細胞自噬在PC12 細胞處理多巴胺和鋅時所扮演的角色

細胞自噬（autophagy）在細胞中扮演重要的角色，除了負責大量降解胞器和長時間表現的細胞質內蛋白質，也參與細胞發育、分化和存活。細胞自噬常在有壓力時誘發，需要LC3 的參與而形成細胞自噬小體（autophagosome）。先前的研究指出，多巴胺和鋅會造成分泌多巴胺的神經細胞死亡，進而導致帕金森氏症。其神經病理主要特徵為大量的蛋白質累積（Lewy bodies），其中主要為α-synuclein，但不知細胞自噬是否參與這些過程中。因此，為了明瞭細胞自噬在細胞面臨多巴胺和鋅處理時所扮演的角色，將PC12 細胞大量表現GFP-LC3，觀察螢光表現。我們的結果顯示，當細胞處理250 μM 的多巴胺和200 μM 的鋅時，細胞自噬小體的數目會有顯著性的增加。但若是前處理phosphatidylinositol 3-kinase（PI3K）的抑制劑，此增加會被顯著性地抑制。除此之外，處理多巴胺和鋅時，會使得許多細胞進行細胞凋亡（apoptosis），而抑制細胞自噬則會讓更多細胞進行細胞凋亡。除此之外，若是將PC12 細胞同時大量表現Dsred-LC3 和CFP-α-synuclein，再處理多巴胺和鋅時，只會導致細胞自噬小體的數目增加，卻不會造成α-synuclein 累積。這些結果顯示，細胞在面臨過量的多巴胺和鋅時，細胞自噬小體會經由PI3K 調節的途徑增加，而且細胞自噬在此扮演保護的角色。

關鍵字

細胞自噬；多巴胺；鋅；帕金森氏症；細胞凋亡

並列摘要

Autophagy is involved in the degradation of organelles and long-lived proteins, but also plays an important role in cell development, differentiation and survival. Autophagy is mainly induced under stress and causes autophagosome formation. The formation of autophagosome requires the recruitment of LC3; therefore, LC3 could be a marker of autophagosomes. It has been shown that both dopamine and zinc cause dopaminergic neuron death which may be responsible for Parkinson’s disease (PD). The neuropathologic hallmark of PD is the presence of α-synuclein accumulation in the Lewy bodies. However, it is not clear whether autophagy is involved in these processes. To determine the roles of autophagy plays in cells treated with dopamine and zinc, PC12 cells were transfected with GFP-fused LC3 and the aggregations of the fluorescence were used to represent the presence of autophagosomes. Our results showed that the number of autophagosomes in cells pretreated with dopamine (250 μM) or zinc (200 μM) was higher than that of control cells. This increase was inhibited by the pretreatment of LY294002 (5 μM) and wortmannin (5 μM), the inhibitors of phosphatidylinositol 3-kinase. In addition, the occurrence of apoptosis in cells pretreated with dopamine was increased and further, enhanced by LY294002 treatment. When PC12 cells coexpressing Dsred-fused LC3 and CFP-fused α-synuclein, LC3, but not α-synuclein, was aggregated by doapmien and Zn2+ treatment. These results suggested that the formation of autophagosome in PC12 cells treated with dopamine and zinc is mediated by PI3K pathway, and autophagy may play a protective role in PC12 cells.

並列關鍵字

autophagy ； PC12 cell ； dopamine ； Zn2+ ； apoptosis

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細胞自噬在PC12 細胞處理多巴胺和鋅時所扮演的角色

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