Inhibition of the Inositol Kinase Itpkb Augments Calcium Signaling in Lymphocytes and Reveals a Novel Strategy to Treat Autoimmune Disease

The autophagy-lysosome pathway: a potential target in the chemical and gene therapeutic strategies for Parkinson's disease

Parkinson's disease is a common neurodegenerative disease with movement disorders associated with the intracytoplasmic deposition of aggregate proteins such as α-synuclein in neurons. As one of the major intracellular degradation pathways, the autophagy-lysosome pathway plays an important role in eliminating these proteins. Accumulating evidence has shown that upregulation of the autophagy-lysosome pathway may contribute to the clearance of α-synuclein aggregates and protect against degeneration of dopaminergic neurons in Parkinson's disease. Moreover, multiple genes associated with the pathogenesis of Parkinson's disease are intimately linked to alterations in the autophagy-lysosome pathway. Thus, this pathway appears to be a promising therapeutic target for treatment of Parkinson's disease. In this review, we briefly introduce the machinery of autophagy. Then, we provide a description of the effects of Parkinson's disease-related genes on the autophagy-lysosome pathway. Finally, we highlight the potential chemical and genetic therapeutic strategies targeting the autophagy-lysosome pathway and their applications in Parkinson's disease.

The protective role of interaction between vitamin D, sex hormones and calcium in multiple sclerosis

Multiple sclerosis (MS) is a neurological disorder that causes disability and paralysis, especially among young adults. Although interactions of several factors, such as viral infections, autoimmunity, genetic and environmental factors, performance a role in the beginning and progression of the disease, the exact cause of MS is unknown to date. Different immune cells such as Th1 and Th17 play an impressive role in the immunopathogenesis of MS, while, regulatory cells such as Th2 and Treg diminish the severity of the illness. Sex hormones have a vital role in many autoimmune disorders, including multiple sclerosis. Testosterone, estrogen and progesterone have various roles in the progress of MS, which higher prevalence of disease in women and more severe in men reveals the importance of sex hormones' role in this disease. Vitamin D after chemical changes in the body, as an active hormone called calcitriol, plays an important role in regulating immune responses and improves MS by modulating the immune system. The optimum level of calcium in the body with vitamin D modulates immune responses and calcium as an essential ion in the body plays a key role in the treatment of autoimmune diseases. The interaction between vitamin D and sex hormones has protective and therapeutic effects against MS and functional synergy between estrogen and calcitriol occurs in disease recovery. Moreover, vitamin D and calcium interact with each other to regulate the immune system and shift them to anti-inflammatory responses.

Transcriptome and Animal Model Integration Reveals Inhibition of Calcium Homeostasis-Associated Gene ITPKB Alleviates Amyloid Plaque Deposition

Alzheimer's disease (AD) is a severe neurological illness that causes memory loss and is a global problem. The calcium hypothesis recently steadily evolved in AD. The prospective targets for calcium homeostasis therapy, however, are limited, and gene expression-level research connected to calcium homeostasis in AD remains hazy. In this study, we analyzed the microarray dataset (GSE132903) taken from the Gene Expression Omnibus (GEO) database to investigate calcium homeostasis-related genes for AD. Using immunoblot analysis, we examined the association of ITPKB with inflammation in AD. Additionally, the immunofluorescence technique was employed to assess the impact of pharmacological inhibition of ITPKB on the amyloid-β (Aβ) plaque deposition in APP/PS1 mice. This article's further exploration of calcium homeostasis-related genes has propelled the validation of the calcium homeostasis theory in AD.

Evidence that inositol 1,4,5-trisphosphate 3-kinase and inositol 1,3,4,5-tetrakisphosphate are negative regulators of platelet function

Background

Inositol 1,3,4,5-tetrakisphosphate (IP4) is formed from inositol 1,4,5-trisphosphate (IP3) by IP3 3-kinase (ITPK) in most cells. Its function is unknown but has been suggested to be involved in Ca2+ entry, IP3 regulation, and phosphoinositide 3-kinase antagonism.

