Glycobiology Advance Access originally published online on December 29, 2004
Glycobiology 2005 15(6):585-591; doi:10.1093/glycob/cwi039
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Glycobiology vol. 15 no. 6 © Oxford University Press 2004; all rights reserved.
Involvement of gangliosides in glucosamine-induced proliferation decrease of retinal pericytes
Diabetic Microangiopathy Research Unit, Merck Santé-INSERM UMR 585, INSA-Lyon, Louis Pasteur Bldg, 69621 Villeurbanne Cedex, France
1 To whom correspondence should be addressed; e-mail: samer.elbawab{at}merck.fr
Received on July 15, 2004; revised on December 20, 2004; accepted on December 23, 2004
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Abstract |
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The hexosamine pathway (HP) is a biochemical hypothesis recently proposed explaining cellular alterations occurring during diabetic microvascular complications. Diabetic retinopathy is a common microvascular complication of diabetes, and it is known that cell proliferation is severely affected during the development of the disease. Particularly, early stages are characterized by death of the retinal microvascular cells, pericytes. Gangliosides have often been described to regulate cell growth; however, very few studies focused on the potential role of gangliosides in diabetic microvascular alterations. The aim of this article was to investigate the effect of the HP activation on pericyte proliferation and determine the potential implication of gangliosides in this process. Results indicate first that HP activation, mimicked by glucosamine treatment, decreased pericyte proliferation. Second, glucosamine treatment induced a modification of gangliosides pattern, particularly GM1 and GD3 were significantly increased. Next, results showed that exogenous addition of a-series gangliosides (GM3, GM2, GM1, GD1a) and b-series ganglioside (GD3) caused a decrease of pericyte proliferation, whereas nonsialylated precursors glucosylceramide and lactosylceramide were without effect. Furthermore, when ganglioside biosynthesis was blocked using PPMP, a glucosylceramide synthase inhibitor, the effects of glucosamine on pericyte proliferation were partially reversed. Our results suggest that in retinal pericytes, gangliosides and particularly GM1 and GD3 that are increased in response to glucosamine, are involved in the antiproliferative effect of glucosamine. These observations also underlie the potential involvement of gangliosides in a pathological context, such as diabetic microvascular complications.
Key words: diabetic retinopathy / gangliosides / hexosamine pathway / pericytes
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Introduction |
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Gangliosides are glycosphingolipids characterized by the presence of sialic acid in their oligosaccharidic portion. After the initial glycosylation step of ceramide catalyzed by glucosylceramide synthase, successive sialylations and glycosylations lead to a wide diversity of gangliosides. They are concentrated in plasma membranes with a cell-specific pattern. They are found in most tissues of the body and are particularly abundant in brain and nervous tissues (van Echten and Sandhoff, 1993
). Gangliosides are known to exert a bifunctional role (Hakomori, 1990). On one hand, they play major roles in cell–cell and cell–matrix recognition via interactions with adhesion receptors such as integrins, matrix proteins (collagen and fibronectin), or other glycosphingolipids, giving them important role in morphogenesis and oncogenesis. In addition, a number of gangliosides may act as receptors of bacteria, viruses, or toxins. On the other hand, gangliosides are known to regulate transmembrane signaling by modulating functional membrane proteins. Thus, they have been described to regulate cell proliferation through modulation of growth factor receptor–associated kinases such as epidermal growth factor and platelet-derived growth factor receptors (Bremer et al., 1986; Mirkin et al., 2002; Sachinidis et al., 1996; Van Brocklyn et al., 1993). The importance of gangliosides in regulating cell proliferation is also supported by studies implicating them in cell cycle arrest processes via cyclin-dependent kinase inhibitors (Nakatsuji and Miller, 2001) or in apoptosis through mitochondrial events (Kristal and Brown, 1999; Rippo et al., 2000).
It is well documented that regulation of cell proliferation is severely affected in retinopathy, a main microvascular complication of diabetes. Death of retinal pericytes, microvascular contractile cells, is indeed one of the earliest retinal changes, induced by hyperglycemia. Pericyte loss and subsequent modification of endothelial cell proliferation and function, combined with basement membrane thickening, trigger structural and functional alterations of capillaries. These chronic alterations establish edema, microaneurisms, and hemorrage that at ultimate stages can lead to blindness (Forrester et al., 1997).
