scholarly journals The Q43L mutant of neuregulin 2β is a pan-ErbB receptor antagonist

2012 ◽  
Vol 443 (1) ◽  
pp. 133-144 ◽  
Author(s):  
Kristy J. Wilson ◽  
Christopher P. Mill ◽  
Richard M. Gallo ◽  
Elizabeth M. Cameron ◽  
Henry VanBrocklin ◽  
...  
Keyword(s):  
Cell Proliferation ◽  
Tyrosine Phosphorylation ◽  
Kinase Activity ◽  
Growth Factor Receptor ◽  
Erbb Receptor ◽  
Pharmacological Agents ◽  
Akt Phosphorylation ◽  
Agonist Stimulation ◽  
Phosphoinositide 3 Kinase ◽  
Stimulation Of

The ErbB4 receptor tyrosine kinase possesses both tumour suppressor and oncogenic activities. Thus pharmacological agents are needed to help elucidate ErbB4 functions. However, limitations of existing ErbB4 agonists and antagonists have led us to seek novel ErbB4 antagonists. The Q43L mutant of the ErbB4 agonist NRG2β (neuregulin 2β) stimulates ErbB4 tyrosine phosphorylation, yet fails to stimulate ErbB4 coupling to cell proliferation. Thus in the present paper we hypothesize that NRG2β/Q43L may be an ErbB4 antagonist. NRG2β/Q43L competitively antagonizes agonist stimulation of ErbB4 coupling to cell proliferation. NRG2β/Q43L stimulates less ErbB4 tyrosine phosphorylation than does NRG2β. In addition, NRG2β stimulation of cell proliferation requires PI3K (phosphoinositide 3-kinase) activity and NRG2β stimulates greater Akt phosphorylation than does NRG2β/Q43L. Moreover, EGFR [EGF (epidermal growth factor) receptor] kinase activity (but not that of ErbB4) is critical for coupling ErbB4 to proliferation. Experiments utilizing ErbB4 splicing isoforms and mutants suggest that NRG2β and NRG2β/Q43L may differentially stimulate ErbB4 coupling to the transcriptional co-regulator YAP (Yes-associated protein). Finally, NRG2β/Q43L competitively antagonizes agonist stimulation of EGFR and ErbB2/ErbB3, indicating that NRG2β/Q43L is a pan-ErbB antagonist. Thus we postulate that NRG2β/Q43L and other antagonistic ligands stimulate ErbB tyrosine phosphorylation on a set of residues distinct from that stimulated by agonists, thus suggesting a novel mechanism of ErbB receptor regulation. Moreover, NRG2β/Q43L and related ligand-based antagonists establish a paradigm for the discovery of anti-ErbB therapeutics.

scholarly journals Compartment-specific regulation of phosphoinositide 3-kinase by platelet-derived growth factor and insulin in 3T3-L1 adipocytes

1996 ◽  
Vol 318 (1) ◽  
pp. 55-60 ◽  
Author(s):  
Barbara T. NAVÉ ◽  
RichardHAIGH J ◽  
Amanda C HAYWARD ◽  
Kenneth SIDDLE ◽  
Peter R. SHEPHERD
Keyword(s):  
Growth Factors ◽  
Growth Factor ◽  
Tyrosine Phosphorylation ◽  
Kinase Activity ◽  
Specific Activity ◽  
Subcellular Fractionation ◽  
Platelet Derived Growth Factor ◽  
Specific Regulation ◽  
Phosphoinositide 3 Kinase ◽  
Stimulation Of

To understand how the stimulation of phosphoinositide 3-kinase (PI 3-kinase) by different growth factors can activate different subsets of downstream responses, growth-factor regulation of PI 3-kinase activity at different intracellular locations was investigated in 3T3-L1 adipocytes. Insulin caused a large stimulation of glucose transport and stimulated recruitment of transferrin receptors to the plasma membrane (PM) in these cells, whereas platelet-derived growth factor (PDGF)-bb was virtually without effect on these responses. Subcellular fractionation studies after stimulation with PDGF-bb or insulin revealed a differential effect of these growth factors on subcellular localization of PI 3-kinase activity. PDGF was more effective than insulin in stimulating PI 3-kinase activity and recruiting the p85α PI 3-kinase adaptor subunit in the fraction containing the PM. However, in the microsomal fraction insulin significantly increased PI 3-kinase activity and p85α levels, whereas PDGF was almost without effect. In the microsomal membrane fraction the insulin-stimulated recruitment of p85α closely matched the increase PI 3-kinase activity, indicating that insulin stimulation of PI 3-kinase in this fraction is largely due to recruitment of PI 3-kinase enzyme rather than alterations in specific activity. Insulin-stimulated recruitment of p85α to the microsomal membranes was not inhibited by wortmannin, indicating that PI 3-kinase activity was not required for this process. A further level of compartment-specific regulation of PI 3-kinase in response to PDGF was revealed by the finding that tyrosine phosphorylation of the p85α adaptor was restricted to the PM-containing fraction. Insulin had no effect on p85 tyrosine phosphorylation in either fraction. In summary, these results suggest a basis by which insulin and PDGF could both use PI 3-kinase signalling cascades but achieve different signalling outcomes.

