Resistance to a bacterial toxin is mediated by removal of a conserved glycosylation pathway required for toxin-host interactions.
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.
Griffitts
Joel S
JS
Section of Cell and Developmental Biology, University of California, San Diego, La Jolla, California 92093, USA.
Huffman
Danielle L
DL
Whitacre
Johanna L
JL
Barrows
Brad D
BD
Marroquin
Lisa D
LD
Müller
Reto
R
Brown
Jillian R
JR
Hennet
Thierry
T
Esko
Jeffrey D
JD
Aroian
Raffi V
RV
D000595:Amino Acid Sequence; D000818:Animals; D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins / Q000494:pharmacology*; D001427:Bacterial Toxins; D017173:Caenorhabditis elegans; D029742:Caenorhabditis elegans Proteins / Q000737:chemistry / Q000502:physiology*; D003001:Cloning, Molecular; D003593:Cytoplasm / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004330:Drosophila; D029721:Drosophila Proteins; D004331:Drosophila melanogaster; D004705:Endocytosis; D004731:Endotoxins / Q000494:pharmacology*; D005816:Genetic Complementation Test; D006031:Glycosylation; D016695:Glycosyltransferases / Q000737:chemistry / Q000502:physiology*; D006460:Hemolysin Proteins; D007413:Intestinal Mucosa / Q000378:metabolism; D008565:Membrane Proteins / Q000378:metabolism; D008856:Microscopy, Fluorescence; D008954:Models, Biological; D008969:Molecular Sequence Data; D009154:Mutation; D017351:N-Acetylglucosaminyltransferases / Q000378:metabolism; D009844:Oligosaccharides / Q000378:metabolism; D017386:Sequence Homology, Amino Acid
D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins; D001427:Bacterial Toxins; D029742:Caenorhabditis elegans Proteins; D029721:Drosophila Proteins; D004731:Endotoxins; D006460:Hemolysin Proteins; D008565:Membrane Proteins; D009844:Oligosaccharides; C103963:brn protein, Drosophila; C030956:insecticidal crystal protein, Bacillus Thuringiensis; C479824:Bre-2 protein, C elegans; C479825:Bre-4 protein, C elegans; D016695:Glycosyltransferases; D017351:N-Acetylglucosaminyltransferases; C037649:N-acetyllactosaminide beta-1,6-N-acetylglucosaminyltransferase