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Dive into the research topics where Javad Torabinejad is active.

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Featured researches published by Javad Torabinejad.


Plant Physiology | 2005

Mutations in the arabidopsis phosphoinositide phosphatase gene SAC9 lead to overaccumulation of PtdIns(4,5)P2 and constitutive expression of the stress-response pathway

Mary E. Williams; Javad Torabinejad; Evan Cohick; Katherine Parker; Elizabeth J. Drake; James E. Thompson; Michelle Hortter; Daryll B. DeWald

Phosphoinositides (PIs) are signaling molecules that regulate cellular events including vesicle targeting and interactions between membrane and cytoskeleton. Phosphatidylinositol (PtdIns)(4,5)P2 is one of the best characterized PIs; studies in which PtdIns(4,5)P2 localization or concentration is altered lead to defects in the actin cytoskeleton and exocytosis. PtdIns(4,5)P2 and its derivative Ins(1,4,5)P3 accumulate in salt, cold, and osmotically stressed plants. PtdIns(4,5)P2 signaling is terminated through the action of inositol polyphosphate phosphatases and PI phosphatases including supressor of actin mutation (SAC) domain phosphatases. In some cases, these phosphatases also act on Ins(1,4,5)P3. We have characterized the Arabidopsis (Arabidopsis thaliana) sac9 mutants. The SAC9 protein is different from other SAC domain proteins in several ways including the presence of a WW protein interaction domain within the SAC domain. The rice (Oryza sativa) and Arabidopsis SAC9 protein sequences are similar, but no apparent homologs are found in nonplant genomes. High-performance liquid chromatography studies show that unstressed sac9 mutants accumulate elevated levels of PtdIns(4,5)P2 and Ins(1,4,5)P3 as compared to wild-type plants. The sac9 mutants have characteristics of a constitutive stress response, including dwarfism, closed stomata, and anthocyanin accumulation, and they overexpress stress-induced genes and overaccumulate reactive-oxygen species. These results suggest that the SAC9 phosphatase is involved in modulating phosphoinsitide signals during the stress response.


Plant Physiology | 2009

VTC4 is a bifunctional enzyme that affects myoinositol and ascorbate biosynthesis in plants.

Javad Torabinejad; Janet L. Donahue; Bhadra N. Gunesekera; Matthew J. Allen-Daniels; Glenda E. Gillaspy

Myoinositol synthesis and catabolism are crucial in many multiceullar eukaryotes for the production of phosphatidylinositol signaling molecules, glycerophosphoinositide membrane anchors, cell wall pectic noncellulosic polysaccharides, and several other molecules including ascorbate. Myoinositol monophosphatase (IMP) is a major enzyme required for the synthesis of myoinositol and the breakdown of myoinositol (1,4,5)trisphosphate, a potent second messenger involved in many biological activities. It has been shown that the VTC4 enzyme from kiwifruit (Actinidia deliciosa) has similarity to IMP and can hydrolyze l-galactose 1-phosphate (l-Gal 1-P), suggesting that this enzyme may be bifunctional and linked with two potential pathways of plant ascorbate synthesis. We describe here the kinetic comparison of the Arabidopsis (Arabidopsis thaliana) recombinant VTC4 with d-myoinositol 3-phosphate (d-Ins 3-P) and l-Gal 1-P. Purified VTC4 has only a small difference in the Vmax/Km for l-Gal 1-P as compared with d-Ins 3-P and can utilize other related substrates. Inhibition by either Ca2+ or Li+, known to disrupt cell signaling, was the same with both l-Gal 1-P and d-Ins 3-P. To determine whether the VTC4 gene impacts myoinositol synthesis in Arabidopsis, we isolated T-DNA knockout lines of VTC4 that exhibit small perturbations in abscisic acid, salt, and cold responses. Analysis of metabolite levels in vtc4 mutants showed that less myoinositol and ascorbate accumulate in these mutants. Therefore, VTC4 is a bifunctional enzyme that impacts both myoinositol and ascorbate synthesis pathways.


Journal of Histochemistry and Cytochemistry | 2002

A Monoclonal Antibody to Visualize PtdIns(3,4,5)P3 in Cells

Riyan Chen; Veronica Kang; Jian Chen; Joseph C. Shope; Javad Torabinejad; Daryll B. DeWald; Glenn D. Prestwich

Phosphatidylinositol 3,4,5-trisphosphate [PtdIns(3,4,5)P3] is a second messenger produced in response to agonist stimulation. Traditionally, visualization of phosphoinositide polyphosphates (PtdInsPn) in living cells is accomplished using chimeric green fluorescent protein (GFP)-pleckstrin homology (PH) domain proteins, while PtdInsPn quantitation is accomplished by extraction and separation of radiolabeled cellular PtdInsPns. Here we describe preparation of a covalent protein-PtdIns(3,4,5)P3 immunogen, characterization of binding selectivity of an anti-PtdIns(3,4,5)P3 IgM, and immunodetection of PtdIns(3,4,5)P3 in stimulated mammalian cells. This antibody has greater than three orders of magnitude selectivity for binding PtdIns(3,4,5)P3 relative to its precursor, phosphatidylinositol 4,5-bis-phosphate (PtdIns(4,5)P2), and is therefore optimal for studies of cell function. The immunodetection in platelet-derived growth factor (PDGF)-stimulated NIH 3T3 cells was bench-marked against HPLC analysis of [3H]-myo-inositol-labeled cellular PtdInsPns. In addition, the changes in subcellular amounts and localizations of both PtdIns(3,4,5)P3 and PtdIns(4,5)P2 in stimulated NIH 3T3 fibroblasts and human neutrophils were observed by immunofluorescence. In insulin- or PDGF-stimulated fibroblasts, PtdIns(3,4,5)P3 levels increased in the cytoplasm, peaking at 10 min. In contrast, increases in the PtdIns(4,5)P2 levels were detected in nuclei, corresponding to the production of new substrate following depletion by phosphoinositide (PI) 3-kinase.


