Inositol Polyphosphate Multikinase Inhibits Angiogenesis via Inositol Pentakisphosphate-Induced HIF-1α Degradation

Preconditioning with Ginsenoside Rg3 mitigates cardiac injury induced by high-altitude hypobaric hypoxia exposure in mice by suppressing ferroptosis through inhibition of the RhoA/ROCK signaling pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Ginseng has historically been utilized as a conventional herbal remedy and dietary supplement to enhance physical stamina and alleviate fatigue. The primary active component of Ginseng, Ginsenoside Rg3 (GS-Rg3), possesses diverse pharmacological properties including immune modulation and anti-inflammatory effects. Furthermore, GS-Rg3 has demonstrated efficacy in mitigating tissue and organ damage associated with metabolic disorders such as hypertension, hyperglycemia, and hyperlipidemia. Nevertheless, its potential impact on high-altitude cardiac injury (HACI) remains insufficiently explored.

AIM OF THE STUDY

The aim of this study was to examine the potential cardioprotective effects of Ginsenoside Rg3, and to investigate how Ginsenoside Rg3 preconditioning can enhance high-altitude cardiac injury by inhibiting the RhoA/ROCK pathway and ferroptosis in cardiac tissue. The findings of this study may contribute to the development of novel therapeutic strategies using traditional Chinese medicine for high-altitude cardiac injury, based on experimental evidence.

MATERIALS AND METHODS

A hypobaric hypoxia chamber was employed to simulate hypobaric hypoxia conditions equivalent to an altitude of 6000 m. Through a randomization process, groups of six male mice were assigned to receive either saline, Ginsenoside Rg3 at doses of 15 mg/kg or 30 mg/kg, or lysophosphatidic acid (LPA) at 1 mg/kg. The impact of Ginsenoside Rg3 on high altitude-induced arrhythmias was evaluated using electrocardiography. Cardiac pathology sections stained with hematoxylin and eosin were evaluated for damage, with the extent of cardiomyocyte damage observed via transmission electron microscopy. The impact of Ginsenoside Rg3 on high-altitude cardiac injury was investigated through analysis of serum biomarkers for cardiac injury (CK-MB, BNP), inflammatory cytokines (TNF, IL-6, IL-1β), reactive oxygen species (ROS) and glutathione (GSH). The expression levels of hypoxia and hypoxia-related proteins in myocardial tissues from each experimental group were assessed using Western blot analysis. Following a review of the existing literature, the traditional regulatory mechanisms of ferroptosis were examined. Immunofluorescence staining of cardiac tissues and Western blotting techniques were utilized to investigate the impact of Ginsenoside Rg3 on cardiomyocyte ferroptosis through the RhoA/ROCK signaling pathway under conditions of hypobaric hypoxia exposure.

RESULTS

Pre-treatment with Ginsenoside Rg3 improved high altitude-induced arrhythmias, reduced cardiomyocyte damage, decreased cardiac injury biomarkers and inflammatory cytokines, and lowered the expression of hypoxia-related proteins in myocardial tissues. Both Western blotting and immunofluorescence staining of cardiac tissues demonstrated that exposure to high-altitude hypobaric hypoxia results in elevated expression of ferroptosis and proteins related to the RhoA/ROCK pathway. Experimental validation corroborated that the role of the RhoA/ROCK signaling pathway in mediating ferroptosis.

CONCLUSIONS

The findings of our study suggest that preconditioning with Ginsenoside Rg3 may attenuate cardiac injury caused by high-altitude hypobaric hypoxia exposure in mice by inhibiting ferroptosis through the suppression of the RhoA/ROCK signaling pathway. These findings contribute to the current knowledge of Ginsenoside Rg3 and high-altitude cardiac injury, suggesting that Ginsenoside Rg3 shows potential as a therapeutic agent for high-altitude cardiac injury.

