Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0023241 (Legionella)
 6,990 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The mechanism of the effects of lipopolysaccharide (LPS) on macrophages in terms of replication of intracellular facultative bacteria is unclear. It was found in the present study that the anti-Legionella pneumophila activity induced by LPS in macrophages from susceptible A/J mice was reversed in vitro by dibutyryl cyclic AMP (DcAMP). A 24-h pretreatment of murine thioglycolate-elicited macrophages with LPS resulted in an enhanced ability of these cells to inhibit the intracellular growth of L. pneumophila. This anti-L. pneumophila activity of macrophages induced by LPS was inhibited when DcAMP (10(-3) to 10(-5) M) was present during preincubation with LPS. The addition of DcAMP to the cultures was more effective before LPS treatment than after treatment. The effect of DcAMP was dose dependent. The secretion and production of acid phosphatase by LPS-activated macrophages were also inhibited by the addition of DcAMP before LPS treatment. Furthermore, the anti-L. pneumophila activity of macrophages induced by LPS could also be reversed in vitro by treatment with prostaglandin E2, colchicine, isoproterenol, theophylline, or hydrocortisone, all of which are known to increase the intracellular levels of cyclic AMP in various tissues. These observations indicate that the anti-L. pneumophila activity induced by LPS treatment can be modified by mechanisms involving cyclic nucleotide metabolism.
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PMID:Cyclic AMP inhibition of lipopolysaccharide-induced restriction of Legionella pneumophila growth in macrophage cultures. 131 22

The legionellae are facultative intracellular bacterial pathogens which multiply in host phagocytes. Legionella micdadei cells contain an acid phosphatase (ACP2) which blocks superoxide anion production by human neutrophils stimulated with formyl-Met-Leu-Phe (fMLP) [A. K. Saha, et al. (1985) Arch. Biochem. Biophys. 243, 150-160]. In the present study, we have purified the Legionella phosphatase to homogeneity as indicated by the finding of a single 68,000-Da band following sodium dodecyl sulfate-polyacrylamide gel electrophoresis. We explored the possibility that ACP2 acts by interfering with polyphosphoinositide hydrolysis and the production of the intracellular second messengers, inositol trisphosphate (IP3) and diacylglycerol, following neutrophil stimulation. Phosphatidylinositol 4,5-bisphosphate (PIP2) was hydrolyzed rapidly by ACP2 in vitro. The rate of hydrolysis of PIP2 was higher at pH 7.0 (Km 2.0 microM; 4 X 10(3) units/mg protein; 1 unit equals 1 nmol of Pi released/h) than at lower pH. IP3 was also a good substrate for ACP2 in vitro. When human neutrophil phosphoinositides were prelabeled with 32Pi, subsequent incubation with ACP2 resulted in an 85% loss of the labeled PIP2 over 2 h. Following fMLP stimulation of [3H]inositol-labeled neutrophils, the quantity of IP3 produced by ACP2-treated cells was reduced by 44%. Prior treatment of neutrophils with ACP2 also reduced by 45% the amount of diacylglycerol they produced when stimulated by fMLP. These results indicate that the Legionella phosphatase may compromise the neutrophils' microbicidal response to the organism by hydrolyzing PIP2, the progenitor of IP3 and diacylglycerol, and by hydrolyzing IP3 itself.
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PMID:Legionella micdadei phosphatase catalyzes the hydrolysis of phosphatidylinositol 4,5-bisphosphate in human neutrophils. 284 4

Advances in computerized microscopy have resulted in image analysis systems that rapidly and precisely measure various aspects of cellular morphology and physiology. These systems-composed of a microscope and attached photomultiplier tube or camera, an image processor, and a computer-have been used to measure lysosomal enzymes, pH, and calcium within phagocytes; to detect viral nucleic acids in in situ hybridization preparations; and to quantitate rates of cellular movement. These experiments have shown that (1) the intracellular proliferation of virulent microorganisms is associated with reductions in acid phosphatase, beta-glucuronidase, and lysozyme activity; (2) virulent Toxoplasma gondii, Legionella pneumophila, and Nocardia asteroides inhibit phagosomal acidification; and (3) changes in intracellular calcium movement affect phagocytic function. These methods have also been used to detect the AIDS virus within cultured lymphocytes and to measure cellular chemotaxis and chemokinesis. Further advances in technology should produce improved microscopic image analysis systems with wider applications for the investigation of infectious diseases.
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PMID:Applications of computerized microscopic image analysis in infectious diseases. 328 Dec 25

The API ZYM system was used to investigate enzymatic activities of Legionella pneumophila and other Legionella-like organisms. Leucine aminopeptidase, alkaline and acid phosphatase, butyrate and caprylate esterase, and phosphoamidase activities were consistently detected in all strains tested. No evidence of myristate lipase, trypsin, chymotrypsin, or glycosidase activity was found.
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PMID:Enzymatic activities of Legionella pneumophila and Legionella-like organisms. 718 5

