scholarly journals ARIA/HRG regulates AChR epsilon subunit gene expression at the neuromuscular synapse via activation of phosphatidylinositol 3-kinase and Ras/MAPK pathway.

1996 ◽  
Vol 134 (2) ◽  
pp. 465-476 ◽  
Author(s):  
M G Tansey ◽  
G C Chu ◽  
J P Merlie
Keyword(s):  
Tyrosine Kinases ◽  
Mapk Pathway ◽  
Neuromuscular Synapse ◽  
Dominant Negative ◽  
Erbb Receptor ◽  
Phosphatidylinositol 3 Kinase ◽  
Epsilon Subunit ◽  
Subunit Expression ◽  
Phosphatidylinositol 3

AChR-inducing activity (ARIA)/heregulin, a ligand for erbB receptor tyrosine kinases (RTKs), is likely to be one nerve-supplied signal that induces expression of acetylcholine receptor (AChR) genes at the developing neuromuscular junction. Since some RTKs act through Ras and phosphatidylinositol 3-kinase (PI3K), we investigated the role of these pathways in ARIA signaling. Expression of activated Ras or Raf mimicked ARIA-induction of AChR epsilon subunit genes in muscle cells; whereas dominant negative Ras or Raf blocked the effect of ARIA. ARIA rapidly activated erk1 and erk2 and inhibition of both erks also abolished the effect of ARIA. ARIA stimulated association of PI3K with erbB3, expression of an activated PI3K led to ARIA-independent AChR epsilon subunit expression, and inhibition of PI3K abolished the action of ARIA. Thus, synaptic induction of AChR genes requires activation of both Ras/MAPK and PI3K signal transduction pathways.

scholarly journals PI(4,5)P2 controls slit diaphragm formation and endocytosis in Drosophila nephrocytes

2021 ◽  
Author(s):  
Max Gass ◽  
Sarah Borkowsky ◽  
Marie-Luise Lotz ◽  
Rita Schroeter ◽  
Pavel Nedvetsky ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Model System ◽  
Dominant Negative ◽  
Slit Diaphragm ◽  
Phosphatidylinositol 3 Kinase ◽  
Ectopic Activation ◽  
Phosphatidylinositol 4 ◽  
Asymmetrically Distributed ◽  
Phosphatidylinositol 3

Drosophila nephrocytes are an emerging model system for mammalian podocytes and podocyte-associated diseases. Like podocytes, nephrocytes exhibit characteristics of epithelial cells, but the role of phospholipids in polarization of these cells is yet unclear. In epithelia phosphatidylinositol(4,5)bisphosphate (PI(4,5)P2) and phosphatidylinositol(3,4,5)-trisphosphate (PI(3,4,5)P3) are asymmetrically distributed in the plasma membrane and determine apical-basal polarity. Here we demonstrate that both phospholipids are present in the plasma membrane of nephrocytes, but only PI(4,5)P2 accumulates at slit diaphragms. Knockdown of Skittles, a phosphatidylinositol(4)phosphate 5-kinase, which produces PI(4,5)P2, abolished slit diaphragm formation and led to strongly reduced endocytosis. Notably, reduction in PI(3,4,5)P3 by overexpression of PTEN or expression of a dominant-negative phosphatidylinositol-3-Kinase did not affect nephrocyte function, whereas enhanced formation of PI(3,4,5)P3 by constitutively active phosphatidylinositol-3-Kinase resulted in strong slit diaphragm and endocytosis defects by ectopic activation of the Akt/mTOR pathway. Thus, PI(4,5)P2 but not PI(3,4,5)P3 is essential for slit diaphragm formation and nephrocyte function. However, PI(3,4,5)P3 has to be tightly controlled to ensure nephrocyte development.

Expression of a prenylation-deficient Rab4 inhibits the GLUT4 translocation induced by active phosphatidylinositol 3-kinase and protein kinase B

2001 ◽  
Vol 356 (1) ◽  
pp. 143-149 ◽  
Author(s):  
Mireille CORMONT ◽  
Nadine GAUTIER ◽  
Karine ILC ◽  
Yannick Le MARCHAND-BRUSTEL
Keyword(s):  
Protein Kinase ◽  
Protein Kinase B ◽  
Active Form ◽  
Small Gtpase ◽  
Dominant Negative ◽  
Glut4 Translocation ◽  
Phosphatidylinositol 3 Kinase ◽  
Isolated Adipocytes ◽  
Phosphatidylinositol 3

