ULK1-regulated AMP sensing by AMPK and its application for the treatment of chronic kidney disease.

Adenosine monophosphate (AMP)-activated protein kinase (AMPK) is a central kinase involved in energy homeostasis. Increased intracellular AMP levels result in AMPK activation through the binding of AMP to the γ-subunit of AMPK. Recently, we reported that AMP-induced AMPK activation is impaired in the kidneys in chronic kidney disease (CKD) despite an increase in the AMP/ATP ratio. However, the mechanisms by which AMP sensing is disrupted in CKD are unclear. Here, we identified mechanisms of energy homeostasis in which Unc-51-like kinase 1 (ULK1)-dependent phosphorylation of AMPKγ1 at Ser260/Thr262 promoting AMP sensitivity of AMPK. AMPK activation by AMP was impaired in Ulk1 knockout mice despite an increased AMP/ATP ratio. ULK1 expression is markedly downregulated in CKD kidneys, leading to AMP sensing failure. Additionally, MK8722, an allosteric AMPK activator, stimulated AMPK in the kidneys of a CKD mouse model (5/6th nephrectomy) via a pathway that is independent of AMP sensing. Thus, our study shows that MK8722 treatment significantly attenuates the deterioration of kidney function in CKD and may be a potential therapeutic option in CKD therapeutics.

A high dose KRP203 induces cytoplasmic vacuoles associated with altered phosphoinositide segregation and endosome expansion.

In animal cells, vacuoles are absent, but can be induced by diseases and drugs. While phosphoinositides are critical for membrane trafficking, their role in the formation of these vacuoles remains unclear. The immunosuppressive KRP203/Mocravimod, which antagonizes sphingosine-1-phosphate receptors, has been identified as having novel multimodal activity against phosphoinositide kinases. However, the impact of this novel KRP203 activity is unknown. Here, we show that KRP203 disrupts the spatial organization of phosphoinositides and induces extensive vacuolization in tumor cells and immortalized fibroblasts. The KRP203-induced vacuoles are primarily from endosomes, and augmented by inhibition of PIKFYVE and VPS34. Conversely, overexpression of PTEN decreased KRP203-induced vacuole formation. Furthermore, V-ATPase inhibition completely blunted KRP203-induced vacuolization, pointing to a critical requirement of the endosomal maturation process. Importantly, nearly a half of KRP203-induced vacuoles are significantly decorated with PI4P, a phosphoinositide typically enriched at the plasma membrane and Golgi. These results suggest a model that noncanonical spatial reorganization of phosphoinositides by KRP203 alters the endosomal maturation process, leading to vacuolization. Taken together, this study reveals a previously unrecognized bioactivity of KRP203 as a vacuole-inducing agent and its unique mechanism of phosphoinositide modulation, providing a new insight of phosphoinositide regulation into vacuolization-associated diseases and their molecular pathologies.

Absence of ULK1 decreases AMPK activity in the kidney, leading to chronic kidney disease progression.

AMP-activated protein kinase (AMPK) inactivation in chronic kidney disease (CKD) leads to energy status deterioration in the kidney, constituting the vicious cycle of CKD exacerbation. Unc-51-like kinase 1 (ULK1) is considered a downstream molecule of AMPK; however, it was recently reported that the activity of AMPK could be regulated by ULK1 conversely. We demonstrated that AMPK and ULK1 activities were decreased in the kidneys of CKD mice. However, whether and how ULK1 is involved in the underlying mechanism of CKD exacerbation remains unknown. In this study, we investigated the ULK1 involvement in CKD, using ULK1 knockout mice. The CKD model of Ulk1-/- mice exhibited significantly exacerbated renal function and worsening renal fibrosis. In the kidneys of the CKD model of Ulk1-/- mice, reduced AMPK and its downstream ß-oxidation could be observed, leading to an energy deficit of increased AMP/ATP ratio. In addition, AMPK signaling in the kidney was reduced in control Ulk1-/- mice with normal renal function compared to control wild-type mice, suggesting that ULK1 deficiency suppressed AMPK activity in the kidney. This study is the first to present ULK1 as a novel therapeutic target for CKD treatment, which regulates AMPK activity in the kidney.

