Role Of SHIP1 Research Articles

Docking of Syk to FcεRI is enhanced by Lyn but limited in duration by SHIP1.

The high-affinity immunoglobulin E (IgE) receptor, FcεRI, is the primary immune receptor found on mast cells and basophils. Signal initiation is classically attributed to phosphorylation of FcεRIβ-and γ-subunits by the Src family kinase (SFK) Lyn, followed by the recruitment and activation of the tyrosine kinase Syk. FcεRI signaling is tuned by the balance between Syk-driven positive signaling and the engagement of inhibitory molecules, including SHIP1. Here, we investigate the mechanistic contributions of Lyn, Syk, and SHIP1 to the formation of the FcεRI signalosome. Using Lyn-deficient RBL-2H3 mast cells, we found that another SFK can weakly monophosphorylate the γ-subunit, yet Syk still binds the incompletely phosphorylated immunoreceptor tyrosine-based activation motifs (ITAMs). Once recruited, Syk further enhances γ-phosphorylation to propagate signaling. In contrast, the loss of SHIP1 recruitment indicates that Lyn is required for phosphorylation of the β-subunit. We demonstrate two noncanonical Syk binding modes, trans γ-bridging and direct β-binding, that can support signaling when SHIP1 is absent. Using single particle tracking, we reveal a novel role of SHIP1 in regulating Syk activity, where the presence of SHIP1 in the signaling complex acts to increase the Syk:receptor off-rate. These data suggest that the composition and dynamics of the signalosome modulate immunoreceptor signaling activities.

The Role of SHIP1 on Apoptosis and Autophagy in the Adipose Tissue of Obese Mice.

Obesity-induced adipocyte apoptosis promotes inflammation and insulin resistance. Src homology domain-containing inositol 5′-phosphatase 1 (SHIP1) is a key factor of apoptosis and inflammation. However, the role of SHIP1 in obesity-induced adipocyte apoptosis and autophagy is unclear. We found that diet-induced obesity (DIO) mice have significantly greater crown-like structures and terminal deoxynucleotidyl transferase deoxyuridine triphosphate (dUTP) nick-end labeling (TUNEL)-positive cells than ob/ob or control mice. Using RNA sequencing (RNA-seq) analysis, we identified that the apoptosis- and inflammation-related gene Ship1 is upregulated in DIO and ob/ob mice compared with control mice. In particular, DIO mice had more SHIP1-positive macrophages and lysosomal-associated membrane protein 1 (LAMP1) as well as a higher B-cell lymphoma 2 (Bcl-2)-associated X protein (Bax)/Bcl-2 ratio compared with ob/ob or control mice. Furthermore, caloric restriction attenuated adipose tissue inflammation, apoptosis, and autophagy by reversing increases in SHIP1-associated macrophages, Bax/Bcl2-ratio, and autophagy in DIO and ob/ob mice. These results demonstrate that DIO, not ob/ob, aggravates adipocyte inflammation, apoptosis, and autophagy due to differential SHIP1 expression. The evidence of decreased SHIP1-mediated inflammation, apoptosis, and autophagy indicates new therapeutic approaches for obesity-induced chronic inflammatory diseases.

SHIP1 inhibits cell growth, migration, and invasion in non‑small cell lung cancer through the PI3K/AKT pathway

Src homology 2‑containing inositol‑5'‑phosphatase 1 (SHIP1) serves a vital role in the occurrence and development of hematological tumors, but there is limited knowledge regarding the role of SHIP1 in various solid tumors, including lung cancer. In the present study, the aim was to investigate the expression and functional mechanisms of SHIP1 in non‑small cell lung cancer (NSCLC). The Gene Expression Omnibus database demonstrated that SHIP1 had low expression in NSCLC. Further studies using fresh tissues and cell lines also confirmed this observation. Biological function analyses revealed that SHIP1 overexpression notably suppressed cell growth, migration and invasion in vitro and in vivo in NSCLC. Mechanistic analyses indicated that SHIP1 inactivated the phosphoinositide 3‑kinase (PI3K)/AKT pathway to suppress signals associated with the cell cycle and epithelial‑mesenchymal transition. In clinical specimens, reduced SHIP1 is an unfavorable factor and is negatively associated with the T classification, N classification and clinical stage. Furthermore, patients with low SHIP1 levels exhibited reduced survival rate, compared with patients with high levels of the protein. Notably, the promoter of the SHIP1 gene lacks CpG islands, and the suppression of SHIP1 expression is not associated with epidermal growth factor receptor or Kirsten rat sarcoma mutations. Thus, the present study demonstrated that SHIP1 inhibits cell growth, migration and invasion in NSCLC through the PI3K/AKT pathway. Additionally, reduced SHIP1 expression may be an unfavorable factor for NSCLC.