Although the pathogenic basis of diabetic microangiopathy is not fully understood at cellular and molecular levels, it is clear that regulations of cell proliferation play an important role. The hexosamine pathway (HP), a novel glucose-sensing pathway, has been implicated in hyperglycemia-induced diabetic vascular alterations (Marshall et al., 1991). After entering cells, glucose is rapidly phosphorylated and converted to fructose-6-phosphate (F-6-P), which is mainly catabolized through the glycolytic pathway. Nevertheless, under hyperglycemic conditions, a greater part of F-6-P can be converted to glucosamine-6-phosphate by glutamine:F-6-P amidotransferase (GFAT), the first and rate-limiting enzyme of the hexosamine biosynthetic pathway. Glucosamine-6-phosphate then undergoes rapid conversion to various hexosamine products, including UDP-N-acetylglucosamine (UDP-GlcNAc). Thus the HP can be activated under the hyperglycemic conditions of a diabetic state by increased availability of substrate (F-6-P) and/or GFAT activation.
The HP exerts its effects via two described mechanisms. First, hexosamine product biosynthesis provides glycosidic precursors for the synthesis of glycoproteins, glycolipids, and proteoglycans. These intermediates can especially be used in the endoplasmic reticulum to form complex glycoproteins, secreted or inserted into the membrane where they can modulate transmembrane signaling or extracellular interactions. Additionally, UDP-GlcNAc can be used as precursor for CMP–sialic acid, a substrate of ganglioside biosynthesis, raising the possibility of a connection between HP and the ganglioside pathway. Second, cytosolic or nuclear proteins can be covalently modified by the addition of a single monosaccharide GlcNAc, a product of the HP. This O-linked glycosylation occurs on key intracellular proteins playing roles in controlling gene expression, cell growth and division, enzyme activity, or structural integrity of the cytoskeleton (Marshall, 2002). Because the potential targets of these O-glycosylation modifications are numerous, the HP may be involved in many pathological mechanisms.
A growing number of studies suggest a role of HP in glucose-induced insulin resistance (Hebert, Jr. et al., 1996; Kaneto et al., 2001; Vosseller et al., 2002) and in diabetic nephropathy, particularly in renal mesangial cell alterations (Kolm-Litty et al., 1998; Schleicher and Weigert, 2000; Singh et al., 2001). However very few studies (if any) have examined the involvement of HP in the development of diabetic retinopathy. Moreover, although gangliosides play a major role in cell proliferation, their potential involvement in diabetic microvascular complications and particularly in retinal pericyte growth perturbations has been poorly studied.
The aim of the present study was to investigate the effect of the HP activation on pericyte proliferation, ganglioside profile, and potential link between the two events. Results indicated that glucosamine modifies pericyte ganglioside pattern concomitantly to a decrease of cell proliferation. Furthermore, addition of exogenous gangliosides exerted antiproliferative effects on pericytes, suggesting that gangliosides are involved in mediating the adverse glucosamine effects on pericyte proliferation.
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Results |
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Glucosamine treatment inhibits pericyte proliferation
To evaluate the effect of the HP on pericyte growth, cells were treated with glucosamine, which bypasses the rate-limiting enzyme GFAT and mimics an exacerbation of the HP. Cells were exposed to 5 mM glucosamine for 1–7 days, and proliferation was estimated by cell counting and total proteins measurement. As shown in Figure 1, time-course experiments revealed that glucosamine potently decreased pericyte proliferation starting at 1–2 days of treatment. Cell counting revealed that glucosamine reduced pericyte number by 32% and 40% after 2 and 7 days of treatment, respectively. A decrease of total proteins was also observed in glucosamine-treated cells and correlated to cell number (Figure 1C). To investigate the effects of glucosamine on cell proliferation, apoptosis was measured in cells treated for 7 days with 5 mM glucosamine. Measurement of caspase 3 activation and determination of DNA fragmentation using an oligonucleosomes determination kit showed that glucosamine did not induce apoptosis of bovine retinal pericytes (BRPs), at least under our culture conditions (data not shown). These results suggest that the growth inhibition observed in response to glucosamine might involve cell cycle events.
