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Purpose Esophageal squamous cell carcinoma (ESCC) is categorized among ten common aggressive malignancies, with a higher incidence and mortality rates in the developing than in developed countries. The inositol polyphosphate 5-phosphatase (INPP5A), as an intracellular-calcium mobilizer and modifier enzyme, facilitates cell responses to various stimuli. Epithelial-mesenchymal transition (EMT), a transformation procedure, has a vital role in cancer progression and metastasis when epithelial cells lose their traits in favor of obtaining mesenchymal features. In this study, we analyzed the correlation between the expression of INPP5A and the involved genes in EMT pathway through the progression and development of the ESCCs. Materials and methods The gene expression analyses of INPP5A, TWIST1, MMP-2, and EGFR were performed using relative comparative real-time PCR in 58 ESCCs patients compared to corresponding margin-normal esophageal tissues. Results A significant inverse correlation between INPP5A and EGFR/MMP-2 mRNA expression was observed in tumor samples. Underexpression of INPP5A was significantly correlated with overexpression of TWIST1, MMP-2, and EGFR in different invasiveness and aggressiveness pathological features of the ESCCs (P ​ Conclusions The results propose a tumor suppressor role for INPP5A and oncogenic function for concomitant expression of the other genes in ESCC invasion and metastasis. The current study is the first report elucidating the correlation between the downregulation of INPP5A and upregulation of TWIST1, MMP-2, and EGFR in ESCC and introduces this panel of the genes as a marker for poor prognosis of the disease.

Upon antigen binding, the B cell receptor (BCR) undergoes clustering to form a signalosome that propagates downstream signaling required for normal B cell development and physiology. BCR clustering is dependent on remodeling of the cortical actin network, but the mechanisms that regulate actin remodeling in this context remain poorly defined. In this study, we identify the inositol 5-phosphatase INPP5B as a key regulator of actin remodeling, BCR clustering, and downstream signaling in antigen-stimulated B cells. INPP5B acts via dephosphorylation of the inositol lipid PI(4,5)P2 that in turn is necessary for actin disassembly, BCR mobilization, and cell spreading on immobilized surface antigen. These effects can be explained by increased actin severing by cofilin and loss of actin linking to the plasma membrane by ezrin, both of which are sensitive to INPP5B-dependent PI(4,5)P2 hydrolysis. INPP5B is therefore a new player in BCR signaling and may represent an attractive target for treatment of B cell malignancies caused by aberrant BCR signaling.

SHIP2 is a multi-domain inositol 5-phosphatase binding to a variety of phosphotyrosine (pY)-containing proteins through its SH2 domain, so as to regulate various cell signaling pathways by modulating the phosphatidylinositol level in the plasma membrane. Unfavorably

Background: Both INPP5D and INPP5F are members of INPP5 family. INPP5F rs117896735 variant was associated with Parkinson’s disease (PD) risk, and INPP5D was an Alzheimer’s disease (AD) risk gene. However, it remains unclear about the roles of INPP5F rs117896735 variant in AD. Objective: We aim to investigate the roles of rs117896735 in AD. Methods: First, we conducted a candidate variant study to evaluate the association of rs117896735 variant with AD risk using the large-scale AD GWAS dataset. Second, we conducted a gene expression analysis of INPP5F to investigate the expression difference of INPP5F in different human tissues using two large-scale gene expression datasets. Third, we conducted an expression quantitative trait loci analysis to evaluate whether rs117896735 variant regulate the expression of INPP5F. Fourth, we explore the potentially differential expression of INPP5F in AD and control using multiple AD-control gene expression datasets in human brain tissues and whole blood. Results: We found that 1) rs117896735 A allele was associated with the increased risk of AD with OR = 1.15, 95% CI 1.005–1.315, p = 0.042; 2) rs117896735 A allele could increase INPP5F expression in multiple human tissues; 3) INPP5F showed different expression in different human tissues, especially in brain tissues; 4) INPP5F showed significant expression dysregulation in AD compared with controls in human brain tissues. Conclusion: Conclusion: We demonstrate that PD rs117896735 variant could regulate INPP5F expression in brain tissues and increase the risk of AD. These finding may provide important information about the role of rs117896735 in AD.

Background Increasing evidence has suggested inositol polyphosphate 5-phosphatase family contributes to tumorigenesis and tumor progression. However, the role of INPP5F in hepatocellular carcinoma (HCC) and its underlying mechanisms is unclear. Methods The expression of INPP5F in HCC was analyzed in public databases and our clinical specimens. The biological functions of INPP5F were investigated in vitro and vivo. The molecular mechanism of INPP5F in regulating tumor growth were studied by transcriptome-sequencing analysis, mass spectrometry analysis, immunoprecipitation assay and immunofluorescence assay. Results High expression of INPP5F was found in HCC tissues and was associated with poor prognosis in HCC patients. Overexpression of INPP5F promoted HCC cell proliferation, and vice versa. Knockdown of INPP5F suppressed tumor growth in vivo. Results from transcriptome-sequencing analysis showed INPP5F not only regulated a series of cell cycle related genes expression (c-MYC and cyclin E1), but also promoted many aerobic glycolysis related genes expression. Further studies confirmed that INPP5F could enhance lactate production and glucose consumption in HCC cell. Mechanistically, INPP5F activated Notch signaling pathway and upregulated c-MYC and cyclin E1 in HCC via interacting with ASPH. Interestingly, INPP5F was commonly nuclear-located in cells of adjacent non-tumor tissues, while in HCC, cytoplasm-located was more common. LMB (nuclear export inhibitor) treatment restricted INPP5F in nucleus and was associated with inhibition of Notch signaling and cell proliferation. Sequence of nuclear localization signals (NLSs) and nuclear export signals (NESs) in INPP5F aminoacidic sequence were then identified. Alteration of the NLSs or NESs influenced the localization of INPP5F and the expression of its downstream molecules. Furthermore, we found INPP5F interacted with both exportin and importin through NESs and NLSs, respectively, but the interaction with exportin was stronger, leading to cytoplasmic localization of INPP5F in HCC. Conclusion These findings indicate that INPP5F functions as an oncogene in HCC via a translocation mechanism and activating ASPH-mediated Notch signaling pathway. INPP5F may serve as a potential therapeutic target for HCC patients.

