Absence of the lipid phosphatase SHIP2 confers resistance to dietary obesity

Drugs targeting SHIP2 demonstrate potent antiproliferative effects irrespective of SHIP2 inhibition

The SH2-containing inositol 5'-phosphatase SHIP2 plays a crucial role in negative regulation of the PI3K/AKT signaling pathway. Putative small molecule inhibitors of SHIP2, AS1949490 and K149 have been reported to elicit a range of beneficial effects in treating or preventing obesity as well as killing cancer cells. However, whether these effects are direct results of SHIP2 inhibition has not been carefully assessed, e.g., in the absence of expression of the protein. Here, we show that these inhibitors alter the PI3K/AKT signaling pathway irrespective of SHIP2 protein expression. Moreover, we found that AS1949490 and K149 alter cell growth in normal and cancer cells lacking both SHIP1 and SHIP2. Overall, our data provide evidence that the antiproliferative effects of AS1949490 and K149 cannot be attributed to SHIP1/2 inhibition.

Discovery of aurones bearing two amine functionalities as SHIP2 inhibitors with insulin-sensitizing effect in rat myotubes

Pharmacological inhibition of the SH2 domain-containing inositol 5-phosphatase 2 (SHIP2) by small-molecule compounds presents an attractive approach to modulate insulin sensitivity. Few drug-like SHIP2 inhibitors have been discovered to date. A series of aurones incorporating key motifs from known SHIP2 inhibitors were synthesized and evaluated for SHIP2-inhibiting activity against a recombinant SHIP2 protein in vitro. Three aurones that inhibited SHIP2 at 15-50 μM were identified. These aurone inhibitors required two amine functionalities, one at ring A and a second at ring B for good inhibitory activity as exemplified by 12a. Mechanistically, molecular dynamics simulations revealed 12a to preferably bind to an allosteric site, restricting the motion of the flexible L4 loop required for SHIP2 phosphatase activity. Additionally, a basic piperidine moiety of 12a interacted with an aspartate residue proximal to the site. At 20-40 μM, 12a significantly enhanced glucose uptake in rat myotubes via increased Akt phosphorylation. 12a showed good permeability across the Caco-2 cell monolayer supporting the aurone chemotype as a new lead to develop drug-like, oral insulin sensitizers.

Proteomics revealed composition- and size-related regulators for hepatic impairments induced by silica nanoparticles

Along with the growing production and application of silica nanoparticles (SiNPs), increased human exposure and ensuing safety evaluation have progressively attracted concern. Accumulative data evidenced the hepatic injuries upon SiNPs inhalation. Still, the understanding of the hepatic outcomes resulting from SiNPs exposure, and underlying mechanisms are incompletely elucidated. Here, SiNPs of two sizes (60 nm and 300 nm) were applied to investigate their composition- and size-related impacts on livers of ApoE-/- mice via intratracheal instillation. Histopathological and biochemical analysis indicated SiNPs promoted inflammation, lipid deposition and fibrosis in the hepatic tissue, accompanied by increased ALT, AST, TC and TG. Oxidative stress was activated upon SiNPs stimuli, as evidenced by the increased hepatic ROS, MDA and declined GSH/GSSG. Of note, these alterations were more dramatic in SiNPs with a smaller size (SiNPs-60) but the same dosage. LC-MS/MS-based quantitative proteomics unveiled changes in mice liver protein profiles, and filtered out particle composition- or size-related molecules. Interestingly, altered lipid metabolism and oxidative damage served as two critical biological processes. In accordance with correlation analysis and liver disease-targeting prediction, a final of 10 differentially expressed proteins (DEPs) were selected as key potential targets attributable to composition- (4 molecules) and size-related (6 molecules) liver impairments upon SiNPs stimuli. Overall, our study provided strong laboratory evidence for a comprehensive understanding of the harmful biological effects of SiNPs, which was crucial for toxicological evaluation to ensure nanosafety.

Phosphoinositides in New Spaces

Phosphoinositides (PIs) are phospholipids derived from phosphatidylinositol. PIs are regulated via reversible phosphorylation, which is directed by the opposing actions of PI kinases and phosphatases. PIs constitute a minor fraction of the total cellular lipid pool but play pleiotropic roles in multiple aspects of cell biology. Genetic mutations of PI regulatory enzymes have been identified in rare congenital developmental syndromes, including ciliopathies, and in numerous human diseases, such as cancer and metabolic and neurological disorders. Accordingly, PI regulatory enzymes have been targeted in the design of potential therapeutic interventions for human diseases. Recent advances place PIs as central regulators of membrane dynamics within functionally distinct subcellular compartments. This brief review focuses on the emerging role PIs play in regulating cell signaling within the primary cilium and in directing transfer of molecules at interorganelle membrane contact sites and identifies new roles for PIs in subcellular spaces.

Phosphoinositide 3-kinase (PI3K) classes: From cell signaling to endocytic recycling and autophagy

Lipid signaling is defined as any biological signaling action in which a lipid messenger binds to a protein target, converting its effects to specific cellular responses. In this complex biological pathway, the family of phosphoinositide 3-kinase (PI3K) represents a pivotal role and affects many aspects of cellular biology from cell survival, proliferation, and migration to endocytosis, intracellular trafficking, metabolism, and autophagy. While yeasts have a single isoform of phosphoinositide 3-kinase (PI3K), mammals possess eight PI3K types divided into three classes. The class I PI3Ks have set the stage to widen research interest in the field of cancer biology. The aberrant activation of class I PI3Ks has been identified in 30-50% of human tumors, and activating mutations in PIK3CA is one of the most frequent oncogenes in human cancer. In addition to indirect participation in cell signaling, class II and III PI3Ks primarily regulate vesicle trafficking. Class III PI3Ks are also responsible for autophagosome formation and autophagy flux. The current review aims to discuss the original data obtained from international research laboratories on the latest discoveries regarding PI3Ks-mediated cell biological processes. Also, we unravel the mechanisms by which pools of the same phosphoinositides (PIs) derived from different PI3K types act differently.

Genome-wide CRISPR/Cas9 screens reveal shared and cell-specific mechanisms of resistance to SHP2 inhibition

SHP2 (PTPN11) acts upstream of SOS1/2 to enable RAS activation. Allosteric SHP2 inhibitors (SHP2i) in the clinic prevent SHP2 activation, block proliferation of RTK- or cycling RAS mutant-driven cancers, and overcome "adaptive resistance." To identify SHP2i resistance mechanisms, we performed genome-wide CRISPR/Cas9 knockout screens on two SHP2i-sensitive cell lines, recovering genes expected to cause resistance (NF1, PTEN, CDKN1B, LZTR1, and RASA2) and novel targets (INPPL1, MAP4K5, epigenetic modifiers). We screened 14 additional lines with a focused CRISPR library targeting common "hits" from the genome-wide screens. LZTR1 deletion conferred resistance in 12/14 lines, followed by MAP4K5 (8/14), SPRED2/STK40 (6/14), and INPPL1 (5/14). INPPL1, MAP4K5, or LZTR1 deletion reactivated ERK signaling. INPPL1-mediated sensitization to SHP2i required its NPXY motif but not lipid phosphatase activity. MAP4K5 acted upstream of MEK through a kinase-dependent target(s); LZTR1 had cell-dependent effects on RIT and RAS stability. INPPL1, MAP4K5, or LZTR1 deletion also conferred SHP2i resistance in vivo. Defining the SHP2i resistance landscape could suggest effective combination approaches.