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Glucosamine modulates ganglioside profile
Ganglioside pattern of BRPs was analyzed in control and cells treated with 5 mM glucosamine. Under control conditions, the main gangliosides were GM3 (60% of all gangliosides detected), GD3 (28%), and GM1 (12%) (Figure 2A). As shown in Figure 2, important modifications of ganglioside profile were observed in response to glucosamine (Figure 2B–C). Thus, GM1 and GD3 masses were increased by 27% and 19%, and by 85% and 105%, after 2 and 7 days of treatment, respectively. Conversely, GM3 mass was decreased by 21% and 32% after 2 and 7 days of treatment, respectively. Similar results were obtained by autoradiography analysis after galactose labeling (data not shown). These results suggest a possible connection between the HP and the ganglioside biosynthesis pathway. Because the glucosamine effects were maximal at 7 days, subsequent experiments were performed at this time of treatment.
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Glucosamine increases GM3 synthase activity
To investigate the mechanism responsible for the observed increase of GM1 and GD3 masses, GM3 synthase activity, a rate-limiting enzyme for the synthesis of gangliosides was measured in control and treated cells. Results presented in Figure 3 show that glucosamine treatment increased GM3 synthase activity by 
160%. Because GM3 is a precursor of complex gangliosides, its decrease despite the augmentation of GM3 synthase activity suggests that GM3 was metabolized to GM1 and GD3 that are both increased in response to glucosamine.
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Treatment with exogenous gangliosides inhibits pericyte proliferation
Because GM1 and GD3 were increased concomitantly to a decrease of cell proliferation in response to glucosamine, we further explored the hypothesis that gangliosides are involved in mediating glucosamine effects. Thus we investigated whether the addition of exogenous gangliosides affects pericyte proliferation. Cells were treated during one passage (7 days) with 10, 50, or 100 µM gangliosides and, as a control, with the nonsialylated precursors glucosylceramide and lactosylceramide. Results presented in Figure 4 show that GM1 and GD3 inhibited pericyte proliferation in a dose-dependent manner, whereas glucosylceramide and lactosylceramide used as controls showed no effects. Inhibition of cell proliferation reached 25% at ganglioside concentration of 100 µM. The effect of a-series gangliosides that were not increased in response to glucosamine was also tested. Results indicated that GM3, GM2, and GD1a also inhibited BRP proliferation (data not shown), suggesting that the presence of sialic acid is required in the active structure leading to inhibition of BRP proliferation. It should be indicated, however, that treatment with exogenous gangliosides resulted in rather modest effects as compared to the effects of glucosamine. These data might be explained by the fact that only a small proportion of added gangliosides are inserted into cell membranes. Additionally, exogenous gangliosides treatment may result in the generation of cell membrane pool functionally different from the gangliosides pool formed endogenously in response to glucosamine treatment.
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PPMP protects against the inhibition of proliferation caused by glucosamine
Next, a complementary approach was used to further support the involvement of gangliosides in the antiproliferative effects of glucosamine on pericytes. DL-threo-1-phenyl-2-palmitoylamino-3-morpholino-1-propanol (PPMP), an inhibitor of glucosylceramide synthase, was used to block the increase of gangliosides caused by glucosamine. As shown in Figure 5, treatment of BRPs with glucosamine in the presence of increasing concentrations of PPMP partially protected cells against proliferation decrease, in a dose-dependent manner.
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Altogether, these results support the hypothesis that GM1 and GD3 increase is involved, at least in part, in the proliferation decrease of pericytes treated with glucosamine.
