scholarly journals A Genomewide Overexpression Screen Identifies Genes Involved in the Phosphatidylinositol 3-Kinase Pathway in the Human Protozoan Parasite Entamoeba histolytica

2014 ◽  
Vol 13 (3) ◽  
pp. 401-411 ◽  
Author(s):  
Amrita B. Koushik ◽  
Brenda H. Welter ◽  
Michelle L. Rock ◽  
Lesly A. Temesvari
Keyword(s):  
Entamoeba Histolytica ◽  
Mutant Cell ◽  
Lethal Dose ◽  
Protozoan Parasite ◽  
Pi3k Pathway ◽  
Forward Genetics ◽  
Pi3k Inhibitor ◽  
Phosphatidylinositol 3 Kinase ◽  
Content Type ◽  
Phosphatidylinositol 3

ABSTRACTEntamoeba histolyticais a protozoan parasite that causes amoebic dysentery and liver abscess.E. histolyticarelies on motility, phagocytosis, host cell adhesion, and proteolysis of extracellular matrix for virulence. In eukaryotic cells, these processes are mediated in part by phosphatidylinositol 3-kinase (PI3K) signaling. Thus, PI3K may be critical for virulence. We utilized a functional genomics approach to identify genes whose products may operate in the PI3K pathway inE. histolytica. We treated a population of trophozoites that were overexpressing genes from a cDNA library with a near-lethal dose of the PI3K inhibitor wortmannin. This screen was based on the rationale that survivors would be overexpressing gene products that directly or indirectly function in the PI3K pathway. We sequenced the overexpressed genes in survivors and identified a cDNA encoding a Rap GTPase, a protein previously shown to participate in the PI3K pathway. This supports the validity of our approach. Genes encoding a coactosin-like protein, EhCoactosin, and a serine-richE. histolyticaprotein (SREHP) were also identified. Cells overexpressing EhCoactosin or SREHP were also less sensitive to a second PI3K inhibitor, LY294002. This corroborates the link between these proteins and PI3K. Finally, a mutant cell line with an increased level of phosphatidylinositol (3,4,5)-triphosphate, the product of PI3K activity, exhibited increased expression of SREHP and EhCoactosin. This further supports the functional connection between these proteins and PI3K inE. histolytica. To our knowledge, this is the first forward-genetics screen adapted to reveal genes participating in a signal transduction pathway in this pathogen.

scholarly journals Localization and Targeting of an Unusual Pyridine Nucleotide Transhydrogenase in Entamoeba histolytica

2010 ◽  
Vol 9 (6) ◽  
pp. 926-933 ◽  
Author(s):  
Mohammad Abu Yousuf ◽  
Fumika Mi-ichi ◽  
Kumiko Nakada-Tsukui ◽  
Tomoyoshi Nozaki
Keyword(s):  
Entamoeba Histolytica ◽  
Fluorescent Protein ◽  
Physiological Role ◽  
Protozoan Parasite ◽  
Pyridine Nucleotide ◽  
Immunofluorescence Assay ◽  
Chemical Degradation ◽  
Content Type ◽  
Targeting Signal ◽  
Pyridine Nucleotide Transhydrogenase

ABSTRACT Pyridine nucleotide transhydrogenase (PNT) catalyzes the direct transfer of a hydride-ion equivalent between NAD(H) and NADP(H) in bacteria and the mitochondria of eukaryotes. PNT was previously postulated to be localized to the highly divergent mitochondrion-related organelle, the mitosome, in the anaerobic/microaerophilic protozoan parasite Entamoeba histolytica based on the potential mitochondrion-targeting signal. However, our previous proteomic study of isolated phagosomes suggested that PNT is localized to organelles other than mitosomes. An immunofluorescence assay using anti-E. histolytica PNT (EhPNT) antibody raised against the NADH-binding domain showed a distribution to the membrane of numerous vesicles/vacuoles, including lysosomes and phagosomes. The domain(s) required for the trafficking of PNT to vesicles/vacuoles was examined by using amoeba transformants expressing a series of carboxyl-terminally truncated PNTs fused with green fluorescent protein or a hemagglutinin tag. All truncated PNTs failed to reach vesicles/vacuoles and were retained in the endoplasmic reticulum. These data indicate that the putative targeting signal is not sufficient for the trafficking of PNT to the vesicular/vacuolar compartments and that full-length PNT is necessary for correct transport. PNT displayed a smear of >120 kDa on SDS-PAGE gels. PNGase F and tunicamycin treatment, chemical degradation of carbohydrates, and heat treatment of PNT suggested that the apparent aberrant mobility of PNT is likely attributable to its hydrophobic nature. PNT that is compartmentalized to the acidic compartments is unprecedented in eukaryotes and may possess a unique physiological role in E. histolytica.

