ஜர்னல் ஆஃப் கிளினிக்கல் & மெடிக்கல் ஜெனோமிக்ஸ்

IRE-1 Dependent Expression of Phosphoribosyl Pyrophosphate Synthetase Genes in U87 Glioma Cells: Effect of Glucose or Glutamine Deprivation

Abstract

Dmytro O Minchenko, Iana A Garmash, Yulia M Bashta, Ganna S Kustkova, Yulianna D Zalesna, Andreas Bikfalvi and Oleksandr H Minchenko

Nutrient deprivation conditions are capable to induce the endoplasmic reticulum stress and are responsible for regulation of the expression of numerous growth factors which control the cell proliferation and angiogenesis in malignant tumors, including glioma. The ERN1 mediated endoplasmic reticulum stress response-signalling pathway is tightly linked to the proliferation because the blockade of ERN1 function suppresses the tumor growth via specific changes in the cell transcriptome. Activation of the pentose phosphate pathway is an important factor of enhanced cell proliferation and tumor growthbecause it controls the synthesis of nucleotides and respectively nucleic acids. We studied the effect of blockade the ERN1 signaling enzyme function in glioma cells on the expression of phosphoribosyl pyrophosphate synthetase (PRPS), an important enzyme of pentose phosphate pathway, as well as its dependence of glucose and glutamine deprivation.

The expression of different genes of PRPS enzyme in glioma cells with complete suppression of ERN1 enzyme activity was measured by qPCR. For glucose and glutamine deprivation conditions the cells were exposurein the glucose or glutamine free medium for 16 hrs.

The expression of PRPS1 and PRPS2 genes as well as phosphoribosyl pyrophosphate synthetase associated protein 1(PRPSAP1) is significantly increased in U87 glioma cells with suppressed function of ERN1 gene, but the expression PRPSAP2 gene is decreased. It was also shown that glucose or glutamine deprivation leads to suppression of PRPS1 and PRPS2 gene expressions in U87 glioma cells; however, the blockade of ERN1 function in glioma cells modifies the effect of glutamine deprivation. Moreover, the expression of PRPSAP1 and PRPSAP2 genes was resistant to glucose deprivation condition in control glioma cells, but increased in glioma cells with ERN1 loss of function.

Results of this investigation demonstrated that the blockade of ERN1 signaling enzyme function affects the expression of genes encoding PRPS enzyme subunits in different ways and that dysregulation of the expression of important regulatory subunits of PRPS (PRPSAP1 and PRPSAP2) possibly changes the activity of this enzyme and participates in suppression of glioma growth via pentose phosphate pathway.