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Discussion |
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A growing number of studies indicate that the HP may be causally involved in the development of diabetic microvascular complications, particularly nephropathy. Many of the pathological features of diabetic nephropathy are also common to diabetic retinopathy. Further, as it is known that retina expresses active GFAT and that hexosamine content is increased in retinal tissues in human and rats with diabetes (Heath et al., 1967
; Mazlen et al., 1970), this raises the hypothesis that the HP could possibly be implicated in diabetic retinopathy development and pericyte loss. On the other hand, gangliosides are known to play a role in cell differentiation and growth regulation. Altered ganglioside levels have been associated with oncogenic transformation or inherited disease such as Farber’s disease (Farina et al., 2000; Manzi et al., 1990; Zeng et al., 2000), although very little is known concerning the mechanism or the biological significance of these changes. However, ganglioside changes and their involvement in diabetes where cell growth is also altered have been poorly studied.
In the present study, ganglioside modifications and their consequences on proliferation of pericytes submitted to diabetic environment were investigated. Glucosamine, which is avidly taken up by the glucose transporter and phosphorylated by hexokinase when added to cells (Schleicher and Weigert, 2000), was used to mimic the high-glucose environment effects that are mediated by the HP in our model. Pericytes were chosen because their growth is particularly affected in diabetic microangiopathy. Results demonstrate that glucosamine treatment induces modification of BRP ganglioside profile with an increase of GM1 and GD3 and a decrease of GM3. Moreover, glucosamine increased GM3 synthase activity, which regulates GM3 biosynthesis, a precursor of complex gangliosides. Thus, by increasing GM3 synthase activity, glucosamine could drive complex ganglioside biosynthesis. This hypothesis is supported by the observed increase of GM1 and GD3. Glucosamine regulates GM3 synthase activity through an as yet undefined mechanism. One possible explanation is through regulation of GM3 synthase gene expression. In fact, human GM3 synthase promoter presents putative binding sites for SP1 (Zeng et al., 2003), a transcription factor whose activity is known to be regulated by O-linked N-acetylglucosamine modification (Goldberg et al., 2002). On the other hand, it should also be considered that glucosamine can lead to increased ganglioside biosynthesis by providing excessive substrates that increase the flux of ganglioside biosynthesis in glucosamine-treated pericytes. Indeed, UDP-GlcNAc can be converted into CMP–sialic acid, a precursor of ganglioside biosynthesis.
Next, results showed that glucosamine causes a decrease of pericyte proliferation. This proliferation decrease is partially reproduced by the application of exogenous gangliosides including GM1 and GD3, both increased in response to glucosamine. This observation suggests a role of gangliosides in mediating glucosamine effects. Of note, previous studies have documented that only 20% of exogenously added gangliosides are inserted into cell membranes (Bremer et al., 1984). This might explain the less potent effects of exogenous gangliosides on decreasing pericyte proliferation as compared to glucosamine. These results are in accordance with other studies showing that gangliosides can decrease cell growth by modulating growth factor receptor signaling. For example, GM1 has been shown to inhibit epidermal growth factor and platelet-derived growth factor receptor phosphorylation and signaling in different cell types (Bremer et al., 1986; Mirkin et al., 2002; Sachinidis et al., 1996; Van Brocklyn et al., 1993). Moreover, GD3 has been described as an intracellular mediator of apoptosis, particularly by inducing mitochondrial permeability transition, cytochrome c release, and caspase activation (Garcia-Ruiz et al., 2000; Kristal and Brown, 1999; Rippo et al., 2000).
A complementary approach using PPMP, an inhibitor of glucosylceramide synthase, was used next. Addition of PPMP to glucosamine treatment partially protected pericytes against the proliferation decrease, supporting a role of gangliosides in mediating the glucosamine effects. These data also suggest that unknown additional pathways are also involved in causing decrease of pericyte proliferation in response to glucosamine. As discussed earlier, the HP can affect cell proliferation through several pathways and mechanisms. Activation of the HP leads to O-GlcNAc modifications of proteins such as transcription factors (Wells et al., 2001). For example, it has been shown in bovine aortic endothelial cells that transcription factor SP1 is modified by O-GlcNAc in response to hyperglycemia or elevated glucosamine (Du et al., 2000). Increased O-GlcNAc modification of SP1 increases SP1 transactivation and SP1-dependent expression of transforming growth factor ß1 and PAI-1 (Du et al., 2000). Interestingly, SP1 has also been shown to regulate the expression of proteins involved in cell cycle regulation, such as p21waf1/cip1 (Gartel and Tyner, 1999). As in our study, glucosamine did not inhibit BRP proliferation through apoptosis; it would be of great interest to investigate the effect of glucosamine on cell cycle proteins such as p21waf1/cip1 in these cells.
