Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.1.4.3 (phospholipase C)
18,461 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Possible interactions between polymerized (F-) actin and insulin-storage granules from rat islets of Langerhans were examined in vitro by comparing the sedimentation of the granules in the presence of various actin concentrations. Actin in the concentration range 0.1--0.5 mg/ml produced a retardation in granule-sedimentation rates consistent with binding of the granules to the actin filaments. The interaction was increased by addition of ATP (2mM), but was decreased by CaCl2 (0.1 mM). Binding of granules to actin was unaffected by cyclic AMP or by preincubation of the granules with phospholipase C. Specificity of the interaction was confirmed by the use of depolymerized (G-) actin and of myosin to provide a solution of comparable viscosity; neither of these caused any alteration of granule sedimentation. Possible implications of this interaction of insulin-storage granules with actin for the mechanism of insulin secretion are briefly discussed.
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PMID:Interaction between insulin-storage granules and F-actin in vitro. 22 Sep 62

Didansyl derivatives of amino acids and N-phenyl-1-naphthylamine were used to localize membrane hydrophobic sites in glycerol-extracted chicken skeletal muscle fibers. Epifluorescence microscopy revealed that such sites coincide with the distribution of mitochondria, the transverse tubular (T) system and the sarcoplasmic reticulum (SR). They are specifically associated with myofibril Z lines and occasionally extend from one Z plane to the next longitudinally along the muscle fiber. The hydrophobic probes interact noncovalently with the Z lines, and their induced fluorescence can be eliminated by exposure of the myofibrils to ionic detergents, nonionic detergents, or phospholipase C, before or after addition of the hydrophobic label. Extraction of glycerinated fibers with 0.6 M KI removes the majority of sarcomeric actin and myosin and leaves a scaffold of longitudinally interconnected Z planes. Membrane fluorescence remains tightly associated with these Z planes and with the remnant mitochondria. Shearing of such scaffolds results in the cleavage of the longitudinal connections and the production of large sheets of interconnected, close-packed Z discs in a honeycomb-like array. Comparison of the localization of two Z disc proteins, desmin and alpha-actinin, with that of the membrane material reveals that alpha-actinin is localized in the interior of each myofibril Z disc whereas both desmin and the membrane material surround each disc. Thus, glycerination and KI extraction of muscle fibers leaves remnants of T system and SR membranes tightly associated with the Z disc honeycomb lattice. Because the Z discs are connected at their peripheries through the T system appear to the plasma membrane, desmin and this membrane structure appear to be connected throughout the whole Z plane up to and including the plasma membrane. The congruent localization of desmin and the T system strongly suggests that this molecule mediates the adhesion of this membrane system around each Z disc.
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PMID:Fluorescent localization of membrane sites in glycerinated chicken skeletal muscle fibers and the relationship of these sites to the protein composition of the Z disc. 35 93

Clostridium novyi alpha-toxin caused retraction and rounding of cultured endothelial cells from porcine pulmonary arteries; nevertheless, the endothelial cells firmly adhered to their supports. F-actin stained with fluorescein-labeled phalloidin was condensed around the nucleus, whereas intermediate filaments and microtubules appeared unchanged. The content of F-actin and myosin was decreased, but that of G-actin or vimentin was not. A predominant role of the microfilament system in C. novyi alpha-toxin cytopathic action is suggested.
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PMID:Morphological and biochemical study of cytoskeletal changes in cultured cells after extracellular application of Clostridium novyi alpha-toxin. 161 67

The mechanism of G protein-mediated sensitization of the contractile apparatus of smooth muscle to Ca2+ was studied in receptor-coupled alpha-toxin-permeabilized rabbit portal vein smooth muscle. To test the hypothesis that Ca2+ sensitization is due to inhibition of myosin light-chain (MLC) phosphatase activity, we measured the effect of guanosine 5'-[gamma-thio]triphosphate and phenylephrine on the rate of MLC dephosphorylation in muscles preactivated with Ca2+ and incubated in Ca(2+)- and ATP-free solution containing 1-(5-chloronaphthalene-1-sulfonyl)-1H-hexahydro-1,4-diazepine (ML-9) to block MLC kinase activity. Guanosine 5'-[gamma-thio]triphosphate alone (300 microM) or in combination (3 microM) with phenylephrine decreased the rates of relaxation and dephosphorylation of MLC to about half of control values; this inhibition is sufficient to account for maximal G protein-mediated Ca2+ sensitization of MLC phosphorylation. The rate of thiophosphorylation of MLC with adenosine 5'-[gamma-thio]-triphosphate was not affected by guanosine 5'-[gamma-thio]triphosphate. We suggest that inhibition of protein phosphatase(s) by G protein(s) may have important regulatory functions.
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PMID:G protein-mediated inhibition of myosin light-chain phosphatase in vascular smooth muscle. 165 67

