High Glucose Stimulates Synthesis of Fibronectin via a Novel Protein Kinase C, Rap1b, and B-Raf Signaling Pathway

Sun, Lin; Sahai, Atul; Chugh, Sumant S.; Pan, Xiaomin; Wallner, Elisabeth I.; Danesh, Farhad R.; Lomasney, Jon W.; Kanwar, Yashpal S.

doi:10.1074/jbc.m203957200

Cited by 46 publications

(44 citation statements)

References 80 publications

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“…A portion of the dissected cortices was processed for immunohistochemical studies. The remainder of the renal cortices was processed for tubular enrichment using a sieving method (6). The tubular enriched fraction was used to isolate mRNA for gene expression studies.…”

Section: Methodsmentioning

confidence: 99%

“…These changes are related to accentuation of cellular flux of glucose intermediaries (3), polyols (4), protein kinase C activity (5,6), expression of TGF-␤ (7), GTP-binding and cell cycle proteins (6,8), and generation of advanced glycation end products and reactive oxygen species (ROS) (9,10). The latter are regarded as central to the pathogenesis of DN with glomerulosclerosis and tubulointerstitial fibrosis in the kidney (11,12).…”

Section: Diabetic Nephropathy (Dn)mentioning

confidence: 99%

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myo-Inositol Oxygenase Overexpression Accentuates Generation of Reactive Oxygen Species and Exacerbates Cellular Injury following High Glucose Ambience

Sun

Dutta

Xie

et al. 2016

Journal of Biological Chemistry

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increased ROS generation, depleted reduced glutathione, reduced GSH/GSSG ratio, and enhanced adaptive changes in the profile of the antioxidant defense system. These changes were also accompanied by mitochondrial dysfunctions, DNA damage and induction of apoptosis, accentuated activity of profibrogenic cytokine, and expression of fibronectin, the latter two being the major hallmarks of DN. These perturbations were largely blocked by various ROS inhibitors (Mito Q, diphenyleneiodonium chloride, and N-acetylcysteine) and MIOX/NOX4 siRNA. In conclusion, this study highlights a novel mechanism where MIOX under HG ambience exacerbates renal injury during the progression of diabetic nephropathy following the generation of excessive ROS via an unexplored G-X pathway.

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Section: Methodsmentioning

confidence: 99%

Section: Diabetic Nephropathy (Dn)mentioning

confidence: 99%

myo-Inositol Oxygenase Overexpression Accentuates Generation of Reactive Oxygen Species and Exacerbates Cellular Injury following High Glucose Ambience

Sun

Dutta

Xie

et al. 2016

Journal of Biological Chemistry

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“…Although mitochondria were somewhat swollen, the morphology of the cristae was restored after transfection ( Figure 4). The protective effect of Rap1b seems to be specific because its mutant constructs (Rap1b/S17N and T61A) that negatively regulate its activity 16 failed to normalize Bax or Bcl-2 expression (Figure 2). Here, the question that needs to be addressed is the mechanism(s) by which Rap1b GTPase ameliorates high glucose-induced injury, and, in doing so, does it interact with Bcl-2 or Bax?…”

Section: Discussionmentioning

confidence: 99%

“…Tubular enriched fraction was prepared by separating glomeruli using a sieving method at 4°C. 16 The cytosolic proteins of tubular cells were extracted with 50 mM Tris-HCl buffer (pH 7.5) containing 50 mM NaCl, 10 mM EDTA, 0.5% NP-40, and a cocktail of protease inhibitors, 15,16,30 and protein concentration was adjusted to 1 mg/ml. Mitochondria were harvested from renal tubular fraction using a Mitochondrial Isolation kit (Pierce, Rockford, IL) following the vendor's instructions.…”

Section: In Vivo Studies With Kidney Tissues In Diabetic Micementioning

confidence: 99%

Rap1b GTPase Ameliorates Glucose-Induced Mitochondrial Dysfunction

Sun

Xie²,

Wada

et al. 2008

Journal of the American Society of Nephrology

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The role of tubular injury in diabetic nephropathy is relatively unknown, despite that apoptosis of tubular epithelial cells is commonly observed in human renal biopsies. The GTPase Ras-proximate-1 (Rap1b) is upregulated in the hyperglycemic state and is known to increase B-Raf, an antiapoptotic effector protein.In this study, the effects of high glucose on renal tubular apoptosis and the potential ability for Rap1b to ameliorate these effects were investigated. In the kidneys of diabetic mice, apoptotic tubular cells and dysmorphic mitochondria were observed, Bcl-2 expression was decreased, and Bax expression was increased. Total Rap1b expression was slightly increased, but its associated GTPase activity was significantly decreased. In vitro, high extracellular glucose led to decreased Bcl-2 expression, reduced Rap1b GTPase activity, and increased levels of both Bax and GTPase activating protein in a proximal tubular cell line (HK-2). These changes were accompanied by increased DNA fragmentation, decreased high molecular weight mitochondrial DNA, altered mitochondrial morphology and function, disrupted Bcl-2-Bax and Bcl-2-Rap1b interactions, and reduced cell survival. Overexpression of Rap1b partially prevents these abnormalities. Furthermore, the BH4 domain of Bcl-2 was found to be required for successful protein-protein interaction between Bcl-2 and Rap1b. In summary, these data suggest that Rap1b ameliorates glucose-induced mitochondrial dysfunction in renal tubular cells.