Phosphatases in Mouse Mast Cells Rapid IgE Desensitization: The Role of SHIP-1

Drug hypersensitivity, Desensitization, Precision medicine, Molecular mechanisms, In vitro desensitization models, FcRI, IgE mediated, Mast cells, SHIP1, ITIM, and ITAM.

Role of SHIP1 in Invariant NKT Cell Development and Functions.

SHIP1 is a 5'-inositol phosphatase known to negatively regulate the signaling product of the PI3K pathway, phosphatidylinositol (3-5)-trisphosphate. SHIP1 is recruited to a large number of inhibitory receptors expressed on invariant NK (iNKT) cells. We hypothesized that SHIP1 deletion would have major effects on iNKT cell development by altering the thresholds for positive and negative selection. Germline SHIP1 deletion has been shown to affect T cells as well as other immune cell populations. However, the role of SHIP1 on T cell function has been controversial, and its participation on iNKT cell development and function has not been examined. We evaluated the consequences of SHIP1 deletion on iNKT cells using germline-deficient mice, chimeric mice, and conditionally deficient mice. We found that T cell and iNKT cell development are impaired in germline-deficient animals. However, this phenotype can be rescued by extrinsic expression of SHIP1. In contrast, SHIP1 is required cell autonomously for optimal iNKT cell cytokine secretion. This suggests that SHIP1 calibrates the threshold of iNKT cell reactivity. These data further our understanding of how iNKT cell activation is regulated and provide insights into the biology of this unique cell lineage.

Molecular control of PtdIns(3,4,5)P3 signaling in neutrophils.

Neutrophils play critical roles in innate immunity and host defense. However, excessive neutrophil accumulation or hyper-responsiveness of neutrophils can be detrimental to the host system. Thus, the response of neutrophils to inflammatory stimuli needs to be tightly controlled. Many cellular processes in neutrophils are mediated by localized formation of an inositol phospholipid, phosphatidylinositol (3,4,5)-trisphosphate (PtdIns(3,4,5)P3), at the plasma membrane. The PtdIns(3,4,5)P3 signaling pathway is negatively regulated by lipid phosphatases and inositol phosphates, which consequently play a critical role in controlling neutrophil function and would be expected to act as ideal therapeutic targets for enhancing or suppressing innate immune responses. Here, we comprehensively review current understanding about the action of lipid phosphatases and inositol phosphates in the control of neutrophil function in infection and inflammation.

Lineage specific role of Ship1 in development of allergic airway inflammation

Background The PI3K pathway is a potent mediator of several functions associated with asthma pathogenesis, including supporting leukocyte survival, activation, migration and cytokine release. Proper negative regulation of this pathway is integral in order to restrict overactive immune responses. Negative regulation of PI3K is predominantly controlled by the lipid phosphatases PTEN and SHIP-1. Inpp5d (Ship1) deficient mice develop spontaneous airway inflammation and have enhanced sensitivity to allergen induced airway inflammation. We hypothesized that deleting Ship1 expression specifically in lineages known to be crucial for adaptive Th2 responses would uncover more subtle effects that could either positively or negatively regulate disease severity in a mouse model of allergic airway inflammation (AAI).

SHIP1 regulates MSC numbers and their osteolineage commitment by limiting induction of the PI3K/Akt/β-catenin/Id2 axis.

Here, we show that Src homology 2-domain-containing inositol 5'-phosphatase 1 (SHIP1) is required for the efficient development of osteoblasts from mesenchymal stem cells (MSCs) such that bone growth and density are reduced in mice that lack SHIP1 expression in MSCs. We find that SHIP1 promotes the osteogenic output of MSCs by limiting activation of the PI3K/Akt/β-catenin pathway required for induction of the MSC stemness factor Id2. In parallel, we demonstrate that mice with myeloid-restricted ablation of SHIP1, including osteoclasts (OCs), show no reduction in bone mass or density. Hence, diminished bone mass and density in the SHIP1-deficient mice results from SHIP deficiency in MSC and osteolineage progenitors. Intriguingly, mice with a SHIP-deficient MSC compartment also exhibit decreased OC numbers. In agreement with our genetic findings we also show that treatment of mice with an SHIP1 inhibitor (SHIPi) significantly reduces bone mass. These findings demonstrate a novel role for SHIP1 in MSC fate determination and bone growth. Further, SHIPi may represent a novel therapeutic approach to limit bone development in osteopetrotic and sclerotic bone diseases.

