Neil M. Nathanson
Dept.: Professor of Pharmacology
Neuroscience Focus Groups: Cell and Molecular Neuroscience, Developmental Neuroscience, Neurotransmitters, Modulators, Transporters and Receptors
Our laboratory is interested in the regulation of and the mechanisms responsible for signal transduction in excitable cells. One area of interest is the muscarinic acetylcholine receptors (mAChR), which comprise a family of related receptor proteins which are the products of distinct genes. Muscarinic receptors can regulate the activity of enzymes involved in intracellular second messenger pathways, such as adenylyl and guanylyl cyclases, phospholipase C, phosphodiesterases, and protein kinases, and can also regulate the function of ion channels. The mAChR gene family produces these effects by interacting with the members of a second gene family, the GTP-binding coupling proteins (G-proteins), which are required for receptor function. We are using a combination of molecular genetic, immunological, biochemical, and physiological studies to study the regulation of expression and mechanisms of action of the mAChR, G-proteins, and ion channels whose activity they regulate. We have isolated the genes encoding both mouse and chick mAChR, and are using these to study the mechanisms for regulation of receptor gene expression by innervation, synaptic activity, developmental signals, etc. We are also introducing wildtype and mutant cloned genes for the mAChR into cells lacking the receptors to compare the function and regulation of the different subtypes of receptor. We are particularly interested in the ways that receptor expression and function are altered by various physiological stimuli, and have identified several discrete pathways for both transcriptional and posttranslational regulation of the muscarinic receptors. We have also begun to use gene disruption techniques to generate strains of mice deficient in individual receptor genes to determine the roles that specifc receptor subtypes play in the nervous system. For example, we have found that the m1 receptor plays a crucial role in certain electrophysiological repsonses and in sizure initiation in a widely used model of temporal lobe epilepsy.
We are also interested in mechanisms for the regulation of neuronal function by trophic and differentiation factors. We are using cell and molecular biological techniques to study the regulation and action of the receptors for LIF (leukemia inhibitory factor) and CNTF (ciliary neurotrophic factor), which are important for the survival of certain types of neurons and which induce other classes of neurons to alter the expression of neurotransmitter-synthesizing and neuropeptide genes. We have identified a number of steps in the signal transduction cascade of these receptors, and are determining their roles in the regulation of neuronal function and gene expression. For example, we have demonstrated that stimulation with LIF causes activation of the MAP kinase cascade. MAP kinase in turn then phosphorylates the LIF receptor and regulates its ability to integrate signals from heterologous growth factor receptor pathways. These studies should provide new insights into the molecular mechanisms regulating long-term plasticity and synaptic function in the nervous system.