LVA CALCIUM CHANNEL AND PANCREATIC B CELL DEATH

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DESCRIPTION (Adapted from applicant's abstract): Insulin dependent diabetes mellitus (IDDM) is characterized by the selective destruction of B-cells of the pancreatic Islets of Langerhans. The principal investigator's previous studies suggest that a low-voltage-activated (LVA) Ca2+ channel may be involved in the process of cytokine-mediated B-cell death. In this proposal, he will test the hypothesis that "abnormal regulation of LVA calcium channels by cytokines and other factors changes B-cell calcium homeostasis, predisposing these cells to further toxicities causing B-cell destruction during insulitis." The aims of the proposed study include: 1) To identify the role of the LVA calcium channels in mediating calcium influx and apoptosis in pancreatic B-cells. LVA Ca2+ channel antagonists will be used to evaluate the role of LVA Ca2+ channels in basal, glucose- and depolarization-stimulated Ca2+ influx. The role of LVA Ca2+ channels in time- and dose-dependent DNA fragmentation and cell death induced by cytokines will also be investigated. 2) To clone the LVA channel from an insulin secreting cell line, INS-1. By using RT-PCR method, we will deduce the nucleotide sequence of the putative alpha1 subunit of the LVA Ca2+ channel and express it in Xenopus oocytes. 3) To investigate the mechanisms of LVA calcium channel regulation. The investigator will examine how cytokines and sex hormones regulate the expression of LVA Ca2+ channels in diabetic and non-diabetic animal models. This study will provide significant insight into the mechanisms of pathogenesis of selective B-cell destruction in human IDDM.