Monastyrska Iryna, van der Heide Meis, Krikken Arjen M, Kiel Jan A K W, van der Klei Ida J, Veenhuis Marten
Eukaryotic Microbiology, Groningen Biomolecular Sciences and Biotechnology Institute (GBB), University of Groningen, PO Box 14, 9750 AA Haren, the Netherlands.
Traffic. 2005 Jan;6(1):66-74. doi: 10.1111/j.1600-0854.2004.00252.x.
We have isolated a peroxisome-degradation-deficient (pdd) mutant of the methylotrophic yeast Hansenula polymorpha via gene tagging mutagenesis. Sequencing revealed that the mutant was affected in the HpATG8 gene. HpAtg8 is a protein with high sequence similarity to both Pichia pastoris and Saccharomyces cerevisiae Atg8 and appeared to be essential for selective peroxisome degradation (macropexophagy) and nitrogen-limitation induced microautophagy. Fluorescence microscopy revealed that a GFP.Atg8 fusion protein was located close to the vacuole. After induction of macropexophagy, the GFP.Atg8 containing spot extended to engulf an individual peroxisome. In cells of a constructed deletion strain, sequestration of individual organelles was never completed; analysis of series of serial sections revealed that invariably a minor diaphragm-like opening remained. We hypothesize that H. polymorpha Atg8 facilitates sealing of the sequestering membranes during selective peroxisome degradation.
我们通过基因标签诱变分离出了多形汉逊酵母甲基营养型酵母的过氧化物酶体降解缺陷（pdd）突变体。测序显示该突变体的HpATG8基因受到影响。HpAtg8是一种与巴斯德毕赤酵母和酿酒酵母Atg8序列高度相似的蛋白质，似乎对选择性过氧化物酶体降解（大自噬）和氮限制诱导的微自噬至关重要。荧光显微镜观察显示，GFP.Atg8融合蛋白位于液泡附近。诱导大自噬后，含有GFP.Atg8的斑点扩展以吞噬单个过氧化物酶体。在构建的缺失菌株的细胞中，单个细胞器的隔离从未完成；对一系列连续切片的分析表明，总是会留下一个微小的隔膜样开口。我们推测多形汉逊酵母Atg8在选择性过氧化物酶体降解过程中促进隔离膜的密封。
