scholarly journals Novel allosteric mechanism of dual p53/MDM2 and p53/MDM4 inhibition by a small molecule

2021 ◽  
Author(s):  
Vera Grinkevich ◽  
Vema Aparna ◽  
Karin Fawkner ◽  
Natalia Issaeva ◽  
Virginia Andreotti ◽  
...  
Keyword(s):  
Ion Mobility ◽  
Molecular Mechanisms ◽  
Protoporphyrin Ix ◽  
Alternative Mechanism ◽  
Allosteric Inhibitors ◽  
Promising Strategy ◽  
Allosteric Mechanism ◽  
Biochemical Assays ◽  
Binding Residues ◽  
P53 Reactivation

Restoration of the p53 tumor suppressor for personalised cancer therapy is a promising strategy. However, high-affinity MDM2 inhibitors have shown substantial side effects in clinical trials. Thus, elucidation of the molecular mechanisms of action of p53 reactivating molecules with alternative functional principle is of the utmost importance. Here, we report a discovery of a novel allosteric mechanism of p53 reactivation through targeting the p53 N-terminus which blocks both p53/MDM2 and p53/MDM4 interactions. Using biochemical assays and molecular docking, we identified the binding site of two p53 reactivating molecules, RITA and protoporphyrin IX (PpIX). Ion-mobility mass spectrometry revealed that the binding of RITA to serine 33 and serine 37 is responsible for inducing the allosteric shift in p53, which shields the MDM2 binding residues of p53 and prevents its interactions with MDM2 and MDM4. Our results point to an alternative mechanism of blocking p53 interaction with MDM2 and MDM4 and may pave the way for the development of novel allosteric inhibitors of p53/MDM2 and p53/MDM4 interactions.

scholarly journals Gene Transcription as a Therapeutic Target in Leukemia

2021 ◽  
Vol 22 (14) ◽  
pp. 7340
Author(s):  
Alvina I. Khamidullina ◽  
Ekaterina A. Varlamova ◽  
Nour Alhuda Hammoud ◽  
Margarita A. Yastrebova ◽  
Alexandra V. Bruter
Keyword(s):  
Gene Transcription ◽  
Molecular Mechanisms ◽  
Hematological Malignancies ◽  
Mechanisms Of Action ◽  
Special Program ◽  
Cell Plasticity ◽  
Hematopoietic Stem ◽  
Promising Strategy ◽  
Tumor Cell Plasticity ◽  
Transcriptional Landscape

Blood malignancies often arise from undifferentiated hematopoietic stem cells or partially differentiated stem-like cells. A tight balance of multipotency and differentiation, cell division, and quiescence underlying normal hematopoiesis requires a special program governed by the transcriptional machinery. Acquisition of drug resistance by tumor cells also involves reprogramming of their transcriptional landscape. Limiting tumor cell plasticity by disabling reprogramming of the gene transcription is a promising strategy for improvement of treatment outcomes. Herein, we review the molecular mechanisms of action of transcription-targeted drugs in hematological malignancies (largely in leukemia) with particular respect to the results of clinical trials.

scholarly journals MAPK/ERK Signaling Pathway in Hepatocellular Carcinoma

Cancers ◽  
2021 ◽  
Vol 13 (12) ◽  
pp. 3026
Author(s):  
Hyuk Moon ◽  
Simon-Weonsang Ro
Keyword(s):  
Hepatocellular Carcinoma ◽  
Signaling Pathway ◽  
Molecular Mechanisms ◽  
Therapeutic Strategies ◽  
Erk Signaling ◽  
Health Concern ◽  
Alternative Mechanism ◽  
Major Health ◽  
Activating Mutations ◽  
Genetic Events

Hepatocellular carcinoma (HCC) is a major health concern worldwide, and its incidence is increasing steadily. Recently, the MAPK/ERK signaling pathway in HCC has gained renewed attention from basic and clinical researchers. The MAPK/ERK signaling pathway is activated in more than 50% of human HCC cases; however, activating mutations in RAS and RAF genes are rarely found in HCC, which are major genetic events leading to the activation of the MAPK/ERK signaling pathway in other cancers. This suggests that there is an alternative mechanism behind the activation of the signaling pathway in HCC. Here, we will review recent advances in understanding the cellular and molecular mechanisms involved in the activation of the MAPK/ERK signaling pathway and discuss potential therapeutic strategies targeting the signaling pathway in the context of HCC.

