Polyamine Regulation Research Articles

Recent advances associated with cardiometabolic remodeling in diabetes-induced heart failure.

Diabetes mellitus (DM) is characterized by chronic hyperglycemia, and despite intensive glycemic control, the risk of heart failure in patients with diabetes remains high. Diabetes-induced heart failure (DHF) presents a unique metabolic challenge, driven by significant alterations in cardiac substrate metabolism, including increased reliance on fatty acid oxidation, reduced glucose utilization, and impaired mitochondrial function. These metabolic alterations lead to oxidative stress, lipotoxicity, and energy deficits, contributing to the progression of heart failure. Emerging research has identified novel mechanisms involved in the metabolic remodeling of diabetic hearts, such as autophagy dysregulation, epigenetic modifications, polyamine regulation, and branched-chain amino acid (BCAA) metabolism. These processes exacerbate mitochondrial dysfunction and metabolic inflexibility, further impairing cardiac function. Therapeutic interventions targeting these pathways-such as enhancing glucose oxidation, modulating fatty acid metabolism, and optimizing ketone body utilization-show promise in restoring metabolic homeostasis and improving cardiac outcomes. This review explores the key molecular mechanisms driving metabolic remodeling in diabetic hearts, highlights advanced methodologies, and presents the latest therapeutic strategies for mitigating the progression of DHF. Understanding these emerging pathways offers new opportunities to develop targeted therapies that address the root metabolic causes of heart failure in diabetes.

The role of polyamine metabolism in cellular function and physiology.

Polyamines are molecules with multiple amino groups that are essential for cellular function. The major polyamines are putrescine, spermidine, spermine, and cadaverine. Polyamines are important for posttranscriptional regulation, autophagy, programmed cell death, proliferation, redox homeostasis, and ion channel function. Their levels are tightly controlled. High levels of polyamines are associated with proliferative pathologies such as cancer, whereas low polyamine levels are observed in aging, and elevated polyamine turnover enhances oxidative stress. Polyamine metabolism is implicated in several pathophysiological processes in the nervous, immune, and cardiovascular systems. Currently, manipulating polyamine levels is under investigation as a potential preventive treatment for several pathologies, including aging, ischemia/reperfusion injury, pulmonary hypertension, and cancer. Although polyamines have been implicated in many intracellular mechanisms, our understanding of these processes remains incomplete and is a topic of ongoing investigation. Here, we discuss the regulation and cellular functions of polyamines, their role in physiology and pathology, and emphasize the current gaps in knowledge and potential future research directions.

Polyamine depletion enhances oil body mobilization through possible regulation of oleosin degradation and aquaporin abundance on its membrane

ABSTRACT Oil body (OB) mobilization, a crucial event associated with early seedling growth, is delayed in response to salt stress. Previous reports suggest that careful regulation of polyamine (PA) metabolism is essential for salt stress tolerance in plants. Many aspects of PA-mediated regulation of metabolism have been uncovered. However, their role in the process of OB mobilization remains unexplored. Interestingly, the present investigations reveal a possible influence of PA homeostasis on OB mobilization, while implicating complex regulation of oleosin degradation and aquaporin abundance in OB membranes in the process. Application of PA inhibitors resulted in the accumulation of smaller OBs when compared to control (−NaCl) and the salt-stressed counterparts, suggesting a faster rate of mobilization. PA deficit also resulted in reduced retention of some larger oleosins under controlled conditions but enhanced retention of all oleosins under salt stress. Additionally, with respect to aquaporins, a higher abundance of PIP2 under PA deficit both under control and saline conditions, is correlated with a faster mobilization of OBs. Contrarily, TIP1s, and TIP2s remained almost undetectable in response to PA depletion and were differentially regulated by salt stress. The present work, thus, provides novel insights into PA homeostasis-mediated regulation of OB mobilization, oleosin degradation, and aquaporin abundance on OB membranes.

β-N-Methylamino-L-Alanine (BMAA) Modulates the Sympathetic Regulation and Homeostasis of Polyamines.

