Aranovich Alexander, Hua Rong, Rutenberg Andrew D, Kim Peter K
Program in Cell Biology, Hospital for Sick Children, Toronto, ON M5G 0A4, Canada.
Program in Cell Biology, Hospital for Sick Children, Toronto, ON M5G 0A4, Canada Department of Biochemistry, University of Toronto, Toronto, ON M5S 1A8, Canada.
J Cell Sci. 2014 Sep 1;127(Pt 17):3675-86. doi: 10.1242/jcs.146282. Epub 2014 Jul 7.
The endoplasmic reticulum (ER) is required for the de novo biogenesis of peroxisomes in mammalian cells. However, its role in peroxisome maintenance is unclear. To explore ER involvement in the maintenance of peroxisomes, we redirect a peroxisomal membrane protein (PMP), PEX3, to directly target to the ER using the N-terminal ER signal sequence from preprolactin. Using biochemical techniques and fluorescent imaging, we find that ER-targeting PEX3 (ssPEX3) is continuously imported into pre-existing peroxisomes. This suggests that the ER constitutively provides membrane proteins and associated lipids to pre-existing peroxisomes. Using quantitative time-lapse live-cell fluorescence microscopy applied to cells that were either depleted of or exogenously expressing PEX16, we find that PEX16 mediates the peroxisomal trafficking of two distinct peroxisomal membrane proteins, PEX3 and PMP34, via the ER. These results not only provide insight into peroxisome maintenance and PMP trafficking in mammalian cells but also highlight important similarities and differences in the mechanisms of PMP import between the mammalian and yeast systems.
内质网（ER）是哺乳动物细胞中过氧化物酶体从头生物合成所必需的。然而，其在过氧化物酶体维持中的作用尚不清楚。为了探究内质网在过氧化物酶体维持中的作用，我们使用来自前催乳素的N端内质网信号序列，将一种过氧化物酶体膜蛋白（PMP），即PEX3，重定向以直接靶向内质网。通过生化技术和荧光成像，我们发现靶向内质网的PEX3（ssPEX3）持续导入预先存在的过氧化物酶体。这表明内质网持续为预先存在的过氧化物酶体提供膜蛋白和相关脂质。通过对耗尽或外源表达PEX16的细胞应用定量延时活细胞荧光显微镜，我们发现PEX16通过内质网介导两种不同的过氧化物酶体膜蛋白PEX3和PMP34的过氧化物酶体运输。这些结果不仅为哺乳动物细胞中的过氧化物酶体维持和PMP运输提供了见解，也突出了哺乳动物和酵母系统中PMP导入机制的重要异同。
