Journal articles: 'LasR'

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Storey, Douglas G., Eva E. Ujack, Harvey R. Rabin, and Ian Mitchell. "Pseudomonas aeruginosa lasRTranscription Correlates with the Transcription of lasA,lasB, and toxA in Chronic Lung Infections Associated with Cystic Fibrosis." Infection and Immunity 66, no. 6 (June 1, 1998): 2521–28. http://dx.doi.org/10.1128/iai.66.6.2521-2528.1998.

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ABSTRACT The role of Pseudomonas aeruginosa quorum-sensing systems in the lung infections associated with cystic fibrosis (CF) has not been examined. The purpose of this study was to determine if genes regulated by the LasR-LasI quorum-sensing system were coordinately regulated by the P. aeruginosa populations during the lung infections associated with CF. We also wanted to ascertain if there was a relationship between the expression of lasR, a transcriptional regulator, and some P. aeruginosa virulence factors during these infections. We extracted RNAs from the bacterial populations of 131 sputa taken from 23 CF patients. These RNAs were blotted and hybridized with probes to P. aeruginosa lasA,lasB, and toxA. The hybridization signals from each probe were ranked, and the rankings were analyzed by a Spearman rank correlation to determine if there was an association between the population transcript accumulations for the three genes. The correlations between the transcript accumulation patterns of pairs of the genes suggested that lasA, lasB, andtoxA might be coordinately regulated during CF lung infections. To determine if this coordinate regulation might be due to regulation by LasR, we probed RNAs, extracted from 84 sputa, with thelasR, lasA, lasB, toxA, and algD probes. Statistical analysis indicated thatlasR transcript accumulation correlated tolasA, lasB, toxA, andalgD transcript accumulations. These results indicated thatlasR may at least partially regulate or be coordinately regulated with lasA, lasB, toxA, and algD during the lung infections associated with CF. These results also suggested that the LasR-LasI quorum-sensing system may control the expression of at least some virulence factors in the lungs of patients with CF.

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Kiratisin, Pattarachai, Kenneth D. Tucker, and Luciano Passador. "LasR, a Transcriptional Activator of Pseudomonas aeruginosa Virulence Genes, Functions as a Multimer." Journal of Bacteriology 184, no. 17 (September 1, 2002): 4912–19. http://dx.doi.org/10.1128/jb.184.17.4912-4919.2002.

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ABSTRACT The Pseudomonas aeruginosa LasR protein functions in concert with N-3-oxo-dodecanoyl-l-homoserine lactone (3O-C12-HSL) to coordinate the expression of target genes, including many genes that encode virulence factors, with cell density. We used a LexA-based protein interaction assay to demonstrate that LasR forms multimers only when 3O-C12-HSL is present. A series of LasR molecules containing internal deletions or substitutions in single, conserved amino acid residues indicated that the N-terminal portion of LasR is required for multimerization. Studies performed with these mutant versions of LasR demonstrated that the ability of LasR to multimerize correlates with its ability to function as a transcriptional activator of lasI, a gene known to be tightly regulated by the LasR-3O-C12-HSL regulatory system. A LasR molecule that carries a C-terminal deletion can function as a dominant-negative mutant in P. aeruginosa, as shown by its ability to decrease expression of lasB, another LasR-3O-C12-HSL target gene. Taken together, our data strongly support the hypothesis that LasR functions as a multimer in vivo.

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Kong, Kok-Fai, Suriya Ravi Jayawardena, Shalaka Dayaram Indulkar, Aimee del Puerto, Chong-Lek Koh, Niels Høiby, and Kalai Mathee. "Pseudomonas aeruginosa AmpR Is a Global Transcriptional Factor That Regulates Expression of AmpC and PoxB β-Lactamases, Proteases, Quorum Sensing, and Other Virulence Factors." Antimicrobial Agents and Chemotherapy 49, no. 11 (November 2005): 4567–75. http://dx.doi.org/10.1128/aac.49.11.4567-4575.2005.

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ABSTRACT In members of the family Enterobacteriaceae, ampC, which encodes a β-lactamase, is regulated by an upstream, divergently transcribed gene, ampR. However, in Pseudomonas aeruginosa, the regulation of ampC is not understood. In this study, we compared the characteristics of a P. aeruginosa ampR mutant, PAOampR, with that of an isogenic ampR + parent. The ampR mutation greatly altered AmpC production. In the absence of antibiotic, PAOampR expressed increased basal β-lactamase levels. However, this increase was not followed by a concomitant increase in the P ampC promoter activity. The discrepancy in protein and transcription analyses led us to discover the presence of another chromosomal AmpR-regulated β-lactamase, PoxB. We found that the expression of P. aeruginosa ampR greatly altered the β-lactamase production from ampC and poxB in Escherichia coli: it up-regulated AmpC but down-regulated PoxB activities. In addition, the constitutive P ampR promoter activity in PAOampR indicated that AmpR did not autoregulate in the absence or presence of inducers. We further demonstrated that AmpR is a global regulator because the strain carrying the ampR mutation produced higher levels of pyocyanin and LasA protease and lower levels of LasB elastase than the wild-type strain. The increase in LasA levels was positively correlated with the P lasA , P lasI , and P lasR expression. The reduction in the LasB activity was positively correlated with the P rhlR expression. Thus, AmpR plays a dual role, positively regulating the ampC, lasB, and rhlR expression levels and negatively regulating the poxB, lasA, lasI, and lasR expression levels.

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Kostylev, Maxim, Daniel Y. Kim, Nicole E. Smalley, Indraneel Salukhe, E. Peter Greenberg, and Ajai A. Dandekar. "Evolution of thePseudomonas aeruginosaquorum-sensing hierarchy." Proceedings of the National Academy of Sciences 116, no. 14 (March 8, 2019): 7027–32. http://dx.doi.org/10.1073/pnas.1819796116.

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The bacterial pathogenPseudomonas aeruginosaactivates expression of many virulence genes in a cell density-dependent manner by using an intricate quorum-sensing (QS) network. QS inP. aeruginosainvolves two acyl-homoserine-lactone circuits, LasI-LasR and RhlI-RhlR. LasI-LasR is required to activate many genes including those coding for RhlI-RhlR.P. aeruginosacauses chronic infections in the lungs of people with cystic fibrosis (CF). In these infections, LasR mutants are common, butrhlR-rhlIexpression has escaped LasR regulation in many CF isolates. To better understand the evolutionary trajectory ofP. aeruginosaQS in chronic infections, we grew LasR mutants of the well-studiedP. aeruginosastrain, PAO1, in conditions that recapitulate an environment where QS signal synthesis by other bacteria might still occur. When QS is required for growth, addition of the RhlI product butyryl-homoserine lactone (C4-HSL), or bacteria that produce C4-HSL, to LasR mutants results in the rapid emergence of a population with a LasR-independent RhlI-RhlR QS system. These evolved populations exhibit subsequent growth without added C4-HSL. The variants that emerge have mutations inmexT, which codes for a transcription factor that controls expression of multiple genes. LasR-MexT mutants have a competitive advantage over both the parent LasR mutant and a LasR-MexT-RhlR mutant. Our findings suggest a plausible evolutionary trajectory for QS inP. aeruginosaCF infections where LasR mutants arise during infection, but because these mutants are surrounded by C4-HSL–producingP. aeruginosa,variants rewired to have a LasR-independent RhlIR system quickly emerge.