Obesity control by SHIP inhibition requires pan-paralog inhibition and an intact eosinophil compartment

Here we extend the understanding of how chemical inhibition of SHIP paralogs controls obesity. We compare different classes of SHIP inhibitors and find that selective inhibitors of SHIP1 or SHIP2 are unable to prevent weight gain and body fat accumulation during increased caloric intake. Surprisingly, only pan-SHIP1/2 inhibitors (pan-SHIPi) prevent diet-induced obesity. We confirm that pan-SHIPi is essential by showing that dual treatment with SHIP1 and SHIP2 selective inhibitors reduced adiposity during excess caloric intake. Consistent with this, genetic inactivation of both SHIP paralogs in eosinophils or myeloid cells also reduces obesity and adiposity. In fact, pan-SHIPi requires an eosinophil compartment to prevent diet-induced adiposity, demonstrating that pan-SHIPi acts via an immune mechanism. We also find that pan-SHIPi increases ILC2 cell function in aged, obese mice to reduce their obesity. Finally, we show that pan-SHIPi also reduces hyperglycemia, but not via eosinophils, indicating a separate mechanism for glucose control.

Cell-Dependent Pathogenic Roles of Filamin B in Different Skeletal Malformations

Mutations of filamin B (FLNB) gene can lead to a spectrum of autosomal skeletal malformations including spondylocarpotarsal syndrome (SCT), Larsen syndrome (LRS), type I atelosteogenesis (AO1), type III atelosteogenesis (AO3), and boomerang dysplasia (BD). Among them, LRS is milder while BD causes a more severe phenotype. However, the molecular mechanism underlying the differences in clinical phenotypes of different FLNB variants has not been fully determined. Here, we presented two patients suffering from autosomal dominant LRS and autosomal recessive vitamin D-dependent rickets type IA (VDDR-IA). Whole-exome sequencing revealed two novel missense variants in FLNB, c.4846A>G (p.T1616A) and c.7022T>G (p.I2341R), which are located in repeat 15 and 22 of filamin B, respectively. The expression of FLNB^I2341R in the muscle tissue from our LRS patient was remarkably increased. And in vitro studies showed that both variants led to a lack of filopodia and accumulation of the mutants in the perinuclear region in HEK293 cells. We also found that c.4846A>G (p.T1616A) and c.7022T>G (p.I2341R) regulated endochondral osteogenesis in different ways. c.4846A>G (p.T1616A) activated AKT pathways through inhibiting SHIP2, suppressed the Smad3 pathway, and impaired the expression of Runx2 in both Saos-2 and ATDC5 cells. c.7022T>G (p.I2341R) activated both AKT and Smad3 pathways and increased the expression of Runx2 in Saos-2 cells, while in ATDC5 cells it activated AKT pathways through inhibiting SHIP2, suppressed the Smad3 pathway, and reduced the expression of Runx2. Our study demonstrated the pathogenic mechanisms of two novel FLNB variants in two different clinical settings and proved that FLNB variants could not only directly cause skeletal malformations but also worsen skeletal symptoms in the setting of other skeletal diseases. Besides, FLNB variants differentially affect skeletal development which contributes to clinical heterogeneity of FLNB-related disorders.

Expression pattern and the roles of phosphatidylinositol phosphatases in testis

Phosphoinositides (PIs) are relatively rare lipid components of the cellular membranes. Their homeostasis is tightly controlled by specific PI kinases and phosphatases. PIs play essential roles in cellular signaling, cytoskeletal organization, and secretory processes in various diseases and normal physiology. Gene targeting experiments strongly suggest that in mice with deficiency of several PI phosphatases such as Pten, Mtmrs, Inpp4b, and Inpp5b, spermatogenesis is affected, resulting in partial or complete infertility. Similarly, in men, loss of several of the PIP phosphatases is observed in infertility characterized by the lack of mature sperm. Using available gene expression databases, we compare expression of known PI phosphatases in various testicular cell types, infertility patients, and mouse age-dependent testicular gene expression, and discuss their potential roles in testis physiology and spermatogenesis.

Discovery of a novel SHIP1 agonist that promotes degradation of lipid-laden phagocytic cargo by microglia

Here, we describe the use of artificial intelligence to identify novel agonists of the SH2-containing 5′ inositol phosphatase 1 (SHIP1). One of the compounds, K306, represents the most potent agonist identified to date. We find that K306 exhibits selectivity for SHIP1 vs. the paralog enzyme SHIP2, and this activation does not require the C2 domain of SHIP1 which other known SHIP1 agonists require. Thus, K306 represents a new class of SHIP1 agonists with a novel mode of agonism. Importantly, we find that K306 can suppress induction of inflammatory cytokines and iNOS in macrophages or microglia, but not by their SHIP1-deficient counterparts. K306 also reduces TNF-α production in vivo in an LPS-induced endotoxemia assay. Finally, we show that K306 enhances phagolysosomal degradation of synaptosomes and dead neurons by microglia revealing a novel function for SHIP1 that might be exploited therapeutically in dementia.

•

Discovery of a potent SHIP1 selective agonist (K306) via artificial intelligence

•

SHIP1 agonism via K306 is independent of the C2 domain and increases PI(3,4)P₂ levels

•

K306 reduces IL-6, TNF-α, and iNOS induction in microglia and macrophages

•

K306 promotes phagocytic degradation of lipid-laden but not protein cargo in microglia

Role of Distinct Fat Depots in Metabolic Regulation and Pathological Implications

People suffering from obesity and associated metabolic disorders including diabetes are increasing exponentially around the world. Adipose tissue (AT) distribution and alteration in their biochemical properties play a major role in the pathogenesis of these diseases. Emerging evidence suggests that AT heterogeneity and depot-specific physiological changes are vital in the development of insulin resistance in peripheral tissues like muscle and liver. Classically, AT depots are classified into white adipose tissue (WAT) and brown adipose tissue (BAT); WAT is the site of fatty acid storage, while BAT is a dedicated organ of metabolic heat production. The discovery of beige adipocyte clusters in WAT depots indicates AT heterogeneity has a more central role than hither to ascribed. Therefore, we have discussed in detail the current state of understanding on cellular and molecular origin of different AT depots and their relevance toward physiological metabolic homeostasis. A major focus is to highlight the correlation between altered WAT distribution in the body and metabolic pathogenesis in animal models and humans. We have also underscored the disparity in the molecular (including signaling) changes in various WAT tissues during diabetic pathogenesis. Exercise-mediated beneficial alteration in WAT physiology/distribution that protects against metabolic disorders is evolving. Here we have discussed the depot-specific biochemical adjustments induced by different forms of exercise. A detailed understanding of the molecular details of inter-organ crosstalk via substrate utilization/storage and signaling through chemokines provide strategies to target selected WAT depots to pharmacologically mimic the benefits of exercise countering metabolic diseases including diabetes.

Multiorgan failure with abnormal receptor metabolism in mice mimicking Samd9/9L syndromes

Autosomal dominant sterile α motif domain containing 9 (Samd9) and Samd9L (Samd9/9L) syndromes are a large subgroup of currently established inherited bone marrow failure syndromes that includes myelodysplasia, infection, growth restriction, adrenal hypoplasia, genital phenotypes, and enteropathy (MIRAGE), ataxia pancytopenia, and familial monosomy 7 syndromes. Samd9/9L genes are located in tandem on chromosome 7 and have been known to be the genes responsible for myeloid malignancies associated with monosomy 7. Additionally, as IFN-inducible genes, Samd9/9L are crucial for protection against viruses. Samd9/9L syndromes are caused by gain-of-function mutations and develop into infantile myelodysplastic syndromes associated with monosomy 7 (MDS/-7) at extraordinarily high frequencies. We generated mice expressing Samd9LD764N, which mimic MIRAGE syndrome, presenting with growth retardation, a short life, bone marrow failure, and multiorgan degeneration. In hematopoietic cells, Samd9LD764N downregulates the endocytosis of transferrin and c-Kit, resulting in a rare cause of anemia and a low bone marrow reconstitutive potential that ultimately causes MDS/-7. In contrast, in nonhematopoietic cells we tested, Samd9LD764N upregulated the endocytosis of EGFR by Ship2 phosphatase translocation to the cytomembrane and activated lysosomes, resulting in the reduced expression of surface receptors and signaling. Thus, Samd9/9L is a downstream regulator of IFN that controls receptor metabolism, with constitutive activation leading to multiorgan dysfunction.

