Amino acid mimicry: Insights into glyphosate transport and toxicity to mitochondria

点击翻译按钮获取中文摘要

Extensive use of glyphosate-based herbicides (GBH) has led to glyphosate entering the food chain, and causing human sera and urine levels to increase over time. This exposure has led to numerous claims that glyphosate causes diseases ranging from multiple types of cancer to affecting human development and reproduction. However, no mechanism of glyphosate import into human cells is known; in yeast, importation occurs through the glutamate/ aspartate (D/E) transporters due to its structural resemblance. Glyphosate is thought not to have acute effects on humans because they lack the shikimate pathway that produces aromatic amino acids (WYF), which is inhibited in the presence of glyphosate, and humans instead acquire aromatic amino acids through diet or the gut microbiome. The differences in commercial preparations of glyphosate have complicated the studies because GBHs have surfactants that increase tissue penetration. Yeast can bypass the inhibition of the shikimate pathway when supplemented with (WYF), which permits the assessment of the role of surfactants or, more likely, discover the unknown glyphosate targets. Our initial studies have found that genes regulating mitochondria, DNA damage, and the cell cycle are differentially regulated in GBH treatments. The long-term goal is to identify the glyphosate transportation mechanisms into cells, the brain, and other tissues that affect mitochondrial metabolism. This application's objective is to determine how mitochondrial metabolism is affected by glyphosate alone and in commercial formulations in the model organism S. cerevisiae. Our central hypothesis is that the transport of glyphosate is due to mimicry of glutamate and aspartate; thus, it will affect other enzymes that utilize glutamate and aspartate, especially within the mitochondria. The rationale of this proposal is that mitochondrial effects of glyphosate have a biochemical basis and will provide a mechanistic understanding of cellular effects in vertebrate species. Specific aims proposed are 1. Measure the import of glyphosate into different compartments in different mutants and how adding D/E rescues growth inhibition from glyphosate 2. Measure changes in specific mitochondrial metabolites (ATP and NADH) in glyphosate treated cells. The proposed research is innovative because the hypothesis proposed is using unbiased experiments, such as genome-wide association, transcriptomics, and In-Lab Evolution experiments to determine the mechanism of extra- and intracellular glyphosate transport using D/E transporters. Glyphosate mimics D/E amino acids in transport, so it likely affects other enzymes that use D/E, particularly in the mitochondria. In plants, fungi, and bacteria, D/E transporters have all been implicated in glyphosate transport and glyphosate affecting mitochondrial functions. While humans do not have the shikimate pathway, they have D/E transporters, and conserved mitochondrial proteins that use D/E, which may be the off-targets of glyphosate leading to the range of diseases claimed to have been caused by glyphosate.