Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UNIPROT:P00750 (PLA)
 16,800 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Streptokinase, an extracellular protein produced by Streptococci, is capable of activating the human fibrinolytic zymogen plasminogen. The rate of amidolytic activity of the plasminogen-streptokinase complex is greatly diminished by micromolar concentrations of ATP and heparin oligosaccharides. In addition, the plasminogen activator activity of the plasminogen-streptokinase complex is also inhibited by these effectors. ATP and heparin oligosaccharides show structural similarity, suggesting that the inhibition is caused by binding of these molecules to a common newly formed binding pocket in streptokinase, which appears after interaction with plasminogen. Addition of the bivalent cations Ca2+ and Mg2+ reverses the inhibition caused by ATP and heparin. In the presence of ATP and bivalent cations, the complex between plasminogen and streptokinase develops an autophosphorylating activity whose target is the sequence LTSRPAHG in the 4.5 kDa streptokinase N-terminal peptide, which is an early autolysis peptide. This streptokinase N-terminal peptide, which is essential for streptokinase activating activity, may serve, once phosphorylated, in mechanisms related to the pathogenicity of Streptococci. These studies suggest a critical role for plasminogen in regulating the activity of the streptokinase molecule.
 ...
PMID:ATP-regulated activity of the plasmin-streptokinase complex: a novel mechanism involving phosphorylation of streptokinase. 854 80

The regulation of peroxisomal motility was investigated both in CHO cells and in cells derived from human umbilical vein endothelium (HUE). The cells were transfected with a construct encoding the green fluorescent protein bearing the C-terminal peroxisomal targeting signal 1. Kinetic analysis following time-lapse imaging revealed that CHO cells respond to simultaneous stimulation with ATP and lysophosphatidic acid (LPA) by reducing peroxisomal movements. When Ca(2+) was omitted from the extracellular medium or the cells were incubated with inhibitors for heterotrimeric G(i)/G(o) proteins, phospholipase C, classical protein kinase C isoforms (cPKC), mitogen-activated protein kinase kinase (MEK) or phospholipase A(2) (PLA(2)), this signal-mediated motility block was abolished. HUE cells grown to confluency on microporous membranes responded similarly to ATP-LPA receptor co-stimulation, but only when the ligands had access to the basolateral membrane region. These data demonstrate that peroxisomal motility is subject to specific modulation from the extracellular environment and suggest a receptor-mediated signaling cascade comprising Ca(2+) influx, G(i)/G(o) proteins, phospholipase C, cPKC isoforms, MEK and PLA(2) being involved in the regulation of peroxisomal arrest.
 ...
PMID:Receptor-mediated regulation of peroxisomal motility in CHO and endothelial cells. 1052 92

Isolated rat hepatocytes were suspended and stored in either Liebovitz-15 medium (37 degrees C or 4 degrees C) or University of Wisconsin (UW) solution (4 degrees C) containing [(3)H] arachidonic acid (AA). At varying times, membrane phospholipids were separated by thin layer chromatography. AA labeled phospholipids similarly at both 4 degrees C and 37 degrees C. Analysis of the ratios of [(3)H] AA and [(14)C] glycerol incorporated into phosphatidic acid or other phospholipids in dual-labeled cells indicated that the deacylation/reacylation cycle was the major route of AA incorporation at hypothermia. This was supported by showing that blocking phospholipase A(2) (PLA(2)) activity by trifluoperazine suppressed AA incorporation into phospholipids. PLA(2) activity, measured by determining the release of AA, was slow during 48-hour cold storage, but increased significantly when ATP was depleted by inhibition of mitochondria and glycolysis. In the whole rat liver, there was no significant loss of phospholipids during 48-hour storage (total phospholipids [micromol phosphorus/L/mg] : 0.197 +/-. 001 at 0 hours) unless energy blockers were used (0.155 +/-.005 at 48 hours) or glycogen depleted by fasting the rat (0.167 +/-.001 at 48 hours). This study shows that a net PLA(2) stimulated hydrolysis of phospholipids is seen only when ATP is depleted and its generation from anaerobic glycolysis inhibited. Thus, PLA(2) hydrolysis of phospholipids is not a significant cause of liver cell injury during cold storage when livers are obtained in optimal condition. However, conditions affecting the generation of ATP during cold storage could alter PLA(2) leading to membrane damage.
 ...
PMID:Phospholipid metabolism of hypothermically stored rat hepatocytes. 1053 45