The Lipid Kinase PI5P4Kß Is an Intracellular GTP Sensor for Metabolism and Tumorigenesis.

While cellular GTP concentration dramatically changes in response to an organism's cellular status, whether it serves as a metabolic cue for biological signaling remains elusive due to the lack of molecular identification of GTP sensors. Here we report that PI5P4Kß, a phosphoinositide kinase that regulates PI(5)P levels, detects GTP concentration and converts them into lipid second messenger signaling. Biochemical analyses show that PI5P4Kß preferentially utilizes GTP, rather than ATP, for PI(5)P phosphorylation, and its activity reflects changes in direct proportion to the physiological GTP concentration. Structural and biological analyses reveal that the GTP-sensing activity of PI5P4Kß is critical for metabolic adaptation and tumorigenesis. These results demonstrate that PI5P4Kß is the missing GTP sensor and that GTP concentration functions as a metabolic cue via PI5P4Kß. The critical role of the GTP-sensing activity of PI5P4Kß in cancer signifies this lipid kinase as a cancer therapeutic target.

Isolation and Structure Elucidation of JBIR-157, a Skeletally Novel Aromatic Polyketide Produced by the Heterologous Expression of a Cryptic Gene Cluster.

Heterologous expression of natural compound biosynthetic gene clusters (BGCs) is a robust approach for not only revealing the biosynthetic mechanisms leading to the compounds, but also for discovering new products from uncharacterized BGCs. We established a heterologous expression technique applicable to huge biosynthetic gene clusters for generating large molecular secondary metabolites such as type-I polyketides. As an example, we targeted concanamycin BGC from Streptomyces neyagawaensis IFO13477 (the cluster size of 99 kbp), and obtained a bacterial artificial chromosome (BAC) clone with an insert size of 211 kbp that contains the entire concanamycin BGC. Interestingly, heterologous expression for this BAC clone resulted in two additional aromatic polyketides, ent-gephyromycin, and a new compound designated as JBIR-157, together with the expected concanamycin. Bioinformatic and biochemical analyses revealed that a cryptic biosynthetic gene cluster in this BAC clone was responsible for the production of these type-II polyketide synthases (PKS) compounds. Here, we describe the production, isolation, and structure elucidation of JBIR-157, determined primarily by a series of NMR spectral analyses.

Multimodal action of KRP203 on phosphoinositide kinases in vitro and in cells.

Increased phosphoinositide signaling is commonly associated with cancers. While "one-drug one-target" has been a major drug discovery strategy for cancer therapy, a "one-drug multi-targets" approach for phosphoinositide enzymes has the potential to offer a new therapeutic approach. In this study, we sought a new way to target phosphoinositides metabolism. Using a high-throughput phosphatidylinositol 5-phosphate 4-kinase-alpha (PI5P4Kα) assay, we have identified that the immunosuppressor KRP203/Mocravimod induces a significant perturbation in phosphoinositide metabolism in U87MG glioblastoma cells. Despite high sequence similarity of PI5P4K and PI4K isozymes, in vitro kinase assays showed that KRP203 activates some (e.g., PI5P4Kα, PI4KIIß) while inhibiting other phosphoinositide kinases (e.g., PI5P4Kß, γ, PI4KIIα, class I PI3K-p110α, δ, γ). Furthermore, KRP203 enhances PI3P5K/PIKFYVE's substrate selectivity for phosphatidylinositol (PI) while preserving its selectivity for PI(3)P. At cellular levels, 3 h of KRP203 treatment induces a prominent increase of PI(3)P and moderate increase of PI(5)P, PI(3,5)P2, and PI(3,4,5)P3 levels in U87MG cells. Collectively, the finding of multimodal activity of KRP203 towards multi-phosphoinositide kinases may open a novel basis to modulate cellular processes, potentially leading to more effective treatments for diseases associated with phosphoinositide signaling pathways.

Role of the Orphan Transporter SLC35E1 in the Nuclear Egress of Herpes Simplex Virus 1.

