We are using mouse embryonic stem cell approaches to introduce novel genetic mutations into the PKA regulatory system and investigating the major physiological functions of this signal transduction cascade. The mouse allows a full complement of genetic manipulations and in most instances provides a relevant model of human physiology, behavior, and disease. We use genetic techniques to produce tissue-specific activation or inactivation of PKA subunits and AKAPs (PKA scaffolding proteins). The lab has also developed a chemical-genetic approach that will allow drug dependent control of kinase activity in specific cell types in vivo


Energy Homeostasis and Body Weight Regulation:

This project is focused on the physiological functions of PKA in the regulation of adiposity, feeding, and energy expenditure.  Targeted disruption of the RIIbeta regulatory subunit gene of PKA creates mice that are lean and resistant to obesity and display a two-fold increase in nocturnal activity.  These phenotypes have recently been traced to the brain and we are focusing our efforts on determining the brain regions and specific cell types that are responsible.


Memory and Learning:

PKA and its associated scaffolding proteins are major regulators of neuronal function.  We are creating mice with mutations in the key regulatory, catalytic, and scaffolding proteins associated with the PKA system and testing their ability to learn and respond to neuromodulators like dopamine and norepinephrine that depend on  cAMP-mediated pathways.


Cell-Type-Specific Labeling Technologies: The RiboTag Mouse

Over the past several years tha lab has worked in collaboration with the laboratory of Dr. David R. Morris to develop a cell-type-specific in vivo labeling technology that allows us to look at changes in gene expression under meaningful physiological states in unique cell types. The key to this technology is our ability to label the translating ribosomes from specific cell types in the contect of a highly complex tissue like brain or testis. We achieve this by modifying endogenous core ribosomal protein genes and adding an epitope tag on the end of the ribosomal protein that can be cell-type-specifically activated using Cre recombinase LoxP technology. By crossing our RiboTag mouse to virtually any Cre Driver line, we can tag ribosomes in any cell type for which a good Cre Driver exists. We are currently applying this technology to study neuronal circuits in the brain and Sertoli and Leydig cell function in the testis.


Cardiac Function: 

The release and reuptake of calcium during excitation/contraction coupling in the heart is dynamically regulated by the sympathetic nervous system.  The interaction of norepinephrine and epinephrine with adrenergic receptors initiates a spatially localized and highly interactive repertoire of intracellular signaling events that leads to changes in the rate and force of contraction. One of the key intracellular second messengers that respond primarily to beta-adrenergic receptor stimulation is cAMP and a major effector of cAMP action in the heart is the PKA family of kinases.  PKA is targeted to receptors and substrates in the heart by members of the AKAP family of scaffolding proteins and this is believed to facilitate the rapid and specific phosphorylation of key regulators of calcium transients. This project is focused on the specific biochemical and physiological roles of PKA and its AKAP binding partners and utilizes mouse genetic approaches to address these processes.