Superfund Research Program

Cholinesterase Inhibition as a Target of Pesticide Residues and the Effect of Cholinergic Intervention on Gene Expression

Project Leader: Palmer W. Taylor
Grant Number: P42ES010337
Funding Period: 2000-2010

Project-Specific Links

Final Progress Reports

Year:   2009  2004 

Over the past year the Cholinesterase Inhibition as a Target of Pesticide Residues and the Effect of Cholinergic Intervention on Gene Expression Project, with Dr. Palmer Taylor as Principal Investigator, has been successful in the developing collaborations with other groups to utilize fully the transgenic, knockout mice strains with selective deletions in the acetylcholinesterase gene. Acetylcholinesterase is encoded by a single gene with a constant catalytic core but with alternative mRNA processing at its 3' end leading to different modes of membrane attachment through a lipid-linked subunit, a glycophospholipid link, and a collagen containing subunit. The exon deletions direct the gene to encode on a single membrane attachment. Other modifications of the gene in an enhancesome region produce selective expression in brain, while eliminating expression in skeletal muscle. Researchers have phenotyped the strains, and they have produced fundamental information on the control of gene expression and the localization of the gene products in various synaptic environments. Moreover, these strains are now with collaborators in Paris and Gif sur Yvette who are conducting highly specialized studies on localization of the enzyme at the electron microscope level and the functional consequences of selective deletions of the structural subunits or factors controlling tissue specific expression. These studies have proven informative in understanding toxicities and compensatory responses to organophosphate pesticide exposure. Studies with collaborators will continue who will maintain the strains.

The work with structure of cholinesterases segued into studies with a related a,b-hydrolase fold protein, neuroligin, whose mutations appear to be linked to certain of the autism spectrum disorders. Neuroligin is a heterophilic adhesion molecule that is post-synaptically located and interacts with a pre-synaptic partner, neurexin. It is believed to be critical in the maintenance of synaptogenesis. The researchers ongoing studies have established that several neuroligin mutations, along with mutations in partnering proteins such as caspr-2 and neurexin give rise to altered expression the gene product. Most of these mutations are folding mutations that cause some aberration in the processing and trafficking of the protein where it is retained in the endoplasmic reticulum. Moreover, there are other mutations in conserved residues of the a,b-hydrolase fold proteins that also cause similar trafficking deficiencies. The detailed analysis of trafficking that researchers have well underway provides insights into the severity of the condition and reveals possible therapeutic avenues into treatment of the autism spectrum disorders. Already, researchers have firm data showing a congenital base at a molecular level for a fraction of the autism spectral disorders. Finally, expression of the mutant proteins should be conducted in the context of a neuron in order to examine the transport from soma through the axon trunk to the dendritic processes where synapse formation occurs. To this end, researcheres have developed a timeSTAMP technique using the green fluorescent protein that enables us to measure the trafficking process for the protein of interest in intact single neurons during synaptogenesis. Hence researchers now have a neuron based assay system to phenotype alterations in synaptic adhesion proteins.