Significance Extensive genetic studies have identified numerous genes whose mutations results on Parkinson’s disease (PD), including synaptojanin 1 (SJ1/Park20), a nerve terminal enriched protein that includes an inositol 4-phosphatase domain (Sac domain). In addition, many PD candidate genes have been identified by genome-wide association studies, but for most of these genes, the link to PD remains hypothetical. One such gene is Sac2/INPP5F, which, interestingly, also includes an inositol 4-phosphatase domain. While Sac2KO mice do not show obvious defects, we show a striking synthetic effect in mice of the KO of Sac2 and the Sac domain mutation of SJ1 found in PD patients. These findings support a synergistic role of SJ1 and Sac2 on a PI4P pool whose dysfunction results in PD., Numerous genes whose mutations cause, or increase the risk of, Parkinson’s disease (PD) have been identified. An inactivating mutation (R258Q) in the Sac inositol phosphatase domain of synaptojanin 1 (SJ1/PARK20), a phosphoinositide phosphatase implicated in synaptic vesicle recycling, results in PD. The gene encoding Sac2/INPP5F, another Sac domain-containing protein, is located within a PD risk locus identified by genome-wide association studies. Knock-In mice carrying the SJ1 patient mutation (SJ1RQKI) exhibit PD features, while Sac2 knockout mice (Sac2KO) do not have obvious neurologic defects. We report a “synthetic” effect of the SJ1 mutation and the KO of Sac2 in mice. Most mice with both mutations died perinatally. The occasional survivors had stunted growth, died within 3 wk, and showed abnormalities of striatal dopaminergic nerve terminals at an earlier stage than SJ1RQKI mice. The abnormal accumulation of endocytic factors observed at synapses of cultured SJ1RQKI neurons was more severe in double-mutant neurons. Our results suggest that SJ1 and Sac2 have partially overlapping functions and are consistent with a potential role of Sac2 as a PD risk gene.

Spinocerebellar ataxias 17 (SCA17) is caused by polyglutamine (polyQ) expansion in the TATA box-binding protein (TBP). The selective neurodegeneration in the cerebellum in SCA17 raises the question of why ubiquitously expressed polyQ proteins can cause neurodegeneration in distinct brain regions in different polyQ diseases. By expressing mutant TBP in different brain regions in adult wild-type mice via stereotaxic injection of adeno-associated virus, we found that adult cerebellar neurons are particularly vulnerable to mutant TBP. In SCA17 knock-in mice, mutant TBP inhibits SP1-mediated gene transcription to down-regulate INPP5A, a protein that is highly abundant in the cerebellum. CRISPR/Cas9-mediated deletion of Inpp5a in the cerebellum of wild-type mice leads to Purkinje cell degeneration, and Inpp5a overexpression decreases inositol 1,4,5-trisphosphate (IP3) levels and ameliorates Purkinje cell degeneration in SCA17 knock-in mice. Our findings demonstrate the important contribution of a tissue-specific protein to the polyQ protein-mediated selective neuropathology., It is not yet clear how ubiquitously-expressed proteins can cause the selective degeneration of particular populations of neurons, such as in spinocerebellar ataxia type 17, SCA17, which results from a CAG trinucleotide repeat expansion in the ubiquitously expressed transcription factor TBP. Here, the authors show that mutant TBP suppresses the cerebellum-enriched transcription of Inpp5a and link altered levels of INPP5A to the selective degeneration of cerebellar neurons.

The oculocerebrorenal disorder of Lowe syndrome is an X-linked mutation in the gene oculocerebrorenal syndrome of Lowe 1 (OCRL), characterized by the triad of congenital cataracts, severe intellectual impairment, and renal tubular dysfunction. Manifestations of phenotype in female carriers and patients are extremely rare. We present a female case with congenital cataracts, severe intellectual impairment, sensorineural hearing loss, and renal tubular dysfunction as Lowe syndrome. A 9-year-old Japanese girl visited our hospital due to prolonged proteinuria. Her renal biopsy revealed diffuse mesangium proliferation, sclerosis and dilatation of renal tubules, and mild IgA deposition in the mesangial region. Furthermore, she had congenital cataracts, severe intellectual impairment, and sensorineural hearing loss. Genetic screening did not identify mutations of the ORCL gene encoding inositol polyphosphate 5-phosphatase (IPP-5P) (46 XX, female). However, we found the reduction of enzyme activity of IPP-5P to 50% of the normal value. Furthermore, her renal function had deteriorated to renal failure within a decade. Finally, she received peritoneal dialysis and renal transplantation. We present the oculocerebrorenal phenotype of Lowe syndrome in a female patient with reduced activity of IPP-5P without OCRL gene mutation.

Nguyen et al. find that the PI(4)P phosphatase Sac2 localizes to insulin granules, where it controls granule docking to the plasma membrane. Loss of Sac2 results in impaired insulin secretion, and Sac2 mRNA levels are reduced in type 2 diabetes., Insulin granule biogenesis involves transport to, and stable docking at, the plasma membrane before priming and fusion. Defects in this pathway result in impaired insulin secretion and are a hallmark of type 2 diabetes. We now show that the phosphatidylinositol 4-phosphate phosphatase Sac2 localizes to insulin granules in a substrate-dependent manner and that loss of Sac2 results in impaired insulin secretion. Sac2 operates upstream of granule docking, since loss of Sac2 prevented granule tethering to the plasma membrane and resulted in both reduced granule density and number of exocytic events. Sac2 levels correlated positively with the number of docked granules and exocytic events in clonal β cells and with insulin secretion in human pancreatic islets, and Sac2 expression was reduced in islets from type 2 diabetic subjects. Taken together, we identified a phosphoinositide switch on the surface on insulin granules that is required for stable granule docking at the plasma membrane and impaired in human type 2 diabetes.

Marinesco-Sjögren syndrome is a rare human disorder caused by biallelic mutations in SIL1 characterized by cataracts in infancy, myopathy and ataxia, symptoms which are also associated with a novel disorder caused by mutations in INPP5K. While these phenotypic similarities may suggest commonalties at a molecular level, an overlapping pathomechanism has not been established yet. In this study, we present six new INPP5K patients and expand the current mutational and phenotypical spectrum of the disease showing the clinical overlap between Marinesco-Sjögren syndrome and the INPP5K phenotype. We applied unbiased proteomic profiling on cells derived from Marinesco-Sjögren syndrome and INPP5K patients and identified alterations in d-3-PHGDH as a common molecular feature. d-3-PHGDH modulates the production of l-serine and mutations in this enzyme were previously associated with a neurological phenotype, which clinically overlaps with Marinesco-Sjögren syndrome and INPP5K disease. As l-serine administration represents a promising therapeutic strategy for d-3-PHGDH patients, we tested the effect of l-serine in generated sil1, phgdh and inpp5k a+b zebrafish models, which showed an improvement in their neuronal phenotype. Thus, our study defines a core phenotypical feature underpinning a key common molecular mechanism in three rare diseases and reveals a common and novel therapeutic target for these patients.

