bims-polyam 2022-07-17 papers

Issue of 2022–07–17
six papers selected by
Sebastian J. Hofer, University of Graz

Sci Rep. 2022 Jul 12. 12(1): 11804

Difluoromethylornithine (DFMO) and AMXT 1501 inhibit capsule biosynthesis in pneumococci.

Moses B Ayoola, Leslie A Shack, Jung Hwa Lee, Juhyeon Lim, Hyungjin Eoh, Edwin Swiatlo, Otto Phanstiel, Bindu Nanduri.

Polyamines are small cationic molecules that have been linked to various cellular processes including replication, translation, stress response and recently, capsule regulation in Streptococcus pneumoniae (Spn, pneumococcus). Pneumococcal-associated diseases such as pneumonia, meningitis, and sepsis are some of the leading causes of death worldwide and capsule remains the principal virulence factor of this versatile pathogen. α-Difluoromethyl-ornithine (DFMO) is an irreversible inhibitor of the polyamine biosynthesis pathway catalyzed by ornithine decarboxylase and has a long history in modulating cell growth, polyamine levels, and disease outcomes in eukaryotic systems. Recent evidence shows that DFMO can also target arginine decarboxylation. Interestingly, DFMO-treated cells often escape polyamine depletion via increased polyamine uptake from extracellular sources. Here, we examined the potential capsule-crippling ability of DFMO and the possible synergistic effects of the polyamine transport inhibitor, AMXT 1501, on pneumococci. We characterized the changes in pneumococcal metabolites in response to DFMO and AMXT 1501, and also measured the impact of DFMO on amino acid decarboxylase activities. Our findings show that DFMO inhibited pneumococcal polyamine and capsule biosynthesis as well as decarboxylase activities, albeit, at a high concentration. AMXT 1501 at physiologically relevant concentration could inhibit both polyamine and capsule biosynthesis, however, in a serotype-dependent manner. In summary, this study demonstrates the utility of targeting polyamine biosynthesis and transport for pneumococcal capsule inhibition. Since targeting capsule biosynthesis is a promising way for the eradication of the diverse and pathogenic pneumococcal strains, future work will identify small molecules similar to DFMO/AMXT 1501, which act in a serotype-independent manner.

DOI: https://doi.org/10.1038/s41598-022-16007-7

World J Microbiol Biotechnol. 2022 Jul 14. 38(9): 159

Elucidating the dialogue between arbuscular mycorrhizal fungi and polyamines in plants.

Sheng-Min Liang, Feng-Ling Zheng, Qiang-Sheng Wu.

The most dominant arbuscular mycorrhizal (AM) symbiont can be established on roots of most terrestrial plants by beneficial AM fungi. A type of polycationic and aliphatic compounds, polyamines (PAs), are involved in plant physiological activities including stress responses. Interestingly, small amounts of PAs such as putrescine (Put) and spermidine (Spd) were found in AM fungal spores, and they are considered to be a component involved in mycorrhizal development, including mycorrhizal colonization, appressoria formation, spore germination and mycelial growth. Thus, PAs are regulatory factors in plant-AM symbiosis. Inoculation of AM fungi also affects the metabolism of endogenous PAs in host plants, including PAs synthesis and catabolism, thus, regulating various physiological events of the host. As a result, there seems to be a dialogue between PAs and AM fungi. Existing knowledge makes us understand that endogenous or exogenous PAs are an important regulator factor in the growth of AM fungi, as well as a key substance to colonize roots, which further enhances mycorrhizal benefits in plant growth responses and root architecture. The presence of AM symbiosis in roots alters the dynamic balance of endogenous PAs, triggering osmotic adjustment and antioxidant defense systems, maintaining charge balance and acting as a stress signalling molecule, which affects various physiological activities, such as plant growth, nutrient acquisition, stress tolerance and improvement of root architecture. This review mainly elucidated (i) what is the role of fungal endogenous PAs in fungal growth and colonization of roots in host plants? (ii) how AM fungi and PAs interact with each other to alter the growth of fungi and plants and subsequent activities, providing the reference for the future combined use of AM fungi and PAs in agricultural production, although there are still many unknown events in the dialogue.

Keywords: Hormone; Mycorrhiza; Putrescine; Spermidine; Spermine; Symbiosis

DOI: https://doi.org/10.1007/s11274-022-03336-y

Med Chem. 2022 Jul 13.

Promising molecular targets related to polyamine biosynthesis in drug discovery against leishmaniasis.

Kaio M Santiago-Silva, Priscila G Camargo, Marcelle L F Bispo.

Leishmaniasis is a neglected tropical disease widely distributed worldwide, caused by parasitic protozoa of the genus Leishmania. Despite representing a significant public health problem, the therapeutic options are old, with several reported adverse effects, have high costs, with administration mainly by parenteral route, which makes treatment difficult, increasing dropout and, consequently, the emergence of resistant strains. Thus, the research and development of new antileishmanial therapies become necessary. In this field, inhibiting essential targets that affect the parasite's growth, survival, and infectivity represents an attractive therapeutic strategy. With this in mind, this review addresses the main structural, functional characteristics and recent reports of the discovery of promising inhibitors of the enzymes arginase (ARG) and trypanothione synthase (TryS), which are involved in the biosynthesis of polyamines and trypanothione and trypanothione reductase (TR), responsible for the reduction of trypanothione thiol.

Keywords: Arginase; leishmaniasis; polyamines; trypanothione reductase.; trypanothione synthase

DOI: https://doi.org/10.2174/1573406418666220713145446

Biomater Adv. 2022 May;pii: 212755. [Epub ahead of print]136

Hyaluronate-coated perfluoroalkyl polyamine prodrugs as bioactive siRNA delivery systems for the treatment of peritoneal cancers.

