Burry R W
Department of Cell Biology, Neurobiology and Anatomy, College of Medicine, The Ohio State University, Columbus 43210, USA.
J Neurosci Res. 1998 Jul 15;53(2):214-22. doi: 10.1002/(SICI)1097-4547(19980715)53:2<214::AID-JNR10>3.0.CO;2-6.
Nerve growth factor (NGF) stimulation of PC12 cells activates signaling pathways leading to new protein expression and growth of neurites. In wild type PC12 cells, incubation with phorbol ester (PMA) will activate protein kinase C (PKC) leading to the expression of many proteins necessary for neurite outgrowth, but this activation of PKC alone will not stimulate growth of long neurites. Here, we show in the subline of PC12-N09, which lacks NGF-stimulated growth of long neurites, that a brief incubation with PKC activators, PMA or bryostatin 1 (bryostatin), before NGF incubation, stimulates the growth of long neurites. However, incubation in the reverse order is ineffective. A short incubation with PMA or bryostatin followed by NGF induced tyrosine phosphorylation of MAP kinase (MAPK), which is of the same duration as that induced by NGF alone. Thus, PMA preincubation did not increase the length NGF activation of MAPK. Twenty-four hr after incubation with PMA or bryostatin, PKC isoforms were downregulated but PKC isoforms delta-, and epsilon- were still present. In these cells chronically treated with either PMA or bryostatin to downregulate PKC, NGF incubation preceded by PMA preincubation still led to long neurite outgrowth. These results suggest that a PMA or bryostatin incubation followed by NGF activates PKC isoforms delta-, and epsilon-leading to outgrowth of long neurites, and that the PMA signaling is independent of the MAPK pathway.
神经生长因子（NGF）刺激PC12细胞可激活信号通路，从而导致新的蛋白质表达和神经突生长。在野生型PC12细胞中，与佛波酯（PMA）孵育会激活蛋白激酶C（PKC），导致神经突生长所需的许多蛋白质表达，但仅这种PKC的激活不会刺激长神经突的生长。在此，我们在缺乏NGF刺激的长神经突生长的PC12-N09亚系中发现，在NGF孵育之前，用PKC激活剂PMA或苔藓抑素1（苔藓抑素）进行短暂孵育，可刺激长神经突的生长。然而，以相反顺序孵育则无效。用PMA或苔藓抑素短暂孵育后再用NGF诱导丝裂原活化蛋白激酶（MAPK）的酪氨酸磷酸化，其持续时间与仅用NGF诱导的相同。因此，PMA预孵育并未增加NGF对MAPK的激活长度。用PMA或苔藓抑素孵育24小时后，PKC亚型下调，但PKCδ和ε亚型仍然存在。在这些用PMA或苔藓抑素长期处理以下调PKC的细胞中，PMA预孵育后再进行NGF孵育仍会导致长神经突长出。这些结果表明，PMA或苔藓抑素孵育后再用NGF激活PKCδ和ε亚型，导致长神经突长出，并表明PMA信号传导独立于MAPK途径。
