过氧化物酶体生物发生研究进展

过氧化物酶体是存在于真核细胞中的一种亚细胞器,主要功能是参与脂肪酸等脂质的代谢过程和氧化应激的调节。近年来研究发现,多种疾病都与过氧化物酶体的生物发生异常有关。过氧化物酶体的生物发生指过氧化物酶体的形成过程,包括从头合成和分裂增殖两条途径。两条途径中,参与过氧化物酶体生物发生的蛋白质,即peroxin(PEX)的基因发生突变,会导致过氧化物酶体生成障碍,引起疾病的发生。因此,就过氧化物酶体生物发生的研究进展进行综述,有助于为相关疾病的诊断和治疗提供参考和依据。     

过氧化物酶体降解与疾病

过氧化物酶体是细胞中一种参与脂肪酸代谢、缩醛磷脂合成和氧化应激等功能的细胞器,其数量会根据细胞和细胞所处微环境的不同而发生变化,这种变化又与过氧化物酶体本身的降解密切相关.虽然一直以来,过氧化物酶体都被线粒体的光芒所掩盖,但是近年来,随着过氧化物酶体研究的逐渐增多,人们对于过氧化物酶体的降解也有了更全面的了解.本文主要...     

酵母过氧化物酶体的形成机制

过氧化物酶体是细胞中一种重要的细胞器.过氧化物酶体在细胞功能的发挥和人体健康方面有着重要作用.目前,以酵母过氧化物酶体为模型,研究过氧化物酶体的形成机制是研究热点.从过氧化物酶体起源、生成方式介绍最新研究进展,总结在酵母细胞中参与过氧化物酶体形成的必需基因(pex),及其编码Peroxin蛋白在过氧化物酶体形成过程中的...     

植物病原真菌过氧化物酶体的发生机制及功能

过氧化物酶体(peroxisome,P)是真核细胞中普遍存在的细胞器,参与多种重要的代谢过程。P的产生、增殖及降解是细胞器发生机理研究的重要部分。到目前已知的P发生相关基因有30多个,但其机制仍不完全清楚。作为一种多细胞真核生物,丝状真菌在P发生机制的研究中有重要价值。近年来,随着基因组序列的应用和真菌生物技术的进展,丝状真菌中P功能及发生机制的研究取得了较大进展。同时,作为丝状真菌真菌中的重要类群,植物病原真菌P在致病过程中的作用也引起关注。本文对P发生机制、在丝状真菌中的研究概况,以及与植物病原真菌致病性的关系进行了综述。     

过氧化物酶体膜对各种光呼吸代谢物的透性和Percoll对其完整性的影响

利用氧极谱法测定依赖乙醇酸和乙醛酸的氧吸收,利用分光光度计测定转氨酶活性的方法,检查了光呼吸碳代谢中各种中间产物对过氧化物酶体膜的透性,结果表明,O2,乙醇酸,乙醛酸,丝氨酸,天冬氨酸,草酰乙酸,α－酮戊二酸能透过过氧体膜,过氧体膜可能有谷氨酸和NADH进入的屏障,过氧体悬浮液Percoll存在,很快使过氧体膜破坏,Percoll也使羟基丙酮酸还原酶和苹果酸脱氢酶的活性很快降低。     

新疆维吾尔族人群过氧化物酶体增殖物激活受体基因相关SNP位点的多态性

对过氧化物酶体增殖物激活受体基因(PPARG)的31个SNP位点进行群体遗传学分析,利用质谱检测技术检测PPARG基因的31个SNPs位点多态性,并根据质谱峰图判读样本目标位点基因型,统计分析31个SNP位点的基因型和等位基因的分布频率,利用x2检验确定筛选的SNP位点是否符合Hardy-Weinberg平衡定律。结果发现31个SNP位点中,23个位点的次等位基因分布频率MAF≥0.05,在新疆维吾尔族人群中具有多态性,其他8个SNP位点的MAF0.05,没显示多态性。基因型和等位基因频率在男女两组间均无统计学差异(P0.05),表明这些位点等位基因分布不存在性别差异。     