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Anderson, Ronda M., Chad A. Zimprich, and Lynn Rust. "A Second Operator Is Involved in Pseudomonas aeruginosa Elastase (lasB) Activation." Journal of Bacteriology 181, no. 20 (October 15, 1999): 6264–70. http://dx.doi.org/10.1128/jb.181.20.6264-6270.1999.

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ABSTRACT Pseudomonas aeruginosa LasB elastase gene (lasB) transcription is controlled by the two-component quorum-sensing system of LasR, and the autoinducer, 3OC12-HSL (N-3-[oxododecanoyl]homoserine lactone). LasR and 3OC12-HSL-mediated lasBactivation requires a functional operator sequence (OP1) in thelasB promoter region. Optimal activation oflasB, however, requires a second sequence of 70% identity to OP1, named OP2, located 43 bp upstream of OP1. In this study, we used sequence substitutions and insertion mutations inlasBp-lacZ fusion plasmids to explore the role of OP2 in lasB activation. Our results demonstrate that (i) OP1 and OP2 synergistically mediate lasB activation; (ii) OP2, like OP1, responds to LasR and 3OC12-HSL; and (iii) the putative autoinducer-binding domain of LasR is not required for synergistic activation from OP1 and OP2.

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Cabrol, Ségolène, Anne Olliver, Gerald B. Pier, Antoine Andremont, and Raymond Ruimy. "Transcription of Quorum-Sensing System Genes inClinical and Environmental Isolates of Pseudomonasaeruginosa." Journal of Bacteriology 185, no. 24 (December 15, 2003): 7222–30. http://dx.doi.org/10.1128/jb.185.24.7222-7230.2003.

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ABSTRACT Quorum sensing (QS)-based transcriptional responses in Pseudomonas aeruginosa have been defined on the basis of increases in transcript levels of QS-controlled genes such as lasB and aprA following the hierarchical transcriptional increases of central controllers such as the lasR gene. These increases occur at high bacterial concentrations such as early-stationary-phase growth in vitro. However, the extent to which the increases occur in a variety of clinical and environmental isolates has not been determined nor is there extensive information on allelic variation in lasR genes. An analysis of the sequences of the lasR gene among 66 clinical and environmental isolates showed that 81% have a sequence either identical to that of strain PAO1 or with a silent mutation, 15% have nucleotide changes resulting in amino acid changes, and 5% have an insertion sequence in the lasR gene. Using real-time PCR to quantify transcript levels of lasR, lasB, and aprA in the early log and early stationary phases among 35 isolates from bacteremia and pneumonia cases and the environment, we found most (33 of 35) strains had increases in lasR transcripts in early stationary phase but with a very wide range of final transcript levels per cell. There was a strong correlation (r 2 = 0.84) between early-log- and early-stationary-phase transcript levels in all strains, but this finding remained true only for the 50% of strains above the median level of lasR found in early log phase. There were significant (P < 0.05) but weak-to-modest correlations of lasR transcript levels with aprA (r2= 0.2) and lasB (r 2 = 0.5) transcript levels, but again this correlation occurred only in the 50% of P. aeruginosa strains with the highest levels of lasR transcripts in early stationary phase. There were no differences in distribution of lasR alleles among the bacteremia, pneumonia, or environmental isolates. Overall, only about 50% of P. aeruginosa strains from clinical and environmental sources show a lasR-dependent increase in the transcription of aprA and lasB genes, indicating that for about 50% of clinical isolates this regulatory system may not play a significant role in pathogenesis.

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Takaya, Akiko, Fumiaki Tabuchi, Hiroko Tsuchiya, Emiko Isogai, and Tomoko Yamamoto. "Negative Regulation of Quorum-Sensing Systems in Pseudomonas aeruginosa by ATP-Dependent Lon Protease." Journal of Bacteriology 190, no. 12 (April 11, 2008): 4181–88. http://dx.doi.org/10.1128/jb.01873-07.

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ABSTRACT Lon protease, a member of the ATP-dependent protease family, regulates numerous cellular systems by degrading specific substrates. Here, we demonstrate that Lon is involved in the regulation of quorum-sensing (QS) signaling systems in Pseudomonas aeruginosa, an opportunistic human pathogen. The organism has two acyl-homoserine lactone (HSL)-mediated QS systems, LasR/LasI and RhlR/RhlI. Many reports have demonstrated that these two systems are regulated and interconnected by global regulators. We found that lon-disrupted cells overproduce pyocyanin, the biosynthesis of which depends on the RhlR/RhlI system, and show increased levels of a transcriptional regulator, RhlR. The QS systems are organized hierarchically: the RhlR/RhlI system is subordinate to LasR/LasI. To elucidate the mechanism by which Lon negatively regulates RhlR/RhlI, we examined the effect of lon disruption on the LasR/LasI system. We found that Lon represses the expression of LasR/LasI by degrading LasI, an HSL synthase, leading to negative regulation of the RhlR/RhlI system. RhlR/RhlI was also shown to be regulated by Lon independently of LasR/LasI via regulation of RhlI, an HSL synthase. In view of these findings, it is suggested that Lon protease is a powerful negative regulator of both HSL-mediated QS systems in P. aeruginosa.

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Whiteley, Marvin, and E. P. Greenberg. "Promoter Specificity Elements in Pseudomonas aeruginosa Quorum-Sensing-Controlled Genes." Journal of Bacteriology 183, no. 19 (October 1, 2001): 5529–34. http://dx.doi.org/10.1128/jb.183.19.5529-5534.2001.

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ABSTRACT The LasR-dependent and RhlR-dependent quorum-sensing systems are global regulators of gene expression in Pseudomonas aeruginosa. Previous studies have demonstrated that promoter elements of the quorum-sensing-controlled genes lasB andhcnABC are important in density-dependent regulation. We have identified LasR- and RhlR-dependent determinants in promoters of quorum-sensing-controlled genes qsc102, qsc117 (acpP), and qsc131 (phzA to -G) by in silico, deletion, point-mutational, and primer extension analyses. Each of these genes (in addition tolasI and rsaL) is activated by LasR, and qsc117 and qsc131 also respond to RhlR. Point mutations in the promoters of the LasR-specific gene, qsc102, relax specificity so that this promoter can respond to RhlR in addition to LasR. Our findings indicate that quorum-sensing-controlled promoters in P. aeruginosa are either specific for LasR or respond to both LasR and RhlR and that critical bases in the promoter elements determine specificity.

