The effect of two newly Chinese presenilin-1 mutations on the sensitivity to trophic factor withdrawal in human neuroblastoma cells

Abstract

To study the effects of two novel presenilin-1 (PS1) mutations, V97L and A136G, discovered in 2 families of Alzheimer's disease (AD) in China, on human neuroblastoma cells and the protective role of insulin-like growth factor-1 (IGF-1). Two mutation type (MT) PS-1 genes with the mutational sites V97L and A136G were established. These 2 MT genes, wild type (WT) PS-1 gene, and mock were stably transfected into the human neuroblastoma cells of the line SH-SY5Y. The 4 kinds of transfected cells were divided into 3 subgroups: (1) control subgroup, cultured in normal medium with serum, (2) serum deprivation subgroup, cultured in the medium without serum, and (3) serum deprivation + IGF-1 subgroup, cultured in serum deprivation medium plus IGF-1. Twenty-four hours later MTT colorimetry was used to calculate the cell survival rate. Hoechst33258 method and phosphatidylinositol/annexin V-FITC double staining flow cytometry were used to observe the cell apoptosis. The glucose uptake was measured. Western blotting was used to analyze the protein expression of glucose transporter protein (GLUT)-1 in the cell membrane. Different tests all showed that the cell survival rates of the V97L and A136G serum deprivation subgroups were both significantly lower than those of the corresponding WT and Mock subgroups (P < 0.01, P < 0.05), the cell survival rates of the all serum deprivation + IGF-1 subgroups were significantly higher than those of the corresponding serum deprivation subgroups (all P < 0.01); The glucose uptake rate was not significantly different among different subgroups, but IGF-1 addition made the glucose uptake increase by about 25% (all P > 0.05). The GLUT1 expression in the cell membrane of the serum deprivation + IGF-I subgroups increased by 15% - 20% respectively, however, without significant differences. Enhanced sensitivity to trophic withdrawal in the cells with the two Chinese PS1 mutations most likely contributes to the neuron loss in AD. The sensitivity to apoptosis is not caused by impaired glucose metabolism, but IGF-1 still can protect cells from serum deprivation that compensates the negative effect through enhancing glucose transport and mitochondria activities.