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Legionella pneumophila type II secretome ... cterial persistence in the lung
Legionella pneumophila type II secretome reveals unique exoproteins and a chitinase that promotes bacterial persistence in the lung
7334
Type II protein secretion is critical for Legionella pneumophila infection of amoebae, macrophages, and mice. Previously, we found several enzymes to be secreted by this (Lsp) secretory pathway. To better define the L. pneumophila type II secretome, a 2D electrophoresis proteomic approach was used to compare proteins in wild-type and type II mutant supernatants. We identified 20 proteins that are type II-dependent, including aminopeptidases, an RNase, and chitinase, as well as proteins with no homology to known proteins. Because a chitinase had not been previously reported in Legionella, we determined that wild type secretes activity against both p-nitrophenyl triacetyl chitotriose and glycol chitin. An lsp mutant had a 70-75% reduction in activity, confirming the type II dependency of the secreted chitinase. Newly constructed chitinase (chiA) mutants also had approximately 75% less activity, and reintroduction of chiA restored the mutants to normal levels of activity. Although chiA mutants were not impaired for in vitro intracellular infection, they were defective upon intratracheal inoculation into the lungs of A/J mice, and antibodies against ChiA were detectable in infected animals. In contrast, mutants lacking a secreted phosphatase, protease, or one of several lipolytic enzymes were not defective in vivo. In sum, this study shows that the output of type II secretion is greater in magnitude than previously appreciated and includes previously undescribed proteins. Our data also indicate that an enzyme with chitinase activity can promote infection of a mammalian host.
DebRoy S, Dao J, Söderberg M, Rossier O, Cianciotto NP
Proceedings of the National Academy of Sciences of the United States of America
2006-12-12 00:00
103
50
19146-51
Animals,Bacterial Proteins,Cell Line,Chitinase,Electrophoresis, Gel, Two-Dimensional,Humans,Intracellular Membranes,Legionella pneumophila,Legionnaires' Disease,Mice,Mutation,Bacterial Proteins,Chitinase
Department of Microbiology-Immunology, Northwestern University Medical School, Chicago, IL 60611, USA.
Proc. Natl. Acad. Sci. U.S.A.
NIAID AI 43987
0027-8424
10.1073/pnas.0608279103
0608279103
0
False
17148602