scholarly journals A complex interplay between Akt, TSC2 and the two mTOR complexes

2009 ◽  
Vol 37 (1) ◽  
pp. 217-222 ◽  
Author(s):  
Jingxiang Huang ◽  
Brendan D. Manning
Keyword(s):  
Growth Factor ◽  
Kinase Activity ◽  
Mammalian Target Of Rapamycin ◽  
Inhibitory Effects ◽  
Complex Interplay ◽  
Additional Level ◽  
Phosphoinositide 3 Kinase ◽  
The Relationship ◽  
Stimulation Of ◽  
In Cells

Akt/PKB (protein kinase B) both regulates and is regulated by the TSC (tuberous sclerosis complex) 1–TSC2 complex. Downstream of PI3K (phosphoinositide 3-kinase), Akt phosphorylates TSC2 directly on multiple sites. Although the molecular mechanism is not well understood, these phosphorylation events relieve the inhibitory effects of the TSC1–TSC2 complex on Rheb and mTORC1 [mTOR (mammalian target of rapamycin) complex] 1, thereby activating mTORC1 in response to growth factors. Through negative-feedback mechanisms, mTORC1 activity inhibits growth factor stimulation of PI3K. This is particularly evident in cells and tumours lacking the TSC1–TSC2 complex, where Akt signalling is severely attenuated due, at least in part, to constitutive activation of mTORC1. An additional level of complexity in the relationship between Akt and the TSC1–TSC2 complex has recently been uncovered. The growth-factor-stimulated kinase activity of mTORC2 [also known as the mTOR–rictor (rapamycin-insensitive companion of mTOR) complex], which normally enhances Akt signalling by phosphorylating its hydrophobic motif (Ser473), was found to be defective in cells lacking the TSC1–TSC2 complex. This effect on mTORC2 can be separated from the inhibitory effects of the TSC1–TSC2 complex on Rheb and mTORC1. The present review discusses our current understanding of the increasingly complex functional interactions between Akt, the TSC1–TSC2 complex and mTOR, which are fundamentally important players in a large variety of human diseases.

scholarly journals Signalling pathways of an insulin-mimetic phosphoinositolglycan–peptide in muscle and adipose tissue

1998 ◽  
Vol 330 (1) ◽  
pp. 277-286 ◽  
Author(s):  
Alexandra KESSLER ◽  
Günter MÜLLER ◽  
Susanne WIED ◽  
Anna CRECELIUS ◽  
Jürgen ECKEL
Keyword(s):  
Adipose Tissue ◽  
Insulin Receptor ◽  
Tyrosine Phosphorylation ◽  
Glucose Transport ◽  
Insulin Action ◽  
Kinase Activity ◽  
Signalling Pathways ◽  
Insulin Mimetic ◽  
Isolated Adipocytes ◽  
Stimulation Of

A novel phosphoinositolglycan-peptide (PIG-P) from the yeast Saccharomyces cerevisiae potently mimicks insulin action on glucose transport and metabolism in rat muscle and adipose tissue. The aim of the present study was to elucidate the cellular signalling pathways of this insulin-mimetic compound. Rapid onset and reversibility of PIG-P action on glucose transport were observed in isolated adipocytes with a half-time of transport stimulation of 6-8 min (insulin less than 5 min). Combined treatment with PIG-P and insulin indicated additive stimulation of glucose transport at submaximal concentrations and non-additive action of both agents at maximal doses. The tyrosine phosphorylation of insulin receptor substrate-1 (IRS-1) was markedly increased in response to PIG-P in rat cardiomyocytes without any effect on the tyrosine phosphorylation of the insulin receptor β-subunit. PIG-P action in these cells was accompanied by phosphorylation/dephosphorylation of several proteins with molecular masses of 15-30 kDa, a response not detected with insulin. Downstream signalling of IRS-1 was then analysed by monitoring IRS-1-associated phosphatidylinositol 3-kinase (PI 3-kinase) activity in cardiomyocytes. A stable (2 and 15 min incubation with PIG-P) 7-fold stimulation corresponding to about 50% of insulin action could be detected. Increased tyrosine phosphorylation of IRS-1 and enhanced PI 3-kinase activity in response to PIG-P independent of the insulin receptor was also observed in isolated adipocytes. Involvement of PI 3-kinase in PIG-P action was subsequently confirmed by the dose-dependent inhibition of PIG-P-activated glucose transport in rat diaphragm and adipocytes by the PI 3-kinase inhibitors wortmannin and LY294002. These data suggest divergent upstream signalling by insulin and PIG-P involving phosphoproteins not affected by insulin. However, PIG-P and insulin action converge at the level of IRS-1 inducing insulin-independent PI 3-kinase-mediated signalling to glucose transport.

