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Achieving the goal of malaria elimination will depend on targeting Plasmodium pathways essential across all life stages. Here we identify a lipid kinase, phosphatidylinositol-4-OH kinase (PI(4)K), as the target of imidazopyrazines, a new antimalarial compound class that inhibits the intracellular development of multiple Plasmodium species at each stage of infection in the vertebrate host. Imidazopyrazines demonstrate potent preventive, therapeutic, and transmission-blocking activity in rodent malaria models, are active against blood-stage field isolates of the major human pathogens P. falciparum and P. vivax , and inhibit liver-stage hypnozoites in the simian parasite P. cynomolgi . We show that imidazopyrazines exert their effect through inhibitory interaction with the ATP-binding pocket of PI(4)K, altering the intracellular distribution of phosphatidylinositol-4-phosphate. Collectively, our data define PI(4)K as a key Plasmodium vulnerability, opening up new avenues of target-based discovery to identify drugs with an ideal activity profile for the prevention, treatment and elimination of malaria. The lipid kinase phosphatidylinositol-4-OH kinase (PI(4)K) is identified as a target of the imidazopyrazines, a new antimalarial compound class that can inhibit several Plasmodium species at each stage of the parasite life cycle; the imidazopyrazines exert their inhibitory action by interacting with the ATP-binding pocket of PI(4)K. A multifunction target for antimalarials To eliminate malaria completely it is necessary to cure an individual of all stages in the malaria parasite's life cycle including the symptomatic blood-stage infection and the preceding liver-stage infection (to prevent relapse) and also to block transmission to mosquitoes. Here Elizabeth Winzeler and colleagues identify phosphatidylinositol-4-OH kinase (PI(4)K) as a potential drug target that is essential to fatty acid metabolism in all stages of the Plasmodium parasite. The authors show that a family of compounds with an imidazopyrazine core, distinct from known antimalarials, inhibits PI(4)K and also inhibits the development of multiple Plasmodium species at each stage of the life cycle. Their analyses reveal that the imidazopyrazines interact with the ATP-binding pocket of PI(4)K, altering the intracellular distribution of phosphatidylinositol-4 phosphate and interfering with cell division.

KRAS is mutated in 90% of human pancreatic ductal adenocarcinomas (PDACs). To function, KRAS must localize to the plasma membrane (PM) via a C-terminal membrane anchor that specifically engages phosphatidylserine (PtdSer). This anchor-binding specificity renders KRAS–PM localization and signaling capacity critically dependent on PM PtdSer content. We now show that the PtdSer lipid transport proteins, ORP5 and ORP8, which are essential for maintaining PM PtdSer levels and hence KRAS PM localization, are required for KRAS oncogenesis. Knockdown of either protein, separately or simultaneously, abrogated growth of KRAS-mutant but not KRAS–wild-type pancreatic cancer cell xenografts. ORP5 or ORP8 knockout also abrogated tumor growth in an immune-competent orthotopic pancreatic cancer mouse model. Analysis of human datasets revealed that all components of this PtdSer transport mechanism, including the PM-localized EFR3A-PI4KIIIα complex that generates phosphatidylinositol-4-phosphate (PI4P), and endoplasmic reticulum (ER)–localized SAC1 phosphatase that hydrolyzes counter transported PI4P, are significantly up-regulated in pancreatic tumors compared to normal tissue. Taken together, these results support targeting PI4KIIIα in KRAS-mutant cancers to deplete the PM-to-ER PI4P gradient, reducing PM PtdSer content. We therefore repurposed the US Food and Drug Administration–approved hepatitis C antiviral agent, simeprevir, as a PI4KIIIα inhibitor In a PDAC setting. Simeprevir potently mislocalized KRAS from the PM, reduced the clonogenic potential of pancreatic cancer cell lines in vitro, and abrogated the growth of KRAS-dependent tumors in vivo with enhanced efficacy when combined with MAPK and PI3K inhibitors. We conclude that the cellular ER-to-PM PtdSer transport mechanism is essential for KRAS PM localization and oncogenesis and is accessible to therapeutic intervention.

