title: The Legionella pneumophila Dot/Icm-secreted effector PlcC/CegC1 together with PlcA and PlcB promotes virulence and belongs to a novel zinc metallophospholipase C family present in bacteria and fungi.
abstract: Legionella pneumophila is a water-borne bacterium that causes pneumonia in humans. PlcA and PlcB are two previously defined L. pneumophila proteins with homology to the phosphatidylcholine-specific phospholipase C (PC-PLC) of Pseudomonas fluorescens. Additionally, we found that Lpg0012 shows similarity to PLCs and has been shown to be a Dot/Icm-injected effector, CegC1, which is designated here as PlcC. It remained unclear, however, whether these L. pneumophila proteins exhibit PLC activity. PlcC expressed in Escherichia coli hydrolyzed a broad phospholipid spectrum, including PC, phosphatidylglycerol (PG), and phosphatidylinositol. The addition of Zn(2+) ions activated, whereas EDTA inhibited, PlcC-derived PLC activity. Protein homology search revealed that the three Legionella enzymes and P. fluorescens PC-PLC share conserved domains also present in uncharacterized fungal proteins. Fifteen conserved amino acids were essential for enzyme activity as identified via PlcC mutagenesis. Analysis of defined L. pneumophila knock-out mutants indicated Lsp-dependent export of PG-hydrolyzing PLC activity. PlcA and PlcB exhibited PG-specific activity and contain a predicted Sec signal sequence. In line with the reported requirement of host cell contact for Dot/Icm-dependent effector translocation, PlcC showed cell-associated PC-specific PLC activity after bacterial growth in broth. A PLC triple mutant, but not single or double mutants, exhibited reduced host killing in a Galleria mellonella infection model, highlighting the importance of the three PLCs in pathogenesis. In summary, we describe here a novel Zn(2+)-dependent PLC family present in Legionella, Pseudomonas, and fungi with broad substrate preference and function in virulence.
authors: Division of Bacterial Infections, Robert Koch-Institut, Burgstrasse 37, 38855 Wernigerode, Germany.
authors: Philipp
authors: P
authors: Aurass
authors: Maren
authors: M
authors: Schlegel
authors: Omar
authors: O
authors: Metwally
authors: Clare R
authors: CR
authors: Harding
authors: Gunnar N
authors: GN
authors: Schroeder
authors: Gad
authors: G
authors: Frankel
authors: Antje
authors: A
authors: Flieger
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism; D005658:Fungi / Q000201:enzymology / Q000235:genetics; D016952:Legionella pneumophila / Q000201:enzymology* / Q000235:genetics / Q000472:pathogenicity*; D008667:Metalloproteins / Q000235:genetics / Q000378:metabolism*; D009154:Mutation; D010740:Phospholipases / Q000235:genetics / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D017386:Sequence Homology, Amino Acid; D037521:Virulence Factors / Q000235:genetics / Q000378:metabolism*; D015032:Zinc / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D005656:Fungal Proteins; D008667:Metalloproteins; D037521:Virulence Factors; D010740:Phospholipases; D015032:Zinc