An isoform of Pex5p, the human PTS1 receptor, is required for the import of PTS2 proteins into peroxisomes
An isoform of Pex5p, the human PTS1 receptor, is required for the import of PTS2 proteins into peroxisomes
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DOI：
10.1093/hmg/7.8.1195
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发表时间：
1998-08-01
影响因子：
3.5
通讯作者：
Valle, D
中科院分区：
文献类型：
--
作者：
Braverman, N;Dodt, G;Valle, D
过氧化物酶体靶向信号(PTS)1受体基因PEX5的突变是导致过氧化物酶体生物发生障碍(PBD)的互补组(CG)2的原因。在本报告的两例CG中，来自PBD018的细胞(错义突变N489K纯合)在将PTS1蛋白导入过氧酶体方面存在缺陷，正如预期的那样。然而，来自PBD005的细胞(无义突变R390ter纯合)在PTS1和PTS2蛋白的导入方面都存在缺陷，这表明PTS1受体也介导了PTS2靶向蛋白的导入。为了研究这种可能性，我们对PEX5的表达进行了研究，发现它经历了选择性剪接，产生了两个转录本，一个包含(PEX5L)和一个缺失(PEX5S)111个核苷酸的内部外显子。与PBD018相比，PBD005的成纤维细胞PEX5的转录本和蛋白水平大大降低，转染PEX5S的PBD005细胞恢复了PTS1而不是PTS2的导入；转染PXR5L的cDNA恢复了PTS1和PTS2的蛋白导入。此外，用含有患者突变的PEX5L cDNA(位于额外外显子下游)转染PBD005细胞可以恢复PTS2，但不能恢复PTS1的导入。综上所述，这些数据为CG2患者不同的蛋白导入缺陷提供了解释，并表明Pex5蛋白的SONG异构体是pts2蛋白过氧体导入所必需的。
Mutations in the peroxisome targeting signal (PTS) 1 receptor gene, PEX5, are responsible for complementation group (CG) 2 of the peroxisome biogenesis disorders (PBD), Of the two reported patients in this CG, cells from PBD018 (homozygous for the missense mutation N489K) are defective in the import of PTS1 proteins into peroxisomes, as expected. However, cells from PBD005 (homozygous for the nonsense mutation R390ter) are defective in the import of both PTS1 and PTS2 proteins, suggesting that the PTS1 receptor also mediates PTS2-targeted protein import. To investigate this possibility, we characterized PEX5 expression and found that it undergoes alternative splicing, producing two transcripts, one containing (PEX5L) and one lacking (PEX5S) a 111 bp internal exon, Fibroblasts from PBD005 have greatly reduced levels of PEX5 transcript and protein as compared with PBD018, Transfection of PBD005 cells with PEX5S cDNA restores PTS1 but not PTS2 import; transfection with PXR5L cDNA restores both PTS1 and PTS2 protein import. Furthermore, transfection of PBD005 cells with PEX5L cDNAs containing the patient mutations (which are located downstream of the additional exon) restores PTS2 but not PTS1 import. Taken together, these data provide an explanation for the different protein import defects in CG2 patients and show that the song isoform of the Pex5 protein is required for peroxisomal import of PTS2 proteins.