The small GTPase Rab4 has been shown to participate in the subcellular distribution of GLUT4 under both basal and insulin-stimulated conditions in adipocytes. In the present work, we have characterized the effect of Rab4 ΔCT, a prenylation-deficient and thus cytosolic form of Rab4, in this process. We show that the expression of Rab4 ΔCT in freshly isolated adipocytes inhibits insulin-induced GLUT4 translocation, but only when this protein is in its GTP-bound active form. Further, it not only blocks the effect of insulin, but also that of a hyperosmotic shock, but does not interfere with the effect of zinc ions on GLUT4 translocation. Rab4 ΔCT was then shown to prevent GLUT4 translocation induced by the expression of an active form of phosphatidylinositol 3-kinase or of protein kinase B, without altering the activities of the enzymes. Our results are consistent with a role of Rab4 ΔCT acting as a dominant negative protein towards Rab4, possibly by binding to Rab4 effectors.

scholarly journals PI(4,5)P2 Controls Slit Diaphragm Formation and Endocytosis in Drosophila Nephrocytes

2021 ◽  
Author(s):  
Maximilian Gass ◽  
Sarah Borkowsky ◽  
Marie-Luise Lotz ◽  
Rita Schröter ◽  
Pavel Nedvetsky ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Model System ◽  
Dominant Negative ◽  
Slit Diaphragm ◽  
Phosphatidylinositol 3 Kinase ◽  
Ectopic Activation ◽  
Phosphatidylinositol 4 ◽  
Asymmetrically Distributed ◽  
Phosphatidylinositol 3

Abstract Drosophila nephrocytes are an emerging model system for mammalian podocytes and podocyte-associated diseases. Like podocytes, nephrocytes exhibit characteristics of epithelial cells, but the role of phospholipids in polarization of these cells is yet unclear. In epithelia phosphatidylinositol(4,5)bisphosphate (PI(4,5)P2) and phosphatidylinositol(3,4,5)-trisphosphate (PI(3,4,5)P3) are asymmetrically distributed in the plasma membrane and determine apical-basal polarity. Here we demonstrate that both phospholipids are present in the plasma membrane of nephrocytes, but only PI(4,5)P2 accumulates at slit diaphragms. Knockdown of Skittles, a phosphatidylinositol(4)phosphate 5-kinase, which produces PI(4,5)P2, abolished slit diaphragm formation and led to strongly reduced endocytosis. Notably, reduction in PI(3,4,5)P3 by overexpression of PTEN or expression of a dominant-negative phosphatidylinositol-3-Kinase did not affect nephrocyte function, whereas enhanced formation of PI(3,4,5)P3 by constitutively active phosphatidylinositol-3-Kinase resulted in strong slit diaphragm and endocytosis defects by ectopic activation of the Akt/mTOR pathway. Thus, PI(4,5)P2 but not PI(3,4,5)P3 is essential for slit diaphragm formation and nephrocyte function. However, PI(3,4,5)P3 has to be tightly controlled to ensure nephrocyte development.

scholarly journals Role of phosphatidylinositol 3-kinase in oxidative stress-induced disruption of tight junctions. Vol. 278 (2003) 49239-49245

2004 ◽  
Vol 279 (7) ◽  
pp. 6204
Author(s):  
Parimal Sheth ◽  
Shyamali Basuroy ◽  
Chunying Li ◽  
Anjaparavanda P. Naren ◽  
Radhakrishna K. Rao
Keyword(s):  
Oxidative Stress ◽  
Tight Junctions ◽  
Phosphatidylinositol 3 Kinase ◽  
Phosphatidylinositol 3

scholarly journals Novel Role of Phosphatidylinositol 3-Kinase in CD28-mediated Costimulation

2000 ◽  
Vol 276 (12) ◽  
pp. 9003-9008 ◽  
Author(s):  
Yohsuke Harada ◽  
Eri Tanabe ◽  
Ryosuke Watanabe ◽  
Bonnie D. Weiss ◽  
Akira Matsumoto ◽  
...  
Keyword(s):  
Phosphatidylinositol 3 Kinase ◽  
Phosphatidylinositol 3

Stimulation of pro-α1(I) collagen by TGF-β1 in mesangial cells: role of the p38 MAPK pathway

2001 ◽  
Vol 280 (3) ◽  
pp. F495-F504 ◽  
Author(s):  
Beek Yoke Chin ◽  
Amir Mohsenin ◽  
Su Xia Li ◽  
Augustine M. K. Choi ◽  
Mary E. Choi
Keyword(s):  
P38 Mapk ◽  
Intracellular Signaling ◽  
Mesangial Cells ◽  
Mapk Pathway ◽  
Dominant Negative ◽  
Glomerular Mesangial Cells ◽  
Mapk Activation ◽  
Mapk Phosphorylation ◽  
Collagen Mrna