Role of SHIP1 in bone biology

The bone marrow milieu comprising both hematopoietic and nonhematopoietic lineages has a unique structural organization. Bone undergoes continuous remodeling throughout life. This dynamic process involves a balance between bone-forming osteoblasts (OBs) derived from multipotent mesenchymal stem cells (MSCs) and bone-resorbing osteoclasts (OCs) derived from hematopoietic stem cells (HSCs). Src homology 2-domain-containing inositol 5'-phosphatase 1 (SHIP1) regulates cellular processes such as proliferation, differentiation, and survival via the PI3K/Akt signaling pathway initiated at the plasma membrane. SHIP1-deficient mice also exhibit profound osteoporosis that has been proposed to result from hyperresorptive activity by OCs. We have previously observed that SHIP1 is expressed in primary OBs, which display defective development in SHIP1-deficient mice. These findings led us to question whether SHIP1 plays a functional role in osteolineage development from MSC in vivo, which contributes to the osteoporotic phenotype in germline SHIP1 knockout mice. In this short review, we discuss our current understanding of inositol phospholipid signaling downstream of SHIP1 in bone biology.

P049 A possible role of mucosal cytokine profile for predicting response to infliximab therapy in ulcerative colitis

leads to altered cytokine production and the development of Crohn’s like ileitis, which in fact presents one of the few mouse models in which intestinal inflammation develops spontaneously. SHIP1 is expressed exclusively in hematopoietic lineage and bone marrow parenchymal cells, and colitis can be transferred to wild type mice by SHIP1 / splenocytes. These data strongly suggest a role for SHIP1 in immune cells in the pathogenesis of CD. We therefore investigated SHIP1 activity and expression in peripheral blood mononuclear cells (PBMCs) from CD patients. Methods: We developed a SHIP1 activity assay by precipitating endogenous SHIP1 from PBMC lysates and incubating precipitates with PtdIns(3,4,5)P3. The accumulation of free phosphate as a result of SHIP1 activity was measured by Malachite green assay. The specificity and quantitative range of this assay were confirmed by using SHIP1 deficient cells, and testing different concentrations of protein. Total SHIP1, SHIP2 and PTEN levels were determined by quantitative Western blot analysis (Odyssey). Results: We performed SHIP1 activity assays on PBMCs of 34 CD patients. In every individual measurement, SHIP1 activity in PBMCs from healthy donors was taken as control (n = 25). We identified 5 patients with SHIP1 expression below detection limit and hence low SHIP1 activity. The remaining patients showed a significant upregulation of SHIP1 protein expression levels, but reduced SHIP1 activity after correction for SHIP1 expression. Differences in SHIP1 activity and expression patterns were not caused by altered PBMC composition as no significant differences in B-cell, T-cell or monocyte percentages were observed between CD patients (n = 15) and healthy controls (n = 9). SHIP2 and PTEN protein levels were normal in all CD patients. Conclusions: Our results demonstrate for the first time that immune cells from 15% of CD patients have decreased SHIP1 expression and activity levels, which may affect immune cell function through interference with phospholipid levels. The remaining 85% of CD patients show a decreased activity of SHIP1, although this may be compensated for by an increased SHIP1 expression. Together, these data suggest a role for impaired SHIP1 activity in the development of disease in a subset of CD patients.

