Sandro Sonnino - Profile on Academia.edu (original) (raw)

Papers by Sandro Sonnino

A Glycosphingolipid/Caveolin-1 Signaling Complex Inhibits Motility of Human Ovarian Carcinoma Cells

Journal of Biological Chemistry, 2011

Journal of Neurochemistry, 2019

† Dedicated to the memory of Dr. Riccardo Casellato, whose scientific contribution was fundamenta... more † Dedicated to the memory of Dr. Riccardo Casellato, whose scientific contribution was fundamental to improve the synthesis of photoactivable gangliosides.

Glycoconjugate Journal, 2000

The conformations and dynamics of gangliosides GM1, GM2, 6'-GM2 and GM4 have been studied by ... more The conformations and dynamics of gangliosides GM1, GM2, 6'-GM2 and GM4 have been studied by computational means, and the results compared to NMR data. Unconstrained conformational searches were run using the AMBER* force field augmented by MNDO derived parameters for the Neu5Ac anomeric torsion, the GB/SA water solvation model, and the MC/EM alogorithm; extended (10–12[emsp4 ]ns) dynamic simulations in GB/SA

Neurochemistry International, 1992

A~tract-The incubation of cultured rat cerebellar granule cells w,th a photoreactwe denvatwe of r... more A~tract-The incubation of cultured rat cerebellar granule cells w,th a photoreactwe denvatwe of radiolabeled GMI ganghoside, [3H]GMI(N3), followed by dlummation, led to the speofic assoclahon of ganghoslde to cell proteins After 30 rain of incubaUon only a few out of the cell proteins became radlolabeled Two of these, at apparent molecular weights of 95 and 112 kDa, are interacting with the portion of associated ganghoslde that is released by trypsin treatment, others, in the region between 31 and 44 kDa, are probably bound to molecules of ganghoside inserted into the outer membrane layer, thus showing that the ganghos~de association to the cell surface is a selective phenomenon, mvolving specific proteins Increasing the incubation time up to 24 h resulted in a larger number of ra&olabeled proteins, probably as a consequence of the internahzatlon and metabolic processing of admimstered [3H]GM I(N3) In fact, photoreactive and ra&oactwe metabolic denvat,ves of [~H]GMI(N0 can also interact with a number of proteins After 24 h incubation, some radioactivity was also associated to cytosohc proteins Again in this case the interaction with proteins seems to be a specific process lnvolwng only a few out of the total cytosohc proteins Ganghos~des, smhc acid containing glycosphmgollplds, are components of the external hpld layer of vertebrate cells plasma membrane and are *Parts of the results of this refereed paper were presented at the ESN workshop on Glycoconjugate~ and Neuronal Membrane Functton, held in Leipzig, 23

Neurochemistry International, 1982

Abstraet-A procedure for accurate densitometric quantification of gangliosides separated by two-d... more Abstraet-A procedure for accurate densitometric quantification of gangliosides separated by two-dimensional thin layer chromatograph 3 is reported. The procedure was set up employing 9 different pure gangliosides and was applied to the analysis of calf and pig brain gangliosides. Silica gel high performance thin layer plates, 10 × 10cm. were two-dimensionally developed at 18-20 C with the following solvents: chloroform/methanol;0.2°~, aqueous CaCI.,. 50/4010 by volume, for the first run: n-propanol 17M NHaOH,water. 6,'2;1 by volume for the second run. Ganglioside spots were visualized b3 spraying with an Ehrlich reagent, which is specific for sialic acid. and heating at 120 C for 15rain. The spots were quantified by sequential scanning densitometry, linear responses being obtained for ganglioside amounts on the plate ranging from 0.1 to 6 nmol as bound siatic acid. The reproducibilit 3 of densitometric responses resulted to be acceptable since the standard deviation values were lower than ± 15". of the mean values also for those ganglioside species contained in minor proportions. The ganglioside mixtures of calf and pig brain were resolved in about 20 spots. Of these 9 corresponded to gangliosides GM3. GM2. GMI. Fuc-GMI. GDIa, GDlb. Fuc-GDlb. GTIb and GQlb. which were identified with certainty and quantified. The identification of GM3 (carrying N-glycolylneuraminic acidl. GD3. GDla Icarrying N-acetyl-and N-glycolyl-neuraminic acid) and GTIa was only tentative. All the other spots corresponded to unidentified gangliosides, some of them possibly new species.