An auxiliary binding interface of SHIP2-SH2 for Y292-phosphorylated FcγRIIB reveals diverse recognition mechanisms for tyrosine-phosphorylated receptors involved in different cell signaling pathways

SH2 domain-containing inositol 5-phosphatase 2 (SHIP2) plays an essential role in regulating phosphatidylinositol level in human cell, and is recruited to many phosphotyrosine (pY)-dependent signal transduction pathways by the SH2 domain. In immunity signaling, immunoreceptor FcγRIIB binds to SHIP2-SH2 via its Y292-phosphorylated immunoreceptor tyrosine-based inhibitory motif (ITIM) and transmits inhibitory signal, which regulates B cell and neuronal cell activity and is associated with immune diseases and Alzheimer's disease. To date, the interaction between SHIP2 and FcγRIIB has not been analyzed from a structural point of view. Here, the binding of SHIP2-SH2 with Y292-phosphorylated FcγRIIB-ITIM was analyzed using NMR spectroscopy. The results demonstrated that SHIP2-SH2 mainly utilizes two regions including a pY-binding pocket and a specificity pocket formed by βD, βE, and EF-loop, to bind with FcγRIIB-ITIM in high affinity. In addition to the two regions, the BG-loop of SHIP2-SH2 functions as an auxiliary interface enhancing affinity. By comparing the binding of SHIP2-SH2 with ligands from FcγRIIB and c-MET, a hepatocyte growth factor receptor associated with tumorigenesis, significant differences in interface and affinity were found, suggesting that SHIP2-SH2 applies diverse patterns for binding to different ligand proteins. Moreover, S49, S51, and R70 of SHIP2 were identified to mediate the binding of both FcγRIIB and c-MET, while R28 and Q107 were found to only participate in the binding of c-MET and FcγRIIB respectively. Taken together, this study reveals the diverse mechanisms of SHIP2-SH2 for recognizing different ligands, and provides important clues for selectively manipulating various signaling pathways and specific drug design.

The 5-Phosphatase SHIP2 Promotes Neutrophil Chemotaxis and Recruitment

Neutrophils, the most abundant circulating leukocytes in humans have key roles in host defense and in the inflammatory response. Agonist-activated phosphoinositide 3-kinases (PI3Ks) are important regulators of many facets of neutrophil biology. PIP3 is subject to dephosphorylation by several 5’ phosphatases, including SHIP family phosphatases, which convert the PI3K product and lipid second messenger phosphatidylinositol 3,4,5-trisphosphate (PIP3) into PI(3,4)P2, a lipid second messenger in its own right. In addition to the leukocyte restricted SHIP1, neutrophils express the ubiquitous SHIP2. This study analyzed mice and isolated neutrophils carrying a catalytically inactive SHIP2, identifying an important regulatory function in neutrophil chemotaxis and directionality in vitro and in neutrophil recruitment to sites of sterile inflammation in vivo, in the absence of major defects of any other neutrophil functions analyzed, including, phagocytosis and the formation of reactive oxygen species. Mechanistically, this is explained by a subtle effect on global 3-phosphorylated phosphoinositide species. This work identifies a non-redundant role for the hitherto overlooked SHIP2 in the regulation of neutrophils, and specifically, neutrophil chemotaxis/trafficking. It completes an emerging wider understanding of the complexity of PI3K signaling in the neutrophil, and the roles played by individual kinases and phosphatases within.

Targeting SHIP1 and SHIP2 in Cancer

Simple Summary

Phosphoinositol signaling pathways and their dysregulation have been shown to have a fundamental role in health and disease, respectively. The SH2-containing 5′ inositol phosphatases, SHIP1 and SHIP2, are regulators of the PI3K/AKT pathway that have crucial roles in cancer progression. This review aims to summarize the role of SHIP1 and SHIP2 in cancer signaling and the immune response to cancer, the discovery and use of SHIP inhibitors and agonists as possible cancer therapeutics.

Abstract

Membrane-anchored and soluble inositol phospholipid species are critical mediators of intracellular cell signaling cascades. Alterations in their normal production or degradation are implicated in the pathology of a number of disorders including cancer and pro-inflammatory conditions. The SH2-containing 5′ inositol phosphatases, SHIP1 and SHIP2, play a fundamental role in these processes by depleting PI(3,4,5)P₃, but also by producing PI(3,4)P₂ at the inner leaflet of the plasma membrane. With the intent of targeting SHIP1 or SHIP2 selectively, or both paralogs simultaneously, small molecule inhibitors and agonists have been developed and tested in vitro and in vivo over the last decade in various disease models. These studies have shown promising results in various pre-clinical models of disease including cancer and tumor immunotherapy. In this review the potential use of SHIP inhibitors in cancer is discussed with particular attention to the molecular structure, binding site and efficacy of these SHIP inhibitors.

Tribbles Pseudokinase 2 (TRIB2) Regulates Expression of Binding Partners in Bovine Granulosa Cells

Members of the Tribbles (TRIB) family of pseudokinases are critical components of intracellular signal transduction pathways in physiological and pathological processes. TRIBs, including TRIB2, have been previously shown as signaling mediators and scaffolding proteins regulating numerous cellular events such as proliferation, differentiation and cell death through protein stability and activity. However, the signaling network associated with TRIB2 and its binding partners in granulosa cells during ovarian follicular development is not fully defined. We previously reported that TRIB2 is differentially expressed in growing dominant follicles while downregulated in ovulatory follicles following the luteinizing hormone (LH) surge or human chorionic gonadotropin (hCG) injection. In the present study, we used the yeast two-hybrid screening system and in vitro coimmunoprecipitation assays to identify and confirm TRIB2 interactions in granulosa cells (GCs) of dominant ovarian follicles (DFs), which yielded individual candidate binding partners including calmodulin 1 (CALM1), inhibin subunit beta A (INHBA), inositol polyphosphate phosphatase-like 1 (INPPL1), 5'-nucleotidase ecto (NT5E), stearoyl-CoA desaturase (SCD), succinate dehydrogenase complex iron sulfur subunit B (SDHB) and Ras-associated protein 14 (RAB14). Further analyses showed that all TRIB2 binding partners are expressed in GCs of dominant follicles but are differentially regulated throughout the different stages of follicular development. CRISPR/Cas9-driven inhibition along with pQE-driven overexpression of TRIB2 showed that TRIB2 differently regulates expression of binding partners, which reveals the importance of TRIB2 in the control of gene expression linked to various biological processes such as proliferation, differentiation, cell migration, apoptosis, calcium signaling and metabolism. These data provide a larger view of potential TRIB2-regulated signal transduction pathways in GCs and provide strong evidence that TRIB2 may act as a regulator of target genes during ovarian follicular development.

PTEN and Other PtdIns(3,4,5)P3 Lipid Phosphatases in Breast Cancer

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.