Deletion of SHIP-1 in Mice Leads to Diminished Th2 Responses to TCR Stimulation in vitro and Allergen Immunization in vivo

RATIONALE: Src Homology 2 domain-containing inositol 5'-phosphatase 1 (SHIP-1) functions as a negative regulator of signaling pathways triggered by antigen, cytokine and Fc receptors in both lymphocytes and myeloid cells. We have shown that SHIP-1 deficiency leads to a spontaneous allergic inflammation in the murine lung. However, the role of SHIP-1 in adaptive immune response is unclear. To determine the contribution of SHIP-1 in T-cell response, we examined in vitro stimulation of T cell receptor and in vivo ovalbumin (OVA)-induced lung inflammation in mice deficient in SHIP-1.METHODS: Splenocytes from SHIP-1−/− and wild type (WT) Balb/c mice were stimulated with immobilized anti-CD3 and anti-CD28 for 2 days and the levels of IL-4, IL-13, and IFN-γ were measured. SHIP-1−/− and WT mice were immunized with OVA in Alum. After intranasal OVA challenge, we analyzed lung histology, bronchoalveolar lavage (BAL) cell recovery/differential, cytokine and chemokine expression, and airway hyperresponsiveness. We also determined cytokine production by cells from peritrachea lymph nodes and spleen after antigen re-stimulation.RESULTS: Compared with WT mice, OVA challenged SHIP-1−/− mice (OVA-SHIP-1) showed decreased eosinophilic infiltration into the lung, lower level of OVA-specific IgE in the serum, and diminished levels of IL-4 and IL-13 in the BAL. Lymphocytes from OVA-SHIP-1 released decreased amount of IL-4 and IL-13 in response to OVA stimulation.CONCLUSIONS: These results demonstrate that SHIP-1 deficiency leads to diminished Th2 responses in vitro and in vivo, suggesting that, in contrast to innate immunity, SHIP-1 may play a critical role in Th2 responses in adaptive immunity. RATIONALE: Src Homology 2 domain-containing inositol 5'-phosphatase 1 (SHIP-1) functions as a negative regulator of signaling pathways triggered by antigen, cytokine and Fc receptors in both lymphocytes and myeloid cells. We have shown that SHIP-1 deficiency leads to a spontaneous allergic inflammation in the murine lung. However, the role of SHIP-1 in adaptive immune response is unclear. To determine the contribution of SHIP-1 in T-cell response, we examined in vitro stimulation of T cell receptor and in vivo ovalbumin (OVA)-induced lung inflammation in mice deficient in SHIP-1. METHODS: Splenocytes from SHIP-1−/− and wild type (WT) Balb/c mice were stimulated with immobilized anti-CD3 and anti-CD28 for 2 days and the levels of IL-4, IL-13, and IFN-γ were measured. SHIP-1−/− and WT mice were immunized with OVA in Alum. After intranasal OVA challenge, we analyzed lung histology, bronchoalveolar lavage (BAL) cell recovery/differential, cytokine and chemokine expression, and airway hyperresponsiveness. We also determined cytokine production by cells from peritrachea lymph nodes and spleen after antigen re-stimulation. RESULTS: Compared with WT mice, OVA challenged SHIP-1−/− mice (OVA-SHIP-1) showed decreased eosinophilic infiltration into the lung, lower level of OVA-specific IgE in the serum, and diminished levels of IL-4 and IL-13 in the BAL. Lymphocytes from OVA-SHIP-1 released decreased amount of IL-4 and IL-13 in response to OVA stimulation. CONCLUSIONS: These results demonstrate that SHIP-1 deficiency leads to diminished Th2 responses in vitro and in vivo, suggesting that, in contrast to innate immunity, SHIP-1 may play a critical role in Th2 responses in adaptive immunity.

The role of SHIP1 in T-lymphocyte life and death

SHIP1 [SH2 (Src homology 2)-containing inositol phosphatase-1], an inositol 5-phosphatase expressed in haemopoietic cells, acts by hydrolysing the 5-phosphates from PtdIns(3,4,5)P(3) and Ins(1,3,4,5)P(4), thereby negatively regulating the PI3K (phosphoinositide 3-kinase) pathway. SHIP1 plays a major role in inhibiting proliferation of myeloid cells. As a result, SHIP1(-/-) mice have an increased number of neutrophils and monocytes/macrophages due to enhanced survival and proliferation of their progenitors. Although SHIP1 contributes to PtdIns(3,4,5)P(3) metabolism in T-lymphocytes, its exact role in this cell type is much less explored. Jurkat cells have recently emerged as an interesting tool to study SHIP1 function in T-cells because they do not express SHIP1 at the protein level, thereby allowing reintroduction experiments in a relatively easy-to-use system. Data obtained from SHIP1 reintroduction have revealed that SHIP1 not only acts as a negative player in T-cell lines proliferation, but also regulates critical pathways, such as NF-kappaB (nuclear factor kappaB) activation, and also appears to remarkably inhibit T-cell apoptosis. On the other hand, experiments using primary T-cells from SHIP1(-/-) mice have highlighted a new role for SHIP1 in regulatory T-cell development, but also emphasize that this protein is not required for T-cell proliferation. In support of these results, SHIP1(-/-) mice are lymphopenic, suggesting that SHIP1 function in T-cells differs from its role in the myeloid lineage.

