Phospholipase A in Gram-negative bacteria and its role in pathogenesis (original) (raw)

Bacterial phospholipase A: structure and function of an integral membrane phospholipase

Biochimica et Biophysica Acta (BBA) - Molecular and Cell Biology of Lipids, 2000

Within the large family of lipolytic enzymes, phospholipases constitute a very diverse subgroup with physiological functions such as digestion and signal transduction. Most phospholipases may associate with membranes at the lipid-water interface. However, in many Gram-negative bacteria, a phospholipase is present which is located integrally in the bacterial outer membrane. This phospholipase (outer membrane phospholipase A or OMPLA) is involved in transport across the bacterial outer membrane and has been implicated in bacterial virulence. OMPLA is calcium dependent and its activity is strictly regulated by reversible dimerisation. Recently the crystal structure of this integral membrane enzyme has been elucidated. In this review, we summarise the implications of these structural data for the understanding of the function and regulation of OMPLA, and discuss a mechanism for phospholipase dependent colicin release in Escherichia coli. ß

Antibacterial actions of secreted phospholipases A2. Review

Biochimica et Biophysica Acta (BBA) - Molecular and Cell Biology of Lipids, 2008

Antibacterial properties of secreted phospholipases A 2 (PLA 2 ) have emerged gradually. Group (G) IIA PLA 2 is the most potent among mammalian secreted (s) PLA 2 s against Gram-positive bacteria, but additional antibacterial compounds, e.g. the bactericidal/permeabilityincreasing protein, are needed to kill Gram-negative bacteria. The mechanisms of binding to the bacterial surface and the killing of bacteria by sPLA 2 s are based on the positive charge of the PLA 2 protein and its phospholipolytic enzymatic activity, respectively. The concentration of GIIA PLA 2 is highly elevated in serum of patients with bacterial sepsis, and overexpression of GIIA PLA 2 protects transgenic mice against experimental Gram-positive infection. The synthesis and secretion of GIIA PLA 2 are stimulated by the cytokines TNF-α, IL-1 and IL-6. Secreted PLA 2 s may be potentially useful new endogenous antibiotics to combat infections including those caused by antibiotic-resistant bacteria such as methicillinresistant staphylococci and vancomysin-resistant enterococci.

Bactericidal Properties of Group IIA and Group V Phospholipases A2

The Journal of …, 2001

Group V phospholipase A 2 (PLA 2) is a recently characterized 14-kDa secretory PLA 2 of mammalian heart and macrophagederived cells. Group IIA PLA 2 , which is structurally close to group V PLA 2 , has been shown to kill Gram-positive bacteria in vitro and to prevent symptoms of Gram-positive infection in vivo. We studied the antibacterial properties of fully active recombinant rat group IIA and V PLA 2 s. Both group IIA and V PLA 2 s were highly bactericidal against Gram-positive bacteria, including methicillin-resistant staphylococci and vancomycin-resistant enterococci. Only high concentrations of group IIA PLA 2 showed some bactericidal effect against the Gram-negative bacterium Escherichia coli. Our results confirm that group IIA PLA 2 is a potent antibacterial enzyme against Gram-positive bacteria. Moreover, we show here that group V PLA 2 is a novel antibacterial mammalian protein, but is less potent than group IIA PLA 2. Both enzymes may be considered as future therapeutic agents against bacterial infections.