Microbial phosphatases are known or suspected to play a role in the pathogenesis of several intracellular pathogens, including Legionella micdadei. Legionella pneumophila also possess phosphatase activities, but their possible roles in cellular infection are unknown. We generated mutants of a serogroup 1 isolate of L. pneumophila that lack the major phosphatase. Isolation of a Pho- mutant after random mutagenesis with transposon MudII4041 allowed us to dissociate the major alkaline phosphatase (pH optimum approximately 8) from a minor acid phosphatase activity. Both activities were concentrated in the bacterial periplasm. The gene encoding the major alkaline phosphatase (pho) was cloned by expression in E. coli and used to generate a site directed mutation in two L. pneumophila strains. Each parent-mutant pair was compared in a U937 cell tissue culture assay for capacity to infect, lyse, and grow within mammalian cells. Although the parental stains differed in their U937 cell cytopathicity, neither was significantly more infective than its Pho- derivative, suggesting that the alkaline phosphatase activity is not essential for cellular infection. Because they are not attenuated, Pho- mutants can be used to generate gene fusions with E. coli alkaline phosphatase to study and secretion and cellular infectivity in L. pneumophila.
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PMID:Phosphatase-negative mutants of Legionella pneumophila and their behavior in mammalian cell infection. 786 53

High-speed supernatant fluids derived from sonicated Coxiella burnetii contained considerable acid phosphatase activity when assayed by using 4-methylumbelliferylphosphate; they also contained a factor that blocked superoxide anion production by human neutrophils stimulated with formyl-Met-Leu-Phe. The pH optimum of the enzyme was approximately 5.0. The level of phosphatase activity detected in several isolates of C. burnetii implicated in acute (Nine Mile) and chronic (S Q217, PRS Q177, K Q154) Q fever was 25 to 60 times greater than that reported in other microorganisms, including Leishmania and Legionella spp. The enzyme was found in rickettsiae grown in different hosts (L929 cells and embryonated eggs) and, in the case of L929 cells, for both short periods (less than a month) and the long term (years). Cytochemical techniques coupled with electron microscopy localized the phosphatase activity to the periplasmic gap in the parasite. Ion-exchange chromatography revealed a major species of the enzyme and showed that the enzyme of the parasite was distinct from that of the host cell (L929 fibroblasts); its apparent molecular weight was 74,000. Phosphatase inhibitors (i.e., molybdate heteropolyanions) had differential effects on the phosphatases of the parasite and host cell. C. burnetii supernatant fluid inhibited superoxide anion production by formyl-Met-Leu-Phe-stimulated human neutrophils; molybdate inhibitors reversed the inhibition. Treatment of C. burnetii-infected L929 cells with one of the molybdate compounds (complex B') significantly reduced the level of infection and did not affect the viability or growth of the host cell. These data suggest that the acid phosphatase of the parasite may be a major virulence determinant, allowing the agent to avoid being killed during uptake by phagocytes and subsequently in the phagolysosome.
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PMID:Acid phosphatase activity in Coxiella burnetii: a possible virulence factor. 840 11

Amphizoic small amoebic protozoa are capable of existing both in 'free-living' and in 'parasitic' form depending on the actual conditions. Two genera (Naegleria and Acanthamoeba) have become recognised as opportunist human parasites. Since the first description in 1965 of a lethal case of primary amoebic meningoencephalitis (PAM) caused by Naegleria, many more (mostly lethal) cases have been reported, while granulomatous amoebic encephalitis (GAE), as well as eye (keratinitis, conjunctivitis, etc.), ear, nose, skin and internal organ infections caused by Acanthamoeba have also occurred in rapidly increasing numbers. Both pathogenic and non-pathogenic species of Naegleria and Acanthamoeba are found worldwide in water, soil and dust, where they provide a potential source of infection. Successful differential diagnosis and appropriate (specific) therapy depends on precise laboratory identification of the 'free-living' amoebae. In most cases, isolation from the environment can be achieved, but identification and differentiation of the pathogenic and non-pathogenic strains is not easy. The methods presently available do not fulfil completely the requirements for specificity, sensitivity and reliability. Morphological criteria are inadequate, while thermophilic character, pH dependency and even virulence in infected mice, are not unambiguous features of pathogenicity of the different strains. More promising are molecular methods, such as restriction endonuclease digestion of whole-cell DNA or mitochondrial DNA, as well as iso-enzyme profile analysis after iso-electric focusing and staining for acid phosphatase and propionyl esterase activity. Use of appropriate monoclonal antibodies has also yielded promising results in the differentiation of human pathogenic and non-pathogenic strains. However, quicker, simpler, more specific and reliable methods are still highly desirable. The significance of endosymbiosis (especially with Legionella strains) is not well understood. The results of a systematic survey in Hungary for the isolation and identification of 'free-living' amoebae, including an investigation of the Hungarian amoebic fauna, the isolation of possibly pathogenic Naegleria strains and of some Acanthamoeba strains from eye diseases, as well as the finding of a case of endosymbiosis, are also reported here.
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PMID:Isolation, identification and increasing importance of 'free-living' amoebae causing human disease. 978 20

