ABSTRACT
The TOR pathway mediates nutrient-responsive regulation of cell growth and metabolism in animals. TOR Complex 1 activity depends, amongst other things, on amino acid availability. MAP4K3 was recently implicated in amino-acid signaling in cell culture. We report here the physiological characterization of MAP4K3 mutant flies. Flies lacking MAP4K3 have reduced TORC1 activity detected by phosphorylation of S6K and 4EBP. Furthermore MAP4K3 mutants display phenotypes characteristic of low TORC1 activity and low nutrient availability, such as reduced growth rate, small body size, and low lipid reserves. The differences between control and MAP4K3 mutant animals diminish when animals are reared in low-nutrient conditions, suggesting that the ability of TOR to sense amino acids is most important when nutrients are abundant. Lastly, we show physical interaction between MAP4K3 and the Rag GTPases raising the possibility they might be acting in one signaling pathway.
Subject(s)
Drosophila Proteins/physiology , Drosophila/metabolism , Gene Expression Regulation, Developmental , Mutation , Protein Serine-Threonine Kinases/physiology , Animals , Animals, Genetically Modified , Body Size , Drosophila Proteins/genetics , GTP Phosphohydrolases/metabolism , Lipids/chemistry , Male , Models, Biological , Models, Genetic , Phenotype , Phosphorylation , Protein Serine-Threonine Kinases/genetics , Ribosomal Protein S6 Kinases/metabolismABSTRACT
The 5.5 Mb chromosome 7q21-22 ACHE/PON1 locus harbours the ACHE gene encoding the acetylcholine hydrolyzing, organophosphate (OP)-inhibitable acetylcholinesterase protein and the paraoxonase gene PON1, yielding the OP-hydrolyzing PON1 enzyme which also displays arylesterase activity. In search of inherited and acquired ACHE-PON1 interactions we genotyped seven polymorphic sites and determined the hydrolytic activities of the corresponding plasma enzymes and of the AChE-homologous butyrylcholinesetrase (BChE) in 157 healthy Israelis. AChE, arylesterase, BChE and paraoxonase activities in plasma displayed 5.4-, 6.5-, 7.2- and 15.5-fold variability, respectively, with genotype-specific differences between carriers of distinct compound polymorphisms. AChE, BChE and arylesterase but not paraoxonase activity increased with age, depending on leucine at PON1 position 55. In contrast, carriers of PON1 M55 displayed decreased arylesterase activity independent of the - 108 promoter polymorphism. Predicted structural consequences of the PON1 L55M substitution demonstrated spatial shifts in adjacent residues. Molecular modelling showed substrate interactions with the enzyme variants, explaining the changes in substrate specificity induced by the Q192R substitution. Intriguingly, PON1, but not BChE or arylesterase, activities displayed inverse association with AChE activity. Our findings demonstrate that polymorphism(s) in the adjacent PON1 and ACHE genes affect each other's expression, predicting for carriers of biochemically debilitating ACHE/PON1 polymorphisms adverse genome-environment interactions.
Subject(s)
Acetylcholinesterase/metabolism , Aryldialkylphosphatase/metabolism , Polymorphism, Genetic , Acetylcholinesterase/chemistry , Acetylcholinesterase/genetics , Adult , Age Factors , Aged , Aged, 80 and over , Amino Acid Motifs/physiology , Animals , Aryldialkylphosphatase/chemistry , Aryldialkylphosphatase/genetics , Butyrylcholinesterase/blood , Butyrylcholinesterase/chemistry , Butyrylcholinesterase/genetics , COS Cells , Carboxylic Ester Hydrolases/blood , Chlorocebus aethiops , Female , Gene Frequency , Genotype , Humans , Male , Middle Aged , Models, Molecular , Mutation , Phenotype , RNA, Messenger/biosynthesis , Reverse Transcriptase Polymerase Chain Reaction/methodsABSTRACT
Exposure to agricultural insecticides, together with yet incompletely understood predisposing genotype/phenotype elements, notably increase the risk of Parkinson's disease. Here, we report findings attributing the increased risk in an insecticide-exposed rural area in Israel to interacting debilitating polymorphisms in the ACHE/PON1 locus and corresponding expression variations. Polymorphisms that debilitate PON1 activity and cause impaired AChE overproduction under anticholinesterase exposure were strongly overrepresented in patients from agriculturally exposed areas, indicating that they confer risk of Parkinson's disease. Supporting this notion, serum AChE and PON1 activities were both selectively and significantly lower in patients than in healthy individuals and in carriers of the risky polymorphisms as compared with other Parkinsonian patients. Our findings suggest that inherited interactive weakness of AChE and PON1 expression increases the insecticide-induced occurrence of Parkinson's disease.
