Yan Xiao-Xin, Li Tong, Rominger Cynthia M, Prakash Shimoga R, Wong Philip C, Olson Richard E, Zaczek Robert, Li Yu-Wen
Bristol-Myers Squibb Company, Pharmaceutical Research Institute, Neuroscience Drug Discovery, Wallingford, Connecticut 06492, USA.
J Neurosci. 2004 Mar 24;24(12):2942-52. doi: 10.1523/JNEUROSCI.0092-04.2004.
gamma-Secretase is a multimeric complex consisted of presenilins (PSs) and three other proteins. PSs appear to be key contributors for the enzymatic center, the potential target of a number of recently developed gamma-secretase inhibitors. Using radiolabeled and unlabeled inhibitors as ligands, this study was aimed to determine the in situ distribution of gamma-secretase in the brain. Characterization using PS-1 knock-out mouse embryos revealed 50 and 80% reductions of gamma-secretase inhibitor binding density in the heterozygous (PS-1(+/-)) and homozygous (PS-1-/-) embryos, respectively, relative to the wild type (PS-1(+/+)). The pharmacological profile from competition binding assays suggests that the ligands may target at the N- and C-terminal fragments of PS essential for gamma-secretase activity. In the adult rat brain, the binding sites existed mostly in the forebrain, the cerebellum, and discrete brainstem areas and were particularly abundant in areas rich in neuronal terminals, e.g., olfactory glomeruli, CA3-hilus area, cerebellar molecular layer, and pars reticulata of the substantia nigra. In the developing rat brain, diffuse and elevated expression of binding sites occurred at the early postnatal stage relative to the adult. The possible association of binding sites with neuronal terminals in the adult brain was further investigated after olfactory deafferentation. A significant decrease with subsequent recovery of binding sites was noted in the olfactory glomeruli after chemical damage of the olfactory epithelium. The findings in this study support a physiological role of PS or gamma-secretase complex in neuronal and synaptic development and plasticity.
γ-分泌酶是一种由早老素（PSs）和其他三种蛋白质组成的多聚体复合物。PSs似乎是酶活性中心的关键组成部分，是许多最近开发的γ-分泌酶抑制剂的潜在靶点。本研究使用放射性标记和未标记的抑制剂作为配体，旨在确定γ-分泌酶在脑中的原位分布。使用PS-1基因敲除小鼠胚胎进行的特性分析显示，相对于野生型（PS-1(+/+)），杂合子（PS-1(+/-)）和纯合子（PS-1-/-）胚胎中γ-分泌酶抑制剂结合密度分别降低了50%和80%。竞争结合试验的药理学特征表明，这些配体可能靶向PS的N端和C端片段，这些片段对γ-分泌酶活性至关重要。在成年大鼠脑中，结合位点主要存在于前脑、小脑和离散的脑干区域，在富含神经末梢的区域特别丰富，例如嗅小球、CA3-海马回区域、小脑分子层和黑质网状部。在发育中的大鼠脑中，相对于成年期，结合位点在出生后早期出现弥漫性和升高的表达。在嗅觉去传入后，进一步研究了成年脑中结合位点与神经末梢的可能关联。在嗅上皮化学损伤后，嗅小球中观察到结合位点显著减少，随后又恢复。本研究的结果支持PS或γ-分泌酶复合物在神经元和突触发育及可塑性中的生理作用。
