Phospholipase C Regulation of Phosphatidylinositol 3,4,5-trisphosphate-mediated Chemotaxis

Department of Molecular Cell Biology, University of Groningen, 9751 NN Haren, The Netherlands.
Molecular Biology of the Cell (Impact Factor: 4.47). 01/2008; 18(12):4772-9. DOI: 10.1091/mbc.E07-05-0407
Source: PubMed


Generation of a phosphatidylinositol 3,4,5-trisphosphate [PI(3,4,5)P(3)] gradient within the plasma membrane is important for cell polarization and chemotaxis in many eukaryotic cells. The gradient is produced by the combined activity of phosphatidylinositol 3-kinase (PI3K) to increase PI(3,4,5)P(3) on the membrane nearest the polarizing signal and PI(3,4,5)P(3) dephosphorylation by phosphatase and tensin homolog deleted on chromosome ten (PTEN) elsewhere. Common to both of these enzymes is the lipid phosphatidylinositol 4,5-bisphosphate [PI(4,5)P(2)], which is not only the substrate of PI3K and product of PTEN but also important for membrane binding of PTEN. Consequently, regulation of phospholipase C (PLC) activity, which hydrolyzes PI(4,5)P(2), could have important consequences for PI(3,4,5)P(3) localization. We investigate the role of PLC in PI(3,4,5)P(3)-mediated chemotaxis in Dictyostelium. plc-null cells are resistant to the PI3K inhibitor LY294002 and produce little PI(3,4,5)P(3) after cAMP stimulation, as monitored by the PI(3,4,5)P(3)-specific pleckstrin homology (PH)-domain of CRAC (PH(CRAC)GFP). In contrast, PLC overexpression elevates PI(3,4,5)P(3) and impairs chemotaxis in a similar way to loss of pten. PI3K localization at the leading edge of plc-null cells is unaltered, but dissociation of PTEN from the membrane is strongly reduced in both gradient and uniform stimulation with cAMP. These results indicate that local activation of PLC can control PTEN localization and suggest a novel mechanism to regulate the internal PI(3,4,5)P(3) gradient.

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    • "We first confirmed that killing of M. abscessus by Dictyostelium was impaired by autophagy inhibitors (Supplementary Fig S8). Using published deletion mutants (Traynor et al, 2000; Luo et al, 2003; Kortholt et al, 2007; Cho et al, 2008), we observed enhanced killing of M. abscessus by strains deficient in phospholipase c (PLCÀ) or inositol (1,4,5)-tris- phosphate receptor (IP3RÀ; Fig 5A) "
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    ABSTRACT: Mycobacterium tuberculosis (MTB) remains a major challenge to global health made worse by the spread of multidrug resistance. We therefore examined whether stimulating intracellular killing of mycobacteria through pharmacological enhancement of macroautophagy might provide a novel therapeutic strategy. Despite the resistance of MTB to killing by basal autophagy, cell-based screening of FDA-approved drugs revealed two anticonvulsants, carbamazepine and valproic acid, that were able to stimulate autophagic killing of intracellular M. tuberculosis within primary human macrophages at concentrations achievable in humans. Using a zebrafish model, we show that carbamazepine can stimulate autophagy in vivo and enhance clearance of M. marinum, while in mice infected with a highly virulent multidrug-resistant MTB strain, carbamazepine treatment reduced bacterial burden, improved lung pathology and stimulated adaptive immunity. We show that carbamazepine induces antimicrobial autophagy through a novel, evolutionarily conserved, mTOR-independent pathway controlled by cellular depletion of myo-inositol. While strain-specific differences in susceptibility to in vivo carbamazepine treatment may exist, autophagy enhancement by repurposed drugs provides an easily implementable potential therapy for the treatment of multidrug-resistant mycobacterial infection. © 2014 The Authors. Published under the terms of the CC BY 4.0 license.
    EMBO Molecular Medicine 12/2014; 7(2). DOI:10.15252/emmm.201404137 · 8.67 Impact Factor
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    • "The amoeba Dictyostelium discoideum, an exceptional model for studying the regulation of human cell motility and chemotaxis [19]–[27], contains the gene ptenA, an ortholog of the human PTEN gene. Deletion of ptenA in D.discoideum causes major defects in lateral pseudopod suppression, motility, chemotaxis and natural aggregation [28]–[34]. As is the case for human PTEN, PtenA in D.discoideum dephosphorylates phospahtidylinositol (3,4,5)-trisphosphate (PIP3) to form phophatidylinositol (4,5)-bisphosphate (PIP2) [35], [36] and mediates PIP3 oscillations [37]–[41], which correlate with actin polymerization and pseudopod extension [30], [39]–[43]. "
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    ABSTRACT: Mutations in the tumor suppressor gene PTEN are associated with a significant proportion of human cancers. Because the human genome also contains several homologs of PTEN, we considered the hypothesis that if a homolog, functionally redundant with PTEN, can be overexpressed, it may rescue the defects of a PTEN mutant. We have performed an initial test of this hypothesis in the model system Dictyostelium discoideum, which contains an ortholog of human PTEN, ptenA. Deletion of ptenA results in defects in motility, chemotaxis, aggregation and multicellular morphogenesis. D. discoideum also contains lpten, a newly discovered homolog of ptenA. Overexpressing lpten completely rescues all developmental and behavioral defects of the D. discoideum mutant ptenA-. This hypothesis must now be tested in human cells.
    PLoS ONE 09/2014; 9(9):e108495. DOI:10.1371/journal.pone.0108495 · 3.23 Impact Factor
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    • "35 Activation of phospholipase C-mediated PIP2 degradation resulted in downregulation of PIP2-dependent PTEN activity, resulting in increased PIP3 level at the leading edge in the chemotaxing cells.34, 36, 37, 38 In this context, it is plausible that PIP5Kα KD, which can also deplete PIP2 level like the action of phospholipase C, can enhance neurite outgrowth. Rho family small guanosine triphsopahatases that coordinate cytoskeletal membrane remodeling also have an important role in the neurite outgrowth. "
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    ABSTRACT: Neurite outgrowth, a cell differentiation process involving membrane morphological changes, is critical for neuronal network and development. The membrane lipid, phosphatidylinositol (PI) 4,5-bisphosphate (PIP2), is a key regulator of many important cell surface events of membrane signaling, trafficking and dynamics. This lipid is produced mainly by the type I PI 4-phosphate 5-kinase (PIP5K) family members. In this study, we addressed whether PIP5Kα, an isoform of PIP5K, could have a role in neurite outgrowth induced by nerve growth factor (NGF). For this purpose, we knocked down PIP5Kα in PC12 rat pheochromocytoma cells by stable expression of PIP5Kα microRNA that significantly reduced PIP5Kα expression and PIP2 level. Interestingly, NGF-induced neurite outgrowth was more prominent in PIP5Kα-knockdown (KD) cells than in control cells. Conversely, add-back of PIP5Kα into PIP5Kα KD cells abrogated the effect of NGF on neurite outgrowth. NGF treatment activated PI 3-kinase (PI3K)/Akt pathway, which seemed to be associated with reactive oxygen species generation. Similar to the changes in neurite outgrowth, the PI3K/Akt activation by NGF was potentiated by PIP5Kα KD, but was attenuated by the reintroduction of PIP5Kα. Moreover, exogenously applied PIP2 to PIP5Kα KD cells also suppressed Akt activation by NGF. Together, our results suggest that PIP5Kα acts as a negative regulator of NGF-induced neurite outgrowth by inhibiting PI3K/Akt signaling pathway in PC12 cells.
    03/2013; 45(3):e16. DOI:10.1038/emm.2013.18
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