Phosphoinositide lipids in primary cilia biology

Primary cilia are solitary signalling organelles projecting from the surface of most cell types. Although the ciliary membrane is continuous with the plasma membrane it exhibits a unique phospholipid composition, a feature essential for normal cilia formation and function. Recent studies have illustrated that distinct phosphoinositide lipid species localise to specific cilia subdomains, and have begun to build a 'phosphoinositide map' of the cilium. The abundance and localisation of phosphoinositides are tightly regulated by the opposing actions of lipid kinases and lipid phosphatases that have also been recently discovered at cilia. The critical role of phosphoinositides in cilia biology is highlighted by the devastating consequences of genetic defects in cilia-associated phosphoinositide regulatory enzymes leading to ciliopathy phenotypes in humans and experimental mouse and zebrafish models. Here we provide a general introduction to primary cilia and the roles phosphoinositides play in cilia biology. In addition to increasing our understanding of fundamental cilia biology, this rapidly expanding field may inform novel approaches to treat ciliopathy syndromes caused by deregulated phosphoinositide metabolism.

The Molecular Landscape of Hürthle Cell Thyroid Cancer Is Associated with Altered Mitochondrial Function-A Comprehensive Review

Hürthle cell thyroid carcinoma (HTC) accounts for 3-5% of all thyroid malignancies. Widely invasive HTC is characterized by poor prognosis and limited responsiveness to standard therapy with radioiodine. The molecular landscape of HTC is significantly different from the genetic signature seen in other forms of thyroid cancer. We performed a comprehensive literature review on the association between the molecular features of HTC and cancer metabolism. We searched the Pubmed, Embase, and Medline databases for clinical and translational studies published between 1980 and 2020 in English, coupling "HTC" with the following keywords: "genomic analysis", "mutations", "exome sequencing", "molecular", "mitochondria", "metabolism", "oxidative phosphorylation", "glycolysis", "oxidative stress", "reactive oxygen species", and "oncogenes". HTC is characterized by frequent complex I mitochondrial DNA mutations as early clonal events. This genetic signature is associated with the abundance of malfunctioning mitochondria in cancer cells. HTC relies predominantly on aerobic glycolysis as a source of energy production, as oxidative phosphorylation-related genes are downregulated. The enhanced glucose utilization by HTC is used for diagnostic purposes in the clinical setting for the detection of metastases by fluorodeoxyglucose positron emission tomography (FGD-PET/CT) imaging. A comprehensive metabolomic profiling of HTC in association with its molecular landscape might be necessary for the implementation of tumor-specific therapeutic approaches.

IRSp53 is a novel interactor of SHIP2: A role of the actin binding protein Mena in their cellular localization in breast cancer cells

A tight control of the machineries regulating membrane bending and actin dynamics is very important for the generation of membrane protrusions, which are crucial for cell migration and invasion. Protein/protein and protein/phosphoinositides complexes assemble and disassemble to coordinate these mechanisms, the scaffold properties of the involved proteins playing a prominent role in this organization. The PI 5-phosphatase SHIP2 is a critical enzyme modulating PI(3,4,5)P₃, PI(4,5)P₂ and PI(3,4)P₂ content in the cell. The scaffold properties of SHIP2 contribute to the specific targeting or retention of the protein in particular subcellular domains. Here, we identified IRSp53 as a new binding interactor of SHIP2 proline-rich domain. Both proteins are costained in HEK293T cells protrusions, upon transfection. We showed that the SH3-binding polyproline motif recognized by IRSp53 in SHIP2 is different from the regions targeted by other PRR binding partners i.e., CIN85, ITSN or even Mena a common interactor of both SHIP2 and IRSp53. We presented evidence that IRSp53 phosphorylation on S366 did not influence its interaction with SHIP2 and that Mena is not necessary for the association of SHIP2 with IRSp53 in MDA-MB-231 cells. The absence of Mena in MDA-MB-231 cells decreased the intracellular content in F-actin and modified the subcellular localization of SHIP2 and IRSp53 by increasing their relative content at the plasma membrane. Together our data suggest that SHIP2, through interaction with the cell protrusion regulators IRSp53 and Mena, participate to the formation of multi-protein complexes. This ensures the appropriate modulations of PIs which is important for regulation of membrane dynamics.

PI(3,4)P2 Signaling in Cancer and Metabolism

The phosphatidylinositide 3 kinases (PI3Ks) and their downstream mediators AKT and mammalian target of rapamycin (mTOR) are central regulators of glycolysis, cancer metabolism, and cancer cell proliferation. At the molecular level, PI3K signaling involves the generation of the second messenger lipids phosphatidylinositol 3,4,5-trisphosphate [PI(3,4,5)P3] and phosphatidylinositol 3,4-bisphosphate [PI(3,4)P2]. There is increasing evidence that PI(3,4)P2 is not only the waste product for the removal of PI(3,4,5)P3 but can also act as a signaling molecule. The selective cellular functions for PI(3,4)P2 independent of PI(3,4,5)P3 have been recently described, including clathrin-mediated endocytosis and mTOR regulation. However, the specific spatiotemporal dynamics and signaling role of PI3K minor lipid messenger PI(3,4)P2 are not well-understood. This review aims at highlighting the biological functions of this lipid downstream of phosphoinositide kinases and phosphatases and its implication in cancer metabolism.

Small molecule targeting of SHIP1 and SHIP2

Modulating the activity of the Src Homology 2 (SH2) — containing Inositol 5′-Phosphatase (SHIP) enzyme family with small molecule inhibitors provides a useful and unconventional method of influencing cell signaling in the PI3K pathway. The development of small molecules that selectively target one of the SHIP paralogs (SHIP1 or SHIP2) as well as inhibitors that simultaneously target both enzymes have provided promising data linking the phosphatase activity of the SHIP enzymes to disorders and disease states that are in dire need of new therapeutic targets. These include cancer, immunotherapy, diabetes, obesity, and Alzheimer's disease. In this mini-review, we will provide a brief overview of research in these areas that support targeting SHIP1, SHIP2 or both enzymes for therapeutic purposes.

Improved Tetanic Force and Mitochondrial Calcium Homeostasis by Astaxanthin Treatment in Mouse Skeletal Muscle

BACKGROUND

Astaxanthin (AX) a marine carotenoid is a powerful natural antioxidant which protects against oxidative stress and improves muscle performance. Retinol and its derivatives were described to affect lipid and energy metabolism. Up to date, the effects of AX and retinol on excitation-contraction coupling (ECC) in skeletal muscle are poorly described.

METHODS

18 C57Bl6 mice were divided into two groups: Control and AX supplemented in rodent chow for 4 weeks (AstaReal A1010). In vivo and in vitro force and intracellular calcium homeostasis was studied. In some experiments acute treatment with retinol was employed.

RESULTS

The voltage activation of calcium transients (V₅₀) were investigated in single flexor digitorum brevis isolated fibers under patch clamp and no significant changes were found following AX supplementation. Retinol shifted V₅₀ towards more positive values and decreased the peak F/F₀ of the calcium transients. The amplitude of tetani in the extensor digitorum longus was significantly higher in AX than in control group. Lastly, the mitochondrial calcium uptake was found to be less prominent in AX.

CONCLUSION

AX supplementation increases in vitro tetanic force without affecting ECC and exerts a protecting effect on the mitochondria. Retinol treatment has an inhibitory effect on ECC in skeletal muscle.

