Comparative effects of indomethacin on cell proliferation and cell cycle progression in tumor cells grown in vitro and in vivo.

Considerable research effort is currently being directed towards understanding the mechanisms mediating the antiproliferative effects of non-steroidal anti-inflammatory drugs (NSAIDs) and, more recently, of cyclooxygenase (COX)-2 inhibitors as well. A key question is whether NSAIDs (excluding sulindac) exert their anticarcinogenic effects in vivo by a mechanism that is dependent on their capacity to inhibit COX activity. Some studies with cultured tumor cells in vitro have argued against such a linkage, showing that NSAIDs inhibit cell replication and/or augment apoptosis only at concentrations that exceed those required to inhibit COX activities 10- to 100-fold.

Kinetic analysis in mixed micelles of partially purified rat brain phospholipase D activity and its activation by phosphatidylinositol 4,5-bisphosphate.

A partially purified rat brain membrane phospholipase D (PLD) activity was characterized in a mixed micellar system consisting of 1-palmitoyl-2-[6-N-(7-nitrobenzo-2-oxa-1,3-diazol-4-yl)-amino]capr oyl-phosphatidylcholine (NBD-PC) and Triton X-100, under conditions where Triton X-100 has a surface dilution effect on PLD activity and the catalytic rate is dependent on the surface concentration (expressed in terms of molar ratio) of NBD-PC. PLD activity was specifically activated by phosphatidylinositol 4,5-bisphosphate (PIP2), and the curve of activation versus PIP2 molar ratio fitted a Michaelis-Menten equation with a K(act) value between molar ratios of 0.001-0.

Identification of a novel Ca2+-dependent, phosphatidylethanolamine-hydrolyzing phospholipase D in yeast bearing a disruption in PLD1.

We have previously reported the identification and partial characterization of a gene encoding a phospholipase D activity (PLD1) in the yeast, Saccharomyces cerevisiae. Here we report the existence of a second phospholipase D activity, designated PLD2, in yeast cells bearing disruption at the PLD1 locus. PLD2 is a Ca2+-dependent enzyme which preferentially utilizes phosphatidylethanolamine over phosphatidylcholine as a substrate.

Identification and characterization of a gene encoding phospholipase D activity in yeast.

We have identified an open reading frame on chromosome XI of the yeast, Saccharomyces cerevisiae, as encoding a protein with phospholipase D (PLD) activity. We have named this open reading frame, PLD1, and show that yeast bearing a disruption in this gene are unable to catalyze the hydrolysis of phosphatidylcholine. PLD1 encodes a hypothetical protein of 1683 amino acids and has a predicted molecular mass of 195 kDa.

Distinct mechanisms of phospholipase D activation and attenuation utilized by different mitogens in NIH-3T3 fibroblasts.

The activation of phospholipase D (PLD) by platelet-derived growth factor (PDGF), prostaglandin F2 alpha and 12-O-tetradecanoylphorbol 13-acetate (TPA) was studied in NIH-3T3 fibroblasts. PLD activation was determined by measuring the production of both [3H]phosphatidic acid and [3H]phosphatidylpropanol (products of the PLD-catalyzed hydrolysis and transphosphatidylation reactions, respectively), in cells that were metabolically pre-labeled with [3H]oleic acid. All mitogens caused a rapid (within 2 min) activation of PLD.