Novel quinazolin-4(3H)-one based Cyclin K degraders regulate alternative polyadenylation activity.

Phenotypic screening is gaining attention as a powerful method for identifying compounds that regulate cellular phenotypes of interest through novel mechanisms of action. Recently, a new modality of compounds, called molecular glues, which can induce the degradation of target proteins by forming ternary complexes of E3 ligases, has emerged from phenotypic screening. In this study, using global proteomic analysis, we identified a novel Cyclin K degrader, T4, which was previously discovered through phenotypic screening for alternative polyadenylation regulation. Our detailed mechanistic analysis revealed that T4 induced Cyclin K degradation, leading to the regulation of alternative polyadenylation. Additionally, we generated a more potent Cyclin K degrader, TR-213, through a structure-activity relationship study of T4. T4 and TR-213 are structurally distinct from other Cyclin K degraders and can be used as novel chemical tools to further analyze the degradation of Cyclin K and the regulation of alternative polyadenylation.

DNA damage stress-induced translocation of mutant FUS proteins into cytosolic granules and screening for translocation inhibitors.

Fused in sarcoma/translated in liposarcoma (FUS) is an RNA-binding protein, and its mutations are associated with neurodegenerative diseases, including amyotrophic lateral sclerosis (ALS), through the DNA damage stress response, aberrant stress granule (SG) formation, etc. We previously reported that translocation of endogenous FUS into SGs was achieved by cotreatment with a DNA double-strand break inducer and an inhibitor of DNA-PK activity. In the present study, we investigated cytoplasmic SG formation using various fluorescent protein-tagged mutant FUS proteins in a human astrocytoma cell (U251) model. While the synergistic enhancement of the migration of fluorescent protein-tagged wild-type FUS to cytoplasmic SGs upon DNA damage induction was observed when DNA-PK activity was suppressed, the fluorescent protein-tagged FUSP525L mutant showed cytoplasmic localization. It migrated to cytoplasmic SGs upon DNA damage induction alone, and DNA-PK inhibition also showed a synergistic effect. Furthermore, analysis of 12 sites of DNA-PK-regulated phosphorylation in the N-terminal LC region of FUS revealed that hyperphosphorylation of FUS mitigated the mislocalization of FUS into cytoplasmic SGs. By using this cell model, we performed screening of a compound library to identify compounds that inhibit the migration of FUS to cytoplasmic SGs but do not affect the localization of the SG marker molecule G3BP1 to cytoplasmic SGs. Finally, we successfully identified 23 compounds that inhibit FUS-containing SG formation without changing normal SG formation. Highlights Characterization of DNA-PK-dependent FUS stress granule localization.A compound library was screened to identify compounds that inhibit the formation of FUS-containing stress granules.

Involvement of ferroptosis in human motor neuron cell death.

Ferroptosis was recently defined as a novel type of programmed cell death depending on iron and lipid peroxidation. It is biologically different from other types of cell death such as apoptosis. While the involvement of ferroptosis in cancer, patient and animal model have been intensely studied, ferroptosis in human motor neuron model is still clearly unknown. Here we carefully assessed ferroptosis using human iPS cell-derived motor neuron (hiMNs). We found that almost all hiMNs died by the treatment of glutathione peroxidase 4 (GPX4) inhibitors. Importantly, the cell death was rescued by one antioxidant, vitamin E acetate, iron chelators and lipid peroxidase inhibitors with high dynamic ranges. Finally, these data clearly indicated that ferroptosis constitutively occurs in hiMNs, suggesting the possibility that it might play a biologically and pathologically important roles in motor neuron death such as motor neuron disease (MND)/Amyotrophic lateral sclerosis (ALS).

Identification of hub molecules of FUS-ALS by Bayesian gene regulatory network analysis of iPSC model: iBRN.