Objectives

To better elucidate a function for IP4, we tested a specific inhibitor of ITPK (GNF362) on platelets, the effects of IP4 directly in permeabilized platelets and its effect on phosphatidylinositol 3,4,5-trisphosphate (PIP3) binding to pleckstrin-homology (PH) domain-containing proteins in platelets.

Methods

Human platelets were utilized in whole blood for thrombus formation, in platelet-rich plasma and washed suspensions for aggregation, and for Ca2+ studies, or resuspended in high K+ and low Na+ buffers for permeabilization experiments. Phosphorylation of AKT-Ser473 and Rap1-GTP formation were measured by Western blotting and PIP3 binding using PIP3 beads.

Results

GNF362-enhanced platelet aggregation stimulated by low concentrations of ADP, collagen, thrombin, U46619, and thrombus formation in collagen-coated capillaries. GNF362 induced a transient elevation of Ca2+ concentration, elevated basal levels of IP3, and enhanced the peak height of Ca2+ elevated by agonists. In permeabilized platelets, IP4 inhibited GTPγS induced formation of AKT-Ser473 phosphorylation and platelet aggregation. IP4 reduced GTPγS-stimulated Rap1-GTP levels and potently reduced extraction of RASA3 and BTK by PIP3 beads.

Conclusion

ITPK and IP4 are negative regulators of platelet function. IP4 regulation of PH domain-containing proteins may represent a pathway by which platelet activation may be controlled during thrombosis.

A genome-wide association study of chronic spontaneous urticaria risk and heterogeneity

BACKGROUND

Chronic spontaneous urticaria (CSU) is a dermatologic condition characterized by spontaneous, pruritic hives and/or angioedema that persists for 6 weeks or longer with no identifiable trigger. Antihistamines and second-line therapies such as omalizumab are effective for some CSU patients, but others remain symptomatic, with significant impact on quality of life. This variable response to treatment and autoantibody levels across patients highlight clinically heterogeneous subgroups.

OBJECTIVE

We aimed to highlight pathways involved in CSU by investigating the genetics of CSU risk and subgroups.

METHODS

We performed a genome-wide association study (GWAS) of 679 CSU patients and 4446 controls and a GWAS of chronic urticaria (CU)-index, which measures IgG autoantibodies levels, by comparing 447 CU index-low to 183 CU index-high patients. We also tested whether polygenic scores for autoimmune-related disorders were associated with CSU risk and CU index.

RESULTS

We identified 2 loci significantly associated with disease risk. The strongest association mapped to position 56 of HLA-DQA1 (P = 1.69 × 10-9), where the arginine residue was associated with increased risk (odds ratio = 1.64). The second association signal colocalized with expression-quantitative trait loci for ITPKB in whole blood (Pcolocalization = .997). The arginine residue at position 56 of HLA-DQA1 was also associated with increased risk of CU index-high (P = 6.15 × 10-5, odds ratio = 1.86), while the ITKPB association was not (P = .64). Polygenic scores for 3 autoimmune-related disorders (hypothyroidism, type 1 diabetes, and vitiligo) were associated with CSU risk and CU index (P < 2.34 × 10-3, odds ratio > 1.72).

CONCLUSION

A GWAS of CSU identified 2 genome-wide significant loci, highlighting the shared genetics between CU index and autoimmune disorders.

A novel signature of autophagy-related immunophenotyping biomarkers in osteoarthritis

AIMS

We aimed to provide an autophagy-related signature to seek immunophenotyping biomarkers in osteoarthritis (OA).

MATERIALS AND METHODS

Microarray expression profiling of OA subchondral bone samples and screening of an autophagy database for autophagy-related differentially expressed genes (au-DEGs) between OA and normal samples were performed. A weighted gene co-expression network analysis (WGCNA) was constructed using au-DEGs to identify key modules significantly associated with clinical information of OA samples. OA-related autophagy hub genes were identified based on the connectivity with the phenotypes of genes in key modules and the protein-protein interaction (PPI) network in which the genes in the modules are involved, followed by feasibility verification of autophagy hub genes by bioinformatics analysis and biological experiments.