High yield and wide adaptation of rice are crucial for grain supply and food security. Here, we report a type II phosphatidylinositol 4-kinase, OsPI4Kγ7, which positively regulates rice yield and confers wide adaptation of rice. We show that OsPI4Kγ7 interacts with the transcription factor, OsLIC, and promotes its stability and nuclear translocation via phosphorylation, thereby increasing yield. Meanwhile, the natural variation of OsPI4Kγ7 alters its expression level by modulating OsTb2 binding. The ospi4kγ7 mutants exhibit an earlier heading date. Intriguingly, the OsPI4Kγ7 HapG with an earlier heading date demonstrates a critical role on the initial extension towards high latitude for japonica rice, and the OsPI4Kγ7 HapA drives increased yield potential in indica rice. Our findings unravel how phosphatidylinositol 4-kinase (PI4K) regulates rice yield, and how one of its critical natural variation contributes to the different “adaptability-yield” trade-offs in japonica and indica , which provide the alternative breeding strategy for raising grain yield in different latitudes. High yield and wide adaptation rice are crucial for grain supply and food security. Here the authors report OsPI4Kγ7 which contributes to different “adaptability-yield” trade-offs in japonica and indica, and provides an alternative breeding strategy for raising grain yield in different latitudes.

Vps13 family proteins are proposed to function in bulk lipid transfer between membranes, but little is known about their regulation. During sporulation of Saccharomyces cerevisiae , Vps13 localizes to the prospore membrane (PSM) via the Spo71–Spo73 adaptor complex. We previously reported that loss of any of these proteins causes PSM extension and subsequent sporulation defects, yet their precise function remains unclear. Here, we performed a genetic screen and identified genes coding for a fragment of phosphatidylinositol (PI) 4-kinase catalytic subunit and PI 4-kinase noncatalytic subunit as multicopy suppressors of spo73 Δ. Further genetic and cytological analyses revealed that lowering PI4P levels in the PSM rescues the spo73 Δ defects. Furthermore, overexpression of VPS13 and lowering PI4P levels synergistically rescued the defect of a spo71 Δ spo73 Δ double mutant, suggesting that PI4P might regulate Vps13 function. In addition, we show that an N-terminal fragment of Vps13 has affinity for the endoplasmic reticulum (ER), and ER-plasma membrane (PM) tethers localize along the PSM in a manner dependent on Vps13 and the adaptor complex. These observations suggest that Vps13 and the adaptor complex recruit ER-PM tethers to ER-PSM contact sites. Our analysis revealed that involvement of a phosphoinositide, PI4P, in regulation of Vps13, and also suggest that distinct contact site proteins function cooperatively to promote de novo membrane formation.

Phosphoinositides are involved in regulation of recruitment and activity of signalling proteins in cell membranes. Phosphatidylinositol (PI) 4-kinases (PI4Ks) generate PI4-phosphate the precursor of regulatory phosphoinositides. No type II PI4K research on the abiotic stress response has previously been reported in plants. A stress-inducible type II PI4K gene, named TaPI4KIIγ, was obtained by de novo transcriptome sequencing of drought-treated wheat (Triticum aestivum). TaPI4KIIγ, localized on the plasma membrane, underwent threonine autophosphorylation, but had no detectable lipid kinase activity. Interaction of TaPI4KIIγ with wheat ubiquitin fusion degradation protein (TaUDF1) indicated that it might be hydrolysed by the proteinase system. Overexpression of TaPI4KIIγ revealed that it could enhance drought and salt stress tolerance during seed germination and seedling growth. A ubdkγ7 mutant, identified as an orthologue of TaPI4KIIγ in Arabidopsis, was sensitive to salt, polyethylene glycol (PEG), and abscisic acid (ABA), and overexpression of TaPI4KIIγ in the ubdkγ7 mutant compensated stress sensitivity. TaPI4KIIγ promoted root growth in Arabidopsis, suggesting that TaPI4KIIγ might enhance stress resistance by improving root growth. Overexpression of TaPI4KIIγ led to an altered expression level of stress-related genes and changes in several physiological traits that made the plants more tolerant to stress. The results provided evidence that overexpression of TaPI4KIIγ could improve drought and salt tolerance.

