepob mice hypersecrete insulin in response to acetylcholine stimulation of the phospholipase C-protein kinase C (PLC-PKC) pathway, and leptin constrains this hypersecretion. Leptin has been reported to activate phosphatidylinositol 3-kinase (PI 3-K) and subsequently phosphodiesterase (PDE) to impair protein kinase A (PKA)-induced insulin secretion from cultured islets of neonatal rats. We determined if PKA-induced insulin secretion was also hyperresponsive in Islets from Lepob/Lepob mice, and if leptin impaired this pathway in islets from these mice. Additionally, the possible role for PI 3-K and PDE in leptin-induced control of acetylcholine-induced insulin secretion was examined. Stimulation of Insulin secretion with GLP-1, forskolin (an activator of adenylyl cyclase), or IBMX (an inhibitor of PDE) did not cause hypersecretion of insulin from islets of young Lepob/Lepob mice, and leptin did not inhibit GLP-1-induced insulin secretion from islets of these mice. Inhibition of PDE with IBMX also did not block leptin-induced inhibition of acetylcholine-mediated insulin secretion from islets of Lepob/Lepob mice. But, preincubation of islets with wortmannin, an Inhibitor of PI 3-K activity, blocked the ability of leptin to constrain acetylcholine-induced insulin secretion from islets of Lepob/Lepob mice. We conclude that the capacity of the PKA pathway to stimulate insulin secretion is not increased in islets from young Lepob/Lepob mice, and that leptin does not regulate this pathway in islets from mice. Leptin may stimulate PI 3-K to constrain PLC-PKC-induced insulin secretion from Islets of Lepob/Lepob mice.

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