Phospholipase A2 enzymes: physical structure, biological function, disease implication, chemical inhibition, and therapeutic intervention.
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ABSTRACT:
SUBMITTER: Dennis EA
PROVIDER: S-EPMC3196595 | biostudies-literature | 2011 Oct
REPOSITORIES: biostudies-literature
Publications
Phospholipase A2 enzymes: physical structure, biological function, disease implication, chemical inhibition, and therapeutic intervention.
Dennis Edward A EA Cao Jian J Hsu Yuan-Hao YH Magrioti Victoria V Kokotos George G
Chemical reviews 20110912 10
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Project description:The development of selective inhibitors for individual PLA(2) enzymes is necessary in order to target PLA(2)-specific signaling pathways, but it is challenging due to the observed promiscuity of known PLA(2) inhibitors. In the current work, we present the development and application of a variety of synthetic routes to produce pentafluoro, tetrafluoro, and trifluoro derivatives of activated carbonyl groups in order to screen for selective inhibitors and characterize the chemical properties that can lead to selective inhibition. Our results demonstrate that the pentafluoroethyl ketone functionality favors selective inhibition of the GVIA iPLA(2), a very important enzyme for which specific, potent, reversible inhibitors are needed. We find that 1,1,1,2,2-pentafluoro-7-phenyl-heptan-3-one (FKGK11) is a selective inhibitor of GVIA iPLA(2) (X(I)(50) = 0.0073). Furthermore, we conclude that the introduction of an additional fluorine atom at the alpha' position of a trifluoromethyl ketone constitutes an important strategy for the development of new potent GVIA iPLA(2) inhibitors.
| S-EPMC2649009 | biostudies-literature
Project description:Phospholipase A2 (PLA2) cleave phospholipids preferentially at the sn-2 position, liberating free fatty acids and lysophospholipids. They are classified into six main groups based on size, location, function, substrate specificity and calcium requirement. These classes include secretory PLA2 (sPLA2), cytosolic (cPLA2), Ca(2+)-independent (iPLA2), platelet activating factor acetylhydrolases (PAF-AH), lysosomal PLA2 (LyPLA2) and adipose specific PLA2 (AdPLA2). It is hypothesized that PLA2 can serve as pharmacological targets for the therapeutic treatment of several diseases, including cardiovascular diseases, atherosclerosis, immune disorders and cancer. Special emphasis has been placed on inhibitors of sPLA2 isoforms as pharmacological moieties, mostly due to the fact that these enzymes are activated during inflammatory events and because their expression is increased in several diseases. This review focuses on understanding how sPLA2 isoform expression is altered during disease progression and the possible therapeutic interventions to specifically target sPLA2 isoforms, including new approaches using nano-particulate-based strategies.
| S-EPMC4104246 | biostudies-literature
Project description:Lysosomal phospholipase A2 (LPLA2/PLA2G15) is a key enzyme involved in lipid homeostasis and is characterized by both phospholipase A2 and transacylase activity and by an acidic pH optimum. Divalent cations such as Ca2+ and Mg2+ have previously been shown to have little effect on the activity of LPLA2, but the discovery of a novel crystal form of LPLA2 with Zn2+ bound in the active site suggested a role for this divalent cation in regulating enzyme activity. In this complex, the cation directly coordinates the serine and histidine of the α/β-hydrolase triad and stabilizes a closed conformation. This closed conformation is characterized by an inward shift of the lid loop, which extends over the active site and effectively blocks access to one of its lipid acyl chain binding tracks. Therefore, we hypothesized that Zn2+ would inhibit LPLA2 activity at a neutral but not acidic pH because histidine would be positively charged at lower pH. Indeed, Zn2+ was found to inhibit the esterase activity of LPLA2 in a noncompetitive manner exclusively at a neutral pH (between 6.5 and 8.0). Because lysosomes are reservoirs of Zn2+ in cells, the pH optimum of LPLA2 might allow it to catalyze acyl transfer unimpeded within the organelle. We conjecture that Zn2+ inhibition of LPLA2 at higher pH maintains a lower activity of the esterase in environments where its activity is not typically required.