Plant Physiology | 2007

Inositol Polyphosphate 5-Phosphatases 1 and 2 Are Required for Regulating Seedling Growth

Bhadra Gunesekera; Javad Torabinejad; Jamille Robinson; Glenda E. Gillaspy

Signals can be perceived and amplified at the cell membrane by receptors coupled to the production of a variety of second messengers, including myoinositol 1,4,5-trisphosphate [Ins(1,4,5)P3]. The myoinositol polyphosphate 5-phosphatases (5PTases; EC 3.1.3.56) comprise a large protein family that hydrolyzes 5-phosphates from a variety of myoinositol phosphate (InsP) and phosphoinositide phosphate (PtdInsP) substrates. Arabidopsis thaliana has 15 genes encoding 5PTases. Biochemical analyses of a subgroup of 5PTase enzymes suggest that these enzymes have both overlapping and unique substrate preferences. Ectopic expression of these genes in transgenic plants can reduce Ins(1,4,5)P3 levels and alter abscisic acid (ABA) signaling. To further explore the function of 5PTases in signaling, we have identified and characterized T-DNA insertional mutants for 5PTase1 and 5PTase2 and produced a double mutant. When grown in the dark, the seeds from these mutants germinate faster than wild-type seeds and the mutant seedlings have longer hypocotyls than wild-type seedlings. Seeds from these mutant lines also demonstrate an increase in sensitivity to ABA. These changes in early seedling growth are accompanied by mass increases in Ins(1,4,5)P3, but not by changes in endogenous ABA content. By labeling the endogenous myoinositol pool in 5ptase1 and 5ptase2 mutants, we detected increases in Ins(1,4,5)P3 and a decrease in PtdIns, PtdIns(4)P, and phosphatidylinositol (4,5) bisphosphate. Taken together, these data indicate that the At5PTase1 and At5PTase2 genes have nonredundant roles in hydrolyzing inositol second-messenger substrates and that regulation of Ins(1,4,5)P3 levels is important during germination and early seedling development.


Methods of Molecular Biology | 2004

Measurement and Immunofluorescence of Cellular Phosphoinositides

Hiroko Hama; Javad Torabinejad; Glenn D. Prestwich; Daryll B. DeWald

Phosphoinositides are a vitally important class of intracellular-signaling molecules that regulate cellular processes, including signaling through cell-surface receptors, remodeling of the cytoskeleton, vesicle-mediated protein trafficking, and various nuclear functions. Methods for the analysis of in vivo phosphoinositide concentration, such as the one described in this chapter enable quantification of all phosphoinositides from a population of cells. This method involves metabolic labeling of cells with myo<-[2-3H] inositol, followed by lipid extraction, and quantification by high-performance liquid chromatography (HPLC). It provides improved efficiency and reproducibility when analyzing yeast, plant cells, and is applicable to animal cells as well. In addition, a technique for determining the intracellular location of phosphoinositides is described. When quantification and localization techniques are used in parallel, an investigator can identify cell, and even subcellular concentration changes. The technique described in this chapter uses immunodetection with antiphosphoinositide antibodies to determine the localization and relative concentrations of phosphinositides in fixed cells. The availability of antibodies allows an investigator to perform immunofluorescence and potentially immunoelectron microscopy of phosphoinositide localization on particular cellular, organellar, or vesicular membranes.


Plant Physiology | 2001

Rapid Accumulation of Phosphatidylinositol 4,5-Bisphosphate and Inositol 1,4,5-Trisphosphate Correlates with Calcium Mobilization in Salt-Stressed Arabidopsis

Daryll B. DeWald; Javad Torabinejad; Christopher A. Jones; Joseph C. Shope; Amanda R. Cangelosi; James E. Thompson; Glenn D. Prestwich; Hiroko Hama


Journal of Experimental Botany | 2006

Mutant identification and characterization of the laccase gene family in Arabidopsis

Xiaoning Cai; Elizabeth J. Davis; Jenny Ballif; Mingxiang Liang; Emily Bushman; Victor Haroldsen; Javad Torabinejad; Yajun Wu


Cancer Research | 2005

Metastasis Suppression by Breast Cancer Metastasis Suppressor 1 Involves Reduction of Phosphoinositide Signaling in MDA-MB-435 Breast Carcinoma Cells

Daryll B. DeWald; Javad Torabinejad; Rajeev S. Samant; Derrick Johnston; Nuray Erin; Joseph C. Shope; Yi Xie; Danny R. Welch


Journal of Invertebrate Pathology | 2006

Mutants and isolates of Metarhizium anisopliae are diverse in their relationships between conidial pigmentation and stress tolerance

Drauzio E.N. Rangel; Michael J. Butler; Javad Torabinejad; Anne J. Anderson; Gilberto U.L. Braga; Alan W. Day; Donald W. Roberts


Molecular Biology of the Cell | 2003

The synaptojanin-like protein Inp53/Sjl3 functions with clathrin in a yeast TGN-to-endosome pathway distinct from the GGA protein- dependent pathway

Seon-Ah Ha; Javad Torabinejad; Daryll B. DeWald; Markus R. Wenk; Louise Lucast; Pietro De Camilli; Richard Newitt; Ruedi Aebersold; Steven F. Nothwehr

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Hiroko Hama

Medical University of South Carolina

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