Journal of Neurochemistry, 1991

GDI b and GD 1 b-lactone (GD 1 b-L) gangliosides bind to the same extent to a Pp crude membrane p... more GDI b and GD 1 b-lactone (GD 1 b-L) gangliosides bind to the same extent to a Pp crude membrane preparation from rat brain. After 30 min of incubation with and M solutions of ganglioside, 1,800, 450, and 100 pmol of ganglioside/mg of protein, respectively, were found to be stably associated to the P2 fraction. This association modifies the phosphorylation process of the P2 membrane proteins in a dose-dependent manner, the maximal effect being reached at a ganglioside association of I .85 nmol/mg of protein and in large part at 450 pmol/mg of protein. The effects of GD 1 b and GD 1 b-L on the phosphorylation of five proteins, showing apparent molecular masses of 17, 20, 36, 41, and 44 kDa, were different after 0.5 min of phosphorylation reaction as well as after 15 min. After 0.5 rnin of re-action, in the presence of stably associated GDlb, the phosphorylation of the 36-, 4 I-, and 44-kDa proteins was increased with reference to the control, whereas the phosphorylation of the 17-and 20-kDa proteins was decreased. GDlb-L exerted qualitatively similar effects only on the 44-, 41-, and 36-kDa proteins and to a strongly reduced degree. After 15 rnin of reaction, only the phosphorylation of the 36-kDa protein was stimulated by GD I b; G D 1 b-L exerted a similar effect, but to a low degree.

The Journal of Lipid Research, 2010

and ovarian cancers, neuroblastoma, lymphoma, and leukemia. Many pieces of evidence indicate a li... more and ovarian cancers, neuroblastoma, lymphoma, and leukemia. Many pieces of evidence indicate a link between HPR's antitumor effect and the metabolism of sphingolipids in tumor cells. As for many other anticancer drugs, the studies in tumor cell lines indicated that apoptosis is the major cytotoxic mechanism for HPR [even if the toxic effect of HPR is likely very complex and at least in part due to nonapoptotic mechanisms (2, 3)], and HPR-induced apoptosis in cancer cells has been ascribed to the increased cellular levels of ceramide, a sphingolipid mediator playing multiple roles in apoptotic signaling, elicited by HPR (4). The main metabolic mechanism responsible for HPR-induced production of ceramide is represented by de novo synthesis. Exposure to HPR of human neuroblastoma (5) and prostate cancer cells (6) resulted in a time-and dose-dependent increase in the activity of serine palmitoyltansferase and (dihydro)ceramide synthase, which catalyze early steps in the biosynthesis of ceramide and derived sphingolipids (7), and the treatment of cultured cells with pharmacological inhibitors of these enzymes was able to block HPR-induced ceramide increase (5, 6, 8). However, the effects of HPR on sphingolipid metabolism are probably much more complex and still poorly understood. For example, the possible role of sphingomyelin turnover due to the action of sphingomyelinases in the HPRelicited ceramide production is still controversial, and confl icting results have been reported (8, 9). In neuroblastoma Abstract The dihydroceramide, ceramide, sphingomyelin, lactosylceramide, and ganglioside species of A2780 human ovarian carcinoma cells treated with the synthetic retinoids N-(4-hydroxyphenyl)retinamide (fenretinide, 4-HPR) and 4-oxo-N-(4-hydroxyphenyl)retinamide (4-oxo-4-HPR) in culture were characterized by ESI-MS. We characterized 32 species of ceramide and dihydroceramide, 15 of sphingomyelin, 12 of lactosylceramide, 9 of ganglioside GM2, and 6 of ganglioside GM3 differing for the long-chain base and fatty acid structures. Our results indicated that treatment with both 4-HPR and 4-oxo-4-HPR led to a marked increase in dihydroceramide species, while only 4-oxo-4-HPR led to a minor increase of ceramide species. Dihydroceramides generated in A2780 cells in response to 4-HPR or 4-oxo-4-HPR differed for their fatty acid content, suggesting that the two drugs differentially affect the early steps of sphingolipid synthesis. Dihydroceramides produced upon treatments with the drugs were further used for the synthesis of complex dihydrosphingolipids, whose levels dramatically increased in drug-treated cells.

