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Roles of ATP-sensitive K+ channels in cell survival and differentiation in the endocrine pancreas
T Miki1, T Iwanaga, K Nagashima
1Department of Molecular Medicine, Chiba University Graduate School of Medicine, Japan.
Abstract:
To determine the roles of the ATP-sensitive K+ (K(ATP)) channels in endocrine pancreas more directly, two types of genetically engineered Kir6.2 mice were developed: mice expressing a dominant-negative form of Kir6.2 specifically in beta-cells (Kir6.2G132S Tg mice) and mice lacking Kir6.2 (Kir6.2-/- or Kir6.2 null mice). The Kir6.2G132S Tg mice show severe impairment of K(ATP) channel function only in the beta-cells, whereas Kir6.2 null mice are completely defective in K(ATP) channel function in all of the cells in which Kir6.2 is a constituent of the K(ATP) channels, because of the disruption of Kir6.2. Both types of mice show abnormal architecture of the pancreatic islets. The number of beta-cells in Kir6.2G132S Tg mice decreases markedly with age, whereas that in Kir6.2-/- mice decreases slightly. alpha-Cells, which are normally present only in the periphery of pancreatic islets, also appear in the center of the islets in both Kir6.2G132S Tg and Kir6.2-/- mice. Interestingly, the number of peptide YY (PYY) and glucagon-positive cells is markedly increased in Kir6.2 null mice, whereas the number of PP cells and delta-cells is not altered. Apoptotic cells are detected by the TdT-mediated dUTP nick-end labeling (TUNEL) method at a high frequency in both Kir6.2G372S Tg and Kir6.2-/- mice compared with the respective controls. Thus, studies of Kir6.2G372S Tg and Kir6.2-/- mice indicate that K(ATP) channels play an important role in cell survival and differentiation in the endocrine pancreas.
Insights
ATP-sensitive potassium (K(ATP)) channels are crucial for endocrine pancreas cell survival and differentiation. Genetically engineered mice lacking Kir6.2 or expressing a dominant-negative form show impaired islet architecture and increased apoptosis.
Area of Science:
- Endocrinology
- Molecular Biology
- Genetics
Background:
- ATP-sensitive potassium (K(ATP)) channels are vital for cellular functions.
- Kir6.2 is a key subunit of K(ATP) channels in the endocrine pancreas.
- Understanding K(ATP) channel roles is essential for metabolic research.
Purpose of the Study:
- To elucidate the specific roles of K(ATP) channels in the endocrine pancreas.
- To investigate the impact of impaired K(ATP) channel function on pancreatic islet cells.
- To analyze the consequences of Kir6.2 disruption on beta-cell survival and islet architecture.
Main Methods:
- Development of two genetically engineered mouse models: Kir6.2G132S Tg (dominant-negative Kir6.2 in beta-cells) and Kir6.2-/- (Kir6.2 null).
- Assessment of K(ATP) channel function, pancreatic islet architecture, and cell populations.
- Utilized TdT-mediated dUTP nick-end labeling (TUNEL) to detect apoptosis.
Main Results:
- Both mouse models exhibited abnormal pancreatic islet architecture, including altered alpha-cell distribution.
- Kir6.2G132S Tg mice showed a marked age-dependent decrease in beta-cell number, while Kir6.2-/- mice had a slight decrease.
- Increased apoptosis was observed in both models, suggesting K(ATP) channels are critical for cell survival.
Conclusions:
- K(ATP) channels, through Kir6.2, play a significant role in maintaining endocrine pancreas cell survival.
- Disruption of K(ATP) channel function impacts beta-cell maintenance and islet cell differentiation.
- These findings highlight the importance of K(ATP) channels in pancreatic islet homeostasis.