Department of Biochemistry, Kyorin University School of Medicine, Tokyo, Japan.
PLoS One. 2010 Dec 9;5(12):e15553. doi: 10.1371/journal.pone.0015553.
A variant of the CDKAL1 gene was reported to be associated with type 2 diabetes and reduced insulin release in humans; however, the role of CDKAL1 in β cells is largely unknown. Therefore, to determine the role of CDKAL1 in insulin release from β cells, we studied insulin release profiles in CDKAL1 gene knockout (CDKAL1 KO) mice.
Total internal reflection fluorescence imaging of CDKAL1 KO β cells showed that the number of fusion events during first-phase insulin release was reduced. However, there was no significant difference in the number of fusion events during second-phase release or high K(+)-induced release between WT and KO cells. CDKAL1 deletion resulted in a delayed and slow increase in cytosolic free Ca(2+) concentration during high glucose stimulation. Patch-clamp experiments revealed that the responsiveness of ATP-sensitive K(+) (K(ATP)) channels to glucose was blunted in KO cells. In addition, glucose-induced ATP generation was impaired. Although CDKAL1 is homologous to cyclin-dependent kinase 5 (CDK5) regulatory subunit-associated protein 1, there was no difference in the kinase activity of CDK5 between WT and CDKAL1 KO islets.
CONCLUSIONS/SIGNIFICANCE: We provide the first report describing the function of CDKAL1 in β cells. Our results indicate that CDKAL1 controls first-phase insulin exocytosis in β cells by facilitating ATP generation, K(ATP) channel responsiveness and the subsequent activity of Ca(2+) channels through pathways other than CDK5-mediated regulation.
有报道称 CDKAL1 基因的一种变体与 2 型糖尿病和人类胰岛素释放减少有关；然而，CDKAL1 在β细胞中的作用在很大程度上尚不清楚。因此，为了确定 CDKAL1 在β细胞胰岛素释放中的作用，我们研究了 CDKAL1 基因敲除（CDKAL1 KO）小鼠的胰岛素释放谱。
CDKAL1 KO β细胞的全内反射荧光成像显示，第一相胰岛素释放过程中的融合事件数量减少。然而，WT 和 KO 细胞之间第二相释放或高 K+诱导释放过程中的融合事件数量没有显著差异。CDKAL1 缺失导致高葡萄糖刺激期间细胞浆游离 Ca2+浓度的延迟和缓慢增加。膜片钳实验表明，KO 细胞中 ATP 敏感性 K+(KATP)通道对葡萄糖的反应性减弱。此外，葡萄糖诱导的 ATP 生成受损。尽管 CDKAL1 与周期蛋白依赖性激酶 5（CDK5）调节亚基相关蛋白 1 同源，但 WT 和 CDKAL1 KO 胰岛中 CDK5 的激酶活性没有差异。
结论/意义：我们首次报道了 CDKAL1 在β细胞中的功能。我们的结果表明，CDKAL1 通过促进 ATP 生成、KATP 通道反应性以及随后的 Ca2+通道活性来控制β细胞中的第一相胰岛素胞吐作用，其作用途径不同于 CDK5 介导的调节。