The inositol phosphate signalling network in physiology and disease

Combinatorial substitution of phosphate groups on the inositol ring gives rise to a plethora of inositol phosphates (InsPs) and inositol pyrophosphates (PP-InsPs). These small molecules constitute an elaborate metabolic and signalling network that influences nearly every cellular function. This review delves into the knowledge accumulated over the past decades regarding the biochemical principles and significance of InsP metabolism. We focus on the biological actions of InsPs in mammals, with an emphasis on recent findings regarding specific target proteins. We further discuss the roles of InsP metabolism in contributing to physiological homeostasis and pathological conditions. A deeper understanding of InsPs and their metabolic pathways holds the potential to address unresolved questions and propel advances towards therapeutic applications.

Combining systems pharmacology, metabolomics, and transcriptomics to reveal the mechanism of Salvia miltiorrhiza-Cortex moutan herb pair for the treatment of ischemic stroke

Ischemic stroke (IS), predominantly triggered by blockages in cerebral blood flow, is increasingly recognized as a critical public health issue. The combination of Salvia miltiorrhiza (SM) and Cortex moutan (CM), traditional herbs in Eastern medicine, are frequently used for managing heart and brain vascular conditions. However, the exact mechanisms by which this herb pair (SC) combats IS remain largely unexplored. This investigation focuses on pinpointing the active constituents in SC that contribute to its protective role and deciphering the mechanisms countering cerebral ischemia, particularly in a middle cerebral artery occlusion (MCAO) rat model. We employed UPLC-Q-TOF-MS/MS alongside network pharmacology for predicting SC's target actions against IS. Key ingredients were examined for their interaction with principal targets using molecular docking. The therapeutic impact was gauged through H&E, TUNEL, and Nissl staining, complemented by transcriptomic and metabolomic integration for mechanistic insights, with vital genes confirmed via western blot. UPLC-Q-TOF-MS/MS analysis revealed that the main components of SC included benzoylpaeoniflorin, salvianolic acid B, oxypaeoniflora, salvianolic acid A, and others. Network pharmacology analysis indicated that SC's mechanism in treating IS primarily involves inflammation, angiogenesis, and cell apoptosis-related pathways, potentially through targets such as AKT1, TNF, PTGS2, MMP9, PIK3CA, and VEGFA. Molecular docking underscored strong affinities between these constituents and their targets. Our empirical studies indicated SC's significant role in enhancing neuroprotection in IS, with transcriptomics suggesting the involvement of the VEGFA/PI3K/AKT pathway and metabolomics revealing improvements in various metabolic processes, including amino acids, glycerophospholipids, sphingomyelin, and fatty acids metabolisms.

Genetic influence on scar vascularity after burn injury in individuals of European ancestry: A prospective cohort study

After burn injury there is considerable variation in scar outcome, partially due to genetic factors. Scar vascularity is one characteristic that varies between individuals, and this study aimed to identify genetic variants contributing to different scar vascularity outcomes. An exome-wide array association study and gene pathway analysis was performed on a prospective cohort of 665 patients of European ancestry treated for burn injury, using their scar vascularity (SV) sub-score, part of the modified Vancouver Scar Scale (mVSS), as an outcome measure. DNA was genotyped using the Infinium HumanCoreExome-24 BeadChip, imputed to the Haplotype Reference Consortium panel. Associations between genetic variants (single nucleotide polymorphisms) and SV were estimated using an additive genetic model adjusting for sex, age, % total body surface area and number of surgical procedures, utilising linear and multinomial logistic regression. No individual genetic variants achieved the cut-off threshold for significance. Gene sets were also analysed using the Functional Mapping and Annotation (FUMA) platform, in which biological processes indirectly related to angiogenesis were significantly represented. This study suggests that SNPs in genes associated with angiogenesis may influence SV, but further studies with larger datasets are essential to validate these findings.