Chronic granulomatous diseases (CGDs) are characterized by recurrent infections resulting from impaired superoxide production by a phagocytic cell, nicotinamide adenine dinucleotide phosphate (reduced) (NADPH) oxidase. Complementary DNAs were cloned that encode the 67-kilodalton (kD) cytosolic oxidase factor (p67), which is deficient in 5% of CGD patients. Recombinant p67 (r-p67) partially restored NADPH oxidase activity to p67-deficient neutrophil cytosol from these patients. The p67 cDNA encodes a 526-amino acid protein with acidic middle and carboxyl-terminal domains that are similar to a sequence motif found in the noncatalytic domain of src-related tyrosine kinases. This motif was recently noted in phospholipase C-gamma, nonerythroid alpha-spectrin (fodrin), p21ras-guanosine triphophatase-activating protein (GAP), myosin-1 isoforms, yeast proteins cdc-25 and fus-1, and the 47-kD phagocyte oxidase factor (p47), which suggests the possibility of common regulatory features.
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PMID:Cloning of a 67-kD neutrophil oxidase factor with similarity to a noncatalytic region of p60c-src. 169 59

In this study we have used several complementary techniques to isolate and characterize a lymphoma membrane-associated 41-kDa protein that shares a number of structural and functional similarities with the alpha i subunit of the guanosine 5'-triphosphate (GTP)-binding protein (e.g., Gi alpha-like protein). In addition, using permeabilized lymphoma cells, we have found that: 1) GTP or GTP-tau-S augments, and pertussis toxin inhibits, phospholipase C (PLC) activity and receptor capping; and 2) the addition of lymphoma 41-kDa Gi alpha-like protein stimulates PLC activity and receptor patching/capping, and reverses the inhibitory effect of pertussis toxin on both activity and receptor patching/capping. Additional cytochemical and biochemical data indicate that the lymphoma 41-kDa protein is closely associated with several cytoskeletal proteins (e.g., actin, myosin, and fodrin) all of which colocalize under receptor cap structures. Furthermore, both the 41-kDa-mediated phospholipase C activity and receptor patching/capping are inhibited by cytochalasin D (a microfilament disrupting drug) and W-7 drug (a calmodulin inhibitor). Together, these data provide strong evidence for a functional association between the lymphoma membrane cytoskeleton and the 41-kDa (Gi alpha-like) protein. Specifically, this association appears to be required for the activation of phospholipase C that results in inositol triphosphate production, subsequent internal Ca2+ release, and finally surface receptor patching and capping.
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PMID:Interactions between a lymphoma membrane-associated guanosine 5'-triphosphate-binding protein and the cytoskeleton during receptor patching and capping. 196 26

1. Flash photolysis of caged compounds of phenylephrine, inositol 1, 4, 5 trisphosphate (InsP3), GTP gamma S, ATP, and CTP has been successfully used to study excitation-contraction coupling, contractile regulation, and contraction in smooth muscle. Major processes explored with this method were (a) the delay between agonist-receptor interaction and contraction and between the rise in InsP3, Ca2+ release and contraction; (b) the effect of myosin light chain phosphorylation on the rate of force development and the respective contributions of phosphorylation and crossbridge kinetics to differences between phasic and tonic smooth muscles; (c) the kinetics of the crossbridge cycle. We have also reviewed recent results obtained by other methods and bearing on the mechanisms of pharmacomechanical Ca2+ release and modulation of the Ca2+ sensitivity of the regulatory/contractile apparatus. 2. The long delay (1.5 at 22 degrees C) following activation of alpha 1-adrenergic receptors through photolysis of caged phenylephrine and the high Q10 of this process are consistent with the hypothesis that activation of phospholipase C is the major mechanism of alpha-adrenergic pharmacomechanical Ca2+ release. 3. The delay between photolysis of caged InsP3 and Ca2+ release is short: 30 ms or less, while the latency of contraction is significant (0.3-0.5 s at 22 degrees C) and similar to the lag between the rise in [Ca2+]i and force development in intact smooth muscles. The latency of contraction following photolysis of caged ATP in permeabilized muscles in rigor, in the presence of Ca2+ and calmodulin, is similar, about 0.2-0.5 s at 22 degrees C. 4. In muscles in which the myosin light chains are maintained in a phosphorylated state during rigor, photolysis of caged ATP initiates contractions with a short delay (10 ms or less). This result and those summarized above (2 and 3) suggest that the major portion of the delay between agonist-receptor interaction and contraction is due to activation of phospholipase C and InsP3 production, and about 0.2-0.5 s of the delay (22 degrees C) can be ascribed to prephosphorylation reactions between Ca2+, calmodulin, and myosin light chain kinase, and/or to mechanical processes, or to the chemical kinetics of two-step reactions. 5. Force development from rigor, initiated by photolysis of caged ATP in the presence of Ca2(+)-calmodulin, is rate-limited by myosin light chain phosphorylation; it is significantly accelerated if the myosin light chains are already phosphorylated prior to photolysis.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Flash photolysis studies of excitation-contraction coupling, regulation, and contraction in smooth muscle. 218 79

