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See detailSHIP2 controls PtdIns(3,4,5)P3 and PKB activity in response to oxidative stress
Zhang, J.; Liu, Z.; Rasschaert, J. et al

in Cellular Signalling (2007), 19

Reactive oxygen species (ROS) are known to be involved in redox signalling pathways that may contribute to normal cell function as well as disease progression. The tumour suppressor PTEN and the inositol ... [more ▼]

Reactive oxygen species (ROS) are known to be involved in redox signalling pathways that may contribute to normal cell function as well as disease progression. The tumour suppressor PTEN and the inositol 5-phosphatase SHIP2 are critical enzymes in the control of PtdIns(3,4,5)P(3) level. It has been reported that oxidants, including those produced in cells such as macrophages, can activate downstream signalling via the inactivation of PTEN. The present study evaluates the potential impact of SHIP2 on phosphoinositides in cells exposed to sodium peroxide. We used a model of SHIP2 deficient mouse embryonic fibroblasts (MEFs) stimulated by H(2)O(2): at 15 min, PtdIns(3,4,5)P(3) was markedly increased in SHIP2 -/- cells as compared to +/+ cells. In contrast, no significant increase in PtdIns(3,4)P(2) could be detected at 15 or 120 min incubation of the cells with H(2)O(2) (0.6 mM). PKB activity was also upregulated in SHIP2 -/- cells as compared to +/+ cells in response to H(2)O(2). SHIP2 add back experiments in SHIP2 -/- cells confirm its critical role as a lipid phosphatase in the control of PtdIns(3,4,5)P(3) level in response to H(2)O(2). We conclude that SHIP2 lipid phosphatase activity plays an important role in the metabolism PtdIns(3,4,5)P(3) which is demonstrated in oxygen stressed cells [less ▲]

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See detailPhosphoinositide phosphatases in a network of signaling reactions
Blero, D.; Payrastre, B.; Schurmans, Stéphane ULg et al

in Pflügers Archiv : European Journal of Physiology (2007), 455

Phosphoinositide phosphatases dephosphorylate the three positions (D-3, 4 and 5) of the inositol ring of the poly-phosphoinositides. They belong to different families of enzymes. The PtdIns(3,4)P(2) 4 ... [more ▼]

Phosphoinositide phosphatases dephosphorylate the three positions (D-3, 4 and 5) of the inositol ring of the poly-phosphoinositides. They belong to different families of enzymes. The PtdIns(3,4)P(2) 4-phosphatase family, the tumour suppressor phosphatase and tensin homolog deleted on chromosome 10 (PTEN), SAC1 domain phosphatases and myotubularins belong to the tyrosine protein phosphatases superfamily. They share the presence of a conserved cysteine residue in the consensus CX(5)RT/S. Another family consists of the inositol polyphosphate 5-phosphatase isoenzymes. The importance of these phosphoinositide phosphatases in cell regulation is illustrated by multiple examples of their implications in human diseases such as Lowe syndrome, X-linked myotubular myopathy, cancer, diabetes or bacterial infection [less ▲]

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See detailPhosphatidylinositol 3,4,5-trisphosphate modulation in Ship2-deficient mouse embryonic fibroblasts
Blero, D.; Zhang, J.; Pesesse, X. et al

in FEBS Journal (2005), 272

SHIP2, the ubiquitous SH2 domain containing inositol 5-phosphatase, includes a series of protein interacting domains and has the ability to dephosphorylate phosphatidylinositol 3,4,5-trisphosphate [PtdIns ... [more ▼]

SHIP2, the ubiquitous SH2 domain containing inositol 5-phosphatase, includes a series of protein interacting domains and has the ability to dephosphorylate phosphatidylinositol 3,4,5-trisphosphate [PtdIns(3,4,5)P3] in vitro. The present study, which was undertaken to evaluate the impact of SHIP2 on PtdIns(3,4,5)P3 levels, was performed in a mouse embryonic fibroblast (MEF) model using SHIP2 deficient (– ⁄ –) MEF cells derived from knockout mice. PtdIns(3,4,5)P3 was upregulated in serum stimulated – ⁄ – MEF cells as compared to +⁄+ MEF cells. Although the absence of SHIP2 had no effect on basal PtdIns(3,4,5)P3 levels, we show here that this lipid was significantly upregulated in SHIP2 – ⁄ – cells but only after short-term (i.e. 5–10 min) incubation with serum. The difference in PtdIns(3,4,5)P3 levels in heterozygous fibroblast cells was intermediate between the +⁄+ and the – ⁄ – cells. In our model, insulin-like growth factor-1 stimulation did not show this upregulation. Serum stimulated phosphoinositide 3-kinase (PI 3-kinase) activity appeared to be comparable between +⁄+ and – ⁄ – cells. Moreover, protein kinase B, but not mitogen activated protein kinase activity, was also potentiated in SHIP2 deficient cells stimulated by serum. The upregulation of protein kinase B activity in serum stimulated cells was totally reversed in the presence of the PI 3-kinase inhibitor LY-294002, in both +⁄+ and – ⁄ – cells. Altogether, these data establish a link between SHIP2 and the acute control of PtdIns(3,4,5)P3 levels in intact cells [less ▲]

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