Previously, we reported that emptying of intracellular Ca(2+) pools with endoplasmatic Ca(2+)-ATP-ase inhibitor thapsigargin leads to the Na(+) influx in human lymphocytes (M. Tepel et al., 1994, J. Biol. Chem. 269, 26239-26242). In the present study we examined the mechanism underlying the thapsigargin-induced Na(+) entry. We found that the thapsigargin-induced increase in Na(+) concentration was effectively inhibited by three structurally unrelated phospholipase A(2) (PLA(2)) inhibitors, p-bromophenacyl bromide, 3-(4-octadecyl)-benzoylacrylic acid (OBAA), and bromoenol lactone (BEL). The thapsigargin-induced Na(+) influx could be mimicked by PLA(2) exogenously added to the lymphocyte suspension. In addition, thapsigargin stimulated formation of arachidonic acid (AA), the physiological PLA(2) product. AA induced Na(+) entry in a time- and concentration-dependent fashion. Both, thapsigargin-induced Na(+) influx and AA liberation were completely inhibited in the presence of tyrosine kinase inhibitor genistein but not in the absence of extracellular Ca(2+). Collectively, these data show that thapsigargin-induced Na(+) entry is associated with tyrosine kinase-dependent stimulation of PLA(2).
 ...
PMID:Phospholipase A(2) is involved in thapsigargin-induced sodium influx in human lymphocytes. 1066

The signal transduction involved in the purinergic stimuli-induced activation of protein kinase C (PKC) in CHO-K1 cells was investigated. Purinergic stimuli such as adenosine triphosphate and uridine triphosphate induced a transient translocation of PKC epsilon, gamma, and delta from the cytoplasm to the plasma membrane. These translocations were blocked by an inhibitor of phosphatidylinositol-specific phospholipase C (PLC), but not by an inhibitor of phosphatidylcholine-specific PLC. A diacylglycerol (DAG) analogue also induced reversible translocations of PKC gamma, epsilon, and delta from the cytoplasm to the plasma membrane, while the calcium ionophore A23187 caused a similar translocation of only the gamma subtype. These results confirm that the hydrolysis of phosphatidylinositol-2-phosphate by PLC and the subsequent generation of DAG and increase in Ca(2+ )are involved in the purinergic stimuli-induced translocation of PKC. A DAG antagonist, 1-o-hexadecyl-2-o-acetyl-glycerol, blocked the DAG analogue-induced translocations of all PKC subtypes tested but failed to inhibit the purinergic stimuli-induced translocations of PKC epsilon and gamma. The DAG antagonist could not block the ATP- and UTP-induced translocation of PKC epsilon even in the absence of extracellular Ca(2+). Co-application of the DAG antagonist and a phospholipase A(2) (PLA(2)) inhibitor such as aristolochic acid, arachidonyltrifluoromethyl ketone, or bromoenol lactone inhibited the purinergic receptor-mediated translocation of PKC epsilon although each PLA(2) inhibitor alone did not block the translocation. In contrast to the epsilon subtype, ATP-induced translocation of PKC gamma was observed in the presence of both the PLA(2) inhibitor and the DAG antagonist. However, it is noteworthy that re-translocation of PKC gamma was hastened by the PLA(2) inhibitor. Furthermore products of PLA(2), such as lysophospholipids and fatty acids, induced the translocation of PKC gamma and epsilon in a dose dependent manner, but not delta. These results indicate that, in addition to PLC and DAG, PLA(2) and its products are involved in the purinergic stimuli-induced translocation of PKC epsilon and gamma in CHO-K1 cells. Each subtype of PKC in CHO-K1 cell is individually activated in response to a purinergic stimulation.
 ...
PMID:Phospholipase A(2) and its products are involved in the purinergic receptor-mediated translocation of protein kinase C in CHO-K1 cells. 1072 17