In conclusion, the present study indicates that glucosamine increases ganglioside biosynthesis in pericytes and suggests that gangliosides are likely involved in the antiproliferative effect of glucosamine in this cell type. These observations also indicate that the ganglioside pattern can be modified by a diabetic environment and extend the role of gangliosides into the field of diabetic microvascular complications.
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Materials and methods |
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Cell isolation and culture
BRPs were isolated from microvessels of bovine retinas as previously described (Lecomte et al., 1996
). Briefly, retinas were dissected under sterile conditions from freshly enucleated bovine eyes obtained from a local slaughterhouse. Retinas (2 per culture dish) were minced into small pieces and homogenized in a Dounce homogenizer in Hank’s balanced salt solution (HBSS) buffer (HBSS) supplemented with 10 mM HEPES, pH 7.4, 1% antibiotics, 0.5% bovine serum albumin (BSA) (Sigma, Saint-Quentin Fallavier, France). The homogenates were then digested at 37°C for 20 min in a solution of collagenase/dispase (Roche Diagnostics, Mannheim, Germany). After digestion, microvessels fragments were trapped onto a 40-µm nylon filter and plated in 6-cm fibronectin-coated dishes. Outgrowth of pericytes from the microvessels occurred after about 48 h. Primary cultures were grown in DMEM supplemented with 10% fetal bovine serum (Gibco, Invitrogen, NY), 1% glutamine, and 1% penicillin/streptomycin (Sigma). Cells were passaged with trypsin–ethylenediamine tetra-acetic acid (Sigma) (1:3) and cultured up to the second passage during which they were treated. Glucosamine (Sigma) was added to the culture medium at 5 mM final concentration, and culture medium was replaced every 2 days. BRPs were treated for 1–7 days.
Ganglioside analysis
At the end of the treatment period, pericytes (5–8 x 105 cells) were collected by trypsination and washed twice with phosphate buffered saline (PBS, Sigma). For metabolic labeling of gangliosides, 0.2 µCi/ml of [14C(U)]D-galactose (329.5 mCi/mmol) (PerkinElmer Life Sciences, Boston, MA) was added to the media overnight before harvesting as galactose incorporates into all gangliosides. Cell pellets were dispersed into 2 ml chloroform (C)/methanol (M) (1:1, v/v), mixed thoroughly, and extracted overnight at 4°C. After centrifugation, the residues were extracted twice with 2 ml of the same solvent. The pooled extracts of total lipids were evaporated to dryness and submitted to partition with C/M/PBS 1 mM (10:10:7, v/v/v). The upper phases containing gangliosides were next desalted on C18 silica gel column (Waters, Milford, MA) and analyzed by high-performance thin-layer chromatography (HPTLC) (Merck, Darmstadt, Germany). Plates were developed in C/M/0.2% CaCl2 (55:45:10, v/v/v) and gangliosides were visualized by autoradiography using phosphor screen and Storm 820 (Molecular Dynamics, Amersham Pharmacia Biotech, Piscataway, NJ) and by resorcinol staining (gangliosides-specific stain: resorcinol 0.3% [Sigma], 0.03% CuSO4, 30% HCl) with Image Master VDS-CL (Amersham Pharmacia Biotech). Gangliosides were identified by comigration with standards (Matreya, Biovalley, Marne la Vallée, France). Quantification was done by densitometry analysis with Image Quant (Molecular Dynamics). Because GT1b is absent in BRP ganglioside profile, it was added as an internal standard in the samples before lipid extraction. Results were adjusted to the total proteins of the sample and the extraction efficiency.
