Bacterial Sirtuins Overview: An Open Niche to Explore

Sirtuins are deacetylase enzymes widely distributed in all domains of life. Although for decades they have been related only to histones deacetylation in eukaryotic organisms, today they are considered global regulators in both prokaryotes and eukaryotes. Despite the important role of sirtuins in humans, the knowledge about bacterial sirtuins is still limited. Several proteomics studies have shown that bacterial sirtuins deacetylate a large number of lysines in vivo, although the effect that this deacetylation causes in most of them remains unknown. To date, only the regulation of a few bacterial sirtuin substrates has been characterized, being their metabolic roles widely distributed: carbon and nitrogen metabolism, DNA transcription, protein translation, or virulence. One of the most current topics on acetylation and deacetylation focuses on studying stoichiometry using quantitative LC-MS/MS. The results suggest that prokaryotic sirtuins deacetylate at low stoichiometry sites, although more studies are needed to know if it is a common characteristic of bacterial sirtuins and its biological significance. Unlike eukaryotic organisms, bacteria usually have one or few sirtuins, which have been reported to have closer phylogenetic similarity with the human Sirt5 than with any other human sirtuin. In this work, in addition to carrying out an in-depth review of the role of bacterial sirtuins in their physiology, a phylogenetic study has been performed that reveals the evolutionary differences between sirtuins of different bacterial species and even between homologous sirtuins.

Download Full-text

hfqPlays Important Roles in Virulence and Stress Adaptation in Cronobacter sakazakii ATCC 29544

Infection and Immunity ◽

10.1128/iai.03161-14 ◽

2015 ◽

Vol 83 (5) ◽

pp. 2089-2098 ◽

Cited By ~ 21

Author(s):

Seongok Kim ◽

Hyelyeon Hwang ◽

Kwang-Pyo Kim ◽

Hyunjin Yoon ◽

Dong-Hyun Kang ◽

...

Keyword(s):

Pathogenic Bacteria ◽

Bacterial Species ◽

Soft Agar ◽

Host Cells ◽

Neonatal Meningitis ◽

Animal Cells ◽

Content Type ◽

Flagellar Biosynthesis

Cronobacterspp. are opportunistic pathogens that cause neonatal meningitis and sepsis with high mortality in neonates. Despite the peril associated withCronobacterinfection, the mechanisms of pathogenesis are still being unraveled. Hfq, which is known as an RNA chaperone, participates in the interaction with bacterial small RNAs (sRNAs) to regulate posttranscriptionally the expression of various genes. Recent studies have demonstrated that Hfq contributes to the pathogenesis of numerous species of bacteria, and its roles are varied between bacterial species. Here, we tried to elucidate the role of Hfq inC. sakazakiivirulence. In the absence ofhfq,C. sakazakiiwas highly attenuated in disseminationin vivo, showed defects in invasion (3-fold) into animal cells and survival (103-fold) within host cells, and exhibited low resistance to hydrogen peroxide (102-fold). Remarkably, the loss ofhfqled to hypermotility on soft agar, which is contrary to what has been observed in other pathogenic bacteria. The hyperflagellated bacteria were likely to be attributable to the increased transcription of genes associated with flagellar biosynthesis in a strain lackinghfq. Together, these data strongly suggest thathfqplays important roles in the virulence ofC. sakazakiiby participating in the regulation of multiple genes.

Download Full-text

Linc00426 accelerates lung adenocarcinoma progression by regulating miR-455-5p as a molecular sponge

Cell Death and Disease ◽

10.1038/s41419-020-03259-2 ◽

2020 ◽

Vol 11 (12) ◽

Author(s):

Hongli Li ◽

Qingjie Mu ◽

Guoxin Zhang ◽

Zhixin Shen ◽

Yuanyuan Zhang ◽

...