This study developed a system consisting of two rounds of screening cellular proteins involved in the nuclear egress of herpes simplex virus 1 (HSV-1). Using this system, we first screened cellular proteins that interacted with the HSV-1 nuclear egress complex (NEC) consisting of UL34 and UL31 in HSV-1-infected cells, which are critical for the nuclear egress of HSV-1, by tandem affinity purification coupled with mass spectrometry-based proteomics technology. Next, we performed CRISPR/Cas9-based screening of live HSV-1-infected reporter cells under fluorescence microscopy using single guide RNAs targeting the cellular proteins identified in the first proteomic screening to detect the mislocalization of the lamin-associated protein emerin, which is a phenotype for defects in HSV-1 nuclear egress. This study focused on a cellular orphan transporter SLC35E1, one of the cellular proteins identified by the screening system. Knockout of SLC35E1 reduced HSV-1 replication and induced membranous invaginations containing perinuclear enveloped virions (PEVs) adjacent to the nuclear membrane (NM), aberrant accumulation of PEVs in the perinuclear space between the inner and outer NMs and the invagination structures, and mislocalization of the NEC. These effects were similar to those of previously reported mutation(s) in HSV-1 proteins and depletion of cellular proteins that are important for HSV-1 de-envelopment, one of the steps required for HSV-1 nuclear egress. Our newly established screening system enabled us to identify a novel cellular protein required for efficient HSV-1 de-envelopment. IMPORTANCE The identification of cellular protein(s) that interact with viral effector proteins and function in important viral procedures is necessary for enhancing our understanding of the mechanics of various viral processes. In this study, we established a new system consisting of interactome screening for the herpes simplex virus 1 (HSV-1) nuclear egress complex (NEC), followed by loss-of-function screening to target the identified putative NEC-interacting cellular proteins to detect a defect in HSV-1 nuclear egress. This newly established system identified SLC35E1, an orphan transporter, as a novel cellular protein required for efficient HSV-1 de-envelopment, providing an insight into the mechanisms involved in this viral procedure.

Helix-forming aliphatic homo-δ-peptide foldamers based on the conformational restriction effects of cyclopropane.

Considerable effort has been directed toward developing artificial peptide-based foldamers. However, detailed structural analysis of δ-peptide foldamers consisting of only aliphatic δ-amino acids has not been reported. Herein, we rationally designed and stereoselectively synthesized aliphatic homo-δ-peptides forming a stable helical structure by using a chiral cyclopropane δ-amino acid as a monomer unit. Structural analysis of the homo-δ-peptides using circular dichroism, infrared, and NMR spectroscopy indicated that they form a stable 14-helical structure in solution. Furthermore, we successfully conducted X-ray crystallographic analysis of the homo-δ-peptides, demonstrating a right-handed 14-helical structure. This helical structure of the crystal was consistent with those predicted by theoretical calculations and those obtained based on NMR spectroscopy in solution. This stable helical structure is due to the effective restriction of the backbone conformation by the structural characteristics of cyclopropane. This work reports the first example of aliphatic homo-δ-peptide foldamers having a stable helical structure both in the solution and crystal states.

Aromatic 19F-13C TROSY: a background-free approach to probe biomolecular structure, function, and dynamics.

Atomic-level information about the structure and dynamics of biomolecules is critical for an understanding of their function. Nuclear magnetic resonance (NMR) spectroscopy provides unique insights into the dynamic nature of biomolecules and their interactions, capturing transient conformers and their features. However, relaxation-induced line broadening and signal overlap make it challenging to apply NMR spectroscopy to large biological systems. Here we took advantage of the high sensitivity and broad chemical shift range of 19F nuclei and leveraged the remarkable relaxation properties of the aromatic 19F-13C spin pair to disperse 19F resonances in a two-dimensional transverse relaxation-optimized spectroscopy spectrum. We demonstrate the application of 19F-13C transverse relaxation-optimized spectroscopy to investigate proteins and nucleic acids. This experiment expands the scope of 19F NMR in the study of the structure, dynamics, and function of large and complex biological systems and provides a powerful background-free NMR probe.

Residue-based program of a ß-peptoid twisted strand shape via a cyclopentane constraint.