Legionella pneumophila, the agent of Legionnaires' disease, is an intracellular pathogen of protozoa and macrophages. Previously, we had determined that the Legionella pilD gene is involved in type IV pilus biogenesis, type II protein secretion, intracellular infection, and virulence. Since the loss of pili and a protease do not account for the infection defect exhibited by a pilD-deficient strain, we sought to define other secreted proteins absent in the mutant. Based upon the release of p-nitrophenol (pNP) from p-nitrophenyl phosphate, acid phosphatase activity was detected in wild-type but not in pilD mutant supernatants. Mutant supernatants also did not release either pNP from p-nitrophenyl caprylate and palmitate or free fatty acid from 1-monopalmitoylglycerol, suggesting that they lack a lipase-like activity. However, since wild-type samples failed to release free fatty acids from 1,2-dipalmitoylglycerol or to cleave a triglyceride derivative, this secreted activity should be viewed as an esterase-monoacylglycerol lipase. The mutant supernatants were defective for both release of free fatty acids from phosphatidylcholine and degradation of RNA, indicating that PilD-negative bacteria lack a secreted phospholipase A (PLA) and nuclease. Finally, wild-type but not mutant supernatants liberated pNP from p-nitrophenylphosphorylcholine (pNPPC). Characterization of a new set of mutants defective for pNPPC-hydrolysis indicated that this wild-type activity is due to a novel enzyme, as opposed to a PLC or another known enzyme. Some, but not all, of these mutants were greatly impaired for intracellular infection, suggesting that a second regulator or processor of the pNPPC hydrolase is critical for L. pneumophila virulence.
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PMID:Secreted enzymatic activities of wild-type and pilD-deficient Legionella pneumophila. 1072 74

Legionella pneumophila is an intracellular pathogen of protozoa and alveolar macrophages. This bacterium contains a gene (pilD) that is involved in both type IV pilus biogenesis and type II protein secretion. We previously demonstrated that the PilD prepilin peptidase is crucial for intracellular infection by L. pneumophila and that the secreted pilD-dependent proteins include a metalloprotease, an acid phosphatase, an esterase/lipase, a phospholipase A, and a p-nitrophenyl phosphorylcholine hydrolase. Since mutants lacking type IV pili, the protease, or the phosphorylcholine hydrolase are not defective for intracellular infection, we sought to determine the significance of the secreted acid phosphatase activity. Three mutants defective in acid phosphatase activity were isolated from a population of mini-Tn10-mutagenized L. pneumophila. Supernatants as well as cell lysates from these mutants contained minimal acid phosphatase activity while possessing normal levels of other pilD-dependent exoproteins. Genetic studies indicated that the gene affected by the transposon insertions encoded a novel bacterial histidine acid phosphatase, which we designated Map for major acid phosphatase. Subsequent inhibitor studies indicated that Map, like its eukaryotic homologs, is a tartrate-sensitive acid phosphatase. The map mutants grew within macrophage-like U937 cells and Hartmannella amoebae to the same degree as did wild-type legionellae, indicating that this acid phosphatase is not essential for L. pneumophila intracellular infection. However, in the course of characterizing our new mutants, we gained evidence for a second pilD-dependent acid phosphatase activity that, unlike Map, is tartrate resistant.
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PMID:Legionella pneumophila major acid phosphatase and its role in intracellular infection. 1111 4

Previously, we had demonstrated that a Legionella pneumophila prepilin peptidase (pilD) mutant does not produce type IV pili and shows reduced secretion of enzymatic activities. Moreover, it displays a distinct colony morphology and a dramatic reduction in intracellular growth within amoebae and macrophages, two phenotypes that are not exhibited by a pilin (pilE(L)) mutant. To determine whether these pilD-dependent defects were linked to type II secretion, we have constructed two new mutants of L. pneumophila strain 130b. Mutations were introduced into either lspDE, which encodes the type II outer membrane secretin and ATPase, or lspFGHIJK, which encodes the pseudopilins. Unlike the wild-type and pilE(L) strains, both lspDE and lspG mutants showed reduced secretion of six pilD-dependent enzymatic activities; i.e., protease, acid phosphatase, p-nitrophenol phosphorylcholine hydrolase, lipase, phospholipase A, and lysophospholipase A. However, they exhibited a colony morphology different from that of the pilD mutant, suggesting that their surfaces are distinct. The pilD, lspDE, and lspG mutants were similarly and greatly impaired for growth within Hartmannella vermiformis, indicating that the intracellular defect of the peptidase mutant in amoebae is explained by the loss of type II secretion. When assessed for infection of U937 macrophages, both lsp mutants exhibited a 10-fold reduction in intracellular multiplication and a diminished cytopathic effect. Interestingly, the pilD mutant was clearly 100-fold more defective than the type II secretion mutants in U937 cells. These results suggest the existence of a novel pilD-dependent mechanism for promoting L. pneumophila intracellular infection of human cells.
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PMID:Type II protein secretion is a subset of the PilD-dependent processes that facilitate intracellular infection by Legionella pneumophila. 1125 62


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