Keyword(s):

Lung Adenocarcinoma ◽

Molecular Mechanisms ◽

Epithelial Mesenchymal Transition ◽

Ectopic Expression ◽

Tumor Development ◽

Biological Significance ◽

Mesenchymal Transition

AbstractIncreasing lines of evidence indicate the role of long non-coding RNAs (LncRNAs) in gene regulation and tumor development. Hence, it is important to elucidate the mechanisms of LncRNAs underlying the proliferation, metastasis, and invasion of lung adenocarcinoma (LUAD). We employed microarrays to screen LncRNAs in LUAD tissues with and without lymph node metastasis and revealed their effects on LUAD. Among them, Linc00426 was selected for further exploration in its expression, the biological significance, and the underlying molecular mechanisms. Linc00426 exhibits ectopic expression in LUAD tissues and cells. The ectopic expression has been clinically linked to tumor size, lymphatic metastasis, and tumor differentiation of patients with LUAD. The deregulation of Linc00426 contributes to a notable impairment in proliferation, invasion, metastasis, and epithelial–mesenchymal transition (EMT) in vitro and in vivo. Mechanistically, the deregulation of Linc00426 could reduce cytoskeleton rearrangement and matrix metalloproteinase expression. Meanwhile, decreasing the level of Linc00426 or increasing miR-455-5p could down-regulate the level of UBE2V1. Thus, Linc00426 may act as a competing endogenous RNA (ceRNA) to abate miR-455-5p-dependent UBE2V1 reduction. We conclude that Linc00426 accelerates LUAD progression by acting as a molecular sponge to regulate miR-455-5p, and may be a potential novel tumor marker for LUAD.

Download Full-text

Corneal Infection Models: Tools to Investigate the Role of Biofilms in Bacterial Keratitis

Cells ◽

10.3390/cells9112450 ◽

2020 ◽

Vol 9 (11) ◽

pp. 2450

Author(s):

Lucy Urwin ◽

Katarzyna Okurowska ◽

Grace Crowther ◽

Sanhita Roy ◽

Prashant Garg ◽

...

Keyword(s):

Ex Vivo ◽

Bacterial Species ◽

Resistance Mechanisms ◽

Bacterial Keratitis ◽

Corneal Surface ◽

Corneal Infection ◽

Infection Models

Bacterial keratitis is a corneal infection which may cause visual impairment or even loss of the infected eye. It remains a major cause of blindness in the developing world. Staphylococcus aureus and Pseudomonas aeruginosa are common causative agents and these bacterial species are known to colonise the corneal surface as biofilm populations. Biofilms are complex bacterial communities encased in an extracellular polymeric matrix and are notoriously difficult to eradicate once established. Biofilm bacteria exhibit different phenotypic characteristics from their planktonic counterparts, including an increased resistance to antibiotics and the host immune response. Therefore, understanding the role of biofilms will be essential in the development of new ophthalmic antimicrobials. A brief overview of biofilm-specific resistance mechanisms is provided, but this is a highly multifactorial and rapidly expanding field that warrants further research. Progression in this field is dependent on the development of suitable biofilm models that acknowledge the complexity of the ocular environment. Abiotic models of biofilm formation (where biofilms are studied on non-living surfaces) currently dominate the literature, but co-culture infection models are beginning to emerge. In vitro, ex vivo and in vivo corneal infection models have now been reported which use a variety of different experimental techniques and animal models. In this review, we will discuss existing corneal infection models and their application in the study of biofilms and host-pathogen interactions at the corneal surface.

Download Full-text

Role of Phosphoglucomutase of Bordetella bronchiseptica in Lipopolysaccharide Biosynthesis and Virulence

Infection and Immunity ◽

10.1128/iai.68.8.4673-4680.2000 ◽

2000 ◽

Vol 68 (8) ◽

pp. 4673-4680 ◽

Cited By ~ 35

Author(s):

Nicholas P. West ◽

Heidrun Jungnitz ◽

John T. Fitter ◽

Jason D. McArthur ◽

Carlos A. Guzmán ◽

...

