Sossin W S, Schwartz J H
Center for Neurobiology and Behavior, Columbia University College of Physicians and Surgeons, New York, NY 10032.
Brain Res Mol Brain Res. 1994 Jul;24(1-4):210-8. doi: 10.1016/0169-328x(94)90134-1.
We examined the activation of protein kinase C (PKC) produced by phorbol esters in Aplysia nervous tissue. Translocation of PKC in intact ganglia requires higher concentrations of phorbol esters than would be expected from: (1) their affinity for Aplysia PKCs measured in vitro; (2) their physiological effects on cultured Aplysia neurons; and (3) their actions on PKC in synaptosomes. Although phorbol esters enter intact ganglia slowly, delayed access to neurons is insufficient to account for the high concentrations needed for translocation. Increasing accessibility to the neural components of ganglia increases the rate at which translocation occurs, but does not affect the concentration of phorbol ester required. We suggest that this might best be explained by the presence of a competitive inhibitor at the binding site for phorbol esters in PKC. An indication for an inhibitor is that the concentration of phorbol esters needed for translocation in homogenates of nervous tissue is markedly decreased by diluting the extract. Preliminary characterization shows that the inhibitory activity is unusual: in addition to being competitive with lipid activators, it is soluble and tissue-specific. This type of inhibitor may be an important regulator of protein phosphorylation by PKC in neurons.
我们研究了佛波酯在海兔神经组织中产生的蛋白激酶C（PKC）的激活情况。在完整神经节中PKC的转位所需的佛波酯浓度高于基于以下几点预期的浓度：（1）它们在体外对海兔PKC的亲和力；（2）它们对培养的海兔神经元的生理作用；（3）它们对突触体中PKC的作用。尽管佛波酯缓慢进入完整神经节，但延迟进入神经元不足以解释转位所需的高浓度。增加对神经节神经成分的可及性会增加转位发生的速率，但不影响所需佛波酯的浓度。我们认为，这最好用PKC中佛波酯结合位点存在竞争性抑制剂来解释。存在抑制剂的一个迹象是，通过稀释提取物，神经组织匀浆中转位所需的佛波酯浓度会显著降低。初步表征表明，这种抑制活性很不寻常：除了与脂质激活剂具有竞争性外，它是可溶的且具有组织特异性。这种类型的抑制剂可能是神经元中PKC介导的蛋白质磷酸化的重要调节剂。
