Modulation of Ion Channels by Kinase/Phosphate Signaling Complexes in CNS Neurons

Excitatory and inhibitory transmissions in the central nervous system (CNS) are mediated primarily by glutamate and GABAA receptors respectively, both of which contain intrinsic ion channels. A group of intracellular enzymes, termed as protein kinases and phosphatases, can modify the functional properties of these channels by adding or removing phosphates at specific sites on these receptors, a process known as protein phosphorylation and dephosphorylation. This project is to study how these multifunctional signaling enzymes achieve high specificity and efficiency in regulating the activity of glutamate and GABAA receptors in central neurons. Dr. Yan's laboratory will focus on protein kinase C (PKC) and protein phosphatase 2B (PP2B), both of which are fundamental for a broad spectrum of physiological functions in the CNS. The hypothesis is that the PKC anchoring protein RACK1 and PP2B anchoring protein AKAP79 are responsible for targeting and functional coupling of these enzymes to GABAA and glutamate receptor channels, thus facilitating the precise regulation of these substrates. A combination of physiological, anatomical, biochemical, pharmacological and molecular biological approaches will be employed to achieve two specific aims: (1) To study the modulation of GABAA receptor channels by PKC/RACK1 complex. (2) To study the modulation of glutamate channels by PP2B/AKAP79 complex. Experimental methods include patch clamp recording with dialysis of peptides, immunocytochemistry, heterologous expression, antisense knock-down and analysis of knockout mice. Because glutamate and GABAA receptor channels are key players mediating information processing in the CNS, insights gained from this study should clarify the molecular and cellular mechanisms underlying the dynamic regulation of neuronal activity by signaling complexes composed of kinases, phosphatases and their anchoring proteins. Integration of the information will not only provide potential novel targets for drugs, but also lay a solid foundation for understanding the regulation of learning and memory processes.