KEY FINDINGS

We screened 754 au-DEGs between OA and control samples, and co-expression networks were constructed using au-DEGs. Three OA-related autophagy hub genes (HSPA5, HSP90AA1, and ITPKB) were identified. Based on the hub gene expression profiles, OA samples were divided into two clusters with significantly different expression profiles and distinct immunological features, and the three hub genes were significantly differentially expressed between the clusters. Differences in hub genes between OA and control samples regarding sex, age, and grades of OA were examined using external datasets and experimental validation.

SIGNIFICANCE

Three autophagy-related markers of OA were identified using bioinformatics methods, and these markers may be useful for the autophagy-related immunophenotyping of OA. The present data may facilitate the diagnosis of OA, as well as the design of immunotherapies and individualized medical treatments.

The actin bundling activity of ITPKA mainly accounts for its migration-promoting effect in lung cancer cells

Expression of Ins(1,4,5)P3-kinase-A (ITPKA), the neuronal isoform of Ins(1,4,5)P3-kinases, is up-regulated in many tumor types. In particular, in lung cancer cells this up-regulation is associated with bad prognosis and it has been shown that a high level of ITPKA increases migration and invasion of lung cancer cell lines. However, since ITPKA exhibits actin bundling and Ins(1,4,5)P3-kinase activity, it was not clear which of these activities account for ITPKA-promoted migration and invasion of cancer cells. To address this issue, we inhibited endogenous actin bundling activity of ITPKA in lung cancer H1299 cells by overexpressing the dominant negative mutant ITPKAL34P. Analysis of actin dynamics in filopodia as well as wound-healing migration revealed that ITPKAL34P inhibited both processes. Moreover, the formation of invasive protrusions into collagen I was strongly blocked in cells overexpressing ITPKAL34P. Furthermore, we found that ATP stimulation slightly but significantly (by 13%) increased migration of cells overexpressing ITPKA while under basal conditions up-regulation of ITPKA had no effect. In accordance with these results, overexpression of a catalytic inactive ITPKA mutant did not affect migration, and the Ins(1,4,5)P3-kinase-inhibitor GNF362 reversed the stimulating effect of ITPKA overexpression on migration. In summary, we demonstrate that under basal conditions the actin bundling activity controls ITPKA-facilitated migration and invasion and in presence of ATP the Ins(1,4,5)P3-kinase activity slightly enhances this effect.

Increased Levels of the Parkinson's Disease-Associated Gene ITPKB Correlate with Higher Expression Levels of α-Synuclein, Independent of Mutation Status

Autosomal dominant mutations in the gene encoding α-synuclein (SNCA) were the first to be linked with hereditary Parkinson's disease (PD). Duplication and triplication of SNCA has been observed in PD patients, together with mutations at the N-terminal of the protein, among which A30P and A53T influence the formation of fibrils. By overexpressing human α-synuclein in the neuronal system of Drosophila, we functionally validated the ability of IP3K2, an ortholog of the GWAS identified risk gene, Inositol-trisphosphate 3-kinase B (ITPKB), to modulate α-synuclein toxicity in vivo. ITPKB mRNA and protein levels were also increased in SK-N-SH cells overexpressing wild-type α-synuclein, A53T or A30P mutants. Kinase overexpression was detected in the cytoplasmatic and in the nuclear compartments in all α-synuclein cell types. By quantifying mRNAs in the cortex of PD patients, we observed higher levels of ITPKB mRNA when SNCA was expressed more (p < 0.05), compared to controls. A positive correlation was also observed between SNCA and ITPKB expression in the cortex of patients, which was not seen in the controls. We replicated this observation in a public dataset. Our data, generated in SK-N-SH cells and in cortex from PD patients, show that the expression of α-synuclein and ITPKB is correlated in pathological situations.