Measurement of GM3 synthase activity
At the end of treatment, cells were washed with PBS, incubated for 20 min at 4°C in 50 µl lysis buffer (20 mM sodium cacodylate, pH 6.6 [Sigma], 0.2% Triton X-100, 1 mM ethylenediamine tetra-acetic acid, 10 µl/ml proteases inhibitors, Calbiochem, Merck) and then collected by scrapping. Four dishes of BRP (2–3 x 106 cells) were pooled. Cell lysates were centrifuged at 10,000 x g for 5 min, and proteins in the supernatants were used to measure GM3 synthase activity. Equal amounts of proteins from each sample (500 µg) were used to perform the assay. Samples were mixed with an equal volume of reaction buffer containing at final concentrations: 0.1 mM lactosylceramide (Matreya), 4 µCi/ml [sialic-4,5,6,7,8,9-14C]CMP–sialic acid (325.2 mCi/mmol) (PerkinElmer Life Sciences), 100 µM CMP–sialic acid (Sigma), 10 mM MgCl2, 0.2% Triton X-100, 100 mM sodium cacodylate, pH 6.6. After shaking, the reaction mixtures were incubated at 37°C for 150 min. Reactions were stopped by loading the samples on silica gel 60 columns (Merck) to separate excess of substrates from products. After washing the columns with water, gangliosides were eluted with C/M (1:1, v/v) and the solvent dried under nitrogen. Gangliosides were finally separated by thin-layer chromatography (Merck), and reaction products were revealed by autoradiography. GM3 synthase activity was expressed as pmoles of GM3 produced per hour/mg proteins.
Measurement of cell growth
After each treatment period, cells were harvested with trypsin, and cell pellets were washed twice with PBS. For each sample, an aliquot of cells was counted using a hemocytometer to determine the cell number, another aliquot was used to measure proteins.
Treatment with exogenous gangliosides
To evaluate the effect of exogenous gangliosides on BRP proliferation, cells were cultured in 96-well plates. Exogenous glycolipids GM1, GD3, glucosylceramide, and lactosylceramide (Matreya) were added to the culture complete medium at final concentrations of 10, 50, or 100 µM in the form of complexes with BSA at a ratio of 1:1 in DMEM–10 mM HEPES, pH 7.4, to facilitate their incorporation within the cell. At the end of treatment, cells were washed twice with PBS and lysed for 30 min at 37°C in 50 µl Ripa lysis buffer (PBS 10 mM, NP40 1%; Pierce, Perbio Science, Brebières, France), sodium deoxycholate 0.5%, sodium dodecyl sulfate 0.1%, 10 µl/ml protease inhibitors). Total proteins were finally measured using the BCA protein assay (Pierce) to assess cell proliferation, because in our experiments cell numbers correlated with total protein concentrations (see Figure 1).
PPMP treatment
To inhibit ganglioside biosynthesis, PPMP (Sigma), an inhibitor of glucosylceramide synthase that catalyses the first step of ganglioside biosynthesis, was used. BRP were cultured in 96-well plates and treated with 5 mM glucosamine in the presence of increasing concentrations of PPMP for 7 days. PPMP was not used at concentrations higher than 1 µM because it caused cellular morphological alterations and toxic effects. At the end of treatment, cells were washed twice with PBS and lysed in Ripa; proteins were measured to assess cell proliferation as described.
Statistical analysis
Data are expressed as means ± SEM and presented as percentage of controls. The Wilcoxon signed-rank test was used to define the significance of the difference between groups. p < 0.05 was considered statistically significant.
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Abbreviations |
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BRP, bovine retinal pericyte; BSA, bovine serum albumin; DMEM, Dulbecco’s modified Eagle’s medium; GFAT, glucosamine-6-phosphate by glutamine:F-6-P amidotransferase; HBSS, Hank’s balanced salt solution; HP, hexosamine pathway; HPTLC, high-performance thin-layer chromatography; PBS, phosphate buffered saline; PPMP, DL-threo-1-phenyl-2-palmitoylamino-3-morpholino-1-propanol
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References |
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TopAbstractIntroductionResultsDiscussionMaterials and methodsReferences |
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Bremer, E.G., Hakomori, S., Bowen-Pope, D.F., Raines, E., and Ross, R. (1984) Ganglioside-mediated modulation of cell growth, growth factor binding, and receptor phosphorylation. J. Biol. Chem., 259, 6818–6825.
