Research Institute for Cell Engineering, National Institute of Advanced Industrial Science and Technology, Ikeda 563-8577, Japan.
Neurosci Lett. 2010 Apr 12;473(3):229-32. doi: 10.1016/j.neulet.2010.02.055. Epub 2010 Feb 26.
Recent studies have focused on a distinctive contrast between bioactivities of precursor brain-derived neurotrophic factor (proBDNF) and mature BDNF (matBDNF). In this study, using a proteolytic cleavage-resistant proBDNF mutant (CR-proBDNF), signaling mechanisms underlying the proapoptotic effect of proBDNF and antiapoptotic effect of matBDNF on the low potassium (LK)-inducing cell death of cultured cerebellar granule neurons (CGNs) were analyzed. A time course study demonstrated that unlike matBDNF, CR-proBDNF failed to induce TrkB phosphorylation for up to 360 min. CR-proBDNF did not activate ERK-1, ERK-2 and Akt, which are involved in TrkB-induced cell survival signaling, while matBDNF activated these kinases. On the other hand treatment of CGNs with CR-proBDNF led to a rapid activation of Rac-GTPase and phosphorylation of JNK which are involved in p75(NTR)-induced apoptosis. In addition, a JNK-specific inhibitor, SP600125, inhibited the CR-proBDNF-induced apoptosis but did not affect the antiapoptotic effect of matBDNF. CR-proBDNF treatment led to an earlier appearance of active caspase-3. In contrast, matBDNF dramatically postponed the appearance of active caspase-3. Not like other signaling molecules, activation of caspase-3 was conversely regulated by both CR-proBDNF and matBDNF. These results thus suggest that in CGNs proBDNF elicits apoptosis via activation of p75(NTR), Rac-GTPase, JNK, and caspase-3, while matBDNF signals cell survival via activation of TrkB, ERKs and Akt, and deactivation of caspase-3.
最近的研究集中在前脑源性神经营养因子（proBDNF）和成熟 BDNF（matBDNF）的生物活性之间的显著差异上。在这项研究中，使用一种蛋白水解不易切割的 proBDNF 突变体（CR-proBDNF），分析了 proBDNF 的促凋亡作用和 matBDNF 对低钾（LK）诱导的培养小脑颗粒神经元（CGN）死亡的抗凋亡作用的信号机制。时程研究表明，与 matBDNF 不同，CR-proBDNF 未能在长达 360 分钟的时间内诱导 TrkB 磷酸化。CR-proBDNF 不会激活 ERK-1、ERK-2 和 Akt，这些激酶参与 TrkB 诱导的细胞存活信号转导，而 matBDNF 激活了这些激酶。另一方面，用 CR-proBDNF 处理 CGN 会导致 Rac-GTPase 的快速激活和 JNK 的磷酸化，这些激酶参与 p75（NTR）诱导的凋亡。此外，一种 JNK 特异性抑制剂 SP600125 抑制了 CR-proBDNF 诱导的凋亡，但不影响 matBDNF 的抗凋亡作用。CR-proBDNF 处理导致活性 caspase-3 的早期出现。相比之下，matBDNF 极大地推迟了活性 caspase-3 的出现。与其他信号分子不同，caspase-3 的激活受 CR-proBDNF 和 matBDNF 的调节。这些结果表明，在 CGN 中，proBDNF 通过激活 p75（NTR）、Rac-GTPase、JNK 和 caspase-3 引发凋亡，而 matBDNF 通过激活 TrkB、ERK 和 Akt 以及失活 caspase-3 来发出细胞存活信号。
