Griffitts Joel S, Huffman Danielle L, Whitacre Johanna L, Barrows Brad D, Marroquin Lisa D, Müller Reto, Brown Jillian R, Hennet Thierry, Esko Jeffrey D, Aroian Raffi V
Section of Cell and Developmental Biology, University of California, San Diego, La Jolla, California 92093, USA.
J Biol Chem. 2003 Nov 14;278(46):45594-602. doi: 10.1074/jbc.M308142200. Epub 2003 Aug 27.
Crystal (Cry) proteins made by the bacterium Bacillus thuringiensis are pore-forming toxins that specifically target insects and nematodes and are used around the world to kill insect pests. To better understand how pore-forming toxins interact with their host, we have screened for Caenorhabditis elegans mutants that resist Cry protein intoxication. We find that Cry toxin resistance involves the loss of two glycosyltransferase genes, bre-2 and bre-4. These glycosyltransferases function in the intestine to confer susceptibility to toxin. Furthermore, they are required for the interaction of active toxin with intestinal cells, suggesting they make an oligosaccharide receptor for toxin. Similarly, the bre-3 resistance gene is also required for toxin interaction with intestinal cells. Cloning of the bre-3 gene indicates it is the C. elegans homologue of the Drosophila egghead (egh) gene. This identification is striking given that the previously identified bre-5 has homology to Drosophila brainiac (brn) and that egh-brn likely function as consecutive glycosyltransferases in Drosophila epithelial cells. We find that, like in Drosophila, bre-3 and bre-5 act in a single pathway in C. elegans. bre-2 and bre-4 are also part of this pathway, thereby extending it. Consistent with its homology to brn, we demonstrate that C. elegans bre-5 rescues the Drosophila brn mutant and that BRE-5 encodes the dominant UDP-GlcNAc:Man GlcNAc transferase activity in C. elegans. Resistance to Cry toxins has uncovered a four component glycosylation pathway that is functionally conserved between nematodes and insects and that provides the basis of the dominant mechanism of resistance in C. elegans.
苏云金芽孢杆菌产生的晶体（Cry）蛋白是一类形成孔道的毒素，它们特异性地作用于昆虫和线虫，在全球范围内用于杀灭害虫。为了更好地理解形成孔道的毒素如何与宿主相互作用，我们筛选了对线虫Cry蛋白中毒具有抗性的秀丽隐杆线虫突变体。我们发现，对Cry毒素的抗性涉及两个糖基转移酶基因bre-2和bre-4的缺失。这些糖基转移酶在肠道中发挥作用，使线虫对毒素敏感。此外，它们是活性毒素与肠道细胞相互作用所必需的，这表明它们构成了毒素的寡糖受体。同样，bre-3抗性基因也是毒素与肠道细胞相互作用所必需的。bre-3基因的克隆表明它是果蝇egghead（egh）基因的秀丽隐杆线虫同源物。鉴于之前鉴定的bre-5与果蝇brainiac（brn）具有同源性，且egh-brn可能在果蝇上皮细胞中作为连续的糖基转移酶发挥作用，这一鉴定结果令人惊讶。我们发现，与果蝇一样，bre-3和bre-5在秀丽隐杆线虫中作用于单一途径。bre-2和bre-4也是该途径的一部分，从而扩展了该途径。与其与brn的同源性一致，我们证明秀丽隐杆线虫的bre-5可以拯救果蝇brn突变体，并且BRE-5在秀丽隐杆线虫中编码主要的UDP-GlcNAc:Man GlcNAc转移酶活性。对Cry毒素的抗性揭示了一种由四个成分组成的糖基化途径，该途径在功能上线虫和昆虫之间是保守的，并且为秀丽隐杆线虫的主要抗性机制提供了基础。
