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Gene Review

lasB  -  elastase LasB

Pseudomonas aeruginosa PAO1

 
 
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Disease relevance of lasB

  • The elastase structural gene (lasB) from Pseudomonas aeruginosa PAO1 has been previously cloned on an 8-kilobase (kb) DNA fragment [1].
  • The lasB gene, cloned in both orientations in pUC18, produced elastase in Escherichia coli, indicating that its promoter and translation initiation sites are functional in E. coli [1].
  • The lasB gene encodes elastase, a major proteolytic enzyme secreted by P. aeruginosa, while algD is required for the synthesis of alginate, an exopolysaccharide frequently overproduced by strains infecting cystic fibrosis patients [2].
  • It was also discovered that the lasB promoter region contains two putative operator sequences (OP1 and OP2) that are similar to each other and the Vibrio fischeri lux operator [3].
 

High impact information on lasB

  • It was found that this unique cell-to-cell signal controlled the expression of lasB, which encodes for the major virulence factor, LasB elastase [4].
  • This indicates the presence of a second extracellular factor (factor 2) that is required for lasB activation in P. aeruginosa when lasR is controlled by its own promoter but not when lasR is controlled by a strong foreign promoter [5].
  • These results suggest that PtxR negatively regulates the expression of the rhamnolipid and pyocyanin genes through rhlI and the pqsABCDE operon while it positively regulates the expression of lasB through lasI [6].
  • PtxR also reduced the expression of the PQS synthesis operon pqsABCDE. ptxR mutation increased the expression of the rhamnolipid synthesis gene rhlA but decreased lasB expression [6].
  • In this study, we identify two novel QscR targets these are lasB, encoding the extracellular elastase, and the second phenazine gene cluster, both of which are downregulated by QscR [7].
 

Chemical compound and disease context of lasB

 

Biological context of lasB

  • Northern (RNA) analysis of total cellular RNA from PAO1, PAO-R1, and PAO-R1 containing the lasR gene on a multicopy plasmid (pMG1.7) revealed that a functional lasR gene is required for transcription of the elastase structural gene (lasB) [8].
  • Transcription from the gene for elastase, as measured with a lasB-cat fusion, demonstrated that production of elastase was subject to cell density-dependent gene activation in PAO1 [9].
  • To further characterize the lasB gene, the nucleotide sequence of the 3.0-kb EcoRI-KpnI fragment was determined [1].
  • The lasR gene was cloned by its ability to restore a positive elastase phenotype in strain PA103, a strain which possesses the elastase structural gene (lasB) but fails to synthesize the enzyme [8].
  • The lasB gene was insertionally inactivated with the omega fragment and this mutated gene introduced into the P. aeruginosa chromosome [10].
 

Anatomical context of lasB

 

Associations of lasB with chemical compounds

  • Exogenous N-butyryl-L-homoserine lactone overcame the reduced expression of rhlI and restored rhlAB and lasB expression, as well as elastase production [13].
  • Mutation of lasA and/or lasB reduced P. aeruginosa invasion, which was not fully restored by extracellularly added LasB, P. aeruginosa conditioned medium containing LasA and LasB, or EGTA pretreatment of cells [12].
  • To better understand the role played by envelope constituents in the functioning of this type II secretory system, we have studied the influence of lipopolysaccharide (LPS) on the secretion of two extracellular enzymes, the elastase LasB and the lipase LipA [14].
 

Regulatory relationships of lasB

  • These results suggest that the lasB gene and the alginate system are co-ordinately regulated at a level parallel to or above the algR gene [2].
 

Other interactions of lasB

  • Known QS-regulated extracellular proteins, including elastase (lasB), LasA protease (lasA) and alkaline metalloproteinase (aprA) were also detected [15].
  • When PAO568, a model strain for the analysis of control of the alginate system, was grown under conditions promoting mucoidy, the algD promoter was activated, whereas lasB mRNA could not be detected [2].
  • 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 [16].
  • In P. aeruginosa, overexpression of rsaL results in reduced lasB expression and decreased elastase activity [17].
  • In this study, we found that transcription of the quorum sensing-regulated genes lecA (coding for PA-IL lectin), lasB (coding for elastase), and rpoS appeared to be growth phase dependent and their expression could not be advanced to the logarithmic phase in cells growing in batch culture by the addition of exogenous C4-HSL and 3O-C12-HSL [18].
 