The neurotoxin β-N-methylamino-L-alanine (BMAA) is a non-proteinogenic amino acid produced by cyanobacteria. Non-neuronal toxicity of BMAA is poorly studied with a reported increase in reactive oxygen species and a decrease in the antioxidant capacity of liver, kidney, and colorectal adenocarcinoma cells. The aim of this research is to study the toxicity of BMAA (0.1-1 mM) on mitochondria and submitochondrial particles with ATPase activity, on the semicarbazide-sensitive amino oxidases (SSAOs) activity of rat liver, and on an in vitro model containing functionally active excitable tissues-regularly contracting heart muscle preparation with a preserved autonomic innervation. For the first time the BMAA-dependent inhibition of SSAO activity, the elimination of the positive inotropic effect of adrenergic innervation, and the direct and reversible inhibition of adrenaline signaling in ventricular myocytes with 1 mM BMAA were observed. Additionally, it is confirmed that 1 mM BMAA can activate mitochondrial ATPase indirectly. It is concluded that a higher dose of BMAA may influence multiple physiological and pathological processes as it slows down the degradation of biogenic amines, downregulates the sympathetic neuromediation, and embarrasses the cell signaling of adrenergic receptors.

Identification of a polyamine-related signature and six novel prognostic biomarkers in oral squamous cell carcinoma.

Elevated polyamine levels are required for tumor transformation and development; however, expression patterns of polyamines and their diagnostic potential have not been investigated in oral squamous cell carcinoma (OSCC), and its impact on prognosis has yet to be determined. A total of 440 OSCC samples and clinical data were obtained from The Cancer Genome Atlas (TCGA) and Gene Expression Omnibus (GEO). Consensus clustering was conducted to classify OSCC patients into two subgroups based on the expression of the 17 polyamine regulators. Polyamine-related differentially expressed genes (PARDEGs) among distinct polyamine clusters were determined. To create a prognostic model, PARDEGs were examined in the training cohorts using univariate-Lasso-multivariate Cox regression analyses. Six prognostic genes, namely, "CKS2," "RIMS3," "TRAC," "FMOD," CALML5," and "SPINK7," were identified and applied to develop a predictive model for OSCC. According to the median risk score, the patients were split into high-risk and low-risk groups. The predictive performance of the six gene models was proven by the ROC curve analysis of the training and validation cohorts. Kaplan-Meier curves revealed that the high-risk group had poorer prognosis. Furthermore, the low-risk group was more susceptible to four chemotherapy drugs according to the IC50 of the samples computed by the "pRRophetic" package. The correlation between the risk scores and the proportion of immune cells was calculated. Meanwhile, the tumor mutational burden (TMB) value of the high-risk group was higher. Real-time quantitative polymerase chain reaction was applied to verify the genes constructing the model. The possible connections of the six genes with various immune cell infiltration and therapeutic markers were anticipated. In conclusion, we identified a polyamine-related prognostic signature, and six novel biomarkers in OSCC, which may provide insights to identify new treatment targets for OSCC.

Cation Homeostasis: Coordinate Regulation of Polyamine and Magnesium Levels in Salmonella.

