Determination of the Activity of Phospholipases A, C, and D

Grossman, Shlomo; Oestreicher, Guillermo; Singer, Thomas P.

doi:10.1002/9780470110423.ch4

Cited by 27 publications

(2 citation statements)

References 110 publications

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“…The reaction products of ACT-PLA activity on plasma membrane phospholipids are lysophospholipids and free fatty acids [ 55 ]. Lysophospholipids, with its positive spontaneous curvature, have been proved to induce in membranes formation of hydrophilic permeable proteolipidic “toroidal pores” in which amphipathic peptides and proteins are inserted.…”

Section: Intrinsic Phospholipase a Activity Of Act And Its Role Inmentioning

confidence: 99%

Understanding the Mechanism of Translocation of Adenylate Cyclase Toxin across Biological Membranes

Ostolaza

Martı́n

González-Bullón

et al. 2017

Toxins

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Adenylate cyclase toxin (ACT) is one of the principal virulence factors secreted by the whooping cough causative bacterium Bordetella pertussis, and it has a critical role in colonization of the respiratory tract and establishment of the disease. ACT targets phagocytes via binding to the CD11b/CD18 integrin and delivers its N-terminal adenylate cyclase (AC) domain directly to the cell cytosol, where it catalyzes unregulated conversion of cytosolic ATP into cAMP upon activation by binding to cellular calmodulin. High cAMP levels disrupt bactericidal functions of the immune cells, ultimately leading to cell death. In spite of its relevance in the ACT biology, the mechanism by which its ≈400 amino acid-long AC domain is transported through the target plasma membrane, and is released into the target cytosol, remains enigmatic. This article is devoted to refresh our knowledge on the mechanism of AC translocation across biological membranes. Two models, the so-called “two-step model” and the recently-proposed “toroidal pore model”, will be considered.

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Section: Intrinsic Phospholipase a Activity Of Act And Its Role Inmentioning

confidence: 99%

Understanding the Mechanism of Translocation of Adenylate Cyclase Toxin across Biological Membranes

Ostolaza

Martı́n

González-Bullón

et al. 2017

Toxins

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show abstract

“…Prediction models of suicide attempts have either used latent predictors exclusively or in combination with manifest predictors, such as sociodemographic characteristics, school performance, peer relations, drug use, parent relations, and contact with suicidal behavior (e.g. De Wilde, Kienhorst, Diekstra, & Wolters, 1992;Dubow, Kausch, Blum, Reed, & Bush, 1989;Garfinkel, Froese, & Hood, 1982;Grossman, Milligan, & Deyo, 1991;Holinger, Offer, & Zola, 1988;Kienhorst, Diekstra, & Wolters, 1991;Philip & McCulloch, 1966;Smith & Crawford, 1986). Manifest p r e dictors can, in principle, be directly observed or at least be efficiently used to prescreen for suicide attempters in large populations without asking potential suicide attempters threatening questions that could cause them emotional distress.…”

mentioning

confidence: 99%

Manifest Predictors of Past Suicide Attempts in a Population of Icelandic Adolescents

Bjarnason,

Thorlindsson

1994

Suicide & Life Threat Behav

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Past suicide attempts have been found to be a major risk factor for both repeated attempts and completed suicide. The utility of this is, however, limited by the fact that the majority of all suicide attempts never come to professional attention. This paper explores the possibility of using manifest indicators to predict which individuals in a population of adolescents have attempted suicide. Using logistic regression, manifest predictors in the categories of school, leisure, peer and parent relations, consumption, and contact with suicidal behavior could identify either a quarter of the population containing three quarters of all suicide attempters or 2% of the population where two thirds of those predicted actually had attempted suicide. It is thus concluded that manifest predictors can complement psychiatric screening methods by efficiently reducing the number to be screened.

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Studies of phospholipase A₂ related to the hamster sperm acrosome reaction

1982

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This report describes studies of innate and exogenous phospholipase A2 related to the acrosome reaction of golden hamster cauda epididymal sperm in vitro. Two acrosome reaction-inducing systems were used: a nonsynchronous system with epinephrine, and a synchronous system with the protonionophore FCCP. After a high percentage of sperm had undergone AR (in both systems) an increased phosphatidylcholine hydrolyzing activity was found in incubation media supernatants after partial purification by Affi-Gel Blue chromatography. A preliminary characterization demonstrates that the activity was stimulted by Ca2+, detectable at pH 7.4-7.8, but not at pH 4.5, and inhibited by p-bromophenacyl bromide and mepacrine. Thus, it appears that a phospholipase A2 was released as a result of the acrosome reaction. BSA purified by TCA precipitation and ethanol resolubilization (TCA-BSA), utilized in both types of incubations did not contain associated phospholipase A2 activity, but did contain an associated phosphatidylcholine hydrolyzing activity. The nonphospholipase A2 activity was removed by further purification of the TCA-BSA by Affi-Gel Blue chromatography, but the resulting highly purified TCA-BSA was still able to induce capacitation and acrosome reactions in hamster sperm at the same level as prior to column chromatography. Incubations of the sperm in the presence of a partially purified bee venom phospholipase A2 did not stimulate hamster sperm AR over control values in the presence of epinephrine, but did so in the absence of epinephrine (probably by mimicking the action of the innate sperm head phospholipase A2). These results provide further support to earlier studies from this laboratory suggesting the involvement of a sperm head phospholipase A2 as an important factor in the mammalian sperm acrosome reaction.The organized fusion and vesiculation of sperm head membranes known as the acrosome reaction is essential for mammalian fertilization (see reviews by Bedford, '70, Meizel, '78, Yanagimachi, '81). Phospholipases may play a role in membrane fusion events in somatic cells (see review by Bach, '74), and Lucy ('75) has hypothesized that the fusogen lysolecithin, a product of phospholipase A activity, could play a role in the acrosome reaction. Indeed, Allison and Hartree ('70) have reported the presence of a phosphatidylcholine hydrolyzing activity, presumably a phospholipase A, in mammalian sperm acrosomal extracts. Recent work from this laboratory (Lui and Meizel, '79) has shown that inhibitors of phospholipase Az can inhibit the hamster sperm acrosome reaction in vitro, thus presenting the first evidence suggesting that this enzyme has a role in the mammalian sperm acrosome reaction.If sperm phospholipase A2 participates directly in the acrosome reaction, the enzyme should be released by that event whether it is present in the acrosomal matrix, outer acrosoma1 membrane, or the overlying plasma membrane and whether it is soluble or membrane bound. The present report demonstrates that phospholipase A2 is releas...

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Determination of the Activity of Phospholipases A, C, and D

Cited by 27 publications

References 110 publications

Understanding the Mechanism of Translocation of Adenylate Cyclase Toxin across Biological Membranes

Understanding the Mechanism of Translocation of Adenylate Cyclase Toxin across Biological Membranes

Manifest Predictors of Past Suicide Attempts in a Population of Icelandic Adolescents

Studies of phospholipase A₂ related to the hamster sperm acrosome reaction

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Determination of the Activity of Phospholipases A, C, and D

Cited by 27 publications

References 110 publications

Understanding the Mechanism of Translocation of Adenylate Cyclase Toxin across Biological Membranes

Understanding the Mechanism of Translocation of Adenylate Cyclase Toxin across Biological Membranes

Manifest Predictors of Past Suicide Attempts in a Population of Icelandic Adolescents

Studies of phospholipase A2 related to the hamster sperm acrosome reaction

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Product

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Studies of phospholipase A₂ related to the hamster sperm acrosome reaction