scholarly journals Bridging the gap between structure and kinetics of human SGLT1

2012 ◽  
Vol 302 (9) ◽  
pp. C1293-C1305 ◽  
Author(s):  
Monica Sala-Rabanal ◽  
Bruce A. Hirayama ◽  
Donald D. F. Loo ◽  
Vincent Chaptal ◽  
Jeff Abramson ◽  
...  
Keyword(s):  
Ligand Binding ◽  
Binding Site ◽  
Sugar Transport ◽  
Gene Families ◽  
Structural Studies ◽  
Sugar Binding ◽  
Substituted Cysteine Accessibility ◽  
Biochemical Assays ◽  
Functional Consequences ◽  
Binding Residues

The Na+-glucose cotransporter hSGLT1 is a member of a class of membrane proteins that harness Na+ electrochemical gradients to drive uphill solute transport. Although hSGLT1 belongs to one gene family (SLC5), recent structural studies of bacterial Na+ cotransporters have shown that Na+ transporters in different gene families have the same structural fold. We have constructed homology models of hSGLT1 in two conformations, the inward-facing occluded (based on vSGLT) and the outward open conformations (based on Mhp1), mutated in turn each of the conserved gates and ligand binding residues, expressed the SGLT1 mutants in Xenopus oocytes, and determined the functional consequences using biophysical and biochemical assays. The results establish that mutating the ligand binding residues produces profound changes in the ligand affinity (the half-saturation concentration, K0.5); e.g., mutating sugar binding residues increases the glucose K0.5 by up to three orders of magnitude. Mutation of the external gate residues increases the Na+ to sugar transport stoichiometry, demonstrating that these residues are critical for efficient cotransport. The changes in phlorizin inhibition constant ( Ki) are proportional to the changes in sugar K0.5, except in the case of F101C, where phlorizin Ki increases by orders of magnitude without a change in glucose K0.5. We conclude that glucose and phlorizin occupy the same binding site and that F101 is involved in binding to the phloretin group of the inhibitor. Substituted-cysteine accessibility methods show that the cysteine residues at the position of the gates and sugar binding site are largely accessible only to external hydrophilic methanethiosulfonate reagents in the presence of external Na+, demonstrating that the external sugar (and phlorizin) binding vestibule is opened by the presence of external Na+ and closes after the binding of sugar and phlorizin. Overall, the present results provide a bridge between kinetics and structural studies of cotransporters.

scholarly journals Diversity of molecular mechanisms used by anti-CRISPR proteins: the tip of an iceberg?

2020 ◽  
Vol 48 (2) ◽  
pp. 507-516 ◽  
Author(s):  
Pierre Hardouin ◽  
Adeline Goulet
Keyword(s):  
Immune System ◽  
Structure Function ◽  
Defense Mechanisms ◽  
Molecular Mechanisms ◽  
Current Knowledge ◽  
Arms Race ◽  
Allosteric Inhibitors ◽  
Fundamental Knowledge ◽  
Attack And Defense ◽  
Fine Tune

Bacteriophages (phages) and their preys are engaged in an evolutionary arms race driving the co-adaptation of their attack and defense mechanisms. In this context, phages have evolved diverse anti-CRISPR proteins to evade the bacterial CRISPR–Cas immune system, and propagate. Anti-CRISPR proteins do not share much resemblance with each other and with proteins of known function, which raises intriguing questions particularly relating to their modes of action. In recent years, there have been many structure–function studies shedding light on different CRISPR–Cas inhibition strategies. As the anti-CRISPR field of research is rapidly growing, it is opportune to review the current knowledge on these proteins, with particular emphasis on the molecular strategies deployed to inactivate distinct steps of CRISPR–Cas immunity. Anti-CRISPR proteins can be orthosteric or allosteric inhibitors of CRISPR–Cas machineries, as well as enzymes that irreversibly modify CRISPR–Cas components. This repertoire of CRISPR–Cas inhibition mechanisms will likely expand in the future, providing fundamental knowledge on phage–bacteria interactions and offering great perspectives for the development of biotechnological tools to fine-tune CRISPR–Cas-based gene edition.

