McLoughlin D M, Standen C L, Lau K F, Ackerley S, Bartnikas T P, Gitlin J D, Miller C C
Department of Neuroscience, Section of Old Age Psychiatry, Institute of Psychiatry, Denmark Hill, London SE5 8AF, United Kingdom.
J Biol Chem. 2001 Mar 23;276(12):9303-7. doi: 10.1074/jbc.M010023200. Epub 2000 Dec 13.
The neuronal adaptor protein X11alpha participates in the formation of multiprotein complexes and intracellular trafficking. It contains a series of discrete protein-protein interaction domains including two contiguous C-terminal PDZ domains. We used the yeast two-hybrid system to screen for proteins that interact with the PDZ domains of human X11alpha, and we isolated a clone encoding domains II and III of the copper chaperone for Cu,Zn-superoxide dismutase-1 (CCS). The X11alpha/CCS interaction was confirmed in coimmunoprecipitation studies plus glutathione S-transferase fusion protein pull-down assays and was shown to be mediated via PDZ2 of X11alpha and a sequence within the carboxyl terminus of domain III of CCS. CCS delivers the copper cofactor to the antioxidant superoxide dismutase-1 (SOD1) enzyme and is required for its activity. Overexpression of X11alpha inhibited SOD1 activity in transfected Chinese hamster ovary cells which suggests that X11alpha binding to CCS is inhibitory to SOD1 activation. X11alpha also interacts with another copper-binding protein found in neurons, the Alzheimer's disease amyloid precursor protein. Thus, X11alpha may participate in copper homeostasis within neurons.
神经元衔接蛋白X11α参与多蛋白复合物的形成和细胞内运输。它包含一系列离散的蛋白质-蛋白质相互作用结构域，包括两个相邻的C末端PDZ结构域。我们利用酵母双杂交系统筛选与人类X11α的PDZ结构域相互作用的蛋白质，并分离出一个编码铜伴侣蛋白（负责铜锌超氧化物歧化酶-1（CCS））结构域II和III的克隆。在免疫共沉淀研究以及谷胱甘肽S-转移酶融合蛋白下拉试验中证实了X11α/CCS的相互作用，并且表明这种相互作用是通过X11α的PDZ2和CCS结构域III羧基末端的一个序列介导的。CCS将铜辅因子传递给抗氧化超氧化物歧化酶-1（SOD1）酶，并且是其活性所必需的。X11α的过表达抑制了转染的中国仓鼠卵巢细胞中的SOD1活性，这表明X11α与CCS的结合对SOD1的激活具有抑制作用。X11α还与神经元中发现的另一种铜结合蛋白——阿尔茨海默病淀粉样前体蛋白相互作用。因此，X11α可能参与神经元内的铜稳态。
