TNP and its analogs: Modulation of IP6K and CYP3A4 inhibition

Monitoring Intracellular IP6 with a Genetically Encoded Fluorescence Biosensor

Inositol hexakisphosphate (IP6), a naturally occurring metabolite of inositol with specific functions in different organelles or tissues, participates in numerous physiological processes and plays a key role in mammalian metabolic regulation. However, current IP6 detection methods, i.e., high-performance liquid chromatography and gel electrophoresis, require sample destruction and lack spatiotemporal resolution. Here, we construct and characterize a genetically encoded fluorescence biosensor named HIPSer that enables ratiometric quantitative IP6 detection in HEK293T cells and subcellular compartments. We demonstrate that HIPSer has a high sensitivity and relative selectivity for IP6 in vitro. We also provide proof-of-concept evidence that HIPSer can monitor IP6 levels in real time in HEK293T cells and can be targeted for IP6 detection in the nucleus of HEK293T cells. Moreover, HIPSer could also detect changes in IP6 content induced by chemical inhibition of IP6-metabolizing enzymes in HEK293T cells. Thus, HIPSer achieves spatiotemporally precise detection of fluctuations in endogenous IP6 in live cells and provides a versatile tool for mechanistic investigations of inositol phosphate functions in metabolism and signaling.

Fragment-Based Screening Identifies New Quinazolinone-Based Inositol Hexakisphosphate Kinase (IP6K) Inhibitors

A high-throughput fragment-based screen has been employed to discover a series of quinazolinone inositol hexakisphosphate kinase (IP6K) inhibitors. IP6Ks have been studied for their role in glucose homeostasis, metabolic disease, fatty liver disease, chronic kidney disease, blood coagulation, neurological development, and psychiatric disease. IP6Ks phosphorylate inositol hexakisphosphate (IP6) to form pyrophosphate 5-diphospho-1,2,3,4,6-pentakisphosphate (IP7). Molecular docking studies and investigation of structure-activity relationships around the quinazolinone core resulted in compounds with submicromolar potency and interesting selectivity for IP6K1 versus the closely related IP6K2 and IP6K3 isoforms.

The Role of Inositol Hexakisphosphate Kinase in the Central Nervous System

Inositol is a unique biological small molecule that can be phosphorylated or even further pyrophosphorylated on each of its six hydroxyl groups. These numerous phosphorylation states of inositol along with the kinases and phosphatases that interconvert them comprise the inositol phosphate signaling pathway. Inositol hexakisphosphate kinases, or IP6Ks, convert the fully mono-phosphorylated inositol to the pyrophosphate 5-IP7 (also denoted IP7). There are three isoforms of IP6K: IP6K1, 2, and 3. Decades of work have established a central role for IP6Ks in cell signaling. Genetic and pharmacologic manipulation of IP6Ks in vivo and in vitro has shown their importance in metabolic disease, chronic kidney disease, insulin signaling, phosphate homeostasis, and numerous other cellular and physiologic processes. In addition to these peripheral processes, a growing body of literature has shown the role of IP6Ks in the central nervous system (CNS). IP6Ks have a key role in synaptic vesicle regulation, Akt/GSK3 signaling, neuronal migration, cell death, autophagy, nuclear translocation, and phosphate homeostasis. IP6Ks' regulation of these cellular processes has functional implications in vivo in behavior and CNS anatomy.

Application of Inositol Hexaphosphate and Inositol in Dental Medicine: An Overview

Phosphorylated inositol hexaphosphate (IP6) is a naturally occurring carbohydrate, and its parent compound, myoinositol (Ins), is abundantly present in plants, particularly in certain high-fiber diets, but also in mammalian cells, where they regulate essential cellular functions. IP6 has profound modulation effects on macrophages, which warrants further research on the therapeutic benefits of IP6 for inflammatory diseases. Here, we review IP6 as a promising compound that has the potential to be used in various areas of dentistry, including endodontics, restorative dentistry, implantology, and oral hygiene products, due to its unique structure and characteristic properties. Available as a dietary supplement, IP6 + Ins has been shown to enhance the anti-inflammatory effect associated with preventing and suppressing the progression of chronic dental inflammatory diseases. IP6 in dentistry is now substantial, and this narrative review presents and discusses the different applications proposed in the literature and gives insights into future use of IP6 in the fields of orthodontics, periodontics, implants, and pediatric dentistry.

The IP6K Inhibitor LI-2242 Ameliorates Diet-Induced Obesity, Hyperglycemia, and Hepatic Steatosis in Mice by Improving Cell Metabolism and Insulin Signaling

Obesity and nonalcoholic fatty liver disease (NAFLD) are global health concerns, and thus, drugs for the long-term treatment of these diseases are urgently needed. We previously discovered that the inositol pyrophosphate biosynthetic enzyme IP6K1 is a target in diet-induced obesity (DIO), insulin resistance, and NAFLD. Moreover, high-throughput screening (HTS) assays and structure-activity relationship (SAR) studies identified LI-2242 as a potent IP6K inhibitor compound. Here, we tested the efficacy of LI-2242 in DIO WT C57/BL6J mice. LI-2242 (20 mg/kg/BW daily, i.p.) reduced body weight in DIO mice by specifically reducing the accumulation of body fat. It also improved glycemic parameters and reduced hyperinsulinemia. LI-2242-treated mice displayed reduced the weight of various adipose tissue depots and an increased expression of metabolism- and mitochondrial-energy-oxidation-inducing genes in these tissues. LI-2242 also ameliorated hepatic steatosis by reducing the expression of genes that enhance lipid uptake, lipid stabilization, and lipogenesis. Furthermore, LI-2242 enhances the mitochondrial oxygen consumption rate (OCR) and insulin signaling in adipocytes and hepatocytes in vitro. In conclusion, the pharmacologic inhibition of the inositol pyrophosphate pathway by LI-2242 has therapeutic potential in obesity and NAFLD.

TNP Analogues Inhibit the Virulence Promoting IP3-4 Kinase Arg1 in the Fungal Pathogen Cryptococcus neoformans

New antifungals with unique modes of action are urgently needed to treat the increasing global burden of invasive fungal infections. The fungal inositol polyphosphate kinase (IPK) pathway, comprised of IPKs that convert IP₃ to IP₈, provides a promising new target due to its impact on multiple, critical cellular functions and, unlike in mammalian cells, its lack of redundancy. Nearly all IPKs in the fungal pathway are essential for virulence, with IP_3-4 kinase (IP_3-4K) the most critical. The dibenzylaminopurine compound, N2-(m-trifluorobenzylamino)-N6-(p-nitrobenzylamino)purine (TNP), is a commercially available inhibitor of mammalian IPKs. The ability of TNP to be adapted as an inhibitor of fungal IP_3-4K has not been investigated. We purified IP_3-4K from the human pathogens, Cryptococcus neoformans and Candida albicans, and optimised enzyme and surface plasmon resonance (SPR) assays to determine the half inhibitory concentration (IC₅₀) and binding affinity (K_D), respectively, of TNP and 38 analogues. A novel chemical route was developed to efficiently prepare TNP analogues. TNP and its analogues demonstrated inhibition of recombinant IP_3-4K from C. neoformans (CnArg1) at low µM IC₅₀s, but not IP_3-4K from C. albicans (CaIpk2) and many analogues exhibited selectivity for CnArg1 over the human equivalent, HsIPMK. Our results provide a foundation for improving potency and selectivity of the TNP series for fungal IP_3-4K.

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.