scholarly journals Photosystem Disorder Could be the Key Cause for the Formation of Albino Leaf Phenotype in Pecan

2020 ◽  
Vol 21 (17) ◽  
pp. 6137
Author(s):  
Ji-Yu Zhang ◽  
Tao Wang ◽  
Zhan-Hui Jia ◽  
Zhong-Ren Guo ◽  
Yong-Zhi Liu ◽  
...  
Keyword(s):  
Chlorophyll A ◽  
Molecular Mechanisms ◽  
Chlorophyll Biosynthesis ◽  
Protoporphyrin Ix ◽  
Photosynthetic Electron Transport ◽  
Chlorophyll Degradation ◽  
Pheophorbide A ◽  
Leaf Phenotype ◽  
Photosynthesis Pathway ◽  
Almost All

Pecan is one of the most famous nut species in the world. The phenotype of mutants with albino leaves was found in the process of seeding pecan, providing ideal material for the study of the molecular mechanisms leading to the chlorina phenotype in plants. Both chlorophyll a and chlorophyll b contents in albino leaves (ALs) were significantly lower than those in green leaves (GLs). A total of 5171 differentially expression genes (DEGs) were identified in the comparison of ALs vs. GLs using high-throughput transcriptome sequencing; 2216 DEGs (42.85%) were upregulated and 2955 DEGs (57.15%) were downregulated. The expressions of genes related to chlorophyll biosynthesis (HEMA1, encoding glutamyl-tRNA reductase; ChlH, encoding Mg-protoporphyrin IX chelatase (Mg-chelatase) H subunit; CRD, encoding Mg-protoporphyrin IX monomethylester cyclase; POR, encoding protochlorophyllide reductase) in ALs were significantly lower than those in GLs. However, the expressions of genes related to chlorophyll degradation (PAO, encoding pheophorbide a oxygenase) in ALs were significantly higher than those in GLs, indicating that disturbance of chlorophyll a biosynthesis and intensification of chlorophyll degradation lead to the absence of chlorophyll in ALs of pecan. A total of 72 DEGs associated with photosynthesis pathway were identified in ALs compared to GLs, including photosystem I (15), photosystem II (19), cytochrome b6-f complex (3), photosynthetic electron transport (6), F-type ATPase (7), and photosynthesis-antenna proteins (22). Moreover, almost all the genes (68) mapped in the photosynthesis pathway showed decreased expression in ALs compared to GLs, declaring that the photosynthetic system embedded within the thylakoid membrane of chloroplast was disturbed in ALs of pecan. This study provides a theoretical basis for elucidating the molecular mechanism underlying the phenotype of chlorina seedlings of pecan.

scholarly journals Conformational changes in a pore-forming region underlie voltage-dependent “loop gating” of an unapposed connexin hemichannel

2009 ◽  
Vol 133 (6) ◽  
pp. 555-570 ◽  
Author(s):  
Qingxiu Tang ◽  
Terry L. Dowd ◽  
Vytas K. Verselis ◽  
Thaddeus A. Bargiello
Keyword(s):  
Conformational Changes ◽  
Disulfide Bonds ◽  
Molecular Mechanisms ◽  
Extracellular Loop ◽  
Connexin Gene ◽  
Gating Mechanism ◽  
Biochemical Assays ◽  
Voltage Dependent ◽  
Tm Domain ◽  
Connexin Hemichannel