Keyword(s):

Bacterial Resistance ◽

Bacterial Species ◽

Bordetella Bronchiseptica ◽

Insertion Mutant ◽

Wild Type ◽

Gene Encoding ◽

High Identity ◽

Lipopolysaccharide Biosynthesis

ABSTRACT The phosphoglucomutase (PGM)-encoding gene of Bordetella bronchiseptica is required for lipopolysaccharide (LPS) biosynthesis. An insertion mutant of the wild-type B. bronchiseptica strain BB7865 which disrupted LPS biosynthesis was created and characterized (BB7865pgm). Genetic analysis of the mutated gene showed it shares high identity with PGM genes of various bacterial species and forms part of an operon which also encompasses the gene encoding phosphoglucose isomerase. Functional assays for PGM revealed that enzyme activity is expressed in bothbvg-positive and bvg-negative strains ofB. bronchiseptica and is substantially reduced in BB7865pgm. Complementation of the mutated PGM gene with that from BB7865 restored the wild-type condition for all phenotypes tested. The ability of the mutant BB7865pgm to survive within J774.A1 cells was significantly reduced at 2 h (40% reduction) and 24 h (56% reduction) postinfection. BB7865pgm was also significantly attenuated in its ability to survive in vivo following intranasal infection of mice, being effectively cleared from the lungs within 4 days, whereas the wild-type strain persisted at least 35 days. The activities of superoxide dismutase, urease, and acid phosphatase were unaffected in the PGM-deficient strain. In contrast, the inability to produce wild-type LPS resulted in a reduced bacterial resistance to oxidative stress and a higher susceptibility to the antimicrobial peptide cecropin P.

Download Full-text

Evolutionarily conserved roles of Caenorhabditis elegans perilipin in lipolysis

10.7287/peerj.preprints.27467v1 ◽

2019 ◽

Author(s):

Filip Kaššák ◽

Ahmed A Chughtai ◽

Marta Kostrouchová

Keyword(s):

Neutral Lipids ◽

Physiological Role ◽

Hormone Sensitive Lipase ◽

Functional Connection ◽

Regulatory Pathways ◽

C Elegans ◽

Evolutionarily Conserved ◽

Eukaryotic Organisms

Neutral lipids and namely triacyl-glycerols (TAGs) are the prevalent excess energy storage molecules in all eukaryotic organisms. They are universally organized in active cytoplasmic organelles called lipid droplets (LDs) and their breakdown is performed and regulated in an evolutionarily conserved manner. In mammals, two distinct but inter-connected pathways are believed to mediate this catabolism: conventional cytoplasmic lipolysis with effector neutral lipases; and lipophagy, a specific kind of autophagy exploiting lysosomal acidic lipases. Central molecules in this regulation are LD-resident proteins, perilipins (PLINs). Our recent discovery of a sole PLIN orthologue in C. elegans offers a unique opportunity to study these regulatory pathways, provided that the interactive mechanisms are orthologous. To determine this, we employed classical genetics with genome editing tools and in vivo microscopy to provide three lines of evidence demonstrating the conserved role of the C. elegans perilipin. Firstly, we proved the common presence of a standard lipolytic apparatus on LDs. Next, we ascertained a functional connection between nematode PLIN-1 and the effector enzyme, hormone-sensitive lipase (HOSL-1). Finally, we identified lipophagy as a secondary lipolytic pathway, which is consistent with the mammalian model. Our data provide not only a proof of concept but also suggests interesting implications by questioning the physiological role of lipophagy in lipolysis.

Download Full-text

Prognostic Value and Biological Function of LRRN4 in Colorectal Cancer

10.21203/rs.3.rs-1010837/v1 ◽

2021 ◽

Author(s):

Cheng Xu ◽

Yulin Chen ◽

Feiwu Long ◽

Junman Ye ◽

Xue Li ◽

...

Keyword(s):