The phosphoinositide 3-kinase (PI3K)/AKT signalling pathway is hyperactivated in ~70% of breast cancers. Class I PI3K generates PtdIns(3,4,5)P3 at the plasma membrane in response to growth factor stimulation, leading to AKT activation to drive cell proliferation, survival and migration. PTEN negatively regulates PI3K/AKT signalling by dephosphorylating PtdIns(3,4,5)P3 to form PtdIns(4,5)P2. PtdIns(3,4,5)P3 can also be hydrolysed by the inositol polyphosphate 5-phosphatases (5-phosphatases) to produce PtdIns(3,4)P2. Interestingly, while PTEN is a bona fide tumour suppressor and is frequently mutated/lost in breast cancer, 5-phosphatases such as PIPP, SHIP2 and SYNJ2, have demonstrated more diverse roles in regulating mammary tumourigenesis. Reduced PIPP expression is associated with triple negative breast cancers and reduced relapse-free and overall survival. Although PIPP depletion enhances AKT phosphorylation and supports tumour growth, this also inhibits cell migration and metastasis in vivo, in a breast cancer oncogene-driven murine model. Paradoxically, SHIP2 and SYNJ2 are increased in primary breast tumours, which correlates with invasive disease and reduced survival. SHIP2 or SYNJ2 overexpression promotes breast tumourigenesis via AKT-dependent and independent mechanisms. This review will discuss how PTEN, PIPP, SHIP2 and SYNJ2 distinctly regulate multiple functional targets, and the mechanisms by which dysregulation of these distinct phosphoinositide phosphatases differentially affect breast cancer progression.

Hormesis describes a biphasic dose-response relationship generally characterized by a low-dose excitement and a high-dose inhibition. This phenomenon has been observed in the regulation of cell, organ, and organismic level. However, hormesis has not reported in oocytes. In this study, we observed, for the first time, hormetic responses of PIPP levels in oocytes by inhibitor of Akt1 or PKCδ. The expression of PIPP was detected by qPCR, immunofluorescent (IF), and Western Blot (WB). To observe the changes of PIPP levels, we used the inhibitors against pAkt1 (Ser473) or PKCδ, SH-6 or sotrastaurin with low and/or high-dose, treated GV oocytes and cultured for 4 h, respectively. The results showed that PIPP expression was significantly enhanced when oocytes were treated with SH-6 or sotrastaurin 10 μM, but decreased with SH-6 or sotrastaurin 100 μM. We also examined the changes of PIPP levels when GV oocytes were treated with exogenous PtdIns(3,4,5)P3 or LY294002 for 4 h. Our results showed that PIPP level was enhanced much higher under the treatment of 0.1 μM PtdIns(3,4,5)P3 than that of 1 μM PtdIns(3,4,5)P3, which is consistent with the changes of PIPP when oocytes were treated with inhibitors of pAkt1 (Ser473) or PKCδ. In addition, with PIPP siRNA, we detected that down-regulated PIPP may affect distributions of Akt, Cdc25, and pCdc2 (Tyr15). Taken together, these results show that the relationships between PIPP and Akt may follow the principle of hormesis and play a key role during release of diplotene arrest in mouse oocytes.

INPP5K (Inositol Polyphosphate 5-Phosphatase K, or SKIP (for Skeletal muscle and Kidney enriched Inositol Phosphatase) is a member of the phosphoinositide 5-phosphatases family. Its protein structure is comprised of a N-terminal catalytic domain which hydrolyses both PtdIns(4,5)P2 and PtdIns(3,4,5)P3, followed by a SKICH domain at the C-terminus which is responsible for protein-protein interactions and subcellular localization of INPP5K. Strikingly, INPP5K is mostly concentrated in the endoplasmic reticulum, although it is also detected at the plasma membrane, in the cytosol and the nucleus. Recently, mutations in INPP5K have been detected in patients with a rare form of autosomal recessive congenital muscular dystrophy with cataract, short stature and intellectual disability. INPP5K functions extend from control of insulin signaling, endoplasmic reticulum stress response and structural integrity, myoblast differentiation, cytoskeleton organization, cell adhesion and migration, renal osmoregulation, to cancer. The goal of this review is thus to summarize and comment recent and less recent data in the literature on INPP5K, in particular on the structure, expression, intracellular localization, interactions and functions of this specific member of the 5-phosphatases family.

Rab5 is required for macropinosome formation, but its site and mode of action remain unknown. We report that Rab5 acts at the plasma membrane, downstream of ruffling, to promote macropinosome sealing and scission. Dominant-negative Rab5, which obliterates macropinocytosis, had no effect on the development of membrane ruffles. However, Rab5-containing vesicles were recruited to circular membrane ruffles, and soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE)-dependent endomembrane fusion was necessary for the completion of macropinocytosis. This fusion event coincided with the disappearance of PtdIns(4,5)P2 that accompanies macropinosome closure. Counteracting the depletion of PtdIns(4,5)P2 by expression of phosphatidylinositol-4-phosphate 5-kinase impaired macropinosome formation. Importantly, we found that the removal of PtdIns(4,5)P2 is dependent on Rab5, through the Rab5-mediated recruitment of the inositol 5-phosphatases OCRL and Inpp5b, via APPL1. Knockdown of OCRL and Inpp5b, or APPL1, prevented macropinosome closure without affecting ruffling. We therefore propose that Rab5 is essential for the clearance of PtdIns(4,5)P2 needed to complete the scission of macropinosomes or to prevent their back-fusion with the plasmalemma.