Polyamines are organic cations that are important in all domains of life. Here, we show that in Salmonella, polyamine levels and Mg2+ levels are coordinately regulated and that this regulation is critical for viability under both low and high concentrations of polyamines. Upon Mg2+ starvation, polyamine synthesis is induced, as is the production of the high-affinity Mg2+ transporters MgtA and MgtB. Either polyamine synthesis or Mg2+ transport is required to maintain viability. Mutants lacking the polyamine exporter PaeA, the expression of which is induced by PhoPQ in response to low Mg2+, lose viability in the stationary phase. This lethality is suppressed by blocking either polyamine synthesis or Mg2+ transport, suggesting that once Mg2+ levels are reestablished, the excess polyamines must be excreted. Thus, it is the relative levels of both Mg2+ and polyamines that are regulated to maintain viability. Indeed, sensitivity to high concentrations of polyamines is proportional to the Mg2+ levels in the medium. These results are recapitulated during infection. Polyamine synthesis mutants are attenuated in a mouse model of systemic infection, as are strains lacking the MgtB Mg2+ transporter. The loss of MgtB in the synthesis mutant background confers a synthetic phenotype, confirming that Mg2+ and polyamines are required for the same process(es). Mutants lacking PaeA are also attenuated, but deleting paeA has no phenotype in a polyamine synthesis mutant background. These data support the idea that the cell coordinately controls both the polyamine and Mg2+ concentrations to maintain overall cation homeostasis, which is critical for survival in the macrophage phagosome. IMPORTANCE Polyamines are organic cations that are important in all life forms and are essential in plants and animals. However, their physiological functions and regulation remain poorly understood. We show that polyamines are critical for the adaptation of Salmonella to low Mg2+ conditions, including those found in the macrophage phagosome. Polyamines are synthesized upon low Mg2+ stress and partially replace Mg2+ until cytoplasmic Mg2+ levels are restored. Indeed, it is the sum of Mg2+ and polyamines in the cell that is critical for viability. While Mg2+ and polyamines compensate for one another, too little of both or too much of both is lethal. After cytoplasmic Mg2+ levels are reestablished, polyamines must be exported to avoid the toxic effects of excess divalent cations.

Brassinosteroids enhance resistance to manganese toxicity in Malus robusta Rehd. via modulating polyamines profile

Manganese (Mn) toxicity in soil is a widely observed phenomenon, which seriously restricts growth, quality, and yield of various crops and fruits including apples. However, mechanisms underlying the regulation of polyamines (PAs) by brassinosteroids (BRs) to improve tolerance to Mn stress are still unclear. In this study, we investigated the effects of 2,4-epibrassinolide (EBL; a BR) on the expression of genes involved in BR signaling pathway, Mn accumulation, PAs-mediated responses (PA precursor levels, metabolic enzymes, and genes), and growth parameters in Mn-stressed Malus robusta Rehd. EBL application significantly modulated the expressions of genes related to BR signaling (MdBRI, MdBSK, etc.) and reduced Mn accumulation, along with improving the rate of increase in root length and plant height, relative water content, chlorophyll content, maximum photochemical efficiency of PSII (Fv/Fm), and actual photochemical efficiency (ΦPSII) and decreasing electrical conductivity. Furthermore, EBL application significantly reduced putrescine (Put) accumulation and increased spermine (Spm) content and (Spd + Spm)/Put ratio. EBL weakened ornithine (Orn) pathway, decreased ornithine decarboxylase (ODC) activity, and increased biosynthesis of Spm from Put via elevating the PA oxidase (PAO) activity and expression of MdSPDS, MdSPMS, and MdPAO. The trends for free, PS-conjugated, and PIS-bound PAs were similar to that of total PAs, except that no significant change was observed in free Spm, PS-conjugated Spd, and Spm, as well as PIS-bound Spd. This study revealed that BR-regulated PAs help in mitigating Mn toxicity and clarified the mechanisms of regulation of PAs by BRs in apple trees.

Abstract 1354: Regulation and roles of polyamines in CD8+ T cell fate and function