Fused in sarcoma/translated in liposarcoma (FUS) is a causative gene of amyotrophic lateral sclerosis (ALS). Mutated FUS causes accumulation of DNA damage and cytosolic stress granule (SG) formation, thereby motor neuron (MN) death. However, key molecular aetiology remains unclear. Here, we applied a novel platform technology, iBRN, "Non- biased" Bayesian gene regulatory network analysis based on induced pluripotent stem cell (iPSC)-derived cell model, to elucidate the molecular aetiology using transcriptome of iPSC-derived MNs harboring FUSH517D. iBRN revealed "hub molecules", which strongly influenced transcriptome network, such as miR-125b-5p-TIMELESS axis and PRKDC for the molecular aetiology. Next, we confirmed miR-125b-5p-TIMELESS axis in FUSH517D MNs such that miR-125b-5p regulated several DNA repair-related genes including TIMELESS. In addition, we validated both introduction of miR-125b-5p and knocking down of TIMELESS caused DNA damage in the cell culture model. Furthermore, PRKDC was strongly associated with FUS mis-localization into SGs by DNA damage under impaired DNA-PK activity. Collectively, our iBRN strategy provides the first compelling evidence to elucidate molecular aetiology in neurodegenerative diseases.

A novel dextrin produced by the enzymatic reaction of 6-α-glucosyltransferase. I. The effect of nonreducing ends of glucose with by α-1,6 bonds on the retrogradation inhibition of high molecular weight dextrin.

We prepared a high-molecular-weight modified dextrin (MWS-1000) from a partial hydrolysate of waxy corn starch with a weight average molecular weight of 1 × 106 (WS-1000) using Paenibacillus alginolyticus PP710 α-glucosyltransferase. The gel permeation chromatography showed that the weight average molecular weight of MWS-1000 was almost the same as that of WS-1000. The side chain lengths of WS-1000 and MWS-1000 after isomaltodextranase digestion were also shown to be similar to each other by high-performance anion exchange chromatography with pulsed amperometric detection. Since MWS-1000 confirmed the presence of α-1,6 bonds by enzyme digestibility, methylation, and 1H-NMR analyses, it was presumed that the structure of MWS-1000 was based on the introduction of α-1,6 glucosyl residues at the nonreducing ends of the partial hydrolysate of waxy corn starch. Furthermore, the MWS-1000 solution was not retrograded even during refrigerated storage or after repeated freeze-thaw cycles.

Quantitative comparison of the mRNA content of human iPSC-derived motor neurons and their extracellular vesicles.

Extracellular vesicles (EVs) contain various cargo molecules, including RNAs and proteins. EVs, which include exosomes, are predicted to be suitable surrogates of their source cells for liquid biopsy to measure biomarkers. Several studies have performed qualitative comparisons of cargo molecule repertoires between source cells and their EVs. However, quantitative comparisons have not been reported so far. Furthermore, many studies analyzed microRNAs or proteins in EVs, but not mRNAs. In this study, we analyzed mRNAs in motor neurons and their EVs. Normal human-induced pluripotent stem cells were differentiated into motor neurons, and comprehensive analysis of mRNAs in the cells and their EVs was performed by RNA sequencing. Differential analysis between cellular and EV mRNAs was performed by edgeR after normalization of read count. The results suggest that signatures in the abundance of EV mRNAs were different from those of cellular mRNAs. Comparison of intracellular vesicle and EV mRNA abundance showed negatively and positively biased genes in the EVs. Gene Ontology analysis revealed that the genes showing negatively biased abundance in the EVs were enriched in many functions regarding neuronal development. In contrast, the positively biased genes were enriched in functions regarding cellular metabolism and protein synthesis. These results suggest that mRNAs in motor neurons are loaded into EVs to regulate certain mechanisms, which are yet to be elucidated.

Synthetic mRNA-based differentiation method enables early detection of Parkinson's phenotypes in neurons derived from Gaucher disease-induced pluripotent stem cells.

