Molecular Anatomy of Peroxisome Biogenesis and Human Disorders

过氧体蛋白，包括膜蛋白，由核基因编码，并在胞质中的游离多聚核糖体上翻译。人类过氧化酶体的功能后果以致命的遗传性过氧化酶体生物发生障碍(PBD)为突出表现，包括Zellweger综合征，所有这些都与过氧酶体组装失败有关。动物细胞突变体的成功分离促使我们寻找对过氧化酶体组装至关重要的基因。我们早先通过对CHO细胞突变体的功能表型互补分析，克隆了包括PEX1、PEX2(原PAF-1)、PEX3、PEX5、PEX6、PEX12、PEX13、PEX14和PEX19在内的9个Peroxin基因，通过酵母基因的表达序列标签搜索，克隆了PEX10和PEX16。在这个助学金的支持下，我们终于成功地为互补第8组(CG8，日本的CG-A)的CHO细胞突变株ZP167克隆了一个互补的cDNAPEX26。Pex26p是一种II型过氧酶体膜蛋白，它将Pexlp-Pex6p复合体招募到过氧酶体中。我们还证明了PEX26确实与CG8的PBD有关。通过克隆PEX26基因，完成了寻找所有PBD致病基因的任务。同时，我们最近利用CHO细胞突变体pex2、pex12、pex13和pex14，证明了携带货物的移动穿梭过氧化物酶体靶向信号1(PTS1)受体Pex5p与假定的进口机械中的初始位置Pexl4p对接，随后转移到其他组分，如Pex13p、Pex2p、Pex10p和Pex12p。此外，在过氧化体膜组装方面，我们证明了Pex19p作为膜蛋白的伴侣在细胞质中发挥作用，并通过与Pex3p对接将它们转移到过氧化体膜上。我们的最新发现包括对过氧化物酶体形态发生的调控。我们发现，Pex11p、Fis1和DLP1以协同的方式调节过氧化体的形态发生。

Peroxisomal proteins, including membrane proteins, are encoded by nuclear genes and translated on free polyribosomes in the cytosol. The functional consequence of human peroxisomes is highlighted by fatal genetic peroxisome biogenesis disorders (PBD), including Zellweger syndrome, all of which are linked to a failure of peroxisome assembly. The successful isolation of animal cell mutants prompted us to search for the genes essential for peroxisome assembly. We earlier cloned nine peroxin cDNAs, including PEX1,PEX2 (formerly PAF-1), PEX3,PEX5,PEX6,PEX12,PEX13,PEX14,and PEX19,by functional phenotype- complementation assay on CHO cell mutants; PEX10 and PEX16 by the expressed sequence tag search using yeast genes. We and other groups showed these PEXs to be responsible for human PBD.During the investigation supported by this Grant-in-Aid, we finally succeeded in cloning of a complementing cDNA, PEX26, for a CHO cell mutant ZP167 of the complementation group 8 (CG8,CG-A in Japan). Pex26p, a type-II peroxisomal membrane protein, recruits Pexlp-Pex6p complexes to peroxisomes. We also showed PEX26 is indeed responsible for PBD of CG8. By cloning of PEX26,the mission of search for pathogenic genes for all PBDs has been accomplished. Meanwhile, we recently demonstrated that a mobile shuttling peroxisome targeting signal 1(PTS1)-receptor, Pex5p, carrying the cargos docks with the initial site Pexl4p in a putative import machinery, subsequently translocating to other components such as Pex13p, Pex2p, Pex10p, and Pex12p, using CHO cell mutants, pex2, pex12, pex13, and pex14. Moreover, with regard to peroxisome membrane assembly, we showed that Pex19p functions in the cytosol as a chaperone for membrane proteins and translocates them to peroxisome membrane by docking to Pex3p. Our most recent findings include the regulation of peroxisome morphogenesis. We found that peroxisome morphogenesis is regulated by Pex11p, Fis1, ad DLP1 in a concerted manner.