HIF-2α inhibition disrupts leukemia stem cell metabolism and impairs vascular microenvironment to enhance chronic myeloid leukemia treatment

Leukemic stem cells (LSCs) in chronic myeloid leukemia (CML) contribute to treatment resistance and disease recurrence. Metabolism regulates LSCs, but the mechanisms remain elusive. Here, we show that hypoxia-inducible factor 2α (HIF-2α) is highly expressed in LSCs in mouse and human CML and increases after tyrosine kinase inhibitor (TKI) treatment. Deletion of HIF-2α suppresses disease progression, reduces LSC numbers, and enhances the efficacy of TKI treatment in BCL-ABL-induced CML mice. Mechanistically, HIF-2α deletion reshapes the metabolic profile of LSCs, leading to increased production of reactive oxygen species (ROS) and apoptosis in CML. Moreover, HIF-2α deletion decreases vascular endothelial growth factor (VEGF) expression, thereby suppressing neovascularization in the bone marrow of CML mice. Furthermore, pharmaceutical inhibition of HIF-2α by PT2399 attenuates disease progression and improves the efficacy of TKI treatment in both mouse and human CML. Overall, our findings highlight the role of HIF-2α in controlling the metabolic state and vascular niche remodeling in CML, suggesting it is a potential therapeutic target to enhance TKI therapy.

Nuclear phosphoinositide signaling promotes YAP/TAZ-TEAD transcriptional activity in breast cancer

The Hippo pathway effectors Yes-associated protein 1 (YAP) and its homolog TAZ are transcriptional coactivators that control gene expression by binding to TEA domain (TEAD) family transcription factors. The YAP/TAZ-TEAD complex is a key regulator of cancer-specific transcriptional programs, which promote tumor progression in diverse types of cancer, including breast cancer. Despite intensive efforts, the YAP/TAZ-TEAD complex in cancer has remained largely undruggable due to an incomplete mechanistic understanding. Here, we report that nuclear phosphoinositides function as cofactors that mediate the binding of YAP/TAZ to TEADs. The enzymatic products of phosphoinositide kinases PIPKIα and IPMK, including phosphatidylinositol 4,5-bisphosphate (PI(4,5)P2) and phosphatidylinositol 3,4,5-trisphosphate (P(I3,4,5)P3), bridge the binding of YAP/TAZ to TEAD. Inhibiting these kinases or the association of YAP/TAZ with PI(4,5)P2 and PI(3,4,5)P3 attenuates YAP/TAZ interaction with the TEADs, the expression of YAP/TAZ target genes, and breast cancer cell motility. Although we could not conclusively exclude the possibility that other enzymatic products of IPMK such as inositol phosphates play a role in the mechanism, our results point to a previously unrecognized role of nuclear phosphoinositide signaling in control of YAP/TAZ activity and implicate this pathway as a potential therapeutic target in YAP/TAZ-driven breast cancer.

Functions, Mechanisms, and therapeutic applications of the inositol pyrophosphates 5PP-InsP5 and InsP8 in mammalian cells

Water-soluble myo-inositol phosphates have long been characterized as second messengers. The signaling properties of these compounds are determined by the number and arrangement of phosphate groups on the myo-inositol backbone. Recently, higher inositol phosphates with pyrophosphate groups were recognized as signaling molecules. 5-Diphosphoinositol 1,2,3,4,6-pentakisphosphate (5PP-InsP5) is the most abundant isoform, constituting more than 90% of intracellular inositol pyrophosphates. 5PP-InsP5 can be further phosphorylated to 1,5-bisdiphosphoinositol 2,3,4,6-tetrakisphosphate (InsP8). These two molecules, 5PP-InsP5 and InsP8, are present in various subcellular compartments, where they participate in regulating diverse cellular processes such as cell death, energy homeostasis, and cytoskeletal dynamics. The synthesis and metabolism of inositol pyrophosphates are subjected to tight regulation, allowing for their highly specific functions. Blocking the 5PP-InsP5/InsP8 signaling pathway by inhibiting the biosynthesis of 5PP-InsP5 demonstrates therapeutic benefits in preclinical studies, and thus holds promise as a therapeutic approach for certain diseases treatment, such as metabolic disorders.