Abstract CD8+ T cells play central roles in tumor immune surveillance and are major effectors in adoptive cell therapy (ACT). Thus, strategies that enhance their functions are an urgent clinical need. Metabolic reprogramming determines T cell fate and function, where glycolysis principally drives an effector phenotype while oxidative phosphorylation (OxPhos) drives T cell memory [1]. However, the roles of amino acid catabolism in controlling effector and memory CD8+ T cell fate and function are less well understood [1, 2]. Glutamine is essential for nucleotide biosynthesis and as an anaplerotic fuel source for the tricarboxylic acid (TCA) cycle. Isotope tracing experiments with 13C glutamine or 13C arginine revealed that glutamine is the major source of polyamines in activated CD8+ T cells. Further, activation of CD8+ T cells provokes marked increases in the expression and activity of enzymes that direct polyamine biosynthesis, specifically ornithine decarboxylase (Odc), spermidine synthase (Srm) and spermine synthase (Sms), as well as to increases in the polyamines putrescine, spermidine and spermine. Notably, pharmacologic inhibition of Odc using difluoromethylornithine (DFMO), or genetic deletion of Odc using CD8+ T cells from CD4-Cre;Odcfl/fl mice, augments cytokine production in activated CD8+ T cells, including IFN-γ, TNF-α and granzyme B. Further, metabolic flux analysis indicates that DFMO treatment switches the metabolism of activated CD8+ T cells to rely on OxPhos, a phenotype found in CD8+ tissue resident memory (TRM) cells that play key roles in tissue and anti-tumor immunity anti-tumor reactivity. Indeed, inhibition or loss of Odc augments other TRM phenotypes, including increases in CD69high;CD44high;S1PR1low;CD62Llow cells that define the TRM phenotype. In addition, ACT of DFMO treated CD8+ T cells augments their survival in vivo and augments the generation of CD69+CD103+CD69+CXCR6+ and Ly6C+ TRMs in the bone marrow. Finally, DFMO treatment enhances IFN-γ and TNF-α production in human TILs, and co-treatment with TGF-β polarizes TILs into CD69+CD103+ and CD69+CD49a+ TRM-like cells. We conclude that polyamines are a metabolic check point in CD8+ TRM generation and are an actionable target to improve the anti-tumor immunity of T-cell based immunotherapies. Citation Format: Aya G. Elmarsafawi, Rebecca S. Hesterberg, John L. Cleveland. Regulation and roles of polyamines in CD8+ T cell fate and function [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 1354.

Novel Chemical Probes targeting the Polyamine Regulatory Circuit

Polyamines are vital for cellular life. Polyamines such as putrescine, spermidine, and spermine regulate the essential cellular process, including gene expression and cell proliferation. Given its cellular role, polyamine concentration in cells is tightly controlled. However, aberrant polyamine metabolism is associated with numerous diseases, including cancer. Growing evidence suggests that elevated polyamine levels are the absolute requirement for tumor growth and progression. The concentrations of cellular polyamines are controlled by the polyamine regulatory circuit comprising three different proteins: Ornithine Decarboxylase (ODC), Ornithine Decarboxylase Antizyme (OAZ), and Antizyme Inhibitor (AZIN). While ODC is directly involved in polyamine biosynthesis, OAZ and AZIN regulate the ODC activity via protein‐protein interactions. The dysregulation of ODC, OAZ, and AZIN leads to elevated polyamines in numerous pathologies, making them attractive targets to control polyamine levels. Besides regulating polyamine synthesis, OAZ is believed to modulate polyamine transport via multiple pathways. However, the precise mechanism of OAZ‐mediated polyamine regulation outside of the polyamine biosynthetic pathway remains elusive. We hypothesize that OAZ sequestration results in increased polyamine uptake. To provide evidence to our hypothesis, we generated covalent OAZ‐mimetic inactivators targeting both ODC and AZIN. Using biochemical experiments, we demonstrate that these OAZ‐mimetics inhibit the activity of ODC and prevent the sequestration of OAZ by AZIN. Using Mass spectrometric experiments, we determine the covalent binding of OAZ‐mimetics to both ODC and AZIN. We employ a novel gel assay to assess the rate of covalent modification of ODC and AZIN. Finally, using computational modeling, we determine the mode of binding of OAZ‐mimetics to both ODC and AZIN to provide insights into inhibition mechanisms.