Vesicular traffic and membrane contact sites between organelles enable the exchange of proteins, lipids, and metabolites. Recruitment of tethers to contact sites between the endoplasmic reticulum (ER) and the plasma membrane is often triggered by calcium. Here we reveal a function for calcium in the repression of cholesterol export at membrane contact sites between the ER and the Golgi complex. We show that calcium efflux from ER stores induced by inositol-triphosphate [IP3] accumulation upon loss of the inositol 5-phosphatase INPP5A or receptor signaling triggers depletion of cholesterol and associated Gb3 from the cell surface, resulting in a blockade of clathrin-independent endocytosis (CIE) of Shiga toxin. This phenotype is caused by the calcium-induced dissociation of oxysterol binding protein (OSBP) from the Golgi complex and from VAP-containing membrane contact sites. Our findings reveal a crucial function for INPP5A-mediated IP3 hydrolysis in the control of lipid exchange at membrane contact sites. The interplay between non-vesicular lipid transport, calcium signaling, and membrane dynamics is unclear. Here, the authors report a function for inositol triphosphate hydrolysis by the inositol 5-phosphatase INPP5A in controlling lipid exchange at interorganelle membrane contact sites between the endoplasmic reticulum and Golgi.

Phosphatidylinositol 4,5-bisphosphate (PI(4,5)P

SH2 domain-containing inositol 5'-phosphatase (SHIP) has critical functions in regulating signal transduction. In additional to its lipid phosphatase activity, SHIP engages in multiple protein-protein interactions, which can serve to localize either SHIP or its binding partners to a particular subcellular domain. Knock-out and knock-down studies have elucidated that SHIP negatively regulates the accumulation of F-actin in leukocytes, usually resulting in inhibition of actin dependent cellular activities such as spreading and migration. Here, we demonstrate that overexpression of SHIP inhibits B cell antigen receptor (BCR)-mediated cell spreading in murine and human B cell lines. B cell stimulation via the BCR or pervanadate induces an interaction between SHIP and Nck, an adaptor protein known to promote actin polymerization. Using a fluorescence recovery after photobleaching (FRAP) assay, we demonstrate that overexpression of SHIP slows F-actin dynamics in BCR-stimulated B cells and this can be overcome by co-overexpression of Nck. Our data supports a role for SHIP in limiting actin turnover and suggests it may do so in part by sequestering Nck.

Liver cancer is a devastating disease for humans with poor prognosis. Although the survival rate of patients with liver cancer has improved in the past decades, the recurrence and metastasis of liver cancer are still obstacles for us. Inositol polyphosphate-5-phosphatase K (INPP5K) belongs to the family of phosphoinositide 5-phosphatases (PI 5-phosphatases), which have been reported to be associated with cell migration, polarity, adhesion, and cell invasion, especially in cancers. However, there have been few studies on the correlation of INPP5K and liver cancer. In this study, we explored the prognostic significance of INPP5K in liver cancer through bioinformatics analysis of data collected from The Cancer Genome Atlas (TCGA) database. Chi-square and Fisher exact tests were used to evaluate the relationship between INPP5K expression and clinical characteristics. Our results showed that low INPP5K expression was correlated with poor outcomes in liver cancer patients. Univariate and multivariate Cox analyses demonstrated that low INPP5K mRNA expression played a significant role in shortening overall survival (OS) and relapse-free survival (RFS), which might serve as the useful biomarker and prognostic factor for liver cancer. In conclusion, low INPP5K mRNA expression is an independent risk factor for poor prognosis in liver cancer.

Thirty-six years after the publication of the important article by Busa and Nuccitelli on the variability of intracellular pH (pHi) and the interdependence of pHi and intracellular Ca2+ concentration ([Ca2+]i), little research has been carried out on pHi and calcium signaling. Moreover, the results appear to be contradictory. Some authors claim that the increase in [Ca2+]i is due to a reduction in pHi, others that it is caused by an increase in pHi. The reasons for these conflicting results have not yet been discussed and clarified in an exhaustive manner. The idea that variations in pHi are insignificant, because cellular buffers quickly stabilize the pHi, may be a limiting and fundamentally wrong concept. In fact, it has been shown that protons can move and react in the cell before they are neutralized. Variations in pHi have a remarkable impact on [Ca2+]i and hence on some of the basic biochemical mechanisms of calcium signaling. This paper focuses on the possible triggering role of protons during their short cellular cycle and it suggests a new hypothesis for an IP3 proton dependent mechanism of action.

Congenital heart disease (CHD) with extracardiac malformations (EM) is the most common multiple malformation, resulting from the interaction between genetic abnormalities and environmental factors. Most studies have attributed the causes of CHD with EM to chromosomal abnormalities. However, multi‐system dysplasia is usually caused by both genetic mutations and epigenetic dysregulation. The epigenetic mechanisms underlying the pathogenesis of CHD with EM remain unclear. In this study, we investigated the mechanisms of imprinting alterations, including those of the Small nuclear ribonucleoprotein polypeptide N (SNRPN), PLAG1 like zinc finger 1 (ZAC1) and inositol polyphosphate‐5‐phosphatase F (INPP5F) genes, in the pathogenesis of CHD with EM. The methylation levels of SNRPN, ZAC1, and INPP5F genes were analysed by the MassARRAY platform in 24 children with CHD with EM and 20 healthy controls. The expression levels of these genes were detected by real‐time polymerase chain reaction (PCR). The correlation between methylation regulation and gene expression was confirmed using 5‐azacytidine (5‐Aza) treated cells. The methylation levels of SNRPN and ZAC1 genes were significantly increased in CHD with EM, while that of INPP5F was decreased. The methylation alterations of these genes were negatively correlated with expression. Risk analysis showed that abnormal hypermethylation of SNRPN and ZAC1 resulted in 5.545 and 7.438 times higher risks of CHD with EM, respectively, and the abnormal hypomethylation of INPP5F was 8.38 times higher than that of the control group. We concluded that abnormally high methylation levels of SNRPN and ZAC1 and decreased levels of INPP5F imply an increased risk of CHD with EM by altering their gene functions. This study provides evidence of imprinted regulation in the pathogenesis of multiple malformations.

Objective To screen a standard homogenous cDNA library of human gastric mucosal epithelium with yeast two-hybrid system and find the proteins that interact with Src-homology 2-containing inositol 5-phosphatase 2 (SHIP2). Methods Using the yeast two-hybrid system, P1 (SH2+5-Ptase) and P2 (PRD+SAM) segments of SHIP2 were used as bait proteins to screen the proteins that bind to SHIP2 from the homogenous cDNA library of human gastric mucosal epithelium. The selected interacting proteins of SHIP2 were verified by co-immunoprecipitation assay. Results A total of 39 positive clones were selected and sequenced for alignment analysis. It was verified that PHB interacted with SHIP2 by reductive hybridization and co-immunoprecipitation assays. Conclusion PHB, the interacting protein of SHIP2 was screened by yeast two-hybrid system from the homogenous cDNA library of human gastric mucosal epithelium.

