To understand the biological basis of drug addiction, genetics and neuroscience are two very important elements. Towards this direction, the Pl's research development and training goals are to pursue the development and application of new methodologies based on gene targeting technology and in vivo animal models. In addition, drug abuse research related educational and severice activities have been incorporated into the proposal to further enhance Pl's career development. Agonist-induced opioid receptor phosphorylation is believed to be an important receptor regulatory process that promotes acute receptor desensitization, triggers internalization and recycling of the receptors, and participates the development of tolerance. However, this has not been demonstrated in neuronal systems and whole animals. Therefore, the proposed research plan is aimed to test the hypothesis that MOR phosphorylation is agonist-dependent as well as region or cell specific, and that the receptor's microconformation and cellular signaling components influence the extent of phosphorylation and the development of differential tolerance and dependence in vivo. Using primary culture of DRG neurons as a model, the PI proposes to examine the MOR phosphorylation pattern in DRG neuron and to evaluate its contribution to desensitization in and other receptor regulatory processes by using phosphorylation-deficient mutant receptor. The PI also proposes to determine the effect of receptor dimerization on MOR phosphorylation, exploring the possible contributions of receptor dimerization to the potential regional variation in receptor phosphorylation and the development of opioid tolerance. The PI further proposes to test the hypothesis in vivo by modifying the MOR phosphorylation status in animal through generating MOR phosphorylation-deficient mutant mice using a knock-in approach. A significance of the proposal is that the study is designed to understand the mechanism of opioid action in a physiologically relevant setting.