We investigated the mechanism of phospholipase A(2) (PLA(2)) activation in response to the P2 receptor agonist ATP in rat thyroid FRTL-5 cells. The PLA(2) activity was determined by measuring the release of [(3)H]-arachidonic acid (AA) from prelabeled cells. ATP evoked a dose- and time-dependent AA release. This release was totally inhibited by pertussis toxin (PTX) treatment, indicating the involvement of a G(i)/G(o) protein. The AA release was also diminished by chelating extracellular Ca(2+) with EGTA or by inhibiting influx of Ca(2+) using Ni(2+). Although the activation of protein kinase C (PKC) by 12-phorbol 13-myristate acetate (PMA) alone did not induce any AA release, the ATP-evoked AA release was significantly reduced when PKC was inhibited by GF109203X or by a long incubation with PMA to downregulate PKC. Both the ATP-evoked AA release and the mitogen-activated protein kinase (MAP kinase) phosphorylation were decreased by the MAP kinase kinase (MEK) inhibitor PD98059. Furthermore, the ATP-evoked MAP kinase phosphorylation was also inhibited by GF109203X and by downregulation of PKC, suggesting a PKC-mediated activation of MAP kinase. Inhibiting Src-like kinases by PP1 attenuated both the MAP kinase phosphorylation and the AA release. These results suggest that these kinases are involved in the regulation of MAP kinase and PLA(2) activation. Elevation of intracellular cAMP by TSH or by dBucAMP did not induce a phosphorylation of MAP kinase. Furthermore, neither the ATP-evoked AA release nor the MAP kinase phosphorylation were attenuated by TSH or dBucAMP. Taken together, our results suggest that ATP regulates the activation of PLA(2) by a G(i)/G(o) protein-dependent mechanism. Moreover, Ca(2+), PKC, MAP kinase, and Src-like kinases are also involved in this regulatory process.
 ...
PMID:Extracellular ATP-mediated phospholipase A(2) activation in rat thyroid FRTL-5 cells: regulation by a G(i)/G(o) protein, Ca(2+), and mitogen-activated protein kinase. 1073 91

This study was attempted to characterize pharmacologically the P2Y receptors triggering phospholipase A(2) (PLA(2)) activation in ampulla from frog semicircular canal. A microassay was developed to screen the abilities of UTP analogs to stimulate [(3)H]arachidonic acid release by labeled ampullas. At 26 degrees C UTP induced a dose-dependent and saturable increase of PLA(2) activity (apparent activation constant 1.3 +/- 0.4 microM, Hill coefficient 0.9 +/- 0.2, maximal stimulating factor 2.0 +/- 0.1). The rank order of potency of agonists for PLA(2) activation was UTP > or = UDP > adenosine 5'-O-(2-thiodiphosphate) = adenosine 5'-O-(3-thiotriphosphate) > or = ATP = 2-methylthio-ATP > or = ADP = diadenosine tetraphosphate > or = alpha,beta-methylene-ATP = CTP > 2' and 3'-O-(4-benzoylbenzoyl)-ATP > or = AMP = UMP >> uridine and adenosine. UTP- and 2-methylthio-ATP-induced PLA(2) activations were inhibited by U-73122, GF-109203X, and methyl arachidonyl fluorophosphate. Basal activity was stimulated by phorbol ester and epinephrine and reduced by vasotocin, isoproterenol, prostaglandin E(2), cAMP, and forskolin. H-89 restored the cAMP- and forskolin-inhibited PLA(2) activities. Results indicate that P2Y receptor-mediated PLA(2) stimulation requires phopholipase C and protein kinase C activations and basal activity is inhibited by agonist-stimulated cAMP-dependent mechanisms.
 ...
PMID:Purine and pyrimidine nucleotide-sensitive phospholipase A(2) in ampulla from frog semicircular canal. 1120 83