Calcineurin, the conserved protein phosphatase and target of immunosuppressants, is a critical mediator of Ca 2+ signaling. Here, to discover calcineurin-regulated processes we examined an understudied isoform, CNAβ1. We show that unlike canonical cytosolic calcineurin, CNAβ1 localizes to the plasma membrane and Golgi due to palmitoylation of its divergent C-terminal tail, which is reversed by the ABHD17A depalmitoylase. Palmitoylation targets CNAβ1 to a distinct set of membrane-associated interactors including the phosphatidylinositol 4-kinase (PI4KA) complex containing EFR3B, PI4KA, TTC7B and FAM126A. Hydrogen-deuterium exchange reveals multiple calcineurin-PI4KA complex contacts, including a calcineurin-binding peptide motif in the disordered tail of FAM126A, which we establish as a calcineurin substrate. Calcineurin inhibitors decrease PI4P production during Gq-coupled GPCR signaling, suggesting that calcineurin dephosphorylates and promotes PI4KA complex activity. In sum, this work discovers a calcineurin-regulated signaling pathway which highlights the PI4KA complex as a regulatory target and reveals that dynamic palmitoylation confers unique localization, substrate specificity and regulation to CNAβ1. Calcineurin — the Ca2+ regulated phosphatase and target of immunosuppressants — regulates GPCR-mediated phospholipid signaling at the plasma membrane. Here the authors show that CNAβ1 (a poorly studied isoform of the calcineurin catalytic subunit) is targeted to the plasma membrane through palmitoylation to dephosphorylate and promote PI4KA complex activity.

4-anilino quinazolines have been identified as inhibitors of HCV replication. The target of this class of compounds was proposed to be the viral protein NS5A, although unequivocal proof has never been presented. A 4-anilino quinazoline moiety is often found in kinase inhibitors, leading us to formulate the hypothesis that the anti-HCV activity displayed by these compounds might be due to inhibition of a cellular kinase. Type III phosphatidylinositol 4-kinase α (PI4KIIIα) has recently been identified as a host factor for HCV replication. We therefore evaluated AL-9, a compound prototypical of the 4-anilino quinazoline class, on selected phosphatidylinositol kinases. AL-9 inhibited purified PI4KIIIα and, to a lesser extent, PI4KIIIβ. In Huh7.5 cells, PI4KIIIα is responsible for the phosphatidylinositol-4 phosphate (PI4P) pool present in the plasma membrane. Accordingly, we observed a gradual decrease of PI4P in the plasma membrane upon incubation with AL-9, indicating that this agent inhibits PI4KIIIα also in living cells. Conversely, AL-9 did not affect the level of PI4P in the Golgi membrane, suggesting that the PI4KIIIβ isoform was not significantly inhibited under our experimental conditions. Incubation of cells expressing HCV proteins with AL-9 induced abnormally large clusters of NS5A, a phenomenon previously observed upon silencing PI4KIIIα by RNA interference. In light of our findings, we propose that the antiviral effect of 4-anilino quinazoline compounds is mediated by the inhibition of PI4KIIIα and the consequent depletion of PI4P required for the HCV membranous web. In addition, we noted that HCV has a profound effect on cellular PI4P distribution, causing significant enrichment of PI4P in the HCV-membranous web and a concomitant depletion of PI4P in the plasma membrane. This observation implies that HCV--by recruiting PI4KIIIα in the RNA replication complex--hijacks PI4P metabolism, ultimately resulting in a markedly altered subcellular distribution of the PI4KIIIα product.

Generation of the lipid messenger phosphatidylinositol-3,4,5-trisphosphate (PtdIns(3,4,5)P 3 ) is crucial for development, cell growth and survival, and motility, and it becomes dysfunctional in many diseases including cancers. Here we reveal a mechanism for PtdIns(3,4,5)P 3 generation by scaffolded phosphoinositide kinases. In this pathway, class I phosphatidylinositol-3-OH kinase (PI(3)K) is assembled by IQGAP1 with PI(4)KIIIα and PIPKIα, which sequentially generate PtdIns(3,4,5)P 3 from phosphatidylinositol. By scaffolding these kinases into functional proximity, the PtdIns(4,5)P 2 generated is selectively used by PI(3)K for PtdIns(3,4,5)P 3 generation, which then signals to PDK1 and Akt that are also in the complex. Moreover, multiple receptor types stimulate the assembly of this IQGAP1–PI(3)K signalling complex. Blockade of IQGAP1 interaction with PIPKIα or PI(3)K inhibited PtdIns(3,4,5)P 3 generation and signalling, and selectively diminished cancer cell survival, revealing a target for cancer chemotherapy. Anderson et al.  show that IQ-motif-containing GTPase-activating protein 1 (IQGAP1) acts as a scaffold for the phosphoinositide kinases that mediate the sequential phosphorylation of phosphoinositides to generate PtdIns(3,4,5)P 3 and downstream signalling.