The Journal of Lipid Research, 2003

Treatment with methyl-␤-cyclodextrin (MCD) induced a time-and dose-dependent efflux of cholestero... more Treatment with methyl-␤-cyclodextrin (MCD) induced a time-and dose-dependent efflux of cholesterol, sphingolipids, and phosphatidylcholine (PC) from cerebellar neurons differentiated in culture. With a "mild" treatment, the loss of cell lipids induced a deep reorganization of the remaining membrane lipids. In fact, the amount of PC associated with a Triton X-100-insoluble membrane fraction (highly enriched in sphingolipids and cholesterol in nontreated cells) was lowered by the treatment. This suggested a reduction of the lipid domain area. However, the cholesterol and sphingolipid enrichment of this fraction remained substantially unchanged, suggesting the existence of dynamic processes aimed at preserving the segregation of cholesterol and sphingolipids in membrane domains. Under these conditions, the lipid membrane domains retained the ability to sort signaling proteins, such as Lyn and c-Src, but cells displayed deep alterations in their membrane permeability. However, normal membrane permeability was restored by loading cells with cholesterol. When MCD treatment was more stringent, a large loss of cell lipids occurred, and the lipid domains were much less enriched in cholesterol and lost the ability to sort specific proteins. The loss of the integrity and properties of lipid domains was accompanied by severe changes in the membrane permeability, distress, and eventually cell death.-Ottico, E., A.

Journal of Biological Chemistry, 2002

In the present work, we studied the effects of fenretinide (N-(4-hydroxyphenyl)retinamide (HPR)),... more In the present work, we studied the effects of fenretinide (N-(4-hydroxyphenyl)retinamide (HPR)), a hydroxyphenyl derivative of all-trans-retinoic acid, on sphingolipid metabolism and expression in human ovarian carcinoma A2780 cells. A2780 cells, which are sensitive to a pharmacologically achievable HPR concentration, become 10-fold more resistant after exposure to increasing HPR concentrations. Our results showed that HPR was able to induce a dose-and time-dependent increase in cellular ceramide levels in sensitive but not in resistant cells. This form of resistance in A2780 cells was not accompanied by the overexpression of multidrug resistance-specific proteins MDR1 P-glycoprotein and multidrug resistance-associated protein, whose mRNA levels did not differ in sensitive and resistant A2780 cells. HPR-resistant cells were characterized by an overall altered sphingolipid metabolism. The overall content in glycosphingolipids was similar in both cell types, but the expression of specific glycosphingolipids was different. Specifically, our findings indicated that glucosylceramide levels were similar in sensitive and resistant cells, but resistant cells were characterized by a 6-fold lower expression of lactosylceramide levels and by a 6-fold higher expression of ganglioside levels than sensitive cells. The main gangliosides from resistant A2780 cells were identified as GM3 and GM2. The possible metabolic mechanisms leading to this difference were investigated. Interestingly, the mRNA levels of glucosylceramide and lactosylceramide synthases were similar in sensitive and resistant cells, whereas GM3 synthase mRNA level and GM3 synthase activity were remarkably higher in resistant cells.

FEBS Letters, 2009

Human fibroblasts produce ceramide from sialyllactosylceramide on the plasma membranes. Sialidase... more Human fibroblasts produce ceramide from sialyllactosylceramide on the plasma membranes. Sialidase Neu3 is known to be plasma membrane associated, while only indirect data suggest the plasma membrane association of b-galactosidase and b-glucosidase. To determine the presence of b-galactosidase and b-glucosidase on plasma membrane, cells were submitted to cell surface biotinylation. Biotinylated proteins were purified by affinity column and analyzed for enzymatic activities on artificial substrates. Both enzyme activities were found associated with the cell surface and were up-regulated in Neu3 overexpressing cells. These enzymes were capable to act on both artificial and natural substrates without any addition of activator proteins or detergents and displayed a trans activity in living cells.

FEBS Letters, 2009

Caveolin-1, and probably also-2 and-3, can organize multimolecular membrane complexes involved in... more Caveolin-1, and probably also-2 and-3, can organize multimolecular membrane complexes involved in transmembrane traffic, cell adhesion and signal transduction. In this review, we discuss on the importance of caveolin membrane environment in regulating the architecture and function of such complexes, with a special emphasis on the role of sphingolipids.