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“…diabetic nephropathy ͉ hyperglycemia ͉ osmoregulation D iabetic nephropathy is characterized by hyperplasia͞ hypertrophy of intrinsic renal cells and increased extracellular matrices (1). These changes are related to the increased cellular flux of glucose intermediaries (2), de novo synthesis of intra-and extracellular advanced glycation end products (3, 4), activation of protein kinase C (5, 6), increased expression of transforming growth factor-␤ (7), increased activity of GTP-binding and cell-cycle proteins (6,8), and generation of reactive oxygen species (9, 10), with consequential compromise in renal functions (11,12). Such complex interrelated cellular signaling events, also involving various forms of MAP͞ERK kinases and Smad proteins, have been defined mainly in glomerular cells (13,14); information relevant to the tubulointerstitial cells, although notably affected, is limited (15, 16).…”

mentioning

confidence: 99%

Modulation of renal-specific oxidoreductase/ myo -inositol oxygenase by high-glucose ambience

Nayak¹,

Xie²,

Akagi³

et al. 2005

Proc. Natl. Acad. Sci. U.S.A.

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Biological properties of renal-specific oxidoreductase (RSOR), characteristics of its promoter, and underlying mechanisms regulating its expression in diabetes were analyzed. RSOR expression, normally confined to the renal cortex, was markedly increased and extended into the outer medullary tubules in db͞db mice, a model of type 2 diabetes. Exposure of LLCPK cells to D-glucose resulted in a dose-dependent increase in RSOR expression and its enzymatic activity. The latter was related to one of the glycolytic enzymes, myo-inositol oxygenase. The increase in activity was in proportion to serum glucose concentration. The RSOR expression also increased in cells treated with various organic osmolytes, e.g., sorbitol, myoinositol, and glycerolphosphoryl-choline and H 2O2. Basal promoter activity was confined to ؊1,252 bp upstream of ATG, and it increased with the treatment of high glucose and osmolytes. EMSAs indicated an increased binding activity with osmotic-, carbohydrate-, and oxidant-response elements in cells treated with high glucose and was abolished by competitors. Supershifts, detected by anti-nuclear factor of activated T cells, and carbohydrate-response-element-binding protein established the binding specificity. Nuclear factor of activated T cells tonicityenhancer-binding protein and carbohydrate-response-elementbinding protein had increased nuclear expression in cells treated with high glucose. The activity of osmotic-response element exhibited a unique alternate binding pattern, as yet unreported in osmoregulatory genes. Data indicate that RSOR activity is modulated by diverse mechanisms, and it is endowed with dual properties to channel glucose intermediaries, characteristic of hepatic aldehyde reductases, and to maintain osmoregulation, a function of renal medullary genes, e.g., aldose reductase, in diabetes. diabetic nephropathy ͉ hyperglycemia ͉ osmoregulation D iabetic nephropathy is characterized by hyperplasia͞ hypertrophy of intrinsic renal cells and increased extracellular matrices (1). These changes are related to the increased cellular flux of glucose intermediaries (2), de novo synthesis of intra-and extracellular advanced glycation end products (3, 4), activation of protein kinase C (5, 6), increased expression of transforming growth factor-␤ (7), increased activity of GTP-binding and cell-cycle proteins (6,8), and generation of reactive oxygen species (9, 10), with consequential compromise in renal functions (11,12). Such complex interrelated cellular signaling events, also involving various forms of MAP͞ERK kinases and Smad proteins, have been defined mainly in glomerular cells (13,14); information relevant to the tubulointerstitial cells, although notably affected, is limited (15, 16). Conceivably, cellular changes in the tubulointerstitium parallel those in the glomerulus, with scarring and thickening of the basement membranes, and they correlate relatively better with the derangements in renal functional parameters (17, 18). Thus, much attention is warranted to the understanding of the...

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High Glucose Stimulates Synthesis of Fibronectin via a Novel Protein Kinase C, Rap1b, and B-Raf Signaling Pathway

Cited by 46 publications

References 80 publications

myo-Inositol Oxygenase Overexpression Accentuates Generation of Reactive Oxygen Species and Exacerbates Cellular Injury following High Glucose Ambience

myo-Inositol Oxygenase Overexpression Accentuates Generation of Reactive Oxygen Species and Exacerbates Cellular Injury following High Glucose Ambience

Rap1b GTPase Ameliorates Glucose-Induced Mitochondrial Dysfunction

Modulation of renal-specific oxidoreductase/ myo -inositol oxygenase by high-glucose ambience

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