In type II diabetes, the insulin secreting beta cells of pancreatic islets fail to secrete insulin in sufficient quantities to maintain normal blood glucose levels. The resulting hyperglycemia can Iead to many serious complications. Therefore, understanding the mechanisms that mediate insulin secretion could lead to new therapies to prevent the onset and complications of Type II diabetes. Two Sub-classes of L-type Calcium channels, Cav1.2 and Cav1.3 are expressed in pancreatic beta cells. A """"""""knock in"""""""" method to introduce Cav1.2 and Cav1.3 mutant channels that are insensitive to the dihydropyridine (DHP) class of L-type channel blockers into the insulinoma cell line INS-1 has been described. In this system, the endogenous L-type channels can be """"""""shut off"""""""" with DHP drugs, thus pharmacologically isolating either Cav1.2 of Cav1.3 channels. Using this system, it is shown that Cav1.3 but not Cav1.2 channels can mediate glucose-stimulated insulin secretion, but that both channels can mediate KCI stimulated insulin secretion. Furthermore, the intracellular loop between homologous domains III and IV (II-III loop) of Cav1.3 but not Cav1.2 completely inhibits glucose-stimulated insulin secretion when over-expressed in INS-1 cells. To elucidate the mechanism and structural determinants of the specificity of Cav1.3 coupling glucose-stimulated insulin secretion in INS-1 cells, this proposal will: 1. Determine the mechanism whereby glucose stimulated insulin secretion is specifically coupled to Cav1.3. 2. Identify the molecular determinants of the preferential coupling of Cav1.3 to glucose-stimulated insulin secretion. 3. Identify proteins that interact with intracellular domains of Cav1.3 and mediate the specificity for glucose-induced insulin secretion. 4. Define functional roles for the distal C-terminal tails of Cav 1.2 and Cav1.3 in INS-1 cells. Although much of this work will be done in the INS-1 cell model, adenovirus vectors will be used to introduce mutant channels and channel fragments into primary rat beta cells to repeat key experiments in this more physiologically relevant system. This proposal will utilize techniques such as patch clamp whole-cell electrophysiology, confocal microscopy, and total internal reflection microscopy. This proposal is consistent with the PI's long-term goal of understanding L-type calcium channel modulation and cellular function.

Agency
National Institute of Health (NIH)
Institute
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Type
Research Project (R01)
Project #
5R01DK064736-05
Application #
7348317
Study Section
Metabolism Study Section (MET)
Program Officer
Appel, Michael C
Project Start
2004-04-01
Project End
2009-08-31
Budget Start
2008-02-01
Budget End
2009-08-31
Support Year
5
Fiscal Year
2008
Total Cost
$199,505
Indirect Cost
Name
Purdue University
Department
Pharmacology
Type
Schools of Pharmacy
DUNS #
072051394
City
West Lafayette
State
IN
Country
United States
Zip Code
47907
Pratt, Evan P S; Salyer, Amy E; Guerra, Marcy L et al. (2016) Ca2+ influx through L-type Ca2+ channels and Ca2+-induced Ca2+ release regulate cAMP accumulation and Epac1-dependent ERK 1/2 activation in INS-1 cells. Mol Cell Endocrinol 419:60-71
Wang, Yuchen; Jarrard, Rachel E; Pratt, Evan P S et al. (2014) Uncoupling of Cav1.2 from Ca(2+)-induced Ca(2+) release and SK channel regulation in pancreatic ?-cells. Mol Endocrinol 28:458-76
Jarrard, Rachel E; Wang, Yuchen; Salyer, Amy E et al. (2013) Potentiation of sulfonylurea action by an EPAC-selective cAMP analog in INS-1 cells: comparison of tolbutamide and gliclazide and a potential role for EPAC activation of a 2-APB-sensitive Ca2+ influx. Mol Pharmacol 83:191-205
Lin, Min; Aladejebi, Oluyemi; Hockerman, Gregory H (2011) Distinct properties of amlodipine and nicardipine block of the voltage-dependent Ca2+ channels Ca v 1.2 and Ca v 2.1 and the mutant channels Ca v 1.2/Dihydropyridine insensitive and Ca v 2.1/Dihydropyridine sensitive. Eur J Pharmacol 670:105-13
Jacobo, Sarah Melissa P; Guerra, Marcy L; Jarrard, Rachel E et al. (2009) The intracellular II-III loops of Cav1.2 and Cav1.3 uncouple L-type voltage-gated Ca2+ channels from glucagon-like peptide-1 potentiation of insulin secretion in INS-1 cells via displacement from lipid rafts. J Pharmacol Exp Ther 330:283-93
Jacobo, Sarah Melissa P; Guerra, Marcy L; Hockerman, Gregory H (2009) Cav1.2 and Cav1.3 are differentially coupled to glucagon-like peptide-1 potentiation of glucose-stimulated insulin secretion in the pancreatic beta-cell line INS-1. J Pharmacol Exp Ther 331:724-32
Liu, Guohong; Jacobo, Sarah Melissa P; Hilliard, Nathan et al. (2006) Differential modulation of Cav1.2 and Cav1.3-mediated glucose-stimulated insulin secretion by cAMP in INS-1 cells: distinct roles for exchange protein directly activated by cAMP 2 (Epac2) and protein kinase A. J Pharmacol Exp Ther 318:152-60