Instituto de Biología y Medicina Experimental-CONICET and Departamento de Química Biológica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires, Argentina.
Br J Pharmacol. 2012 May;166(2):637-49. doi: 10.1111/j.1476-5381.2011.01783.x.
BACKGROUND AND PURPOSE The immunosuppressive macrolide FK506 (tacrolimus) shows neuroregenerative action by a mechanism that appears to involve the Hsp90-binding immunophilin FKBP52. This study analyses some aspects of the early steps of neuronal differentiation and neuroregeneration. EXPERIMENTAL APPROACH Undifferentiated murine neuroblastoma cells and hippocampal neurones isolated from embryonic day-17 rat embryos were induced to differentiate with FK506. Subcellular relocalization of FKBP52, Hsp90 and its co-chaperone p23 was analysed by indirect immunofluorescence confocal microscopy and by Western blots of axonal fractions isolated from cells grown on a porous transwell cell culture chamber. Neuroregeneration was evaluated using a scratch-wound assay. KEY RESULTS In undifferentiated cells, FKBP52, Hsp90 and p23 are located in the cell nucleus, forming an annular structure that disassembles when the differentiation process is triggered by FK506. This was observed in the N2a cell line and in hippocampal neurones. More importantly, the annular structure of chaperones is reassembled after damaging the neurones, whereas FK506 prompts their rapid regeneration, a process linked to the subcellular redistribution of the heterocomplex. CONCLUSIONS AND IMPLICATIONS There is a direct relationship between the disassembly of the chaperone complex and the progression of neuronal differentiation upon stimulation with the immunophilin ligand FK506. Both neuronal differentiation and neuroregeneration appear to be mechanistically linked, so the elucidation of one mechanism may lead to unravel the properties of the other. This study also implies that the discovery of FK506 derivatives, devoid of immunosuppressive action, would be therapeutically significant for neurotrophic use.
免疫抑制剂 FK506（他克莫司）通过一种似乎涉及 HSP90 结合免疫亲和素 FKBP52 的机制表现出神经再生作用。本研究分析了神经元分化和神经再生的早期步骤的一些方面。
用 FK506 诱导未分化的鼠神经母细胞瘤细胞和来自胚胎第 17 天大鼠胚胎的海马神经元分化。通过间接免疫荧光共焦显微镜和从生长在多孔 Transwell 细胞培养室的细胞中分离的轴突级分的 Western blot 分析 FKBP52、Hsp90 及其共伴侣 p23 的亚细胞重定位。使用划痕伤口测定评估神经再生。
在未分化的细胞中，FKBP52、Hsp90 和 p23 位于细胞核中，形成一个环形结构，当分化过程被 FK506 触发时，该结构会解体。这在 N2a 细胞系和海马神经元中都观察到。更重要的是，当神经元受损时，伴侣蛋白的环形结构会重新组装，而 FK506 则促使它们快速再生，这一过程与异质复合物的亚细胞重新分布有关。
FK506 配体刺激下，伴侣复合物的解体与神经元分化的进展之间存在直接关系。神经元分化和神经再生似乎在机制上是相关的，因此阐明一种机制可能会揭示另一种机制的特性。这项研究还表明，发现无免疫抑制作用的 FK506 衍生物在神经营养方面的治疗应用将具有重要意义。