| S-EPMC6677152 | biostudies-literature
Project description:Phospholipidosis, the excessive accumulation of phospholipids within lysosomes, is a pathological response observed following exposure to many drugs across multiple therapeutic groups. A clear mechanistic understanding of the causes and implications of this form of drug toxicity has remained elusive. We previously reported the discovery and characterization of a lysosome-specific phospholipase A2 (PLA2G15) and later reported that amiodarone, a known cause of drug-induced phospholipidosis, inhibits this enzyme. Here, we assayed a library of 163 drugs for inhibition of PLA2G15 to determine whether this phospholipase was the cellular target for therapeutics other than amiodarone that cause phospholipidosis. We observed that 144 compounds inhibited PLA2G15 activity. Thirty-six compounds not previously reported to cause phospholipidosis inhibited PLA2G15 with IC50 values less than 1 mM and were confirmed to cause phospholipidosis in an in vitro assay. Within this group, fosinopril was the most potent inhibitor (IC50 0.18 μM). Additional characterization of the inhibition of PLA2G15 by fosinopril was consistent with interference of PLA2G15 binding to liposomes. PLA2G15 inhibition was more accurate in predicting phospholipidosis compared with in silico models based on pKa and ClogP, measures of protonation, and transport-independent distribution in the lysosome, respectively. In summary, PLA2G15 is a primary target for cationic amphiphilic drugs that cause phospholipidosis, and PLA2G15 inhibition by cationic amphiphilic compounds provides a potentially robust screening platform for potential toxicity during drug development.
| S-EPMC8243516 | biostudies-literature
Project description:Bile salt interactions with phospholipid monolayers of fat emulsions are known to regulate the actions of gastrointestinal lipolytic enzymes in order to control the uptake of dietary fat. Specifically, on the lipid/aqueous interface of fat emulsions, the anionic portions of amphipathic bile salts have been thought to interact with and activate the enzyme group-IB phospholipase A2 (PLA2) derived from the pancreas. To explore this regulatory process, we have determined the crystal structures of the complexes of pancreatic PLA2 with the naturally occurring bile salts: cholate, glycocholate, taurocholate, glycochenodeoxycholate, and taurochenodeoxycholate. The five PLA2-bile salt complexes each result in a partly occluded active site, and the resulting ligand binding displays specific hydrogen bonding interactions and extensive hydrophobic packing. The amphipathic bile salts are bound to PLA2 with their polar hydroxyl and sulfate/carboxy groups oriented away from the enzyme's hydrophobic core. The impaired catalytic and interface binding functions implied by these structures provide a basis for the previous numerous observations of a biphasic dependence of the rate of PLA2 catalyzed hydrolysis of zwitterionic glycerophospholipids in the presence of bile salts. The rising or activation phase is consistent with enhanced binding and activation of the bound PLA2 by the bile salt induced anionic charge in a zwitterionic interface. The falling or inhibitory phase can be explained by the formation of a catalytically inert stoichiometric complex between PLA2 and any bile salts in which it forms a stable complex. The model provides new insight into the regulatory role that specific PLA2-bile salt interactions are likely to play in fat metabolism.
| S-EPMC1933606 | biostudies-literature
Project description:Human group IIA secretory phospholipase A(2) (hGIIA sPLA(2)) is reported to be involved in inflammation, since its expression level is enhanced under various inflammatory conditions. In this work, we report the total chemical synthesis of this enzyme (124 amino acids) by solid-phase method. The identity of the protein, in denatured or folded (7 disulphide bonds) forms, was confirmed by electrospray MS. Synthetic sPLA(2) possesses the same circular dichroism spectrum, enzymic activity in hydrolysing different phospholipid substrates, and inhibitory effect in thrombin formation from prothrombinase complex as the recombinant sPLA(2). Furthermore, LY311727, a reported specific hGIIA sPLA(2) inhibitor, is able to inhibit the synthetic and the recombinant enzymes with the same efficiency. This study demonstrates that chemically continuous solid phase synthesis is an alternative and less time-consuming approach to producing small, structurally folded and fully active proteins of up to 124 amino acids, such as hGIIA sPLA(2). Moreover, this technique provides more flexibility in analogue synthesis to elucidate their physiological functions and pathological effects.