Gaucher disease, the most prevalent metabolic storage disorder, is caused by mutations in the glucocerebrosidase gene GBA1, which lead to the accumulation of glucosylceramide (GlcCer) in affected cells. Gaucher disease type 1 (GD1), although defined as a nonneuronopathic subtype, is accompanied by an increased risk of Parkinson's disease. To gain insights into the association of progressive accumulation of GlcCer and the Parkinson's disease phenotypes, we generated dopaminergic (DA) neurons from induced pluripotent stem cells (iPSCs) derived from a GD1 patient and a healthy donor control, and measured GlcCer accumulation by liquid chromatography-mass spectrometry. We tested two DA neuron differentiation methods: a well-established method that mimics a step-wise developmental process from iPSCs to neural progenitor cells, and to DA neurons; and a synthetic mRNA-based method that overexpresses a transcription factor in iPSCs. GD1-specific accumulation of GlcCer was detected after 60 days of differentiation by the former method, whereas it was detected after only 10 days by the latter method. With this synthetic mRNA-based rapid differentiation method, we found that the metabolic defect in GD1 patient cells can be rescued by the overexpression of wild-type GBA1 or the treatment with an inhibitor for GlcCer synthesis. Furthermore, we detected the increased phosphorylation of α-synuclein, a biomarker for Parkinson's disease, in DA neurons derived from a GD1 patient, which was significantly decreased by the overexpression of wild-type GBA1. These results suggest that synthetic mRNA-based method accelerates the analyses of the pathological mechanisms of Parkinson's disease in GD1 patients and possibly facilitates drug discovery processes.

Viscous flow and collapse of macroscopic cavities in a granular material in terms of a Darcylet.

Viscous flow through a granular material that has a macroscopic cavity is obtained on the basis of the Stokes and the generalized Darcy's equation. A new singularity termed 'Darcylet', a fundamental flow in the granular material that acts like a point force with negative direction, is proposed, which is applied to elucidate the interaction of two cavities. Depending on the configuration of the latter, the volume flux into the cavity increases, which enhances the local stresses on the boundary, causes the collapse of cavities and triggers landslides. This article is part of the theme issue 'Stokes at 200 (Part 1)'.

A BET family protein degrader provokes senolysis by targeting NHEJ and autophagy in senescent cells.

Although cellular senescence acts primarily as a tumour suppression mechanism, the accumulation of senescent cells in vivo eventually exerts deleterious side effects through inflammatory/tumour-promoting factor secretion. Thus, the development of new drugs that cause the specific elimination of senescent cells, termed senolysis, is anticipated. Here, by an unbiased high-throughput screening of chemical compounds and a bio-functional analysis, we identify BET family protein degrader (BETd) as a promising senolytic drug. BETd provokes senolysis through two independent but integrated pathways; the attenuation of non-homologous end joining (NHEJ), and the up-regulation of autophagic gene expression. BETd treatment eliminates senescent hepatic stellate cells in obese mouse livers, accompanied by the reduction of liver cancer development. Furthermore, the elimination of chemotherapy-induced senescent cells by BETd increases the efficacy of chemotherapy against xenograft tumours in immunocompromised mice. These results reveal the vulnerability of senescent cells and open up possibilities for its control.

A Cell-Based High-Throughput Screening Identified Two Compounds that Enhance PINK1-Parkin Signaling.

Early-onset Parkinson's disease-associated PINK1-Parkin signaling maintains mitochondrial health. Therapeutic approaches for enhancing PINK1-Parkin signaling present a potential strategy for treating various diseases caused by mitochondrial dysfunction. We report two chemical enhancers of PINK1-Parkin signaling, identified using a robust cell-based high-throughput screening system. These small molecules, T0466 and T0467, activate Parkin mitochondrial translocation in dopaminergic neurons and myoblasts at low doses that do not induce mitochondrial accumulation of PINK1. Moreover, both compounds reduce unfolded mitochondrial protein levels, presumably through enhanced PINK1-Parkin signaling. These molecules also mitigate the locomotion defect, reduced ATP production, and disturbed mitochondrial Ca2+ response in the muscles along with the mitochondrial aggregation in dopaminergic neurons through reduced PINK1 activity in Drosophila. Our results suggested that T0466 and T0467 may hold promise as therapeutic reagents in Parkinson's disease and related disorders.

Decoding Transcriptome Dynamics of Genome-Encoded Polyadenylation and Autoregulation with Small-Molecule Modulators of Alternative Polyadenylation.

