RESUMO
We have studied the effect of hypoxia on the expression level of mRNA of the basic enzymes of pentose-phosphate cycle (G6PD, TKT, TALDO1, PGLS and RPIA) and glucose-6-phosphate isomerase (GPI) in U87 glioma cells in relation to inhibition of IRE1 (inositol requiring enzyme 1). It was shown that hypoxia leads to up-regulation of the expression of GPI and PGLS genes and to down-regulation of TALDO1 and RPIA genes in control glioma cells. Changes for GPI gene were more significant than for other genes. At the same time, inhibition of IRE1 modified the effect of hypoxia on the expression of all studied genes. In particular, it increased sensitivity to hypoxia of G6PD and TKT genes expression and suppressed the effect of hypoxia on the expression of GPI and RPIA genes. Additionally, inhibition of IRE1 eliminated hypoxic regulation of PGLS gene and did not change significantly effect of hypoxia on the expression of TALDO1 gene in glioma cells. Present study demonstrated that hypoxia, which often contributes to tumor growth, affects the expression of most studied genes and inhibition of IRE1 modified the hypoxic regulation of pentose-phosphate cycle gene expressions in a gene specific manner and thus possibly contributes to slower glioma growth, but several aspects of this regulation warrant further investigation.
Assuntos
Estresse do Retículo Endoplasmático/genética , Endorribonucleases/genética , Regulação Neoplásica da Expressão Gênica , Neuroglia/metabolismo , Via de Pentose Fosfato/genética , Proteínas Serina-Treonina Quinases/genética , Aldose-Cetose Isomerases/genética , Aldose-Cetose Isomerases/metabolismo , Hidrolases de Éster Carboxílico/genética , Hidrolases de Éster Carboxílico/metabolismo , Hipóxia Celular , Linhagem Celular Tumoral , Movimento Celular , Proliferação de Células , Endorribonucleases/deficiência , Técnicas de Silenciamento de Genes , Glucose-6-Fosfato Isomerase/genética , Glucose-6-Fosfato Isomerase/metabolismo , Glucosefosfato Desidrogenase/genética , Glucosefosfato Desidrogenase/metabolismo , Humanos , Neuroglia/patologia , Proteínas Serina-Treonina Quinases/deficiência , Transdução de Sinais , Transaldolase/genética , Transaldolase/metabolismo , Transcetolase/genética , Transcetolase/metabolismoRESUMO
Activation of pentose phosphate pathway is an important factor of enhanced cell proliferation and tumor growth. Phosphoribosyl pyrophosphate synthetase (PRPS) is a key enzyme of this pathway and plays a central role in the synthesis of purines and pyrimidines. Hypoxia as well as ERN1 (from endoplasmic reticulum to nuclei-1) mediated endoplasmic reticulum stress response-signalling pathway is linked to the proliferation because the blockade of ERN1 suppresses tumor growth, including glioma. We studied the expression of different PRPS genes in glioma cells with ERN1 knockdown under hypoxic condition. It was shown that hypoxia decreases the expression of PRPS1 and PRPS2 genes in both types of glioma cells, being more pronounced in cells without ERN1 function, but PRPSAP1 and PRPSAP2 gene expressions are suppressed by hypoxia only in glioma cells with blockade of ERN1. Moreover, the blockade of endoribonuclease activity of ERN1 does not affect the expression of PRPS1 and PRPS2 as well as PPRS-associated protein genes in U87 glioma cells. At the same time, the induction of endoplasmic reticulum stress by tunicamycin in glioma cells with suppressed activity of ERN1 endoribonuclease decreases the expression level of PRPS1 and PRPS2 genes only. Results of this investigation clearly demonstrated that the expression of different genes encoding subunits of PRPS enzyme is affected by hypoxia in U87 glioma cells, but the effect of hypoxia is modified by suppression of endoplasmic reticulum stress signaling enzyme ERN1.