In nerve, muscle and secretory cells, voltage-gated Ca2+ channels transduce membrane electrical signals into a cytosolic Ca2+ signal that initiates a variety of cellular processes, including release of neurotransmitter, contraction of muscle and alteration of gene expression. Ca2+ channels trigger these processes by opening in response to electrical stimulation and allowing Ca2+ ions to flow into cells, where these ions act as signaling molecules that can be detected by Ca2+ binding proteins.
Our research is focused upon how voltage-gated Ca2+ channels open and selectively transport Ca2+, and how these channels are modulated by neurotransmitter receptors. The emphasis is upon the structural and mechanistic bases of these processes, making use of molecular biological, electrophysiological and optical methods. Three specific areas of research are underway:
We combine single-channel patch clamp and two-electrode voltage clamp electrophysiology with site-directed mutagenesis to identify and characterize the molecular features in the ion-conducting pore of Ca2+ channels that enable them to rapidly and selectively deliver Ca2+ to the cytoplasm.
We employ fluorescence resonance energy transfer to study mechanisms and rates of interaction between Ca2+ channel subunits, GTP-binding proteins, and protein kinase C isoforms in living cells. These studies rely on the use of complementary pairs of fluorescently-labeled proteins (e.g., Ca2+ channel subunits) and a fast agonist application system to initiate the protein-protein interactions of interest.
We use whole-cell patch clamp recording from neurons in brain slices to investigate the role of distinct Ca2+ channel subtypes in helping to regulate the circadian rhythms generated in the suprachiasmatic nucleus, the brain's master clock.