Alternative polyadenylation (APA) plays a critical role in regulating gene expression. However, the balance between genome-encoded APA processing and autoregulation by APA modulating RNA binding protein (RBP) factors is not well understood. We discovered two potent small-molecule modulators of APA (T4 and T5) that promote distal-to-proximal (DtoP) APA usage in multiple transcripts. Monotonically responsive APA events, induced by short exposure to T4 or T5, were defined in the transcriptome, allowing clear isolation of the genomic sequence features and RBP motifs associated with DtoP regulation. We found that longer vulnerable introns, enriched with distinctive A-rich motifs, were preferentially affected by DtoP APA, thus defining a core set of genes with genomically encoded DtoP regulation. Through APA response pattern and compound-small interfering RNA epistasis analysis of APA-associated RBP factors, we further demonstrated that DtoP APA usage is partly modulated by altered autoregulation of polyadenylate binding nuclear protein-1 signaling.

Discovery of novel serine palmitoyltransferase inhibitors as cancer therapeutic agents.

We pursued serine palmitoyltransferase (SPT) inhibitors as novel cancer therapeutic agents based on a correlation between SPT inhibition and growth suppression of cancer cells. High-throughput screening and medicinal chemistry efforts led to the identification of structurally diverse SPT inhibitors 4 and 5. Both compounds potently inhibited SPT enzyme and decreased intracellular ceramide content. In addition, they suppressed cell growth of human lung adenocarcinoma HCC4006 and acute promyelocytic leukemia PL-21, and displayed good pharmacokinetic profiles. Reduction of 3-ketodihydrosphingosine, the direct downstream product of SPT, was confirmed under in vivo settings after oral administration of compounds 4 and 5. Their anti-tumor efficacy was observed in a PL-21 xenograft mouse model. These results suggested that SPT inhibitors might have potential to be effective cancer therapeutics.

Derivatization of inhibitor of apoptosis protein (IAP) ligands yields improved inducers of estrogen receptor α degradation.

Aberrant expression of proteins often underlies many diseases, including cancer. A recently developed approach in drug development is small molecule-mediated, selective degradation of dysregulated proteins. We have devised a protein-knockdown system that utilizes chimeric molecules termed specific and nongenetic IAP-dependent protein erasers (SNIPERs) to induce ubiquitylation and proteasomal degradation of various target proteins. SNIPER(ER)-87 consists of an inhibitor of apoptosis protein (IAP) ligand LCL161 derivative that is conjugated to the estrogen receptor α (ERα) ligand 4-hydroxytamoxifen by a PEG linker, and we have previously reported that this SNIPER efficiently degrades the ERα protein. Here, we report that derivatization of the IAP ligand module yields SNIPER(ER)s with superior protein-knockdown activity. These improved SNIPER(ER)s exhibited higher binding affinities to IAPs and induced more potent degradation of ERα than does SNIPER(ER)-87. Further, they induced simultaneous degradation of cellular inhibitor of apoptosis protein 1 (cIAP1) and delayed degradation of X-linked IAP (XIAP). Notably, these reengineered SNIPER(ER)s efficiently induced apoptosis in MCF-7 human breast cancer cells that require IAPs for continued cellular survival. We found that one of these molecules, SNIPER(ER)-110, inhibits the growth of MCF-7 tumor xenografts in mice more potently than the previously characterized SNIPER(ER)-87. Mechanistic analysis revealed that our novel SNIPER(ER)s preferentially recruit XIAP, rather than cIAP1, to degrade ERα. Our results suggest that derivatized IAP ligands could facilitate further development of SNIPERs with potent protein-knockdown and cytocidal activities against cancer cells requiring IAPs for survival.

Discovery of an Irreversible and Cell-Active BCL6 Inhibitor Selectively Targeting Cys53 Located at the Protein-Protein Interaction Interface.

