bims-polyam 2020-04-05 papers

Issue of 2020‒04‒05
six papers selected by
Alexander Ivanov
Engelhardt Institute of Molecular Biology

Biomolecules. 2020 Mar 30. pii: E522. [Epub ahead of print]10(4):

Half Way to Hypusine-Structural Basis for Substrate Recognition by Human Deoxyhypusine Synthase.

Elżbieta Wątor, Piotr Wilk, Przemysław Grudnik.

Deoxyhypusine synthase (DHS) is a transferase enabling the formation of deoxyhypusine, which is the first, rate-limiting step of a unique post-translational modification: hypusination. DHS catalyses the transfer of a 4-aminobutyl moiety of polyamine spermidine to a specific lysine of eukaryotic translation factor 5A (eIF5A) precursor in a nicotinamide adenine dinucleotide (NAD)-dependent manner. This modification occurs exclusively on one protein, eIF5A, and it is essential for cell proliferation. Malfunctions of the hypusination pathway, including those caused by mutations within the DHS encoding gene, are associated with conditions such as cancer or neurodegeneration. Here, we present a series of high-resolution crystal structures of human DHS. Structures were determined as the apoprotein, as well as ligand-bound states at high-resolutions ranging from 1.41 to 1.69 Å. By solving DHS in complex with its natural substrate spermidine (SPD), we identified the mode of substrate recognition. We also observed that other polyamines, namely spermine (SPM) and putrescine, bind DHS in a similar manner as SPD. Moreover, we performed activity assays showing that SPM could to some extent serve as an alternative DHS substrate. In contrast to previous studies, we demonstrate that no conformational changes occur in the DHS structure upon spermidine-binding. By combining mutagenesis and a light-scattering approach, we show that a conserved "ball-and-chain" motif is indispensable to assembling a functional DHS tetramer. Our study substantially advances our knowledge of the substrate recognition mechanism by DHS and may aid the design of pharmacological compounds for potential applications in cancer therapy.

Keywords: EIF5A; deoxyhypusine synthase; hypusination; hypusine; polyamines; post-translational modification; putrescine; spermidine; spermine; translation

DOI: https://doi.org/10.3390/biom10040522

Int J Mol Sci. 2020 Mar 31. pii: E2406. [Epub ahead of print]21(7):

Cytotoxic Mechanism of Excess Polyamines Functions through Translational Repression of Specific Proteins Encoded by Polyamine Modulon.

Akihiko Sakamoto, Junpei Sahara, Gota Kawai, Kaneyoshi Yamamoto, Akira Ishihama, Takeshi Uemura, Kazuei Igarashi, Keiko Kashiwagi, Yusuke Terui.

Excessive accumulation of polyamines causes cytotoxicity, including inhibition of cell growth and a decrease in viability. We investigated the mechanism of cytotoxicity caused by spermidine accumulation under various conditions using an Escherichia coli strain deficient in spermidine acetyltransferase (SAT), a key catabolic enzyme in controlling polyamine levels. Due to the excessive accumulation of polyamines by the addition of exogenous spermidine to the growth medium, cell growth and viability were markedly decreased through translational repression of specific proteins [RMF (ribosome modulation factor) and Fis (rRNA transcription factor) etc.] encoded by members of polyamine modulon, which are essential for cell growth and viability. In particular, synthesis of proteins that have unusual locations of the Shine-Dalgarno (SD) sequence in their mRNAs was inhibited. In order to elucidate the molecular mechanism of cytotoxicity by the excessive accumulation of spermidine, the spermidine-dependent structural change of the bulged-out region in the mRNA at the initiation site of the rmf mRNA was examined using NMR analysis. It was suggested that the structure of the mRNA bulged-out region is affected by excess spermidine, so the SD sequence of the rmf mRNA cannot approach initiation codon AUG.

Keywords: cell growth; cell viability; cytotoxicity; polyamine modulon; polyamines; spermidine

DOI: https://doi.org/10.3390/ijms21072406

Plants (Basel). 2020 Mar 31. pii: E426. [Epub ahead of print]9(4):

Citrus Polyamines: Structure, Biosynthesis, and Physiological Functions.

Nabil Killiny, Yasser Nehela.

