Fares H, Greenwald I
Department of Biochemistry and Molecular Biophysics, Howard Hughes Medical Institute, Columbia University College of Physicians and Surgeons, New York, New York 10032, USA.
Genetics. 2001 Sep;159(1):133-45. doi: 10.1093/genetics/159.1.133.
The coelomocytes of Caenorhabditis elegans are scavenger cells that continuously and nonspecifically endocytose fluid from the pseudocoelom (body cavity). Green fluorescent protein (GFP) secreted into the pseudocoelom from body wall muscle cells is endocytosed and degraded by coelomocytes. We show that toxin-mediated ablation of coelomocytes results in viable animals that fail to endocytose pseudocoelomic GFP, indicating that endocytosis by coelomocytes is not essential for growth or survival of C. elegans under normal laboratory conditions. We examined known viable endocytosis mutants, and performed RNAi for other known endocytosis genes, for coelomocyte uptake defective (Cup) phenotypes. We also screened for new genes involved in endocytosis by isolating viable mutants with Cup defects; this screen identified 14 different genes, many with multiple alleles. A variety of Cup terminal phenotypes were observed, consistent with defects at various steps in the endocytic pathway. Available molecular information indicates that the Cup mutant screen has identified novel components of the endocytosis machinery that are conserved in mammals but not in Saccharomyces cerevisiae, the only other organism for which large-scale genetic screens for endocytosis mutants have been performed.
秀丽隐杆线虫的体腔细胞是清道夫细胞，它们持续且非特异性地从假体腔（体腔）内吞液体。从体壁肌肉细胞分泌到假体腔中的绿色荧光蛋白（GFP）被体腔细胞内吞并降解。我们发现，毒素介导的体腔细胞消融产生了能够存活但无法内吞假体腔GFP的动物，这表明在正常实验室条件下，体腔细胞的内吞作用对于秀丽隐杆线虫的生长或存活并非必不可少。我们检查了已知的存活内吞突变体，并对其他已知的内吞基因进行RNA干扰，以寻找体腔细胞摄取缺陷（Cup）表型。我们还通过分离具有Cup缺陷的存活突变体来筛选参与内吞作用的新基因；该筛选鉴定出14个不同的基因，其中许多具有多个等位基因。观察到了多种Cup终末表型，这与内吞途径中各个步骤的缺陷一致。现有的分子信息表明，Cup突变体筛选鉴定出了内吞机制的新组分，这些组分在哺乳动物中保守，但在酿酒酵母中不保守，酿酒酵母是唯一进行过大规模内吞突变体遗传筛选的其他生物。