Chemistry and Physics of Lipids, 1988

N-Glycolylneuraminic acid containing GM 1, GM l(NeuGc), was prepared by semisynthetic procedure. ... more N-Glycolylneuraminic acid containing GM 1, GM l(NeuGc), was prepared by semisynthetic procedure. The procedure makes use of GM 1 ganglioside deacetylated at the level of sialic acid residue (deAc-GM 1) and of 1,3-dioxalan-2,4-dione. DeAc-GM 1 is prepared from GM 1 by alkaline hydrolysis in the presence of tetramethylammonium hydroxide and the glycolylating compound by reaction of glycolic acid with phosgene in dioxane, followed by cyclization under vacuum. Mass spectrometric and nuclear magnetic resonance spectroscopy analyses clearly indicated the presence, in the neosynthesized ganglioside of a glycolic group in the sialic acid residue. Laser-light scattering measurements show that GM l(NeuGc) aggregates in aqueous media being present in solution as micelles with a molecular weight of 576,000 and a hydrodynamic radius of 62.4/~, as determined at 25°C. GM 1 (NeuGc) promotes neurite outgrowth in N-2a cells to a similar degree as GMI(NeuAc), but shows different behaviour under treatment with sialidase from Arthrobacter ureafaciens.

Biochemistry, 1989

A new procedure was used to synthesize a derivative of ganglioside GM1 containing a photoreactive... more A new procedure was used to synthesize a derivative of ganglioside GM1 containing a photoreactive nitrophenyl azide group at the end of the fatty acyl moiety, using deAc-deAcyl-GM1 obtained by deacetylation of the sialic acid and deacylation of the ceramide portion of GM1. This deAc-deAcyl-GM1 was first acylated at the long chain base amino group with 12-aminododecanoic acid, which has the amino group protected by a fluorenyl residue, and tritium labeled a t the sialic acid amino group with [3H]acetic anhydride of very high specific radioactivity. The fluorenyl group removed by ammonia treatment was

A Glycosphingolipid/Caveolin-1 Signaling Complex Inhibits Motility of Human Ovarian Carcinoma Cells

Journal of Biological Chemistry, 2011

Journal of Neurochemistry, 2019

† Dedicated to the memory of Dr. Riccardo Casellato, whose scientific contribution was fundamenta... more † Dedicated to the memory of Dr. Riccardo Casellato, whose scientific contribution was fundamental to improve the synthesis of photoactivable gangliosides.

Glycoconjugate Journal, 2000

The conformations and dynamics of gangliosides GM1, GM2, 6'-GM2 and GM4 have been studied by ... more The conformations and dynamics of gangliosides GM1, GM2, 6'-GM2 and GM4 have been studied by computational means, and the results compared to NMR data. Unconstrained conformational searches were run using the AMBER* force field augmented by MNDO derived parameters for the Neu5Ac anomeric torsion, the GB/SA water solvation model, and the MC/EM alogorithm; extended (10–12[emsp4 ]ns) dynamic simulations in GB/SA

Neurochemistry International, 1992

A~tract-The incubation of cultured rat cerebellar granule cells w,th a photoreactwe denvatwe of r... more A~tract-The incubation of cultured rat cerebellar granule cells w,th a photoreactwe denvatwe of radiolabeled GMI ganghoside, [3H]GMI(N3), followed by dlummation, led to the speofic assoclahon of ganghoslde to cell proteins After 30 rain of incubaUon only a few out of the cell proteins became radlolabeled Two of these, at apparent molecular weights of 95 and 112 kDa, are interacting with the portion of associated ganghoslde that is released by trypsin treatment, others, in the region between 31 and 44 kDa, are probably bound to molecules of ganghoside inserted into the outer membrane layer, thus showing that the ganghos~de association to the cell surface is a selective phenomenon, mvolving specific proteins Increasing the incubation time up to 24 h resulted in a larger number of ra&olabeled proteins, probably as a consequence of the internahzatlon and metabolic processing of admimstered [3H]GM I(N3) In fact, photoreactive and ra&oactwe metabolic denvat,ves of [~H]GMI(N0 can also interact with a number of proteins After 24 h incubation, some radioactivity was also associated to cytosohc proteins Again in this case the interaction with proteins seems to be a specific process lnvolwng only a few out of the total cytosohc proteins Ganghos~des, smhc acid containing glycosphmgollplds, are components of the external hpld layer of vertebrate cells plasma membrane and are *Parts of the results of this refereed paper were presented at the ESN workshop on Glycoconjugate~ and Neuronal Membrane Functton, held in Leipzig, 23