Bremer, E.G., Schlessinger, J., and Hakomori, S. (1986) Ganglioside-mediated modulation of cell growth. Specific effects of GM3 on tyrosine phosphorylation of the epidermal growth factor receptor. J. Biol. Chem., 261, 2434–2440.
Du, X.L., Edelstein, D., Rossetti, L., Fantus, I.G., Goldberg, H., Ziyadeh, F., Wu, J., and Brownlee, M. (2000) Hyperglycemia-induced mitochondrial superoxide overproduction activates the hexosamine pathway and induces plasminogen activator inhibitor-1 expression by increasing Sp1 glycosylation. Proc. Natl Acad. Sci. USA, 97, 12222–12226.
Farina, F., Cappello, F., Todaro, M., Bucchieri, F., Peri, G., Zummo, G., and Stassi, G. (2000) Involvement of caspase-3 and GD3 ganglioside in ceramide-induced apoptosis in Farber disease. J. Histochem. Cytochem., 48, 57–62.
Forrester, J.V., Knott, R.M., Pickup, J., and Williams G. (1997) Pathogenesis of diabetic retinopathy and cataract. Blackwell Sci., 45, 1–19.
Garcia-Ruiz, C., Colell, A., Paris, R., and Fernandez-Checa, J.C. (2000) Direct interaction of GD3 ganglioside with mitochondria generates reactive oxygen species followed by mitochondrial permeability transition, cytochrome c release, and caspase activation. FASEB J., 14, 847–858.
Gartel, A.L. and Tyner, A.L. (1999) Transcriptional regulation of the p21((WAF1/CIP1)) gene. Exp. Cell Res., 246, 280–289.[CrossRef][ISI][Medline]
Goldberg, H.J., Whiteside, C.I., and Fantus, I.G. (2002) The hexosamine pathway regulates the plasminogen activator inhibitor-1 gene promoter and Sp1 transcriptional activation through protein kinase C-beta I and -delta. J. Biol. Chem., 277, 33833–33841.
Hakomori, S. (1990) Bifunctional role of glycosphingolipids. Modulators for transmembrane signaling and mediators for cellular interactions. J. Biol. Chem., 265, 18713–18716.
Heath, H., Paterson, R.A., and Hart, J.C. (1967) Changes in the hydroxyproline, hexosamine and sialic acid of the diabetic human and beta, beta’-iminodipropionitrile-treated rat retinal vascular systems. Diabetologia, 3, 515–518.[CrossRef][Medline]
Hebert, L.F. Jr., Daniels, M.C., Zhou, J., Crook, E.D., Turner, R.L., Simmons, S.T., Neidigh, J.L., Zhu, J.S., Baron, A.D., and McClain, D.A. (1996) Overexpression of glutamine:fructose-6-phosphate amidotransferase in transgenic mice leads to insulin resistance. J. Clin. Invest., 98, 930–936.[ISI][Medline]
Kaneto, H., Xu, G., Song, K.H., Suzuma, K., Bonner-Weir, S., Sharma, A., and Weir, G.C. (2001) Activation of the hexosamine pathway leads to deterioration of pancreatic beta-cell function through the induction of oxidative stress. J. Biol. Chem., 276, 31099–31104.
Kolm-Litty, V., Sauer, U., Nerlich, A., Lehmann, R., and Schleicher, E.D. (1998) High glucose-induced transforming growth factor beta1 production is mediated by the hexosamine pathway in porcine glomerular mesangial cells. J. Clin. Invest., 101, 160–169.[ISI][Medline]
Kristal, B.S. and Brown, A.M. (1999) Ganglioside GD3, the mitochondrial permeability transition, and apoptosis. Ann. NY Acad. Sci., 893, 321–324.
Lecomte, M., Paget, C., Ruggiero, D., Wiernsperger, N., and Lagarde, M. (1996) Docosahexaenoic acid is a major n-3 polyunsaturated fatty acid in bovine retinal microvessels. J. Neurochem., 66, 2160–2167.[ISI][Medline]
Manzi, A.E., Sjoberg, E.R., Diaz, S., and Varki, A. (1990) Biosynthesis and turnover of O-acetyl and N-acetyl groups in the gangliosides of human melanoma cells. J. Biol. Chem., 265, 13091–13103.