scholarly journals Role of Phosphatidylinositol-3-Kinase Pathway in Head and Neck Squamous Cell Carcinoma

2012 ◽  
Vol 2012 ◽  
pp. 1-12 ◽  
Author(s):  
Li Du ◽  
Jingping Shen ◽  
Andrew Weems ◽  
Shi-Long Lu
Keyword(s):  
Squamous Cell Carcinoma ◽  
Cell Carcinoma ◽  
Head And Neck ◽  
Squamous Cell ◽  
Pi3k Pathway ◽  
Neck Squamous Cell Carcinoma ◽  
Phosphatidylinositol 3 Kinase ◽  
Molecular Alterations ◽  
Future Direction ◽  
Phosphatidylinositol 3

Activation of the phosphatidylinositol-3-kinase (PI3K) pathway is one of the most frequently observed molecular alterations in many human malignancies, including head and neck squamous cell carcinoma (HNSCC). A growing body of evidence demonstrates the prime importance of the PI3K pathway at each stage of tumorigenesis, that is, tumor initiation, progression, recurrence, and metastasis. Expectedly, targeting the PI3K pathway yields some promising results in both preclinical studies and clinical trials for certain cancer patients. However, there are still many questions that need to be answered, given the complexity of this pathway and the existence of its multiple feedback loops and interactions with other signaling pathways. In this paper, we will summarize recent advances in the understanding of the PI3K pathway role in human malignancies, with an emphasis on HNSCC, and discuss the clinical applications and future direction of this field.

scholarly journals Hypothalamic Phosphatidylinositol 3-Kinase Pathway of Leptin Signaling Is Impaired during the Development of Diet-Induced Obesity in FVB/N Mice

Endocrinology ◽  
2007 ◽  
Vol 149 (3) ◽  
pp. 1121-1128 ◽  
Author(s):  
Anantha S. Metlakunta ◽  
Maitrayee Sahu ◽  
Abhiram Sahu
Keyword(s):  
Energy Homeostasis ◽  
Early Period ◽  
Pi3k Pathway ◽  
Leptin Resistance ◽  
Phosphatidylinositol 3 Kinase ◽  
Leptin Signaling ◽  
Diet Induced Obesity ◽  
Pi3k Activity ◽  
Central Leptin Resistance ◽  
Phosphatidylinositol 3

Phosphatidylinositol 3-kinase (PI3K) pathway of leptin signaling plays an important role in transducing leptin action in the hypothalamus. Obesity is usually associated with resistance to the effect of leptin on food intake and energy homeostasis. Although central leptin resistance is thought to be involved in the development of diet-induced obesity (DIO), the mechanism behind this phenomenon is not clearly understood. To determine whether DIO impairs the effect of leptin on hypothalamic PI3K signaling, we fed 4-wk-old FVB/N mice a high-fat diet (HFD) or low-fat diet (LFD) for 19 wk. HFD-fed mice developed DIO in association with hyperleptinemia, hyperinsulinemia, and impaired glucose and insulin tolerance. Leptin (ip) significantly increased hypothalamic PI3K activity and phosphorylated signal transducer and activator of transcription 3 (p-STAT3) levels in LFD-fed mice but not in DIO mice. Immunocytochemical study confirmed impaired p-STAT3 activation in various hypothalamic areas, including the arcuate nucleus. We next tested whether both PI3K and STAT3 pathways of leptin signaling were impaired during the early period of DIO. Leptin failed to increase PI3K activity in DIO mice that were on a HFD for 4 wk. However, leptin-induced p-STAT3 activation in the hypothalamus measured by Western blotting and immunocytochemistry remained comparable between LFD- and HFD-fed mice. These results suggest that the PI3K pathway but not the STAT3 pathway of leptin signaling is impaired during the development of DIO in FVB/N mice. Thus, a defective PI3K pathway of leptin signaling in the hypothalamus may be one of the mechanisms of central leptin resistance and DIO.

