The Experts below are selected from a list of 31914 Experts worldwide ranked by ideXlab platform
Goutam Ghosh Choudhury - One of the best experts on this subject based on the ideXlab platform.
-
tgfb acts through pdgfrb to activate mtorc1 via the akt pras40 axis and causes glomerular Mesangial Cell hypertrophy and matrix protein expression
Journal of Biological Chemistry, 2020Co-Authors: Soumya Maity, Nandini Ghoshchoudhury, Balakuntalam S Kasinath, Goutam Ghosh ChoudhuryAbstract:Interaction of TGFβ-induced canonical signaling with the noncanonical kinase cascades regulates glomerular hypertrophy and matrix protein deposition, which are early features of glomerulosclerosis. However, the specific target downstream of TGFβ receptor involved in the noncanonical signaling is unknown. Here, we show that TGFβ increased the catalytic loop phosphorylation of platelet-derived growth factor receptor beta (PDGFRβ), a receptor tyrosine kinase expressed abundantly in glomerular Mesangial Cells. TGFβ increased phosphorylation of the PI 3 kinase-interacting Tyr-751 residue of PDGFRβ, thus activating Akt. Inhibition of PDGFRβ using a pharmacological inhibitor and siRNAs blocked TGFβ-stimulated phosphorylation of PRAS40, an intrinsic inhibitory component of mTORC1, and prevented activation of mTORC1 in the absence of any effect on Smad 2/3 phosphorylation. Expression of constitutively active Myr-Akt reversed the siPDGFRβ-mediated inhibition of mTORC1 activity; however, co-expression of phospho-deficient mutant of PRAS40 inhibited the effect of Myr-Akt, suggesting a definitive role of PRAS40 phosphorylation in mTORC1 activation downstream of PDGFRβ in Mesangial Cells. Additionally, we demonstrate that PDGFRβ-initiated phosphorylation of PRAS40 is required for TGFβ-induced Mesangial Cell hypertrophy and, fibronectin and collagen I (α2) production. Increased activating phosphorylation of PDGFRβ is also associated with enhanced TGFβ expression and mTORC1 activation in the kidney cortex and glomeruli of diabetic mice and rat, respectively. Thus, pursuing the TGFβ noncanonical signaling, we identified how TGFβ receptor I achieves mTORC1 activation through PDGFRβ-mediated Akt/PRAS40 phosphorylation to spur Mesangial Cell hypertrophy and matrix protein accumulation. These findings provide support for targeting PDGFRβ in TGFβ-driven renal fibrosis.
-
deacetylation of s6 kinase promotes high glucose induced glomerular Mesangial Cell hypertrophy and matrix protein accumulation
Journal of Biological Chemistry, 2019Co-Authors: Soumya Maity, Nandini Ghoshchoudhury, Balakuntalam S Kasinath, Goutam Ghosh ChoudhuryAbstract:S6 kinase acts as a driver for renal hypertrophy and matrix accumulation, two key pathologic signatures of diabetic nephropathy. As a post-translational modification, S6 kinase undergoes acetylation at the C terminus. The role of this acetylation to regulate kidney glomerular Cell hypertrophy and matrix expansion is not known. In Mesangial Cells, high glucose decreased the acetylation and enhanced phosphorylation of S6 kinase and its substrates rps6 and eEF2 kinase that lead to dephosphorylation of eEF2. To determine the mechanism of S6 kinase deacetylation, we found that trichostatin A, a pan-histone deacetylase (HDAC) inhibitor, blocked all high glucose-induced effects. Furthermore, high glucose increased the expression and association of HDAC1 with S6 kinase. HDAC1 decreased the acetylation of S6 kinase and mimicked the effects of high glucose, resulting in Mesangial Cell hypertrophy and expression of fibronectin and collagen I (α2). In contrast, siRNA against HDAC1 inhibited these effects by high glucose. A C-terminal acetylation-mimetic mutant of S6 kinase suppressed high glucose-stimulated phosphorylation of S6 kinase, rps6 and eEF2 kinase, and inhibited the dephosphorylation of eEF2. Also, the acetylation mimetic attenuated the Mesangial Cell hypertrophy and fibronectin and collagen I (α2) expression. Conversely, an S6 kinase acetylation-deficient mutant induced all the above effects of high glucose. Finally, in the renal glomeruli of diabetic rats, the acetylation of S6 kinase was significantly reduced concomitant with increased HDAC1 and S6 kinase activity. In aggregate, our data uncovered a previously unrecognized role of S6 kinase deacetylation in high glucose-induced Mesangial Cell hypertrophy and matrix protein expression.
-
high glucose forces a positive feedback loop connecting akt kinase and foxo1 transcription factor to activate mtorc1 kinase for Mesangial Cell hypertrophy and matrix protein expression
Journal of Biological Chemistry, 2014Co-Authors: Nandini Ghoshchoudhury, Amit Bera, Balakuntalam S Kasinath, Meenalakshmi M Mariappan, Goutam Ghosh ChoudhuryAbstract:Abstract High glucose-induced Akt acts as a signaling hub for Mesangial Cell hypertrophy and matrix expansion, which are recognized as cardinal signatures for the development of diabetic nephropathy. How Mesangial Cells sustain the activated state of Akt is not clearly understood. Here we show Akt-dependent phosphorylation of the transcription factor FoxO1 by high glucose. Phosphorylation-deficient, constitutively active FoxO1 inhibited the high glucose-induced phosphorylation of Akt to suppress the phosphorylation/inactivation of PRAS40 and mTORC1 activity. In contrast, dominant negative FoxO1 increased the phosphorylation of Akt, resulting in increased mTORC1 activity similar to high glucose treatment. Notably, FoxO1 regulates high glucose-induced protein synthesis, hypertrophy, and expression of fibronectin and PAI-1. High glucose paves the way for complications of diabetic nephropathy through the production of reactive oxygen species (ROS). We considered whether the FoxO1 target antioxidant enzyme catalase contributes to sustained activation of Akt. High glucose-inactivated FoxO1 decreases the expression of catalase to increase the production of ROS. Moreover, we show that catalase blocks high glucose-stimulated Akt phosphorylation to attenuate the inactivation of FoxO1 and PRAS40, resulting in the inhibition of mTORC1 and Mesangial Cell hypertrophy and fibronectin and PAI-1 expression. Finally, using kidney cortices from type 1 diabetic OVE26 mice, we show that increased FoxO1 phosphorylation is associated with decreased catalase expression and increased fibronectin and PAI-1 expression. Together, our results provide the first evidence for the presence of a positive feedback loop for the sustained activation of Akt involving inactivated FoxO1 and a decrease in catalase expression, leading to increased ROS and Mesangial Cell hypertrophy and matrix protein expression.