Melatonin treatment induces chilling tolerance by regulating the contents of polyamine, γ-aminobutyric acid, and proline in cucumber fruit

The mechanism of melatonin (MT) induced chilling tolerance in harvested cucumber fruit was investigated at commercial maturity. In this study, cucumber fruits were treated with 100 µmol L–1 MT at 4°C and 90% relative humidity for 15 d of storage. In comparison with the control, cucumber treatment with MT resulted in reduced chilling injury (CI), decreased electrolyte leakage and enhanced firmness. The fruits treated with MT showed higher chlorophyll contents in storage conditions with suppressed chlorophyllase enzyme activity. MT treatment increased arginine decarboxylase (ADC) and ornithine decarboxylase (ODC) enzyme activities. Moreover, enhanced expression of the Cucumis sativus ADC (CsADC) and C. sativus ODC (CsODC) genes resulted in the accumulation of polyamine contents. Similarly, proline levels exhibited higher levels among treated fruits. Meanwhile, the proline synthesizing enzymes △1-pyrroline-5-carboxylate syntheses (P5CS) and ornithine aminotransferase (OAT) were significantly increased, while a catabolic enzyme of proline dehydrogenase (PDH) activity was inhibited by treatment. In addition, MT induced expression of C. sativus OAT (CsOAT) and C. sativus P5CS (CsP5CS) genes. Cucumber fruits treated with MT also exhibited higher γ-aminobutyric acid (GABA) content by enhanced GABA transaminase (GABA-T) and glutamate decarboxylase (GAD) enzyme activities and a higher C. sativus GAD (CsGAD) gene expression. To sum up, the results show that MT treatment enhanced chilling tolerance, which was associated with the regulation of polyamines, as well as proline and γ-aminobutyric acid.

Polyamine and nitrogen metabolism regulation by melatonin and salicylic acid combined treatment as a repressor for salt toxicity in wheat (Triticum aestivum L.) plants

Polyamine and nitrogen metabolism regulation by melatonin and salicylic acid combined treatment as a repressor for salt toxicity in wheat (Triticum aestivum L.) plants

Arbuscular Mycorrhiza-Mediated Regulation of Polyamines and Aquaporins During Abiotic Stress: Deep Insights on the Recondite Players.

Environmental stresses of (a)biotic origin induce the production of multitudinous compounds (metabolites and proteins) as protective defense mechanisms in plants. On account of the regulation of some of these compounds, arbuscular mycorrhizal fungi (AMF) reinforce the inherent tolerance of plants toward the stress of different origins and kind. This article reviews two specific fundamental mechanisms that are categorically associated with mycorrhiza in alleviating major abiotic stresses, salt, drought, and heavy metal (HM) toxicity. It puts emphasis on aquaporins (AQPs), the conduits of water and stress signals; and polyamines (PAs), the primordial stress molecules, which are regulated by AMF to assure water, nutrient, ion, and redox homeostasis. Under stressful conditions, AMF-mediated host AQP responses register distinct patterns: an upregulation to encourage water and nutrient uptake; a downregulation to restrict water loss and HM uptake; or no alterations. The patterns thereof are apparently an integrative outcome of the duration, intensity, and type of stress, AMF species, the interaction of fungal AQPs with that of plants, and the host type. However, the cellular and molecular bases of mycorrhizal influence on host AQPs are largely unexplored. The roles of PAs in augmenting the antioxidant defense system and improving the tolerance against oxidative stress are well-evident. However, the precise mechanism by which mycorrhiza accords stress tolerance by influencing the PA metabolism per se is abstruse and broadly variable under different stresses and plant species. This review comprehensively analyzes the current state-of-art of the involvement of AMF in “PA and AQP modulation” under abiotic stress and identifies the lesser-explored landscapes, gaps in understanding, and the accompanying challenges. Finally, this review outlines the prospects of AMF in realizing sustainable agriculture and provides insights into potential thrust areas of research on AMF and abiotic stress.

Isoamylamine Induces B16-F1 Melanoma Cell Autophagy by Upregulating the 5' Adenosine Monophosphate-Activated Protein Pathway.

