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Ovarian cancer often develops resistance to conventional therapies, hampering their effectiveness. Here, using ex vivo paired ovarian cancer ascites obtained before and after chemotherapy and in vitro therapy-induced secretomes, we show that molecules secreted by ovarian cancer cells upon therapy promote cisplatin resistance and enhance DNA damage repair in recipient cancer cells. Even a short-term incubation of chemonaive ovarian cancer cells with therapy-induced secretomes induces changes resembling those that are observed in chemoresistant patient-derived tumor cells after long-term therapy. Using integrative omics techniques, we find that both ex vivo and in vitro therapy-induced secretomes are enriched with spliceosomal components, which relocalize from the nucleus to the cytoplasm and subsequently into the extracellular vesicles upon treatment. We demonstrate that these molecules substantially contribute to the phenotypic effects of therapy-induced secretomes. Thus, SNU13 and SYNCRIP spliceosomal proteins promote therapy resistance, while the exogenous U12 and U6atac snRNAs stimulate tumor growth. These findings demonstrate the significance of spliceosomal network perturbation during therapy and further highlight that extracellular signaling might be a key factor contributing to the emergence of ovarian cancer therapy resistance.
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Cisplatino , Resistencia a Antineoplásicos , Neoplasias Ováricas , Empalmosomas , Femenino , Humanos , Neoplasias Ováricas/metabolismo , Neoplasias Ováricas/patología , Neoplasias Ováricas/genética , Neoplasias Ováricas/tratamiento farmacológico , Empalmosomas/metabolismo , Cisplatino/farmacología , Línea Celular Tumoral , Animales , Ratones , Vesículas Extracelulares/metabolismo , Supervivencia Celular/efectos de los fármacos , Antineoplásicos/farmacología , ARN Nuclear Pequeño/metabolismo , ARN Nuclear Pequeño/genética , Reparación del ADNRESUMEN
The COVID-19 pandemic, caused by the SARS-CoV-2 virus, has significantly impacted global healthcare, underscoring the importance of exploring the virus's effects on infected individuals beyond treatments and vaccines. Notably, recent findings suggest that SARS-CoV-2 can infect the gut, thereby altering the gut microbiota. This study aimed to analyze the gut microbiota composition differences between COVID-19 patients experiencing mild and severe symptoms. We conducted 16S rRNA metagenomic sequencing on fecal samples from 49 mild and 43 severe COVID-19 cases upon hospital admission. Our analysis identified a differential abundance of specific bacterial species associated with the severity of the disease. Severely affected patients showed an association with Enterococcus faecium, Akkermansia muciniphila, and others, while milder cases were linked to Faecalibacterium prausnitzii, Alistipes putredinis, Blautia faecis, and additional species. Furthermore, a network analysis using SPIEC-EASI indicated keystone taxa and highlighted structural differences in bacterial connectivity, with a notable disruption in the severe group. Our study highlights the diverse impacts of SARS-CoV-2 on the gut microbiome among both mild and severe COVID-19 patients, showcasing a spectrum of microbial responses to the virus. Importantly, these findings align, to some extent, with observations from other studies on COVID-19 gut microbiomes, despite variations in methodologies. The findings from this study, based on retrospective data, establish a foundation for future prospective research to confirm the role of the gut microbiome as a predictive biomarker for the severity of COVID-19.
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MOTIVATION: The Oxford Nanopore technology has a great potential for the analysis of methylated motifs in genomes, including whole-genome methylome profiling. However, we found that there are no methylation motifs detection algorithms, which would be sensitive enough and return deterministic results. Thus, the MEME suit does not extract all Helicobacter pylori methylation sites de novo even using the iterative approach implemented in the most up-to-date methylation analysis tool Nanodisco. RESULTS: We present Snapper, a new highly sensitive approach, to extract methylation motif sequences based on a greedy motif selection algorithm. Snapper does not require manual control during the enrichment process and has enrichment sensitivity higher than MEME coupled with Tombo or Nanodisco instruments that was demonstrated on H.pylori strain J99 studied earlier by the PacBio technology and on four external datasets representing different bacterial species. We used Snapper to characterize the total methylome of a new H.pylori strain A45. At least four methylation sites that have not been described for H.pylori earlier were revealed. We experimentally confirmed the presence of a new CCAG-specific methyltransferase and inferred a gene encoding a new CCAAK-specific methyltransferase. AVAILABILITY AND IMPLEMENTATION: Snapper is implemented using Python and is freely available as a pip package named "snapper-ont." Also, Snapper and the demo dataset are available in Zenodo (10.5281/zenodo.10117651).