Polyamines (PAs) are ubiquitous biogenic amines found in all living organisms from bacteria to Archaea, and Eukaryotes including plants and animals. Since the first description of putrescine conjugate, feruloyl-putrescine (originally called subaphylline), from grapefruit leaves and juice, many research studies have highlighted the importance of PAs in growth, development, and other physiological processes in citrus plants. PAs appear to be involved in a wide range of physiological processes in citrus plants; however, their exact roles are not fully understood. Accordingly, in the present review, we discuss the biosynthesis of PAs in citrus plants, with an emphasis on the recent advances in identifying and characterizing PAs-biosynthetic genes and other upstream regulatory genes involved in transcriptional regulation of PAs metabolism. In addition, we will discuss the recent metabolic, genetic, and molecular evidence illustrating the roles of PAs metabolism in citrus physiology including somatic embryogenesis; root system formation, morphology, and architecture; plant growth and shoot system architecture; inflorescence, flowering, and flowering-associated events; fruit set, development, and quality; stomatal closure and gas-exchange; and chlorophyll fluorescence and photosynthesis. We believe that the molecular and biochemical understanding of PAs metabolism and their physiological roles in citrus plants will help citrus breeding programs to enhance tolerance to biotic and abiotic stresses and provide bases for further research into potential applications.

Keywords: citrus; embryogenesis; flowering and inflorescence; polyamines; putrescine; root system architecture; shoot system architecture; spermidine; spermine

DOI: https://doi.org/10.3390/plants9040426

Am J Clin Nutr. 2020 Apr 04. pii: nqaa064. [Epub ahead of print]

Effect of a lifestyle intervention program with energy-restricted Mediterranean diet and exercise on the serum polyamine metabolome in individuals at high cardiovascular disease risk: a randomized clinical trial.

José C Fernández-García, María A Martínez-Sánchez, María R Bernal-López, Araceli Muñoz-Garach, Miguel A Martínez-González, Montse Fitó, Jordi Salas-Salvadó, Francisco J Tinahones, Bruno Ramos-Molina.

BACKGROUND: Many food items included in the Mediterranean diet (MedDiet) are rich in polyamines, small aliphatic amines with potential cardioprotective effects. The consumption of a MedDiet could increase polyamine concentrations. Based on experimental models, polyamine concentrations may be also influenced by physical activity (PA).OBJECTIVES: We aimed to evaluate whether an intervention based on an energy-restricted MedDiet (er-MedDiet) and PA promotion, in comparison with an energy-unrestricted MedDiet and traditional health care, influences the serum pattern of polyamines and related metabolites in subjects at high risk of cardiovascular disease (CVD).
METHODS: This was a substudy from the PREDIMED-Plus trial, an ongoing randomized clinical trial including 6874 participants allocated either to an intensive weight-loss lifestyle intervention based on er-MedDiet, PA promotion, and behavioral support (er-MedDiet + PA group), or to an energy-unrestricted MedDiet and traditional health care group (MedDiet group). A total of 75 patients (n = 38, er-MedDiet + PA group; n = 37, MedDiet group) were included in this study. Serum concentrations of arginine, ornithine, polyamines, and acetyl polyamines at baseline and 26 wk of intervention were measured by an ultra-high-performance LC-tandem MS platform.
RESULTS: At week 26, study groups had similar adherence to the MedDiet but patients randomly assigned to the er-MedDiet + PA group showed significantly lower mean energy intake (-340.3 kcal/d; 95% CI: -567.3, -113.4 kcal/d; P = 0.004), higher mean PA (1290.6; 95% CI: 39.9, 2541.3 metabolic equivalent tasks · min/d; P = 0.043), and higher mean decrease in BMI (in kg/m2) (-1.3; 95% CI: -1.8, -0.6; P < 0.001) than the MedDiet group. However, no significant differences in serum polyamines or related metabolites were found between study groups after 26 wk of intervention and no significant between-group differences were found in glycated hemoglobin, HDL-cholesterol, or triglyceride concentrations.
CONCLUSIONS: In individuals at high CVD risk, an er-MedDiet with increased PA did not result in significant changes of serum concentrations of polyamines or related metabolites in comparison with an energy-unrestricted MedDiet and no increase in PA. This trial was registered at isrctn.com as ISRCTN89898870.