An Acanthamoeba myosin heavy chain has been identified whose tail domain amino acid sequence distinguishes it from Acanthamoeba myosins IB, IC, and II. The gene for this novel myosin heavy chain spans approximately 6.8 kilobases, is split by 17 introns, and encodes a 177-kDa polypeptide. While the amino-terminal approximately 90 kDa of this polypeptide is highly similar to the globular head sequences of myosins I and II, its approximately 87-kDa tail domain shows essentially no similarity to the tail sequences of either type of myosin. The only exception to this is the carboxyl-terminal approximately 50-amino acid region of the polypeptide, which is homologous to the carboxyl termini of the myosins I. Interestingly, this approximately 50-residue segment has been shown to exist in a diverse family of cytoskeleton-associated proteins that include nonreceptor tyrosine kinases, phospholipase C gamma, and fodrin (Rodaway, A. R. F., Sternberg, M. J. E., and Bentley, D. L. (1989) Nature 342, 624). Sequence analysis indicates that the tail domain of this new myosin is incapable of forming a myosin II-like coiled-coil structure, implying that the protein is single-headed and nonfilamentous. For this reason we have tentatively classified it as a high molecular weight form of myosin I (HMWMI). To determine if HMWMI exists in cells, antiserum was raised against a bacterially expressed fusion peptide made using a cDNA clone encoding most of the unique HMWMI tail domain. This antiserum does not recognize Acanthamoeba myosins IB, IC, or II but does recognize a single polypeptide in whole cell extracts with the mobility predicted for the HMWMI heavy chain. This protein is precipitated from crude extracts using F-actin and released from the pellet by ATP, supporting its classification as a member of the myosin family of proteins.
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PMID:A new Acanthamoeba myosin heavy chain. Cloning of the gene and immunological identification of the polypeptide. 224 10

Platelet activation induced by NaF or fluoroaluminate (AlF4-) was studied. The latter has been described to substitute for the gamma-phosphate group of the GTP molecule. With 10 mM-NaF, a concentration unable to induce any measurable Ca2+ mobilization (as measured with Indo 1), addition of AlCl3 potentiated platelet aggregation, thromboxane synthesis, diacylglycerol formation and p43 phosphorylation, without any increase in intracellular Ca2+. Neither phosphoinositide hydrolysis nor phosphatidic acid formation could be detected. AlF4- induced the release through a granule centralization within a microtubule bundle, although no myosin light-chain phosphorylation could be detected. Addition of flurbiprofen (10 microM) resulted in only partial inhibition of diacylglycerol formation, with no effect on the release reaction or on p43 phosphorylation. The present results suggest that AlF4- does not stimulate a G-protein governing the phosphoinositide-specific phospholipase C. The AlF4(-)-induced diacylglycerol formation is discussed. Moreover, these results bring evidence that there is no correlation between granule centralization and myosin light-chain phosphorylation.
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PMID:How does fluoroaluminate activate human platelets? 230 76

In yeast, the cortical actin cytoskeleton seems to specify sites of growth of the cell surface. Because the actin-binding protein ABP1p is associated with the cortical cytoskeleton of Saccharomyces cerevisiae, it might be involved in the spatial organization of cell surface growth. ABP1p is localized to the cortical cytoskeleton and its overproduction causes assembly of the cortical actin cytoskeleton at inappropriate sites on the cell surface, resulting in delocalized surface growth. We have now cloned and sequenced the gene encoding ABP1p. ABP1p is a novel protein with a 50 amino-acid C-terminal domain that is very similar to the SH3 domain in the non-catalytic region of nonreceptor tyrosine kinases (including those encoded by the proto-oncogenes c-src and c-abl), in phospholipase C gamma and in alpha-spectrin. We also identified an SH3-related motif in the actin-binding tail domain of myosin-I. The identification of SH3 domains in a family of otherwise unrelated proteins that associate with the membrane cytoskeleton indicates that this domain might serve to bring together signal transduction proteins and their targets or regulators, or both, in the membrane cytoskeleton.
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PMID:Homology of a yeast actin-binding protein to signal transduction proteins and myosin-I. 240 79


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