-
a positive feedback loop involving erk5 and akt turns on Mesangial Cell proliferation in response to pdgf
American Journal of Physiology-cell Physiology, 2014Co-Authors: Amit Bera, Nandini Ghoshchoudhury, Xiaonan Li, Yves Gorin, Balakuntalam S Kasinath, Hanna E Abboud, Goutam Ghosh ChoudhuryAbstract:Platelet-derived growth factor BB and its receptor (PDGFRβ) play a pivotal role in the development of renal glomerular Mesangial Cells. Their roles in increased Mesangial Cell proliferation during mesangioproliferative glomerulonephritis have long been noted, but the operating logic of signaling mechanisms regulating these changes remains poorly understood. We examined the role of a recently identified MAPK, Erk5, in this process. PDGF increased the activating phosphorylation of Erk5 and tyrosine phosphorylation of proteins in a time-dependent manner. A pharmacologic inhibitor of Erk5, XMD8-92, abrogated PDGF-induced DNA synthesis and Mesangial Cell proliferation. Similarly, expression of dominant negative Erk5 or siRNAs against Erk5 blocked PDGF-stimulated DNA synthesis and proliferation. Inhibition of Erk5 attenuated expression of cyclin D1 mRNA and protein, resulting in suppression of CDK4-mediated phosphorylation of the tumor suppressor protein pRb. Expression of cyclin D1 or CDK4 prevented the dominant negative Erk5- or siErk5-mediated inhibition of DNA synthesis and Mesangial Cell proliferation induced by PDGF. We have previously shown that phosphatidylinositol 3-kinase (PI3-kinase) contributes to PDGF-induced proliferation of Mesangial Cells. Inhibition of PI3-kinase blocked PDGF-induced phosphorylation of Erk5. Since PI3-kinase acts through Akt, we determined the role of Erk5 on Akt phosphorylation. XMD8-92, dominant negative Erk5, and siErk5 inhibited phosphorylation of Akt by PDGF. Interestingly, we found inhibition of PDGF-induced Erk5 phosphorylation by a pharmacological inhibitor of Akt kinase and kinase dead Akt in Mesangial Cells. Thus our data unfold the presence of a positive feedback microcircuit between Erk5 and Akt downstream of PI3-kinase nodal point for PDGF-induced Mesangial Cell proliferation.
-
transforming growth factor β integrates smad 3 to mechanistic target of rapamycin complexes to arrest deptor abundance for glomerular Mesangial Cell hypertrophy
Journal of Biological Chemistry, 2013Co-Authors: Nandini Ghoshchoudhury, Amit Bera, Balakuntalam S Kasinath, Hanna E Abboud, Goutam Ghosh ChoudhuryAbstract:In many renal diseases, transforming growth factor β (TGFβ)-stimulated canonical Smad 3 and noncanonical mechanistic target of rapamycin (mTOR) promote increased protein synthesis and Mesangial Cell hypertrophy. The Cellular underpinnings involving these signaling molecules to regulate Mesangial Cell hypertrophy are not fully understood. Deptor has recently been identified as an mTOR interacting protein and functions as an endogenous inhibitor of the kinase activity for both TORC1 and TORC2. Prolonged incubation of Mesangial Cells with TGFβ reduced the levels of deptor concomitant with an increase in TORC1 and TORC2 activity. Sustained TGFβ activation was required to inhibit association of deptor with mTOR, whereas rapid activation had no effect. Using the mTOR inhibitor PP242, we found that TGFβ-induced both early and sustained activation of TORC1 and TORC2 was necessary for deptor suppression. PP242-induced reversal of deptor suppression by TGFβ was associated with a significant inhibition of TGFβ-stimulated protein synthesis and hypertrophy. Interestingly, expression of siRNA against Smad 3 or Smad 7, which blocks TGFβ receptor-specific Smad 3 signaling, prevented TGFβ-induced suppression of deptor abundance and TORC1/2 activities. Furthermore, overexpression of Smad 3 decreased deptor expression similar to TGFβ stimulation concomitant with increased TORC1 and TORC2 activities. Finally, knockdown of deptor reversed Smad 7-mediated inhibition of protein synthesis and Mesangial Cell hypertrophy induced by TGFβ. These data reveal the requirement of both early and late activation of mTOR for TGFβ-induced protein synthesis. Our results support that TGFβ-stimulated Smad 3 acts as a key node to instill a feedback loop between deptor down-regulation and TORC1/2 activation in driving Mesangial Cell hypertrophy.
Nandini Ghoshchoudhury - One of the best experts on this subject based on the ideXlab platform.