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Genoma Bacteriano , Nanoporos , Metilación de ADN , Metiltransferasas/genética , Metiltransferasas/metabolismo , Algoritmos , Análisis de Secuencia de ADN/métodos , Secuenciación de Nucleótidos de Alto RendimientoRESUMEN
The commensal microflora provides a repertoire of antigens that illicit mucosal antibodies. In some cases, these antibodies can cross-react with host proteins, inducing autoimmunity, or with other microbial antigens. We demonstrate that the oral microbiota can induce salivary anti-SARS-CoV-2 Spike IgG antibodies via molecular mimicry. Anti-Spike IgG antibodies in the saliva correlated with enhanced abundance of Streptococcus salivarius 1 month after anti-SARS-CoV-2 vaccination. Several human commensal bacteria, including S. salivarius, were recognized by SARS-CoV-2-neutralizing monoclonal antibodies and induced cross-reactive anti-Spike antibodies in mice, facilitating SARS-CoV-2 clearance. A specific S. salivarius protein, RSSL-01370, contains regions with homology to the Spike receptor-binding domain, and immunization of mice with RSSL-01370 elicited anti-Spike IgG antibodies in the serum. Additionally, oral S. salivarius supplementation enhanced salivary anti-Spike antibodies in vaccinated individuals. Altogether, these data show that distinct species of the human microbiota can express molecular mimics of SARS-CoV-2 Spike protein, potentially enhancing protective immunity.
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COVID-19 , Microbiota , Humanos , Animales , Ratones , Glicoproteína de la Espiga del Coronavirus , Formación de Anticuerpos , Imitación Molecular , SARS-CoV-2 , Anticuerpos Monoclonales , Anticuerpos Antivirales , Inmunoglobulina A Secretora , Inmunoglobulina G , Anticuerpos NeutralizantesRESUMEN
Life expectancy and age-related diseases burden increased significantly over the past few decades. Age-related conditions are commonly discussed in a very limited paradigm of depleted cellular proliferation and maturation with exponential accumulation of senescent cells. However, most recent evidence showed that the majority of age-associated ailments, i.e., diabetes mellitus, cardiovascular diseases and neurodegeneration. These diseases are closely associated with tissue nonspecific inflammation triggered and controlled by mesenchymal stromal cell secretion. Mesenchymal stromal cells (MSCs) are known as the most common type of cells for therapeutic approaches in clinical practice. Side effects and complications of MSC-based treatments increased interest in the MSCs secretome as an alternative concept for validation tests in regenerative medicine. The most recent data also proposed it as an ideal tool for cell-free regenerative therapy and tissue engineering. However, senescent MSCs secretome was shown to hold the role of 'key-driver' in inflammaging. We aimed to review the immunomodulatory effects of the MSCs-secretome during cell senescence and provide eventual insight into the interpretation of its beneficial biological actions in inflammaging-associated diseases.
