Identification of the Host Substratome of Leishmania-Secreted Casein Kinase 1 Using a SILAC-Based Quantitative Mass Spectrometry Assay

Leishmaniasis is a severe public health problem, caused by the protozoan Leishmania. This parasite has two developmental forms, extracellular promastigote in the insect vector and intracellular amastigote in the mammalian host where it resides inside the phagolysosome of macrophages. Little is known about the virulence factors that regulate host-pathogen interactions and particularly host signalling subversion. All the proteomes of Leishmania extracellular vesicles identified the presence of Leishmania casein kinase 1 (L-CK1.2), a signalling kinase. L-CK1.2 is essential for parasite survival and thus might be essential for host subversion. To get insights into the functions of L-CK1.2 in the macrophage, the systematic identification of its host substrates is crucial, we thus developed an easy method to identify substrates, combining phosphatase treatment, in vitro kinase assay and Stable Isotope Labelling with Amino acids in Cell (SILAC) culture-based mass spectrometry. Implementing this approach, we identified 225 host substrates as well as a potential novel phosphorylation motif for CK1. We confirmed experimentally the enrichment of our substratome in bona fide L-CK1.2 substrates and showed they were also phosphorylated by human CK1δ. L-CK1.2 substratome is enriched in biological processes such as “viral and symbiotic interaction,” “actin cytoskeleton organisation” and “apoptosis,” which are consistent with the host pathways modified by Leishmania upon infection, suggesting that L-CK1.2 might be the missing link. Overall, our results generate important mechanistic insights into the signalling of host subversion by these parasites and other microbial pathogens adapted for intracellular survival.

Nuplazid suppresses esophageal squamous cell carcinoma growth in vitro and in vivo by targeting PAK4

Background Due to the high recurrence and low 5-year survival rates of esophageal squamous cell carcinoma (ESCC) after treatment, the discovery of novel drugs for recurrence chemoprevention is of particular importance. Methods We screened the FDA-approved drug library and found that Nuplazid, an atypical antipsychotic that acts as an effective 5-HT 2 A receptor inverse agonist, could potentially exert anticancer effects in vitro and in vivo on ESCC. Results Pull-down results indicated that Nuplazid binds with p21-activated kinase 4 (PAK4), and a kinase assay showed that Nuplazid strongly suppressed PAK4 kinase activity. Moreover, Nuplazid exhibited inhibitory effects on ESCC in vivo. Conclusions Our findings indicate that Nuplazid can suppress ESCC progression through targeting PAK4.

Quinacrine binds to the kinase domain of FGFR1 and inhibits its activity

BackgroundFGF family receptors, especially FGFR1, have been widely implicated for their potential role in the promotion of oncogenesis and chemoresistance in lung cancer. Quinacrine, an anti-malarial drug, has been widely reported to exhibit anti-neoplastic properties through the activation of p53 and simultaneous inhibition of NF-kB signaling pathways in cancer cells.MethodsThe binding of QC to FGFR1 was studied using molecular docking and molecular dynamics simulation studies. The experimental kinase activity assay for the protein was performed using a luminescence-based kinase assay. FGF-induced phosphorylation and proliferation were studied by cell counting and western blotting. Matrigel-based cell migration was conducted to assess migration activity.ResultsQC interacted with multiple residues around the kinase insert domain of FGFR1 through hydrogen bonding, hydrophobic interactions, and water bridges. The kinase activity inhibition assay demonstrated a significant reduction in FGFR1 kinase activity by QC at higher concentrations, which was further observed at the cellular level in inhibition of FGFR1 phosphorylation and proliferation by QC at higher exposure concentrations of FGF stimulated cells. These effects were further validated downstream in the FGF-induced activation of cell migration.ConclusionQC did form a stable interaction with residues of FGFR1 at another allosteric site surrounding the kinase domain, leading to inhibition of its kinase activity at higher drug concentrations. This effect was further observed at the cellular level in both acidic and basic FGF ligand-induced proliferation, phosphorylation of FGFR1, and cell migration, where a trend of significant reduction in activity was observed at higher drug concentrations.