-
tgfb acts through pdgfrb to activate mtorc1 via the akt pras40 axis and causes glomerular Mesangial Cell hypertrophy and matrix protein expression
Journal of Biological Chemistry, 2020Co-Authors: Soumya Maity, Nandini Ghoshchoudhury, Balakuntalam S Kasinath, Goutam Ghosh ChoudhuryAbstract:Interaction of TGFβ-induced canonical signaling with the noncanonical kinase cascades regulates glomerular hypertrophy and matrix protein deposition, which are early features of glomerulosclerosis. However, the specific target downstream of TGFβ receptor involved in the noncanonical signaling is unknown. Here, we show that TGFβ increased the catalytic loop phosphorylation of platelet-derived growth factor receptor beta (PDGFRβ), a receptor tyrosine kinase expressed abundantly in glomerular Mesangial Cells. TGFβ increased phosphorylation of the PI 3 kinase-interacting Tyr-751 residue of PDGFRβ, thus activating Akt. Inhibition of PDGFRβ using a pharmacological inhibitor and siRNAs blocked TGFβ-stimulated phosphorylation of PRAS40, an intrinsic inhibitory component of mTORC1, and prevented activation of mTORC1 in the absence of any effect on Smad 2/3 phosphorylation. Expression of constitutively active Myr-Akt reversed the siPDGFRβ-mediated inhibition of mTORC1 activity; however, co-expression of phospho-deficient mutant of PRAS40 inhibited the effect of Myr-Akt, suggesting a definitive role of PRAS40 phosphorylation in mTORC1 activation downstream of PDGFRβ in Mesangial Cells. Additionally, we demonstrate that PDGFRβ-initiated phosphorylation of PRAS40 is required for TGFβ-induced Mesangial Cell hypertrophy and, fibronectin and collagen I (α2) production. Increased activating phosphorylation of PDGFRβ is also associated with enhanced TGFβ expression and mTORC1 activation in the kidney cortex and glomeruli of diabetic mice and rat, respectively. Thus, pursuing the TGFβ noncanonical signaling, we identified how TGFβ receptor I achieves mTORC1 activation through PDGFRβ-mediated Akt/PRAS40 phosphorylation to spur Mesangial Cell hypertrophy and matrix protein accumulation. These findings provide support for targeting PDGFRβ in TGFβ-driven renal fibrosis.
-
deacetylation of s6 kinase promotes high glucose induced glomerular Mesangial Cell hypertrophy and matrix protein accumulation
Journal of Biological Chemistry, 2019Co-Authors: Soumya Maity, Nandini Ghoshchoudhury, Balakuntalam S Kasinath, Goutam Ghosh ChoudhuryAbstract:S6 kinase acts as a driver for renal hypertrophy and matrix accumulation, two key pathologic signatures of diabetic nephropathy. As a post-translational modification, S6 kinase undergoes acetylation at the C terminus. The role of this acetylation to regulate kidney glomerular Cell hypertrophy and matrix expansion is not known. In Mesangial Cells, high glucose decreased the acetylation and enhanced phosphorylation of S6 kinase and its substrates rps6 and eEF2 kinase that lead to dephosphorylation of eEF2. To determine the mechanism of S6 kinase deacetylation, we found that trichostatin A, a pan-histone deacetylase (HDAC) inhibitor, blocked all high glucose-induced effects. Furthermore, high glucose increased the expression and association of HDAC1 with S6 kinase. HDAC1 decreased the acetylation of S6 kinase and mimicked the effects of high glucose, resulting in Mesangial Cell hypertrophy and expression of fibronectin and collagen I (α2). In contrast, siRNA against HDAC1 inhibited these effects by high glucose. A C-terminal acetylation-mimetic mutant of S6 kinase suppressed high glucose-stimulated phosphorylation of S6 kinase, rps6 and eEF2 kinase, and inhibited the dephosphorylation of eEF2. Also, the acetylation mimetic attenuated the Mesangial Cell hypertrophy and fibronectin and collagen I (α2) expression. Conversely, an S6 kinase acetylation-deficient mutant induced all the above effects of high glucose. Finally, in the renal glomeruli of diabetic rats, the acetylation of S6 kinase was significantly reduced concomitant with increased HDAC1 and S6 kinase activity. In aggregate, our data uncovered a previously unrecognized role of S6 kinase deacetylation in high glucose-induced Mesangial Cell hypertrophy and matrix protein expression.
-
high glucose forces a positive feedback loop connecting akt kinase and foxo1 transcription factor to activate mtorc1 kinase for Mesangial Cell hypertrophy and matrix protein expression
Journal of Biological Chemistry, 2014Co-Authors: Nandini Ghoshchoudhury, Amit Bera, Balakuntalam S Kasinath, Meenalakshmi M Mariappan, Goutam Ghosh ChoudhuryAbstract:Abstract High glucose-induced Akt acts as a signaling hub for Mesangial Cell hypertrophy and matrix expansion, which are recognized as cardinal signatures for the development of diabetic nephropathy. How Mesangial Cells sustain the activated state of Akt is not clearly understood. Here we show Akt-dependent phosphorylation of the transcription factor FoxO1 by high glucose. Phosphorylation-deficient, constitutively active FoxO1 inhibited the high glucose-induced phosphorylation of Akt to suppress the phosphorylation/inactivation of PRAS40 and mTORC1 activity. In contrast, dominant negative FoxO1 increased the phosphorylation of Akt, resulting in increased mTORC1 activity similar to high glucose treatment. Notably, FoxO1 regulates high glucose-induced protein synthesis, hypertrophy, and expression of fibronectin and PAI-1. High glucose paves the way for complications of diabetic nephropathy through the production of reactive oxygen species (ROS). We considered whether the FoxO1 target antioxidant enzyme catalase contributes to sustained activation of Akt. High glucose-inactivated FoxO1 decreases the expression of catalase to increase the production of ROS. Moreover, we show that catalase blocks high glucose-stimulated Akt phosphorylation to attenuate the inactivation of FoxO1 and PRAS40, resulting in the inhibition of mTORC1 and Mesangial Cell hypertrophy and fibronectin and PAI-1 expression. Finally, using kidney cortices from type 1 diabetic OVE26 mice, we show that increased FoxO1 phosphorylation is associated with decreased catalase expression and increased fibronectin and PAI-1 expression. Together, our results provide the first evidence for the presence of a positive feedback loop for the sustained activation of Akt involving inactivated FoxO1 and a decrease in catalase expression, leading to increased ROS and Mesangial Cell hypertrophy and matrix protein expression.