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Células Madre Mesenquimatosas , Humanos , Células Madre Mesenquimatosas/metabolismo , Senescencia Celular , Medicina Regenerativa , Inflamación/metabolismo , Tratamiento Basado en Trasplante de Células y TejidosRESUMEN
The epigenetics of bacteria, and bacteria with a reduced genome in particular, is of great interest, but is still poorly understood. Mycoplasma gallisepticum, a representative of the class Mollicutes, is an excellent model of a minimal cell because of its reduced genome size, lack of a cell wall, and primitive cell organization. In this study we investigated DNA modifications of the model object Mycoplasma gallisepticum and their roles. We identified DNA modifications and methylation motifs in M. gallisepticum S6 at the genome level using single molecule real time (SMRT) sequencing. Only the ANCNNNNCCT methylation motif was found in the M. gallisepticum S6 genome. The studied bacteria have one functional system for DNA modifications, the Type I restriction-modification (RM) system, MgaS6I. We characterized its activity, affinity, protection and epigenetic functions. We demonstrated the protective effects of this RM system. A common epigenetic signal for bacteria is the m6A modification we found, which can cause changes in DNA-protein interactions and affect the cell phenotype. Native methylation sites are underrepresented in promoter regions and located only near the -35 box of the promoter, which does not have a significant effect on gene expression in mycoplasmas. To study the epigenetics effect of m6A for genome-reduced bacteria, we constructed a series of M. gallisepticum strains expressing EGFP under promoters with the methylation motifs in their different elements. We demonstrated that m6A modifications of the promoter located only in the -10-box affected gene expression and downregulated the expression of the corresponding gene.
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Mycoplasma gallisepticum , Tenericutes , Mycoplasma gallisepticum/genética , ADN Bacteriano/genética , ADN Bacteriano/metabolismo , Enzimas de Restricción-Modificación del ADN/genética , Tenericutes/genética , Metilación de ADNRESUMEN
Cancer-associated fibroblasts (CAFs) have long been known as one of the most important players in tumor initiation and progression. Even so, there is an incomplete understanding of the identification of CAFs among tumor microenvironment cells as the list of CAF marker genes varies greatly in the literature, therefore it is imperative to find a better way to identify reliable markers of CAFs. To this end, we summarized a large number of single-cell RNA-sequencing data of multiple tumor types and corresponding normal tissues. As a result, for 9 different types of cancer, we identified CAF-specific gene expression signatures and found 10 protein markers that showed strongly positive staining of tumor stroma according to the analysis of IHC images from the Human Protein Atlas database. Our results give an insight into selecting the most appropriate combination of cancer-associated fibroblast markers. Furthermore, comparison of different approaches for studying differences between cancer-associated and normal fibroblasts (NFs) illustrates the superiority of transcriptome analysis of fibroblasts obtained from fresh tissue samples. Using single-cell RNA sequencing data, we identified common differences in gene expression patterns between normal and cancer-associated fibroblasts, which do not depend on the type of tumor.
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Mycoplasmas are pathogenic, genome-reduced bacteria. The development of such fields of science as system and synthetic biology is closely associated with them. Despite intensive research of different representatives of this genus, genetic manipulations remain challenging in mycoplasmas. Here we demonstrate a single-plasmid transposon-based CRISPRi system for the repression of gene expression in mycoplasmas. We show that selected expression determinants provide a level of dCas9 that does not lead to a significant slow-down of mycoplasma growth. For the first time we describe the proteomic response of genome-reduced bacteria to the expression of exogenous dcas9. The functionality of the resulting vector is confirmed by targeting the three genes coding transcription factors-fur, essential spxA, whiA, and histone-like protein hup1 in Mycoplasma gallisepticum. As a result, the expression level of each gene was decreased tenfold and influenced the mRNA level of predicted targets of transcription factors. To illustrate the versatility of this vector, we performed a knockdown of metabolic genes in a representative member of another cluster of the Mycoplasma genus-Mycoplasma hominis. The developed CRISPRi system is a powerful tool to discover the functioning of genes that are essential, decipher regulatory networks and that can help to identify novel drug targets to control Mycoplasma infections.