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Müh, Ute, Martin Schuster, Roger Heim, Ashvani Singh, Eric R. Olson, and E. Peter Greenberg. "Novel Pseudomonas aeruginosa Quorum-Sensing Inhibitors Identified in an Ultra-High-Throughput Screen." Antimicrobial Agents and Chemotherapy 50, no. 11 (September 11, 2006): 3674–79. http://dx.doi.org/10.1128/aac.00665-06.

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ABSTRACT The opportunistic pathogen Pseudomonas aeruginosa has two complete acyl-homoserine lactone (acyl-HSL) signaling systems, LasR-LasI and RhlR-RhlI. LasI catalyzes the synthesis of N-3-oxododecanoyl homoserine lactone (3OC12-HSL), and LasR is a transcription factor that requires 3OC12-HSL as a ligand. RhlI catalyzes the synthesis of N-butanoyl homoserine lactone (C4), and RhlR is a transcription factor that responds to C4. LasR and RhlR control the transcription of hundreds of P. aeruginosa genes, many of which are critical virulence determinants, and LasR is required for RhlR function. We developed an ultra-high-throughput cell-based assay to screen a library of approximately 200,000 compounds for inhibitors of LasR-dependent gene expression. Although the library contained a large variety of chemical structures, the two best inhibitors resembled the acyl-homoserine lactone molecule that normally binds to LasR. One compound, a tetrazole with a 12-carbon alkyl tail designated PD12, had a 50% inhibitory concentration (IC50) of 30 nM. The second compound, V-06-018, had an IC50 of 10 μM and is a phenyl ring with a 12-carbon alkyl tail. A microarray analysis showed that both compounds were general inhibitors of quorum sensing, i.e., the expression levels of most LasR-dependent genes were affected. Both compounds also inhibited the production of two quorum-sensing-dependent virulence factors, elastase and pyocyanin. These compounds should be useful for studies of LasR-dependent gene regulation and might serve as scaffolds for the identification of new quorum-sensing modulators.

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Lequette, Yannick, Joon-Hee Lee, Fouzia Ledgham, Andrée Lazdunski, and E. Peter Greenberg. "A Distinct QscR Regulon in the Pseudomonas aeruginosa Quorum-Sensing Circuit." Journal of Bacteriology 188, no. 9 (May 1, 2006): 3365–70. http://dx.doi.org/10.1128/jb.188.9.3365-3370.2006.

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ABSTRACT The opportunistic pathogen Pseudomonas aeruginosa possesses two complete acyl-homoserine lactone (acyl-HSL) signaling systems. One system consists of LasI and LasR, which generate a 3-oxododecanoyl-homoserine lactone signal and respond to that signal, respectively. The other system is RhlI and RhlR, which generate butanoyl-homoserine lactone and respond to butanoyl-homoserine lactone, respectively. These quorum-sensing systems control hundreds of genes. There is also an orphan LasR-RhlR homolog, QscR, for which there is no cognate acyl-HSL synthetic enzyme. We previously reported that a qscR mutant is hypervirulent and showed that QscR transiently represses a few quorum-sensing-controlled genes. To better understand the role of QscR in P. aeruginosa gene regulation and to better understand the relationship between QscR, LasR, and RhlR control of gene expression, we used transcription profiling to identify a QscR-dependent regulon. Our analysis revealed that QscR activates some genes and represses others. Some of the repressed genes are not regulated by the LasR-I or RhlR-I systems, while others are. The LasI-generated 3-oxododecanoyl-homoserine lactone serves as a signal molecule for QscR. Thus, QscR appears to be an integral component of the P. aeruginosa quorum-sensing circuitry. QscR uses the LasI-generated acyl-homoserine lactone signal and controls a specific regulon that overlaps with the already overlapping LasR- and RhlR-dependent regulons.

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de Kievit, Teresa, Patrick C. Seed, Jonathon Nezezon, Luciano Passador, and Barbara H. Iglewski. "RsaL, a Novel Repressor of Virulence Gene Expression in Pseudomonas aeruginosa." Journal of Bacteriology 181, no. 7 (April 1, 1999): 2175–84. http://dx.doi.org/10.1128/jb.181.7.2175-2184.1999.

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ABSTRACT As components of a Pseudomonas aeruginosaquorum-sensing system, LasR and PAI-1 globally regulate expression of multiple virulence determinants, as well as the second P. aeruginosa quorum-sensing system. To date, no information exists on negative regulation of the quorum-sensing cascade in P. aeruginosa. Here we describe a novel gene, rsaL, which is located downstream from lasR and transcribed antisense relative to lasR. In P. aeruginosa,overexpression of rsaL results in reduced lasBexpression and decreased elastase activity. With the use of a six-His protein fusion system, we demonstrate that rsaL encodes an 11-kDa protein. Direct quantitation of PAI-1 levels in cultures and studies utilizing Escherichia coli lambda lysogens carryinglacZ transcriptional fusions reveal that RsaL specifically represses transcription of the PAI-1 autoinducer synthase gene,lasI. RsaL’s repressive effect on lasI and the associated decrease in elastase activity have important implications for the expression of all LasR–PAI-1-dependent virulence genes and the overall pathogenicity of P. aeruginosa.

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Wang, Mengjia, Lu Zhao, Hao Wu, Chaoyue Zhao, Qianhong Gong, and Wengong Yu. "Cladodionen Is a Potential Quorum Sensing Inhibitor Against Pseudomonas aeruginosa." Marine Drugs 18, no. 4 (April 10, 2020): 205. http://dx.doi.org/10.3390/md18040205.

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Pseudomonas aeruginosa is an opportunistic pathogen using virulence factors and biofilm regulated by quorum sensing (QS) systems to infect patients and protect itself from environmental stress and antibiotics. Interfering with QS systems is a novel approach to combat P. aeruginosa infections without killing the bacteria, meaning that it is much harder for bacteria to develop drug resistance. A marine fungus Cladosporium sp. Z148 with anti-QS activity was obtained from Jiaozhou Bay, China. Cladodionen, a novel QS inhibitor, was isolated from the extracts of this fungus. Cladodionen had a better inhibitory effect than pyocyanin on the production of elastase and rhamnolipid. It also inhibited biofilm formation and motilities. The mRNA expressions of QS-related genes, including receptor proteins (lasR, rhlR and pqsR), autoinducer synthases (lasI, rhlI and pqsA) and virulence factors (lasB and rhlA) were down-regulated by cladodionen. Molecular docking analysis showed that cladodionen had better binding affinity to LasR and PqsR than natural ligands. Moreover, the binding affinity of cladodionen to LasR was higher than to PqsR. Cladodionen exhibits potential as a QS inhibitor against P. aeruginosa, and its structure–activity relationships should be further studied to illustrate the mode of action, optimize its structure and improve anti-QS activity.