-
a positive feedback loop involving erk5 and akt turns on Mesangial Cell proliferation in response to pdgf
American Journal of Physiology-cell Physiology, 2014Co-Authors: Amit Bera, Nandini Ghoshchoudhury, Xiaonan Li, Yves Gorin, Balakuntalam S Kasinath, Hanna E Abboud, Goutam Ghosh ChoudhuryAbstract:Platelet-derived growth factor BB and its receptor (PDGFRβ) play a pivotal role in the development of renal glomerular Mesangial Cells. Their roles in increased Mesangial Cell proliferation during mesangioproliferative glomerulonephritis have long been noted, but the operating logic of signaling mechanisms regulating these changes remains poorly understood. We examined the role of a recently identified MAPK, Erk5, in this process. PDGF increased the activating phosphorylation of Erk5 and tyrosine phosphorylation of proteins in a time-dependent manner. A pharmacologic inhibitor of Erk5, XMD8-92, abrogated PDGF-induced DNA synthesis and Mesangial Cell proliferation. Similarly, expression of dominant negative Erk5 or siRNAs against Erk5 blocked PDGF-stimulated DNA synthesis and proliferation. Inhibition of Erk5 attenuated expression of cyclin D1 mRNA and protein, resulting in suppression of CDK4-mediated phosphorylation of the tumor suppressor protein pRb. Expression of cyclin D1 or CDK4 prevented the dominant negative Erk5- or siErk5-mediated inhibition of DNA synthesis and Mesangial Cell proliferation induced by PDGF. We have previously shown that phosphatidylinositol 3-kinase (PI3-kinase) contributes to PDGF-induced proliferation of Mesangial Cells. Inhibition of PI3-kinase blocked PDGF-induced phosphorylation of Erk5. Since PI3-kinase acts through Akt, we determined the role of Erk5 on Akt phosphorylation. XMD8-92, dominant negative Erk5, and siErk5 inhibited phosphorylation of Akt by PDGF. Interestingly, we found inhibition of PDGF-induced Erk5 phosphorylation by a pharmacological inhibitor of Akt kinase and kinase dead Akt in Mesangial Cells. Thus our data unfold the presence of a positive feedback microcircuit between Erk5 and Akt downstream of PI3-kinase nodal point for PDGF-induced Mesangial Cell proliferation.
-
transforming growth factor β integrates smad 3 to mechanistic target of rapamycin complexes to arrest deptor abundance for glomerular Mesangial Cell hypertrophy
Journal of Biological Chemistry, 2013Co-Authors: Nandini Ghoshchoudhury, Amit Bera, Balakuntalam S Kasinath, Hanna E Abboud, Goutam Ghosh ChoudhuryAbstract:In many renal diseases, transforming growth factor β (TGFβ)-stimulated canonical Smad 3 and noncanonical mechanistic target of rapamycin (mTOR) promote increased protein synthesis and Mesangial Cell hypertrophy. The Cellular underpinnings involving these signaling molecules to regulate Mesangial Cell hypertrophy are not fully understood. Deptor has recently been identified as an mTOR interacting protein and functions as an endogenous inhibitor of the kinase activity for both TORC1 and TORC2. Prolonged incubation of Mesangial Cells with TGFβ reduced the levels of deptor concomitant with an increase in TORC1 and TORC2 activity. Sustained TGFβ activation was required to inhibit association of deptor with mTOR, whereas rapid activation had no effect. Using the mTOR inhibitor PP242, we found that TGFβ-induced both early and sustained activation of TORC1 and TORC2 was necessary for deptor suppression. PP242-induced reversal of deptor suppression by TGFβ was associated with a significant inhibition of TGFβ-stimulated protein synthesis and hypertrophy. Interestingly, expression of siRNA against Smad 3 or Smad 7, which blocks TGFβ receptor-specific Smad 3 signaling, prevented TGFβ-induced suppression of deptor abundance and TORC1/2 activities. Furthermore, overexpression of Smad 3 decreased deptor expression similar to TGFβ stimulation concomitant with increased TORC1 and TORC2 activities. Finally, knockdown of deptor reversed Smad 7-mediated inhibition of protein synthesis and Mesangial Cell hypertrophy induced by TGFβ. These data reveal the requirement of both early and late activation of mTOR for TGFβ-induced protein synthesis. Our results support that TGFβ-stimulated Smad 3 acts as a key node to instill a feedback loop between deptor down-regulation and TORC1/2 activation in driving Mesangial Cell hypertrophy.
Richard J Johnson - One of the best experts on this subject based on the ideXlab platform.
-
extraglomerular origin of the Mesangial Cell after injury a new role of the juxtaglomerular apparatus
Journal of Clinical Investigation, 1997Co-Authors: Christian Hugo, Stuart J Shankland, William G Couser, Daniel F Bowenpope, Richard J JohnsonAbstract:: We investigated the origin of the glomerular Mesangial Cell, a smooth muscle-like Cell that provides structural support in the glomerulus. Injection of anti-Thy 1 antibody that binds the Thy 1 antigen on rat Mesangial Cells eliminated (> 95%) the Mesangial population at 20-28 h, while Thy 1-positive Cells in the juxtaglomerular apparatus (JGA) were sequestered from the circulation and survived. Single pulse labeling with [3H]thymidine at 36 h labeled Thy 1-positive Cells in the JGA and hilus. Serial biopsies demonstrated the progressive migration (5-15 micron/d) and proliferation of these Mesangial reserve Cells until the entire glomerulus was repopulated. The regenerating Mesangial population expressed contractile and migratory proteins preferentially at the leading edge of the migratory front. Single as well as multiple pulse labeling with [3H]thymidine confirmed that the entire Mesangial Cell repopulation originated from only a few Mesangial reserve Cells. These reserve Cells resided in the extraglomerular mesangium in the JGA and were not renin-secreting Cells, macrophages, smooth muscle Cells, or endothelial Cells. These studies document Mesangial Cell migration in the anti-Thy 1 model of Mesangial proliferative glomerulonephritis and provide evidence for a new role for the juxtaglomerular apparatus in the maintenance of the Mesangial Cell population.
