Effects of Ca2+, Mg2+, and depolarizing agents, on the 32Pi-labeling and degradation of phosphatidylinositols in rat brain synaptosomes
| Autor: | P. Leaky, G. V. Marinetti, T. W. Morris |
|---|---|
| Rok vydání: | 1993 |
| Předmět: |
Male
Phosphatidylinositol 4 5-Diphosphate Antimycin A Phosphatidylinositols Biochemistry Phospholipases A Phosphates Rats Sprague-Dawley Cellular and Molecular Neuroscience chemistry.chemical_compound Phospholipase A2 Phosphatidylinositol Phosphates Sodium fluoride Animals Magnesium Phosphatidylinositol Egtazic Acid Calcimycin Synaptosome Oxamic Acid biology Brain Inositol trisphosphate Depolarization General Medicine Rats EGTA Phospholipases A2 chemistry Biophysics biology.protein Sodium Fluoride lipids (amino acids peptides and proteins) Calcium Phosphorus Radioisotopes Synaptosomes |
| Zdroj: | Neurochemical research. 18(3) |
| ISSN: | 0364-3190 |
| Popis: | In isolated synaptosomes from rat brain, 100 microM antimycin A and 10 microM oxamic acid inhibit the 32Pi-labeling of phosphatidylinositol-4,5-bisphosphate (PIP2) and phosphatidylinositol-4-phosphate (PIP) by 90% and 95-99% respectively. 10 mM sodium fluoride inhibits the labeling by 50-60% and 10 mM A23187 inhibits the labeling by 63-70%. Phospholipase A2 inhibits the labeling of PIP2 and PIP by 93-94% and stimulates their degradation by 84-92%. Depolarization of synaptosomes with 75 mM K+ or 100 microM veratrine decreases the labeling of PIP2 and PIP by 66-74%. The decreased labeling results in large part from the Ca(2+)-dependent degradation of 32P-labeled PIP2 and PIP as shown by pulse-chase experiments in which PIP2 and PIP were prelabeled with 32Pi. Depolarization of synaptosomes results in the stimulation of 45Ca2+ uptake with the concomitant hydrolysis of PIP and PIP2. Addition of 1 mM Ca2+ accounts for 25% of the enhanced degradation whereas depolarization with 75 mM K+ accounts for 75% of the enhanced degradation of PIP2 and PIP. Depolarization with 100 mM veratrine results in a 223% increase in inositol trisphosphate as evidenced by stimulation of 45Ca2+ uptake. EGTA (10 mM) and Mg2+ (5-10 mM) inhibit the degradation of PIP and PIP2 and counteract the action of 1 mM Ca2+. Our data demonstrate that 45Ca2+, Mg2+, and membrane depolarization play an important role in the turnover of membrane phosphatidylinositols. |
| Databáze: | OpenAIRE |
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