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Zhao, Rui, Myles Marshall, Elvin A. Alemán, Rajan Lamichhane, Andrew Feig, and David Rueda. "Laser-Assisted Single-Molecule Refolding (LASR)." Biophysical Journal 99, no. 6 (September 2010): 1925–31. http://dx.doi.org/10.1016/j.bpj.2010.07.019.

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Vandeputte, Olivier M., Martin Kiendrebeogo, Tsiry Rasamiravaka, Caroline Stévigny, Pierre Duez, Sanda Rajaonson, Billo Diallo, Adeline Mol, Marie Baucher, and Mondher El Jaziri. "The flavanone naringenin reduces the production of quorum sensing-controlled virulence factors in Pseudomonas aeruginosa PAO1." Microbiology 157, no. 7 (July 1, 2011): 2120–32. http://dx.doi.org/10.1099/mic.0.049338-0.

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Preliminary screening of the Malagasy plant Combretum albiflorum for compounds attenuating the production of quorum sensing (QS)-controlled virulence factors in bacteria led to the identification of active fractions containing flavonoids. In the present study, several flavonoids belonging to the flavone, flavanone, flavonol and chalcone structural groups were screened for their capacity to reduce the production of QS-controlled factors in the opportunistic pathogen Pseudomonas aeruginosa (strain PAO1). Flavanones (i.e. naringenin, eriodictyol and taxifolin) significantly reduced the production of pyocyanin and elastase in P. aeruginosa without affecting bacterial growth. Consistently, naringenin and taxifolin reduced the expression of several QS-controlled genes (i.e. lasI, lasR, rhlI, rhlR, lasA, lasB, phzA1 and rhlA) in P. aeruginosa PAO1. Naringenin also dramatically reduced the production of the acylhomoserine lactones N-(3-oxododecanoyl)-l-homoserine lactone (3-oxo-C12-HSL) and N-butanoyl-l-homoserine lactone (C4-HSL), which is driven by the lasI and rhlI gene products, respectively. In addition, using mutant strains deficient for autoinduction (ΔlasI and ΔrhlI) and LasR- and RhlR-based biosensors, it was shown that QS inhibition by naringenin not only is the consequence of a reduced production of autoinduction compounds but also results from a defect in the proper functioning of the RlhR–C4-HSL complex. Widely distributed in the plant kingdom, flavonoids are known for their numerous and determinant roles in plant physiology, plant development and in the success of plant–rhizobia interactions, but, as shown here, some of them also have a role as inhibitors of the virulence of pathogenic bacteria by interfering with QS mechanisms.

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Rampioni, Giordano, Iris Bertani, Elisabetta Zennaro, Fabio Polticelli, Vittorio Venturi, and Livia Leoni. "The Quorum-Sensing Negative Regulator RsaL of Pseudomonas aeruginosa Binds to the lasI Promoter." Journal of Bacteriology 188, no. 2 (January 15, 2006): 815–19. http://dx.doi.org/10.1128/jb.188.2.815-819.2006.

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ABSTRACT A mutation in the rsaL gene of Pseudomonas aeruginosa produces dramatically higher amounts of N-acyl homoserine lactone with respect to the wild type, highlighting the key role of this negative regulator in controlling quorum sensing (QS) in this opportunistic pathogen. The DNA binding site of the RsaL protein on the rsaL-lasI bidirectional promoter partially overlaps the binding site of the LasR protein, consistent with the hypothesis that RsaL and LasR could be in binding competition on this promoter. This is the first direct demonstration that RsaL acts as a QS negative regulator by binding to the lasI promoter.

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Heurlier, Karin, Valérie Dénervaud, Marisa Haenni, Lionel Guy, Viji Krishnapillai, and Dieter Haas. "Quorum-Sensing-Negative (lasR) Mutants of Pseudomonas aeruginosa Avoid Cell Lysis and Death." Journal of Bacteriology 187, no. 14 (July 2005): 4875–83. http://dx.doi.org/10.1128/jb.187.14.4875-4883.2005.

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ABSTRACT In Pseudomonas aeruginosa, N-acylhomoserine lactone signals regulate the expression of several hundreds of genes, via the transcriptional regulator LasR and, in part, also via the subordinate regulator RhlR. This regulatory network termed quorum sensing contributes to the virulence of P. aeruginosa as a pathogen. The fact that two supposed PAO1 wild-type strains from strain collections were found to be defective for LasR function because of independent point mutations in the lasR gene led to the hypothesis that loss of quorum sensing might confer a selective advantage on P. aeruginosa under certain environmental conditions. A convenient plate assay for LasR function was devised, based on the observation that lasR mutants did not grow on adenosine as the sole carbon source because a key degradative enzyme, nucleoside hydrolase (Nuh), is positively controlled by LasR. The wild-type PAO1 and lasR mutants showed similar growth rates when incubated in nutrient yeast broth at pH 6.8 and 37°C with good aeration. However, after termination of growth during 30 to 54 h of incubation, when the pH rose to ≥ 9, the lasR mutants were significantly more resistant to cell lysis and death than was the wild type. As a consequence, the lasR mutant-to-wild-type ratio increased about 10-fold in mixed cultures incubated for 54 h. In a PAO1 culture, five consecutive cycles of 48 h of incubation sufficed to enrich for about 10% of spontaneous mutants with a Nuh− phenotype, and five of these mutants, which were functionally complemented by lasR + , had mutations in lasR. The observation that, in buffered nutrient yeast broth, the wild type and lasR mutants exhibited similar low tendencies to undergo cell lysis and death suggests that alkaline stress may be a critical factor providing a selective survival advantage to lasR mutants.

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Thaden, Joshua T., Stephen Lory, and Timothy S. Gardner. "Quorum-Sensing Regulation of a Copper Toxicity System in Pseudomonas aeruginosa." Journal of Bacteriology 192, no. 10 (March 16, 2010): 2557–68. http://dx.doi.org/10.1128/jb.01528-09.

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ABSTRACT The LasR/LasI quorum-sensing system in Pseudomonas aeruginosa influences global gene expression and mediates pathogenesis. In this study, we show that the quorum-sensing system activates, via the transcriptional regulator PA4778, a copper resistance system composed of 11 genes. The quorum-sensing global regulator LasR was recently shown to directly activate transcription of PA4778, a cueR homolog and a MerR-type transcriptional regulator. Using molecular genetic methods and bioinformatics, we verify the interaction of LasR with the PA4778 promoter and further demonstrate the LasR binding site. We also identify a putative PA4778 binding motif and show that the protein directly binds to and activates five promoters controlling the expression of 11 genes—PA3519 to -15, PA3520, mexPQ-opmE, PA3574.1, and cueA, a virulence factor in a murine model. Using gene disruptions, we show that PA4778, along with 7 of 11 gene targets of PA4778, increases the sensitivity of P. aeruginosa to elevated copper concentrations. This work identifies a cellular function for PA4778 and four other previously unannotated genes (PA3515, PA3516, PA3517, and PA3518) and suggests a potential role for copper in the quorum response. We propose to name PA4778 cueR.