植物体中的过氧化物酶体

过氧化物酶体参与了包括氧化氢反应、长链脂肪酸的β-氧化等几乎所有的必需代谢途径。植物过氧化物酶体在植物体抗病和抗衰老过程中发挥作用。介绍了植物过氧化物酶体与亚硫酸盐氧化酶以及植物过氧化物酶体抗衰老、生物发生和动力学等方面的研究进展。     

固定化过氧化物酶丝素膜的制备及其性质

家蚕丝素经高浓度的中性盐氯化钙溶解后,制成了固定化过氧化物酶丝素膜,对这种酶膜的活性和理化特性作了分析,结果表明这种酶膜的活性高,酶促反应温度范围宽,最适pH5.0-7.0,热稳定性也较游离酶好,这与用溴化锂溶解丝素后制成的固定化过氧化物酶膜相仿.因此,用这种方法制成的丝素膜同样是一种良好的固定化酶的生物材料.     

过氧化物酶体膜对各种光呼吸代谢物的透性和Percoll对其完整性的影响

利用氧极谱法测定依赖乙醇酸和乙醛酸的氧吸收,利用分光光度计测定转氨酶活性的方法,检查了光呼吸碳代谢中各种中间产物对过氧化物酶体膜的透性,结果表明,O2,乙醇酸,乙醛酸,丝氨酸,天冬氨酸,草酰乙酸,α－酮戊二酸能透过过氧体膜,过氧体膜可能有谷氨酸和NADH进入的屏障,过氧体悬浮液Percoll存在,很快使过氧体膜破坏,Percoll也使羟基丙酮酸还原酶和苹果酸脱氢酶的活性很快降低。     

过氧化物酶体的生物发生与疾病

过氧化物酶体的膜蛋白和酶分子由核基因编码,在游离的核糖体上合成之后,由定位信号引导靶向运输并组装到过氧化物酶体的。本文就过氧化物酶体膜蛋白信号ｍＰＴＳ、酶分子信号ＰＴＳ１Ｔ ＰＴＳ２、酶分子运进过氧化物酶体的模型以及由于过氧化物酶体生物发生的障碍而引起的疾病加以讨论。     

CRM1-mediated recycling of snurportin 1 to the cytoplasm

Importin beta is a major mediator of import into the cell nucleus. Importin beta binds cargo molecules either directly or via two types of adapter molecules, importin alpha, for import of proteins with a classical nuclear localization signal (NLS), or snurportin 1, for import of m3G-capped U snRNPs. Both adapters have an NH2-terminal importin beta-binding domain for binding to, and import by, importin beta, and both need to be returned to the cytoplasm after having delivered their cargoes to the nucleus. We have shown previously that CAS mediates export of importin alpha. Here we show that snurportin 1 is exported by CRM1, the receptor for leucine-rich nuclear export signals (NESs). However, the interaction of CRM1 with snurportin 1 differs from that with previously characterized NESs. First, CRM1 binds snurportin 1 50-fold stronger than the Rev protein and 5,000-fold stronger than the minimum Rev activation domain. Second, snurportin 1 interacts with CRM1 not through a short peptide but rather via a large domain that allows regulation of affinity. Strikingly, snurportin 1 has a low affinity for CRM1 when bound to its m3G-capped import substrate, and a high affinity when substrate-free. This mechanism appears crucial for productive import cycles as it can ensure that CRM1 only exports snurportin 1 that has already released its import substrate in the nucleus.     

Inhibitors of COPI and COPII do not block PEX3-mediated peroxisome synthesis

In humans, defects in peroxisome biogenesis are the cause of lethal diseases typified by Zellweger syndrome. Here, we show that inactivating mutations in human PEX3 cause Zellweger syndrome, abrogate peroxisome membrane synthesis, and result in reduced abundance of peroxisomal membrane proteins (PMPs) and/or mislocalization of PMPs to the mitochondria. Previous studies have suggested that PEX3 may traffic through the ER en route to the peroxisome, that the COPI inhibitor, brefeldin A, leads to accumulation of PEX3 in the ER, and that PEX3 overexpression alters the morphology of the ER. However, we were unable to detect PEX3 in the ER at early times after expression. Furthermore, we find that inhibition of COPI function by brefeldin A has no effect on trafficking of PEX3 to peroxisomes and does not inhibit PEX3-mediated peroxisome biogenesis. We also find that inhibition of COPII-dependent membrane traffic by a dominant negative SAR1 mutant fails to block PEX3 transport to peroxisomes and PEX3-mediated peroxisome synthesis. Based on these results, we propose that PEX3 targeting to peroxisomes and PEX3-mediated peroxisome membrane synthesis may occur independently of COPI- and COPII-dependent membrane traffic.     