Pretreatment with Notoginsenoside R1 attenuates high-altitude hypoxia-induced cardiac injury via activation of the ERK1/2-P90RSK-Bad signaling pathway in rats

High-altitude cardiac injury (HACI) is one of the common tissue injuries caused by high-altitude hypoxia that may be life threatening. Notoginsenoside R1 (NG-R1), a major saponin of Panax notoginseng, exerts anti-oxidative, anti-inflammatory, and anti-apoptosis effects, protecting the myocardium from hypoxic injury. This study aimed to investigate the protective effect and molecular mechanism of NG-R1 against HACI. We simulated a 6000 m environment for 48 h in a hypobaric chamber to create a HACI rat model. Rats were pretreated with NG-R1 (50, 100 mg/kg) or dexamethasone (4 mg/kg) for 3 days and then placed in the chamber for 48 h. The effect of NG-R1 was evaluated by changes in Electrocardiogram parameters, histopathology, cardiac biomarkers, oxidative stress and inflammatory indicators, key protein expression, and immunofluorescence. U0126 was used to verify whether the anti-apoptotic effect of NG-R1 was related to the activation of ERK pathway. Pretreatment with NG-R1 can improve abnormal cardiac electrical conduction and alleviate high-altitude-induced tachycardia. Similar to dexamethasone, NG-R1 can improve pathological damage, reduce the levels of cardiac injury biomarkers, oxidative stress, and inflammatory indicators, and down-regulate the expression of hypoxia-related proteins HIF-1α and VEGF. In addition, NG-R1 reduced cardiomyocyte apoptosis by down-regulating the expression of apoptotic proteins Bax, cleaved caspase 3, cleaved caspase 9, and cleaved PARP1 and up-regulating the expression of anti-apoptotic protein Bcl-2 through activating the ERK1/2-P90RSK-Bad pathway. In conclusion, NG-R1 prevented HACI and suppressed apoptosis via activation of the ERK1/2-P90RSK-Bad pathway, indicating that NG-R1 has therapeutic potential to treat HACI.

Inositol polyphosphate multikinase modulates redox signaling through nuclear factor erythroid 2-related factor 2 and glutathione metabolism

Maintenance of redox balance plays central roles in a plethora of signaling processes. Although physiological levels of reactive oxygen and nitrogen species are crucial for functioning of certain signaling pathways, excessive production of free radicals and oxidants can damage cell components. The nuclear factor erythroid 2-related factor 2 (Nrf2) signaling cascade is the key pathway that mediates cellular response to oxidative stress. It is controlled at multiple levels, which serve to maintain redox homeostasis within cells. We show here that inositol polyphosphate multikinase (IPMK) is a modulator of Nrf2 signaling. IPMK binds Nrf2 and attenuates activation and expression of Nrf2 target genes. Furthermore, depletion of IPMK leads to elevated glutathione and cysteine levels, resulting in increased resistance to oxidants. Accordingly, targeting IPMK may restore redox balance under conditions of cysteine and glutathione insufficiency.

Identification of key pathways, genes and immune cell infiltration in hypoxia of high-altitude acclimatization via meta-analysis and integrated bioinformatics analysis