Ao Yu, Siyuan Tang, Ling Ding, Jackson Foley, Weimin Tang, Huizhen Jia, Sudipta Panja, Cassandra E Holbert, Yu Hang, Tracy Murray Stewart, Lynette M Smith, Diptesh Sil, Robert A Casero, David Oupický.

RNA interference (RNAi) is an emerging therapeutic modality for cancer, which remains in critical need of effective delivery vectors due to the unfavorable biopharmaceutical properties of small RNAs. Polyamines are essential for functioning of mammalian cells. Dysregulated polyamine metabolism is found in many cancers and has been an attractive therapeutic target in combination therapies. Combination therapies based on drugs that affect polyamine metabolism and nucleic acids promise to enhance anticancer activity due to a cooperative effect on multiple oncogenic pathways. Here, we report bioactive polycationic prodrug (F-PaP) based on an anticancer polyamine analog bisethylnorspermine (BENSpm) modified with perfluoroalkyl moieties. Following encapsulation of siRNA, F-PaP/siRNA nanoparticles were coated with hyaluronic acid (HA) to form ternary nanoparticles HA@F-PaP/siRNA. The presence of perfluoroalkyl moieties and HA reduced cell membrane toxicity and improved stability of the particles with cooperatively enhanced siRNA delivery in pancreatic and colon cancer cell lines. We then tested a therapeutic hypothesis that combining BENSpm with siRNA silencing of polo-like kinase 1 (PLK1) would result in cooperative cancer cell killing. HA@F-PaP/siPLK1 induced polyamine catabolism and cell cycle arrest, leading to enhanced apoptosis in the tested cell lines. The HA-coated nanoparticles facilitated tumor accumulation and contributed to strong tumor inhibition and favorable modulation of the immune tumor microenvironment in orthotopic pancreatic cancer model. Combination anticancer therapy with polyamine prodrug-mediated delivery of siRNA. Hyaluronate coating of the siRNA nanoparticles facilitates selective accumulation in orthotopic pancreatic tumors. Perfluoroalkyl conjugation reduces toxicity and improves gene silencing effect. Nanoparticle treatment induces polyamine catabolism and cell cycle arrest leading to strong tumor inhibition and favorable modulation of immune tumor microenvironment.

Keywords: combination cancer therapy; hyaluronic acid; perfluoroalkyls; polyamines; siRNA delivery

DOI: https://doi.org/10.1016/j.bioadv.2022.212755

Brief Funct Genomics. 2022 Jul 09. pii: elac014. [Epub ahead of print]

Biophysical and modeling-based approach for the identification of inhibitors against DOHH from Leishmania donovani.

Madhusudhanarao Katiki, Monica Sharma, Neetu Neetu, Madhubala Rentala, Pravindra Kumar.

The amino acid hypusine (Nε-4-amino-2-hydroxybutyl(lysine)) occurs only in isoforms of eukaryotic translation factor 5A (eIF5A) and has a role in initiating protein translation. Hypusinated eIF5A promotes translation and modulates mitochondrial function and oxygen consumption rates. The hypusination of eIF5A involves two enzymes, deoxyhypusine synthase and deoxyhypusine hydroxylase (DOHH). DOHH is the second enzyme that completes the synthesis of hypusine and the maturation of eIF5A. Our current study aims to identify inhibitors against DOHH from Leishmania donovani (LdDOHH), an intracellular protozoan parasite causing Leishmaniasis in humans. The LdDOHH protein was produced heterologously in Escherichia coli BL21(DE3) cells and characterized biochemically. The three-dimensional structure was predicted, and the compounds folic acid, scutellarin and homoarbutin were selected as top hits in virtual screening. These compounds were observed to bind in the active site of LdDOHH stabilizing the structure by making hydrogen bonds in the active site, as observed by the docking and molecular dynamics simulation studies. These results pave the path for further investigation of these molecules for their anti-leishmanial activities.

Keywords: Leishmania donovani ; Leishmaniasis; MD simulation; MPBSA; phytochemicals

DOI: https://doi.org/10.1093/bfgp/elac014

EMBO J. 2022 Jul 13. e110581

Molecular architecture of 40S translation initiation complexes on the hepatitis C virus IRES.

Zuben P Brown, Irina S Abaeva, Swastik De, Christopher U T Hellen, Tatyana V Pestova, Joachim Frank.

Hepatitis C virus mRNA contains an internal ribosome entry site (IRES) that mediates end-independent translation initiation, requiring a subset of eukaryotic initiation factors (eIFs). Biochemical studies revealed that direct binding of the IRES to the 40S ribosomal subunit places the initiation codon into the P site, where it base pairs with eIF2-bound Met-tRNAiMet forming a 48S initiation complex. Subsequently, eIF5 and eIF5B mediate subunit joining, yielding an elongation-competent 80S ribosome. Initiation can also proceed without eIF2, in which case Met-tRNAiMet is recruited directly by eIF5B. However, the structures of initiation complexes assembled on the HCV IRES, the transitions between different states, and the accompanying conformational changes have remained unknown. To fill these gaps, we now obtained cryo-EM structures of IRES initiation complexes, at resolutions up to 3.5 Å, that cover all major stages from the initial ribosomal association, through eIF2-containing 48S initiation complexes, to eIF5B-containing complexes immediately prior to subunit joining. These structures provide insights into the dynamic network of 40S/IRES contacts, highlight the role of IRES domain II, and reveal conformational changes that occur during the transition from eIF2- to eIF5B-containing 48S complexes and prepare them for subunit joining.

Keywords: eIF2; eIF5B; hepatitis C virus IRES; ribosome; translation initiation

DOI: https://doi.org/10.15252/embj.2022110581