Dihydrolipoamide Dehydrogenase of Pseudomonas aeruginosa Is a Surface-Exposed Immune Evasion Protein That Binds Three Members of the Factor H Family and Plasminogen

Abstract

The opportunistic human pathogen Pseudomonas aeruginosa causes a wide range of diseases. To cross host innate immune barriers, P. aeruginosa has developed efficient strategies to escape host complement attack. In this study, we identify the 57-kDa dihydrolipoamide dehydrogenase (Lpd) as a surface-exposed protein of P. aeruginosa that binds the four human plasma proteins, Factor H, Factor H-like protein-1 (FHL-1), complement Factor H-related protein 1 (CFHR1), and plasminogen. Factor H contacts Lpd via short consensus repeats 7 and 18–20. Factor H, FHL-1, and plasminogen when bound to Lpd were functionally active. Factor H and FHL-1 displayed complement-regulatory activity, and bound plasminogen, when converted to the active protease plasmin, cleaved the chromogenic substrate S-2251 and the natural substrate fibrinogen. The lpd of P. aeruginosa is a rather conserved gene; a total of 22 synonymous and 3 nonsynonymous mutations was identified in the lpd gene of the 5 laboratory strains and 13 clinical isolates. Lpd is surface exposed and contributes to survival of P. aeruginosa in human serum. Bacterial survival was reduced when Lpd was blocked on the surface prior to challenge with human serum. Similarly, bacterial survival was reduced up to 84% when the bacteria was challenged with complement active serum depleted of Factor H, FHL-1, and CFHR1, demonstrating a protective role of the attached human regulators from complement attack. In summary, Lpd is a novel surface-exposed virulence factor of P. aeruginosa that binds Factor H, FHL-1, CFHR1, and plasminogen, and the Lpd-attached regulators are relevant for innate immune escape and most likely contribute to tissue invasion.

Tuf of Streptococcus pneumoniae is a surface displayed human complement regulator binding protein

“…SCRs 6-7 and SCRs 18-20. Microbial proteins that bind Factor H and FHL-1 via these domains, include Rck from Salmonella enterica, Lpd from P. aeruginosa and Gpm1p and Pra1 from C. albicans (Hallstrom et al, 2012;Ho et al, (C) TufSp is present in cytoplasmic and membrane fractions. Cytoplasmic and membrane fractions were obtained from eight S. pneumoniae strains by subcellular fractionation.…”

“…Pathogenic microbes often use several Factor H binding and complement acquiring surface proteins. Such microbial immune evasion proteins include Shiga toxin of Escherichia coli (Poolpol et al, 2014), NspA of Neisseria meningitidis (Lewis et al, 2010), Scl-1 of Streptococcus pyogens (Reuter et al, 2010), Sbi, SdrE and Ecb of Staphylococcus aureus (Amdahl et al, 2013;Haupt et al, 2008;Sharp et al, 2012), Lpd of Pseudomonas aeruginosa (Hallstrom et al, 2012) and Pra-1, Gpd2 and Hgt1p of Candida albicans (Lesiak-Markowicz et al, 2011;Luo et al, 2009Luo et al, , 2013Poltermann et al, 2007).…”

Identification of an extracellular bacterial flavoenzyme that can prevent re-polymerisation of lignin fragments

“…Dihydrolipoamide dehydrogenase has also been implicated in reducing cellular nitric oxide [27], iron [28], and tellurite [29]. Although dihydrolipoamide dehydrogenase is normally an intracellular enzyme [22,25,26] there are reports of cell surface dehydrolipoamide dehydrogenase enzyme activities in Pseudomonas aeruginosa [30],…”

Identification of a Haemophilus influenzae Factor H–Binding Lipoprotein Involved in Serum Resistance

“…Several pathogens rely on a comparable multifarious strategy to recruit FH at their surface. In Pseudomonas aeruginosa, Yersinia enterocolitica, Streptococcus pneumoniae, Streptococcus pyogenes, and Borrelia burgdorferi at least two different FH-binding proteins have been characterized, whereas in N. meningitidis, FH recruitment occurs through sialylation of the LOS as well as two separate FH-binding proteins (13,37,55).…”