Infection by positive-strand RNA viruses necessitates membrane expansion and elevated phospholipid biosynthesis, whereby fatty acids stored as triacylglycerols in lipid droplets (LDs) are mobilized to promote metabolic processes and membrane biogenesis. The replication organelles (ROs) of coronavirus associate with modified host endomembrane; however, the molecular mechanisms underlying the expansion and modification of these membranes remain poorly understood. Here, we show that viral protein orf3a collaborates with nsp3, nsp4, nsp6 to facilitate the formation of ROs in SARS-CoV-2. Importantly, orf3a targets LDs to ROs, establishing novel membrane contact sites and induces host cell microlipophagy, which supplies essential lipids for RO biogenesis. Subsequently, Following the formation of ROs, nsp3, with assistance from nsp12, indirectly recruits phosphatidylinositol 4-kinase beta (PI4KB) to ROs, to produce phosphatidylinositol 4-phosphate (PI4P). This action creates a PI4P-enriched microenvironment that enhances SARS-CoV-2 replication. Our findings elucidate the mechanism governing RO generation during SARS-CoV-2 infection and suggest that targeting microlipophagy pharmacologically may represent a promising strategy for the development of anti-coronaviruses therapies.

A mechanism for phosphoinositide conversion at endosomes to enable exit from the endosomal system, suggesting that defective phosphoinositide conversion at endosomes underlies X-linked centronuclear myopathy. Phosphoinositide conversion during endosome exit Directional membrane traffic requires regulated conversion of phosphoinositides (PIs) — membrane phospholipids that act as determinants of membrane identity — by PI metabolizing enzymes. Volker Haucke and co-workers studied the mechanism of PI identity shifts during trafficking from the endosomal system — defined by phosphatidylinositol 3-phosphate (PI(3)P) — to the secretory compartments and the plasma membrane, dominated by phosphatidylinositol 4-phosphate (PI(4)P) and phosphatidylinositol 4,5-bisphosphate (PI(4,5)P 2 ). The authors find that endosomal cargo en route to intracellular destinations can change direction and make its way back to the cell surface by the action of two enzymes. Specifically, PI(3)P on the membrane of these compartments is hydrolysed by the phosphatase MTM1, an enzyme whose loss of function leads to X-linked centronuclear myopathy in humans. This hydrolysis of PI(3)P is accompanied by the generation of PI(4)P through the action of phosphatidylinositol 4-kinase, as well as the recruitment of the exocyst tethering complex to enable subsequent membrane fusion. Phosphoinositides are a minor class of short-lived membrane phospholipids that serve crucial functions in cell physiology ranging from cell signalling and motility to their role as signposts of compartmental membrane identity 1 , 2 . Phosphoinositide 4-phosphates such as phosphatidylinositol 4-phosphate (PI(4)P) and phosphatidylinositol 4,5-bisphosphate (PI(4,5)P 2 ) are concentrated at the plasma membrane, on secretory organelles 3 , and on lysosomes 4 , whereas phosphoinositide 3-phosphates, most notably phosphatidylinositol 3-phosphate (PI(3)P) 5 , are a hallmark of the endosomal system 1 , 2 . Directional membrane traffic between endosomal and secretory compartments, although inherently complex, therefore requires regulated phosphoinositide conversion. The molecular mechanism underlying this conversion of phosphoinositide identity during cargo exit from endosomes by exocytosis is unknown. Here we report that surface delivery of endosomal cargo requires hydrolysis of PI(3)P by the phosphatidylinositol 3-phosphatase MTM1, an enzyme whose loss of function leads to X-linked centronuclear myopathy (also called myotubular myopathy) in humans 6 . Removal of endosomal PI(3)P by MTM1 is accompanied by phosphatidylinositol 4-kinase-2α (PI4K2α)-dependent generation of PI(4)P and recruitment of the exocyst tethering complex to enable membrane fusion. Our data establish a mechanism for phosphoinositide conversion from PI(3)P to PI(4)P at endosomes en route to the plasma membrane and suggest that defective phosphoinositide conversion at endosomes underlies X-linked centronuclear myopathy caused by mutation of MTM1 in humans.