Inhibition of NMDA-induced protein kinase C translocation by a Zn2+ chelator: implication of intracellular Zn2+.
The role of intracellular Zn2+ in the translocation of protein kinase C from cytosol to membrane fractions was examined by the [3H]phorbol 12,13-dibutyrate (PDBu) binding method in guinea pig cerebral synaptoneurosomes. N-methyl-D-aspartate (NMDA, 100 microM) and calcium ionophore A23187 (0.3-30 microM) decreased the binding activity in the cytosol with a concomitant increase in the membrane fractions. Pretreatment of synaptoneurosomes with a heavy metal chelator, N,N,N',N'-tetrakis-(2-pyridylmethyl)ethylenediamine (TPEN), inhibited the NMDA- and A23187-induced changes of the distribution of [3H]PDBu binding sites in cytosol and membrane fractions. The inhibitory effect of TPEN was negated by a preincubation of TPEN with equimolar Zn2+ but not by that with Ca2+. The addition of 500 microM Zn2+ to the lysate of synaptoneurosomes induced an increase of [3H]PDBu binding activity in the membrane fraction with a concomitant decrease in the cytosol fraction, as did 100 microM Ca2+. Low concentrations of Zn2+ (10 microM), which alone had no effect on the distribution of the binding, significantly enhanced the effect of 10 microM Ca2+ in the lysate. Under those conditions TPEN inhibited the Zn(2+)-potentiated Ca(2+)-dependent changes in the binding. These results suggest that intracellular Zn2+ is essential for the agonist-induced translocation of protein kinase C in guinea pig synaptoneurosomes.
Baba
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A
Department of Pharmacology, Faculty of Pharmaceutical Sciences, Osaka University, Japan.
Etoh
S
S
Iwata
H
H
D000818:Animals; D000001:Calcimycin / Q000494:pharmacology; D002132:Calcium Radioisotopes; D002413:Cations, Divalent / Q000494:pharmacology; D002540:Cerebral Cortex / Q000187:drug effects / Q000201:enzymology; D002614:Chelating Agents / Q000494:pharmacology*; D003600:Cytosol / Q000201:enzymology; D004533:Egtazic Acid / Q000494:pharmacology; D005029:Ethylenediamines / Q000494:pharmacology; D006168:Guinea Pigs; D066298:In Vitro Techniques; D008297:Male; D016202:N-Methylaspartate / Q000037:antagonists & inhibitors* / Q000494:pharmacology; D009474:Neurons / Q000187:drug effects / Q000201:enzymology; D015240:Phorbol 12,13-Dibutyrate / Q000494:pharmacology; D011493:Protein Kinase C / Q000378:metabolism*; D013574:Synaptosomes / Q000187:drug effects / Q000201:enzymology; D015032:Zinc / Q000494:pharmacology / Q000502:physiology*
D002132:Calcium Radioisotopes; D002413:Cations, Divalent; D002614:Chelating Agents; D005029:Ethylenediamines; D015240:Phorbol 12,13-Dibutyrate; D000001:Calcimycin; D004533:Egtazic Acid; D016202:N-Methylaspartate; D011493:Protein Kinase C; D015032:Zinc; C044387:N,N,N',N'-tetrakis(2-pyridylmethyl)ethylenediamine