Background: For individuals acutely exposed to high-altitude regions, environmental hypobaric hypoxia induces several physiological or pathological responses, especially immune dysfunction. Therefore, hypoxia is a potentially life-threatening factor, which has closely related to high-altitude acclimatization. However, its specific molecular mechanism is still unclear. Methods: The four expression profiles about hypoxia and high altitude were downloaded from the Gene Expression Omnibus database in this study. Meta-analysis of GEO datasets was performed by NetworkAnalyst online tool. Kyoto Encyclopedia of Genes and Genomes (KEGG), Gene ontology (GO) enrichment analysis, and visualization were performed using R (version 4.1.3) software, respectively. The CIBERSORT analysis was conducted on GSE46480 to examine immune cell infiltration. In addition, we experimentally verified the bioinformatics analysis with qRT-PCR. Results: The meta-analysis identified 358 differentially expressed genes (DEGs), with 209 upregulated and 149 downregulated. DEGs were mostly enriched in biological processes and pathways associated with hypoxia acclimatization at high altitudes, according to both GO and KEGG enrichment analyses. ERH, VBP1, BINP3L, TOMM5, PSMA4, and POLR2K were identified by taking intersections of the DEGs between meta-analysis and GSE46480 and verified by qRT-PCR experiments, which were inextricably linked to hypoxia. Immune infiltration analysis showed significant differences in immune cells between samples at sea level and high altitudes. Conclusion: Identifying the DEGs and pathways will improve our understanding of immune function during high-altitude hypoxia at a molecular level. Targeting hypoxia-sensitive pathways in immune cells is interesting in treating high-altitude sickness. This study provides support for further research on high-altitude acclimatization.

HSPA12A Stimulates p38/ERK-AP-1 Signaling to Promote Angiogenesis and Is Required for Functional Recovery Postmyocardial Infarction

Angiogenesis plays a critical role in wound healing postmyocardial infarction (MI). However, there is still a lack of ideal angiogenic therapeutics for rescuing ischemic hearts clinically, suggesting that a more understanding regarding angiogenesis regulation is urgently needed. Heat shock protein A12A (HSPA12A) is an atypical member of the HSP70 family. Here, we demonstrated that HSPA12A was upregulated during endothelial tube formation, a characteristic of in vitro angiogenesis. Intriguingly, overexpression of HSPA12A promoted in vitro angiogenic characteristics including proliferation, migration, and tube formation of endothelial cells. By contrast, deficiency of HSPA12A impaired myocardial angiogenesis and worsened cardiac dysfunction post-MI in mice. The expression of genes related to angiogenesis (VEGF, VEGFR2, and Ang-1) was decreased by HSPA12A deficiency in MI hearts of mice, whereas their expression was increased by HSPA12A overexpression in endothelial cells. HSPA12A overexpression in endothelial cells increased phosphorylation levels and nuclear localization of AP-1, a transcription factor dominating angiogenic gene expression. Also, HSPA12A increased p38 and ERK phosphorylation levels, whereas inhibition of p38 or ERKs diminished the HSPA12A-promoted AP-1 phosphorylation and nuclear localization, as well as VEGF and VEGFR2 expression in endothelial cells. Notably, inhibition of either p38 or ERKs diminished the HSPA12A-promoted in vitro angiogenesis characteristics. The findings identified HSPA12A as a novel angiogenesis activator, and HSPA12A might represent a viable strategy for the management of myocardial healing in patients with ischemic heart diseases.

The Inositol Phosphate System-A Coordinator of Metabolic Adaptability

All cells rely on nutrients to supply energy and carbon building blocks to support cellular processes. Over time, eukaryotes have developed increasingly complex systems to integrate information about available nutrients with the internal state of energy stores to activate the necessary processes to meet the immediate and ongoing needs of the cell. One such system is the network of soluble and membrane-associated inositol phosphates that coordinate the cellular responses to nutrient uptake and utilization from growth factor signaling to energy homeostasis. In this review, we discuss the coordinated interactions of the inositol polyphosphates, inositol pyrophosphates, and phosphoinositides in major metabolic signaling pathways to illustrate the central importance of the inositol phosphate signaling network in nutrient responses.

