Effects of polyamines and calcium and sodium ions on smooth muscle cytoskeleton-associated phosphatidylinositol (4)-phosphate 5-kinase
| Autor: | H, Chen, C B, Baron, T, Griffiths, P, Greeley, R F, Coburn |
|---|---|
| Rok vydání: | 1998 |
| Předmět: |
Phosphatidylinositol 4
5-Diphosphate Spermidine Swine Detergents Acrylic Resins Phosphatidic Acids Phosphatidylserines Cell Fractionation Phosphatidylinositols Substrate Specificity Adenosine Triphosphate Sarcolemma Polyamines Putrescine Animals Magnesium Cytoskeleton Heparin Sodium Anticoagulants Muscle Smooth Intracellular Membranes Hydrogen-Ion Concentration Phosphotransferases (Alcohol Group Acceptor) Ethanolamines Potassium Calcium Spermine Protein Binding |
| Zdroj: | Journal of cellular physiology. 177(1) |
| ISSN: | 0021-9541 |
| Popis: | In many different cell types, including smooth muscle cells (Baron et al., 1989, Am. J. Physiol., 256: C375-383; Baron et al., J. Pharmacol. Exp. Ther. 266: 8-15), phosphatidylinositol (4)-phosphate 5-kinase plays a critical role in the regulation of membrane concentrations of phosphatidylinositol (4,5)-bisphosphate and formation of inositol (1,4,5)-trisphosphate. In unstimulated porcine trachealis smooth muscle, 70% of total cellular phosphatidylinositol (4)-phosphate 5-kinase activity was associated with cytoskeletal proteins and only trace activity was detectable in isolated sarcolemma. Using two different preparations, we studied cytoskeleton-associated phosphatidyl inositol (4)-phosphate 5-kinase under conditions that attempted to mimic the ionic and thermal cytoplasmic environment of living cells. The cytoskeleton-associated enzyme, studied using phosphatidylinositol (4)-phosphate substrate concentrations that produced phosphatidylinositol 4,5-bisphosphate at about 10% of the maximal rate, was sensitive to free [Mg2+], had an absolute requirement for phosphatidylserine, phosphatidic acid, or phosphatidylinositol, and included type I isoforms. At 0.5 mM free [Mg2+], physiological spermine concentrations, 0.2-0.4 mM, increased phosphatidylinositol (4)-phosphate 5-kinase activity two to four times compared to controls run without spermine. The EC50 for spermine-evoked increases in activity was 0.17 +/- 0.02 mM. Spermine-evoked enzyme activity was a function of both free [Mg2+] and substrate concentration. Cytoskeleton-associated phosphatidylinositol (4)-phosphate 5-kinase was inhibited by free [Ca2+] over a physiological range for cytoplasm--10(-8) to 10(-5) M, an effect independent of the presence of calmodulin. Na+ over the range 20 to 50 mM also inhibited this enzyme activated by 5 mM Mg2+ but had no effect on spermine-activated enzyme. Na+, Ca2+, and spermine appear to be physiological modulators of smooth muscle cytoskeleton-bound phosphatidylinositol (4)-phosphate 5-kinase. |
| Databáze: | OpenAIRE |
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