Brain-specific BNIP-2-homology protein Caytaxin relocalises glutaminase to neurite terminals and reduces glutamate levels
Brain-specific BNIP-2-homology protein Caytaxin relocalises glutaminase to neurite terminals and reduces glutamate levels
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DOI：
10.1242/jcs.03061
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发表时间：
2006-08-15
影响因子：
4
通讯作者：
Low, Boon Chuan
中科院分区：
文献类型：
--
作者：
Buschdorf, Jan Paul;Chew, Li Li;Low, Boon Chuan
人类开曼共济失调和小鼠或大鼠肌张力障碍与编码BNIP-H或Cayaxin的基因ATCAY(Atcay)突变有关，Cayaxin是BNIP-2家族的大脑特异性成员。为了探讨其在神经元功能中的可能作用(S)，我们利用蛋白质沉淀和基质辅助激光解吸/电离质谱仪鉴定了肾型谷氨酰胺酶(KGA)为BNIP-H的一个新的合作伙伴。KGA将谷氨酰胺转化为谷氨酸，谷氨酸可能是神经递质的重要来源。与特异性BNIP-H抗体的免疫共沉淀证实，内源性BNIP-H和KGA在脑内形成一种生理复合体，而结合研究表明它们直接相互作用。免疫组织化学和原位杂交显示BNIP-H在海马区和小脑中高表达，与先前报道的KGA的表达模式广泛重叠。值得注意的是，BNIP-H在胚胎癌细胞系P19的分化神经元中被激活，而其在大鼠嗜铬细胞瘤PC12细胞中的过表达使KGA从线粒体重新定位到轴突终末。它还通过抑制KGA酶的活性来降低稳态谷氨酸水平。这些结果有力地表明，BNIP-H通过与KGA结合，在神经传递过程中调节突触谷氨酸的合成。因此，BNIP-H功能的丧失可能导致谷氨酸兴奋毒性或/和谷氨酸能激活，导致共济失调、肌张力障碍或其他神经疾病。
Human Cayman ataxia and mouse or rat dystonia are linked to mutations in the genes ATCAY (Atcay) that encode BNIP-H or Caytaxin, a brain-specific member of the BNIP-2 family. To explore its possible role(s) in neuronal function, we used protein precipitation and matrix-assisted laser desorption/ionisation mass spectrometry and identified kidney-type glutaminase (KGA) as a novel partner of BNIP-H. KGA converts glutamine to glutamate, which could serve as an important source of neurotransmitter. Co-immunoprecipitation with specific BNIP-H antibody confirmed that endogenous BNIP-H and KGA form a physiological complex in the brain, whereas binding studies showed that they interact with each other directly. Immunohistochemistry and in situ hybridisation revealed high BNIP-H expression in hippocampus and cerebellum, broadly overlapping with the expression pattern previously reported for KGA. Significantly, BNIP-H expression was activated in differentiating neurons of the embryonic carcinoma cell line P19 whereas its overexpression in rat pheochromocytoma PC12 cells relocalised KGA from the mitochondria to neurite terminals. It also reduced the steady-state levels of glutamate by inhibiting KGA enzyme activity. These results strongly suggest that through binding to KGA, BNIP-H could regulate glutamate synthesis at synapses during neurotransmission. Thus, loss of BNIP-H function could render glutamate excitotoxicity or/and deregulated glutamatergic activation, leading to ataxia, dystonia or other neurological disorders.