Human cell receptors: potential drug targets to combat COVID-19

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) causes the coronavirus disease 2019 (COVID-19). The World Health Organization (WHO) has announced that COVID-19 is a pandemic having a higher spread rate rather than the mortality. Identification of a potential approach or therapy against COVID-19 is still under consideration. Therefore, it is essential to have an insight into SARS-CoV-2, its interacting partner, and domains for an effective treatment. The present study is divided into three main categories, including SARS-CoV-2 prominent receptor and its expression levels, other interacting partners, and their binding domains. The first section focuses primarily on coronaviruses' general aspects (SARS-CoV-2, SARS-CoV, and the Middle East Respiratory Syndrome Coronaviruses (MERS-CoV)) their structures, similarities, and mode of infections. The second section discusses the host receptors which includes the human targets of coronaviruses like dipeptidyl peptidase 4 (DPP4), CD147, CD209L, Angiotensin-Converting Enzyme 2 (ACE2), and other miscellaneous targets (type-II transmembrane serine proteases (TTSPs), furin, trypsin, cathepsins, thermolysin, elastase, phosphatidylinositol 3-phosphate 5-kinase, two-pore segment channel, and epithelium sodium channel C-α subunit). The human cell receptor, ACE2 plays an essential role in the Renin-Angiotensin system (RAS) pathway and COVID-19. Thus, this section also discusses the ACE2 expression and risk of COVID-19 infectivity in various organs and tissues such as the liver, lungs, intestine, heart, and reproductive system in the human body. Absence of ACE2 protein expression in immune cells could be used for limiting the SARS-CoV-2 infection. The third section covers the current available approaches for COVID-19 treatment. Overall, this review focuses on the critical role of human cell receptors involved in coronavirus pathogenesis, which would likely be used in designing target-specific drugs to combat COVID-19.

Inositol Polyphosphate Multikinase Signaling: Multifaceted Functions in Health and Disease

Inositol phosphates are water-soluble intracellular signaling molecules found in eukaryotes from yeasts to mammals, which are synthesized by a complex network of enzymes including inositol phosphate kinases. Among these, inositol polyphosphate multikinase (IPMK) is a promiscuous enzyme with broad substrate specificity, which phosphorylates multiple inositol phosphates, as well as phosphatidylinositol 4,5-bisphosphate. In addition to its catalytic actions, IPMK is known to non-catalytically control major signaling events via direct protein-protein interactions. In this review, we describe the general characteristics of IPMK, highlight its pleiotropic roles in various physiological and pathological conditions, and discuss future challenges in the field of IPMK signaling pathways.

Inositol polyphosphate multikinase IPMK-1 regulates development through IP3/calcium signaling in Caenorhabditis elegans

Inositol polyphosphate multikinase (IPMK) is a conserved protein that initiates the production of inositol phosphate intracellular messengers and is critical for regulating a variety of cellular processes. Here, we report that the C. elegans IPMK-1, which is homologous to the mammalian inositol polyphosphate multikinase, plays a crucial role in regulating rhythmic behavior and development. The deletion mutant ipmk-1(tm2687) displays a long defecation cycle period and retarded postembryonic growth. The expression of functional ipmk-1::GFP was detected in the pharyngeal muscles, amphid sheath cells, the intestine, excretory (canal) cells, proximal gonad, and spermatheca. The expression of IPMK-1 in the intestine was sufficient for the wild-type phenotype. The IP3-kinase activity of IPMK-1 is required for defecation rhythms and postembryonic development. The defective phenotypes of ipmk-1(tm2687) could be rescued by a loss-of-function mutation in type I inositol 5-phosphatase homolog (IPP-5) and improved by a supplemental Ca²⁺ in the medium. Our work demonstrates that IPMK-1 and the signaling molecule inositol triphosphate (IP3) pathway modulate rhythmic behaviors and development by dynamically regulating the concentration of intracellular Ca²⁺ in C. elegans. Advances in understanding the molecular regulation of Ca²⁺ homeostasis and regulation of organism development may lead to therapeutic strategies that modulate Ca²⁺ signaling to enhance function and counteract disease processes. Unraveling the physiological role of IPMK and the underlying functional mechanism in C. elegans would contribute to understanding the role of IPMK in other species, especially in mammals, and benefit further research on the involvement of IPMK in disease.

