bims-polyam 2021-01-31 papers

Issue of 2021‒01‒31
five papers selected by
Sebastian J. Hofer
University of Graz

Front Plant Sci. 2020 ;11 600792

Arbuscular Mycorrhizal Fungi Regulate Polyamine Homeostasis in Roots of Trifoliate Orange for Improved Adaptation to Soil Moisture Deficit Stress.

Ying-Ning Zou, Fei Zhang, Anoop K Srivastava, Qiang-Sheng Wu, Kamil Kuča.

Soil arbuscular mycorrhizal fungi (AMF) enhance the tolerance of plants against soil moisture deficit stress (SMDS), but the underlying mechanisms are still not fully understood. Polyamines (PAs) as low-molecular-weight, aliphatic polycations have strong roles in abiotic stress tolerance of plants. We aimed to investigate the effect of AMF (Funneliformis mosseae) inoculation on PAs, PA precursors, activities of PA synthases and degrading enzymes, and concentration of reactive oxygen species in the roots of trifoliate orange (Poncirus trifoliata) subjected to 15 days of SMDS. Leaf water potential and total chlorophyll levels were comparatively higher in AMF-inoculated than in non-AMF-treated plants exposed to SMDS. Mycorrhizal plants recorded a significantly higher concentration of precursors of PA synthesis such as L-ornithine, agmatine, and S-adenosyl methionine, besides higher putrescine and cadaverine and lower spermidine during the 15 days of SMDS. AMF colonization raised the PA synthase (arginine decarboxylase, ornithine decarboxylase, spermidine synthase, and spermine synthase) activities and PA-degrading enzymes (copper-containing diamine oxidase and FAD-containing polyamine oxidase) in response to SMDS. However, mycorrhizal plants showed a relatively lower degree of membrane lipid peroxidation, superoxide anion free radical, and hydrogen peroxide than non-mycorrhizal plants, whereas the difference between them increased linearly up to 15 days of SMDS. Our study concluded that AMF regulated PA homeostasis in roots of trifoliate orange to tolerate SMDS.

Keywords: Poncirus trifoliata; citrus; mycorrhiza; polyamine; water deficit

DOI: https://doi.org/10.3389/fpls.2020.600792

Turk J Chem. 2020 ;44(3): 817-832

Comparative modelling of a novel enzyme: Mus musculus leucine decarboxylase.

Arif Sercan ŞahutoĞlu.

Leucine decarboxylase (LDC) is a recently proposed enzyme with no official enzyme commission number yet. It is encoded by the Mus musculus gene Gm853 which is expressed at kidneys, generating isopentylamine, an alkylmonoamine that has not been described to be formed by any metazoan enzyme yet. Although the relevance of LDC in mammalian physiology has not been fully determined, isopentylamine is a potential modulator which may have effects on insulin secretion and healthy gut microbiota formation. The LDC is a stable enzyme that specifically decarboxylates L-leucine but does not decarboxylate ornithine or lysine as its paralogues ornithine decarboxylase (ODC; EC: 4.1.1.17) and lysine decarboxylase (KDC; EC: 4.1.1.18) do. It does not act as an antizyme inhibitor and does not decarboxylate branched amino acids such as valine and isoleucine as it is another paralogue valine decarboxylase (VDC; EC: 4.1.1.14). The crystal structure of the enzyme has not been determined yet but there are homologous structures with complete coverage in Protein Data Bank (PDB) which makes LDC a good candidate for comparative modelling.In this study, homology models of LDC were generated and used in cofactor and substrate docking to understand the structure/function relationship underlying the unique selectivity of LDC enzyme.

Keywords: Gm853; Homology modelling; isopentylamine; leucine decarboxylase; ornithine decarboxylase

DOI: https://doi.org/10.3906/kim-2003-63

Cell Biochem Funct. 2021 Jan 25.

Spermidine promotes melanin production through an MITF signalling pathway.

Seong-Hee Kang, Moon-Moo Kim.

Melanin plays an important role in determining skin colour. Apoptosis of melanocytes and defect in melanin production cause vitiligo. Various studies have been conducted to treat the disease, but its treatment is still difficult. Therefore, this study aimed to investigate the effect of spermidine, which is known as an inhibitor of ageing-related oxidized proteins, on melanogenesis. Even though spermidine above 50 μM had no effect on antioxidant activity and DOPA oxidation, it displayed tyrosinase activity. However, spermidine at 2000 μM was cytotoxic in B16F1 cells using MTT assay. Spermidine above 125 μM decreased the amount of intracellular hydrogen peroxide in a concentration-dependent manner in DCFH-DA analysis. It was also found that spermidine above 2000 μM increased melanin synthesis in living cells. However, spermidine above 1000 μM increased melanin synthesis in a concentration-dependent manner in H2 O2 -treated B16F1 cells. Furthermore, spermidine enhanced the expression of tyrosine hydroxylase via MITF transcription factor involved in melanogenesis in H2 O2 -treated B16F1 cells. Therefore, these results suggest that spermidine could be applied as a potential stimulator of melanin synthesis for the prevention of hair greying.