SHIP-2 Inositol Phosphatase Is Inducibly Expressed in Human Monocytes and Serves to Regulate Fcγ Receptor-mediated Signaling

SHIP-2, a recently identified inositol 5'-phosphatase, shares high level homology with SHIP-1. Although the role of SHIP-1 has been extensively studied, the role of SHIP-2 in myeloid cell functions is not known. Here, we have analyzed the expression patterns, molecular mechanism of activation, and function of SHIP-2 in human myeloid cell Fcgamma receptor (FcgammaR) signaling. We report that SHIP-2 is expressed in transformed myeloid cells and in primary macrophages, but not in peripheral blood monocytes. Treatment of peripheral blood monocytes with bacterial lipopolysaccharide induced expression of SHIP-2 in a dose-dependent manner. FcgammaRIIa clustering in THP-1 cells induced SHIP-2 tyrosine phosphorylation, suggesting a role for SHIP-2 in modulating FcgammaR-mediated function. Consistent with this notion, overexpression of wild-type SHIP-2 (but not catalytically deficient SHIP-2) in THP-1 cells almost completely abrogated NFkappaB-mediated gene transcription in response to FcgammaRIIa clustering. Furthermore, FcgammaRIIa-induced Akt activation was blocked by wild-type SHIP-2, but not by a catalytically deficient mutant of SHIP-2. Additional experiments analyzing the molecular mechanism of SHIP-2 induction by FcgammaRIIa revealed that SHIP-2 associated with the phosphorylated FcgammaRIIa immunoreceptor tyrosine-based activation motif via the SHIP-2 SH2 domain. Thus, an SH2 domain mutant of SHIP-2 failed to associate with FcgammaRIIa or to become tyrosine-phosphorylated upon FcgammaRIIa clustering. Finally, we also demonstrate that SHIP-2 phosphorylation was induced by FcgammaRI clustering in THP-1 cells. These findings unravel a novel level of regulation of FcgammaR-mediated activation of human myeloid cells by the expression and function of the inositol phosphatase SHIP-2.

The SH2 Inositol 5-Phosphatase Ship1 Is Recruited in an SH2-dependent Manner to the Erythropoietin Receptor

Ship1 (SH2 inositol 5-phosphatase 1) has been shown to be a target of tyrosine phosphorylation downstream of cytokine and immunoregulatory receptors. In addition to its catalytic activity on phosphatidylinositol substrates, it can serve as an adaptor protein in binding Shc and Grb2. Erythropoietin (EPO), the primary regulator of erythropoiesis, has been shown to activate the tyrosine phosphorylation of Shc, resulting in recruitment of Grb2. However, the mechanism by which the erythropoietin receptor (EPO-R) recruits Shc remains unknown. EPO activates the tyrosine phosphorylation of Ship1, resulting in the interdependent recruitment of Shc and Grb2. Ship1 is recruited to the EPO-R in an SH2-dependent manner. Utilizing a panel of EPO-R deletion and tyrosine mutants, we have discovered remarkable redundancy in Ship1 recruitment. EPO-R Tyr(401) appears to be a major site of Ship1 binding; however, Tyr(429) and Tyr(431) can also serve to recruit Ship1. In addition, we have shown that EPO stimulates the formation of a ternary complex consisting of Ship1, Shc, and Grb2. Ship1 may modulate several discrete signal transduction pathways. EPO-dependent activation of ERK1/2 and protein kinase B (PKB)/Akt was examined utilizing a panel of EPO-R deletion mutants. Activation of ERK1/2 was observed in EPO-RDelta99, which retains only the most proximal tyrosine, Tyr(343). In contrast, EPO-dependent PKB activation was observed in EPO-RDelta43, but not in EPO-RDelta99. It appears that EPO-dependent PKB activation is downstream of a region that indirectly couples to phosphatidylinositol 3-kinase.