Inositol polyphosphate 5-phosphatases (5PTases) function in inositol signaling by regulating the catabolism of phosphoinositol derivatives. Previous reports showed that 5PTases play a critical role in plant development and stress responses. In this study, we identified a novel 5PTase gene, Gs5PTase8, from the salt-tolerance locus of chromosome 3 in wild soybean (Glycine soja). Gs5PTase8 is highly up-regulated under salt treatment. It is localized in the nucleus and plasma membrane with a strong signal in the apoplast. Ectopic expression of Gs5PTase8 significantly increased salt tolerance in transgenic BY-2 cells, soybean hairy roots and Arabidopsis, suggesting Gs5PTase8 could increase salt tolerance in plants. The overexpression of Gs5PTase8 significantly enhanced the activities of catalase and ascorbate peroxidase under salt stress. The seeds of Gs5PTase8-transgenic Arabidopsis germinated earlier than the wild type under abscisic acid treatment, indicating Gs5PTase8 would alter ABA sensitivity. Besides, transcriptional analyses showed that the stress-responsive genes, AtRD22, AtRD29A and AtRD29B, were induced with a higher level in the Gs5PTase8-transgenic Arabidopsis plants than in the wild type under salt stress. These results reveal that Gs5PTase8 play a positive role in salt tolerance and might be a candidate gene for improving soybean adaptation to salt stress.

The effects of sodium citrate (SC), sodium acetate (SA) and sodium tartrate (ST) spraying on mung bean germination were investigated. Exogenous SC, ST and SA treatments significantly reduced the phytic acid content and increased the antioxidant enzyme activities. In this study, an iTRAQ-based proteomic approach was employed to explore the proteomes of mung bean sprouts, and 81, 101 and 90 differentially expressed proteins were identified in 4-day-old SC-, SA- and ST-treated mung bean sprouts, with 38 proteins present in all samples. Functional classification analysis showed that most of the differentially expressed proteins in mung bean sprouts subjected to the three treatments were involved in carbohydrate and energy metabolism. The inhibitory effect of the SA treatment was probably due to impairments in protein biosynthesis, whereas enhanced energy metabolism, accelerated reserve hydrolysis and protein processing were very important strategies for growth stimulation in response to ST and SC treatments.

A typical hallmark of diabetic kidney disease (DKD) is an excessive deposition of extracellular matrix (ECM) in the glomerulus and renal tubulointerstitium, leading to glomerulosclerosis and tubular interstitial fibrosis. Src homology 2 domain-containing inositol 5'-phosphatase (SHIP) is a negative regulator of the phosphatidylinositol 3-kinase/protein kinase B (PI3K/Akt) signaling. Here, we investigated the effect of SHIP on ECM deposition in diabetic mice and high glucose-stimulated human renal tubular epithelial cells (HK2 cells). The decreased SHIP and increased phospho-Akt (Ser 473, Thr 308) were found in the renal tubular cells of diabetic mice, which were accompanied by overexpression of transforming growth factor-β1 (TGF-β1), α-smooth muscle actin (α-SMA), and secreted collagen type 3 (Col 3) and a low expression of E-cadherin compared to that in normal mice. In vitro research revealed that high glucose-attenuated SHIP expression accompanied the activation of the PI3K/Akt signaling and ECM production. Knocking down SHIP in HK2 cells caused an increase in the levels of phospho-Akt (Ser 473), phospho-Akt (Thr 308), TGF-β1, α-SMA, and secreted Col 3 and a decrease in E-cadherin. Again, either the M90-SHIP plasmid or the PI3K/Akt pathway inhibitor LY294002 could significantly prevent the high glucose-induced increase in TGF-β1, α-SMA, and secreted Col 3 and decreased E-cadherin. Furthermore, we confirmed that inhibition of the TGF-β1 pathway with SB431542 blocked the effect of SHIP knockdown on ECM production in HK2 cells. In summary, our study suggests that decreased SHIP mediates high glucose-induced TGF-β1 upregulation and ECM deposition through activation of the PI3K/Akt pathway in renal tubular cells. J. Cell. Biochem. 118: 2271-2284, 2017. © 2017 Wiley Periodicals, Inc.

Background Inositol polyphosphate-5-phosphatase (INPP5A) has been shown to play a role in the progression of actinic keratosis to cutaneous squamous cell carcinoma (cSCC) and the progression of localized disease to metastatic disease. Currently, no cSCC biomarkers are able to risk stratify recurrent and metastatic disease. Objective To determine the prognostic value of INPP5A expression in cSCC recurrent and metastatic disease. Methods We conducted a multicenter, single-institutional, retrospective cohort study within the Mayo Clinic Health System on the use of immunohistochemical staining to examine cSCC INPP5A protein expression in primary tumors and recurrent and metastatic disease. Dermatologists and dermatopathologists were blinded to outcome. Results Low staining expression of INPP5A in recurrent and metastatic disease tumors was associated with poor overall survival (OS) (31.0 months for low versus 62.0 months for high expression; P = .0272). A composite risk score (calculated as score of primary tumor + score of recurrent or metastatic disease tumor, with tumors with high expression scoring a zero and low expression a 1, score range 0-2) of 0 was predictive of improved OS compared with a composite risk score of ≥1 (hazard ratio 0.42, 95% confidence interval 0.21-0.84; P = .0113). Limitations This is a multicenter but single institution study of a white population. Conclusion Loss of INPP5A expression predicts poor OS in recurrent and metastatic disease of cSCC.

Mutations of the inositol 5-phosphatase OCRL cause Lowe syndrome (LS), characterized by congenital cataract, low IQ, and defective kidney proximal tubule resorption. A key subset of LS mutants abolishes OCRL’s interactions with endocytic adaptors containing F&H peptide motifs. Converging unbiased methods examining human peptides and the unicellular phagocytic organism Dictyostelium discoideum reveal that, like OCRL, the Dictyostelium OCRL orthologue Dd5P4 binds two proteins closely related to the F&H proteins APPL1 and Ses1/2 (also referred to as IPIP27A/B). In addition, a novel conserved F&H interactor was identified, GxcU (in Dictyostelium) and the Cdc42-GEF FGD1-related F-actin binding protein (Frabin) (in human cells). Examining these proteins in D. discoideum, we find that, like OCRL, Dd5P4 acts at well-conserved and physically distinct endocytic stations. Dd5P4 functions in coordination with F&H proteins to control membrane deformation at multiple stages of endocytosis and suppresses GxcU-mediated activity during fluid-phase micropinocytosis. We also reveal that OCRL/Dd5P4 acts at the contractile vacuole, an exocytic osmoregulatory organelle. We propose F&H peptide-containing proteins may be key modifiers of LS phenotypes.