| S-EPMC1222685 | biostudies-other
Project description:The long-standing proposal that phospholipase A2 (PLA2) enzymes are involved in rickettsial infection of host cells has been given support by the recent characterization of a patatin phospholipase (Pat2) with PLA2 activity from the pathogens Rickettsia prowazekii and R. typhi. However, pat2 is not encoded in all Rickettsia genomes; yet another uncharacterized patatin (Pat1) is indeed ubiquitous. Here, evolutionary analysis of both patatins across 46 Rickettsia genomes revealed 1) pat1 and pat2 loci are syntenic across all genomes, 2) both Pat1 and Pat2 do not contain predicted Sec-dependent signal sequences, 3) pat2 has been pseudogenized multiple times in rickettsial evolution, and 4) ubiquitous pat1 forms two divergent groups (pat1A and pat1B) with strong evidence for recombination between pat1B and plasmid-encoded homologs. In light of these findings, we extended the characterization of R. typhi Pat1 and Pat2 proteins and determined their role in the infection process. As previously demonstrated for Pat2, we determined that 1) Pat1 is expressed and secreted into the host cytoplasm during R. typhi infection, 2) expression of recombinant Pat1 is cytotoxic to yeast cells, 3) recombinant Pat1 possesses PLA2 activity that requires a host cofactor, and 4) both Pat1 cytotoxicity and PLA2 activity were reduced by PLA2 inhibitors and abolished by site-directed mutagenesis of catalytic Ser/Asp residues. To ascertain the role of Pat1 and Pat2 in R. typhi infection, antibodies to both proteins were used to pretreat rickettsiae. Subsequent invasion and plaque assays both indicated a significant decrease in R. typhi infection compared to that by pre-immune IgG. Furthermore, antibody-pretreatment of R. typhi blocked/delayed phagosomal escapes. Together, these data suggest both enzymes are involved early in the infection process. Collectively, our study suggests that R. typhi utilizes two evolutionary divergent patatin phospholipases to support its intracellular life cycle, a mechanism distinguishing it from other rickettsial species.
| S-EPMC3688537 | biostudies-literature
Project description:Altered epidermal differentiation along with increased keratinocyte proliferation is a characteristic feature of psoriasis and pityriasis rubra pilaris (PRP). However, despite this large degree of overlapping clinical and histologic features, the molecular signatures these skin disorders share are unknown. Using global transcriptomic profiling, we demonstrate that plaque psoriasis and PRP skin lesions have high overlap, with all differentially expressed genes in PRP relative to normal skin having complete overlap with those in psoriasis. The major common pathway shared between psoriasis and PRP involves the phospholipases PLA2G2F, PLA2G4D, and PLA2G4E, which were found to be primarily expressed in the epidermis. Gene silencing each of the 3 PLA2s led to reduction in immune responses and epidermal thickness both in vitro and in vivo in a mouse model of psoriasis, establishing their proinflammatory roles. Lipidomic analyses demonstrated that PLA2s affect mobilization of a phospholipid-eicosanoid pool, which is altered in psoriatic lesions and functions to promote immune responses in keratinocytes. Taken together, our results highlight the important role of PLA2s as regulators of epidermal barrier homeostasis and inflammation, identify PLA2s as a shared pathogenic mechanism between PRP and psoriasis, and as potential therapeutic targets for both diseases.
