Ano Yoshitaka, Hattori Takeshi, Kato Nobuo, Sakai Yasuyoshi
Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Japan.
Biosci Biotechnol Biochem. 2005 Aug;69(8):1527-33. doi: 10.1271/bbb.69.1527.
The methylotrophic yeast Pichia pastoris can degrade peroxisomes selectively though two distinct pexophagic pathways, viz., micropexophagy and macropexophagy. These micro- and macropexophagy pathways are induced by adaptation of methanol-grown cells to glucose-containing and ethanol-containing media respectively. However, our understanding of the molecular signal(s) that determine which pathway is activated or repressed in response to environmental changes is limited. In this study, the determinant for these pathways was sought using cells undergoing pexophagy under a variety of conditions. Micropexophagy and macropexophagy were distinguished in living cells by fluorescence microscopy. Our results indicate that glucose and ethanol were not specific inducers of micro- and macropexophagy respectively. Micropexophagy was found to be more sensitive to ATP-depletion than macropexophagy, suggesting that the micropexophagic process requires a higher level of ATP than the macropexophagic process. From these and other results, we postulate that intracellular ATP levels play an important role in determining which pexophagic pathway is activated.
甲基营养型酵母巴斯德毕赤酵母可通过两种不同的过氧化物酶体自噬途径，即微过氧化物酶体自噬和巨过氧化物酶体自噬，选择性地降解过氧化物酶体。这些微过氧化物酶体自噬和巨过氧化物酶体自噬途径分别通过使在甲醇中生长的细胞适应含葡萄糖和含乙醇的培养基来诱导。然而，我们对响应环境变化决定激活或抑制哪种途径的分子信号的理解是有限的。在本研究中，利用在各种条件下经历过氧化物酶体自噬的细胞寻找这些途径的决定因素。通过荧光显微镜在活细胞中区分微过氧化物酶体自噬和巨过氧化物酶体自噬。我们的结果表明，葡萄糖和乙醇分别不是微过氧化物酶体自噬和巨过氧化物酶体自噬的特异性诱导剂。发现微过氧化物酶体自噬比巨过氧化物酶体自噬对ATP消耗更敏感，这表明微过氧化物酶体自噬过程比巨过氧化物酶体自噬过程需要更高水平的ATP。根据这些及其他结果，我们推测细胞内ATP水平在决定激活哪种过氧化物酶体自噬途径中起重要作用。
