Escobar Valerie Drews, Kuo Yien-Ming, Orrison Bonnie M, Giasson Benoit I, Nussbaum Robert L
Department of Medicine, University of California San Francisco, San Francisco, CA 94143, USA; Institute for Human Genetics, University of California San Francisco, San Francisco, CA 94143, USA.
Genetic Disease Research Branch, NHGRI, National Institutes of Health, Bethesda, MD 20892, USA.
Neurosci Lett. 2014 Mar 20;563:96-100. doi: 10.1016/j.neulet.2014.01.033. Epub 2014 Jan 30.
Aggregated α-synuclein is a predominant constituent of Lewy bodies, the intracellular protein aggregates seen in Parkinson's disease. While most α-synuclein in the nervous system is unphosphorylated, the majority of α-synuclein in Lewy bodies is phosphorylated at serine 129 (S129). We developed transgenic mice expressing human SNCA with either a phosphomimic (S129D) or a non-phosphorylatable (S129A) mutation, on a mouse Snca knockout background. Transgenic lines with each mutation expressing the human α-synuclein protein at levels ranging from 0.3 to 1.9 fold of endogenous mouse protein were chosen to avoid toxic overexpression effects. We previously demonstrated an altered distribution of presynaptic vesicles in Snca knockout mice, as well as enhanced interaction between presynaptic cytoskeletal proteins and α-synuclein when phosphorylated at S129 or carrying an S129D mutation. We therefore examined α-synuclein's synaptic localization and the distribution of presynaptic vesicles in these mutants. In addition, we evaluated the transgenic lines for reduced colonic motility, an early marker of α-synuclein pathology, and α-synuclein aggregates. No abnormalities were detected in mice expressing either phosphorylation mutant protein as their only α-synuclein protein. These results suggest the S129A and S129D mutations have no obvious effect on α-synuclein function.
聚集的α-突触核蛋白是路易小体的主要成分，路易小体是帕金森病中出现的细胞内蛋白质聚集体。虽然神经系统中的大多数α-突触核蛋白未被磷酸化，但路易小体中的大多数α-突触核蛋白在丝氨酸129（S129）处被磷酸化。我们在小鼠Snca基因敲除背景下，培育出了表达具有磷酸化模拟（S129D）或不可磷酸化（S129A）突变的人类SNCA的转基因小鼠。选择每个突变的转基因品系，使其表达的人类α-突触核蛋白水平为内源性小鼠蛋白的0.3至1.9倍，以避免毒性过表达效应。我们之前证明了Snca基因敲除小鼠中突触前囊泡的分布改变，以及当在S129处磷酸化或携带S129D突变时，突触前细胞骨架蛋白与α-突触核蛋白之间的相互作用增强。因此，我们研究了这些突变体中α-突触核蛋白的突触定位和突触前囊泡的分布。此外，我们评估了转基因品系的结肠运动性降低情况，这是α-突触核蛋白病理学的早期标志物，以及α-突触核蛋白聚集体。在仅表达磷酸化突变蛋白作为其唯一α-突触核蛋白的小鼠中未检测到异常。这些结果表明，S129A和S129D突变对α-突触核蛋白功能没有明显影响。