Isoamylamine (IA) is an aliphatic monoamine molecule present in cheese, eggs, and wine. It belongs to the family of polyamines and also can be synthesized endogenously. It has been known that regulation of polyamines in cells is related to cell cycle and tumor formation. Malignant melanoma is difficult to treat and easily resistant to chemotherapy/radiotherapy through autophagy. In this study, we aim to clarify whether IA has a growth control effect on melanoma tumor cells and the regulatory mechanism. We treated B16-F1 melanoma cells with IA at concentrations of 0, 200, 400, and 600 ppm for 24 h. The 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT) assay was checked for cell viability and results showed that IA has an inhibitory effect on B16-F1 melanoma cells. The signaling molecules, which included Raf/MEK/ERK, were activated, while MSK1 and protein kinase B (AKT) were suppressed. Autophagy was also confirmed to be induced by IA. The acridine orange stain-positive cells were increased and BECN-1/LC3 upregulated. The data also showed that the autophagy regulatory molecule, 5'-adenosine monophosphate-activated protein kinase (AMPK), was induced after IA treatment, so we used dorsomorphin to inhibit AMPK and found that it could suppress autophagy. In conclusion, IA has an effect of inducing autophagy in B16-F1 cells and it is regulated through AMPK.

Polyamines Mediate Folding of Primordial Hyperacidic Helical Proteins.

Polyamines are known to mediate diverse biological processes, and specifically to bind and stabilize compact conformations of nucleic acids, acting as chemical chaperones that promote folding by offsetting the repulsive negative charges of the phosphodiester backbone. However, whether and how polyamines modulate the structure and function of proteins remain unclear. In particular, early proteins are thought to have been highly acidic, like nucleic acids, due to a scarcity of basic amino acids in the prebiotic context. Perhaps polyamines, the abiotic synthesis of which is simple, could have served as chemical chaperones for such primordial proteins? We replaced all lysines of an ancestral 60-residue helix-bundle protein with glutamate, resulting in a disordered protein with 21 glutamates in total. Polyamines efficiently induce folding of this hyperacidic protein at submillimolar concentrations, and their potency scaled with the number of amine groups. Compared to cations, polyamines were several orders of magnitude more potent than Na+, while Mg2+ and Ca2+ had an effect similar to that of a diamine, inducing folding at approximately seawater concentrations. We propose that (i) polyamines and dications may have had a role in promoting folding of early proteins devoid of basic residues and (ii) coil–helix transitions could be the basis of polyamine regulation in contemporary proteins.

Polyamine regulation of porcine reproductive and respiratory syndrome virus infection depends on spermidine-spermine acetyltransferase 1

Like obligate intracellular parasites, viruses co-opt host cell resources to establish productive infections. Polyamines are key aliphatic molecules that perform important roles in cellular growth and proliferation. They are also needed for the successful multiplication of various viruses. Little is known about the effects of polyamines on Arteriviridae infections. Here, porcine reproductive and respiratory syndrome virus (PRRSV), an economically prominent porcine virus, was used to investigate virus–polyamine interactions. We found that PRRSV infection significantly downregulated the levels of cellular polyamines. Using an inhibitor or specific short interfering RNAs (siRNAs) of ornithine decarboxylase 1, a key anabolic enzyme involved in the classical de novo biosynthesis of polyamines, we found that polyamine depletion abrogated PRRSV proliferation, and this effect was recoverable by adding exogenous spermidine and spermine, but not putrescine to the cells, suggesting that the host inhibits polyamine biosynthesis to restrict PRRSV proliferation. Further analysis revealed that the expression level of spermidine-spermine acetyltransferase 1 (SAT1), a catabolic enzyme that reduces spermidine and spermine levels, was upregulated during PRRSV infection, but conversely, SAT1 had an inhibitory effect on PRRSV reproduction. Our data show that polyamines are important molecules during PRRSV-host interactions, and polyamines and their biosynthetic pathways are potential therapeutic targets against PRRSV infection.