| S-EPMC8564909 | biostudies-literature
Project description:Increased lipoprotein-associated phospholipase A(2) (Lp-PLA(2)) activity is associated with increased risk of cardiac events, but it is not known whether Lp-PLA(2) is a causative agent. Here we show that selective inhibition of Lp-PLA(2) with darapladib reduced development of advanced coronary atherosclerosis in diabetic and hypercholesterolemic swine. Darapladib markedly inhibited plasma and lesion Lp-PLA(2) activity and reduced lesion lysophosphatidylcholine content. Analysis of coronary gene expression showed that darapladib exerted a general anti-inflammatory action, substantially reducing the expression of 24 genes associated with macrophage and T lymphocyte functioning. Darapladib treatment resulted in a considerable decrease in plaque area and, notably, a markedly reduced necrotic core area and reduced medial destruction, resulting in fewer lesions with an unstable phenotype. These data show that selective inhibition of Lp-PLA(2) inhibits progression to advanced coronary atherosclerotic lesions and confirms a crucial role of vascular inflammation independent from hypercholesterolemia in the development of lesions implicated in the pathogenesis of myocardial infarction and stroke.
| S-EPMC2885134 | biostudies-literature
Project description:BackgroundThe rate-limiting step in prostaglandin (PG) biosynthesis is catalyzed by phospholipase A2 (PLA2) enzymes which hydrolyze arachidonic acid from membrane phospholipids. Despite their importance in uterine PG production, little is known concerning the specific PLA2 enzymes that regulate arachidonic acid liberation in the uterine endometrium. The objectives of this study were to evaluate the expression and activities of calcium-independent Group VI and Group IVC PLA2 (PLA2G6 and PLA2G4C) and calcium-dependent Group IVA PLA2 (PLA2G4A) enzymes in the regulation of bovine uterine endometrial epithelial cell PG production.MethodsBovine endometrial epithelial cells in culture were treated with oxytocin, interferon-tau and the PLA2G6 inhibitor bromoenol lactone, alone and in combination. Concentrations of PGF2alpha and PGE2 released into the medium were analyzed. Western blot analysis was performed on cellular protein to determine the effects of treatments on expression of PLA2G4A, PLA2G6 and PLA2G4C. Group-specific PLA2 activity assays were performed on cell lysates following treatment with oxytocin, interferon-tau or vehicle (control), alone and in combination. To further evaluate the role of specific PLA2 enzymes in uterine cell PG biosynthesis, cells were transfected with cDNAs encoding human PLA2G6 and PLA24C, treated as described above and PG assays performed.ResultsConstitutive cell production of PGF2alpha was about two-fold higher than PGE2. Oxytocin stimulated production of both PGs but the increase of PGF2alpha was significantly greater. Interferon-tau diminished oxytocin stimulation of both PGs. The PLA2G6 inhibitor, bromoenol lactone, abolished oxytocin-stimulated production of PGF2alpha. Treatments had little effect on PLA2G4A protein expression. In contrast, oxytocin enhanced expression of PLA2G6 and this effect was diminished in the presence of interferon-tau. Expression of PLA2G4C was barely detectable in control and oxytocin treated cells but it was enhanced in cells treated with interferon-tau. Oxytocin stimulated PLA2 activity in assays designed to evaluate PLA2G6 activity and interferon-tau inhibited this response. In assays designed to measure PLA2G4C activity, only interferon-tau was stimulatory. Cells overexpressing PLA2G6 produced similar quantities of the two PGs and these values were significantly higher than PG production by non-transfected cells. Oxytocin stimulated production of both PGs and this response was inhibited by interferon-tau. Bromoenol lactone inhibited oxtocin stimulation of PGF2alpha production but stimulated PGE2 production, both in the absence and presence of oxytocin. Cells over-expressing PLA2G4C produced more PGE2 than PGF2alpha and interferon-tau stimulated PGE2 production.ConclusionResults from these studies indicate that oxytocin stimulation of uterine PGF2alpha production is mediated, at least in part, by up-regulation of PLA2G6 expression and activity. In addition to its known inhibitory effect on oxytocin receptor expression, interferon-tau represses oxytocin-stimulated PLA2G6 expression and activity and this contributes to diminished PGF2alpha production. Furthermore, endometrial cell PGE2 biosynthesis was associated with PLA2G4C expression and activity and interferon-tau was stimulatory to this process.
| S-EPMC1868772 | biostudies-literature