Inositol polyphosphate 5-phosphatase (5PTase), a key enzyme that hydrolyzes the 5` position of the inositol ring, has essential functions in growth, development, and stress responses in plants, yeasts, and animals. However, the evolutionary history and patterns of 5PTases have not been examined systematically. Here, we report a comprehensive molecular evolutionary analysis of the 5PTase gene family and define four groups. These four groups are different from former classifications, which were based on in vitro substrate specificity. Most orthologous groups appear to be conserved as single or low-copy genes in all lineages in Groups II&ndash, IV, whereas 5PTase genes in Group I underwent several duplication events in angiosperm, resulting in multiple gene copies. Whole-genome duplication (WGD) was the main mechanism for 5PTase duplications in angiosperm. Plant 5PTases have more members than that of animals, and most plant 5PTase genes appear to have evolved under strong purifying selection. The paralogs have diverged in substrate specificity and expression pattern, showing evidence of selection pressure. Meanwhile, the increase in 5PTases and divergences in sequence, expression, and substrate might have contributed to the divergent functions of 5PTase genes, allowing the angiosperms to successfully adapt to a great number of ecological niches.

The phosphoinositide 3-kinase (PI3K) generated lipid signals, PtdIns(3,4,5) P 3 and PtdIns(3,4) P 2, are both required for the maximal activation of the serine/threonine kinase proto-oncogene Akt. The inositol polyphosphate 5-phosphatases (5-phosphatases) hydrolyse the 5-position phosphate from the inositol head group of PtdIns(3,4,5) P 3 to yield PtdIns(3,4) P 2. Extensive work has revealed several 5-phosphatases inhibit PI3K-driven Akt signalling, by decreasing PtdIns(3,4,5) P 3 despite increasing cellular levels of PtdIns(3,4) P 2. The roles that 5-phosphatases play in suppressing cell proliferation and transformation are slow to emerge; however, the 5-phosphatase PIPP [proline-rich inositol polyphosphate 5-phosphatase; inositol polyphosphate 5-phosphatase ( INPP5J )] has recently been identified as a putative tumour suppressor in melanoma and breast cancer and SHIP1 [SH2 (Src homology 2)-containing inositol phosphatase 1] inhibits haematopoietic cell proliferation. INPP5E regulates cilia stability and INPP5E mutations have been implicated ciliopathy syndromes. This review will examine 5-phosphatase regulation of PI3K/Akt signalling, focussing on the role PtdIns(3,4,5) P 3 5-phosphatases play in developmental diseases and cancer. * 3AC, : 3-a-aminocholestane; 5-phosphatases, : inositol polyphosphate 5-phosphatases; AURKA, : aurora kinase A; BJAB, : human B-cell lymphoma cell line; BMMC, : bone marrow-derived mast cells; CHO, : Chinese hamster ovary; EGF, : epidermal growth factor; ENU, : N -ethyl- N -nitrosourea; ER, : estrogen receptor; FoxO, : forkhead box, class O; GLUT4, : glucose transporter type 4; Gpr161, : G-protein-coupled receptor 161; HEK, : human embryonic kidney; IGF-1, : insulin-like growth factor-1; IL-3, : interleukin-3; LPS, : lipopolysaccharide; MEF, : mouse embryonic fibroblast; MM, : multiple myeloma; mTORC, : mammalian target of rapamycin complex; NFAT, : nuclear factor of activated T cells; OCRL, : oculocerebrorenal syndrome of Lowe; Pak1, : P21-activated kinase 1; PDK1, : phosphoinositide-dependent kinase 1; PH, : pleckstrin homology; 1PIE, : (2-phenyl-benzo[ h ]quinolin-4-yl)-[2]piperidyl-methanol hydrochloride; 2PIQ, : 1-[(chlorophenyl)methyl]-2-methyl-5-(methylthio)-1H-indole-3-ethanamine hydrochloride; 6PTQ, : (2-adamantan-1-yl-6,8-dichloro-quinolin-4-yl)-pyridin-2-yl-methanol hydrochloride; PI3K, : phosphoinositide 3-kinase; PIPP, : proline-rich inositol polyphosphate 5-phosphatase; PRAS40, : proline-rich Akt substrate of 40 kDa; PTEN, : phosphatase and tensin homologue deleted on chromosome 10; PyMT, : polyoma middle T; Rheb, : Ras homologue enriched in brain; RhoGAP, : Rho GTP-ase activating protein; SAG, : smoothened agonist; Shh, : sonic hedgehog; SHIP, : SH2-containing inositol phosphatase; SKICH, : SKIP carboxy homology; SKIP, : skeletal muscle- and kidney-enriched inositol phosphatase; TNFα, : tumour necrosis factor α; TSC, : tuberous sclerosis; TULP3, : Tubby-like protein 3

Crohn's disease (CD) is associated with a dysregulated immune response to commensal micro-organisms in the intestine. Mice deficient in inositol polyphosphate 5'-phosphatase D (INPP5D, also known as SHIP) develop intestinal inflammation resembling that of patients with CD. SHIP is a negative regulator of PI3Kp110α activity. We investigated mechanisms of intestinal inflammation in Inpp5d(-/-) mice (SHIP-null mice), and SHIP levels and activity in intestinal tissues of subjects with CD.We collected intestines from SHIP-null mice, as well as Inpp5d(+/+) mice (controls), and measured levels of cytokines of the interleukin 1 (IL1) family (IL1α, IL1β, IL1ra, and IL6) by enzyme-linked immunosorbent assay. Macrophages were isolated from lamina propria cells of mice, IL1β production was measured, and mechanisms of increased IL1β production were investigated. Macrophages were incubated with pan-phosphatidylinositol 3-kinase inhibitors or PI3Kp110α-specific inhibitors. Some mice were given an antagonist of the IL1 receptor; macrophages were depleted from ilea of mice using clodronate-containing liposomes. We obtained ileal biopsies from sites of inflammation and peripheral blood mononuclear cells (PBMCs) from treatment-naïve subjects with CD or without CD (controls), and measured SHIP levels and activity. PBMCs were incubated with lipopolysaccharide and adenosine triphosphate, and levels of IL1β production were measured.Inflamed intestinal tissues and intestinal macrophages from SHIP-null mice produced higher levels of IL1B and IL18 than intestinal tissues from control mice. We found PI3Kp110α to be required for macrophage transcription of Il1b. Macrophage depletion or injection of an IL1 receptor antagonist reduced ileal inflammation in SHIP-null mice. Inflamed ileal tissues and PBMCs from patients with CD had lower levels of SHIP protein than controls (P.0001 and P.0002, respectively). There was an inverse correlation between levels of SHIP activity in PBMCs and induction of IL1β production by lipopolysaccharide and adenosine triphosphate (R(2) = .88).Macrophages from SHIP-deficient mice have increased PI3Kp110α-mediated transcription of Il1b, which contributes to spontaneous ileal inflammation. SHIP levels and activity are lower in intestinal tissues and peripheral blood samples from patients with CD than controls. There is an inverse correlation between SHIP activity and induction of IL1β production by lipopolysaccharide and adenosine triphosphate in PBMCs. Strategies to reduce IL1B might be developed to treat patients with CD found to have low SHIP activity.