Colorectal Cancer ◽

Mrna Level ◽

Biological Significance ◽

Progression Free Survival ◽

Molecular Determinant ◽

Chinese Cohort ◽

Xenograft Models

Abstract Background: Several nervous and nerve-related biomarkers have been detected in colorectal cancer (CRC) and can contribute to the progression of CRC. However, the role of leucine-rich repeat neuronal 4 (LRRN4), a recently identified neurogenic marker, in CRC remains unclear. Methods: We examined the expression and the clinical outcomes of LRRN4 in CRC from TCGA-COREAD mRNA-sequencing datasets and immunohistochemistry on the Chinese cohort. Furthermore, the colony formation, flow cytometry, wound healing assay and mouse xenograft models were used to investigate the biological significance of LRRN4 in CRC cell lines with LRRN4 knockdown or overexpression in vitro and in vivo. In addition, weighted co-expression network analysis and DAVID were used to explore the potential molecular mechanism. Results: We provide the first evidence that LRRN4 expression, at both the protein and mRNA level, was remarkable high in CRC compared to controls and positively correlated with the clinical outcome of CRC patients. Specifically, LRRN4 was an independent prognostic factor for progression-free survival and overall survival in CRC patients. Further functional experiments showed that LRRN4 promoted cell proliferation, cell DNA synthesis and cell migration and inhibited apoptosis. Knockdown of LRRN4 can correspondingly decrease these effects in vitro and can significantly suppress the growth of xenografts. Several biological functions and signaling pathways were regulated by LRRN4, including proteoglycans in cancer, glutamatergic synapse, Ras, MAPK and PI3K.Conclusions: Our results suggest that LRRN4 could be a biological and molecular determinant to stratify CRC patients into distinct risk categories, and mechanistically, this is likely attributable to LRRN4 in regulating several malignant phenotypes of neoplastic cells via cancer-related pathways.

Download Full-text

Monitoring the 5-methoxycarbonylmethyl-2-thiouridine (mcm5s2U) modification in eukaryotic tRNAs via the gamma-toxin endonuclease

10.1101/253708 ◽

2018 ◽

Author(s):

Jenna M. Lentini ◽

Jillian Ramos ◽

Dragony Fu

Keyword(s):

Mammalian Cells ◽

Kluyveromyces Lactis ◽

Protein Translation ◽

Cell Types ◽

Eukaryotic Cell ◽

Wobble Position ◽

Eukaryotic Species ◽

Domains Of Life ◽

Toxin Assay ◽

Eukaryotic Organisms

ABSTRACTThe post-transcriptional modification of tRNA at the wobble position is a universal process occurring in all domains of life. In eukaryotes, the wobble uridine of particular tRNAs is transformed to the 5-methoxycarbonylmethyl-2-thiouridine (mcm5s2U) modification which is critical for proper mRNA decoding and protein translation. However, current methods to detect mcm5s2U are technically challenging and/or require specialized instrumental expertise. Here, we show that gamma-toxin endonuclease from the yeast Kluyveromyces lactis can be used as a probe for assaying mcm5s2U status in the tRNA of diverse eukaryotic organisms ranging from protozoans to mammalian cells. The assay couples the mcm5s2U-dependent cleavage of tRNA by gamma-toxin with standard molecular biology techniques such as Northern blot analysis or quantitative PCR to monitor mcm5s2U levels in multiple tRNA isoacceptors. The results gained from the gamma-toxin assay reveals the evolutionary conservation of the mcm5s2U modification across eukaryotic species. Moreover, we have employed the gamma-toxin assay to verify uncharacterized eukaryotic Trm9 and Trm112 homologs that catalyze the formation of mcm5s2U. These findings demonstrate the use of gamma-toxin as a detection method to monitor mcm5s2U status in diverse eukaryotic cell types for cellular, genetic and biochemical studies.

Download Full-text

Role of rpoS in Stress Survival and Virulence of Vibrio cholerae

Journal of Bacteriology ◽

10.1128/jb.180.4.773-784.1998 ◽

1998 ◽

Vol 180 (4) ◽

pp. 773-784 ◽

Cited By ~ 165

Author(s):

Fitnat H. Yildiz ◽

Gary K. Schoolnik

Keyword(s):

Vibrio Cholerae ◽

Genomic Library ◽

Bacterial Species ◽

Wild Type ◽

Reading Frame ◽

Infant Mouse ◽

Acid Protein ◽

Amino Acid Protein

ABSTRACT Vibrio cholerae is known to persist in aquatic environments under nutrient-limiting conditions. To analyze the possible involvement of the alternative sigma factor encoded byrpoS, which is shown to be important for survival during nutrient deprivation in several other bacterial species, a V. cholerae rpoS homolog was cloned by functional complementation of an Escherichia coli mutant by using a wild-type genomic library. Sequence analysis of the complementing clone revealed an 1.008-bp open reading frame which is predicted to encode a 336-amino-acid protein with 71 to 63% overall identity to other reported rpoS gene products. To determine the functional role of rpoS in V. cholerae, we inactivatedrpoS by homologous recombination. V. choleraestrains lacking rpoS are impaired in the ability to survive diverse environmental stresses, including exposure to hydrogen peroxide, hyperosmolarity, and carbon starvation. These results suggest that rpoS may be required for the persistence of V. cholerae in aquatic habitats. In addition, the rpoSmutation led to reduced production or secretion of hemagglutinin/protease. However, rpoS is not critical for in vivo survival, as determined by an infant mouse intestinal competition assay.

