alpha-Synuclein Delays Endoplasmic Reticulum (ER)-to-Golgi Transport in Mammalian Cells by Antagonizing ER/Golgi SNAREs

作者：Thayanidhi Nandhakumar; Helm Jared R; Nycz Deborah C; Bentley Marvin; Liang Yingjian; Hay Jesse C^*

来源：Molecular Biology of the Cell, 2010, 21(11): 1850-1863.

DOI：10.1091/mbc.E09-09-0801

Toxicity of human alpha-synuclein when expressed in simple organisms can be suppressed by overexpression of endoplasmic reticulum (ER)-to-Golgi transport machinery, suggesting that inhibition of constitutive secretion represents a fundamental cause of the toxicity. Whether similar inhibition in mammals represents a cause of familial Parkinson's disease has not been established. We tested elements of this hypothesis by expressing human alpha-synuclein in mammalian kidney and neuroendocrine cells and assessing ER-to-Golgi transport. Overexpression of wild type or the familial disease-associated A53T mutant alpha-synuclein delayed transport by up to 50%; however, A53T inhibited more potently. The secretory delay occurred at low expression levels and was not accompanied by insoluble alpha-synuclein aggregates or mistargeting of transport machinery, suggesting a direct action of soluble alpha-synuclein on trafficking proteins. Co-overexpression of ER/Golgi arginine soluble N-ethylmaleimide-sensitive factor attachment protein receptors (R-SNAREs) specifically rescued transport, indicating that alpha-synuclein antagonizes SNARE function. Ykt6 reversed alpha-synuclein inhibition much more effectively than sec22b, suggesting a possible neuroprotective role for the enigmatic high expression of ykt6 in neurons. In in vitro reconstitutions, purified alpha-synuclein A53T protein specifically inhibited COPII vesicle docking and fusion at a pre-Golgi step. Finally, soluble alpha-synuclein A53T directly bound ER/Golgi SNAREs and inhibited SNARE complex assembly, providing a potential mechanism for toxic effects in the early secretory pathway.

• 出版日期2010-6-1