Analytical, diagnostic and therapeutic context of lasB

References

  1. Molecular characterization and nucleotide sequence of the Pseudomonas aeruginosa elastase structural gene. Bever, R.A., Iglewski, B.H. J. Bacteriol. (1988) [Pubmed]
  2. Expression patterns of genes encoding elastase and controlling mucoidy: co-ordinate regulation of two virulence factors in Pseudomonas aeruginosa isolates from cystic fibrosis. Mohr, C.D., Rust, L., Albus, A.M., Iglewski, B.H., Deretic, V. Mol. Microbiol. (1990) [Pubmed]
  3. Analysis of the Pseudomonas aeruginosa elastase (lasB) regulatory region. Rust, L., Pesci, E.C., Iglewski, B.H. J. Bacteriol. (1996) [Pubmed]
  4. Quinolone signaling in the cell-to-cell communication system of Pseudomonas aeruginosa. Pesci, E.C., Milbank, J.B., Pearson, J.P., McKnight, S., Kende, A.S., Greenberg, E.P., Iglewski, B.H. Proc. Natl. Acad. Sci. U.S.A. (1999) [Pubmed]
  5. A second N-acylhomoserine lactone signal produced by Pseudomonas aeruginosa. Pearson, J.P., Passador, L., Iglewski, B.H., Greenberg, E.P. Proc. Natl. Acad. Sci. U.S.A. (1995) [Pubmed]
  6. PtxR modulates the expression of QS-controlled virulence factors in the Pseudomonas aeruginosa strain PAO1. Carty, N.L., Layland, N., Colmer-Hamood, J.A., Calfee, M.W., Pesci, E.C., Hamood, A.N. Mol. Microbiol. (2006) [Pubmed]
  7. Interactions of the quorum sensing regulator QscR: interaction with itself and the other regulators of Pseudomonas aeruginosa LasR and RhlR. Ledgham, F., Ventre, I., Soscia, C., Foglino, M., Sturgis, J.N., Lazdunski, A. Mol. Microbiol. (2003) [Pubmed]
  8. Cloning and characterization of the Pseudomonas aeruginosa lasR gene, a transcriptional activator of elastase expression. Gambello, M.J., Iglewski, B.H. J. Bacteriol. (1991) [Pubmed]
  9. Synthesis of multiple exoproducts in Pseudomonas aeruginosa is under the control of RhlR-RhlI, another set of regulators in strain PAO1 with homology to the autoinducer-responsive LuxR-LuxI family. Brint, J.M., Ohman, D.E. J. Bacteriol. (1995) [Pubmed]
  10. Pseudomonas aeruginosa LasA: a second elastase under the transcriptional control of lasR. Toder, D.S., Gambello, M.J., Iglewski, B.H. Mol. Microbiol. (1991) [Pubmed]
  11. Population transcript accumulation of Pseudomonas aeruginosa exotoxin A and elastase in sputa from patients with cystic fibrosis. Storey, D.G., Ujack, E.E., Rabin, H.R. Infect. Immun. (1992) [Pubmed]
  12. Mutation of lasA and lasB reduces Pseudomonas aeruginosa invasion of epithelial cells. Cowell, B.A., Twining, S.S., Hobden, J.A., Kwong, M.S., Fleiszig, S.M. Microbiology (Reading, Engl.) (2003) [Pubmed]
  13. Inhibition of quorum sensing by a Pseudomonas aeruginosa dksA homologue. Branny, P., Pearson, J.P., Pesci, E.C., Köhler, T., Iglewski, B.H., Van Delden, C. J. Bacteriol. (2001) [Pubmed]
  14. Alteration of the lipopolysaccharide structure affects the functioning of the Xcp secretory system in Pseudomonas aeruginosa. Michel, G., Ball, G., Goldberg, J.B., Lazdunski, A. J. Bacteriol. (2000) [Pubmed]
  15. Proteome analysis of extracellular proteins regulated by the las and rhl quorum sensing systems in Pseudomonas aeruginosa PAO1. Nouwens, A.S., Beatson, S.A., Whitchurch, C.B., Walsh, B.J., Schweizer, H.P., Mattick, J.S., Cordwell, S.J. Microbiology (Reading, Engl.) (2003) [Pubmed]
  16. Transcription of quorum-sensing system genes in clinical and environmental isolates of Pseudomonas aeruginosa. Cabrol, S., Olliver, A., Pier, G.B., Andremont, A., Ruimy, R. J. Bacteriol. (2003) [Pubmed]
  17. RsaL, a novel repressor of virulence gene expression in Pseudomonas aeruginosa. de Kievit, T., Seed, P.C., Nezezon, J., Passador, L., Iglewski, B.H. J. Bacteriol. (1999) [Pubmed]
  18. Advancing the quorum in Pseudomonas aeruginosa: MvaT and the regulation of N-acylhomoserine lactone production and virulence gene expression. Diggle, S.P., Winzer, K., Lazdunski, A., Williams, P., Cámara, M. J. Bacteriol. (2002) [Pubmed]
  19. Pseudomonas aeruginosa LasB mutant constructed by insertional mutagenesis reveals elastolytic activity due to alkaline proteinase and the LasA fragment. Wolz, C., Hellstern, E., Haug, M., Galloway, D.R., Vasil, M.L., Döring, G. Mol. Microbiol. (1991) [Pubmed]
  20. Identification of residues in the Pseudomonas aeruginosa elastase propeptide required for chaperone and secretion activities. McIver, K.S., Kessler, E., Ohman, D.E. Microbiology (Reading, Engl.) (2004) [Pubmed]
 
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