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Clay, Michelle E., John H. Hammond, Fangfang Zhong, Xiaolei Chen, Caitlin H. Kowalski, Alexandra J. Lee, Monique S. Porter, et al. "Pseudomonas aeruginosa lasR mutant fitness in microoxia is supported by an Anr-regulated oxygen-binding hemerythrin." Proceedings of the National Academy of Sciences 117, no. 6 (January 24, 2020): 3167–73. http://dx.doi.org/10.1073/pnas.1917576117.

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Pseudomonas aeruginosa strains with loss-of-function mutations in the transcription factor LasR are frequently encountered in the clinic and the environment. Among the characteristics common to LasR-defective (LasR−) strains is increased activity of the transcription factor Anr, relative to their LasR+ counterparts, in low-oxygen conditions. One of the Anr-regulated genes found to be highly induced in LasR− strains was PA14_42860 (PA1673), which we named mhr for microoxic hemerythrin. Purified P. aeruginosa Mhr protein contained the predicted di-iron center and bound molecular oxygen with an apparent Kd of ∼1 µM. Both Anr and Mhr were necessary for fitness in lasR+ and lasR mutant strains in colony biofilms grown in microoxic conditions, and the effects were more striking in the lasR mutant. Among genes in the Anr regulon, mhr was most closely coregulated with the Anr-controlled high-affinity cytochrome c oxidase genes. In the absence of high-affinity cytochrome c oxidases, deletion of mhr no longer caused a fitness disadvantage, suggesting that Mhr works in concert with microoxic respiration. We demonstrate that Anr and Mhr contribute to LasR− strain fitness even in biofilms grown in normoxic conditions. Furthermore, metabolomics data indicate that, in a lasR mutant, expression of Anr-regulated mhr leads to differences in metabolism in cells grown on lysogeny broth or artificial sputum medium. We propose that increased Anr activity leads to higher levels of the oxygen-binding protein Mhr, which confers an advantage to lasR mutants in microoxic conditions.

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McCready, Amelia R., Jon E. Paczkowski, Brad R. Henke, and Bonnie L. Bassler. "Structural determinants driving homoserine lactone ligand selection in thePseudomonas aeruginosaLasR quorum-sensing receptor." Proceedings of the National Academy of Sciences 116, no. 1 (December 17, 2018): 245–54. http://dx.doi.org/10.1073/pnas.1817239116.

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Quorum sensing is a cell–cell communication process that bacteria use to orchestrate group behaviors. Quorum sensing is mediated by signal molecules called autoinducers. Autoinducers are often structurally similar, raising questions concerning how bacteria distinguish among them. Here, we use thePseudomonas aeruginosaLasR quorum-sensing receptor to explore signal discrimination. The cognate autoinducer, 3OC12homoserine lactone (3OC12HSL), is a more potent activator of LasR than other homoserine lactones. However, other homoserine lactones can elicit LasR-dependent quorum-sensing responses, showing that LasR displays ligand promiscuity. We identify mutants that alter which homoserine lactones LasR detects. Substitution at residue S129 decreases the LasR response to 3OC12HSL, while enhancing discrimination against noncognate autoinducers. Conversely, the LasR L130F mutation increases the potency of 3OC12HSL and other homoserine lactones. We solve crystal structures of LasR ligand-binding domains complexed with noncognate autoinducers. Comparison with existing structures reveals that ligand selectivity/sensitivity is mediated by a flexible loop near the ligand-binding site. We show that LasR variants with modified ligand preferences exhibit altered quorum-sensing responses to autoinducers in vivo. We suggest that possessing some ligand promiscuity endows LasR with the ability to optimally regulate quorum-sensing traits.

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Hennemann, Lisa C., Shantelle L. LaFayette, Julien K. Malet, Perrine Bortolotti, Tianxiao Yang, Geoffrey A. McKay, Daniel Houle, Danuta Radzioch, Simon Rousseau, and Dao Nguyen. "LasR-deficient Pseudomonas aeruginosa variants increase airway epithelial mICAM-1 expression and enhance neutrophilic lung inflammation." PLOS Pathogens 17, no. 3 (March 10, 2021): e1009375. http://dx.doi.org/10.1371/journal.ppat.1009375.

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Pseudomonas aeruginosa causes chronic airway infections, a major determinant of lung inflammation and damage in cystic fibrosis (CF). Loss-of-function lasR mutants commonly arise during chronic CF infections, are associated with accelerated lung function decline in CF patients and induce exaggerated neutrophilic inflammation in model systems. In this study, we investigated how lasR mutants modulate airway epithelial membrane bound ICAM-1 (mICAM-1), a surface adhesion molecule, and determined its impact on neutrophilic inflammation in vitro and in vivo. We demonstrated that LasR-deficient strains induce increased mICAM-1 levels in airway epithelial cells compared to wild-type strains, an effect attributable to the loss of mICAM-1 degradation by LasR-regulated proteases and associated with enhanced neutrophil adhesion. In a subacute airway infection model, we also observed that lasR mutant-infected mice displayed greater airway epithelial ICAM-1 expression and increased neutrophilic pulmonary inflammation. Our findings provide new insights into the intricate interplay between lasR mutants, LasR-regulated proteases and airway epithelial ICAM-1 expression, and reveal a new mechanism involved in the exaggerated inflammatory response induced by lasR mutants.

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Xuan, Guanhua, Chuanjuan Lv, Huangwei Xu, Kai Li, Huaiwei Liu, Yongzhen Xia, and Luying Xun. "Sulfane Sulfur Regulates LasR-Mediated Quorum Sensing and Virulence in Pseudomonas aeruginosa PAO1." Antioxidants 10, no. 9 (September 21, 2021): 1498. http://dx.doi.org/10.3390/antiox10091498.

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Sulfane sulfur, such as inorganic and organic polysulfide (HSn− and RSn−, n > 2), is a common cellular component, produced either from hydrogen sulfide oxidation or cysteine metabolism. In Pseudomonas aeruginosa PAO1, LasR is a quorum sensing master regulator. After binding its autoinducer, LasR binds to its target DNA to activate the transcription of a suite of genes, including virulence factors. Herein, we report that the production of hydrogen sulfide and sulfane sulfur were positively correlated in P. aeruginosa PAO1, and sulfane sulfur was able to modify LasR, which generated Cys188 persulfide and trisulfide and produced a pentasulfur link between Cys201 and Cys203. The modifications did not affect LasR binding to its target DNA site, but made it several-fold more effective than unmodified LasR in activating transcription in both in vitro and in vivo assays. On the contrary, H2O2 inactivates LasR via producing a disulfide bond between Cys201 and Cys203. P. aeruginosa PAO1 had a high cellular sulfane sulfur and high LasR activity in the mid log phase and early stationary phase, but a low sulfane sulfur and low LasR activity in the declination phase. Thus, sulfane sulfur is a new signaling factor in the bacterium, adding another level of control over LasR-mediated quorum sensing and turning down the activity in old cells.