SHIPping out diabetes-Metformin, an old friend among new SHIP2 inhibitors

SHIP2 (Src homology 2 domain‐containing inositol 5′‐phosphatase 2) belongs to the family of 5′‐phosphatases. It regulates the phosphoinositide 3‐kinase (PI3K)‐mediated insulin signalling cascade by dephosphorylating the 5′‐position of PtdIns(3,4,5)P3 to generate PtdIns(3,4)P2, suppressing the activity of the pathway. SHIP2 mouse models and genetic studies in human propose that increased expression or activity of SHIP2 contributes to the pathogenesis of the metabolic syndrome, hypertension and type 2 diabetes. This has raised great interest to identify SHIP2 inhibitors that could be used to design new treatments for metabolic diseases. This review summarizes the central mechanisms associated with the development of diabetic kidney disease, including the role of insulin resistance, and then moves on to describe the function of SHIP2 as a regulator of metabolism in mouse models. Finally, the identification of SHIP2 inhibitors and their effects on metabolic processes in vitro and in vivo are outlined. One of the newly identified SHIP2 inhibitors is metformin, the first‐line medication prescribed to patients with type 2 diabetes, further boosting the attraction of SHIP2 as a treatment target to ameliorate metabolic disorders.

Altered chondrocyte differentiation, matrix mineralization and MEK-Erk1/2 signaling in an INPPL1 catalytic knock-out mouse model of opsismodysplasia

Opsismodysplasia (OPS) is a rare but severe autosomal recessive skeletal chondrodysplasia caused by inactivating mutations in the Inppl1/Ship2 gene. The molecular mechanism leading from Ship2 gene inactivation to OPS is currently unknown. Here, we used our Ship2^Δ/Δ mouse expressing reduced amount of a catalytically-inactive SHIP2 protein and a previously reported SHIP2 inhibitor to investigate growth plate development and mineralization in vivo, ex vivo and in vitro. First, as observed in OPS patients, catalytic inactivation of SHIP2 in mouse leads to reduced body length, shortening of long bones, craniofacial dysmorphism, reduced height of the hyperthrophic chondrocyte zone and to defects in growth plate mineralization. Second, intrinsic Ship2^Δ/Δ bone defects were sufficient to induce the characteristic OPS alterations in bone growth, histology and mineralization ex vivo. Third, expression of osteocalcin was significantly increased in SHIP2-inactivated chondrocyte cultures whereas production of mineralized nodules was markedly decreased. Targeting osteocalcin mRNA with a specific shRNA increased the production of mineralized nodules. Fourth, levels of p-MEK and p-Erk1/2 were significantly increased in SHIP2-inactivated chondrocytes in response to serum and IGF-1, but not to FGF2, as compared to control chondrocytes. Treatment of chondrocytes and bones in culture with a MEK inhibitor partially rescued the production of mineralized nodules, the size of the hypertrophic chondrocyte zone and bone growth, raising the possibility of a treatment that could partially reduce the phenotype of this severe condition. Altogether, our results indicate that Ship2^Δ/Δ mice represent a relevant model for human OPS. They also highlight the important role of SHIP2 in chondrocytes during endochondral ossification and its different differentiation steps. Finally, we identified a role of osteocalcin in mineralized nodules production and for the MEK-Erk1/2 signaling pathway in the OPS phenotype.

Maternal and Post-weaning High-Fat Diets Produce Distinct DNA Methylation Patterns in Hepatic Metabolic Pathways within Specific Genomic Contexts

Calorie-dense high-fat diets (HF) are associated with detrimental health outcomes, including obesity, cardiovascular disease, and diabetes. Both pre- and post-natal HF diets have been hypothesized to negatively impact long-term metabolic health via epigenetic mechanisms. To understand how the timing of HF diet intake impacts DNA methylation and metabolism, male Sprague–Dawley rats were exposed to either maternal HF (MHF) or post-weaning HF diet (PHF). At post-natal week 12, PHF rats had similar body weights but greater hepatic lipid accumulation compared to the MHF rats. Genome-wide DNA methylation was evaluated, and analysis revealed 1744 differentially methylation regions (DMRs) between the groups with the majority of the DMR located outside of gene-coding regions. Within differentially methylated genes (DMGs), intragenic DNA methylation closer to the transcription start site was associated with lower gene expression, whereas DNA methylation further downstream was positively correlated with gene expression. The insulin and phosphatidylinositol (PI) signaling pathways were enriched with 25 DMRs that were associated with 20 DMGs, including PI3 kinase (Pi3k), pyruvate kinase (Pklr), and phosphodiesterase 3 (Pde3). Together, these results suggest that the timing of HF diet intake determines DNA methylation and gene expression patterns in hepatic metabolic pathways that target specific genomic contexts.

Phosphatidylinositol Kinases and Phosphatases in Entamoeba histolytica

Phosphatidylinositol (PtdIns) metabolism is indispensable in eukaryotes. Phosphoinositides (PIs) are phosphorylated derivatives of PtdIns and consist of seven species generated by reversible phosphorylation of the inositol moieties at the positions 3, 4, and 5. Each of the seven PIs has a unique subcellular and membrane domain distribution. In the enteric protozoan parasite Entamoeba histolytica, it has been previously shown that the PIs phosphatidylinositol 3-phosphate (PtdIns3P), PtdIns(4,5)P₂, and PtdIns(3,4,5)P₃ are localized to phagosomes/phagocytic cups, plasma membrane, and phagocytic cups, respectively. The localization of these PIs in E. histolytica is similar to that in mammalian cells, suggesting that PIs have orthologous functions in E. histolytica. In contrast, the conservation of the enzymes that metabolize PIs in this organism has not been well-documented. In this review, we summarized the full repertoire of the PI kinases and PI phosphatases found in E. histolytica via a genome-wide survey of the current genomic information. E. histolytica appears to have 10 PI kinases and 23 PI phosphatases. It has a panel of evolutionarily conserved enzymes that generate all the seven PI species. However, class II PI 3-kinases, type II PI 4-kinases, type III PI 5-phosphatases, and PI 4P-specific phosphatases are not present. Additionally, regulatory subunits of class I PI 3-kinases and type III PI 4-kinases have not been identified. Instead, homologs of class I PI 3-kinases and PTEN, a PI 3-phosphatase, exist as multiple isoforms, which likely reflects that elaborate signaling cascades mediated by PtdIns(3,4,5)P₃ are present in this organism. There are several enzymes that have the nuclear localization signal: one phosphatidylinositol phosphate (PIP) kinase, two PI 3-phosphatases, and one PI 5-phosphatase; this suggests that PI metabolism also has conserved roles related to nuclear functions in E. histolytica, as it does in model organisms.

Expansion and Functional Divergence of Inositol Polyphosphate 5-Phosphatases in Angiosperms

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-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.

Genome-wide association study for backfat thickness at 100 kg and loin muscle thickness in domestic pigs based on genotyping by sequencing

Both backfat thickness at 100 kg (B100) and loin muscle thickness (LMT) are economically important traits in pigs. In this study, a total of 1,200 pigs (600 Landrace and 600 Yorkshire pigs) were examined with genotyping by sequencing. A total of 345,570 single nucleotide polymorphisms (SNPs) were obtained from 1,200 pigs. Then, a single marker regression test was used to conduct a genome-wide association study for B100 and LMT. A total of 8 and 90 significant SNPs were detected for LMT and B100, respectively. Interestingly, two shared significant loci [located at Sus scrofa chromosome (SSC) 6: 149876694 and SSC12: 46226580] were detected in two breeds for B100. Furthermore, three potential candidate genes were found for LMT and B100. The positional candidate gene FAM3C (SSC18: 25573656, P = 2.48 × 10^-9), which controls the survival, growth, and differentiation of tissues and cells, was found for LMT in Landrace pigs. At SSC9: 6.78-6.82 Mb in Landrace pigs, the positional candidate gene, INPPL1, which has a negative regulatory effect on diet-induced obesity and is involved in the regulation of insulin function, was found for B100. The candidate gene, RAB35, which regulates the adipocyte glucose transporter SLC2A4/GLUT4, was identified at approximately SSC14: 40.09-40.13 Mb in Yorkshire pigs. The results of this GWAS will greatly advance our understanding of the genetic architecture of the LMT and B100 traits. However, these identified loci and genes need to be further verified in more pig populations, and their functions also need to be validated by more biological experiments in pigs.