CBIO-11. HISTONE H3.3 G34R/V MUTATIONS STIMULATE PEDIATRIC HIGH-GRADE GLIOMA FORMATION THROUGH THE INDUCTION OF CHROMOSOMAL INSTABILITY

H3.3 G34R/V mutations are drivers of high-grade pediatric glioma (pHGG). H3.3 G34R/V mutations are linked to altered H3.3 K36 trimethylation (H3K36me3); implicating epigenetic gene regulation as a possible contributor to pHGG formation. Here we show that H3.3 G34R/V also induces chromosomal instability (CIN); a hallmark of pHGG. If CIN promotes pHGG formation is unknown. We observed that H3.3 G34 mutant pHGG cells have reduced mitotic H3.3 S31 phosphorylation compare to WT H3.3 cell lines. And, H3.3 G34R reduced Chk1 phosphorylation at S31 by >90% in an in vitro kinase assay. Chk1 regulates chromosome segregation through phosphorylation of pericentromeric H3.3 S31 during early mitosis. Overexpression of H3.3 G34R or non-phosphorylatable S31A in H3.3 WT, diploid cells caused a significant increase in CIN. Likewise, H3.3 G34 mutant pHGG cells have significantly elevated rates of CIN as compare to H3.3 WT pHGG cells. During normal cell division, phospho-S31 is lost in anaphase. However, following chromosome missegregation, phospho-S31 spreads and stimulates p53-induced cell cycle arrest. Here we show that WT p53 cells expressing mutant G34 fail to arrest following chromosome mis-segregation. These studies demonstrate that H3.3 G34R/V mutations are sufficient to transform normal, diploid cells into proliferating CIN cells. To determine if this process contributes to tumorigenesis, we used RCAS Nestin-TVA mice to overexpress H3.3 WT, G34R, or S31A – P2A-linked to PDGFB expression in glial precursor cells of newborn mice. Over 100 days, S31A and G34R mice had drastically reduced survival (averaging 77, 81, and 100 days for S31A, G34R, and WT). Furthermore, most G34R and S31A mice developed HGG, while H3.3 WT mice remained tumor-free. Our work implicates CIN as a driver of H3.3 G34 mutant pHGG formation. Our ongoing studies utilize K36M and double mutants to further define the contributions of S31 phosphorylation (CIN) and H3K36me3 (epigenetic gene regulation) to tumorigenesis.

HIV-1 Vif protein is stabilized by AKT-mediated phosphorylation to enhance APOBEC3G degradation

HIV-1 virus has to counter anti-viral restriction factors for its successful replication after its entry in the cell. The host-pathogen dynamics operate as soon as HIV-1 interacts with the cell. HIV-1 Vif has been known for its role in degradation of APOBEC3G; a cytosine deaminase which leads to hyper mutations in the viral DNA leading to aberrant viral replication. The cellular proteins regulating the intracellular HIV-1 Vif protein levels can have profound impact on HIV-1 pathogenesis. MDM2 is known to induce degradation of Vif with subsequent effects on APOBEC3G. Here, we have identified AKT/PKB as one of the crucial regulators of HIV-1 Vif protein. The rationale for selecting Vif as a target substrate for AKT was the presence of RMRINT motif in it, which is similar to the AKT phosphorylation motif RxRxxS/T. Immunoprecipitation assay and Kinase assay revealed that AKT and Vif interact strongly with each other and Vif is phosphorylated at T20 position by AKT. This phosphorylation stabilizes HIV-1 Vif while Vif mutant T20A degrades faster. Moreover, use of dominant negative form of AKT (KD-AKT) and AKT inhibitors were found to destabilise Vif and increase its K48-ubiquitination profile. The consequences of this AKT-Vif interplay were also validated on APOBEC3G degradation, a target of Vif. AKT inhibition was found to restore APOBEC3G levels. This process can be interpreted as a strategy used by virus to prevent MDM2 mediated Vif degradation; AKT stabilises Mdm2, which then targets Vif for degradation but at the same time AKT stabilises Vif by phosphorylating it. Thus, AKT mediated stabilization of Vif might compensate for its degradation by MDM2. This study can have significant implications as HIV-1 Tat protein and growth factors like insulin activate PI3-K/AKT Kinase pathway and can potentially affect Vif and APOBEC3G protein levels and hence HIV-1 pathogenesis.

Physical and functional interactome atlas of human receptor tyrosine kinases

Much cell-to-cell communication is facilitated by cell surface receptor tyrosine kinases (RTKs). These proteins phosphorylate their downstream cytoplasmic substrates in response to stimuli such as growth factors. Despite their central roles, the functions of many RTKs are still poorly understood. To resolve the lack of systematic knowledge, we used three complementary methods to map the molecular context and substrate profiles of RTKs. We used affinity purification coupled to mass spectrometry (AP-MS) to characterize stable binding partners and RTK-protein complexes, proximity-dependent biotin identification (BioID) to identify transient and proximal interactions, and an in vitro kinase assay to identify RTK substrates. To identify how kinase interactions depend on kinase activity, we also used kinase-deficient mutants. Our data represent a comprehensive, systemic mapping of RTK interactions and substrates. This resource adds information regarding well-studied RTKs, offers insights into the functions of less well-studied RTKs, and highlights RTK-RTK interactions and shared signaling pathways.