-
Mesangial Cell proliferation mediated by pdgf and bfgf is determined by levels of the cyclin kinase inhibitor p27kip1
Kidney International, 1997Co-Authors: Stuart J Shankland, William G Couser, Jeffrey W Pippin, Mike Flanagan, Steve R Coats, Masaomi Nangaku, Katherine L Gordon, James M Roberts, Richard J JohnsonAbstract:Mesangial Cell proliferation mediated by PDGF and bFGF is determined by levels of the cyclin kinase inhibitor p27 Kip1 . Mesangial Cell proliferation in vitro is regulated by many cytokines. Platelet-derived growth factor (PDGF) and basic fibroblast growth factor (bFGF) are potent Mesangial Cell mitogens, whereas transforming growth factor- β 1 (TGF- β 1) reduces their effects. We examined how these cytokines regulate rat Mesangial Cell proliferation at the level of the Cell-cycle. Quiescent Mesangial Cells in vitro express the cyclin kinase inhibitor, p27 Kip1 (p27), and PDGF- and bFGF-induced Mesangial Cell proliferation is associated with a substantial decrease in p27 levels. Consequently there is a marked increase in expression (Western blot analysis, immunostaining) of cyclin A and CDK2. The decline in p27 levels was prevented by TGF- β 1 during inhibition of PDGF- and bFGF-induced Mesangial Cell proliferation. To determine the functional role of p27 during cytokine-mediated Mesangial Cell proliferation, the expression of p27 was reduced with specific p27 Kip1 antisense oligodeoxynucleotides. Reducing the levels of p27 resulted in an increased magnitude of Mesangial Cell proliferation (BrdU and 3 H-thymidine incorporation) induced by PDGF and bFGF compared to non-transfected Mesangial Cells and Mesangial Cells transfected with control mismatch oligodeoxynucleotides. Furthermore, the onset of maximal proliferation occurred earlier in Mesangial Cells transfected with antisense compared to control. The reduction in proliferation by TGF- β 1 were not altered by decreased p27 expression. Reducing p27 expression in the absence of mitogens was not associated with entry into the Cell-cycle. These results suggest cytokine mediated Mesangial Cell proliferation is associated with specific Cell-cycle proteins, and that the levels of p27 may be important in determining the Mesangial Cell's proliferative response to PDGF and bFGF in vitro .
-
Mesangial Cell apoptosis the major mechanism for resolution of glomerular hyperCellularity in experimental Mesangial proliferative nephritis
Journal of Clinical Investigation, 1994Co-Authors: Amanda J Baker, Richard J Johnson, A Mooney, Jeremy Hughes, Donna Lombardi, John SavillAbstract:Abstract Increases in Mesangial Cell number may herald glomerular scarring, but they are not irreversible. This study sought mechanisms by which surplus glomerular Mesangial Cells can be cleared. A small proportion of cultured Mesangial Cells exhibited typical morphological features of apoptosis (programmed Cell death), which was increased by growth factor deprivation or exposure to cycloheximide, stimuli known to increase apoptosis in other Cell types. Apoptosis was confirmed by typical internucleosomal chromatin cleavage. In vivo, clear morphological evidence of Mesangial apoptosis leading to phagocytosis by neighboring Mesangial Cells was obtained in self-limited Mesangial proliferation induced in rats by Thy1.1 antibody, apoptosis occurring approximately 10-fold more frequently than in the healthy rat glomerulus. Indeed, changes in glomerular Cell number in Thy1.1 nephritis strongly suggested that apoptosis is the major Cell clearance mechanism counterbalancing Cell division, thereby mediating resolution of glomerular hyperCellularity in experimental Mesangial proliferation.
-
heparin suppresses Mesangial Cell proliferation and matrix expansion in experimental mesangioproliferative glomerulonephritis
Kidney International, 1993Co-Authors: Jürgen Floege, Bessie A Young, William G Couser, Richard J JohnsonAbstract:Heparin suppresses Mesangial Cell proliferation and matrix expansion in experimental mesangioproliferative glomerulonephritis. Proliferation and extraCellular matrix (ECM) overproduction by glomerular Mesangial Cells characterizes many types of glomerulonephritis and often precedes the development of glomerulosclerosis. Heparin is a potent inhibitor of Mesangial Cell growth in vitro . We examined whether standard heparin can inhibit Mesangial Cell proliferation in vivo in the mesangioproliferative anti-Thy 1.1 nephritis. Untreated control rats were compared to rats infused with heparin either early (day -2 to 1) or late (day 2 to 5) after induction of anti-Thy 1.1 nephritis. The results show that heparin treatment significantly reduced Mesangial Cell proliferation regardless of when it was initiated. Heparin (either early or late treatment) also reduced Mesangial basic fibroblast growth factor (bFGF) expression and platelet-derived growth factor (PDGF) receptor up-regulation as reflected by immunostaining, whereas PDGF B-chain expression was reduced only by late heparin treatment. Furthermore, heparin treatment markedly inhibited the Mesangial matrix expansion for a variety of ECM proteins, including laminin, type I and IV collagen, fibronectin and entactin. Heparin did not affect the initial mesangiolysis, glomerular macrophage influx, deposition of anti-Thy 1.1 IgG or fibrinogen, or the glomerular platelet influx. These results suggest that heparin, via its antiproliferative rather than anticoagulant effect, can inhibit Mesangial Cell proliferation, overexpression of polypeptide growth factors, and ECM protein overproduction in vivo . The beneficial effect of heparin can be demonstrated even if treatment is initiated after the development of nephritis. By virtue of these properties, heparin may be an effective agent in the treatment of human mesangioproliferative disease and in the prevention of glomerulosclerosis.
-
factors involved in the regulation of Mesangial Cell proliferation in vitro and in vivo
Kidney International, 1993Co-Authors: Jürgen Floege, Bessie A Young, Richard J JohnsonAbstract:: One of the central features of many human glomerular diseases is the proliferation of the smooth muscle Cell-like Mesangial Cells. While a multitude of mitogens for Mesangial Cells has been proposed on the basis of in vitro experiments, the factors involved in the regulation of Mesangial Cell proliferation in vivo remain largely undefined. To investigate the regulation of Mesangial Cell proliferation in vivo we have studied the mesangioproliferative glomerulonephritis that is induced by injection of antibody directed against the Thy 1.1 antigen on the Mesangial Cell surface in rats. In this review, we discuss the role of three cytokines in the mesangioproliferative response, namely platelet-derived growth factor (PDGF), basic fibroblast growth factor (bFGF), and transforming growth factor-beta (TGF-beta). All three cytokines are present in various inflammatory Cells as well as in Mesangial Cells themselves, thereby allowing these factors to exert both paracrine and autocrine regulatory functions on Mesangial Cells. In vivo studies show that PDGF, bFGF and TGF-beta participate in either the Mesangial Cell proliferation or the Mesangial matrix expansion that follows Mesangial Cell injury with anti-Thy 1.1 antibody. Based on currently available data we propose that bFGF may participate in the initiation, PDGF in the maintenance, and TGF-beta in the resolution of Mesangial Cell proliferation in vivo. Further analysis of the mitogens operative in vivo may ultimately result in the design of new therapeutic strategies to treat progressive glomerular mesangioproliferative diseases.
