Shimozawa N, Zhang Z, Imamura A, Suzuki Y, Fujiki Y, Tsukamoto T, Osumi T, Aubourg P, Wanders R J, Kondo N
Department of Pediatrics, Gifu University School of Medicine, Gifu, 500-8076, Japan.
Biochem Biophys Res Commun. 2000 Feb 5;268(1):31-5. doi: 10.1006/bbrc.1999.2082.
Patients with peroxisome biogenesis disorders (PBD) can be identified by detection of peroxisomes in their fibroblasts, by means of immunocytochemical staining using an anti-catalase antibody. We report here data on three PBD patients with newly identified mutations (del550C and del642G) in the PEX2 gene which encodes a 35-kDa peroxisomal membrane protein containing two membrane-spanning and a C-terminal cysteine-rich region. Some of the fibroblasts from the patient with the del642G mutation contained numerous catalase-containing particles, whereas no fibroblasts containing such particles were found in the patient with the del550C mutation. We confirmed that the del642G mutation caused a partial defect in peroxisome synthesis and import by expression of the mutated PEX2 into PEX2-defective CHO mutant cells. We propose that the two putative membrane-spanning segments in Pex2p are important domains for peroxisome assembly and import and that a defect in one of these domains severely affects PBD patients. Furthermore, a defect in the C-terminal portion of Pex2p exposed to the cytosol containing a RING finger motif caused the mild phenotype, residual enzyme activities, and mosaic detectable peroxisomes in fibroblasts from the patient.
过氧化物酶体生物发生障碍（PBD）患者可通过使用抗过氧化氢酶抗体进行免疫细胞化学染色，检测其成纤维细胞中的过氧化物酶体来识别。我们在此报告三例PBD患者的数据，这些患者在编码一种35 kDa过氧化物酶体膜蛋白的PEX2基因中发现了新的突变（del550C和del642G），该蛋白包含两个跨膜区域和一个富含半胱氨酸的C末端区域。来自del642G突变患者的一些成纤维细胞含有大量含过氧化氢酶的颗粒，而在del550C突变患者中未发现含有此类颗粒的成纤维细胞。我们通过将突变的PEX2表达到PEX2缺陷的CHO突变细胞中，证实del642G突变导致过氧化物酶体合成和导入存在部分缺陷。我们提出，Pex2p中的两个假定跨膜片段是过氧化物酶体组装和导入的重要结构域，其中一个结构域的缺陷会严重影响PBD患者。此外，暴露于含有环指基序的细胞质中的Pex2p C末端部分的缺陷导致了患者成纤维细胞中的轻度表型、残余酶活性和可检测的过氧化物酶体镶嵌现象。
