The expression levels of PI3K and phospho-AKT in PTEN-mutated cells were much higher than in DK-MG and GaMG cells, which can be associated with the lack of PTEN in these cells leading to a compensatory activation of the PI3K pathway. mechanisms responsible for the excessive membrane folding and microvilli expression in GBM cells remain unclear. To address this issue, we explore in the present study the plasma membrane morphology in five GBM lines differing in the mutational status of and SE m describes the ratio of the actual cell membrane surface area to that of a smooth sphere of the same TAK-659 hydrochloride radius. From the in Figure 2), thus yielding the values for the peak frequencies (and e is expected (Eq. 2) and is found in all cell lines (Figure 3). The data of each cell line were fitted to Eq. 2 to calculate the mean area-specific membrane capacitance the external conductivity e.The measurements were performed in isotonic 300-mOsm inositol medium. The Discussion). In isotonic medium, the 5 GBM lines exhibited very different IGLC1 in all GBM cells and also a large variation of this parameter among tested cell lines (2.38 5.25). Particularly, TAK-659 hydrochloride the values larger than 3 obtained here for cell lines with mutant or status, or both, are clearly at the upper edge of the range measured in 60 tumor cell lines by dielectrophoresis [19]. For comparison, we also analyzed the plasma membrane folding in two non-malignant human cell lines, including the human embryonic kidney HEK293 line and the human fibroblast cell line HFIB-1 (both are adherently growing cell lines). As evident from the Fig. S3, the mean and show best least-square fits of the Lcio-model [50] to the data. The fitted parameters ( SE m SE was determined by video microscopy from the cross-sections of cells, such as shown in Figures 4A and 4D. The osmotically inactive volume fraction was determined from the Boyle vant Hoff plots (Figure S4). The osmotic water permeability cells (RHS column) in 100-mOsm sucrose solution (Figure 5A). The data in Figures 4 and ?and55 reveal a marked difference between sucrose and inositol in their effects on the secondary volume response in all tested cell lines. After the initial swelling in hypotonic sucrose solutions, all GBM lines underwent regulatory volume decrease (RVD). During RVD, the cells shrank gradually despite persisting hypotonicity. RVD relies on the release of cytosolic solutes (including both inorganic ions and small organic osmolytes) through swelling-activated membrane pathways [37], [46]. In agreement with our findings presented here (Figure 5) and previously [47], other glioma cells (including the D54-MG line and primary glioma cells from patient biopsies) are able to readjust their volume in anisotonic media [48]. In sharp contrast to the disaccharide sucrose, the small organic osmolyte inositol not only completely abolished RVD, e.g. in case of DK-MG cells, but also caused noticeable secondary swelling of GaMG and SNB19 cells (Figures 5B and 5D). As shown elsewhere [37], [46], the different cell volume responses to hypotonic inositol and sucrose solutions arise from the size selectivity of swelling-activated membrane pathways, conducting inositol but not sucrose. Mammalian cells ubiquitously express swelling-activated pathways for small organic osmolytes, such TAK-659 hydrochloride as sorbitol, inositol, amino acids etc. [37], [49]. Under our experimental conditions, the influx of extracellular inositol into cells abolished RVD by compensating for the release of intracellular solutes. Unlike inositol, the disaccharide sucrose did not permeate the plasma membrane of GBM cells, as evidenced by the ability to RVD over the entire hypotonicity range (Figures 5A and 5B). The presence of RVD allowed us to quantitatively analyze the membrane transport properties in terms of the osmotic water and swelling-activated solute permeabilities (lipogenesis and membrane synthesis. In a previous study [21], elevated levels of FAS protein have been found in various GBM lines and human glioma tissue samples. Figure 6 shows exemplarily the Western blot data of cell samples probed for p53, MDM2, PTEN, PI3K (p110), phospho-AKT, phospho-mTOR, and FAS. Open in a separate window Figure 6 Representative Western blot analysis of the expression of p53, MDM2, PTEN, PI3K, phospho-AKT, phospho-mTOR and FAS proteins.For each cell line, cell lysates were prepared from exponentially TAK-659 hydrochloride growing cells, 20C24 h after splitting the culture. Each protein band was normalized to the intensity of -actin used as loading control, and.