N-Substituted peptides, such as peptoids and ß-peptoids, have been reported to have unique structures with diverse functions, like catalysis and manipulation of biomolecular functions. Recently, the preorganization of monomer shape by restricting bond rotations about all backbone dihedral angles has been demonstrated to be useful for de novo design of peptoid structures. Such design strategies are hitherto unexplored for ß-peptoids; to date, no preorganized ß-peptoid monomers have been reported. Here, we report the first design strategy for ß-peptoids, in which all four backbone dihedral angles (ω, ϕ, θ, ψ) are rotationally restricted on a per-residue basis. The introduction of a cyclopentane constraint realized the preorganized monomer structure and led to a ß-peptoid with a stable twisted strand shape.

Conformational equilibrium defines the variable induction of the multidrug-binding transcriptional repressor QacR.

QacR, a multidrug-binding transcriptional repressor in pathogenic bacteria Staphylococcus aureus, modulates the transcriptional level of the multidrug transporter gene, qacA, in response to engaging a set of diverse ligands. However, the structural basis that defines the variable induction level remains unknown. Here, we reveal that the conformational equilibrium between the repressive and inducive conformations in QacR defines the induction level of the transporter gene. In addition, the unligated QacR is already partly populated in the inducive conformation, allowing the basal expression of the transporter. We also showed that, in the known constitutively active QacR mutants, the equilibrium is shifted more toward the inducive conformation, even in the unligated state. These results highlight the unexpected structural mechanism, connecting the promiscuous multidrug binding to the variable transcriptional regulation of QacR, which provide clues to dysfunctioning of the multidrug resistance systems.

Oligo(N-methylalanine) as a Peptide-Based Molecular Scaffold with a Minimal Structure and High Density of Functionalizable Sites.

Functionalizable synthetic molecules with nanometer sizes and defined shapes in water are useful as molecular scaffolds to mimic the functions of biomacromolecules and develop chemical tools for manipulating biomacromolecules. Herein, we propose oligo(N-methylalanine) (oligo-NMA) as a peptide-based molecular scaffold with a minimal structure and a high density of functionalizable sites. Oligo-NMA forms a defined shape in water without hydrogen-bonding networks or ring constraints, which enables the molecule to act as a scaffold with minimal atomic composition. Furthermore, functional groups can be readily introduced on the nitrogens and α-carbons of oligo-NMA. Computational and NMR spectroscopic analysis suggested that the backbone structure of oligo-NMA is not largely affected by functionalization. Moreover, the usefulness of oligo-NMA was demonstrated by the design of protein ligands. The ease of synthesis, minimal structure, and high functionalization flexibility makes oligo-NMA a useful scaffold for chemical and biological applications.

Nonthermal excitation effects mediated by sub-terahertz radiation on hydrogen exchange in ubiquitin.

Water dynamics in the hydration layers of biomolecules play crucial roles in a wide range of biological functions. A hydrated protein contains multiple components of diffusional and vibrational dynamics of water and protein, which may be coupled at ∼0.1-THz frequency (10-ps timescale) at room temperature. However, the microscopic description of biomolecular functions based on various modes of protein-water-coupled motions remains elusive. A novel approach for perturbing the hydration dynamics in the subterahertz frequency range and probing them at the atomic level is therefore warranted. In this study, we investigated the effect of klystron-based, intense 0.1-THz excitation on the slow dynamics of ubiquitin using NMR-based measurements of hydrogen-deuterium exchange. We demonstrated that the subterahertz irradiation accelerated the hydrogen-deuterium exchange of the amides located in the interior of the protein and hydrophobic surfaces while decelerating this exchange in the amides located in the surface loop and short 310 helix regions. This subterahertz-radiation-induced effect was qualitatively contradictory to the increased-temperature-induced effect. Our results suggest that the heterogeneous water dynamics occurring at the protein-water interface include components that are nonthermally excited by the subterahertz radiation. Such subterahertz-excited components may be linked to the slow function-related dynamics of the protein.

Flexibility and Cell Permeability of Cyclic Ras-Inhibitor Peptides Revealed by the Coupled Nosé-Hoover Equation.