Abstract 566: Therapeutic targeting of the polyamine pathway and EIF5A1 hypusination in endometrial cancer with DFMO and GC7

Abstract The polyamines putrescine, spermidine, and spermine are well-characterized oncometabolites upregulated in cancers and drive their proliferation and spread. Endometrial cancers (ECs) express high levels of ornithine decarboxylase (ODC), a rate-limiting enzyme of polyamine biosynthesis and decreased levels of spermidine/spermine N1-acetyltransferase (SAT1), a key negative regulator of polyamines. In addition, the deoxyhypusine synthase (DHPS) enzyme necessary for spermidine-dependent hypusination of eIF5A1 is highly expressed in ECs. Hypusinated EIF5A1 is needed by cancer cells to support their increased protein translation needs. Collectively, these findings suggest that the polyamine pathway is particularly active and necessary in EC. Here we evaluated the effect of ODC inhibitor difluoromethylornithine (DFMO) and DHPS inhibitor N1-Guanyl-1,7-Diaminoheptane (GC7) alone or in combination on the growth of ECs. GC7 and DFMO were effective in suppressing growth in EC cell lines in vitro as measured by MTS viability and proliferation assays. These effects were accompanied by decreased hypusinated EIF5A1 in treated cells. However, neither compound induced apoptotic cell death when applied singly. We did note that when non-apoptotic inducing doses of DFMO and GC7 were combined, EC cells showed a marked combinatorial decrease in viability, proliferation, and hypusinated EIF5A1 levels. Importantly we found that combined DFMO/GC7 treatment caused apoptotic cell death of EC cells as measured by cleaved PARP. Furthermore, levels of cleaved caspases 3 and 7 were increased in these cells while caspases 5 or 9 were not cleaved. In summary we found for the first time that pharmacologically increased depression of the polyamine pathway as measured by decreased hypusinated EIFA1 can lead to apoptotic cell death in ECs. These data suggest that targeting the polyamine pathway and particularly its role in protein translation through EIF5A1 hypusination may be an effective treatment strategy. Citation Format: HongIm Kim, Chad Schultz, Andre Bachmann, John I. Risinger. Therapeutic targeting of the polyamine pathway and EIF5A1 hypusination in endometrial cancer with DFMO and GC7 [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 566.

Metabolic regulation of polyamines and γ-aminobutyric acid in relation to spermidine-induced heat tolerance in white clover.

Heat stress decreases crop growth and yield worldwide. Spermidine (Spd) is a small aliphatic amine and acts as a ubiquitous regulator for plant growth, development and stress tolerance. Objectives of this study were to determine effects of exogenous Spd on changes in endogenous polyamine (PA) and γ-aminobutyric acid (GABA) metabolism, oxidative damage, senescence and heat shock protein (HSP) expression in white clover subjected to heat stress. Physiological and molecular methods, including colorimetric assay, high performance liquid chromatography and qRT-PCR, were applied. Results showed that exogenous Spd significantly alleviated heat-induced stress damage. Application of Spd not only increased endogenous putrescine, Spd, spermine and total PA accumulation, but also accelerated PA oxidation and improved glutamic acid decarboxylase activity, leading to GABA accumulation in leaves under heat stress. The Spd-pretreated white clover maintained a significantly higher chlorophyll (Chl) content than untreated plants under heat stress, which could be related to the roles of Spd in up-regulating genes encoding Chl synthesis (PBGD and Mg-CHT) and maintaining reduced Chl degradation (PaO and CHLASE) during heat stress. In addition, Spd up-regulated HSP70, HSP70B and HSP70-5 expression, which might function in stabilizing denatured proteins and helping proteins to folding correctly in white clover under high temperature stress. In summary, exogenous Spd treatment improves the heat tolerance of white clover by altering endogenous PA and GABA content and metabolism, enhancing the antioxidant system and HSP expression and slowing leaf senescence related to an increase in Chl biosynthesis and a decrease in Chl degradation during heat stress.

