Role of Gab proteins in phosphatidylinositol 3-kinase activation by thrombopoietin (Tpo)

Bouscary, Didier; Lecoq-Lafon, Carinne; Chrétien, Stany; Zompì, Simona; Fichelson, Serge; Muller, Odile; Porteu, Françoise; Dusanter‐Fourt, Isabelle; Gisselbrecht, Sylvie; Mayeux, Patrick; Lacombe, Catherine

doi:10.1038/sj.onc.1204317

Cited by 39 publications

(29 citation statements)

References 51 publications

(53 reference statements)

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“…A novel function of Shc was found to link Gab2 to the phosphotyrosine on the IL-2␤ receptor via Grb2 (41). Consistent with these data, a recent report showed that the Shc docking site on Mpl, Tyr 112 , serves a similar function in promoting Gab phosphorylation by JAK2 (42). However, in our hands, Gab2/SHP2/p85PI3K complex formation was still present in BaF3/T69, albeit reduced compared with BaF3/Mpl cells.…”

Section: Discussionsupporting

confidence: 78%

The Roles of Phosphatidylinositol 3-Kinase and Protein Kinase Cζ for Thrombopoietin-induced Mitogen-activated Protein Kinase Activation in Primary Murine Megakaryocytes

Rojnuckarin¹,

Miyakawa²,

Fox³

et al. 2001

Journal of Biological Chemistry

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Thrombopoietin (TPO) stimulates a network of intracellular signaling pathways that displays extensive cross-talk. We have demonstrated previously that the ERK/mitogen-activated protein kinase pathway is important for TPO-induced endomitosis in primary megakaryocytes (MKs). One known pathway by which TPO induces ERK activation is through the association of Shc with the penultimate phosphotyrosine within the TPO receptor, Mpl. However, several investigators found that the membrane-proximal half of the cytoplasmic domain of Mpl is sufficient to activate ERK in vitro and support base-line megakaryopoiesis in vivo. Using BaF3 cells expressing a truncated Mpl (T69Mpl) as a tool to identify non-Shc/Ras-dependent signaling pathways, we describe here novel mechanisms of TPO-induced ERK activation mediated, in part, by phosphoinositide 3-kinase (PI3K). Similar to cells expressing full-length receptor, PI3K was activated by its incorporation into a complex with IRS2 or Gab2. Furthermore, the MEKphosphorylating activity of protein kinase C (PKC) was also enhanced after TPO stimulation of T69Mpl, contributing to ERK activity. PKC and PI3K also contribute to TPO-induced ERK activation in MKs, confirming their physiological relevance. Like in BaF3 cells, a TPO-induced signaling complex containing p85PI3K is detectable in MKs expressing T61Mpl and is probably responsible for PI3K activation. These data demonstrate a novel role of PI3K and PKC in steadystate megakaryopoiesis.Binding of TPO 1 to its receptor, the product of the protooncogene c-mpl, activates a wide variety of signaling molecules and pathways. As for other cytokine systems, it is becoming clear that the response to TPO is characterized by networks of multiple branching and converging signaling pathways, which display extensive cross-talk. As such, blockade of one signaling pathway can be compensated by alternate pathways. This may partially explain relatively mild hematopoietic phenotypes of mice in which supposedly critical signaling pathways are disrupted by homologous recombination (1-3). We demonstrated previously that the ERK/MAPK pathway is activated in response to TPO in both a BaF3 cell line engineered to express full-length Mpl (BaF3/Mpl) and in primary MKs, and plays an important role in MK endomitosis (4). Consistent with our results, MKs from mice engineered to express only a truncated Mpl receptor missing 60 residues from the COOH terminus of the cytoplasmic domain (T61 or ⌬60 mice) display a reduced capacity to activate ERK and have significantly decreased endomitotic capability after TPO administration in vivo (3). The classic pathway of ERK activation is via growth factor-induced Shc phosphorylation followed by its association with Grb2 (5), which then activates Sos, a nucleotide exchange factor for Ras (6). Consequently, ERK can be activated by Ras-GTP through Raf and MEK phosphorylation. Several groups have reported that Shc is strongly activated in response to TPO (7). Hence, Shc-dependent activation of Ras is likely to be an important mechanism...

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Section: Discussionsupporting

confidence: 78%

The Roles of Phosphatidylinositol 3-Kinase and Protein Kinase Cζ for Thrombopoietin-induced Mitogen-activated Protein Kinase Activation in Primary Murine Megakaryocytes

Rojnuckarin¹,

Miyakawa²,

Fox³

et al. 2001

Journal of Biological Chemistry

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“…Both adipokines induced a strong reduction in insulin receptor substrate 1 expression whereas IL-6 had no effect. Under the same conditions, expression of insulin receptor, Giα2 and insulin receptor substrate 2, another member of the insulin receptor substrate family present in megakaryocytes, 34 was not disturbed. Leptin and resistin receptors induce signaling through the JAK/STAT pathway to expression regulation of suppressor of cytokine signaling (SOCS) proteins, which attenuate cytokine signaling by interfering with receptor function, JAK activity or by targeting activated signaling proteins for degradation by the proteasome.…”

Section: © F E R R a T A S T O R T I F O U N D A T I O Nmentioning

confidence: 75%

Induction of insulin resistance by the adipokines resistin, leptin, plasminogen activator inhibitor-1 and retinol binding protein 4 in human megakaryocytes