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COVID-19 caused by SARS-CoV-2 is continuing to spread around the world and drastically affect our daily life. New strains appear, and the severity of the course of the disease itself seems to be decreasing, but even people who have been ill on an outpatient basis suffer post-COVID consequences. Partly, it is associated with the autoimmune reactions, so debates about the development of new vaccines and the need for vaccination/revaccination continue. In this study we performed an analysis of the antibody response of patients with COVID-19 to linear and conformational epitopes of viral proteins using ELISA, chip array and western blot with analysis of correlations between antibody titer, disease severity, and complications. We have shown that the presence of IgG antibodies to the nucleoprotein can deteriorate the course of the disease, induce multiple direct COVID-19 symptoms, and contribute to long-term post-covid symptoms. We analyzed the cross reactivity of antibodies to SARS-CoV-2 with own human proteins and showed that antibodies to the nucleocapsid protein can bind to human proteins. In accordance with the possibility of HLA presentation, the main possible targets of the autoantibodies were identified. People with HLA alleles A01:01; A26:01; B39:01; B15:01 are most susceptible to the development of autoimmune processes after COVID-19.
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COVID-19 , SARS-CoV-2 , Anticuerpos Antivirales , COVID-19/complicaciones , Humanos , Nucleoproteínas , Glicoproteína de la Espiga del Coronavirus , Síndrome Post Agudo de COVID-19RESUMEN
Short-chain fatty acids are metabolites widely presented in many natural sources, including human feces and blood. Estimation of their composition is a common procedure, usually performed using nuclear magnetic resonance or gas chromatography with a flame ionization detector. However, the commonly used methods often depend on specific sample preparation, such as filtration and homogenization. The gas-chromatography/mass-spectrometry (GC/MS) method with headspace extraction allows sample preparation to be kept to a minimum regardless of the physical state of the sample, which can be potentially useful in metabolomics research of complex natural samples such as blood or feces. In this work, we have demonstrated the applicability of Headspace GC-MS for estimating short chain fatty acid (SCFA) composition. The main problem here is the complex, non-linear dependence between the composition of the compounds in the source phase and the relative pressures in the vapor phase, which are directly measured by this method. We have implemented a thermodynamic model that performs the reverse transformation of relative abundances in the vapor phase to relative concentrations in the liquid phase, and have tested it on some synthetic SCFA mixtures. The developed method is available as a pip package called UniqPy and can be used to describe liquid-vapor equilibrium for any multicomponent system if a sufficient amount of training data is provided. The gas chromatography method with headspace extraction in conjunction with the UniqPy data transformation showed satisfactory quantification accuracy for propionic acid, butyric acid, isobutyric acid, and valeric acid (R-squared > 0.96). The applicability of the method was additionally demonstrated on a series of fecal samples.
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Ácidos Grasos Volátiles , Metabolómica , Ácidos Grasos/análisis , Ácidos Grasos Volátiles/análisis , Heces/química , Ionización de Llama , Cromatografía de Gases y Espectrometría de Masas/métodos , Humanos , Metabolómica/métodosRESUMEN
The structure and dynamics of bacterial nucleoids play important roles in regulating gene expression. Bacteria of class Mollicutes and, in particular, mycoplasmas feature extremely reduced genomes. They lack multiple structural proteins of the nucleoid, as well as regulators of gene expression. We studied the organization of Mycoplasma gallisepticum nucleoids in the stationary and exponential growth phases at the structural and protein levels. The growth phase transition results in the structural reorganization of M. gallisepticum nucleoid. In particular, it undergoes condensation and changes in the protein content. The observed changes corroborate with the previously identified global rearrangement of the transcriptional landscape in this bacterium during the growth phase transition. In addition, we identified that the glycolytic enzyme enolase functions as a nucleoid structural protein in this bacterium. It is capable of non-specific DNA binding and can form fibril-like complexes with DNA.
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Cell proliferation is associated with increased energy and nutrients consumption. Metabolism switch from oxidative phosphorylation to glycolysis and telomerase activity are induced during stimulation of proliferation, such as tumorigenesis, immune cell activation, and stem cell differentiation, among others. Telomerase RNA is one of the core components of the telomerase complex and participates in survival mechanisms that are activated under stress conditions. Human telomerase RNA protein (hTERP) is encoded by telomerase RNA and has been recently shown to be involved in autophagy regulation. In this study, we demonstrated the role of hTERP in the modulation of signaling pathways regulating autophagy, protein biosynthesis, and cell proliferation. The AMPK signaling pathway was affected in cells deficient of hTERP and when hTERP was overexpressed. The appearance of hTERP is important for metabolism switching associated with the accelerated proliferation of cells in healthy and pathological processes. These findings demonstrate the connection between telomerase RNA biogenesis and function and signaling pathways.
