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/Drug Addiction:
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.
Sperm Capacitation and Oocyte Maturation:
PKA activity is the gatekeeper that determines the onset of sperm capacitation and regulates the timing of oocyte maturation. We are investigating the signaling of PKA in both sperm and oocyte with the goal of understanding both the downstream regulatory events that respond to PKA stimulation and the more translational questions of whether modifiers of the PKA system could be useful in either preventing or improving fertility in males and females. These studies will be primarily conducted in mice to take advantage of targeted genetic mutations in the system, but key aspects of the regulatory pathways will also be tested in human sperm and oocytes.
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.