The structure of the pore is critical to understanding the molecular mechanisms underlying selective permeation and voltage-dependent gating of channels formed by the connexin gene family. Here, we describe a portion of the pore structure of unapposed hemichannels formed by a Cx32 chimera, Cx32*Cx43E1, in which the first extracellular loop (E1) of Cx32 is replaced with the E1 of Cx43. Cysteine substitutions of two residues, V38 and G45, located in the vicinity of the border of the first transmembrane (TM) domain (TM1) and E1 are shown to react with the thiol modification reagent, MTSEA–biotin-X, when the channel resides in the open state. Cysteine substitutions of flanking residues A40 and A43 do not react with MTSEA–biotin-X when the channel resides in the open state, but they react with dibromobimane when the unapposed hemichannels are closed by the voltage-dependent “loop-gating” mechanism. Cysteine substitutions of residues V37 and A39 do not appear to be modified in either state. Furthermore, we demonstrate that A43C channels form a high affinity Cd2+ site that locks the channel in the loop-gated closed state. Biochemical assays demonstrate that A43C can also form disulfide bonds when oocytes are cultured under conditions that favor channel closure. A40C channels are also sensitive to micromolar Cd2+ concentrations when closed by loop gating, but with substantially lower affinity than A43C. We propose that the voltage-dependent loop-gating mechanism for Cx32*Cx43E1 unapposed hemichannels involves a conformational change in the TM1/E1 region that involves a rotation of TM1 and an inward tilt of either each of the six connexin subunits or TM1 domains.

scholarly journals Rewiring Glucose Metabolism Improves 5-FU Efficacy in Glycolytic p53-Deficient Colorectal Tumors

2021 ◽  
Author(s):  
Marlies Ludikhuize ◽  
Sira Gevers ◽  
Nguyen Nguyen ◽  
Maaike Meerlo ◽  
S. Khadijeh Shafiei Roudbari ◽  
...  
Keyword(s):  
Dna Damage ◽  
Cell Death ◽  
Glucose Metabolism ◽  
Molecular Mechanisms ◽  
Genetically Engineered ◽  
Driver Mutations ◽  
Cycle Arrest ◽  
Promising Strategy ◽  
Clinical Models ◽  
The Warburg Effect

Abstract 5-fluorouracil (5-FU) is the backbone for chemotherapy in colorectal cancer (CRC), however response rates in patients are limited to 50%. Unexpectedly, the molecular mechanisms by which 5-FU ultimately induces toxicity remain debated, limiting the development of strategies to improve its efficacy. How fundamental aspects of cancer, such as driver mutations and phenotypic intra-tumor heterogeneity, relate to the 5-FU response are ill-defined. This is largely due to a shortage of mechanistic studies in pre-clinical models able to recapitulate the key-features of CRC. Here, we analyzed the 5-FU response in human organoids genetically engineered to reproduce the different stages of CRC progression. We find that 5-FU induces pyrimidine imbalance, which leads to DNA damage and cell death. Actively proliferating cancer (stem) cells are, accordingly, efficiently targeted by 5-FU. Importantly, p53 behaves as a discriminating factor for 5-FU sensitivity, whereas p53-deficiency leads to DNA damage-induced cell death, active p53 protects from these effects through inducing cell cycle arrest. Moreover, we find that targeting the Warburg effect, by rewiring glucose metabolism, enhances 5-FU toxicity by altering the nucleotide pool and without increasing toxicity in non-transformed cells. Thus, rewiring glucose metabolism in combination with replication stress-inducing chemotherapies emerges as a promising strategy for CRC treatment.

scholarly journals DDK regulates replication initiation by controlling the multiplicity of Cdc45-GINS binding to Mcm2-7

2020 ◽  
Author(s):  
Lorraine De Jesus Kim ◽  
Larry J Friedman ◽  
Christian Ramsoomair ◽  
Jeff Gelles ◽  
Stephen P Bell
Keyword(s):  
Single Molecule ◽  
Replication Origin ◽  
Molecular Mechanisms ◽  
Replication Initiation ◽  
Phosphorylation Sites ◽  
Dependent Manner ◽  
Multiplicity Results ◽  
Biochemical Assays ◽  
Eukaryotic Dna ◽  
Two Stages