Phospholipase A(2) (PLA(2)) enzymes may play a role in cellular injury due to ATP depletion. Renal Madin-Darby canine kidney cells were subjected to ATP depletion to assess the effects of cellular energy metabolism on cytosolic PLA(2) (cPLA(2)) regulation. ATP depletion results in a decrease in soluble cPLA(2) activity and an increase in membrane-associated activity, which is reversed upon restoration of ATP levels by addition of dextrose. In ATP-depleted cells cPLA(2) mass shifts from cytosol to nuclear fractions. GFP-cPLA(2) is localized at the nuclear membrane of stably transfected ATP-depleted LLC-PK(1) cells under conditions where [Ca(2+)](i) is known to increase. cPLA(2) translocation does not occur if the increase in [Ca(2+)](i) increase is inhibited. If [Ca(2+)](i) is allowed to increase when ATP is depleted and the cells are then lysed, cPLA(2) remains associated with nuclear fractions even if the homogenate [Ca(2+)] is markedly reduced. In contrast, cPLA(2), which becomes associated with the nucleus when [Ca(2+)](i) is increased using ionophore, readily dissociates from the nuclear fractions of ATP-replete cells upon reduction of homogenate [Ca(2+)]. Okadaic acid inhibits the ATP depletion-induced association of cPLA(2) with nuclear fractions. Thus energy deprivation results in [Ca(2+)]-induced nuclear translocation, which is partially prevented by a phosphatase inhibitor.
 ...
PMID:Nuclear translocation of cytosolic phospholipase A2 is induced by ATP depletion. 1139 12

We analyzed a recently reported (K. Seno, T. Okuno, K. Nishi, Y. Murakami, F. Watanabe, T. Matsuur, M. Wada, Y. Fujii, M. Yamada, T. Ogawa, T. Okada, H. Hashizume, M. Kii, S.-H. Hara, S. Hagishita, S. Nakamoto, J. Med. Chem. 43 (2000)) pyrrolidine-based inhibitor, pyrrolidine-1, against the human group IV cytosolic phospholipase A(2) alpha-isoform (cPLA(2)alpha). Pyrrolidine-1 inhibits cPLA(2)alpha by 50% when present at approx. 0.002 mole fraction in the interface in a number of in vitro assays. It is much less potent on the cPLA(2)gamma isoform, calcium-independent group VI PLA(2) and groups IIA, X, and V secreted PLA(2)s. Pyrrolidine-1 blocked all of the arachidonic acid released in Ca(2+) ionophore-stimulated CHO cells stably transfected with cPLA(2)alpha, in zymosan- and okadaic acid-stimulated mouse peritoneal macrophages, and in ATP- and Ca(2+) ionophore-stimulated MDCK cells.
 ...
PMID:A pyrrolidine-based specific inhibitor of cytosolic phospholipase A(2)alpha blocks arachidonic acid release in a variety of mammalian cells. 1147 87

Attempts were made to engineer the periplasm of Escherichia coli to an expression compartment of heterologous proteins in their native conformation. As a first approach the low-molecular-size additive L-arginine and the redox compound glutathione (GSH) were added to the culture medium. Addition of 0.4 M L-arginine and 5 mM reduced GSH increased the yield of a native tissue-type plasminogen activator variant (rPA), consisting of the kringle-2 and the protease domain, and a single-chain antibody fragment (scFv) up to 10- and 37-fold, respectively. A variety of other medium additives also had positive effects on the yield of rPA. In a second set of experiments, the effects of cosecreted ATP-independent molecular chaperones on the yields of native therapeutic proteins were investigated. At optimized conditions, cosecretion of E. coli DnaJ or murine Hsp25 increased the yield of native rPA by a factor of 170 and 125, respectively. Cosecretion of DnaJ also dramatically increased the amount of a second model protein, native proinsulin, in the periplasm. The results of this study are anticipated to initiate a series of new approaches to increase the yields of native, disulfide-bridged, recombinant proteins in the periplasm of E. coli.
 ...
PMID:Cosecretion of chaperones and low-molecular-size medium additives increases the yield of recombinant disulfide-bridged proteins. 1152 96


<< Previous 1 2 3 4 5 6 7 8 Next >>