Zhu Yuan, Yang Guo-Yuan, Ahlemeyer Barbara, Pang Li, Che Xiao-Ming, Culmsee Carsten, Klumpp Susanne, Krieglstein Josef
Institut für Pharmakologie und Toxikologie and Pharmazeutische Chemie, Philipps-Universität, D-35032 Marburg, Germany.
J Neurosci. 2002 May 15;22(10):3898-909. doi: 10.1523/JNEUROSCI.22-10-03898.2002.
Despite the characterization of neuroprotection by transforming growth factor-beta1 (TGF-beta1), the signaling pathway mediating its protective effect is unclear. Bad is a proapoptotic member of the Bcl-2 family and is inactivated on phosphorylation via mitogen-activated protein kinase (MAPK). This study attempted to address whether MAPK signaling and Bad phosphorylation were influenced by TGF-beta1 and, furthermore, whether these two events were involved in the antiapoptotic effect of TGF-beta1. We found a gradual activation of extracellular signal-regulated kinase 1/2 (Erk1/2) and MAPK-activated protein kinase-1 (also called Rsk1) and a concomitant increase in Bad phosphorylation at Ser(112) in mouse brains after adenovirus-mediated TGF-beta1 transduction under nonischemic and ischemic conditions induced by transient middle cerebral artery occlusion. Consistent with these effects, the ischemia-induced increase in Bad protein level and caspase-3 activation were suppressed in TGF-beta1-transduced brain. Consequently, DNA fragmentation, ischemic lesions, and neurological deficiency were significantly reduced. In cultured rat hippocampal cells, TGF-beta1 inhibited the increase in Bad expression caused by staurosporine. TGF-beta1 concentration- and time-dependently activated Erk1/2 and Rsk1 accompanied by an increase in Bad phosphorylation. These effects were blocked by U0126, a mitogen-activated protein kinase/Erk kinase 1/2 inhibitor, suggesting an association between Bad phosphorylation and MAPK activation. Notably, U0126 and a Rsk1 inhibitor (Ro318220) abolished the neuroprotective activity of TGF-beta1 in staurosporine-induced apoptosis, indicating that activation of MAPK is necessary for the antiapoptotic effect of TGF-beta1 in cultured hippocampal cells. Together, we demonstrate that TGF-beta1 suppresses Bad expression under lesion conditions, increases Bad phosphorylation, and activates the MAPK/Erk pathway, which may contribute to its neuroprotective activity.
尽管已经对转化生长因子β1（TGF-β1）的神经保护作用进行了表征，但其介导保护作用的信号通路尚不清楚。Bad是Bcl-2家族的促凋亡成员，通过丝裂原活化蛋白激酶（MAPK）磷酸化而失活。本研究试图探讨MAPK信号传导和Bad磷酸化是否受TGF-β1影响，此外，这两个事件是否参与TGF-β1的抗凋亡作用。我们发现，在短暂大脑中动脉闭塞诱导的非缺血和缺血条件下，腺病毒介导的TGF-β1转导后，小鼠脑中细胞外信号调节激酶1/2（Erk1/2）和MAPK活化蛋白激酶-1（也称为Rsk1）逐渐激活，同时Ser(112)位点的Bad磷酸化增加。与这些作用一致，TGF-β1转导的脑内缺血诱导的Bad蛋白水平升高和半胱天冬酶-3激活受到抑制。因此，DNA片段化、缺血性损伤和神经功能缺损明显减少。在培养的大鼠海马细胞中，TGF-β1抑制了星形孢菌素引起的Bad表达增加。TGF-β1浓度和时间依赖性地激活Erk1/2和Rsk1，同时Bad磷酸化增加。这些作用被丝裂原活化蛋白激酶/Erk激酶1/2抑制剂U0126阻断，提示Bad磷酸化与MAPK激活之间存在关联。值得注意的是，U0126和Rsk1抑制剂（Ro318220）消除了TGF-β1在星形孢菌素诱导的凋亡中的神经保护活性，表明MAPK激活对于TGF-β1在培养海马细胞中的抗凋亡作用是必需的。总之，我们证明TGF-β1在损伤条件下抑制Bad表达，增加Bad磷酸化，并激活MAPK/Erk通路，这可能有助于其神经保护活性。