Keywords: Mediterranean diet; metabolic syndrome; metabolomics; nutrition; obesity; polyamines

DOI: https://doi.org/10.1093/ajcn/nqaa064

Redox Biol. 2020 Mar 21. pii: S2213-2317(19)31549-6. [Epub ahead of print]32 101514

Exogenous spermine attenuates rat diabetic cardiomyopathy via suppressing ROS-p53 mediated downregulation of calcium-sensitive receptor.

Yuehong Wang, Junting Chen, Siwei Li, Xinying Zhang, Zuoming Guo, Jing Hu, Xiaoting Shao, Ningyang Song, Yajun Zhao, Hongzhu Li, Guangdong Yang, Changqing Xu, Can Wei.

Diabetic cardiomyopathy (DCM) is a severe complication of type 1 diabetic (T1D) patients, manifested as combined diastolic and systolic dysfunction. DCM is associated with impaired calcium homeostasis secondary to decreased calcium-sensitive receptor (CaSR) expression. Spermine, a direct agonist of CaSR, was found deficient in cardiomyocytes of T1D rats. However, the role of spermine in DCM was unclear. Here, we examined the cardioprotective effect of exogenous spermine on DCM in streptozotocin (STZ) induced-T1D rats and high-glucose (HG)-incubated neonatal rat cardiomyocytes. Exogenous spermine significantly attenuated cardiac dysfunction in T1D rats, characterized by improved echocardiography, less fibrosis, reduced myocardial endoplasmic reticulum (ER) stress and oxidative stress, and increased expression of myocardial membrane CaSR. In cultured neonatal rat cardiomyocytes, exogenous spermine attenuated myocardial injury induced by HG treatment, demonstrated by restored cellular glucose uptake capacity, reduced expression of apoptotic markers, lowered level of oxidative stress, ER stress and unfolded protein response, and upregulated cell membrane CaSR. Mechanistically, the cardioprotective effect of spermine appeared dependent upon effective elimination of reactive oxygen species (ROS) and up-regulation of CaSR expression by suppressing the Nrf2-ROS-p53-MuRF1 axis. Taken together, these results suggest that exogenous spermine protects against DCM in vivo and in vitro, partially via suppressing ROS and p53-mediated downregulation of cell membrane CaSR.

Keywords: Calcium sensitive receptor; Diabetic cardiomyopathy; ER stress; Nrf2-ROS-p53-MuRF1 axis; Spermine; Unfolded protein response

DOI: https://doi.org/10.1016/j.redox.2020.101514

Biochem Biophys Res Commun. 2020 Mar 26. pii: S0006-291X(20)30533-7. [Epub ahead of print]

Constitutive activity of a spermine receptor is maintained by a single site in the C-terminal.

Zhe Zhang, Xiang Gao, Qinghua Zhang, Weming Li.

Olfactory receptors are G-protein coupled receptors (GPCRs) that enable olfactory epithelia to detect odorants. These GPCRs may also show constitutive activity, which play important roles in the development and responses of odorant receptor neurons. However, little is known about the molecular characteristics that support the constitutive activities in olfactory receptors. Here, we characterize a pair of olfactory receptor orthologs that show similar ligand-dependent activity but different levels of constitutive activity, and elucidate the molecular characteristics that maintain the constitutive activity. Previously, PmTAAR348, a sea lamprey (Petromyzon marinus) olfactory receptor that is activated by the male sex pheromone spermine has been reported. In this study, we identified LmTAAR348 of Northeast Chinese lamprey (Lethenteron morii) as an ortholog of PmTAAR348. When expressed in HEK293T cell lines, both receptors showed similar levels of activation when exposed to spermine. However, the constitutive activity of LmTAAR348 was 100-fold higher than that of PmTAAR348. Using site-directed mutagenesis, we screened all 13 amino acid residues (aa) that differed between the two orthologs and found that a switch in position 340 reversed the constitutive activity levels between LmTAAR348 and PmTAAR348. Mutating the remaining 12 aa did not affect the ligand-dependent or constitutive activation. Moreover, both the ligand-dependent and constitutive activation of TAAR348 are Golf (G protein ⍺ subunit olfactory type) independent. We conclude that a single aa in the C-terminal maintains the constitutive activity in a spermine receptor.

Keywords: Basal activity; G protein-coupled receptors; Lamprey; Site-directed mutagenesis; Spermine receptor

DOI: https://doi.org/10.1016/j.bbrc.2020.03.053