Pex12p of Saccharomyces cerevisiae is a component of a multi-protein complex essential for peroxisomal matrix protein import

We have isolated the Saccharomyces cerevisiae pex12-1 mutant from a screen to identify mutants defective in peroxisome biogenesis. The pex12delta deletion strain fails to import peroxisomal matrix proteins through both the PTS1 and PTS2 pathway. The PEX12 gene was cloned by functional complementation of the pex12-1 mutant strain and encodes a polypeptide of 399 amino acids. ScPex12p is orthologous to Pex12 proteins from other species and like its orthologues, S. cerevisiae Pex12p contains a degenerate RING finger domain of the C3HC4 type in its essential carboxy-terminus. Localization studies demonstrate that Pex12p is an integral peroxisomal membrane protein, with its NH2-terminus facing the peroxisomal lumen and with its COOH-terminus facing the cytosol. Pex12p-deficient cells retain particular structures that contain peroxisomal membrane proteins consistent with the existence of peroxisomal membrane remnants ("ghosts") in pex12A null mutant cells. This finding indicates that pex12delta cells are not impaired in peroxisomal membrane biogenesis. In immunoisolation experiments Pex12p was co-purified with the RING finger protein Pex10p, the PTS1 receptor Pex5p and the docking proteins for the PTS1 and the PTS2 receptor at the peroxisomal membrane, Pex13p and Pex14p. Furthermore, two-hybrid experiments suggest that the two RING finger domains are sufficient for the Pex10p-Pex12p interaction. Our results suggest that Pex12p is a component of the peroxisomal translocation machinery for matrix proteins.     

ER–endosome contact sites: molecular compositions and functions

Recent studies have revealed the existence of numerous contact sites between the endoplasmic reticulum (ER) and endosomes in mammalian cells. Such contacts increase during endosome maturation and play key roles in cholesterol transfer, endosome positioning, receptor dephosphorylation, and endosome fission. At least 7 distinct contact sites between the ER and endosomes have been identified to date, which have diverse molecular compositions. Common to these contact sites is that they impose a close apposition between the ER and endosome membranes, which excludes membrane fusion while allowing the flow of molecular signals between the two membranes, in the form of enzymatic modifications, or ion, lipid, or protein transfer. Thus, ER–endosome contact sites ensure coordination of molecular activities between the two compartments while keeping their general compositions intact. Here, we review the molecular architectures and cellular functions of known ER–endosome contact sites and discuss their implications for human health.     

ER–plasma membrane contact sites contribute to autophagosome biogenesis by regulation of local PI3P synthesis

The double‐membrane‐bound autophagosome is formed by the closure of a structure called the phagophore, origin of which is still unclear. The endoplasmic reticulum (ER) is clearly implicated in autophagosome biogenesis due to the presence of the omegasome subdomain positive for DFCP1, a phosphatidyl‐inositol‐3‐phosphate (PI3P) binding protein. Contribution of other membrane sources, like the plasma membrane (PM), is still difficult to integrate in a global picture. Here we show that ER–plasma membrane contact sites are mobilized for autophagosome biogenesis, by direct implication of the tethering extended synaptotagmins (E‐Syts) proteins. Imaging data revealed that early autophagic markers are recruited to E‐Syt‐containing domains during autophagy and that inhibition of E‐Syts expression leads to a reduction in autophagosome biogenesis. Furthermore, we demonstrate that E‐Syts are essential for autophagy‐associated PI3P synthesis at the cortical ER membrane via the recruitment of VMP1, the stabilizing ER partner of the PI3KC3 complex. These results highlight the contribution of ER–plasma membrane tethers to autophagosome biogenesis regulation and support the importance of membrane contact sites in autophagy.