Marshall, S. (2002) The hexosamine signaling pathway: a new road to drug discovery. Curr. Opin. Endocrinol. and Diabetes., 9, 160–167.[CrossRef]
Marshall, S., Bacote, V., and Traxinger, R.R. (1991) Discovery of a metabolic pathway mediating glucose-induced desensitization of the glucose transport system. Role of hexosamine biosynthesis in the induction of insulin resistance. J. Biol. Chem., 266, 4706–4712.
Mazlen, R.G., Muellenberg, C.G., and O’Brien, P.J. (1970) L-glutamine D-fructose 6-phosphate amidotransferase from bovine retina. Exp. Eye Res., 9, 1–11.[CrossRef][ISI][Medline]
Mirkin, B.L., Clark, S.H., and Zhang, C. (2002) Inhibition of human neuroblastoma cell proliferation and EGF receptor phosphorylation by gangliosides GM1, GM3, GD1A and GT1B. Cell Prolif., 35, 105–115.[CrossRef][ISI][Medline]
Nakatsuji, Y. and Miller, R.H. (2001) Selective cell-cycle arrest and induction of apoptosis in proliferating neural cells by ganglioside GM3. Exp. Neurol., 168, 290–299.[CrossRef][ISI][Medline]
Rippo, M.R., Malisan, F., Ravagnan, L., Tomassini, B., Condo, I., Costantini, P., Susin, S.A., Rufini, A., Todaro, M., Kroemer, G., and Testi, R. (2000) GD3 ganglioside as an intracellular mediator of apoptosis. Eur. Cytokine Netw., 11, 487–488.[ISI][Medline]
Sachinidis, A., Kraus, R., Seul, C., Meyer zu Brickwedde, M.K., Schulte, K., Ko, Y., Hoppe, J., and Vetter, H. (1996) Gangliosides GM1, GM2 and GM3 inhibit the platelet-derived growth factor-induced signalling transduction pathway in vascular smooth muscle cells by different mechanisms. Eur.J.Cell Biol., 71, 79–88.
Schleicher, E.D. and Weigert, C. (2000) Role of the hexosamine biosynthetic pathway in diabetic nephropathy. Kidney Int. Suppl., 77, S13–S18.[CrossRef][Medline]
Singh, L.P., Andy, J., Anyamale, V., Greene, K., Alexander, M., and Crook, E.D. (2001) Hexosamine-induced fibronectin protein synthesis in mesangial cells is associated with increases in cAMP responsive element binding (CREB) phosphorylation and nuclear CREB: the involvement of protein kinases A and C. Diabetes, 50, 2355–2362.
Van Brocklyn, J., Bremer, E.G., and Yates, A.J. (1993) Gangliosides inhibit platelet-derived growth factor-stimulated receptor dimerization in human glioma U-1242MG and Swiss 3T3 cells. J. Neurochem., 61, 371–374.[CrossRef][ISI][Medline]
van Echten, G. and Sandhoff, K. (1993) Ganglioside metabolism. Enzymology, topology, and regulation. J. Biol. Chem., 268, 5341–5344.
Vosseller, K., Wells, L., Lane, M.D., and Hart, G.W. (2002) Elevated nucleocytoplasmic glycosylation by O-GlcNAc results in insulin resistance associated with defects in Akt activation in 3T3-L1 adipocytes. Proc. Natl Acad. Sci. USA, 99, 5313–5318.
Wells, L., Vosseller, K., and Hart, G.W. (2001) Glycosylation of nucleocytoplasmic proteins: signal transduction and O-GlcNAc. Science, 291, 2376–2378.
Zeng, G., Gao, L., Birkle, S., and Yu, R.K. (2000) Suppression of ganglioside GD3 expression in a rat F-11 tumor cell line reduces tumor growth, angiogenesis, and vascular endothelial growth factor production. Cancer Res., 60, 6670–6676.
Zeng, G., Gao, L., Xia, T., Tencomnao, T., and Yu, R.K. (2003) Characterization of the 5'-flanking fragment of the human GM3-synthase gene. Biochim. Biophys. Acta, 1625, 30–35.[Medline]
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