Kinase Inhibition as Treatment for Acute and Chronic Graft-Versus-Host Disease

Allogeneic hematopoietic stem cell transplantation (allo-HCT) is a potentially curative therapy for patients suffering from hematological malignancies via the donor immune system driven graft-versus-leukemia effect. However, the therapy is mainly limited by severe acute and chronic graft-versus-host disease (GvHD), both being life-threatening complications after allo-HCT. GvHD develops when donor T cells do not only recognize remaining tumor cells as foreign, but also the recipient’s tissue, leading to a severe inflammatory disease. Typical GvHD target organs include the skin, liver and intestinal tract. Currently all approved strategies for GvHD treatment are immunosuppressive therapies, with the first-line therapy being glucocorticoids. However, therapeutic options for glucocorticoid-refractory patients are still limited. Novel therapeutic approaches, which reduce GvHD severity while preserving GvL activity, are urgently needed. Targeting kinase activity with small molecule inhibitors has shown promising results in preclinical animal models and clinical trials. Well-studied kinase targets in GvHD include Rho-associated coiled-coil-containing kinase 2 (ROCK2), spleen tyrosine kinase (SYK), Bruton’s tyrosine kinase (BTK) and interleukin-2-inducible T-cell kinase (ITK) to control B- and T-cell activation in acute and chronic GvHD. Janus Kinase 1 (JAK1) and 2 (JAK2) are among the most intensively studied kinases in GvHD due to their importance in cytokine production and inflammatory cell activation and migration. Here, we discuss the role of kinase inhibition as novel treatment strategies for acute and chronic GvHD after allo-HCT.

The Parkinson's disease-associated gene ITPKB protects against α-synuclein aggregation by regulating ER-to-mitochondria calcium release

Parkinson’s disease (PD) is the second most prevalent neurodegenerative disease of aging, affecting approximately 10 million patients worldwide with no approved therapies to modify progression of disease. Further understanding of the cellular mechanisms contributing to the development of PD is necessary to discover therapies. Here, we characterize the role of a recently identified GWAS hit for sporadic PD, ITPKB, in the aggregation of α-synuclein, the primary pathological feature of disease. These results identify inhibition of inositol-1,4,5,-triphosphate (IP₃)-mediated ER-to-mitochondria calcium release as a potential therapeutic approach for reducing neuropathology in PD.

Inositol-1,4,5-triphosphate (IP₃) kinase B (ITPKB) is a ubiquitously expressed lipid kinase that inactivates IP₃, a secondary messenger that stimulates calcium release from the endoplasmic reticulum (ER). Genome-wide association studies have identified common variants in the ITPKB gene locus associated with reduced risk of sporadic Parkinson’s disease (PD). Here, we investigate whether ITPKB activity or expression level impacts PD phenotypes in cellular and animal models. In primary neurons, knockdown or pharmacological inhibition of ITPKB increased levels of phosphorylated, insoluble α-synuclein pathology following treatment with α-synuclein preformed fibrils (PFFs). Conversely, ITPKB overexpression reduced PFF-induced α-synuclein aggregation. We also demonstrate that ITPKB inhibition or knockdown increases intracellular calcium levels in neurons, leading to an accumulation of calcium in mitochondria that increases respiration and inhibits the initiation of autophagy, suggesting that ITPKB regulates α-synuclein pathology by inhibiting ER-to-mitochondria calcium transport. Furthermore, the effects of ITPKB on mitochondrial calcium and respiration were prevented by pretreatment with pharmacological inhibitors of the mitochondrial calcium uniporter complex, which was also sufficient to reduce α-synuclein pathology in PFF-treated neurons. Taken together, these results identify ITPKB as a negative regulator of α-synuclein aggregation and highlight modulation of ER-to-mitochondria calcium flux as a therapeutic strategy for the treatment of sporadic PD.