B-cell lymphoma 6 (BCL6) is the most frequently involved oncogene in diffuse large B-cell lymphomas (DLBCLs). BCL6 shows potent transcriptional repressor activity through interactions with its corepressors, such as BCL6 corepressor (BCOR). The inhibition of the protein-protein interaction (PPI) between BCL6 and its corepressors suppresses the growth of BCL6-dependent DLBCLs, thus making BCL6 an attractive drug target for lymphoma treatment. However, potent small-molecule PPI inhibitor identification remains challenging because of the lack of deep cavities at PPI interfaces. This article reports the discovery of a potent, cell-active small-molecule BCL6 inhibitor, BCL6-i (8), that operates through irreversible inhibition. First, we synthesized irreversible lead compound 4, which targets Cys53 in a cavity on the BCL6-BTB domain dimer by introducing an irreversible warhead to high-throughput screening hit compound 1. Further chemical optimization of 4 based on kinact/KI evaluation produced BCL6-i with a kinact/KI value of 1.9 × 104 M-1 s-1, corresponding to a 670-fold improvement in potency compared to that of 4. By exploiting the property of irreversible inhibition, engagement of BCL6-i to intracellular BCL6 was confirmed. BCL6-i showed intracellular PPI inhibitory activity between BCL6 and its corepressors, thus resulting in BCL6-dependent DLBCL cell growth inhibition. BCL6-i is a cell-active chemical probe with the most potent BCL6 inhibitory activity reported to date. The discovery process of BCL6-i illustrates the utility of irreversible inhibition for identifying potent chemical probes for intractable target proteins.

Development of Protein Degradation Inducers of Androgen Receptor by Conjugation of Androgen Receptor Ligands and Inhibitor of Apoptosis Protein Ligands.

Targeted protein degradation using small molecules is a novel strategy for drug development. We have developed hybrid molecules named specific and nongenetic inhibitor of apoptosis protein [IAP]-dependent protein erasers (SNIPERs) that recruit IAP ubiquitin ligases to degrade target proteins. Here, we show novel SNIPERs capable of inducing proteasomal degradation of the androgen receptor (AR). Through derivatization of the SNIPER(AR) molecule at the AR ligand and IAP ligand and linker, we developed 42a (SNIPER(AR)-51), which shows effective protein knockdown activity against AR. Consistent with the degradation of the AR protein, 42a inhibits AR-mediated gene expression and proliferation of androgen-dependent prostate cancer cells. In addition, 42a efficiently induces caspase activation and apoptosis in prostate cancer cells, which was not observed in the cells treated with AR antagonists. These results suggest that SNIPER(AR)s could be leads for an anticancer drug against prostate cancers that exhibit AR-dependent proliferation.

Feedback activation of AMPK-mediated autophagy acceleration is a key resistance mechanism against SCD1 inhibitor-induced cell growth inhibition.

Elucidating the bioactive compound modes of action is crucial for increasing success rates in drug development. For anticancer drugs, defining effective drug combinations that overcome resistance improves therapeutic efficacy. Herein, by using a biologically annotated compound library, we performed a large-scale combination screening with Stearoyl-CoA desaturase-1 (SCD1) inhibitor, T-3764518, which partially inhibits colorectal cancer cell proliferation. T-3764518 induced phosphorylation and activation of AMPK in HCT-116 cells, which led to blockade of downstream fatty acid synthesis and acceleration of autophagy. Attenuation of fatty acid synthesis by small molecules suppressed the growth inhibitory effect of T-3764518. In contrast, combination of T-3764518 with autophagy flux inhibitors synergistically inhibited cellular proliferation. Experiments using SCD1 knock-out cells validated the results obtained with T-3764518. The results of our study indicated that activation of autophagy serves as a survival signal when SCD1 is inhibited in HCT-116 cells. Furthermore, these findings suggest that combining SCD1 inhibitor with autophagy inhibitors is a promising anticancer therapy.

Using a biologically annotated library to analyze the anticancer mechanism of serine palmitoyl transferase (SPT) inhibitors.

Mechanistic understanding is crucial to anticancer drug discovery. Here, we reveal that inhibition of serine palmitoyl transferase (SPT), the rate-limiting enzyme in sphingolipid synthesis, induced death in a lung cancer cell line via a necrosis-dependent pathway. To elucidate the mechanism of cell death induced by SPT inhibition, a biologically annotated library of diverse compounds was screened with an SPT inhibitor. This analysis identified suppressors of SPT inhibitor-mediated cell death. Further analysis using hit compounds from this screening revealed that SPT inhibitors induce COX-2 expression, leading to necrosis-dependent cell death. SPT inhibitors might therefore represent novel candidates for cancer therapy via necrosis pathway regulation. Our data illustrate that compound combination screening of biologically annotated libraries could be used for mechanistic elucidation.