Metformin increases glucose uptake and acts renoprotectively by reducing SHIP2 activity

Metformin, the first-line drug to treat type 2 diabetes (T2D), inhibits mitochondrial glycerolphosphate dehydrogenase in the liver to suppress gluconeogenesis. However, the direct target and the underlying mechanisms by which metformin increases glucose uptake in peripheral tissues remain uncharacterized. Lipid phosphatase Src homology 2 domain-containing inositol-5-phosphatase 2 (SHIP2) is upregulated in diabetic rodent models and suppresses insulin signaling by reducing Akt activation, leading to insulin resistance and diminished glucose uptake. Here, we demonstrate that metformin directly binds to and reduces the catalytic activity of the recombinant SHIP2 phosphatase domain in vitro. Metformin inhibits SHIP2 in cultured cells and in skeletal muscle and kidney of db/db mice. In SHIP2-overexpressing myotubes, metformin ameliorates reduced glucose uptake by slowing down glucose transporter 4 endocytosis. SHIP2 overexpression reduces Akt activity and enhances podocyte apoptosis, and both are restored to normal levels by metformin. SHIP2 activity is elevated in glomeruli of patients with T2D receiving nonmetformin medication, but not in patients receiving metformin, compared with people without diabetes. Furthermore, podocyte loss in kidneys of metformin-treated T2D patients is reduced compared with patients receiving nonmetformin medication. Our data unravel a novel molecular mechanism by which metformin enhances glucose uptake and acts renoprotectively by reducing SHIP2 activity.-Polianskyte-Prause, Z., Tolvanen, T. A., Lindfors, S., Dumont, V., Van, M., Wang, H., Dash, S. N., Berg, M., Naams, J.-B., Hautala, L. C., Nisen, H., Mirtti, T., Groop, P.-H., Wähälä, K., Tienari, J., Lehtonen, S. Metformin increases glucose uptake and acts renoprotectively by reducing SHIP2 activity.

Involvement of Hepatic SHIP2 and PI3K/Akt Signalling in the Regulation of Plasma Insulin by Xiaoyaosan in Chronic Immobilization-Stressed Rats

Background: Long-term exposure to chronic stress is thought to be a factor closely correlated with the development of metabolic disorders, such as diabetes mellitus and metabolic syndrome. Xiaoyaosan, a Chinese herbal formula, has been described in many previous studies to exert anxiolytic-like or antidepressant effects in chronically stressed rats. However, few studies have observed the effects of Xiaoyaosan on the metabolic disorders induced by chronic stress. Objective: We sought to investigate the effective regulation of Xiaoyaosan on 21-day chronic immobility stress (CIS, which is 3 h of restraint immobilization every day)-induced behavioural performance and metabolic responses and to further explore whether the effects of Xiaoyaosan were related to SHIP2 expression in the liver. Methods: Sixty male Sprague Dawley rats were randomly divided into a control group, a CIS group, a Xiaoyaosan group and a rosiglitazone group. The latter three groups were subjected to 21 days of CIS to generate the stress model. After 21 days of CIS, the effects of Xiaoyaosan on body weight, food intake, and behaviour in the open field test, the sucrose preference test and the forced swimming test were observed following chronic stress. Plasma insulin, cholesterol (CHOL), triglyceride (TG), low-density lipoprotein (LDL-C) and high-density lipoprotein (HDL-C) concentrations and blood glucose were examined, and the protein and mRNA expression levels of SHIP2, p85 and Akt in the liver were measured using RT-qPCR and immunohistochemical staining. Results: Rats exposed to CIS exhibited depression-like behaviours, decreased levels of plasma insulin, CHOL, LDL-C, TG and HDL-C, and increased blood glucose. Increased SHIP2 expression and reduced Akt, p-Akt and p85 expression were also observed in the liver. Xiaoyaosan exerted antidepressant effects and effectively reversed the changes caused by CIS. Conclusions: These results suggest that Xiaoyaosan attenuates depression-like behaviours and ameliorates stress-induced abnormal levels of insulin, blood glucose, CHOL, LDL-C and HDL-C in the plasma of stressed rats, which may be associated with the regulation of SHIP2 expression to enhance PI3K/Akt signalling activity in the liver.

A transcriptomic roadmap to alpha- and beta cell differentiation in the embryonic pancreas

During pancreatic development, endocrine cells appear from the pancreatic epithelium when Neurog3 positive cells delaminate and differentiate into alpha, beta, gamma and delta cells. The mechanisms involved in this process are still incompletely understood. We characterized the temporal, lineage-specific developmental programs during pancreatic development by sequencing the transcriptome of thousands of individual pancreatic cells from embryonic day E12.5 to E18.5 in mice, and identified all known cell types that are present in the embryonic pancreas, but focused specifically on alpha and beta cell differentiation by enrichment of a MIP-GFP reporter. We characterized transcriptomic heterogeneity in the tip domain based on proliferation, and characterized two endocrine precursor clusters marked by expression of Neurog3 and Fev. Pseudotime analysis revealed specific branches for developing alpha- and beta cells, which allowed identification of specific gene regulation patterns. These include some known and many previously unreported genes that appear to define pancreatic cell fate transitions. This resource allows dynamic profiling of embryonic pancreas development at single cell resolution and reveals novel gene signatures during pancreatic differentiation into alpha and beta cells.

The inositol phosphatase SHIP2 enables sustained ERK activation downstream of FGF receptors by recruiting Src kinases

Sustained activation of extracellular signal-regulated kinase (ERK) drives pathologies caused by mutations in fibroblast growth factor receptors (FGFRs). We previously identified the inositol phosphatase SHIP2 (also known as INPPL1) as an FGFR-interacting protein and a target of the tyrosine kinase activities of FGFR1, FGFR3, and FGFR4. We report that loss of SHIP2 converted FGF-mediated sustained ERK activation into a transient signal and rescued cell phenotypes triggered by pathologic FGFR-ERK signaling. Mutant forms of SHIP2 lacking phosphoinositide phosphatase activity still associated with FGFRs and did not prevent FGF-induced sustained ERK activation, demonstrating that the adaptor rather than the catalytic activity of SHIP2 was required. SHIP2 recruited Src family kinases to the FGFRs, which promoted FGFR-mediated phosphorylation and assembly of protein complexes that relayed signaling to ERK. SHIP2 interacted with FGFRs, was phosphorylated by active FGFRs, and promoted FGFR-ERK signaling at the level of phosphorylation of the adaptor FRS2 and recruitment of the tyrosine phosphatase PTPN11. Thus, SHIP2 is an essential component of canonical FGF-FGFR signal transduction and a potential therapeutic target in FGFR-related disorders.