Balakuntalam S Kasinath - One of the best experts on this subject based on the ideXlab platform.
-
tgfb acts through pdgfrb to activate mtorc1 via the akt pras40 axis and causes glomerular Mesangial Cell hypertrophy and matrix protein expression
Journal of Biological Chemistry, 2020Co-Authors: Soumya Maity, Nandini Ghoshchoudhury, Balakuntalam S Kasinath, Goutam Ghosh ChoudhuryAbstract:Interaction of TGFβ-induced canonical signaling with the noncanonical kinase cascades regulates glomerular hypertrophy and matrix protein deposition, which are early features of glomerulosclerosis. However, the specific target downstream of TGFβ receptor involved in the noncanonical signaling is unknown. Here, we show that TGFβ increased the catalytic loop phosphorylation of platelet-derived growth factor receptor beta (PDGFRβ), a receptor tyrosine kinase expressed abundantly in glomerular Mesangial Cells. TGFβ increased phosphorylation of the PI 3 kinase-interacting Tyr-751 residue of PDGFRβ, thus activating Akt. Inhibition of PDGFRβ using a pharmacological inhibitor and siRNAs blocked TGFβ-stimulated phosphorylation of PRAS40, an intrinsic inhibitory component of mTORC1, and prevented activation of mTORC1 in the absence of any effect on Smad 2/3 phosphorylation. Expression of constitutively active Myr-Akt reversed the siPDGFRβ-mediated inhibition of mTORC1 activity; however, co-expression of phospho-deficient mutant of PRAS40 inhibited the effect of Myr-Akt, suggesting a definitive role of PRAS40 phosphorylation in mTORC1 activation downstream of PDGFRβ in Mesangial Cells. Additionally, we demonstrate that PDGFRβ-initiated phosphorylation of PRAS40 is required for TGFβ-induced Mesangial Cell hypertrophy and, fibronectin and collagen I (α2) production. Increased activating phosphorylation of PDGFRβ is also associated with enhanced TGFβ expression and mTORC1 activation in the kidney cortex and glomeruli of diabetic mice and rat, respectively. Thus, pursuing the TGFβ noncanonical signaling, we identified how TGFβ receptor I achieves mTORC1 activation through PDGFRβ-mediated Akt/PRAS40 phosphorylation to spur Mesangial Cell hypertrophy and matrix protein accumulation. These findings provide support for targeting PDGFRβ in TGFβ-driven renal fibrosis.
-
deacetylation of s6 kinase promotes high glucose induced glomerular Mesangial Cell hypertrophy and matrix protein accumulation
Journal of Biological Chemistry, 2019Co-Authors: Soumya Maity, Nandini Ghoshchoudhury, Balakuntalam S Kasinath, Goutam Ghosh ChoudhuryAbstract:S6 kinase acts as a driver for renal hypertrophy and matrix accumulation, two key pathologic signatures of diabetic nephropathy. As a post-translational modification, S6 kinase undergoes acetylation at the C terminus. The role of this acetylation to regulate kidney glomerular Cell hypertrophy and matrix expansion is not known. In Mesangial Cells, high glucose decreased the acetylation and enhanced phosphorylation of S6 kinase and its substrates rps6 and eEF2 kinase that lead to dephosphorylation of eEF2. To determine the mechanism of S6 kinase deacetylation, we found that trichostatin A, a pan-histone deacetylase (HDAC) inhibitor, blocked all high glucose-induced effects. Furthermore, high glucose increased the expression and association of HDAC1 with S6 kinase. HDAC1 decreased the acetylation of S6 kinase and mimicked the effects of high glucose, resulting in Mesangial Cell hypertrophy and expression of fibronectin and collagen I (α2). In contrast, siRNA against HDAC1 inhibited these effects by high glucose. A C-terminal acetylation-mimetic mutant of S6 kinase suppressed high glucose-stimulated phosphorylation of S6 kinase, rps6 and eEF2 kinase, and inhibited the dephosphorylation of eEF2. Also, the acetylation mimetic attenuated the Mesangial Cell hypertrophy and fibronectin and collagen I (α2) expression. Conversely, an S6 kinase acetylation-deficient mutant induced all the above effects of high glucose. Finally, in the renal glomeruli of diabetic rats, the acetylation of S6 kinase was significantly reduced concomitant with increased HDAC1 and S6 kinase activity. In aggregate, our data uncovered a previously unrecognized role of S6 kinase deacetylation in high glucose-induced Mesangial Cell hypertrophy and matrix protein expression.