Transforming growth factor-β1(TGF-β1) is a potent inducer of extracellular matrix protein synthesis and a key mediator of renal fibrosis. However, the intracellular signaling mechanisms by which TGF-β1stimulates this process remain incompletely understood. In this report, we examined the role of a major stress-activated intracellular signaling cascade, belonging to the mitogen-activated protein kinase (MAPK) superfamily, in mediating TGF-β1 responses in rat glomerular mesangial cells, using dominant-negative inhibition of TGF-β1 signaling receptors. We first stably transfected rat glomerular mesangial cells with a kinase-deleted mutant TGF-β type II receptor (TβR-IIM) designed to inhibit TGF-β1 signaling in a dominant-negative fashion. Next, expression of TβR-IIM mRNA was confirmed by Northern analysis. Cell surface expression and ligand binding of TβR-IIM protein were demonstrated by affinity cross-linking with 125I-labeled-TGF-β1. TGF-β1 rapidly induced p38 MAPK phosphorylation in wild-type and empty vector (pcDNA3)-transfected control mesangial cells. Interestingly, transfection with dominant-negative TβR-IIM failed to block TGF-β1-induced p38 MAPK phosphorylation. Moreover, dominant-negative TβR-IIMfailed to block TGF-β1-stimulated pro-α1(I) collagen mRNA expression and cellular protein synthesis, whereas TGF-β1-induced extracellular signal-regulated kinase (ERK) 1/ERK2 activation and antiproliferative responses were blocked by TβR-IIM. In the presence of a specific inhibitor of p38 MAPK, SB-203580, TGF-β1 was unable to stimulate pro-α1(I) collagen mRNA expression in the control and TβR-IIM-transfected mesangial cells. Finally, we confirmed that both p38 MAPK activation and pro-α1(I) collagen stimulation were TGF-β1 effects that were abrogated by dominant-negative inhibition of TGF-β type I receptor. Thus we show first demonstration of p38 MAPK activation by TGF-β1 in mesangial cells, and, given the rapid kinetics, this TGF-β1 effect is likely a direct one. Furthermore, our findings suggest that the p38 MAPK pathway functions as a component in the signaling of pro-α1(I) collagen induction by TGF-β1 in mesangial cells.

scholarly journals cAMP-stimulated Na+ transport in H441 distal lung epithelial cells: role of PKA, phosphatidylinositol 3-kinase, and sgk1

2004 ◽  
Vol 287 (4) ◽  
pp. L843-L851 ◽  
Author(s):  
Christie P. Thomas ◽  
Jason R. Campbell ◽  
Patrick J. Wright ◽  
Russell F. Husted
Keyword(s):  
Apical Cell ◽  
P38 Map Kinase ◽  
Lung Epithelial Cells ◽  
Epithelial Cell Line ◽  
Phosphatidylinositol 3 Kinase ◽  
Transport Pathway ◽  
Early Effect ◽  
Sustained Effect ◽  
Phosphatidylinositol 3

H441 cells, a bronchiolar epithelial cell line, develop a cAMP-regulated benzamil-sensitive Na+ transport pathway on permeable supports (Itani OA, Auerbach SD, Husted RF, Volk KA, Ageloff S, Knepper MA, Stokes JB, Thomas CP. Am J Physiol Lung Cell Mol Physiol 282: L631–L641, 2002). To understand the molecular basis for the stimulation of Na+ transport, we delineated the role of specific intracellular pathways and examined the effect of cAMP on αβγ-epithelial Na+ channel (ENaC) and sgk1 expression. Na+ transport increases within 5 min of cAMP stimulation and is sustained for >24 h. The sustained effect of cAMP on Na+ transport is abolished by LY-294002, an inhibitor of phosphatidylinositol 3-kinase, by H89, an inhibitor of PKA, or by SB-202190, an inhibitor of p38 MAP kinase. The sustained effect of cAMP was associated with increases in α-ENaC mRNA and protein but without a detectable increase in βγ-ENaC and sgk1. The early effect of cAMP on Na+ transport is brefeldin sensitive and is mediated via PKA. These results are consistent with a model where the early effect of cAMP is to increase trafficking of Na+ channels to the apical cell surface whereas the sustained effect requires the synthesis of α-ENaC.

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