Highlight We report two novel reduced-height maize mutants caused by mutations within a putative inositol polyphosphate 5-phosphatase-encoding gene. Auxin-mediated internode elongation probably requires regulation of inositol and/or phospholipid metabolism., In maize (Zea mays L.), as in other grass species, stem elongation occurs during growth and most noticeably upon the transition to flowering. Genes that reduce stem elongation have been important to reduce stem breakage, or lodging. Stem elongation has been mediated by dwarf and brachytic/brevis plant mutants that affect giberellic acid and auxin pathways, respectively. Maize brevis plant1 (bv1) mutants, first identified over 80 years ago, strongly resemble brachytic2 mutants that have shortened internodes, short internode cells, and are deficient in auxin transport. Here, we characterized two novel bv1 maize mutants. We found that an inositol polyphosphate 5-phosphatase orthologue of the rice gene dwarf50 was the molecular basis for the bv1 phenotype, implicating auxin-mediated inositol polyphosphate and/or phosphoinositide signalling in stem elongation. We suggest that auxin-mediated internode elongation involves processes that also contribute to stem gravitropism. Genes misregulated in bv1 mutants included genes important for cell wall synthesis, transmembrane transport, and cytoskeletal function. Mutant and wild-type plants were indistinguishable early in development, responded similarly to changes in light quality, had unaltered flowering times, and had normal flower development. These attributes suggest that breeding could utilize bv1 alleles to increase crop grain yields.

The protein tyrosine kinase LCK plays a key role in TCR signaling, and its activity is dynamically controlled by the tyrosine kinase C-terminal Src kinase (CSK) and the tyrosine phosphatase CD45. CSK is brought in contiguity to LCK via binding to a transmembrane adaptor known as phosphoprotein associated with glycosphingolipid-enriched microdomains (PAG). The lack of a blatant phenotype in PAG-deficient mice has impeded our understanding of the mechanisms through which PAG exerts its negative-regulatory role in TCR signaling. We used quantitative mass spectrometry and both thymocytes and CD4+ T cells from mice in which a tag for affinity purification was knocked in the gene coding for PAG to determine the composition and dynamics of the multiprotein complexes that are found around PAG over 5 min of activation. Most of the high-confidence interactions that we observed were previously unknown. Using phosphoproteomic analysis, PAG showed low levels of tyrosine phosphorylation in resting primary mouse CD4+ T cells; the levels of tyrosine phosphorylation increased and reached a maximum 2 min after stimulation. Analysis of the dynamics of association of the protein tyrosine phosphatase PTPN22 and lipid phosphatase SHIP-1 with PAG following T cell activation suggests that both cooperate with CSK to terminate T cell activation. Our findings provide a model of the role for PAG in mouse primary CD4+ T cells that is consistent with recent phosphoproteomic studies of the Jurkat T cell line but difficult to reconcile with former biochemical studies indicating that PAG is constitutively phosphorylated in resting T cells and rapidly dephosphorylated once the TCR is engaged.

Recently, inhibition of the SH2-containing inositol 5'-phosphatase 1 (SHIP1) has become an attractive strategy for facilitating engraftment of MHC-I mismatched bone marrow grafts, increasing the number of adult stem cells in vivo, and inducing mobilization of hematopoietic stem cells. Utilizing high-throughput screening, two quinoline small molecules (NSC13480 and NSC305787) that inhibit SHIP1 enzymatic activity were discovered. New syntheses of these inhibitors have been developed which verified the relative stereochemistry of these structures. Utilizing this synthetic route, some analogs of these quinolines have been prepared and tested for their ability to inhibit SHIP. These structure activity studies determined that an amine tethered to the quinoline core is required for SHIP inhibition. SHIP inhibition may explain the antitumor effects of similar quinoline amino alcohols and provides an impetus for further synthetic studies in this class of compounds.

Purpose We aimed to investigate the anti-angiogenic properties of miR-155 via in vitro and in vivo studies. Methods miR-155 was knocked down using lentivirus-mediated RNA interference. The proliferation, migration, and tube formation of human retinal microvascular endothelial cells (HRMECs) were measured using BrdU, Transwell, and Matrigel assays, respectively. An oxygen-induced retinopathy (OIR) model was induced using neonatal C57BL/6J pups. Anti-miR-155 was intravitreally injected on postnatal day 12, and the retinal non-perfused areas and extent of neovascularization were measured on postnatal day 18 using transcardiovascular fluorescein isothiocyanate (FITC)-dextran perfusion and retina sections. A laser-induced choroidal neovascularization (CNV) model was induced in adult C57BL/6J mice. To evaluate the leakage areas, fundus fluorescein angiography was performed on day 14 after anti-miR-155 intravitreal injection. The neovascularization area of the CNV model was also examined in confocal and retina section studies. The expression levels of SHIP1 and p-Akt (Thr308, Ser473, and Thr450) were evaluated both in vitro and in vivo. Results The expression of miR-155 was elevated in HRMECs after treatment with vascular endothelial growth factor (VEGF) and in neovascularized mouse model retinas. Anti-miR-155 lentivirus reduced the VEGF-induced proliferation, migration, and tube formation abilities of HRMECs. Anti-miR-155 attenuated retinal neovascularization in in vivo CNV and OIR models. In VEGF-treated HRMECs and retina neovascularization models, p-Akt (Ser473) was significantly upregulated, while SHIP1 was downregulated. Conversely, the inhibition of miR-155 restored the expression of SHIP1 and reduced the phosphorylation of effectors in the Akt (Ser473) signaling pathway. Conclusions The results revealed that the downregulation of miR-155 attenuated retinal neovascularization via the phosphatidylinositol 3-kinase (PI3K)/Akt pathway.