Semaphorin 3A-hypoxia inducible factor 1 subunit alpha co-overexpression enhances the osteogenic differentiation of induced pluripotent stem cells-derived mesenchymal stem cells in vitro

Background:

Mesenchymal stem or stromal cells (MSCs) derived from the induced pluripotent stem cells (iPSCs) have uniform biological activity, which makes the clinical application of MSCs in bone repair possible. Culturing the iPSC-MSCs onto osteoconductive materials is a promising tissue engineering-based strategy in bone regeneration. The aim of this work was to evaluate the effects of semaphorin 3A (Sema3A) and hypoxia inducible factor 1 subunit alpha (HIF1α) co-overexpression on the survival and osteogenic differentiation of iPSC-MSCs.

Methods:

Sema3A and HIF1α were linked together with the three (GGGGS; G, glycine; S, serine) peptide fragment, and their co-expression in iPSC-MSCs was mediated by a lentiviral vector. The fusion protein retained the immune reactivity for both Sema3A and HIF1α as determined with Western blotting. iPSC-MSCs were infected with overexpression lentivirus (oeLenti) as negative control, oeLenti-Sema3A, oeLenti-HIF1α or oeLenti-Sema3A-HIF1α lentiviruses.

Results:

Sema3A overexpression alone promoted the osteogenic differentiation of iPSC-MSCs (the activity and/or expression of osteoblast markers, such as alkaline phosphatase, osteopontin, and osteocalcin, were upregulated), and suppressed cell survival. The Sema3A-HIF1α fusion protein showed a comparable osteoconductive effect to that of Sema3A without reducing cell survival. We further seeded iPSC-MSCs modified by SemaA-HIF1α overexpression onto hydroxyapatite (HA) scaffolds, and evaluated their growth and differentiation on this three-dimensional material. Additional data indicated that, as compared to iPSC-MSCs cultured in ordinary two-dimensional dishes, cells cultured in HA scaffolds grew (blank vs. HA scaffolds: 0.83 vs. 1.39 for survival) and differentiated better (blank vs. HA scaffolds: 11.29 vs. 16.62 for alkaline phosphatase activity).

Conclusion:

Modifying iPSC-MSCs with pro-osteogenic (Sema3A) and pro-survival (HIF1α) factors may represent a promising strategy to optimize tissue engineering-based strategy in bone repair.

HIF-1α Promotes the Metastasis of Esophageal Squamous Cell Carcinoma by Targeting SP1

Background: In microenvironment of malignant tumors, Hypoxia-Inducible Factors (HIF), most importantly HIF-1α, play an important role in regulation of adaptive biological response to hypoxia, promoting angiogenesis and metastasis. However, the underlying mechanism that HIF-1α regulates metastasis needs to be further clarified. Methods: The expressions of HIF-1α and SP1 were detected in 182 samples of esophageal squamous cell carcinoma (ESCC) and adjacent normal tissues by immunohistochemistry (IHC), and the correlation between the expression levels of HIF-1α and SP1 was analyzed. The expression of HIF-1α in ESCC cell lines TE1 and KYSE30 was then detected using qRT-PCR and western blot. The potential binding sites of HIF-1α on the SP1 promoter were analyzed using UCSC and JASPAR databases, verified by chromosomal immunoprecipitation (ChIP) assay and qRT-PCR. The effects of HIF-1α and SP1 on ESCC cell migration and invasion were then tested with Transwell and Matrigel experiments. Results: The expression of HIF-1α in cancer tissues is higher than adjacent normal tissues, and is correlated with metastasis, recurrence and poor prognosis. Upon silencing HIF-1α by siRNA, the invasion and migration ability of ESCC cells were significantly inhibited, which could be restored by the overexpression of SP1. Hypoxic conditions significantly increased the expression of HIF-1α and SP1 at both protein and mRNA levels in ESCC cells. HIF-1α enhanced SP1 transcription through binding to the promoter region. The expression of protein and mRNA levels of SP1 was decreased by silencing HIF-1α in cells. In contrast, overexpression of HIF-1α significantly increased the mRNA and protein levels of SP1. The expression of SP1 in ESCC was positively correlated with the protein expression of HIF-1α and poor prognosis. Conclusion: The results of our study indicate that HIF-1α promotes metastasis of ESCC by targeting SP1 in a hypoxic microenvironment. Further study on this mechanism may elucidate the possibility of HIF-1α and SP1 as new targets for the treatment of ESCC.

