Molecular Cell Biology, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, 9747AG Groningen, the Netherlands.
Molecular Cell Biology, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, 9747AG Groningen, the Netherlands.
J Mol Biol. 2018 May 25;430(11):1545-1558. doi: 10.1016/j.jmb.2018.03.033. Epub 2018 Apr 22.
The import of matrix proteins into peroxisomes in yeast requires the action of the ubiquitin-conjugating enzyme Pex4p and a complex consisting of the ubiquitin E3 ligases Pex2p, Pex10p and Pex12p. Together, this peroxisomal ubiquitination machinery is thought to ubiquitinate the cycling receptor protein Pex5p and members of the Pex20p family of co-receptors, a modification that is required for receptor recycling. However, recent reports have demonstrated that this machinery plays a role in additional peroxisome-associated processes. Hence, our understanding of the function of these proteins in peroxisome biology is still incomplete. Here, we identify a role for the peroxisomal ubiquitination machinery in the degradation of the peroxisomal membrane protein Pex13p. Our data demonstrate that Pex13p levels build up in cells lacking members of this machinery and also establish that Pex13p undergoes rapid degradation in wild-type cells. Furthermore, we show that Pex13p is ubiquitinated in wild-type cells and also establish that Pex13p ubiquitination is reduced in cells lacking a functional peroxisomal E3 ligase complex. Finally, deletion of PEX2 causes Pex13p to build up at the peroxisomal membrane. Taken together, our data provide further evidence that the role of the peroxisomal ubiquitination machinery in peroxisome biology goes much deeper than receptor recycling alone.
酵母中基质蛋白向过氧化物酶体的输入需要泛素连接酶 Pex4p 的作用以及由泛素 E3 连接酶 Pex2p、Pex10p 和 Pex12p 组成的复合物的作用。这个过氧化物酶体泛素化机制被认为可以泛素化循环受体蛋白 Pex5p 和 Pex20p 家族的共同受体成员，这种修饰是受体再循环所必需的。然而，最近的报告表明，该机制在其他过氧化物酶体相关过程中发挥作用。因此，我们对这些蛋白质在过氧化物酶体生物学中的功能的理解仍然不完整。在这里，我们确定了过氧化物酶体泛素化机制在过氧化物酶体膜蛋白 Pex13p 降解中的作用。我们的数据表明，在缺乏这些机制成员的细胞中 Pex13p 水平增加，并且还确定 Pex13p 在野生型细胞中迅速降解。此外，我们表明 Pex13p 在野生型细胞中被泛素化，并确定在缺乏功能性过氧化物酶体 E3 连接酶复合物的细胞中 Pex13p 的泛素化减少。最后，pex2 的缺失导致 Pex13p 在过氧化物酶体膜上积累。总之，我们的数据提供了进一步的证据，表明过氧化物酶体泛素化机制在过氧化物酶体生物学中的作用远远超出受体再循环本身。
