title: Characterization of the major secreted zinc metalloprotease- dependent glycerophospholipid:cholesterol acyltransferase, PlaC, of Legionella pneumophila.
abstract: Legionella pneumophila, an intracellular pathogen causing a severe pneumonia, possesses distinct lipolytic activities which have not been completely assigned to specific enzymes so far. We cloned and characterized a gene, plaC, encoding a protein with high homology to PlaA, the major secreted lysophospholipase A of L. pneumophila and to other hydrolytic enzymes belonging to the GDSL family. Here we show that L. pneumophila plaC mutants possessed reduced phospholipase A and lysophospholipase A activities and lacked glycerophospholipid:cholesterol acyltransferase activity in their culture supernatants. The mutants' reduced phospholipase A and acyltransferase activities were complemented by reintroduction of an intact copy of plaC. Additionally, plaC conferred increased lysophospholipase A and glycerophospholipid:cholesterol acytransferase activities to recombinant Escherichia coli. Furthermore, PlaC was shown to be another candidate exported by the L. pneumophila type II secretion system and was activated by a factor present in the bacterial culture supernatant dependent on the zinc metalloprotease. Finally, the role of plaC in intracellular infection of Acanthamoeba castellanii and U937 macrophages with L. pneumophila was assessed, and plaC was found to be dispensable. Thus, L. pneumophila possesses another secreted lipolytic enzyme, a protein with acyltransferase, phospholipase A, and lysophospholipase A activities. This enzyme is distinguished from the previously characterized phospholipases A and lysophospholipases A by its capacity not only to cleave fatty acids from lipids but to transfer them to cholesterol. Cholesterol is an important compound of eukaryotic membranes, and an acyltransferase might be a tool for host cell modification to fit the needs of the bacterium.
authors.affiliation: Robert Koch-Institut, Research Group NG5 Pathogenesis of Legionella Infections, Nordufer 20, D-13353 Berlin, Germany.
authors.forename: Sangeeta
authors.initials: S
authors.lastname: Banerji
authors.forename: Mayte
authors.initials: M
authors.lastname: Bewersdorff
authors.forename: Björn
authors.initials: B
authors.lastname: Hermes
authors.forename: Nicholas P
authors.initials: NP
authors.lastname: Cianciotto
authors.forename: Antje
authors.initials: A
authors.lastname: Flieger
mesh_terms: D048248:Acanthamoeba castellanii / Q000382:microbiology; D000217:Acyltransferases / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D001426:Bacterial Proteins / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial; D006801:Humans; D016952:Legionella pneumophila / Q000201:enzymology* / Q000235:genetics / Q000472:pathogenicity; D008245:Lysophospholipase / Q000378:metabolism; D008666:Metalloendopeptidases / Q000378:metabolism*; D009154:Mutation; D010740:Phospholipases / Q000378:metabolism; D020298:U937 Cells / Q000382:microbiology
chemical_list: D001426:Bacterial Proteins; D000217:Acyltransferases; C020597:glycerophospholipid-cholesterol acyltransferase; D010740:Phospholipases; D008245:Lysophospholipase; D008666:Metalloendopeptidases; C043859:pseudolysin, Pseudomonas aeruginosa