Inositol 1,4,5-trisphosphate 3-kinase B promotes Ca2+ mobilization and the inflammatory activity of dendritic cells

Innate immune responses to Gram-negative bacteria depend on the recognition of lipopolysaccharide (LPS) by a receptor complex that includes CD14 and TLR4. In dendritic cells (DCs), CD14 enhances the activation not only of TLR4 but also that of the NFAT family of transcription factors, which suppresses cell survival and promotes the production of inflammatory mediators. NFAT activation requires Ca²⁺ mobilization. In DCs, Ca²⁺ mobilization in response to LPS depends on phospholipase C γ2 (PLCγ2), which produces inositol 1,4,5-trisphosphate (IP₃). Here, we showed that the IP₃ receptor 3 (IP₃R3) and ITPKB, a kinase that converts IP₃ to inositol 1,3,4,5-tetrakisphosphate (IP₄), were both necessary for Ca²⁺ mobilization and NFAT activation in mouse and human DCs. A pool of IP₃R3 was located on the plasma membrane of DCs, where it colocalized with CD14 and ITPKB. Upon LPS binding to CD14, ITPKB was required for Ca²⁺ mobilization through plasma membrane-localized IP₃R3 and for NFAT nuclear translocation. Pharmacological inhibition of ITPKB in mice reduced both LPS-induced tissue swelling and the severity of inflammatory arthritis to a similar extent as that induced by the inhibition of NFAT using nanoparticles that delivered an NFAT-inhibiting peptide specifically to phagocytic cells. Our results suggest that ITPKB may represent a promising target for anti-inflammatory therapies that aim to inhibit specific DC functions.

AEB-071 Ameliorates Muscle Weakness by Altering Helper T Lymphocytes in an Experimental Autoimmune Myasthenia Gravis Rat Model

Background

Myasthenia gravis (MG) is an autoimmune neurological disorder of neuromuscular junctions. In this study we established experimental autoimmune myasthenia gravis (EAMG) rat models to investigate the effects of AEB-071 (AEB), which is a specific inhibitor of protein kinase C that prevents T lymphocyte activation.

Material/Methods

We utilized animals divided into 4 groups: (1) control rats, (2) EAMG, (3) AEB-071+EAMG, and (4) AZP+EAMG. Drug treatment was continued for 10 days. Ten weeks after immunization we measured body weights, assessed mortality rates, and used Lennon scores to evaluate EAMG grades. We also assessed the proportions of T_reg, T_h1, T_h2, T_h17, and lymphocytes using flow cytometry.

Results

In the absence of drug treatment, we found a significant decline in body weights in the EAMG group in comparison to control rats, and EAMG group rats also had higher Lennon scores (P<0.05). Interestingly, we found that AEB-071 restored the body weight of EAMG rats and the decreased mortality rate compared to AZP treatment. Although a decrease in the number of T_reg cells was observed, the proportion of T_h lymphocytes was significantly increased in the EAMG group, and AEB-071 treatment decreased the proportion of T_h lymphocytes.

Conclusions

We concluded that AEB-071 treatment imparts beneficial effects in EAMG rat models by reducing mortality rate and restoring T_h lymphocyte balance, and thus may be an attractive candidate for use in MG treatment.

Inhibition of inositol kinase B controls acute and chronic graft-versus-host disease

T-cell activation releases inositol 1,4,5-trisphosphate (IP3), inducing cytoplasmic calcium (Ca2+) influx. In turn, inositol 1,4,5-trisphosphate 3-kinase B (Itpkb) phosphorylates IP3 to negatively regulate and thereby tightly control Ca2+ fluxes that are essential for mature T-cell activation and differentiation and protection from cell death. Itpkb pathway inhibition increases intracellular Ca2+, induces apoptosis of activated T cells, and can control T-cell-mediated autoimmunity. In this study, we employed genetic and pharmacological approaches to inhibit Itpkb signaling as a means of controlling graft-versus-host disease (GVHD). Murine-induced, Itpkb-deleted (Itpkb-/-) T cells attenuated acute GVHD in 2 models without eliminating A20-luciferase B-cell lymphoma graft-versus-leukemia (GVL). A highly potent, selective inhibitor, GNF362, ameliorated acute GVHD without impairing GVL against 2 acute myeloid leukemia lines (MLL-AF9-eGFP and C1498-luciferase). Compared with FK506, GNF362 more selectively deleted donor alloreactive vs nominal antigen-responsive T cells. Consistent with these data and as compared with FK506, GNF362 had favorable acute GVHD and GVL properties against MLL-AF9-eGFP cells. In chronic GVHD preclinical models that have a pathophysiology distinct from acute GVHD, Itpkb-/- donor T cells reduced active chronic GVHD in a multiorgan system model of bronchiolitis obliterans (BO), driven by germinal center reactions and resulting in target organ fibrosis. GNF362 treatment reduced active chronic GVHD in both BO and scleroderma models. Thus, intact Itpkb signaling is essential to drive acute GVHD pathogenesis and sustain active chronic GVHD, pointing toward a novel clinical application to prevent acute or treat chronic GVHD.