Phosphatidylinositol 3′-kinase signaling pathway is essential for Rac1-induced hypoxia-inducible factor-1α and vascular endothelial growth factor expression

2011 ◽  
Vol 300 (6) ◽  
pp. H2169-H2176 ◽  
Author(s):  
Yan Xue ◽  
Nan-Lin Li ◽  
Jing-Yue Yang ◽  
Yan Chen ◽  
Lu-Lu Yang ◽  
...  
Keyword(s):  
Signal Transduction ◽  
Tumor Suppressor ◽  
Active Form ◽  
Hypoxia Inducible Factor ◽  
Pi3k Pathway ◽  
Rho Proteins ◽  
Phosphatidylinositol 3 Kinase ◽  
Von Hippel Lindau ◽  
Phosphatidylinositol 3

We have previously demonstrated the roles of RhoA, Rac1, and Cdc42 in hypoxia-driven angiogenesis. However, the role of oncogenes in hypoxia signaling is poorly understood. Given the importance of Rho proteins in the hypoxic response, we hypothesized that Rho family members could act as mediators of hypoxic signal transduction. We investigated the cross-talk between hypoxia and oncogene-driven signal transduction pathways and explored the role of Rac1 on hypoxia-induced hypoxia-inducible factor (HIF)-1α and VEGF expression. Since the phosphatidylinositol 3′-kinase (PI3K) pathway is involved in signal transduction of many oncogenes, we explored the role of PI3K on Rac1-mediated expression of HIF-1α and VEGF in hypoxia. We showed that LY-294002, a PI3K inhibitor, suppressed HIF-1α and VEGF induction under hypoxic conditions by up to 50%. Activation of Rac1 resulted in an upregulation of hypoxia-induced HIF-1α expression, which was blocked by LY-294002. These data suggested that Rac1 is an intermediate in the PI3K-mediated induction of HIF-1α. Interestingly, there was a significant downregulation of the tumor suppressor genes p53 and von Hippel-Lindau tumor suppressor (VHL) in cells expressing a constitutively active form of Rac1. Rac1-mediated inhibition of p53 and VHL could therefore be implicated in the upregulation of HIF-1α expression.

scholarly journals Idelalisib in the management of lymphoma

Blood ◽  
2016 ◽  
Vol 128 (3) ◽  
pp. 331-336 ◽  
Author(s):  
Chan Yoon Cheah ◽  
Nathan H. Fowler
Keyword(s):  
Clinical Experience ◽  
Small Molecule ◽  
Therapeutic Strategy ◽  
Pi3k Pathway ◽  
Phosphatidylinositol 3 Kinase ◽  
Mechanisms Of Resistance ◽  
Preclinical Data ◽  
Combination Strategies ◽  
Orally Bioavailable ◽  
Phosphatidylinositol 3

Abstract Inhibition of the phosphatidylinositol-3-kinase (PI3K) pathway as an anticancer therapeutic strategy was realized with the approval of the orally bioavailable small molecule PI3Kδ inhibitor idelalisib. In this focused review, we highlight the rationale for targeting the pathway in lymphomas, provide a brief summary of the preclinical data, and describe the clinical experience with this agent in patients with lymphoma. We describe some of the idiosyncratic toxicities of this agent, some of the mechanisms of resistance, and some of the ongoing combination strategies.

Effects of rifampin on the pharmacokinetics of copanlisib, a novel pan-class I phosphatidylinositol-3-kinase (PI3K) inhibitor in cancer patients.

2018 ◽  
Vol 36 (15_suppl) ◽  
pp. e14559-e14559
Author(s):  
Anna Spreafico ◽  
Michael B. Sawyer ◽  
Lillian L. Siu ◽  
Funan Huang ◽  
Susanne Reschke ◽  
...  
Keyword(s):  
Cancer Patients ◽  
Pi3k Inhibitor ◽  
Class I ◽  
Phosphatidylinositol 3 Kinase ◽  
Phosphatidylinositol 3
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