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Whole-exome sequencing is an attractive alternative to microarray analysis because of the low cost and potential ability to detect copy number variations (CNV) of various sizes (from 1-2 exons to several Mb). Previous comparison of the most popular CNV calling tools showed a high portion of false-positive calls. Moreover, due to a lack of a gold standard CNV set, the results are limited and incomparable. Here, we aimed to perform a comprehensive analysis of tools capable of germline CNV calling available at the moment using a single CNV standard and reference sample set. Compiling variants from previous studies with Bayesian estimation approach, we constructed an internal standard for NA12878 sample (pilot National Institute of Standards and Technology Reference Material) including 110,050 CNV or non-CNV exons. The standard was used to evaluate the performance of 16 germline CNV calling tools on the NA12878 sample and 10 correlated exomes as a reference set with respect to length distribution, concordance, and efficiency. Each algorithm had a certain range of detected lengths and showed low concordance with other tools. Most tools are focused on detection of a limited number of CNVs one to seven exons long with a false-positive rate below 50%. EXCAVATOR2, exomeCopy, and FishingCNV focused on detection of a wide range of variations but showed low precision. Upon unified comparison, the tools were not equivalent. The analysis performed allows choosing algorithms or ensembles of algorithms most suitable for a specific goal, e.g. population studies or medical genetics.
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Variaciones en el Número de Copia de ADN , Benchmarking , Exoma , Humanos , Secuenciación del ExomaRESUMEN
Non-proteinogenic neurotoxic amino acid ß-N-methylamino-L-alanine (BMAA) is synthesized by cyanobacteria, diatoms, and dinoflagellates, and is known to be a causative agent of human neurodegenerative diseases. Different phytoplankton organisms' ability to synthesize BMAA could indicate the importance of this molecule in the interactions between microalgae in nature. We were interested in the following: what kinds of mechanisms underline BMAA's action on cyanobacterial cells in different nitrogen supply conditions. Herein, we present a proteomic analysis of filamentous cyanobacteria Nostoc sp. PCC 7120 cells that underwent BMAA treatment in diazotrophic conditions. In diazotrophic growth conditions, to survive, cyanobacteria can use only biological nitrogen fixation to obtain nitrogen for life. Note that nitrogen fixation is an energy-consuming process. In total, 1567 different proteins of Nostoc sp. PCC 7120 were identified by using LC-MS/MS spectrometry. Among them, 123 proteins belonging to different functional categories were selected-due to their notable expression differences-for further functional analysis and discussion. The presented proteomic data evidences that BMAA treatment leads to very strong (up to 80%) downregulation of α (NifD) and ß (NifK) subunits of molybdenum-iron protein, which is known to be a part of nitrogenase. This enzyme is responsible for catalyzing nitrogen fixation. The genes nifD and nifK are under transcriptional control of a global nitrogen regulator NtcA. In this study, we have found that BMAA impacts in a total of 22 proteins that are under the control of NtcA. Moreover, BMAA downregulates 18 proteins that belong to photosystems I or II and light-harvesting complexes; BMAA treatment under diazotrophic conditions also downregulates five subunits of ATP synthase and enzyme NAD(P)H-quinone oxidoreductase. Therefore, we can conclude that the disbalance in energy and metabolite amounts leads to severe intracellular stress that induces the upregulation of stress-activated proteins, such as starvation-inducible DNA-binding protein, four SOS-response enzymes, and DNA repair enzymes, nine stress-response enzymes, and four proteases. The presented data provide new leads into the ecological impact of BMAA on microalgal communities that can be used in future investigations.