Download Full-text

Phosphorylation of the Anaphase Promoting Complex activator CDH1/FZR regulates the transition from Meiosis I to Meiosis II in mouse male germ cell

10.1101/2020.03.13.990127 ◽

2020 ◽

Author(s):

Nobuhiro Tanno ◽

Shinji Kuninaka ◽

Sayoko Fujimura ◽

Kaho Okamura ◽

Kazumasa Takemoto ◽

...

Keyword(s):

Cell Cycle ◽

Germ Cells ◽

Critical Role ◽

Biological Significance ◽

Mitotic Cell ◽

Anaphase Promoting Complex ◽

Meiosis I

SummaryCDH1/FZR is an activator of Anaphase promoting complex/Cyclosome (APC/C), best known for its role as E3 ubiquitin ligase that drives the cell cycle. APC/C activity is regulated by CDK-mediated phosphorylation of CDH1 during mitotic cell cycle. Although the critical role of CDH1 phosphorylation has been shown mainly in yeast and in vitro cell culture studies, its biological significance in mammalian tissues in vivo remained elusive. Here, we examined the in vivo role of CDH1 phosphorylation using a mouse model, in which non-phosphorylatable substitutions were introduced in the putative CDK-phosphorylation sites of CDH1. Although ablation of CDH1 phosphorylation did not show substantial consequences in mouse somatic tissues, it led to severe testicular defects resulting in male infertility. In the absence of CDH1 phosphorylation, male juvenile germ cells entered meiosis normally but skipped meiosis II producing diploid spermatid-like cells. In aged testis, male germ cells were overall abolished, showing Sertoli cell-only phenotype. The present study demonstrated that phosphorylation of CDH1 is required for temporal regulation of APC/C activity at the transition from meiosis I to meiosis II, and for spermatoginial stem cell maintenance, which raised an insight into the sexual dimorphism of CDH1-regulation in germ cells.

Download Full-text

MTORC2 is an in vivo hydrophobic motif kinase of S6 Kinase 1.

10.1101/2021.08.17.456612 ◽

2021 ◽

Author(s):

Sheikh Tahir Majeed ◽

Rabiya Majeed ◽

Muhammad Afzal Zargar ◽

Khurshid Iqbal Andrabi

Keyword(s):

Kinase Inhibitor ◽

Protein Translation ◽

S6 Kinase ◽

Downstream Effector ◽

Truncation Mutant ◽

Amino Acid Stretch ◽

Hydrophobic Motif ◽

Cell Growth And Proliferation

Ribosomal protein S6 kinase (S6K1), a major downstream effector molecule of mTORC1, regulates cell growth and proliferation via modulating protein translation and ribosomal biogenesis. We have previously identified eIF4E as an intermediate in transducing signals from mTORC1 to S6K1 and further demonstrated that the role of mTORC1 is restricted to relieving S6K1 auto-inhibition to allow hydrophobic motif (HM) phosphorylation of the enzyme for activation. These observations rule out the role of mTORC1 as an HM kinase of S6K1 and point towards the involvement of mTORC1 independent kinase in mediating HM phosphorylation. Here, we report mTORC2 as an in-vivo HM kinase of S6K1. We show that S6K1 truncation mutant, incapacitated to respond to mTORC1 signals, continues to display HM phosphorylation which remains sensitive towards mTOR kinase inhibitor-torin 1. Furthermore, we identify a highly conserved amino acid stretch in S6K1 responsible for mediating HM phosphorylation. We show that deletion of this stretch leads to HM dephosphorylation and subsequent in activation of the enzyme. We, therefore, propose a novel mechanism for S6K1 regulation where mTOR complex 1 and 2 act in tandem to activate the enzyme.

Download Full-text