Phosphatidylinositol 3-KINASE

Active Ras and phosphatidylinositol-3-kinase-dependent pathways contribute to the malignant phenotype of glioblastoma multiformes (GBM). Here we show that the Ras inhibitor trans-farnesylthiosalicylic acid (FTS) exhibits profound antioncogenic effects in U87 GBM cells. FTS inhibited active Ras and attenuated Ras signaling to extracellular signal-regulated kinase, phosphatidylinositol-3-kinase, and Akt. Concomitantly, hypoxia-inducible factor 1alpha (HIF-1alpha) disappeared, expression of key glycolysis pathway enzymes and of other HIF-1alpha-regulated genes (including vascular endothelial growth factor and the Glut-1 glucose transporter) was down-regulated, and glycolysis was halted. This led to a dramatic reduction in ATP, resulting in a severe energy crisis. In addition, the expression of E2F-regulated genes was down-regulated in the FTS-treated cells. Consequently, U87 cell growth was arrested and the cells died. These results show that FTS is a potent down-regulator of HIF-1alpha and might therefore block invasiveness, survival, and angiogenesis in GBM.

In order to acquire fertilization competence, spermatozoa have to undergo biochemical changes in the female reproductive tract, known as capacitation. Signaling pathways that take place during the capacitation process are much investigated issue. However, the role and regulation of phosphatidylinositol 3-kinase (PI3K) in this process are still not clear. Previously, we reported that short-time activation of protein kinase A (PRKA, PKA) leads to PI3K activation and protein kinase Cα (PRKCA, PKCα) inhibition. In the present study, we found that during the capacitation PI3K phosphorylation/activation increases. PI3K activation was PRKA dependent, and down-regulated by PRKCA. PRKCA is found to be highly active at the beginning of the capacitation, conditions in which PI3K is not active. Moreover, inhibition of PRKCA causes significant activation of PI3K. Similar activation of PI3K is seen when the phosphatase PPP1 is blocked suggesting that PPP1 regulates PI3K activity. We found that du...

Pectolinarigenin (PEC), a natural flavonoid present in and in some species of fruits, has various pharmacological benefits such as anti-inflammatory and anti-cancer activities. In the present study, we investigated the anti-cancer mechanism of PEC induced cell death caused by autophagy and apoptosis in AGS and MKN28 human gastric cancer cells. The PEC treatment significantly inhibited the AGS and MKN28 cell growth in a dose-dependent manner. Further, PEC significantly elevated sub-G1 phase in AGS cells and G2/M phase cell cycle arrest in both AGS and MKN28 cells. Apoptosis was confirmed by Annexin V and Hoechst 33342 fluorescent staining. Moreover, Immunoblotting results revealed that PEC treatment down-regulated the inhibitor of apoptosis protein (IAP) family protein XIAP that leads to the activation of caspase-3 thereby cleavage of PARP (poly-ADP-ribose polymerase) in both AGS and MKN28 cells in a dose-dependent manner. The autophagy-inducing effect was indicated by the increased ...

The ataxia–telangiectasia mutated (ATM) gene codifies for a protein critically involved in the cellular response to DNA damage. ATM alterations have been observed in some sporadic lymphoproliferative disorders. The recurrent 11q22-23 deletions found in mantle cell lymphoma (MCL) suggest that ATM could be inactivated in these lymphomas. In this study, ATM gene alterations and protein expression were examined in 20 and 17 MCL tumor specimens, respectively. Previously, these patients had been examined forp53 and p14ARF gene status and analyzed by comparative genomic hybridization. Nine patients had 11q22-23 losses. Eight ATM gene mutations were detected in 7 patients. These alterations were 3 missense mutations in the phosphatidylinositol-3 kinase (PI-3K) domain and 5 truncating mutations, including 3 frameshifts, a nonsense mutation, and a substitution of the initial methionine. All truncating mutations were associated with lack of protein expression. Somatic origin was demonstrated i...

Phosphoinositides are a minor class of short-lived membrane phospholipids that serve crucial functions in cell physiology ranging from cell signalling and motility to their role as signposts of compartmental membrane identity. Phosphoinositide 4-phosphates such as phosphatidylinositol 4-phosphate (PI(4)P) and phosphatidylinositol 4,5-bisphosphate (PI(4,5)P2) are concentrated at the plasma membrane, on secretory organelles, and on lysosomes, whereas phosphoinositide 3-phosphates, most notably phosphatidylinositol 3-phosphate (PI(3)P), are a hallmark of the endosomal system. Directional membrane traffic between endosomal and secretory compartments, although inherently complex, therefore requires regulated phosphoinositide conversion. The molecular mechanism underlying this conversion of phosphoinositide identity during cargo exit from endosomes by exocytosis is unknown. Here we report that surface delivery of endosomal cargo requires hydrolysis of PI(3)P by the phosphatidylinositol 3-...