Quantifying the cell permeability of cyclic peptides is crucial for their rational drug design. However, the reasons remain unclear why a minor chemical modification, such as the difference between Ras inhibitors cyclorasin 9A5 and 9A54, can substantially change a peptide's permeability. To address this question, we performed enhanced sampling simulations of these two 11-mer peptides using the coupled Nosé-Hoover equation (cNH) we recently developed. The present cNH simulations realized temperature fluctuations over a wide range (240-600 K) in a dynamic manner, allowing structural samplings that were well validated by nuclear Overhauser effect measurements. The derived structural ensembles were comprehensively analyzed by all-atom structural clustering, mapping the derived clusters onto principal components (PCs) that characterize the cyclic structure, and calculating cluster-dependent geometric and chemical properties. The planar-open conformation was dominant in aqueous solvent, owing to inclusion of the Trp side chain in the main-chain ring, while the compact-closed conformation, which favors cell permeation due to its compactness and high polarity, was also accessible. Conformation-dependent cell permeability was observed in one of the derived PCs, demonstrating that decreased cell permeability in 9A54 is due to the high free energy barrier separating the two conformations. The origin of the change in free energy surface was determined to be loss of flexibility in the modified residues 2-3, resulting from the increased bulkiness of their side chains. The derived molecular mechanism of cell permeability highlights the significance of complete structural dynamics surveys for accelerating drug development with cyclic peptides.

15N detection harnesses the slow relaxation property of nitrogen: Delivering enhanced resolution for intrinsically disordered proteins.

Studies over the past decade have highlighted the functional significance of intrinsically disordered proteins (IDPs). Due to conformational heterogeneity and inherent dynamics, structural studies of IDPs have relied mostly on NMR spectroscopy, despite IDPs having characteristics that make them challenging to study using traditional 1H-detected biomolecular NMR techniques. Here, we develop a suite of 3D 15N-detected experiments that take advantage of the slower transverse relaxation property of 15N nuclei, the associated narrower linewidth, and the greater chemical shift dispersion compared with those of 1H and 13C resonances. The six 3D experiments described here start with aliphatic 1H magnetization to take advantage of its higher initial polarization, and are broadly applicable for backbone assignment of proteins that are disordered, dynamic, or have unfavorable amide proton exchange rates. Using these experiments, backbone resonance assignments were completed for the unstructured regulatory domain (residues 131-294) of the human transcription factor nuclear factor of activated T cells (NFATC2), which includes 28 proline residues located in functionally important serine-proline (SP) repeats. The complete assignment of the NFATC2 regulatory domain enabled us to study phosphorylation of NFAT by kinase PKA and phosphorylation-dependent binding of chaperone protein 14-3-3 to NFAT, providing mechanistic insight on how 14-3-3 regulates NFAT nuclear translocation.

Conformational Plasticity of Cyclic Ras-Inhibitor Peptides Defines Cell Permeabilization Activity.

Cyclorasins 9A5 and 9A54 are 11-mer cyclic peptides that inhibit the Ras-Raf protein interaction. The peptides share a cell-penetrating peptide (CPP)-like motif; however, only cyclorasin 9A5 can permeabilize cells to exhibit strong cell-based activity. To unveil the structural origin underlying their distinct cellular permeabilization activities, we compared the three-dimensional structures of cyclorasins 9A5 and 9A54 in water and in the less polar solvent dimethyl sulfoxide (DMSO) by solution NMR. We found that cyclorasin 9A5 changes its extended conformation in water to a compact amphipathic structure with converged aromatic residues surrounded by Arg residues in DMSO, which might contribute to its cell permeabilization activity. However, cyclorasin 9A54 cannot adopt this amphipathic structure, due to the steric hindrance between two neighboring bulky amino-acid sidechains, Tle-2 and dVal-3. We also found that the bulkiness of the sidechains at positions 2 and 3 negatively affects the cell permeabilization activities, indicating that the conformational plasticity that allows the peptides to form the amphipathic structure is important for their cell permeabilization activities.