Indole-3-acetic acid (IAA) conjugation is one of the mechanisms responsible for auxin homeostasis. IAA ester conjugates biosynthesis has been studied during development of maize seeds where IAA-inositol (IAInos) and its glycosidic forms make up about 50 % of its ester conjugates pool. 1-O-indole-3-acetyl-β-d-glucose (IAGlc) synthase and indole-3-acetyl transferase (IAInos synthase) are key enzymes in a two-step pathway of IAInos synthesis. In the first reaction, IAA is glucosylated to a high energy acetal, 1-O-indole-3-acetyl-β-d-glucose by IAGlc synthase, whereas in the second step, IAInos synthase transfers IAA moiety to myo-inositol forming a stable auxin ester, indole-3-acetyl-myo-inositol (IAInos). It should be mentioned that IAGlc synthase catalyzes a reversible reaction with unfavourable equilibrium that delivers IAGlc for favourable transacylation to IAInos. This is the first study where IAGlc synthase and IAInos synthase are simultaneously analyzed by enzymatic activity assay and quantitative RT-PCR in maize seeds at four stages of development (13, 26, 39 and 52 Days After Flowering). Activity of IAGlc/IAInos synthases as well as their expression profiles during seed development were different. While both enzymatic activities and ZmIAIn expression were the highest in seeds at 26 DAF, the highest expression of ZmIAGlc was observed at 13 DAF. Protein gel blot analysis showed that IAInos synthase exists as a mixture of several isoforms at a similar protein level at particular stages of seed development. Neither of other ester conjugates of IAA (IAA-mannose) nor IAA-amino acids were detected at the stages studied. Catalytic activity of l-tryptophan aminotransferase involved in IAA biosynthesis as well as UDPG pyrophosphorylase, synthesizing UDPG as a substrate for IAGlc synthase, were also analyzed. l-tryptophan aminotransferase activity was the highest at 26 DAF. Changes in enzyme activity of UDPG pyrophosphorylase are difficult to interpret. Expression levels of ZmIPS and ZmIPP encoding two enzymes of myo-inositol biosynthesis pathway: inositol-x-phosphate synthase (IPS) and inositol-x-phosphate phosphatase (IPP), respectively, were analyzed. 26 DAF seeds displayed the highest expression level of ZmIPS, whereas transcription of ZmIPP was the highest at 13 DAF.

Inositol polyphosphate 5-phosphatase (INPP5A) has been shown to play a role in development and progression of cutaneous squamous cell carcinoma (cSCC). The goal of the current study was to explore the prognostic value of INPP5A expression in cSCC.A total of 189 cases of actinic keratosis and SCC in 174 patients were identified; clinical and outcome data were abstracted, histopathology was rereviewed, and immunohistochemical staining and interpretation was performed for INPP5A.The majority of tumors (89.4%) had an INPP5A score of 2 or 3. No patients had complete loss of INPP5A. Tumors with an INPP5A score of 1 were more likely to be intermediate- to high-risk tumors (Brigham and Women's Hospital stage ≥T2a 85.0% vs 23.7% [P .0001]) characterized by a larger diameter (2.4 cm vs 1.3 cm [P = .0004]), moderate-to-poor differentiation (86.7% vs 17.6% [P .0001]), and perineural invasion (37.5% vs 5.3%, [P .0001]). An INPP5A score of 1 was associated with a worse 3-year survival (a rate of 42.3% [hazard ratio, 2.81, P = .0006]) and a local metastasis rate of 48.0% (hazard ratio, 4.71; P .0001).Low INPP5A scores are predictive of aggressive tumors and may be a useful adjunct to guide clinical management of cSCC.

This study aimed to exploit the potential therapeutic value of palmatine in treatment of cardiac hypertrophy and the underlying molecular mechanism. Rat hypertrophy model was established by intraperitoneal isoproterenol (ISO) injection. The hypertrophy was evaluated with cardiac hypertrophic parameters, hemodynamic parameters, lipid profile, and non-specific cardiac markers. The animals were intraperitoneally administrated with either palmatine or vehicle. The relative expressions of ANP, BNP, HDAC2, HDAC5, KLF4, and INPP5F transcripts were determined by real-time polymerase chain reaction (PCR). The relative protein levels of HDAC2, HDAC5, KLF4, and INPP5F were analyzed by immunoblotting. Palmatine treatment significantly attenuated ISO-induced hypertrophy in rats and elicited remarkable repressions in ANP, BNP, and HDAC2 transcriptions but not HDAC5. The downstream effector genes KLF4 and INPP5F were greatly restored in a dose-dependent manner in response to palmatine treatment. Our data demonstrated that palmatine possessed promising therapeutic potential against hypertrophy, which was mediated by modulation of HDAC2-KLF4/INPP5F pathway.

Many self-reactive B cells exist in the periphery in a rapidly reversible state of unresponsiveness referred to as anergy. Reversibility of anergy indicates that chronically occupied BCR must transduce non-durable regulatory signals that maintain unresponsiveness. Consistent with such a mechanism, studies of immunoglobulin transgenic, as well as naturally occurring polyclonal autoreactive B cells demonstrate activation of the inositol 5-phosphatase SHIP-1 in anergic cells, and low affinity chromatin autoantigen-reactive B cells have been shown to require expression of this phosphatase to maintain anergy. However, it has been reported that anergy of B cells recognizing high affinity soluble antigen may not require SHIP-1, and is instead mediated by upregulation of the inositol 3-phosphatase PTEN. To further explore this apparent difference in mechanism we analyzed the effect of B cell-targeted SHIP-1 deletion on immune tolerance of high affinity anti-HEL B cells in mice expressing soluble HEL (MD4.ML-5). We report that SHIP-1 functions to dampen responses of naïve and low-dose antigen-primed B cells in vitro, and is required for induction of B cell tolerance. Thus, while anergy of B cells reactive with low affinity and likely polyvalent chromatin antigens is maintained by activation of inhibitory signaling circuitry involving SHIP-1, anergy of B cells recognizing soluble self antigen with high affinity also requires increased activity of SHIP-1.