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Aminoácidos Diaminos/farmacología , Fijación del Nitrógeno/efectos de los fármacos , Nostoc/efectos de los fármacos , Proteínas Bacterianas/metabolismo , Bicarbonatos/metabolismo , Metabolismo de los Hidratos de Carbono/efectos de los fármacos , Dióxido de Carbono/metabolismo , Toxinas de Cianobacterias , Regulación hacia Abajo/efectos de los fármacos , Nitrógeno/metabolismo , Nitrogenasa/metabolismo , Nostoc/metabolismo , Nostoc/fisiología , Fosforilación/efectos de los fármacos , Fotosíntesis/efectos de los fármacos , Proteómica , Estrés Fisiológico/efectos de los fármacosRESUMEN
Major histocompatibility complex class I (MHC I) plays a crucial role in the development of adaptive immune response in vertebrates. MHC molecules are cell surface protein complexes loaded with short peptides and recognized by the T-cell receptors (TCR). Peptides associated with MHC are named immunopeptidome. The MHC I immunopeptidome is produced by the proteasome degradation of intracellular proteins. The knowledge of the immunopeptidome repertoire facilitates the creation of personalized antitumor or antiviral vaccines. A huge number of publications on the immunopeptidome diversity of different human and mouse biological samples-plasma, peripheral blood mononuclear cells (PBMCs), and solid tissues, including tumors-appeared in the scientific journals in the last decade. Significant immunopeptidome identification efficiency was achieved by advances in technology: the immunoprecipitation of MHC and mass spectrometry-based approaches. Researchers optimized common strategies to isolate MHC-associated peptides for individual tasks. They published many protocols with differences in the amount and type of biological sample, amount of antibodies, type and amount of insoluble support, methods of post-fractionation and purification, and approaches to LC-MS/MS identification of immunopeptidome. These parameters have a large impact on the final repertoire of isolated immunopeptidome. In this review, we summarize and compare immunopeptidome isolation techniques with an emphasis on the results obtained.
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Antígenos de Histocompatibilidad Clase I/metabolismo , Péptidos/aislamiento & purificación , Proteoma/metabolismo , Proteómica , Animales , Anticuerpos/metabolismo , Cromatografía de Afinidad , Antígenos de Histocompatibilidad Clase I/genética , HumanosRESUMEN
The malignant tumor is a complex heterogeneous set of cells functioning in a no less heterogeneous microenvironment. Like any dynamic system, cancerous tumors evolve and undergo changes in response to external influences, including therapy. Initially, most tumors are susceptible to treatment. However, remaining cancer cells may rapidly reestablish the tumor after a temporary remission. These new populations of malignant cells usually have increased resistance not only to the first-line agent, but also to the second- and third-line drugs, leading to a significant decrease in patient survival. Multiple studies describe the mechanism of acquired therapy resistance. In past decades, it became clear that, in addition to the simple selection of pre-existing resistant clones, therapy induces a highly complicated and tightly regulated molecular response that allows tumors to adapt to current and even subsequent therapeutic interventions. This review summarizes mechanisms of acquired resistance, such as secondary genetic alterations, impaired function of drug transporters, and autophagy. Moreover, we describe less obvious molecular aspects of therapy resistance in cancers, including epithelial-to-mesenchymal transition, cell cycle alterations, and the role of intercellular communication. Understanding these molecular mechanisms will be beneficial in finding novel therapeutic approaches for cancer therapy.