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Hennemann, Lisa C., and Dao Nguyen. "LasR-regulated proteases in acute vs. chronic lung infection: a double-edged sword." Microbial Cell 8, no. 7 (July 5, 2021): 161–63. http://dx.doi.org/10.15698/mic2021.07.755.

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Pseudomonas aeruginosa is a gram-negative opportunistic pathogen capable of causing both acute and chronic infections, particularly in individuals with compromised host defenses. The quorum sensing transcriptional activator LasR is widely recognized for its role in regulating the expression of acute virulence factors, notably several secreted proteases which cause direct host damage and subvert host immunity in acute infections. Paradoxically, lung infections caused by LasR-deficient variants, which are found in at least a third of cystic fibrosis (CF) patients with chronic P. aeruginosa infections, are associated with accelerated lung disease and increased markers of inflammation compared to infections caused by strains with a functional LasR system. While the loss of LasR function often (although not always) results in impaired production of LasR-controlled acute virulence factors, the implication of this pathoadaptation on host-pathogen interactions and chronic disease pathology is less well recognized. We recently observed that loss of LasR function in lasR variants, which results in impaired secreted protease production, led to increased expression of the membrane-bound surface adhesion molecule mICAM-1 in the airway epithelium, and increased neutrophilic inflammation. Specifically, human airway epithelial cells stimulated with lasR variants had higher mICAM-1 expression and greater neutrophil binding in vitro compared to stimulation with wild-type P. aeruginosa. In a subacute non-lethal P. aeruginosa lung infection model, lasR variant infection also induced higher mICAM-1 expression in the murine airway epithelium and was associated with increased neutrophilic pulmonary inflammation in vivo. Here, we discuss how (loss of) LasR function and LasR-regulated proteases affect host immunity, inflammation and tissue pathology in acute vs. chronic P. aeruginosa lung infection.

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Balasubramanian, Deepak, Kok-Fai Kong, Suriya Ravi Jayawardena, Sixto Manuel Leal, Robert Todd Sautter, and Kalai Mathee. "Co-regulation of β-lactam resistance, alginate production and quorum sensing in Pseudomonas aeruginosa." Journal of Medical Microbiology 60, no. 2 (February 1, 2011): 147–56. http://dx.doi.org/10.1099/jmm.0.021600-0.

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Development of β-lactam resistance, production of alginate and modulation of virulence factor expression that alters host immune responses are the hallmarks of chronic Pseudomonas aeruginosa infection in cystic fibrosis patients. In this study, we propose that a co-regulatory network exists between these mechanisms. We compared the promoter activities of ampR, algT/U, lasR, lasI, rhlR, rhlI and lasA genes, representing the β-lactam antibiotic resistance master regulatory gene, the alginate switch operon, the las and rhl quorum-sensing (QS) genes, and the LasA staphylolytic protease, respectively. Four isogenic P. aeruginosa strains, the prototypic Alg− PAO1, Alg− PAOampR, the mucoid Alg+ PAOmucA22 (Alg+ PDO300) and Alg+ PAOmucA22ampR (Alg+ PDOampR) were used. We found that in the presence of AmpR regulator and β-lactam antibiotic, the extracytoplasmic function sigma factor AlgT/U positively regulated P ampR , whereas AmpR negatively regulated P algT/U . On the basis of this finding we suggest the presence of a negative feedback loop to limit algT/U expression. In addition, the functional AlgT/U caused a significant decrease in the expression of QS genes, whereas loss of ampR only resulted in increased P lasI and P lasR transcription. The upregulation of the las QS system is likely to be responsible for the increased lasA promoter and the LasA protease activities in Alg− PAOampR and Alg+ PDOampR. The enhanced expression of virulence factors in the ampR strains correlated with a higher rate of Caenorhabditis elegans paralysis. Hence, this study shows that the loss of ampR results in increased virulence, and is indicative of the existence of a co-regulatory network between β-lactam resistance, alginate production, QS and virulence factor production, with AmpR playing a central role.

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Carlson, Edward A., Pierre-Philippe J. Beaujean, and Edgar An. "Location-Aware Source Routing Protocol for Underwater Acoustic Networks of AUVs." Journal of Electrical and Computer Engineering 2012 (2012): 1–18. http://dx.doi.org/10.1155/2012/765924.

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Acoustic networks of autonomous underwater vehicles (AUVs) cannot typically rely on protocols intended for terrestrial radio networks. This work describes a new location-aware source routing (LASR) protocol shown to provide superior network performance over two commonly used network protocols—flooding and dynamic source routing (DSR)—in simulation studies of underwater acoustic networks of AUVs. LASR shares some features with DSR but also includes an improved link/route metric and a node tracking system. LASR also replaces DSR's shortest-path routing with the expected transmission count (ETX) metric. This allows LASR to make more informed routing decisions, which greatly increases performance compared to DSR. Provision for a node tracking system is another novel addition: using the time-division multiple access (TDMA) feature of the simulated acoustic modem, LASR includes a tracking system that predicts node locations, so that LASR can proactively respond to topology changes. LASR delivers 2-3 times as many messages as flooding in 72% of the simulated missions and delivers 2–4 times as many messages as DSR in 100% of the missions. In 67% of the simulated missions, LASR delivers messages requiring multiple hops to cross the network with 2–5 times greater reliability than flooding or DSR.

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Rajamani, Sathish, Wolfgang D. Bauer, Jayne B. Robinson, John M. Farrow, Everett C. Pesci, Max Teplitski, Mengsheng Gao, Richard T. Sayre, and Donald A. Phillips. "The Vitamin Riboflavin and Its Derivative Lumichrome Activate the LasR Bacterial Quorum-Sensing Receptor." Molecular Plant-Microbe Interactions® 21, no. 9 (September 2008): 1184–92. http://dx.doi.org/10.1094/mpmi-21-9-1184.