Polyamine regulation of ion channel assembly and implications for nicotinic acetylcholine receptor pharmacology

Small molecule polyamines are abundant in all life forms and participate in diverse aspects of cell growth and differentiation. Spermidine/spermine acetyltransferase (SAT1) is the rate-limiting enzyme in polyamine catabolism and a primary genetic risk factor for suicidality. Here, using genome-wide screening, we find that SAT1 selectively controls nicotinic acetylcholine receptor (nAChR) biogenesis. SAT1 specifically augments assembly of nAChRs containing α7 or α4β2, but not α6 subunits. Polyamines are classically studied as regulators of ion channel gating that engage the nAChR channel pore. In contrast, we find polyamine effects on assembly involve the nAChR cytosolic loop. Neurological studies link brain polyamines with neurodegenerative conditions. Our pharmacological and transgenic animal studies find that reducing polyamines enhances cortical neuron nAChR expression and augments nicotine-mediated neuroprotection. Taken together, we describe a most unexpected role for polyamines in regulating ion channel assembly, which provides a new avenue for nAChR neuropharmacology.

Polyamine Regulation in Diabetic Breast Cancer Cells

Polyamines (spermine, spermidine, and putrescine) are involved in basic cellular processes such as cell growth, replication, and transcription. They are highly regulated cations that are elevated in cancer. Upregulation of polyamines can thus develop tumors due to hyper‐proliferation of cells as observed in cancers of the colon, skin, prostate and breast. Inhibitors of polyamine pathway could prevent tumor growth as shown in animal models of colon and skin cancer. Intracellular polyamine is regulated by biosynthesis, intestinal uptake and microbial production. Thus inhibitors of synthesis alone have not been very effective as cytotoxic agents but exhibit cytostatic properties. Diabetic conditions further accelerate the growth and metastasis of cancers such as pancreas, breast, liver, and colorectal, however the role of polyamines in such states has not been investigated. We hypothesized that polyamine regulation affects proliferation of breast cancer cells and normal breast epithelial cells in diabetic conditions. Breast cancer cells (MDA‐MB‐231) and normal breast epithelial cells (MCF‐10A) were treated with normal glucose (NG, 5mM) or high glucose (HG, 25 mM) in the presence/absence of polyamine pathway inhibitors. Cells were then treated with polyamine supplements, following depletion with polyamine pathway inhibitors. There was a time dependent increase in cell proliferation with HG from 48–72 hr compared to NG. This was correlated with an increase in polyamines (putrescine, spermidine) though spermine levels were not changed considerably. Simultaneous treatment with an ornithine decarboxylase (polyamine synthesis enzyme) inhibitor, difluoromethylornithine (DFMO) could prevent cell proliferation, restore polyamines, and normalize polyamine catabolic enzymes with high glucose exposure. In conclusion, polyamine regulation is responsible for proliferation of breast cancer cells and normal breast epithelial cells in diabetic states, which can be prevented using inhibitors affecting polyamine levels in cells.Support or Funding Information Funding: Grants from the UNK Undergraduate Research Fellows Program and UNK Research Services Council Seed Grant Equipment: Microplate Reader (Dr. Nuxoll’s lab), Grant from the National Institute for General Medical Science (NIGMS) (5P20GM103427), a component of the National Institutes of Health (NIH)

Transcriptome Analysis of Acid-Responsive Genes and Pathways Involved in Polyamine Regulation in Iron Walnut.

We reported changes in the co-regulated mRNA expression in iron walnut (Juglans sigillata) in response to soil pH treatments and identified mRNAs specific to acidic soil conditions. Phenotypic and physiological analyses revealed that iron walnut growth was greater for the pH 4–5 and pH 5–6 treatments than for the pH 3–4 and pH 6–7 treatments. A total of 2768 differentially expressed genes were detected and categorized into 12 clusters by Short Time-series Expression Miner (STEM). The 994 low-expression genes in cluster III and 255 high-expression genes in cluster X were classified as acid-responsive genes on the basis of the relationships between phenotype, physiology, and STEM clustering, and the two gene clusters were analyzed by a maximum likelihood (ML) evolutionary tree with the greatest log likelihood values. No prominent sub-clusters occurred in cluster III, but three occurred in cluster X. The Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis indicated that acid-responsive genes were related primarily to arginine biosynthesis and the arginine/proline metabolism pathway, implying that polyamine accumulation may enhance iron walnut acid stress tolerance. Overall, our results revealed 1249 potentially acid-responsive genes in iron walnut, indicating that its response to acid stress involves different pathways and activated genes.