-
high glucose forces a positive feedback loop connecting akt kinase and foxo1 transcription factor to activate mtorc1 kinase for Mesangial Cell hypertrophy and matrix protein expression
Journal of Biological Chemistry, 2014Co-Authors: Nandini Ghoshchoudhury, Amit Bera, Balakuntalam S Kasinath, Meenalakshmi M Mariappan, Goutam Ghosh ChoudhuryAbstract:Abstract High glucose-induced Akt acts as a signaling hub for Mesangial Cell hypertrophy and matrix expansion, which are recognized as cardinal signatures for the development of diabetic nephropathy. How Mesangial Cells sustain the activated state of Akt is not clearly understood. Here we show Akt-dependent phosphorylation of the transcription factor FoxO1 by high glucose. Phosphorylation-deficient, constitutively active FoxO1 inhibited the high glucose-induced phosphorylation of Akt to suppress the phosphorylation/inactivation of PRAS40 and mTORC1 activity. In contrast, dominant negative FoxO1 increased the phosphorylation of Akt, resulting in increased mTORC1 activity similar to high glucose treatment. Notably, FoxO1 regulates high glucose-induced protein synthesis, hypertrophy, and expression of fibronectin and PAI-1. High glucose paves the way for complications of diabetic nephropathy through the production of reactive oxygen species (ROS). We considered whether the FoxO1 target antioxidant enzyme catalase contributes to sustained activation of Akt. High glucose-inactivated FoxO1 decreases the expression of catalase to increase the production of ROS. Moreover, we show that catalase blocks high glucose-stimulated Akt phosphorylation to attenuate the inactivation of FoxO1 and PRAS40, resulting in the inhibition of mTORC1 and Mesangial Cell hypertrophy and fibronectin and PAI-1 expression. Finally, using kidney cortices from type 1 diabetic OVE26 mice, we show that increased FoxO1 phosphorylation is associated with decreased catalase expression and increased fibronectin and PAI-1 expression. Together, our results provide the first evidence for the presence of a positive feedback loop for the sustained activation of Akt involving inactivated FoxO1 and a decrease in catalase expression, leading to increased ROS and Mesangial Cell hypertrophy and matrix protein expression.
-
a positive feedback loop involving erk5 and akt turns on Mesangial Cell proliferation in response to pdgf
American Journal of Physiology-cell Physiology, 2014Co-Authors: Amit Bera, Nandini Ghoshchoudhury, Xiaonan Li, Yves Gorin, Balakuntalam S Kasinath, Hanna E Abboud, Goutam Ghosh ChoudhuryAbstract:Platelet-derived growth factor BB and its receptor (PDGFRβ) play a pivotal role in the development of renal glomerular Mesangial Cells. Their roles in increased Mesangial Cell proliferation during mesangioproliferative glomerulonephritis have long been noted, but the operating logic of signaling mechanisms regulating these changes remains poorly understood. We examined the role of a recently identified MAPK, Erk5, in this process. PDGF increased the activating phosphorylation of Erk5 and tyrosine phosphorylation of proteins in a time-dependent manner. A pharmacologic inhibitor of Erk5, XMD8-92, abrogated PDGF-induced DNA synthesis and Mesangial Cell proliferation. Similarly, expression of dominant negative Erk5 or siRNAs against Erk5 blocked PDGF-stimulated DNA synthesis and proliferation. Inhibition of Erk5 attenuated expression of cyclin D1 mRNA and protein, resulting in suppression of CDK4-mediated phosphorylation of the tumor suppressor protein pRb. Expression of cyclin D1 or CDK4 prevented the dominant negative Erk5- or siErk5-mediated inhibition of DNA synthesis and Mesangial Cell proliferation induced by PDGF. We have previously shown that phosphatidylinositol 3-kinase (PI3-kinase) contributes to PDGF-induced proliferation of Mesangial Cells. Inhibition of PI3-kinase blocked PDGF-induced phosphorylation of Erk5. Since PI3-kinase acts through Akt, we determined the role of Erk5 on Akt phosphorylation. XMD8-92, dominant negative Erk5, and siErk5 inhibited phosphorylation of Akt by PDGF. Interestingly, we found inhibition of PDGF-induced Erk5 phosphorylation by a pharmacological inhibitor of Akt kinase and kinase dead Akt in Mesangial Cells. Thus our data unfold the presence of a positive feedback microcircuit between Erk5 and Akt downstream of PI3-kinase nodal point for PDGF-induced Mesangial Cell proliferation.
-
transforming growth factor β integrates smad 3 to mechanistic target of rapamycin complexes to arrest deptor abundance for glomerular Mesangial Cell hypertrophy
Journal of Biological Chemistry, 2013Co-Authors: Nandini Ghoshchoudhury, Amit Bera, Balakuntalam S Kasinath, Hanna E Abboud, Goutam Ghosh ChoudhuryAbstract:In many renal diseases, transforming growth factor β (TGFβ)-stimulated canonical Smad 3 and noncanonical mechanistic target of rapamycin (mTOR) promote increased protein synthesis and Mesangial Cell hypertrophy. The Cellular underpinnings involving these signaling molecules to regulate Mesangial Cell hypertrophy are not fully understood. Deptor has recently been identified as an mTOR interacting protein and functions as an endogenous inhibitor of the kinase activity for both TORC1 and TORC2. Prolonged incubation of Mesangial Cells with TGFβ reduced the levels of deptor concomitant with an increase in TORC1 and TORC2 activity. Sustained TGFβ activation was required to inhibit association of deptor with mTOR, whereas rapid activation had no effect. Using the mTOR inhibitor PP242, we found that TGFβ-induced both early and sustained activation of TORC1 and TORC2 was necessary for deptor suppression. PP242-induced reversal of deptor suppression by TGFβ was associated with a significant inhibition of TGFβ-stimulated protein synthesis and hypertrophy. Interestingly, expression of siRNA against Smad 3 or Smad 7, which blocks TGFβ receptor-specific Smad 3 signaling, prevented TGFβ-induced suppression of deptor abundance and TORC1/2 activities. Furthermore, overexpression of Smad 3 decreased deptor expression similar to TGFβ stimulation concomitant with increased TORC1 and TORC2 activities. Finally, knockdown of deptor reversed Smad 7-mediated inhibition of protein synthesis and Mesangial Cell hypertrophy induced by TGFβ. These data reveal the requirement of both early and late activation of mTOR for TGFβ-induced protein synthesis. Our results support that TGFβ-stimulated Smad 3 acts as a key node to instill a feedback loop between deptor down-regulation and TORC1/2 activation in driving Mesangial Cell hypertrophy.
Amit Bera - One of the best experts on this subject based on the ideXlab platform.