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Many bacteria use quorum sensing (QS) as an intercellular signaling mechanism to regulate gene expression in local populations. Plant and algal hosts, in turn, secrete compounds that mimic bacterial QS signals, allowing these hosts to manipulate QS-regulated gene expression in bacteria. Lumichrome, a derivative of the vitamin riboflavin, was purified and chemically identified from culture filtrates of the alga Chlamydomonas as a QS signal-mimic compound capable of stimulating the Pseudomonas aeruginosa LasR QS receptor. LasR normally recognizes the N-acyl homoserine lactone (AHL) signal, N-3-oxo-dodecanoyl homoserine lactone. Authentic lumichrome and riboflavin stimulated the LasR receptor in bioassays and lumichrome activated LasR in gel shift experiments. Amino acid substitutions in LasR residues required for AHL binding altered responses to both AHLs and lumichrome or riboflavin. These results and docking studies indicate that the AHL binding pocket of LasR recognizes both AHLs and the structurally dissimilar lumichrome or riboflavin. Bacteria, plants, and algae commonly secrete riboflavin or lumichrome, raising the possibility that these compounds could serve as either QS signals or as interkingdom signal mimics capable of manipulating QS in bacteria with a LasR-like receptor.

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Abd El-Aziz, Norhan Khairy, Marwa Ibrahim Abd El-Hamid, and El-sayed Youssef El-Naenaeey. "A complex hierarchical quorum-sensing circuitry modulates phenazine gene expression in Pseudomonas aeruginosa." Journal of Infection in Developing Countries 11, no. 12 (January 10, 2018): 919–25. http://dx.doi.org/10.3855/jidc.8775.

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Introduction: Pseudomonas aeruginosa (P. aeruginosa) modulates the expression of a myriad of virulence factors via two complicated hierarchical quorum-sensing (QS) cascade. This study shed light on the interrelation between P. aeruginosa QS systems and pyocyanin production. Methodology: Transcription analysis of lasR, rhlR, rhlI and phz genes using quantitative real time-reverse transcriptase PCR (qRT–PCR) assay, followed by sequencing of the autoinducer synthase (lasI gene) were applied for 15 P. aeruginosa strains recovered from diverse animal clinical sources. Results: Expression studies revealed that most P. aeruginosa strains demonstrated statistically significant differences (p < 0.05) with a very wide range of transcript levels of QS and phz genes in comparison to P. aeruginosa ATCC 27853. We have identified significant positive correlations (r ≥ 0.3) between the expressions of QS and phz genes in eleven analyzed strains, whereas pyocyanin production positively correlated with the expression of lasR only in three strains (r ≥ 0.6). We further found that there was a negative correlation between the transcript levels of QS and phz genes in one bacterial strain. Analysis of lasI sequences showed point mutations explaining the alterations in pyocyanin expression. The deficiencies of lasI, lasR and rhlI with rhlR-dependent expression of phz in one strain were also recorded. Conclusions: These results provided new insights to the pivotal role of QS signal molecules on pyocyanin production presenting the las system as the dominant regulator.

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Tanasa, Ana, Alexandru Burlacu, Cristina Popa, Mehmet Kanbay, Crischentian Brinza, Liviu Macovei, Radu Crisan-Dabija, and Adrian Covic. "A Systematic Review on the Correlations between Left Atrial Strain and Cardiovascular Outcomes in Chronic Kidney Disease Patients." Diagnostics 11, no. 4 (April 8, 2021): 671. http://dx.doi.org/10.3390/diagnostics11040671.

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Left atrial strain (LASr) represents a relatively new but promising technique for left atrial and left ventricle function evaluation. LASr was strongly linked to myocardial fibrosis and endocardial thickness, suggesting the utility of LASr in subclinical cardiac dysfunction detection. As CKD negatively impacts cardiovascular risk and mortality, underlying structural and functional abnormalities of cardiac remodeling are widely investigated. LASr could be used in LV diastolic dysfunction grading with an excellent discriminatory power. Our objectives were to assess the impact and existing correlations between LASr and cardiovascular outcomes, as reported in clinical trials, including patients with CKD. We searched PubMed, Web of Science, Embase, and the Cochrane Central Register of Controlled Trials for full-text papers. As reported in clinical studies, LASr was associated with adverse cardiovascular outcomes, including cardiovascular death and major adverse cardiovascular events (HR 0.89, 95% CI, 0.84–0.93, p < 0.01), paroxysmal atrial fibrillation (OR 0.847, 95% CI, 0.760–0.944, p = 0.003), reduced exercise capacity (AUC 0.83, 95% CI, 0.78–0.88, p < 0.01), diastolic dysfunction (p < 0.05), and estimated pulmonary capillary wedge pressure (p < 0.001). Despite limitations attributed to LA deformation imaging (image quality, inter-observer variability, software necessity, learning curve), LASr constitutes a promising marker for cardiovascular events prediction and risk evaluation in patients with CKD.

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Cameli, Matteo, Marcelo Haertel Miglioranza, Julien Magne, Giulia Elena Mandoli, Giovanni Benfari, Roberta Ancona, Gerolamo Sibilio, et al. "Multicentric Atrial Strain COmparison between Two Different Modalities: MASCOT HIT Study." Diagnostics 10, no. 11 (November 13, 2020): 946. http://dx.doi.org/10.3390/diagnostics10110946.

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Two methods are currently available for left atrial (LA) strain measurement by speckle tracking echocardiography, with two different reference timings for starting the analysis: QRS (QRS-LASr) and P wave (P-LASr). The aim of MASCOT HIT study was to define which of the two was more reproducible, more feasible, and less time consuming. In 26 expert centers, LA strain was analyzed by two different echocardiographers (young vs senior) in a blinded fashion. The study population included: healthy subjects, patients with arterial hypertension or aortic stenosis (LA pressure overload, group 2) and patients with mitral regurgitation or heart failure (LA volume–pressure overload, group 3). Difference between the inter-correlation coefficient (ICC) by the two echocardiographers using the two techniques, feasibility and analysis time of both methods were analyzed. A total of 938 subjects were included: 309 controls, 333 patients in group 2, and 296 patients in group 3. The ICC was comparable between QRS-LASr (0.93) and P-LASr (0.90). The young echocardiographers calculated QRS-LASr in 90% of cases, the expert ones in 95%. The feasibility of P-LASr was 85% by young echocardiographers and 88% by senior ones. QRS-LASr young median time was 110 s (interquartile range, IR, 78-149) vs senior 110 s (IR 78-155); for P-LASr, 120 s (IR 80-165) and 120 s (IR 90-161), respectively. LA strain was feasible in the majority of patients with similar reproducibility for both methods. QRS complex guaranteed a slightly higher feasibility and a lower time wasting compared to the use of P wave as the reference.

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van Delden, Christian, Rachel Comte, and And Marc Bally. "Stringent Response Activates Quorum Sensing and Modulates Cell Density-Dependent Gene Expression inPseudomonas aeruginosa." Journal of Bacteriology 183, no. 18 (September 15, 2001): 5376–84. http://dx.doi.org/10.1128/jb.183.18.5376-5384.2001.