Chinese Prescription Kangen-karyu as Potential Anti-Alzheimer’s Disease Therapeutic: Analyses of BACE1 and GSK-3b Inhibitory Activities

Inhibition of β-site amyloid precursor protein-cleaving enzyme 1 (BACE1) or glycogen synthase kinase-3β (GSK-3β) is estimated to be the central therapeutic approach for Alzheimer’s disease (AD). In this study, water extract of Kangenkaryu, its crude drug and chemical composition used in oriental medicine were evaluated regarding their BACE1 and GSK-3β inhibitory activities.Fluorescence resonance energy transfer was used to characterize the BACE1 inhibitory effect of Kangen-karyu, its crude drug and chemical composition.GSK-3β activity was determined using the Kinase-Glo Luminescent Kinase Assay Platform. The water extract of Kangen-karyu inhibited BACE1 and GSK-3β in concentration-dependent manners when compared with reference drugs, quercetin and luteolin. Among six components of Kangen-karyu, the water extracts of Salviae Miltiorrhizae Radix or Cyperi Rhizoma exhibited significant inhibitory effects on BACE1 and GSK-3β. Among the constituents of Salviae Miltiorrhizae Radix extract, salvianolic acid C, salvianolic acid A, rosmarinic acid, and magnesium lithospermate B significantly inhibited BACE1. In addition, they inhibited GSK-3β with an IC50 value range of 6.97 to 135.35 μM. From these results, one of the effectiveness and its mechanisms of action of Kangen-karyu against AD may be the inhibition of BACE1 and GSK-3β, and one of the active ingredients of Kangen-karyu is Salviae Miltiorrhizae Radix and its constituents.

Cyclin G2 reverses immunosuppressive tumor microenvironment and potentiates PD-1 blockade in glioma

Background Expression of aberrant cyclin G2 is a key factor contributing to cancer biological processes, including glioma. However, the potential underlying mechanisms of cyclin G2 in the glioma tumor immune microenvironment remain unclear. Methods Co-immunoprecipitation (co-IP), in situ proximity ligation assay (PLA), and in vitro kinase assay were conducted to reveal the underlying mechanism by which cyclin G2 regulates Y10 phosphorylation of LDHA. Further, the biological roles of cyclin G2 in cell proliferation, migration, invasion capacity, apoptosis, glycolysis, and immunomodulation were assessed through in vitro and in vivo functional experiments. Expressions of cyclin G2 and Foxp3 in glioma specimens was determined by immunohistochemistry. Results In this study, we found that cyclin G2 impeded the interaction between LDHA and FGFR1, thereby decreasing Y10 phosphorylation of LDHA through FGFR1 catalysis. Cyclin G2 inhibited proliferation, migration, invasion capacity, and glycolysis and promoted apoptosis glioma cells via suppressing Y10 phosphorylation of LDHA. Moreover, we further verified that cyclin G2 reversed the immunosuppressive to antitumor immune microenvironment through inhibiting lactate production by glioma cells. Besides, cyclin G2 potentiated PD-1 blockade and exerted strong antitumor immunity in the glioma-bearing mice model. Conclusions Cyclin G2 acts as a potent tumor suppressor in glioma and enhances responses to immunotherapy. Our findings may be helpful in selecting glioma patients for immunotherapy trials in the future.

Identification of novel indazole-based inhibitors of fibroblast growth factor receptor 1 (FGFR1)

Background: Overactivity of fibroblast growth factor receptor 1 (FGFR1) is associated with various tumors, particularly breast cancer, prostate cancer, non-small-cell lung carcinoma, myeloproliferative diseases, which makes this protein kinase a promising therapeutic target for anticancer therapy. Objective: The main aim of this study is to identify novel FGFR1 inhibitors. Method: In order to find FGFR1 inhibitors, virtual screening experiments were performed using AutoDock software. Best-scored compounds were tested in vitro using P32 radioactive kinase assay. Results: Small-molecular inhibitors of protein kinase FGFR1 were identified among indazole derivatives. The most active compound [3-(3,4-dichloro-phenyl)-1H-indazol-5-yl]-(2,3-dihydro-1H-cyclopenta[b]quinolin-9-yl)-amine (1) inhibits FGFR1 with IC50 value of 100 nM. According to molecular docking results, this compound interacts simultaneously with adenine- and phosphate-binding regions of protein kinase FGFR1. The structure-activity relationships have been investigated and binding mode has been predicted. Conclusion: The compound 1 can be used for further structural optimization and biological research.