-
high glucose forces a positive feedback loop connecting akt kinase and foxo1 transcription factor to activate mtorc1 kinase for Mesangial Cell hypertrophy and matrix protein expression
Journal of Biological Chemistry, 2014Co-Authors: Nandini Ghoshchoudhury, Amit Bera, Balakuntalam S Kasinath, Meenalakshmi M Mariappan, Goutam Ghosh ChoudhuryAbstract:Abstract High glucose-induced Akt acts as a signaling hub for Mesangial Cell hypertrophy and matrix expansion, which are recognized as cardinal signatures for the development of diabetic nephropathy. How Mesangial Cells sustain the activated state of Akt is not clearly understood. Here we show Akt-dependent phosphorylation of the transcription factor FoxO1 by high glucose. Phosphorylation-deficient, constitutively active FoxO1 inhibited the high glucose-induced phosphorylation of Akt to suppress the phosphorylation/inactivation of PRAS40 and mTORC1 activity. In contrast, dominant negative FoxO1 increased the phosphorylation of Akt, resulting in increased mTORC1 activity similar to high glucose treatment. Notably, FoxO1 regulates high glucose-induced protein synthesis, hypertrophy, and expression of fibronectin and PAI-1. High glucose paves the way for complications of diabetic nephropathy through the production of reactive oxygen species (ROS). We considered whether the FoxO1 target antioxidant enzyme catalase contributes to sustained activation of Akt. High glucose-inactivated FoxO1 decreases the expression of catalase to increase the production of ROS. Moreover, we show that catalase blocks high glucose-stimulated Akt phosphorylation to attenuate the inactivation of FoxO1 and PRAS40, resulting in the inhibition of mTORC1 and Mesangial Cell hypertrophy and fibronectin and PAI-1 expression. Finally, using kidney cortices from type 1 diabetic OVE26 mice, we show that increased FoxO1 phosphorylation is associated with decreased catalase expression and increased fibronectin and PAI-1 expression. Together, our results provide the first evidence for the presence of a positive feedback loop for the sustained activation of Akt involving inactivated FoxO1 and a decrease in catalase expression, leading to increased ROS and Mesangial Cell hypertrophy and matrix protein expression.
-
a positive feedback loop involving erk5 and akt turns on Mesangial Cell proliferation in response to pdgf
American Journal of Physiology-cell Physiology, 2014Co-Authors: Amit Bera, Nandini Ghoshchoudhury, Xiaonan Li, Yves Gorin, Balakuntalam S Kasinath, Hanna E Abboud, Goutam Ghosh ChoudhuryAbstract:Platelet-derived growth factor BB and its receptor (PDGFRβ) play a pivotal role in the development of renal glomerular Mesangial Cells. Their roles in increased Mesangial Cell proliferation during mesangioproliferative glomerulonephritis have long been noted, but the operating logic of signaling mechanisms regulating these changes remains poorly understood. We examined the role of a recently identified MAPK, Erk5, in this process. PDGF increased the activating phosphorylation of Erk5 and tyrosine phosphorylation of proteins in a time-dependent manner. A pharmacologic inhibitor of Erk5, XMD8-92, abrogated PDGF-induced DNA synthesis and Mesangial Cell proliferation. Similarly, expression of dominant negative Erk5 or siRNAs against Erk5 blocked PDGF-stimulated DNA synthesis and proliferation. Inhibition of Erk5 attenuated expression of cyclin D1 mRNA and protein, resulting in suppression of CDK4-mediated phosphorylation of the tumor suppressor protein pRb. Expression of cyclin D1 or CDK4 prevented the dominant negative Erk5- or siErk5-mediated inhibition of DNA synthesis and Mesangial Cell proliferation induced by PDGF. We have previously shown that phosphatidylinositol 3-kinase (PI3-kinase) contributes to PDGF-induced proliferation of Mesangial Cells. Inhibition of PI3-kinase blocked PDGF-induced phosphorylation of Erk5. Since PI3-kinase acts through Akt, we determined the role of Erk5 on Akt phosphorylation. XMD8-92, dominant negative Erk5, and siErk5 inhibited phosphorylation of Akt by PDGF. Interestingly, we found inhibition of PDGF-induced Erk5 phosphorylation by a pharmacological inhibitor of Akt kinase and kinase dead Akt in Mesangial Cells. Thus our data unfold the presence of a positive feedback microcircuit between Erk5 and Akt downstream of PI3-kinase nodal point for PDGF-induced Mesangial Cell proliferation.
-
transforming growth factor β integrates smad 3 to mechanistic target of rapamycin complexes to arrest deptor abundance for glomerular Mesangial Cell hypertrophy
Journal of Biological Chemistry, 2013Co-Authors: Nandini Ghoshchoudhury, Amit Bera, Balakuntalam S Kasinath, Hanna E Abboud, Goutam Ghosh ChoudhuryAbstract:In many renal diseases, transforming growth factor β (TGFβ)-stimulated canonical Smad 3 and noncanonical mechanistic target of rapamycin (mTOR) promote increased protein synthesis and Mesangial Cell hypertrophy. The Cellular underpinnings involving these signaling molecules to regulate Mesangial Cell hypertrophy are not fully understood. Deptor has recently been identified as an mTOR interacting protein and functions as an endogenous inhibitor of the kinase activity for both TORC1 and TORC2. Prolonged incubation of Mesangial Cells with TGFβ reduced the levels of deptor concomitant with an increase in TORC1 and TORC2 activity. Sustained TGFβ activation was required to inhibit association of deptor with mTOR, whereas rapid activation had no effect. Using the mTOR inhibitor PP242, we found that TGFβ-induced both early and sustained activation of TORC1 and TORC2 was necessary for deptor suppression. PP242-induced reversal of deptor suppression by TGFβ was associated with a significant inhibition of TGFβ-stimulated protein synthesis and hypertrophy. Interestingly, expression of siRNA against Smad 3 or Smad 7, which blocks TGFβ receptor-specific Smad 3 signaling, prevented TGFβ-induced suppression of deptor abundance and TORC1/2 activities. Furthermore, overexpression of Smad 3 decreased deptor expression similar to TGFβ stimulation concomitant with increased TORC1 and TORC2 activities. Finally, knockdown of deptor reversed Smad 7-mediated inhibition of protein synthesis and Mesangial Cell hypertrophy induced by TGFβ. These data reveal the requirement of both early and late activation of mTOR for TGFβ-induced protein synthesis. Our results support that TGFβ-stimulated Smad 3 acts as a key node to instill a feedback loop between deptor down-regulation and TORC1/2 activation in driving Mesangial Cell hypertrophy.