RESUMO
A theoretical study to elucidate the mechanistic aspects involved in the tosylation-cyclization reaction of diastereomeric phytosphingosines 1a-1d to jaspines 4a-4d is presented. The stereochemistry of the starting stereoisomers is crucial for the development of weak interactions, both in the reactants and in the transition states. The analysis of the energy barriers of each elementary reaction is consistent with the observed reluctance of tosylate 2d to undergo cyclization. In addition, the initial tosylation can be identified as the limiting step in cyclizations from la and 1b.
Assuntos
Compostos Bicíclicos Heterocíclicos com Pontes/síntese química , Toxinas Marinhas/síntese química , Esfingosina/análogos & derivados , Compostos Bicíclicos Heterocíclicos com Pontes/química , Ciclização , Toxinas Marinhas/química , Modelos Moleculares , Estrutura Molecular , Esfingosina/químicaRESUMO
Recent evidence suggests that sphingosine 1-phosphate (S1P) regulates self-renewal of human embryonic stem (ES) cells and differentiation of mouse embryoid bodies (derived from mouse ES cells) to cardiomyocytes. We have investigated the role of S1P in regulating ERK-1/2 signaling in mouse ES cells. In this regard, we found that both mouse ES-D3 and CGR8 cells express S1P(1), S1P(2), S1P(3), and S1P(5) but lack S1P(4). The treatment of ES cells with S1P induced the activation of ERK-1/2 via a mechanism that was not mediated by S1P(1), S1P(2), or S1P(3). This was based on: (i) the failure of S1P(1), S1P(2), or S1P(3) antagonists to inhibit S1P-stimulated ERK-1/2 activation and (ii) the failure of SEW 2871 (S1P(1) receptor agonist) to stimulate ERK-1/2 activation. The treatment of ES cells with phytosphingosine 1-phosphate (phyto-S1P), which we show here is an agonist of the S1P(5) receptor, stimulated ERK-1/2 activation. These findings therefore suggest that S1P(5) may mediate the effects of S1P in terms of regulating ERK-1/2 signaling in ES cells. The S1P-dependent activation of ERK-1/2 was sensitive to inhibition by pertussis toxin (uncouples the G-protein, G(i) from GPCR), bisindolylmaleimide I (PKC inhibitor), and PP2 (c-Src inhibitor), but was not reduced by LY29004 (PI3K inhibitor) suggesting that S1P uses G(i)-, PKC-, and c-Src-dependent mechanisms to activate the ERK-1/2 pathway in ES cells.
Assuntos
Células-Tronco Embrionárias/efeitos dos fármacos , Lisofosfolipídeos/farmacologia , Proteína Quinase 1 Ativada por Mitógeno/metabolismo , Proteína Quinase 3 Ativada por Mitógeno/metabolismo , Esfingosina/análogos & derivados , Animais , Western Blotting , Células CHO , Linhagem Celular , Linhagem Celular Tumoral , Cricetinae , Cricetulus , DNA/biossíntese , Células-Tronco Embrionárias/citologia , Células-Tronco Embrionárias/metabolismo , Ativação Enzimática/efeitos dos fármacos , Expressão Gênica , Humanos , Camundongos , Fator de Crescimento Derivado de Plaquetas/farmacologia , Proteína Quinase C/metabolismo , Proteínas Proto-Oncogênicas pp60(c-src)/metabolismo , Receptores de Lisoesfingolipídeo/genética , Receptores de Lisoesfingolipídeo/metabolismo , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Esfingosina/farmacologiaRESUMO
The synthesis of isomeric jaspines (anhydro phytosphingosines), arising from intramolecular cyclization of the corresponding phytosphingosines with different configurations at C3 and C4 positions of the sphingoid backbone, is reported. Natural jaspine B is the most cytotoxic isomer on A549 cells and it induces cell death in a dose-dependent manner. The cytotoxicity of jaspine B has been correlated with a significant increase of intracellular dihydroceramides, which seem to play an active role in autophagy.
Assuntos
Esfingosina/análogos & derivados , Autofagia , Morte Celular/efeitos dos fármacos , Linhagem Celular , Ceramidas/metabolismo , Ciclização , Relação Dose-Resposta a Droga , Humanos , Esfingosina/síntese química , Esfingosina/química , Esfingosina/farmacologia , EstereoisomerismoRESUMO
A library of 64 phytosphingolipid analogues resulting from the systematic variation of the C1, C3, C4, and the N-acyl moiety of phytosphingosine (PHS) has been prepared from common scaffolds derived from the chiral pool and Sharpless asymmetric dihydroxylation reactions. Library members have been evaluated as growth inhibitors of the yeast Saccaromyces cerevisiae. In addition, 1-amino-N-pivaloyl PHS analogues were also tested as IPC synthase inhibitors, in comparison with the natural product khafrefungin.
