Calcium channel regulation: Roles of alpha-2/delta subunit and protein kinase C-betaII

The objectives of the work presented in this thesis were to understand how the α2/δ subunit and protein kinase C-βII (PKC-βII) regulate voltage-gated calcium channels (VGCC). We hypothesized that PKC-βII and the α2/δ peptide would alter the biophysical properties of VGCC in cardiac, neuronal, and skeletal cells. Our experimental approach involved the use of native cells in culture. This is a contrast from cell expression systems such as Xenopus oocytes, and HEK and CHO cells, which have been widely used to study these modulators of, channel function. The α2/δ studies involved the use of gabapentin, a drug that specifically binds to this channel protein. To study PKC we used a transgenic mouse model in which a PKC isoform (PKC-βII) was constitutively and selectively expressed in cardiac muscle.; Our results from the α2/δ studies indicate that this subunit modulates L-type Ca+2 channel gating current, Ca+2 release from the sarcoplasmic reticulum, and Ca+2 influx through VGCC under specific electrophysiological conditions. In addition, work with the PKC-βII transgenic mouse model demonstrate that this isoform greatly augments Ca+2 influx due to enhanced L-type channel current and attenuates Ca+2-dependent inactivation of the L-type channel. The use of the PKC-βII transgenic mouse model has allowed us to examine specific functional changes in VGCC regulation. This study of VGCC function in native cells is more relevant to understanding the global role of Ca2+ channels in ECC signal transduction, and cell physiology. The studies outlined in this thesis research present demonstrate that the α2/δ subunit and PKC-βII are potent regulators of Ca2+ channel properties and excitation-contraction coupling in muscle cells.