The committed step of eukaryotic DNA replication occurs when the replicative Mcm2-7 helicase pairs that license each replication origin are activated. Helicase activation requires the recruitment of Cdc45 and GINS to Mcm2-7, forming Cdc45-Mcm2-7-GINS complexes (CMGs). Using single-molecule biochemical assays to monitor CMG formation, we found that Cdc45 and GINS are recruited to loaded Mcm2-7 in two stages. Initially, Cdc45 and GINS are individually recruited to unstructured Mcm2-7 N-terminal tails in a Dbf4-dependent kinase (DDK)-dependent manner, forming Cdc45-tail-GINS intermediates (CtGs). The multiple phosphorylation sites on the Mcm2-7 tails promote DDK-dependent modulation of the number of CtGs formed per Mcm2-7. In a second, inefficient event, a subset of CtGs transfer their Cdc45 and GINS components to form CMGs. Importantly, higher CtG multiplicity results in increased frequency of CMG formation. Our findings reveal molecular mechanisms sensitizing helicase activation to DDK levels with implications for the control of replication origin efficiency and timing.

scholarly journals The Role of PARPs in Inflammation—and Metabolic—Related Diseases: Molecular Mechanisms and Beyond

Cells ◽  
2019 ◽  
Vol 8 (9) ◽  
pp. 1047 ◽  
Author(s):  
Ke ◽  
Wang ◽  
Zhang ◽  
Zhong ◽  
Wang ◽  
...  
Keyword(s):  
Breast Cancer ◽  
Cardiovascular Disease ◽  
Ovarian Cancer ◽  
Molecular Mechanisms ◽  
Parp Inhibition ◽  
Biological Processes ◽  
Post Translational Modification ◽  
Cancer Breast ◽  
Promising Strategy

Poly(ADP-ribosyl)ation (PARylation) is an essential post-translational modification catalyzed by poly(ADP-ribose) polymerase (PARP) enzymes. Poly(ADP-ribose) polymerase 1 (PARP1) is a well-characterized member of the PARP family. PARP1 plays a crucial role in multiple biological processes and PARP1 activation contributes to the development of various inflammatory and malignant disorders, including lung inflammatory disorders, cardiovascular disease, ovarian cancer, breast cancer, and diabetes. In this review, we will focus on the role and molecular mechanisms of PARPs enzymes in inflammation- and metabolic-related diseases. Specifically, we discuss the molecular mechanisms and signaling pathways that PARP1 is associated with in the regulation of pathogenesis. Recently, increasing evidence suggests that PARP inhibition is a promising strategy for intervention of some diseases. Thus, our in-depth understanding of the mechanism of how PARPs are activated and how their signaling downstream effecters can provide more potential therapeutic targets for the treatment of the related diseases in the future is crucial.

scholarly journals The Anti-Neuroinflammatory Role of Anthocyanins and Their Metabolites for the Prevention and Treatment of Brain Disorders

2020 ◽  
Vol 21 (22) ◽  
pp. 8653
Author(s):  
Joana F. Henriques ◽  
Diana Serra ◽  
Teresa C. P. Dinis ◽  
Leonor M. Almeida
Keyword(s):  
Neurological Disorders ◽  
Fruits And Vegetables ◽  
Molecular Mechanisms ◽  
Brain Inflammation ◽  
Brain Diseases ◽  
Naturally Occurring ◽  
Pathological Conditions ◽  
Promising Strategy ◽  
Prevention And Treatment

Anthocyanins are naturally occurring polyphenols commonly found in fruits and vegetables. Numerous studies have described that anthocyanin-rich foods may play a crucial role in the prevention and treatment of different pathological conditions, which have encouraged their consumption around the world. Anthocyanins exhibit a significant neuroprotective role, mainly due to their well-recognized antioxidant and anti-inflammatory properties. Neuroinflammation is an intricate process relevant in both homeostatic and pathological circumstances. Since the progression of several neurological disorders relies on neuroinflammatory process, targeting brain inflammation has been considered a promising strategy in those conditions. Recent data have shown the anti-neuroinflammatory abilities of many anthocyanins and of their metabolites in the onset and development of several neurological disorders. In this review, it will be discussed the importance and the applicability of these polyphenolic compounds as neuroprotective agents and it will be also scrutinized the molecular mechanisms underlying the modulation of neuroinflammation by these natural compounds in the context of several brain diseases.

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