Neurochemistry International, 1982

Abstraet-A procedure for accurate densitometric quantification of gangliosides separated by two-d... more Abstraet-A procedure for accurate densitometric quantification of gangliosides separated by two-dimensional thin layer chromatograph 3 is reported. The procedure was set up employing 9 different pure gangliosides and was applied to the analysis of calf and pig brain gangliosides. Silica gel high performance thin layer plates, 10 × 10cm. were two-dimensionally developed at 18-20 C with the following solvents: chloroform/methanol;0.2°~, aqueous CaCI.,. 50/4010 by volume, for the first run: n-propanol 17M NHaOH,water. 6,'2;1 by volume for the second run. Ganglioside spots were visualized b3 spraying with an Ehrlich reagent, which is specific for sialic acid. and heating at 120 C for 15rain. The spots were quantified by sequential scanning densitometry, linear responses being obtained for ganglioside amounts on the plate ranging from 0.1 to 6 nmol as bound siatic acid. The reproducibilit 3 of densitometric responses resulted to be acceptable since the standard deviation values were lower than ± 15". of the mean values also for those ganglioside species contained in minor proportions. The ganglioside mixtures of calf and pig brain were resolved in about 20 spots. Of these 9 corresponded to gangliosides GM3. GM2. GMI. Fuc-GMI. GDIa, GDlb. Fuc-GDlb. GTIb and GQlb. which were identified with certainty and quantified. The identification of GM3 (carrying N-glycolylneuraminic acidl. GD3. GDla Icarrying N-acetyl-and N-glycolyl-neuraminic acid) and GTIa was only tentative. All the other spots corresponded to unidentified gangliosides, some of them possibly new species.

Journal of Neurochemistry, 1991

GDI b and GD 1 b-lactone (GD 1 b-L) gangliosides bind to the same extent to a Pp crude membrane p... more GDI b and GD 1 b-lactone (GD 1 b-L) gangliosides bind to the same extent to a Pp crude membrane preparation from rat brain. After 30 min of incubation with and M solutions of ganglioside, 1,800, 450, and 100 pmol of ganglioside/mg of protein, respectively, were found to be stably associated to the P2 fraction. This association modifies the phosphorylation process of the P2 membrane proteins in a dose-dependent manner, the maximal effect being reached at a ganglioside association of I .85 nmol/mg of protein and in large part at 450 pmol/mg of protein. The effects of GD 1 b and GD 1 b-L on the phosphorylation of five proteins, showing apparent molecular masses of 17, 20, 36, 41, and 44 kDa, were different after 0.5 min of phosphorylation reaction as well as after 15 min. After 0.5 rnin of re-action, in the presence of stably associated GDlb, the phosphorylation of the 36-, 4 I-, and 44-kDa proteins was increased with reference to the control, whereas the phosphorylation of the 17-and 20-kDa proteins was decreased. GDlb-L exerted qualitatively similar effects only on the 44-, 41-, and 36-kDa proteins and to a strongly reduced degree. After 15 rnin of reaction, only the phosphorylation of the 36-kDa protein was stimulated by GD I b; G D 1 b-L exerted a similar effect, but to a low degree.

