Selective autophagy of peroxisomes in methylotrophic yeasts.
Selective autophagy of peroxisomes in methylotrophic yeasts.
复制标题
DOI：
--
复制
发表时间：
1993
影响因子：
6.6
通讯作者：
D. L. Tuttle;A. Lewin;W. Dunn
中科院分区：
文献类型：
--
作者：
D. L. Tuttle;A. Lewin;W. Dunn
甲醇营养型酵母巴斯德毕赤酵母和多形汉逊酵母通过合成过氧化物酶体酶来响应甲醇底物，导致形成大的过氧化物酶体。当碳源从甲醇变为葡萄糖时，我们观察到过氧化物酶体的快速损失。在这项比较研究中，我们利用生物化学和形态学技术来表征这些酵母中过氧化物酶体的损失。我们使用代谢标记和追踪程序来评估这种损失是否是由于抑制合成或增强降解。当在甲醇中生长的培养物达到稳定生长时，醇氧化酶的合成被抑制10倍。然而，在将这些培养物转移到葡萄糖培养基中后，没有观察到合成的进一步减少。在甲醇中保持的稳定期培养物中，两种过氧化物酶体蛋白，醇氧化酶和二羟丙酮合酶，被降解，半衰期超过3小时。然而，在3小时内的葡萄糖阻遏，多达80%的放射性标记的过氧化物酶体蛋白从酵母菌丢失。这种葡萄糖介导的降解事件似乎对过氧化物酶体蛋白具有特异性，因为线粒体蛋白是稳定的。两种酵母的超微结构检查显示，葡萄糖诱导的过氧化物酶体到酵母液泡，推定的网站降解的隔离。这些结果表明，过氧化物酶体损失葡萄糖阻遏过程中是由于选择性，增强降解的整个过氧化物酶体的自噬机制。
The methylotrophic yeasts Pichia pastoris and Hansenula polymorpha respond to a methanol substrate by synthesizing peroxisomal enzymes resulting in the formation of large peroxisomes. When the carbon source was changed from methanol to glucose, we observed a rapid loss of peroxisomes. In this comparative study, we utilized biochemical and morphological techniques to characterize the loss of peroxisomes in these yeasts. We used metabolic labeling and chase procedures to evaluate whether this loss was due to suppressed synthesis or enhanced degradation. The synthesis of alcohol oxidase was depressed 10-fold when cultures grown in methanol attained stationary growth. However, no further reduction of synthesis was observed upon transfer of these cultures to glucose medium. In stationary phase cultures maintained in methanol, two peroxisomal proteins, alcohol oxidase and dihydroxyacetone synthase, were degraded with a half-life of over 3 h. However, within 3 h of glucose repression, as much as 80% of the radiolabeled peroxisomal proteins were lost from both yeasts. This glucose-mediated degradative event appeared to be specific for peroxisomal proteins, since mitochondrial proteins were stable. Ultrastructural examination of both yeasts revealed that glucose induced the sequestration of peroxisomes into the yeast vacuole, the presumed site of degradation. These results suggest that peroxisome loss during glucose repression is due to a selective, enhanced degradation of whole peroxisomes by autophagic mechanisms.