In Vivo Knockdown of Pathogenic Proteins via Specific and Nongenetic Inhibitor of Apoptosis Protein (IAP)-dependent Protein Erasers (SNIPERs).

Many diseases, especially cancers, result from aberrant or overexpression of pathogenic proteins. Specific inhibitors against these proteins have shown remarkable therapeutic effects, but these are limited mainly to enzymes. An alternative approach that may have utility in drug development relies on selective degradation of pathogenic proteins via small chimeric molecules linking an E3 ubiquitin ligase to the targeted protein for proteasomal degradation. To this end, we recently developed a protein knockdown system based on hybrid small molecule SNIPERs (Specific and Nongenetic IAP-dependent Protein Erasers) that recruit inhibitor of the apoptosis protein (IAP) ubiquitin ligases to specifically degrade targeted proteins. Here, we extend our previous study to show a proof of concept of the SNIPER technology in vivo By incorporating a high affinity IAP ligand, we developed a novel SNIPER against estrogen receptor α (ERα), SNIPER(ER)-87, that has a potent protein knockdown activity. The SNIPER(ER) reduced ERα levels in tumor xenografts and suppressed the growth of ERα-positive breast tumors in mice. Mechanistically, it preferentially recruits X-linked IAP (XIAP) rather than cellular IAP1, to degrade ERα via the ubiquitin-proteasome pathway. With this IAP ligand, potent SNIPERs against other pathogenic proteins, BCR-ABL, bromodomain-containing protein 4 (BRD4), and phosphodiesterase-4 (PDE4) could also be developed. These results indicate that forced ubiquitylation by SNIPERs is a useful method to achieve efficient protein knockdown with potential therapeutic activities and could also be applied to study the role of ubiquitylation in many cellular processes.

Vacuolin-1 inhibits autophagy by impairing lysosomal maturation via PIKfyve inhibition.

Lysosomal protein degradation via autophagy strictly regulates cellular protein homoeostasis. Herein we performed high-content screening to identify compounds that inhibit autophagy pathways. We obtained 11 hit compounds and performed cluster analysis using cellular morphological information. Vacuolin-1, which induces the formation of giant vacuoles and is a target unknown compound, clustered with the known PIKfyve inhibitor YM201636. We further confirmed that vacuolin-1 is a potent PIKfyve inhibitor, and we finally concluded that PIKfyve inhibitors are novel chemical tools for regulating autophagy.

ABCG1 and ABCG4 Suppress γ-Secretase Activity and Amyloid ß Production.

ATP-binding cassette G1 (ABCG1) and ABCG4, expressed in neurons and glia in the central nervous system, mediate cholesterol efflux to lipid acceptors. The relationship between cholesterol level in the central nervous system and Alzheimer's disease has been reported. In this study, we examined the effects of ABCG1 and ABCG4 on amyloid precursor protein (APP) processing, the product of which, amyloid ß (Aß), is involved in the pathogenesis of Alzheimer's disease. Expression of ABCG1 or ABCG4 in human embryonic kidney 293 cells that stably expressed Swedish-type mutant APP increased cellular and cell surface APP levels. Products of cleavage from APP by α-secretase and by ß-secretase also increased. The levels of secreted Aß, however, decreased in the presence of ABCG1 and ABCG4, but not ABCG4-KM, a nonfunctional Walker-A lysine mutant. In contrast, secreted Aß levels increased in differentiated SH-SY5Y neuron-like cells in which ABCG1 and ABCG4 were suppressed. Furthermore, Aß42 peptide in the cerebrospinal fluid from Abcg1 null mice significantly increased compared to the wild type mice. To examine the underlying mechanism, we analyzed the activity and distribution of γ-secretase. ABCG1 and ABCG4 suppressed γ-secretase activity and disturbed γ-secretase localization in the raft domains where γ-secretase functions. These results suggest that ABCG1 and ABCG4 alter the distribution of γ-secretase on the plasma membrane, leading to the decreased γ-secretase activity and suppressed Aß secretion. ABCG1 and ABCG4 may inhibit the development of Alzheimer's disease and can be targets for the treatment of Alzheimer's disease.