The Journal of Lipid Research, 2010

and ovarian cancers, neuroblastoma, lymphoma, and leukemia. Many pieces of evidence indicate a li... more and ovarian cancers, neuroblastoma, lymphoma, and leukemia. Many pieces of evidence indicate a link between HPR's antitumor effect and the metabolism of sphingolipids in tumor cells. As for many other anticancer drugs, the studies in tumor cell lines indicated that apoptosis is the major cytotoxic mechanism for HPR [even if the toxic effect of HPR is likely very complex and at least in part due to nonapoptotic mechanisms (2, 3)], and HPR-induced apoptosis in cancer cells has been ascribed to the increased cellular levels of ceramide, a sphingolipid mediator playing multiple roles in apoptotic signaling, elicited by HPR (4). The main metabolic mechanism responsible for HPR-induced production of ceramide is represented by de novo synthesis. Exposure to HPR of human neuroblastoma (5) and prostate cancer cells (6) resulted in a time-and dose-dependent increase in the activity of serine palmitoyltansferase and (dihydro)ceramide synthase, which catalyze early steps in the biosynthesis of ceramide and derived sphingolipids (7), and the treatment of cultured cells with pharmacological inhibitors of these enzymes was able to block HPR-induced ceramide increase (5, 6, 8). However, the effects of HPR on sphingolipid metabolism are probably much more complex and still poorly understood. For example, the possible role of sphingomyelin turnover due to the action of sphingomyelinases in the HPRelicited ceramide production is still controversial, and confl icting results have been reported (8, 9). In neuroblastoma Abstract The dihydroceramide, ceramide, sphingomyelin, lactosylceramide, and ganglioside species of A2780 human ovarian carcinoma cells treated with the synthetic retinoids N-(4-hydroxyphenyl)retinamide (fenretinide, 4-HPR) and 4-oxo-N-(4-hydroxyphenyl)retinamide (4-oxo-4-HPR) in culture were characterized by ESI-MS. We characterized 32 species of ceramide and dihydroceramide, 15 of sphingomyelin, 12 of lactosylceramide, 9 of ganglioside GM2, and 6 of ganglioside GM3 differing for the long-chain base and fatty acid structures. Our results indicated that treatment with both 4-HPR and 4-oxo-4-HPR led to a marked increase in dihydroceramide species, while only 4-oxo-4-HPR led to a minor increase of ceramide species. Dihydroceramides generated in A2780 cells in response to 4-HPR or 4-oxo-4-HPR differed for their fatty acid content, suggesting that the two drugs differentially affect the early steps of sphingolipid synthesis. Dihydroceramides produced upon treatments with the drugs were further used for the synthesis of complex dihydrosphingolipids, whose levels dramatically increased in drug-treated cells.

The Journal of Lipid Research, 2003

Treatment with methyl-␤-cyclodextrin (MCD) induced a time-and dose-dependent efflux of cholestero... more Treatment with methyl-␤-cyclodextrin (MCD) induced a time-and dose-dependent efflux of cholesterol, sphingolipids, and phosphatidylcholine (PC) from cerebellar neurons differentiated in culture. With a "mild" treatment, the loss of cell lipids induced a deep reorganization of the remaining membrane lipids. In fact, the amount of PC associated with a Triton X-100-insoluble membrane fraction (highly enriched in sphingolipids and cholesterol in nontreated cells) was lowered by the treatment. This suggested a reduction of the lipid domain area. However, the cholesterol and sphingolipid enrichment of this fraction remained substantially unchanged, suggesting the existence of dynamic processes aimed at preserving the segregation of cholesterol and sphingolipids in membrane domains. Under these conditions, the lipid membrane domains retained the ability to sort signaling proteins, such as Lyn and c-Src, but cells displayed deep alterations in their membrane permeability. However, normal membrane permeability was restored by loading cells with cholesterol. When MCD treatment was more stringent, a large loss of cell lipids occurred, and the lipid domains were much less enriched in cholesterol and lost the ability to sort specific proteins. The loss of the integrity and properties of lipid domains was accompanied by severe changes in the membrane permeability, distress, and eventually cell death.-Ottico, E., A.

