Stimulation of the ERK pathway by GTP-loaded Rap1 requires the concomitant activation of ras, protein kinase C, and protein kinase A in neuronal cells
Stimulation of the ERK pathway by GTP-loaded Rap1 requires the concomitant activation of ras, protein kinase C, and protein kinase A in neuronal cells
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DOI：
10.1074/jbc.m204652200
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发表时间：
2003-02-14
影响因子：
4.8
通讯作者：
Journot, L
中科院分区：
文献类型：
--
作者：
Bouschet, T;Perez, V;Journot, L
小GTP酶Ras或Rap 1可能介导某些G蛋白偶联受体对神经细胞ERK活性的刺激作用。因此，我们在这里报道，垂体腺苷酸环化酶激活多肽（PACAP），其G蛋白偶联受体触发神经元分化的PC 1/2细胞系通过ERK 1/2激活，瞬时激活Ras和诱导的Rapl的持续GTP加载。Ras介导PACAP对ERK的峰值刺激，而Rapl是持续激活相所必需的。然而，PACAP诱导的Rap 1的GTP负载不足以解释PACAP对ERK的激活，因为1）PACAP诱导的Rap 1的GTP负载仅依赖于磷脂酶C，而PACAP对ERK的最大刺激还需要蛋白激酶A（PKA）、蛋白激酶C（PKC）和钙依赖性信号传导的活性; Rap 1、Rap 1A-V12和Rap 1B-V12的组成型活性突变体与Ras-V12相比仅最低程度地刺激ERK途径。Rap 1A-V12的作用通过同时激活PKC、cAMP途径和Ras而显著增强，并且这种增强作用被Ras和Raf的显性负突变体阻断。因此，这组数据表明，GPCR引发的GTP负载Rapl不足以有效刺激PC 12细胞中的ERK，并且需要PKA、PKC或Ras的允许共刺激。
The small GTPases Ras or Rap1 were suggested to mediate the stimulatory effect of some G protein-coupled receptors on ERK activity in neuronal cells. Accordingly, we reported here that pituitary adenylate cyclase-activating polypeptide (PACAP), whose G protein-coupled receptor triggers neuronal differentiation of the PC12 cell line via ERK1/2 activation, transiently activated Ras and induced the sustained GTP loading of Rapl. Ras mediated peak stimulation of ERK by PACAP, whereas Rapl was necessary for the sustained activation phase. However, PACAP-induced GTP-loading of Rapl was not sufficient to account for ERK activation by PACAP because 1) PACAP-elicited Rapl GTP-loading depended only on phospholipase C, whereas maximal stimulation of ERK by PACAP also required the activity of protein kinase A (PKA), protein kinase C (PKC), and calcium-dependent signaling;, and 2) constitutively active mutants of Rapl, RaplA-V12, and Rap1B-V12 only minimally stimulated the ERK pathway compared with Ras-V12. The effect of Rap1A-V12 was dramatically potentiated by the concurrent activation of PKC, the cAMP pathway, and Ras, and this potentiation was blocked by dominant-negative mutants of Ras and Raf. Thus, this set of data indicated that GPCR-elicited GTP loading of Rapl was not sufficient to stimulate efficiently ERK in PC12 cells and required the permissive co-stimulation of PKA, PKC, or Ras.