Role of synaptic phosphatidylinositol 3-kinase in a behavioral learning response in C. elegans.

The phosphatidylinositol 3-kinase (PI3K) pathway regulates many cellular functions, but its roles in the nervous system are still poorly understood. We found that a newly discovered insulin receptor isoform, DAF-2c, is translocated from the cell body to the synaptic region of the chemosensory neuron in Caenorhabditis elegans by a conditioning stimulus that induces taste avoidance learning. This translocation is essential for learning and is dependent on the mitogen-activated protein kinase-regulated interaction of CASY-1 (the calsyntenin ortholog) and kinesin-1. The PI3K pathway is required downstream of the receptor. Light-regulated activation of PI3K in the synaptic region, but not in other parts of the cell, switched taste-attractive behavior to taste avoidance, mimicking the effect of conditioning. Thus, synaptic PI3K is crucial for the behavioral switch caused by learning.