The focus of this application is the neuropeptide calcitorin gene-related (CGRP). The importance of CGRP is illustrated by clinical observations that CGRP levels are elevated in migraines ad are attenuated by antimigrain 5-HT1 receptor agonists that act on trigeminal nerves. However, the mechanisms that regulate CGRP expression in trigeminal neurons are not known. In this application, a series of studies on CGRP gene expression have been proposed that extend from cell lines to in vivo measurements of promoter activity in trigeminal neurons. The first major goal will be to examine the signaling mechanism controlling the CGRP cell-specific enhancer. A unique feature of this enhancer is that it is repressed by both 5-HT1 agonists and nuclear receptor ligands. We will test the hypotheses that these agents converge on the enhancer by repression of MAP kinase activation by distinct mechanisms. The roles of a winged helix transcription factor that binds the enhancer and a novel kinase, SLK, that we have cloned will be examined. SLK interacts with the retinoic acid receptor in a ligand dependent manner and is predicted to lie in a MAP kinase pathway. The second major goal is to extend these gene regulation studies to trigeminal neurons in culture and in vivo. We will use adenoviral vectors and transgenic mice to test the hypotheses that activation of MAP kinase pathways by neurotrophins and inflammatory signals increase CGRP enhancer activity and that 5-HT1 agonists and nuclear receptor ligands suppress that activation. NGF and bradykinin will be used to activate MAP kinases in the cultured neurons and temporomandibular joint (TMJ) inflammation will be used to stimulate trigeminal neurons in vivo. Overall, the goal of theses studies is to obtain insight into the regulation of CGRP gene expression that will ultimately facilitate therapeutic strategies for migraine.