Inositol-triphosphate 3-kinase B confers cisplatin resistance by regulating NOX4-dependent redox balance

How altered metabolism contributes to chemotherapy resistance in cancer cells remains unclear. Through a metabolism-related kinome RNAi screen, we identified inositol-trisphosphate 3-kinase B (ITPKB) as a critical enzyme that contributes to cisplatin-resistant tumor growth. We demonstrated that inositol 1,3,4,5-tetrakisphosphate (IP4), the product of ITPKB, plays a critical role in redox homeostasis upon cisplatin exposure by reducing cisplatin-induced ROS through inhibition of a ROS-generating enzyme, NADPH oxidase 4 (NOX4), which promotes cisplatin-resistant tumor growth. Mechanistically, we identified that IP4 competes with the NOX4 cofactor NADPH for binding and consequently inhibits NOX4. Targeting ITPKB with shRNA or its small-molecule inhibitor resulted in attenuation of NOX4 activity, imbalanced redox status, and sensitized cancer cells to cisplatin treatment in patient-derived xenografts. Our findings provide insight into the crosstalk between kinase-mediated metabolic regulation and platinum-based chemotherapy resistance in human cancers. Our study also suggests a distinctive signaling function of IP4 that regulates NOX4. Furthermore, pharmaceutical inhibition of ITPKB displayed synergistic attenuation of tumor growth with cisplatin, suggesting ITPKB as a promising synthetic lethal target for cancer therapeutic intervention to overcome cisplatin resistance.

Regulation of Hematopoietic Cell Development and Function Through Phosphoinositides

One of the most paramount receptor-induced signal transduction mechanisms in hematopoietic cells is production of the lipid second messenger phosphatidylinositol(3,4,5)trisphosphate (PIP₃) by class I phosphoinositide 3 kinases (PI3K). Defective PIP₃ signaling impairs almost every aspect of hematopoiesis, including T cell development and function. Limiting PIP₃ signaling is particularly important, because excessive PIP₃ function in lymphocytes can transform them and cause blood cancers. Here, we review the key functions of PIP₃ and related phosphoinositides in hematopoietic cells, with a special focus on those mechanisms dampening PIP₃ production, turnover, or function. Recent studies have shown that beyond “canonical” turnover by the PIP₃ phosphatases and tumor suppressors phosphatase and tensin homolog (PTEN) and SH2 domain-containing inositol-5-phosphatase-1 (SHIP-1/2), PIP₃ function in hematopoietic cells can also be dampened through antagonism with the soluble PIP₃ analogs inositol(1,3,4,5)tetrakisphosphate (IP₄) and inositol-heptakisphosphate (IP₇). Other evidence suggests that IP₄ can promote PIP₃ function in thymocytes. Moreover, IP₄ or the kinases producing it limit store-operated Ca²⁺ entry through Orai channels in B cells, T cells, and neutrophils to control cell survival and function. We discuss current models for how soluble inositol phosphates can have such diverse functions and can govern as distinct processes as hematopoietic stem cell homeostasis, neutrophil macrophage and NK cell function, and development and function of B cells and T cells. Finally, we will review the pathological consequences of dysregulated IP₄ activity in immune cells and highlight contributions of impaired inositol phosphate functions in disorders such as Kawasaki disease, common variable immunodeficiency, or blood cancer.