Journal of Biological Chemistry, 2002

In the present work, we studied the effects of fenretinide (N-(4-hydroxyphenyl)retinamide (HPR)),... more In the present work, we studied the effects of fenretinide (N-(4-hydroxyphenyl)retinamide (HPR)), a hydroxyphenyl derivative of all-trans-retinoic acid, on sphingolipid metabolism and expression in human ovarian carcinoma A2780 cells. A2780 cells, which are sensitive to a pharmacologically achievable HPR concentration, become 10-fold more resistant after exposure to increasing HPR concentrations. Our results showed that HPR was able to induce a dose-and time-dependent increase in cellular ceramide levels in sensitive but not in resistant cells. This form of resistance in A2780 cells was not accompanied by the overexpression of multidrug resistance-specific proteins MDR1 P-glycoprotein and multidrug resistance-associated protein, whose mRNA levels did not differ in sensitive and resistant A2780 cells. HPR-resistant cells were characterized by an overall altered sphingolipid metabolism. The overall content in glycosphingolipids was similar in both cell types, but the expression of specific glycosphingolipids was different. Specifically, our findings indicated that glucosylceramide levels were similar in sensitive and resistant cells, but resistant cells were characterized by a 6-fold lower expression of lactosylceramide levels and by a 6-fold higher expression of ganglioside levels than sensitive cells. The main gangliosides from resistant A2780 cells were identified as GM3 and GM2. The possible metabolic mechanisms leading to this difference were investigated. Interestingly, the mRNA levels of glucosylceramide and lactosylceramide synthases were similar in sensitive and resistant cells, whereas GM3 synthase mRNA level and GM3 synthase activity were remarkably higher in resistant cells.

FEBS Letters, 2009

Human fibroblasts produce ceramide from sialyllactosylceramide on the plasma membranes. Sialidase... more Human fibroblasts produce ceramide from sialyllactosylceramide on the plasma membranes. Sialidase Neu3 is known to be plasma membrane associated, while only indirect data suggest the plasma membrane association of b-galactosidase and b-glucosidase. To determine the presence of b-galactosidase and b-glucosidase on plasma membrane, cells were submitted to cell surface biotinylation. Biotinylated proteins were purified by affinity column and analyzed for enzymatic activities on artificial substrates. Both enzyme activities were found associated with the cell surface and were up-regulated in Neu3 overexpressing cells. These enzymes were capable to act on both artificial and natural substrates without any addition of activator proteins or detergents and displayed a trans activity in living cells.

FEBS Letters, 2009

Caveolin-1, and probably also-2 and-3, can organize multimolecular membrane complexes involved in... more Caveolin-1, and probably also-2 and-3, can organize multimolecular membrane complexes involved in transmembrane traffic, cell adhesion and signal transduction. In this review, we discuss on the importance of caveolin membrane environment in regulating the architecture and function of such complexes, with a special emphasis on the role of sphingolipids.

Chemistry and Physics of Lipids, 1988

N-Glycolylneuraminic acid containing GM 1, GM l(NeuGc), was prepared by semisynthetic procedure. ... more N-Glycolylneuraminic acid containing GM 1, GM l(NeuGc), was prepared by semisynthetic procedure. The procedure makes use of GM 1 ganglioside deacetylated at the level of sialic acid residue (deAc-GM 1) and of 1,3-dioxalan-2,4-dione. DeAc-GM 1 is prepared from GM 1 by alkaline hydrolysis in the presence of tetramethylammonium hydroxide and the glycolylating compound by reaction of glycolic acid with phosgene in dioxane, followed by cyclization under vacuum. Mass spectrometric and nuclear magnetic resonance spectroscopy analyses clearly indicated the presence, in the neosynthesized ganglioside of a glycolic group in the sialic acid residue. Laser-light scattering measurements show that GM l(NeuGc) aggregates in aqueous media being present in solution as micelles with a molecular weight of 576,000 and a hydrodynamic radius of 62.4/~, as determined at 25°C. GM 1 (NeuGc) promotes neurite outgrowth in N-2a cells to a similar degree as GMI(NeuAc), but shows different behaviour under treatment with sialidase from Arthrobacter ureafaciens.

Biochemistry, 1989

A new procedure was used to synthesize a derivative of ganglioside GM1 containing a photoreactive... more A new procedure was used to synthesize a derivative of ganglioside GM1 containing a photoreactive nitrophenyl azide group at the end of the fatty acyl moiety, using deAc-deAcyl-GM1 obtained by deacetylation of the sialic acid and deacylation of the ceramide portion of GM1. This deAc-deAcyl-GM1 was first acylated at the long chain base amino group with 12-aminododecanoic acid, which has the amino group protected by a fluorenyl residue, and tritium labeled a t the sialic acid amino group with [3H]acetic anhydride of very high specific radioactivity. The fluorenyl group removed by ammonia treatment was