Proteomic Analysis of Nicotinic Effects on the Mesolimbic Dopamine System

Marina Picciotto, Psychiatry, Pharmacology and Neurobiology, Yale University

Nicotinic acetylcholine receptors (nAChRs) are expressed in most neurons in the central and peripheral nervous system. Activation of nAChRs by nicotine can result in stimulation of many different neurotransmitter systems and result in many behavioral outcomes. Nicotine activates the mesolimbic dopaminergic (DA) system, as has been seen with many other drugs of abuse. Indeed, actions of nicotine on many brain areas may ultimately converge on the mesolimbic DA system, and/or other systems, to result in the neurochemical changes that lead to nicotine addiction. The development of nicotine addiction is likely due to repeated intake of the drug that leads to changes in the brain at many levels including changes in signal transduction and gene expression. We have shown that chronic nicotine results in changes in MAP kinase and CREB signaling in projection regions of the DA neurons and can activate the calcium-dependent phosphatase calcineurin leading to altered glutamate signaling in VTA and cortical neurons. We propose two Proteomics Aims: 1) to use iTraq to identify targets of CREB that are regulated in the DA system following nicotine place preference in wild type and genetically manipulated mice. These changes will be correlated with behavioral effects of nicotine to identify the signal transduction pathways and brain areas most critical for behavioral effects of nicotine. In addition, these analyses will be carried out on knockout mice lacking high affinity nAChRs that do not show relevant behavioral responses to nicotine. This control will help identify signal transduction changes that are not relevant to some of the behavioral effects of nicotine in models of reinforcement.; 2) to use LTQ-Orbitrap to identify changes in phosphorylation state of targets of calcineurin or CaMKI that might be involved in calcium-mediated signaling downstream of nAChRs. We have identified a role for calcium signaling in the VTA in locomotor sensitization to repeated nicotine injection. We would now like to identify substrates for calcium-dependent phosphatases and kinases that mediate those cellular and behavioral effects.