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Resistencia a Antineoplásicos , Redes Reguladoras de Genes , Neoplasias/genética , Autofagia , Ciclo Celular , Progresión de la Enfermedad , Transición Epitelial-Mesenquimal , Regulación Neoplásica de la Expresión Génica , HumanosRESUMEN
PURPOSE: Preclinical evaluation of PCA3 and AMACR transcript simultaneous detection in urine to diagnose clinical significant prostate cancer (prostate cancer with Gleason score ≥7) in a Russian cohort. PATIENTS AND METHODS: We analyzed urine samples of patients with a total serum PSA ≥2 ng/mL: 31 men with prostate cancer scheduled for radical prostatectomy, 128 men scheduled for first diagnostic biopsy (prebiopsy cohort). PCA3, AMACR, PSA and GPI transcripts were detected by multiplex reverse transcription quantitative polymerase chain reaction, and the results were used for scores for calculation and statistical analysis. RESULTS: There was no significant difference between clinically significant and nonsignificant prostate cancer PCA3 scores. However, there was a significant difference in the AMACR score (patients scheduled for radical prostatectomy p=0.0088, prebiopsy cohort p=0.029). We estimated AUCs, optimal cutoffs, sensitivities and specificities for PCa and csPCa detection in the prebiopsy cohort by tPSA, PCA3 score, PCPT Risk Calculator and classification models based on tPSA, PCA3 score and AMACR score. In the clinically significant prostate cancer ROC analysis, the PCA3 score AUC was 0.632 (95%CI: 0.511-0.752), the AMACR score AUC was 0.711 (95%CI: 0.617-0.806) and AUC of classification model based on the PCA3 score, the AMACR score and total PSA was 0.72 (95%CI: 0.58-0.83). In addition, the correlation of the AMACR score with the ratio of total RNA and RNA of prostate cells in urine was shown (tau=0.347, p=6.542e-09). Significant amounts of nonprostate RNA in urine may be a limitation for the AMACR score use. CONCLUSION: The AMACR score is a good predictor of clinically significant prostate cancer. Significant amounts of nonprostate RNA in urine may be a limitation for the AMACR score use. Evaluation of the AMACR score and classification models based on it for clinically significant prostate cancer detection with larger samples and a follow-up analysis is promising.
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An amendment to this paper has been published and can be accessed via the original article.
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All cyanobacteria produce a neurotoxic non-protein amino acid ß-N-methylamino-L-alanine (BMAA). However, the biological function of BMAA in the regulation of cyanobacteria metabolism still remains undetermined. It is known that BMAA suppresses the formation of heterocysts in diazotrophic cyanobacteria under nitrogen starvation conditions, and BMAA induces the formation of heterocyst-like cells under nitrogen excess conditions, by causing the expression of heterocyst-specific genes that are usually "silent" under nitrogen-replete conditions, as if these bacteria receive a nitrogen deficiency intracellular molecular signal. In order to find out the molecular mechanisms underlying this unexpected BMAA effect, we studied the proteome of cyanobacterium Nostoc sp. PCC 7120 grown under BMAA treatment in nitrogen-replete medium. Experiments were performed in two experimental settings: (1) in control samples consisted of cells grown without the BMAA treatment and (2) the treated samples consisted of cells grown with addition of an aqueous solution of BMAA (20 µM). In total, 1567 different proteins of Nostoc sp. PCC 7120 were identified by LC-MS/MS spectrometry. Among them, 80 proteins belonging to different functional categories were chosen for further functional analysis and interpretation of obtained proteomic data. Here, we provide the evidence that a pleiotropic regulatory effect of BMAA on the proteome of cyanobacterium was largely different under conditions of nitrogen-excess compared to its effect under nitrogen starvation conditions (that was studied in our previous work). The most significant difference in proteome expression between the BMAA-treated and untreated samples under different growth conditions was detected in key regulatory protein PII (GlnB). BMAA downregulates protein PII in nitrogen-starved cells and upregulates this protein in nitrogen-replete conditions. PII protein is a key signal transduction protein and the change in its regulation leads to the change of many other regulatory proteins, including different transcriptional factors, enzymes and transporters. Complex changes in key metabolic and regulatory proteins (RbcL, RbcS, Rca, CmpA, GltS, NodM, thioredoxin 1, RpbD, ClpP, MinD, RecA, etc.), detected in this experimental study, could be a reason for the appearance of the "starvation" state in nitrogen-replete conditions in the presence of BMAA. In addition, 15 proteins identified in this study are encoded by genes, which are under the control of NtcA-a global transcriptional regulator-one of the main protein partners and transcriptional regulators of PII protein. Thereby, this proteomic study gives a possible explanation of cyanobacterium starvation under nitrogen-replete conditions and BMAA treatment. It allows to take a closer look at the regulation of cyanobacteria metabolism affected by this cyanotoxin.