Hendry I A, Johanson S O, Heydon K
Division of Neuroscience, John Curtin School of Medical Research, Australian National University, Canberra, Australia.
Brain Res. 1995 Nov 27;700(1-2):157-63. doi: 10.1016/0006-8993(95)00945-m.
Nerve cells are exquisitely sensitive to target tissue derived factors and the discovery that nerve growth factor could be retrogradely transported in axons suggested that the physical translocation of proteins along the axon could be a mechanism to convey this signal. This message is not due to the neurotrophic factor itself but rather due to second messengers generated by interaction with receptors. We have previously demonstrated the retrograde axonal transport of the alpha subunits of two putative second messenger molecules Gi and Gz. We have investigated more thoroughly the transport of the alpha subunit of Gz (Gz alpha) and in order to be more certain that the immunoreactivity seen is due to Gz alpha, we have made antibodies to peptides from both the N- and C-terminal regions of Gz alpha, which recognise the same 41 kDa band on Western blots of brain and sciatic nerve extracts. This band is eliminated when the antibodies are previously incubated with the specific peptide to which they were made. Using these antibodies for immunohistochemical localisation for Gz alpha, we now report that the GTP-binding protein Gz, is not only retrogradely transported in axons but that it translocates to the neuronal nucleus. Furthermore, the levels seen in the nuclear compartment decline after axotomy or ligation of the mice under ether anaesthetic, suggesting it is the retrogradely transported Gz alpha that is accumulating in the nucleus after activation at the nerve terminal.
神经细胞对靶组织衍生因子极为敏感，神经生长因子可在轴突中逆行运输这一发现表明，蛋白质沿轴突的物理转运可能是传递该信号的一种机制。这个信息并非源于神经营养因子本身，而是源于与受体相互作用产生的第二信使。我们之前已经证明了两种假定的第二信使分子Gi和Gz的α亚基的逆行轴突运输。我们更深入地研究了Gz的α亚基（Gzα）的运输，为了更确定所观察到的免疫反应性是由Gzα引起的，我们制备了针对GzαN端和C端区域肽段的抗体，这些抗体在脑和坐骨神经提取物的蛋白质免疫印迹中识别相同的41 kDa条带。当抗体预先与它们所针对的特异性肽段孵育时，该条带消失。利用这些抗体对Gzα进行免疫组织化学定位，我们现在报告GTP结合蛋白Gz不仅在轴突中逆行运输，而且它会转移到神经元细胞核。此外，在轴突切断或对乙醚麻醉下的小鼠进行结扎后，核区中观察到的水平下降，这表明是在神经末梢激活后逆行运输到细胞核中的Gzα在积累。