Porphyromonas gingivalis, an important periodontal pathogen, infects primary gingival epithelial cells (GECs). Despite the large number of bacteria that replicate inside the GECs, the host cell remains viable. We demonstrate that P. gingivalis triggers rapid and reversible surface phosphatidylserine exposure through a mechanism requiring caspase activation. However, after 1 day of infection, the bacteria no longer induce phosphatidylserine externalization and instead protect infected cells against apoptosis. Infection exerts its effect at the level of mitochondria, as P. gingivalis also blocks depolarization of the mitochondrial transmembrane potential and cytochrome c release. Interestingly, protein kinase B/Akt is phosphorylated during infection, which can be blocked with the phosphatidylinositol 3-kinase (PI3K) inhibitor LY294002. Suppression of the PI3K/Akt pathway following staurosporine treatment results in mitochondrial-membrane depolarization, cytochrome c release, DNA fragm...

Introduction: Experimental and clinical studies have shown that exercise training is one of the most effective strategies for reducing the progression of cardiomyopathy and decreasing the incidence of cardiovascular complications and mortality due to myocardial ischemia. This study aimed to investigate the role of high-intensity interval training (HIIT) in the expression of Hand2 and Phosphatidylinositol-3-kinase (PI3K) genes in cardiac ischemia rats.

Materials & Methods: In this study, 28 male Wistar rats (200-250 g) were randomly divided into four groups of sham, ischemia, exercise, and exercise-ischemia. Myocardial infarction was performed by the closure of the left anterior descending artery for 30 min. In total, 40-min HIIT (each interval consisted of 4-min very high intensity running with approximately 85% to 90% maximum rate of oxygen consumption [VO2max] followed by 2-min active recovery with approximately 50% to 60% VO2max) were performed three days a week for eight weeks.
Ethics code: IR.SSRI.REC.1396.134

Findings: The results showed that the expression level of the Hand2 gene in the ischemia-training group was significantly increased, compared to the sham (P=0.001) and ischemia (P=0.001) groups. Furthermore, the concentration of PI3K in the exercise and exercise-ischemia groups was significantly increased, compared to the sham (P=0.001) and ischemia (P=0.001) groups. However, there was a decrease in the ischemia group, compared to the other groups (P<0.05).

Discussions & Conclusions: The findings of the present study showed that HIIT leads to increased expression of the Hand2 gene and PI3K. Furthermore, the HIIT results in physiological hypertrophy. On the other hand, the pathological hypertrophy of these variables is reduced in this study.

Integrin α2β1–mediated adhesion of human platelets to monomeric type I collagen or to the GFOGER peptide caused a time-dependent activation of PI3K and Akt phosphorylation. This process was abrogated by pharmacologic inhibition of PI3Kβ, but not of PI3Kγ or PI3Kα. Moreover, Akt phosphorylation was undetectable in murine platelets expressing a kinase-dead mutant of PI3Kβ (PI3KβKD), but occurred normally in PI3KγKD platelets. Integrin α2β1 failed to stimulate PI3Kβ in platelets from phospholipase Cγ2 (PLCγ2)–knockout mice, and we found that intracellular Ca2+ linked PLCγ2 to PI3Kβ activation. Integrin α2β1 also caused a time-dependent stimulation of the focal kinase Pyk2 downstream of PLCγ2 and intracellular Ca2+. Whereas activation of Pyk2 occurred normally in PI3KβKD platelets, stimulation of PI3Kβ was strongly reduced in Pyk2-knockout mice. Neither Pyk2 nor PI3Kβ was required for α2β1–mediated adhesion and spreading. However, activation of Rap1b and inside-out stimulation of integr...

HER2 (erbB2/neu) is a member of the erbB family of receptor tyrosine kinases and is involved in regulating the growth of several types of human carcinomas. HER2 represents a successful therapeutic target of the biotechnology era as exemplified by the drug Herceptin (trastuzumab), which has clinical activity in a subset of breast cancer patients. Using DNA microarrays, we identified a cohort of genes that are differentially regulated by HER2 in breast epithelial cells. One of the HER2-regulated genes discovered was fatty acid synthase (FAS), which has been shown to be overexpressed in breast cancer as well as other cancers. FAS is implicated in tumorigenesis through its role in cell proliferation and membrane lipid incorporation of neoplastic cells. Here, we demonstrate that HER2-mediated induction of FAS is inhibitable by Herceptin and tyrosine kinase inhibitors of HER2. Through a phosphatidylinositol 3&#39;-kinase-dependent pathway, HER2 stimulates the FAS promoter and ultimately m...

The transition from embryonic to vegetative growth marks an important developmental stage in the plant life cycle. The turnip (tnp) mutant was identified in a screen for modifiers of POLARIS expression, a gene required for normal root growth. Mapping and molecular ...

Endothelial connexin (Cx)40 plays an important role in signal propagation along blood vessel walls, modulating vessel diameter and thereby blood flow. Blood flow, in turn, has been shown to alter endothelial Cx40 expression. However, the timing and shear stress dependence of this relationship have remained unclear, as have the signal transduction pathways involved and the functional implications. Therefore, the aim of this study was to quantify the effects of shear stress on endothelial Cx40 expression, to analyze the role of phosphoinositide 3-kinase (PI3K)/Akt signaling involved, and to assess the possible functional consequences for the adaptation of microvascular networks. First-passage human umbilical vein endothelial cells were exposed to defined shear stress conditions and analyzed for Cx40 using real-time RT-PCR and immunoblot analysis. Shear stress caused long-term induction of Cx40 protein expression, with two short-term mRNA peaks at 4 and 16 h, indicating the dynamic nat...