Secreted phospholipases A2, a new class of HIV inhibitors that block virus entry into host cells

Self Cite

317

506

Expression of the full set of human and mouse groups I, II, V, X, and XII secreted phospholipases A 2 (sPLA 2 s) in Escherichia coli and insect cells has provided pure recombinant enzymes for detailed comparative interfacial kinetic and binding studies. The set of mammalian sPLA 2 s display dramatically different sensitivity to dithiothreitol. The specific activity for the hydrolysis of vesicles of differing phospholipid composition by these enzymes varies by up to 4 orders of magnitude, and yet all enzymes display similar catalytic site specificity toward phospholipids with different polar head groups. Discrimination between sn-2 polyunsaturated versus saturated fatty acyl chains is <6-fold. These enzymes display apparent dissociation constants for activation by calcium in the 1-225 M range, depending on the phospholipid substrate. Analysis of the inhibition by a set of 12 active site-directed, competitive inhibitors reveals a large variation in the potency among the mammalian sPLA 2 s, with Me-Indoxam being the most generally potent sPLA 2 inhibitor. A dramatic correlation exists between the ability of the sPLA 2 s to hydrolyze phosphatidylcholine-rich vesicles efficiently in vitro and the ability to release arachidonic acid when added exogenously to mammalian cells; the group V and X sPLA 2 s are uniquely efficient in this regard.

Section: Discussionmentioning

confidence: 99%

Interfacial Kinetic and Binding Properties of the Complete Set of Human and Mouse Groups I, II, V, X, and XII Secreted Phospholipases A2

Singer¹,

Ghomashchi²,

Calvez³

et al. 2002

Self Cite

317

506

“…In addition to the cloned PLA 2 receptor, several binding proteins recognized by snake venom sPLA 2 s have been reported, although their molecular structures, endogenous ligands, and biological functions remain uncertain (4,56). Fenard et al (57) have recently reported the putative binding sites that might be involved in the venom sPLA 2 s-evoked suppression of HIV-1 virus entry into host cells. The possibility of sPLA 2 -IIE acting as a ligand for these binding sites also deserves attention in future studies.…”

Section: Figmentioning

confidence: 99%

Structures, Enzymatic Properties, and Expression of Novel Human and Mouse Secretory Phospholipase A2s

Suzuki

Ishizaki

Yokota

et al. 2000

163

131

Mammalian secretory phospholipase A 2 s (sPLA 2 s) form a family of structurally related enzymes that are involved in a variety of physiological and pathological processes via the release of arachidonic acid from membrane phospholipids or the binding to specific membrane receptors. Here, we report the cloning and characterization of a novel sPLA 2 that is the sixth isoform of the sPLA 2 family found in humans. The novel human mature sPLA 2 consists of 123 amino acids (M r ‫؍‬ 14,000) and is most similar to group IIA sPLA 2 (sPLA 2 -IIA) with respect to the number and positions of cysteine residues as well as overall identity (51%). Therefore, this novel sPLA 2 should be categorized into group II and called group IIE (sPLA 2 -IIE) following the recently identified group IID sPLA 2 (sPLA 2 -IID). The enzymatic properties of recombinant human sPLA 2 -IIE were almost identical to those of sPLA 2 -IIA and IID in terms of Ca 2؉ requirement, optimal pH, substrate specificity, as well as high susceptibility to the sPLA 2 inhibitor indoxam. Along with the biochemical properties of proteins, genetic and evolutional similarities were also observed among these three types of group II sPLA 2 s as to the chromosomal location of the human gene (1p36) and the exon/intron organization. The expression of sPLA 2 -IIE transcripts in humans was restricted to the brain, heart, lung, and placenta in contrast to broad expression profiles for sPLA 2 -IIA and -IID. In sPLA 2 -IIA-deficient mice, the expression of sPLA 2 -IIE was markedly enhanced in the lung and small intestine upon endotoxin challenge, which contrasted with the reduced expression of sPLA 2 -IID mRNA. In situ hybridization analysis revealed elevation of sPLA 2 -IIE mRNA at alveolar macrophage-like cells in the lung of endotoxin-treated mice. These findings suggest a distinct functional role of novel sPLA 2 -IIE in the progression of inflammatory processes.

“…In addition to the above evidence, it is becoming clear that sPLA 2 s are involved in a diverse set of physiological functions (7,(12)(13)(14). In the last few years, six mouse and five human sPLA 2 s structurally related to GIB and GIIA sPLA 2 s (mGIIC, hGIID, mGIID, hGIIE, mGIIE, mGIIF, hGIIF, hGV, mGV, hGX, and mGX) 2 have been identified (15)(16)(17)(18)(19)(20).…”

mentioning

confidence: 99%

Cloning and Recombinant Expression of a Structurally Novel Human Secreted Phospholipase A2

Gelb¹,

Valentin²,

Ghomashchi³

et al. 2000

Self Cite

159

152

Mammals contain a diverse set of secreted phospholipases A 2 (sPLA 2 s) that liberate arachidonic acid from phospholipids for the production of eicosanoids and exert a variety of physiological and pathological effects. We report the cloning, recombinant expression, and kinetic properties of a novel human sPLA 2 that defines a new structural class of sPLA 2 s called group XII. The human group XII (hGXII) cDNA contains a putative signal peptide of 22 residues followed by a mature protein of 167 amino acids that displays homology to all known sPLA 2 s only over a short stretch of amino acids in the active site region. Northern blot and reverse transcription-polymerase chain reaction analyses show that the tissue distribution of hGXII is distinct from the other human sPLA 2 s with strong expression in heart, skeletal muscle, kidney, and pancreas and weaker expression in brain, liver, small intestine, lung, placenta, ovaries, testis, and prostate. Catalytically active hGXII was produced in Escherichia coli and shown to be Ca 2؉ -dependent despite the fact that it is predicted to have an unusual Ca 2؉ -binding loop. Similar to the previously characterized mouse group IIE sPLA 2 s, the specific activity of hGXII is low in comparison to that of other mammalian sPLA 2 , suggesting that hGXII could have novel functions that are independent of its phospholipase A 2 activity.