Switch to
| Predicate | Object |
|---|---|
| rdf:type | |
| lifeskim:mentions | |
| pubmed:issue |
15
|
| pubmed:dateCreated |
1992-6-25
|
| pubmed:abstractText |
We demonstrated previously tyrosine phosphorylation-dependent modulation of phospholipase C-gamma 1 (PLC-gamma 1) catalytic activity (Nishibe, S., Wahl, M. I., Hernandez-Sotomayor, S. M. T., Tonks, N. K., Rhee, S. G., and Carpenter, G. (1990) Science 250, 1253-1256). The increase in PLC-gamma 1 catalytic activity in A-431 cells occurs rapidly, with maximal activation 5 min after epidermal growth factor (EGF) stimulation. Certain other growth factors (fibroblast growth factor, platelet-derived growth factor) also stimulate PLC-gamma 1 catalytic activity, whereas insulin does not. A similar increase in PLC-gamma 1 specific activity (2-3-fold) was observed in both soluble (cytosol) and particulate (membrane) preparations from EGF-treated cells. Tyrosine-phosphorylated PLC-gamma 1 was detected in both cytosol and membrane fractions in lysates from EGF-treated A-431 cells, but the proportion of tyrosine-phosphorylated PLC-gamma 1 was higher in the cytosol (approximately 50%) than in the membrane (approximately 20%). Because a micellar concentration of the non-ionic detergent Triton X-100 allows detection of the tyrosine phosphorylation-dependent increase in PLC-gamma 1 catalytic activity in this assay, we evaluated the kinetic properties of PLC-gamma 1, immunoprecipitated from cytosol of control or EGF-treated cells, using substrate, phosphatidylinositol 4,5-bisphosphate (PtdIns 4,5-P2), solubilized in Triton X-100 at various molar ratios. The behavior of the control enzyme differed from the EGF-activated enzyme with respect to both Ks and Km. The control enzyme has a 7.5-fold higher Ks value than the activated enzyme (1.5 mM as compared with 0.22 mM). Activation by EGF is also a positive allosteric modifier of PLC-gamma 1-catalyzed PtdIns 4,5-P2 hydrolysis, i.e. the activated enzyme displayed apparent Michalis-Menton kinetics, with a Km of 0.6 mol fraction PtdIns 4,5-P2, whereas the control enzyme displayed sigmoidal kinetics with respect to PtdIns 4,5-P2 hydrolysis. At low substrate mol fractions (e.g. 0.07), the reaction velocity of the control enzyme was 4-fold lower than the activated enzyme. However, at a high substrate mol fraction (e.g. 0.33), the estimated maximal reaction velocities (Vmax) for both forms of PLC-gamma 1 were equivalent. PLC-gamma 1 activity from both control and EGF-treated cells was stimulated by increasing nanomolar Ca2+ concentrations. Although the catalytic activity of PLC-gamma 1 from EGF-treated cells was greater than control PLC-gamma 1 at every Ca2+ concentration tested, the relative stimulation of activity was markedly greater at Ca2+ concentrations above approximately 300 nM.
|
| pubmed:grant | |
| pubmed:language |
eng
|
| pubmed:journal | |
| pubmed:citationSubset |
IM
|
| pubmed:chemical |
http://linkedlifedata.com/resource/pubmed/chemical/Detergents,
http://linkedlifedata.com/resource/pubmed/chemical/Epidermal Growth Factor,
http://linkedlifedata.com/resource/pubmed/chemical/Fibroblast Growth Factors,
http://linkedlifedata.com/resource/pubmed/chemical/Inositol 1,4,5-Trisphosphate,
http://linkedlifedata.com/resource/pubmed/chemical/Insulin,
http://linkedlifedata.com/resource/pubmed/chemical/Isoenzymes,
http://linkedlifedata.com/resource/pubmed/chemical/Octoxynol,
http://linkedlifedata.com/resource/pubmed/chemical/Phosphatidylinositol 4,5-Diphosphate,
http://linkedlifedata.com/resource/pubmed/chemical/Phosphatidylinositol Phosphates,
http://linkedlifedata.com/resource/pubmed/chemical/Platelet-Derived Growth Factor,
http://linkedlifedata.com/resource/pubmed/chemical/Polyethylene Glycols,
http://linkedlifedata.com/resource/pubmed/chemical/Type C Phospholipases,
http://linkedlifedata.com/resource/pubmed/chemical/Tyrosine
|
| pubmed:status |
MEDLINE
|
| pubmed:month |
May
|
| pubmed:issn |
0021-9258
|
| pubmed:author | |
| pubmed:issnType |
Print
|
| pubmed:day |
25
|
| pubmed:volume |
267
|
| pubmed:owner |
NLM
|
| pubmed:authorsComplete |
Y
|
| pubmed:pagination |
10447-56
|
| pubmed:dateRevised |
2011-11-17
|
| pubmed:meshHeading |
pubmed-meshheading:1316902-3T3 Cells,
pubmed-meshheading:1316902-Animals,
pubmed-meshheading:1316902-Catalysis,
pubmed-meshheading:1316902-Cell Membrane,
pubmed-meshheading:1316902-Chromatography, Gel,
pubmed-meshheading:1316902-Cytosol,
pubmed-meshheading:1316902-Detergents,
pubmed-meshheading:1316902-Enzyme Activation,
pubmed-meshheading:1316902-Epidermal Growth Factor,
pubmed-meshheading:1316902-Fibroblast Growth Factors,
pubmed-meshheading:1316902-Humans,
pubmed-meshheading:1316902-Inositol 1,4,5-Trisphosphate,
pubmed-meshheading:1316902-Insulin,
pubmed-meshheading:1316902-Isoenzymes,
pubmed-meshheading:1316902-Kinetics,
pubmed-meshheading:1316902-Mice,
pubmed-meshheading:1316902-Octoxynol,
pubmed-meshheading:1316902-Phosphatidylinositol 4,5-Diphosphate,
pubmed-meshheading:1316902-Phosphatidylinositol Phosphates,
pubmed-meshheading:1316902-Phosphorylation,
pubmed-meshheading:1316902-Platelet-Derived Growth Factor,
pubmed-meshheading:1316902-Polyethylene Glycols,
pubmed-meshheading:1316902-Precipitin Tests,
pubmed-meshheading:1316902-Type C Phospholipases,
pubmed-meshheading:1316902-Tyrosine
|
| pubmed:year |
1992
|
| pubmed:articleTitle |
Growth factor stimulation of phospholipase C-gamma 1 activity. Comparative properties of control and activated enzymes.
|
| pubmed:affiliation |
Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, Tennessee 37232-0146.
|
| pubmed:publicationType |
Journal Article,
Comparative Study,
Research Support, U.S. Gov't, P.H.S.
|