Diverse type VI secretion phospholipases are functionally plastic antibacterial effectors

Nature, 2013

Membranes allow the compartmentalization of biochemical processes and are therefore fundamental to life. The conservation of the cellular membrane, combined with its accessibility to secreted proteins, has made it a common target of factors mediating antagonistic interactions between diverse organisms. Here we report the discovery of a diverse superfamily of bacterial phospholipase enzymes. Within this superfamily, we defined enzymes with phospholipase A1 (PLA 1 ) and A2 (PLA 2 ) activity, which are common in host cell-targeting bacterial toxins and the venoms of certain insects and reptiles 1,2 . However, we find that the fundamental role of the superfamily is to mediate antagonistic bacterial interactions as effectors of the type VI secretion system (T6SS) translocation apparatus; accordingly, we name these proteins type VI lipase effectors (Tle). Our analyses indicate that PldA of Pseudomonas aeruginosa, a eukaryotic-like phospholipase D (PLD) 3 , is a member of the Tle superfamily and the founding substrate of the haemolysin co-regulated protein secretion island II T6SS (H2-T6SS). While prior studies have specifically implicated PldA and the H2-T6SS in pathogenesis 3-5 , we uncovered a specific role for the effector and its secretory machinery in intra-and inter-species bacterial interactions. Furthermore we find that this effector achieves its antibacterial activity by degrading phosphatidylethanolamine (PE), the major component of bacterial membranes. The surprising finding that virulence-associated phospholipases can serve as specific antibacterial effectors suggests that interbacterial interactions are a relevant factor driving the ongoing evolution of pathogenesis.

Phospholipase A 2 Functions in Pseudomonas aeruginosa - Induced Apoptosis

Infection and Immunity, 2006

Pseudomonas aeruginosa, a gram-negative, facultative pathogen, causes severe and often even lethal infections in immunocompromised patients, as well as cystic fibrosis patients. We show here that a variety of P. aeruginosa strains activate phospholipase A 2 (PLA 2), cultured epithelial cells, and fibroblasts, resulting in increased intracellular and extracellular arachidonic acid release. The use of different PLA 2 inhibitors revealed that P. aeruginosa-induced arachidonic acid release is mediated by activation of cytosolic PLA 2 (cPLA2), whereas iPLA 2 or sPLA 2 do not seem to be involved in the response to P. aeruginosa. Likewise, the cPLA 2-specific inhibitors MAFP and AACOCF3 prevented apoptosis of cultured epithelial cells upon P. aeruginosa infection, whereas inhibitors specific for iPLA 2 or sPLA 2 were without effect. The physiological significance of these findings is indicated by an inhibition of apoptosis in tracheal epithelial cells upon in vivo infection with P. aeruginosa. The data indicate that arachidonic acid generation by activation of cPLA 2 during P. aeruginosa infection plays an important role in the induction of host cell death.

Phospholipase A activity in Pseudomonas aeruginosa

Zentralblatt für Bakteriologie : international journal of medical microbiology, 1995

Our study describes the production, purification and properties of an enzyme from Pseudomonas aeruginosa displaying the properties of phospholipase A. Maximal amounts of enzyme could be detected in the culture supernatant when the bacterium was grown for 3 to 5 days at 37 degrees C in stirred flask cultures containing brain heart infusion. The enzyme was purified by polyethylenimine precipitation and ammonium sulfate precipitation followed by gel filtration. In sodium dodecyl sulfate-polyacrylamide gel electrophoresis, the enzyme preparation exhibited two bands with molecular weights of 13.5 and 60 kD, respectively. Correspondingly, two peaks of the same molecular weight could be demonstrated by high performance size exclusion chromatography. The activity toward the sn-2 ester binding of phospholipids was characterized and found to be highest towards phosphatidylcholine. Enzymatic activity was not influenced by the addition of calcium or EDTA while magnesium and strontium caused a d...

Phospholipase A2 Functions in Pseudomonas aeruginosa- Induced Apoptosis

Infection and Immunity, 2006

Pseudomonas aeruginosa, a gram-negative, facultative pathogen, causes severe and often even lethal infections in immunocompromised patients, as well as cystic fibrosis patients. We show here that a variety of P. aeruginosa strains activate phospholipase A2 (PLA2), cultured epithelial cells, and fibroblasts, resulting in increased intracellular and extracellular arachidonic acid release. The use of different PLA2 inhibitors revealed that P. aeruginosa-induced