Keywords: MITF; melanin; spermidine; tyrosine hydroxylase; α-MSH

DOI: https://doi.org/10.1002/cbf.3619

Microbiology (Reading). 2021 Jan 27.

A mutagenic screen reveals NspS residues important for regulation of Vibrio cholerae biofilm formation.

Erin C Young, Jackson T Baumgartner, Ece Karatan, Misty L Kuhn.

Biofilm formation in the human intestinal pathogen Vibrio cholerae is in part regulated by norspermidine, spermidine and spermine. V. cholerae senses these polyamines through a signalling pathway consisting of the periplasmic protein, NspS, and the integral membrane c-di-GMP phosphodiesterase MbaA. NspS and MbaA belong to a proposed class of novel signalling systems composed of periplasmic ligand-binding proteins and membrane-bound c-di-GMP phosphodiesterases containing both GGDEF and EAL domains. In this signal transduction pathway, NspS is hypothesized to interact with MbaA in the periplasm to regulate its phosphodiesterase activity. Polyamine binding to NspS likely alters this interaction, leading to the activation or inhibition of biofilm formation depending on the polyamine. The purpose of this study was to determine the amino acids important for NspS function. We performed random mutagenesis of the nspS gene, identified mutant clones deficient in biofilm formation, determined their responsiveness to norspermidine and mapped the location of these residues onto NspS homology models. Single mutants clustered on two lobes of the NspS model, but the majority were found on a single lobe that appeared to be more mobile upon norspermidine binding. We also identified residues in the putative ligand-binding site that may be important for norspermidine binding and interactions with MbaA. Ultimately, our results provide new insights into this novel signalling pathway in V. cholerae and highlight differences between periplasmic binding proteins involved in transport versus signal transduction.

Keywords: Vibrio cholerae; biofilm; homology modelling; norspermidine; polyamine

DOI: https://doi.org/10.1099/mic.0.001023

Br J Pharmacol. 2021 Jan 29.

Synergistic beneficial effects of natural activators of autophagy on endothelial cells and platelets.

Roberto Carnevale, Cristina Nocella, Sonia Schiavon, Vittoria Cammisotto, Maria Cotugno, Maurizio Forte, Valentina Valenti, Simona Marchitti, Daniele Vecchio, Giuseppe Biondi Zoccai, Speranza Rubattu, Ombretta Martinelli, Pasquale Pignatelli, Francesco Violi, Massimo Volpe, Francesco Versaci, Luigi Frati, Giacomo Frati, Sebastiano Sciarretta.

BACKGROUND AND PURPOSE: Oxidative stress and insufficient autophagy activity are associated with inflammatory processes and are common features of many cardiovascular diseases (CVD). We investigated if a combination of natural activators of autophagy is able to modulate oxidative stress, platelet aggregation and endothelial cell survival and function in response to stress.EXPERIMENTAL APPROACH: Ex vivo platelet aggregation and activation, H2 O2 production and autophagy were measured in platelets of subjects at high cardiovascular risk, including smokers, patients with metabolic syndrome (MS) and patients with atrial fibrillation (AF). In vitro, the effects of a mixture of natural pro-autophagy molecules and antioxidants on platelets and HUVECs were evaluated.
KEY RESULT: Autophagy appeared to be inhibited, whereas aggregation was increased in platelets from AF and MS patients and in smokers, as compared to healthy subjects. Treatment of platelets isolated from these patients with 2 different mixtures of catechin, epicatechin, trehalose and spermidine significantly reduced platelet activation and oxidative stress, whereas they increased autophagy in a synergistic manner with respect to the effect of each single molecule alone. Similarly, treatment of HUVECs with a combination of these natural compounds exerted synergic beneficial effects and increased endothelial cell survival, NO bioavailability and angiogenesis in response to stress in a potentiated manner.
CONCLUSION AND IMPLICATIONS: A combination of natural activators of autophagy could synergistically inhibit platelet activity and oxidative stress and improve endothelial cell survival and function in a potentiated manner representing a useful strategy to reduce the impact of risk factors on CVD occurrence.

Keywords: autophagy; cardiovascular diseases; endothelial cells; oxidative stress; platelets

DOI: https://doi.org/10.1111/bph.15399