Structural analyses of inositol phosphate second messengers bound to signaling effector proteins

The higher-order inositol phosphate second messengers inositol tetrakisphosphate (IP4), inositol pentakisphosphate (IP5) and inositol hexakisphosphate (IP6) are important signaling molecules that regulate DNA-damage repair, cohesin dynamics, RNA-editing, retroviral assembly, nuclear transport, phosphorylation, acetylation, crotonylation, and ubiquitination. This functional diversity has made understanding how inositol polyphosphates regulate cellular processes challenging to dissect. However, some inositol phosphates have been unexpectedly found in X-ray crystal structures, occasionally revealing structural and mechanistic details of effector protein regulation before functional consequences have been described. This review highlights a sampling of crystal structures describing the interaction between inositol phosphates and protein effectors. This list includes the RNA editing enzyme "adenosine deaminase that acts on RNA 2" (ADAR2), the Pds5B regulator of cohesin dynamics, the class 1 histone deacetylases (HDACs) HDAC1 and HDAC3, and the PH domain of Bruton's tyrosine kinase (Btk). One of the most important enzymes responsible for higher-order inositol phosphate synthesis is inositol polyphosphate multikinase (IPMK), which plays dual roles in both inositol and phosphoinositide signaling. Structures of phosphoinositide lipid binding proteins have also revealed new aspects of protein effector regulation, as mediated by the nuclear receptors Steroidogenic Factor-1 (SF-1, NR5A2) and Liver Receptor Homolog-1 (LRH-1, NR5A2). Together, these studies underscore the structural diversity in binding interactions between effector proteins and inositol phosphate small signaling molecules, and further support that detailed structural studies can lead to new biological discovery.

Inositol polyphosphates promote T cell-independent humoral immunity via the regulation of Bruton's tyrosine kinase

T cell-independent (TI) B cell response is critical for the early protection against pathogen invasion. The regulation and activation of Bruton's tyrosine kinase (Btk) is known as a pivotal step of B cell antigen receptor (BCR) signaling in TI humoral immunity, as observed in patients with X-linked agammaglobulinemia (XLA) experiencing a high incidence of encapsulated bacterial infections. However, key questions remain as to whether a well-established canonical BCR signaling pathway is sufficient to regulate the activity of Btk. Here, we find that inositol hexakisphosphate (InsP6) acts as a physiological regulator of Btk in BCR signaling. Absence of higher order inositol phosphates (InsPs), inositol polyphosphates, leads to an inability to mount immune response against TI antigens. Interestingly, the significance of InsP6-mediated Btk regulation is more prominent in IgM+ plasma cells. Hence, the present study identifies higher order InsPs as principal components of B cell activation upon TI antigen stimulation and presents a mechanism for InsP-mediated regulation of the BCR signaling.

Inositol hexakisphosphate kinase 3 promotes focal adhesion turnover via interactions with dynein intermediate chain 2

Cells express a family of three inositol hexakisphosphate kinases (IP6Ks). Although sharing the same enzymatic activity, individual IP6Ks mediate different cellular processes. Here we report that IP6K3 is enriched at the leading edge of migrating cells where it associates with dynein intermediate chain 2 (DIC2). Using immunofluorescence microscopy and total internal reflection fluorescence microscopy, we found that DIC2 and IP6K3 are recruited interdependently to the leading edge of migrating cells, where they function coordinately to enhance the turnover of focal adhesions. Deletion of IP6K3 causes defects in cell motility and neuronal dendritic growth, eventually leading to brain malformations. Our results reveal a mechanism whereby IP6K3 functions in coordination with DIC2 in a confined intracellular microenvironment to promote focal adhesion turnover.