scholarly journals Tyrosine 766 in the fibroblast growth factor receptor-1 is required for FGF-stimulation of phospholipase C, phospholipase D, phospholipase A(2), phosphoinositide 3-kinase and cytoskeletal reorganisation in porcine aortic endothelial cells

2000 ◽  
Vol 113 (4) ◽  
pp. 643-651 ◽  
Author(s):  
M.J. Cross ◽  
M.N. Hodgkin ◽  
S. Roberts ◽  
E. Landgren ◽  
M.J. Wakelam ◽  
...  
Keyword(s):  
Growth Factor ◽  
Fibroblast Growth Factor ◽  
Fibroblast Growth Factor Receptor ◽  
Growth Factor Receptor ◽  
Fibroblast Growth ◽  
Wild Type ◽  
Aortic Endothelial Cells ◽  
Phosphoinositide 3 Kinase ◽  
Porcine Aortic Endothelial Cells ◽  
Stimulation Of

Fibroblast growth factor-mediated signalling was studied in porcine aortic endothelial cells expressing either wild-type fibroblast growth factor receptor-1 or a mutant receptor (Y766F) unable to bind phospholipase C-(γ). Stimulation of cells expressing the wild-type receptor resulted in activation of phospholipases C, D and A(2) and increased phosphoinositide 3-kinase activity. Stimulation of the wild-type receptor also resulted in stress fibre formation and a cellular shape change. Cells expressing the Y766F mutant receptor failed to stimulate phospholipase C, D and A(2) as well as phosphoinositide 3-kinase. Furthermore, no stress fibre formation or shape change was observed. Both the wild-type and Y766F receptor mutant activated MAP kinase and elicited proliferative responses in the porcine aortic endothelial cells. Thus, fibroblast growth factor receptor-1 mediated activation of phospholipases C, D and A(2) and phosphoinositide 3-kinase was dependent on tyrosine 766. Furthermore, whilst tyrosine 766 was not required for a proliferative response, it was required for fibroblast growth factor receptor-1 mediated cytoskeletal reorganisation.

scholarly journals Mechanism of Rapid Nuclear Factor-E2-Related Factor 2 (Nrf2) Activation via Membrane-Associated Estrogen Receptors: Roles of NADPH Oxidase 1, Neutral Sphingomyelinase 2 and Epidermal Growth Factor Receptor (EGFR)

Antioxidants ◽  
2019 ◽  
Vol 8 (3) ◽  
pp. 69 ◽  
Author(s):  
Tetsuro Ishii ◽  
Eiji Warabi
Keyword(s):  
Cell Proliferation ◽  
Epidermal Growth Factor Receptor ◽  
Estrogen Receptors ◽  
Growth Factor Receptor ◽  
Related Factor ◽  
Nuclear Factor ◽  
Nrf2 Activation ◽  
Nadph Oxidase 1 ◽  
Epidermal Growth ◽  
Stimulation Of

Membrane-associated estrogen receptors (ER)-α36 and G protein-coupled estrogen receptor (GPER) play important roles in the estrogen’s rapid non-genomic actions including stimulation of cell proliferation. Estrogen via these receptors induces rapid activation of transcription factor nuclear factor-E2-related factor 2 (Nrf2), a master regulator of detoxification and antioxidant systems, playing a key role in the metabolic reprogramming to support cell proliferation. This review highlights the possible mechanism underlying rapid Nrf2 activation via membrane-associated estrogen receptors by estrogen and phytoestrogens. Stimulation of ER-α36-GPER signaling complex rapidly induces Src-mediated transactivation of epidermal growth factor receptor (EGFR) leading to a kinase-mediated signaling cascade. We propose a novel hypothesis that ER-α36-GPER signaling initially induces rapid and temporal activation of NADPH oxidase 1 to generate superoxide, which subsequently activates redox-sensitive neutral sphingomyelinase 2 generating the lipid signaling mediator ceramide. Generation of ceramide is required for Ras activation and ceramide-protein kinase C ζ-casein kinase 2 (CK2) signaling. Notably, CK2 enhances chaperone activity of the Cdc37-Hsp90 complex supporting activation of various signaling kinases including Src, Raf and Akt (protein kinase B). Activation of Nrf2 may be induced by cooperation of two signaling pathways, (i) Nrf2 stabilization by direct phosphorylation by CK2 and (ii) EGFR-Ras-PI 3 kinase (PI3K)-Akt axis which inhibits glycogen synthase kinase 3β leading to enhanced nuclear transport and stability of Nrf2.

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