Gerrits¹,

Gitz²,

Koekman³

et al. 2012

Haematologica

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The online version of this article has a Supplementary Appendix. BackgroundIn normal platelets, insulin inhibits agonist-induced Ca 2+ mobilization by raising cyclic AMP. Platelet from patients with type 2 diabetes are resistant to insulin and show increased Ca 2+ mobilization, aggregation and procoagulant activity. We searched for the cause of this insulin resistance. Design and MethodsPlatelets, the megakaryocytic cell line CHRF-288-11 and primary megakaryocytes were incubated with adipokines and with plasma from individuals with a disturbed adipokine profile. Thrombininduced Ca 2+ mobilization and signaling through the insulin receptor and insulin receptor substrate 1 were measured. Abnormalities induced by adipokines were compared with abnormalities found in platelets from patients with type 2 diabetes. ResultsResistin, leptin, plasminogen activator inhibitor-1 and retinol binding protein 4 left platelets unchanged but induced insulin resistance in CHRF-288-11 cells. Interleukin-6, tumor necrosis factor-α and visfatin had no effect. These results were confirmed in primary megakaryocytes. Contact with adipokines for 2 hours disturbed insulin receptor substrate 1 Ser 307 -phosphorylation, while contact for 72 hours caused insulin receptor substrate 1 degradation. Plasma with a disturbed adipokine profile also made CHRF-288-11 cells insulin-resistant. Platelets from patients with type 2 diabetes showed decreased insulin receptor substrate 1 expression. ConclusionsAdipokines resistin, leptin, plasminogen activator-1 and retinol binding protein 4 disturb insulin receptor substrate 1 activity and expression in megakaryocytes. This might be a cause of the insulin resistance observed in platelets from patients with type 2 diabetes.Key words: adipokines, insulin, insulin resistance, megakaryocytes, platelets, obesity, type 2 diabetes.Citation: Gerrits AJ, Gitz E, Koekman CA, Visseren FL, van Haeften TW, and Haematologica 2012;97(08):1149-1157. doi:10.3324/haematol.2011

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“…They are called 'scaffolding' or 'docking' proteins because of the presence of multiple functional motifs mediating interactions with many other signaling molecules (Nishida et al, 1999). Grb2-associated binding proteins are involved in signaling events triggered by a variety of stimuli, including GFs, cytokines, G-coupled receptors and T-and B-lymphocyte antigens, ultimately regulating cell growth, differentiation and transformation (Bouscary et al, 2001;Liu et al, 2001;Sattler et al, 2002). Among the Gab2 direct interactors are proteins with key roles in human cancer when mutated, such as PI3K and the tyrosine phosphatase Ptpn11/Shp2.…”

Section: Discussionmentioning

confidence: 99%

“…Previous analyses have identified signaling molecules that can bind to Gab2 on receptor activation, including the tyrosine phosphatase Ptpn11/Shp2, leading to the activation of Erk and Jnk (Yu et al, 2006), the p85 subunit of PI3K, leading to Akt activation (Bouscary et al, 2001), and Src family kinases (Kong et al, 2003). Therefore, to dissect the signaling pathways downstream of Gab2 that could mediate anchorage-independent growth, we examined the effects on cell vitality of a panel of small molecule inhibitors targeting the abovementioned signaling kinases ( Figure 4a).…”

Section: Gab2-driven Anchorage Independence Requires Src and Involvesmentioning

confidence: 99%

The GAB2 signaling scaffold promotes anchorage independence and drives a transcriptional response associated with metastatic progression of breast cancer

et al. 2009

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Acquisition of independence from anchorage to the extracellular matrix is a critical event for onset and progression of solid cancers. To identify and characterize new genes conferring anchorage independence, we transduced MCF10A human normal breast cells with a retroviral cDNA expression library and selected them by growth in suspension. Microarray analysis targeted on library-derived transcripts revealed robust and reproducible enrichment, after selection, of cDNAs encoding the scaffolding adaptor Gab2. Gab2 was confirmed to strongly promote anchorageindependent growth when overexpressed. Interestingly, downregulation by RNA interference of endogenous Gab2 in neoplastic cells did not affect their adherent growth, but abrogated their growth in soft agar. Gab2-driven anchorage independence was found to specifically involve activation of the Src-Stat3 signaling axis. A transcriptional 'signature' of 205 genes was obtained from GAB2-transduced, anchorageindependent MCF10A cells, and found to contain two main functional modules, controlling proliferation and cell adhesion/migration/invasion, respectively. Extensive validation on breast cancer data sets showed that the GAB2 signature provides a robust prognostic classifier for breast cancer metastatic relapse, largely independent from existing clinical and genomic indicators and from estrogen receptor status. This work highlights a pivotal role for GAB2 and its transcriptional targets in anchorage-independent growth and breast cancer metastatic progression.

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Role of Gab proteins in phosphatidylinositol 3-kinase activation by thrombopoietin (Tpo)

Cited by 39 publications

References 51 publications

The Roles of Phosphatidylinositol 3-Kinase and Protein Kinase Cζ for Thrombopoietin-induced Mitogen-activated Protein Kinase Activation in Primary Murine Megakaryocytes

The Roles of Phosphatidylinositol 3-Kinase and Protein Kinase Cζ for Thrombopoietin-induced Mitogen-activated Protein Kinase Activation in Primary Murine Megakaryocytes

Induction of insulin resistance by the adipokines resistin, leptin, plasminogen activator inhibitor-1 and retinol binding protein 4 in human megakaryocytes

The GAB2 signaling scaffold promotes anchorage independence and drives a transcriptional response associated with metastatic progression of breast cancer

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