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ABSTRACT During nutrient starvation, Escherichia coli elicits a stringent response involving the ribosome-associated protein RelA. Activation of RelA results in a global change in the cellular metabolism including enhanced expression of the stationary-phase sigma factor RpoS. In the human pathogen Pseudomonas aeruginosa, a complex quorum-sensing circuitry, linked to RpoS expression, is required for cell density-dependent production of many secreted virulence factors, including LasB elastase. Quorum sensing relies on the activation of specific transcriptional regulators (LasR and RhlR) by their corresponding autoinducers (3-oxo-C12-homoserine lactone [HSL] and C4-HSL), which function as intercellular signals. We found that overexpression of relA activated the expression of rpoS in P. aeruginosa and led to premature, cell density-independent LasB elastase production. We therefore investigated the effects of the stringent response on quorum sensing. Both lasR and rhlR gene expression and autoinducer synthesis were prematurely activated during the stringent response induced by overexpression of relA. Premature expression of lasR and rhlR was also observed when relA was overexpressed in a PAO1 rpoSmutant. The stringent response induced by the amino acid analogue serine hydroxamate (SHX) also led to premature production of the 3-oxo-C12-HSL autoinducer. This response to SHX was absent in a PAO1 relA mutant. These findings suggest that the stringent response can activate the two quorum-sensing systems of P. aeruginosa independently of cell density.

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Urbelis, Vaidotas. "Changes in US Global Security Strategy and their Implications for Lithuania." Lithuanian Annual Strategic Review 1, no. 1 (July 18, 2003): 37–68. http://dx.doi.org/10.47459/lasr.200.1.3.

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Linkevičius, Linas. "Membership of NATO is the Impulse for Reforms." Lithuanian Annual Strategic Review 1, no. 1 (July 18, 2003): 7–15. http://dx.doi.org/10.47459/lasr.2003.1.1.

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Lopata, Raimundas. "Authoritarianism in Belarus: Eventual Threats to Lithuania’s Security." Lithuanian Annual Strategic Review 1, no. 1 (July 18, 2003): 215–29. http://dx.doi.org/10.47459/lasr.2003.1.10.

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Gricius, Algirdas, and Kęstutis Paulauskas. "Democratic Control over the Armed Forces in Lithuania." Lithuanian Annual Strategic Review 1, no. 1 (July 18, 2003): 233–53. http://dx.doi.org/10.47459/lasr.2003.1.11.

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Žeruolis, Darius, and Giedrius Jucevičius. "The Content of the Strategic Dimension of Lithuania’s Economic Policy in a Comparative Perspective." Lithuanian Annual Strategic Review 1, no. 1 (July 18, 2003): 255–76. http://dx.doi.org/10.47459/lasr.2003.1.12.

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Grebliauskas, Artūras. "Analysis of Threats to Economic Security of Lithuania." Lithuanian Annual Strategic Review 1, no. 1 (July 18, 2003): 277–95. http://dx.doi.org/10.47459/lasr.2003.1.13.

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Janušauskienė, Diana, and Jūratė Novagrockienė. "Perception of Security Issues by Lithuanian Population." Lithuanian Annual Strategic Review 1, no. 1 (July 18, 2003): 297–319. http://dx.doi.org/10.47459/lasr.2003.1.14.

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Dranseikaitė, Edita. "Globalisation and New Threats: Terrorism." Lithuanian Annual Strategic Review 1, no. 1 (July 18, 2003): 19–36. http://dx.doi.org/10.47459/lasr.2003.1.2.

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Nekrašas, Evaldas. "Debates on NATO’s Future." Lithuanian Annual Strategic Review 1, no. 1 (July 18, 2003): 69–89. http://dx.doi.org/10.47459/lasr.2003.1.4.

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Čekuolis, Giedrius. "Lithuania in the Context of NATO Enlargement." Lithuanian Annual Strategic Review 1, no. 1 (July 18, 2003): 91–106. http://dx.doi.org/10.47459/lasr.2003.1.5.

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Vitkus, Gediminas. "Changing Security Regime in the Baltic Sea Region." Lithuanian Annual Strategic Review 1, no. 1 (July 18, 2003): 109–32. http://dx.doi.org/10.47459/lasr.2003.1.6.

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Šešelgytė, Margarita. "European Security: New Challenges and Prospects for Co-operation." Lithuanian Annual Strategic Review 1, no. 1 (July 18, 2003): 133–62. http://dx.doi.org/10.47459/lasr.2003.1.7.

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Laurinavičius, Česlovas. "Russia’s Foreign Policy after September II." Lithuanian Annual Strategic Review 1, no. 1 (July 18, 2003): 165–79. http://dx.doi.org/10.47459/lasr.2003.1.8.

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Sirutavičius, Vladas, and Inga Stanytė - Toločkienė. "Strategic Importance of Kaliningrad Oblast of the Russian Federation." Lithuanian Annual Strategic Review 1, no. 1 (July 18, 2003): 181–214. http://dx.doi.org/10.47459/lasr.2003.1.9.

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Motieka, Egidijus, and Nortautas Statkus. "Global and Lithuanian Geopolitical Situation: Review of 2001-2003." Lithuanian Annual Strategic Review 2, no. 1 (October 18, 2004): 9–39. http://dx.doi.org/10.47459/lasr.2004.2.1.

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Šiukštienė, Dalia. "Peculiarities of the Lithuanian Banking Sector Development and their Influence on Residents’ Economic Security." Lithuanian Annual Strategic Review 2, no. 1 (October 18, 2004): 239–58. http://dx.doi.org/10.47459/lasr.2004.2.10.

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Šatūnienė, Živilė. "Energy (In)Dependence and National Security of Lithuania." Lithuanian Annual Strategic Review 2, no. 1 (October 18, 2004): 259–78. http://dx.doi.org/10.47459/lasr.2004.2.11.

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Maliukevičius, Nerijus. "Military Conflict in the Information Age and Lithuania’s Preparedness." Lithuanian Annual Strategic Review 2, no. 1 (October 18, 2004): 41–62. http://dx.doi.org/10.47459/lasr.2004.2.2.

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Gricius, Algirdas, and Kęstutis Paulauskas. "EU’s Common Foreign and Security Policy and Lithuania." Lithuanian Annual Strategic Review 2, no. 1 (October 18, 2004): 65–93. http://dx.doi.org/10.47459/lasr.2004.2.3.

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Šešelgytė, Margarita. "NATO Response Force and the EU Rapid Reaction Force: main challenges and opportunities." Lithuanian Annual Strategic Review 2, no. 1 (October 18, 2004): 95–125. http://dx.doi.org/10.47459/lasr.2004.2.4.

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Vilpišauskas, Ramūnas. "Enhanced cooperation in the EU and its implications for Lithuania." Lithuanian Annual Strategic Review 2, no. 1 (October 18, 2004): 127–43. http://dx.doi.org/10.47459/lasr.2004.2.5.

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Journal articles on the topic 'LasR'

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