Solution structure of SHIP2 SH2 domain and its interaction with a phosphotyrosine peptide from c-MET

SH2 domain-containing inositol 5-phosphatase 2 (SHIP2) binds with the Y1356-phosphorylated hepatocyte growth factor (HGF) receptor, c-MET, through its SH2 domain, which is essential for the role of SHIP2 in HGF-induced cell scattering and cell spreading. Previously, the experimental structure of the SH2 domain from SHIP2 (SHIP2-SH2) had not been reported, and its interaction with the Y1356-phosphorylated c-MET had not been investigated from a structural point of view. In this study, the solution structure of SHIP2-SH2 was determined by NMR spectroscopy, where it was found to adopt a typical SH2-domain fold that contains a positively-charged pocket for binding to phosphotyrosine (pY). The interaction between SHIP2-SH2 and a pY-containing peptide from c-MET (Y1356 phosphorylated) was investigated through NMR titrations. The results showed that the binding affinity of SHIP2-SH2 with the phosphopeptide is at low micromolar level, and the binding interface consists of the positively-charged pocket and its surrounding regions. Furthermore, R28, S49 and R70 were identified as key residues for the binding and may directly interact with the pY. Taken together, these findings provide structural insights into the binding of SHIP2-SH2 with the Y1356-phosphorylated c-MET, and lay a foundation for further studies of the interactions between SHIP2-SH2 and its various binding partners.

Global lipidomics reveals two plasma lipids as novel biomarkers for the detection of squamous cell lung cancer: A pilot study

Lipids are known to serve important roles in energy storage, membrane structure and signal transduction as well as in human cancers. In the present study, lipidomics was employed in order to identify plasma lipid markers for the early detection of lung cancer. Mass spectrometry was performed to profile 390 individual lipids in 44 plasma samples obtained from a training discovery cohort, which included 22 patients with squamous cell lung carcinoma (SqCC) and 22 high-risk individuals. An additional cohort that included 22 high-risk individuals and 22 patients with SqCC was further used for validation. During the training stage, a total of 20 distinct lipids that were significantly distributed between the high-risk and SqCC cases, were identified. A panel of 2 lipid markers (C18:2 cholesterol esters and sphingomyelin 22:0) were then further defined using the training accuracy values of 95.5% sensitivity, 90.9% specificity and 95.2% area under the receiver operating characteristic curve (AUC). The validation accuracy values applied for the additional cohort were 93.9% sensitivity, 92.9% specificity and 98.7% AUC. Thus, in the present study, 2 lipid markers that were able to discern SqCC patients from high-risk individuals with a high sensitivity, specificity and accuracy, were identified. These results may provide vital information for the development of a quick and safe blood test for the early diagnosis of SqCC.

Biochemical and cellular properties of insulin receptor signalling

The mechanism of insulin action is a central theme in biology and medicine. In addition to the rather rare condition of insulin deficiency caused by autoimmune destruction of pancreatic β-cells, genetic and acquired abnormalities of insulin action underlie the far more common conditions of type 2 diabetes, obesity and insulin resistance. The latter predisposes to diseases ranging from hypertension to Alzheimer disease and cancer. Hence, understanding the biochemical and cellular properties of insulin receptor signalling is arguably a priority in biomedical research. In the past decade, major progress has led to the delineation of mechanisms of glucose transport, lipid synthesis, storage and mobilization. In addition to direct effects of insulin on signalling kinases and metabolic enzymes, the discovery of mechanisms of insulin-regulated gene transcription has led to a reassessment of the general principles of insulin action. These advances will accelerate the discovery of new treatment modalities for diabetes.

New lipid interaction partners stimulate the inhibition of activated protein C by cell-penetrating protein C inhibitor

Protein C inhibitor (PCI, SerpinA5) is a heparin-binding serpin which can penetrate through cellular membranes. Selected negatively charged phospholipids like unsaturated phosphatidylserine and oxidised phosphatidylethanolamine bind to PCI and stimulate its inhibitory activity towards different proteases. The interaction of phospholipids with PCI might also alter the lipid distribution pattern of blood cells and influence the remodelling of cellular membranes. Here we showed that PCI is an additional binding partner of phosphatidic acid (PA), cardiolipin (CL), and phosphoinositides (PIPs). Protein lipid overlay assays exhibited a unique binding pattern of PCI towards different lipid species. In addition PA, CL, and unsaturated, monophosphorylated PIPs stimulated the inhibitory property of PCI towards activated protein C in a heparin like manner. As shown for kallistatin (SerpinA4) and vaspin (SerpinA12), the incubation of cells with PCI led to the activation of protein kinase B (AKT), which could be achieved through direct interaction of PCI with PIPs. This model is supported by the fact that PCI stimulated the PIP-dependent 5-phosphatase SHIP2 in vitro, which would result in AKT activation. Hence the interaction of PCI with different lipids might not only stimulate the inhibition of potential target protease by PCI, but could also alter intracellular lipid signalling.

Endothelial SHIP2 Suppresses Nox2 NADPH Oxidase-Dependent Vascular Oxidative Stress, Endothelial Dysfunction, and Systemic Insulin Resistance

Shc homology 2-containing inositol 5' phosphatase-2 (SHIP2) is a lipid phosphatase that inhibits insulin signaling downstream of phosphatidylinositol 3-kinase (PI3K); its role in vascular function is poorly understood. To examine its role in endothelial cell (EC) biology, we generated mice with catalytic inactivation of one SHIP2 allele selectively in ECs (ECSHIP2^Δ/+). Hyperinsulinemic-euglycemic clamping studies revealed that ECSHIP2^Δ/+ was resistant to insulin-stimulated glucose uptake in adipose tissue and skeletal muscle compared with littermate controls. ECs from ECSHIP2^Δ/+ mice had increased basal expression and activation of PI3K downstream targets, including Akt and endothelial nitric oxide synthase, although incremental activation by insulin and shear stress was impaired. Insulin-mediated vasodilation was blunted in ECSHIP2^Δ/+ mice, as was aortic nitric oxide bioavailability. Acetylcholine-induced vasodilation was also impaired in ECSHIP2^Δ/+ mice, which was exaggerated in the presence of a superoxide dismutase/catalase mimetic. Superoxide abundance was elevated in ECSHIP2^Δ/+ ECs and was suppressed by PI3K and NADPH oxidase 2 inhibitors. These findings were phenocopied in healthy human ECs after SHIP2 silencing. Our data suggest that endothelial SHIP2 is required to maintain normal systemic glucose homeostasis and prevent oxidative stress-induced endothelial dysfunction.

Structural basis for interdomain communication in SHIP2 providing high phosphatase activity

SH2-containing-inositol-5-phosphatases (SHIPs) dephosphorylate the 5-phosphate of phosphatidylinositol-3,4,5-trisphosphate (PI(3,4,5)P₃) and play important roles in regulating the PI3K/Akt pathway in physiology and disease. Aiming to uncover interdomain regulatory mechanisms in SHIP2, we determined crystal structures containing the 5-phosphatase and a proximal region adopting a C2 fold. This reveals an extensive interface between the two domains, which results in significant structural changes in the phosphatase domain. Both the phosphatase and C2 domains bind phosphatidylserine lipids, which likely helps to position the active site towards its substrate. Although located distant to the active site, the C2 domain greatly enhances catalytic turnover. Employing molecular dynamics, mutagenesis and cell biology, we identify two distinct allosteric signaling pathways, emanating from hydrophobic or polar interdomain interactions, differentially affecting lipid chain or headgroup moieties of PI(3,4,5)P₃. Together, this study reveals details of multilayered C2-mediated effects important for SHIP2 activity and points towards interesting new possibilities for therapeutic interventions.