Transcription Factor Binding in Embryonic Stem Cells Is Constrained by DNA Sequence Repeat Symmetry.

Transcription factor (TF) recognition is dictated by the underlying DNA motif sequence specific for each TF. Here, we reveal that DNA sequence repeat symmetry plays a central role in defining TF-DNA-binding preferences. In particular, we find that different TFs bind similar symmetry patterns in the context of different developmental layers. Most TFs possess dominant preferences for similar DNA repeat symmetry types. However, in some cases, preferences of specific TFs are changed during differentiation, suggesting the importance of information encoded outside of known motif regions. Histone modifications also exhibit strong preferences for similar DNA repeat symmetry patterns unique to each type of modification. Next, using an in vivo reporter assay, we show that gene expression in embryonic stem cells can be positively modulated by the presence of genomic and computationally designed DNA oligonucleotides containing identified nonconsensus-repetitive sequence elements. This supports the hypothesis that certain nonconsensus-repetitive patterns possess a functional ability to regulate gene expression. We also performed a solution NMR experiment to probe the stability of double-stranded DNA via imino proton resonances for several double-stranded DNA sequences characterized by different repetitive patterns. We suggest that such local stability might play a key role in determining TF-DNA binding preferences. Overall, our findings show that despite the enormous sequence complexity of the TF-DNA binding landscape in differentiating embryonic stem cells, this landscape can be quantitatively characterized in simple terms using the notion of DNA sequence repeat symmetry.

A BRET-based assay reveals collagen-Hsp47 interaction dynamics in the endoplasmic reticulum and small-molecule inhibition of this interaction.

Molecular chaperones perform pivotal roles in proteostasis by engaging in protein-protein interactions (PPIs). The collagen-specific molecular chaperone Hsp47 (heat shock protein 47) interacts with procollagen in the endoplasmic reticulum (ER) and plays crucial roles in collagen synthesis. PPIs between Hsp47 and collagen could offer a therapeutic target for fibrosis, which is characterized by abnormal collagen accumulation in the extracellular matrix of fibrotic organs. Herein, we established a bioluminescence resonance energy transfer (BRET) system for assessing Hsp47-collagen interaction dynamics within the ER. After optimization and validation of the method, we could demonstrate inhibition of the interaction between Hsp47 and collagen by a small molecule (Col003) in the ER. Using the BRET system, we also found that Hsp47 interacts not only with the Gly-Pro-Arg motif but also weakly with Gly-Pro-Hyp motifs of triple-helical collagen in cells. Moreover, we found that the serpin loop of Hsp47 (SerpinH1) contributes to its binding to collagen. We propose that the method developed here can provide valuable information on PPIs between Hsp47 and collagen and on the effects of PPI inhibitors important for the management of fibrotic disorders.

The role of NMR in leveraging dynamics and entropy in drug design.

Nuclear magnetic resonance (NMR) spectroscopy has contributed to structure-based drug development (SBDD) in a unique way compared to the other biophysical methods. The potency of a ligand binding to a protein is dictated by the binding free energy, which is an intricate interplay between entropy and enthalpy. In addition to providing the atomic resolution structural information, NMR can help to identify protein-ligand interactions that potentially contribute to the enthalpic component of the free energy. NMR can also illuminate dynamic aspects of the interaction, which correspond to the entropic term of the free energy. The ability of NMR to access both terms in the free energy equation stems from the suite of experiments developed to shed light on various aspects that contribute to both entropy and enthalpy, deepening our understanding of the biological function of macromolecules and assisting to target them in physiological conditions. Here we provide a brief account of the contribution of NMR to SBDD, highlighting hallmark examples and discussing the challenges that demand further method development. In the era of integrated biology, the unique ability of NMR to directly ascertain structural and dynamical aspects of macromolecule and monitor changes in these properties upon engaging a ligand can be combined with computational and other structural and biophysical methods to provide a more complete picture of the energetics of drug engagement with the target. Such efforts can be used to engineer better drugs.

Correction to: The role of NMR in leveraging dynamics and entropy in drug design.

Unfortunately, in the original publication, Fig. 5 was published incorrectly. The correct version is given below.