Affiliation:
1. Robert Koch-Institut, Berlin, Germany
2. Department of Microbiology-Immunology, Northwestern University Medical School, Chicago, Illinois
Abstract
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.
Publisher
American Society for Microbiology
Subject
Infectious Diseases,Immunology,Microbiology,Parasitology
Cited by
72 articles.
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