DOI:http://dx.doi.org/10.7554/eLife.26640.001

Biofluid lipidome: a source for potential diagnostic biomarkers

Lipidomics is the identification and quantitation of changes in the lipidome of a cell, tissue, organ or biofluid in health and disease using high resolution mass spectrometry. Lipidome of a particular organism has relevance to the disease manifestation as it reflects the metabolic changes which can be a consequence of the disease. Hence these changes in the molecules can be considered as potential markers for screening and early detection of the disease. Biological fluids as blood/serum/plasma, urine, saliva, tear and cerebrospinal fluid, due to their accessibility, offer ease of collection with minimal or no discomfort to the patient and provide a ready footprint of the metabolic changes occurring during disease. This review provides a brief introduction to lipidomics and its role in understanding the metabolic changes in health and disease followed by discussion on the chemical diversity of the lipid species and their biological role, mammalian lipids and their metabolism and role of lipids in pathogens and the immune response before dwelling further into importance of studying lipidome in various biological fluids. The challenges in performing a lipidomic analysis at the experimental and data analysis stages are discussed.

Insulin signalling and glucose transport in the ovary and ovarian function during the ovarian cycle

Data derived principally from peripheral tissues (fat, muscle and liver) show that insulin signals via diverse interconnecting intracellular pathways and that some of the major intersecting points (known as critical nodes) are the IRSs (insulin receptor substrates), PI3K (phosphoinositide kinase)/Akt and MAPK (mitogen-activated protein kinase). Most of these insulin pathways are probably also active in the ovary and their ability to interact with each other and also with follicle-stimulating hormone (FSH) and luteinizing hormone (LH) signalling pathways enables insulin to exert direct modulating influences on ovarian function. The present paper reviews the intracellular actions of insulin and the uptake of glucose by ovarian tissues (granulosa, theca and oocyte) during the oestrous/menstrual cycle of some rodent, primate and ruminant species. Insulin signals through diverse pathways and these are discussed with specific reference to follicular cell types (granulosa, theca and oocyte). The signalling pathways for FSH in granulosa cells and LH in granulosa and theca cells are summarized. The roles of glucose and of insulin-mediated uptake of glucose in folliculogenesis are discussed. It is suggested that glucose in addition to its well-established role of providing energy for cellular function may also have insulin-mediated signalling functions in ovarian cells, involving AMPK (AMP-dependent protein kinase) and/or hexosamine. Potential interactions of insulin signalling with FSH or LH signalling at critical nodes are identified and the available evidence for such interactions in ovarian cells is discussed. Finally the action of the insulin-sensitizing drugs metformin and the thiazolidinedione rosiglitazone on follicular cells is reviewed.

PI3K/SHIP2/PTEN pathway in cell polarity and hepatitis C virus pathogenesis

Hepatitis C virus (HCV) infects hepatocytes, polarized cells in the liver. Chronic HCV infection often leads to steatosis, fibrosis, cirrhosis and hepatocellular carcinoma, and it has been identified as the leading cause of liver transplantation worldwide. The HCV replication cycle is dependent on lipid metabolism and particularly an accumulation of lipid droplets in host cells. Phosphoinositides (PIs) are minor phospholipids enriched in different membranes and their levels are tightly regulated by specific PI kinases and phosphatases. PIs are implicated in a vast array of cellular responses that are central to morphogenesis, such as cytoskeletal changes, cytokinesis and the recruitment of downstream effectors to govern mechanisms involved in polarization and lumen formation. Important reviews of the literature identified phosphatidylinositol (PtdIns) 4-kinases, and their lipid products PtdIns(4)P, as critical regulators of the HCV life cycle. SH2-containing inositol polyphosphate 5-phosphatase (SHIP2), phosphoinositide 3-kinase (PI3K) and their lipid products PtdIns(3,4)P2 and PtdIns(3,4,5)P3, respectively, play an important role in the cell membrane and are key to the establishment of apicobasal polarity and lumen formation. In this review, we will focus on these new functions of PI3K and SHIP2, and their deregulation by HCV, causing a disruption of apicobasal polarity, actin organization and extracellular matrix assembly. Finally we will highlight the involvement of this pathway in the event of insulin resistance and nonalcoholic fatty liver disease related to HCV infection.

miR-184 exhibits angiostatic properties via regulation of Akt and VEGF signaling pathways

Corneal avascularity is critical for achieving transparency necessary for proper transmission of light to the lens and visual acuity. Although much is known about angiogenesis and angiostasis, the precise regulation of these processes in the cornea is unclear. MicroRNA (miR)-184, the most abundant corneal epithelial miRNA, has been suggested to function in corneal angiostasis by altering VEGF signaling; however, the mechanism(s) underlying this regulation have not been addressed. Using a combination of in vitro and in vivo assays to evaluate angiogenesis, we demonstrated that human limbal epithelial keratinocytes (HLEKs) engineered to overexpress miR-184 secreted lower amounts of angiogenic mitogens. Human dermal microvascular cells exposed to conditioned medium from miR-184-overexpressing HLEKs were less proliferative and failed to seal linear scratch wounds. The in vivo Matrigel plug assay showed that conditioned medium from miR-184-expressing HLEKs elicited a lesser degree of neovascularization compared with controls. We found that miR-184 directly targets and represses the proangiogenic factors, friend of Gata 2 (FOG2), platelet-derived growth factor (PDGF)-β, and phosphatidic acid phosphatase 2b (PPAP2B). FOG2 regulates VEGF expression, whereas PDGF-β and PPAP2B regulate Akt activity. By attenuating both VEGF and Akt signaling, miR-184 acts as a broad-spectrum negative regulator of corneal angiogenesis.-Park, J. K., Peng, H., Yang, W., Katsnelson, J., Volpert, O., Lavker, R. M. miR-184 exhibits angiostatic properties via regulation of Akt and VEGF signaling pathways.

FcγRIIb-SHIP2 axis links Aβ to tau pathology by disrupting phosphoinositide metabolism in Alzheimer's disease model

Amyloid-β (Aβ)-containing extracellular plaques and hyperphosphorylated tau-loaded intracellular neurofibrillary tangles are neuropathological hallmarks of Alzheimer's disease (AD). Although Aβ exerts neuropathogenic activity through tau, the mechanistic link between Aβ and tau pathology remains unknown. Here, we showed that the FcγRIIb-SHIP2 axis is critical in Aβ_1-42-induced tau pathology. Fcgr2b knockout or antagonistic FcγRIIb antibody inhibited Aβ_1-42-induced tau hyperphosphorylation and rescued memory impairments in AD mouse models. FcγRIIb phosphorylation at Tyr273 was found in AD brains, in neuronal cells exposed to Aβ_1-42, and recruited SHIP2 to form a protein complex. Consequently, treatment with Aβ_1-42 increased PtdIns(3,4)P₂ levels from PtdIns(3,4,5)P₃ to mediate tau hyperphosphorylation. Further, we found that targeting SHIP2 expression by lentiviral siRNA in 3xTg-AD mice or pharmacological inhibition of SHIP2 potently rescued tau hyperphosphorylation and memory impairments. Thus, we concluded that the FcγRIIb-SHIP2 axis links Aβ neurotoxicity to tau pathology by dysregulating PtdIns(3,4)P₂ metabolism, providing insight into therapeutic potential against AD.

INPPL1 gene mutations in opsismodysplasia

The INPPL1 (inositol polyphosphate phosphatase-like 1) gene encodes the inositol phosphatase, SHIP2 (for src homology 2 domain-containing inositol phosphatase 2). SHIP2 functions to dephosphorylate, and negatively regulate, the lipid second messenger phosphatidylinositol (3,4,5)P3. SHIP2 has been well studied in the area of insulin resistance and obesity but has roles in cancer and other disorders. Recently, it was reported that mutations in INPPL1 cause opsismodysplasia, a rare, autosomal recessive severe skeletal dysplasia. This review focuses on the mutations associated with opsismodysplasia and explores the role of INPPL1/ SHIP2 in skeletal development.