Choeiri C, Staines W A, Miki T, Seino S, Renaud J-M, Teutenberg K, Messier C
Psychology Faculty, Fresno Pacific University, 1717 South Chestnut Ave. Fresno, CA 93702, USA.
Behav Brain Res. 2006 Sep 25;172(2):233-9. doi: 10.1016/j.bbr.2006.05.005. Epub 2006 Jun 23.
K-ATP channels formed of the Sur and Kir subunits are widely distributed in the brain. Sur1-Kir6.2 is the most common combination of K-ATP channel subunits in the brain and Kir6.2 plays an important role in glucose metabolism through pancreatic insulin secretion or hypothalamic glucose sensing. K-ATP channels have also been reported to play a role in memory processing. Therefore, the aim of the present experiment is to assess the gene and protein expression of GLUT1, GLUT3 and GLUT4 in various brain regions of Kir6.2(-/-) K-ATP knockout mice and to test their working memory performance. GLUT4 was measured using two antibodies, one recognizing an intracellular epitope and the other, an extracellular epitope. Relative to their corresponding wild type, semi-quantitative immunohistochemistry showed that GLUT4 protein expression as measured by a GLUT4 antibody recognizing an extracellular epitope was increased in the Kir6.2(-/-) K-ATP mice. However, there was only a small increase in GLUT4 labeling using the GLUT4 antibody recognizing the intracellular epitope. These results suggest a compensatory higher GLUT4 inclusion at the cellular neuronal membrane in the cerebral cortex, hippocampus and cerebellum of the Kir6.2(-/-) K-ATP knockout mice. However, there was no change in GLUT4 gene expression assessed by TaqMan PCR except for a decrease in the cerebellum of these mice. Working memory performance of the Kir6.2(-/-) K-ATP mice was disrupted at age of 12 weeks but not at 5 weeks. The mild glucose intolerance that is observed in the Kir6.2 knockout mice is unlikely to have created the memory deficits observed. Rather, in light of the effects of K-ATP channel modulators on memory, the memory deficits in the Kir6.2(-/-) K-ATP mice are more likely due to the absence of the Kir6.2 and possible disruption of the GLUT4 activity in the brain.
由磺脲类受体（Sur）和内向整流型钾通道（Kir）亚基构成的钾离子-腺苷三磷酸酶（K-ATP）通道广泛分布于大脑中。Sur1-Kir6.2是大脑中K-ATP通道亚基最常见的组合形式，且Kir6.2通过胰腺胰岛素分泌或下丘脑葡萄糖感知在葡萄糖代谢中发挥重要作用。据报道，K-ATP通道在记忆处理过程中也发挥作用。因此，本实验的目的是评估Kir6.2基因敲除（-/-）K-ATP基因敲除小鼠不同脑区中葡萄糖转运蛋白1（GLUT1）、葡萄糖转运蛋白3（GLUT3）和葡萄糖转运蛋白4（GLUT4）的基因和蛋白表达，并测试其工作记忆表现。使用两种抗体检测GLUT4，一种识别细胞内表位，另一种识别细胞外表位。相对于相应的野生型，半定量免疫组织化学显示，用识别细胞外表位的GLUT4抗体检测，Kir6.2基因敲除（-/-）K-ATP小鼠中GLUT4蛋白表达增加。然而，使用识别细胞内表位的GLUT4抗体时，GLUT4标记仅有小幅增加。这些结果表明Kir6.2基因敲除（-/-）K-ATP基因敲除小鼠大脑皮质、海马体和小脑中，细胞神经元膜上存在补偿性更高的GLUT4内吞。然而，除了这些小鼠小脑中GLUT4基因表达下降外，通过TaqMan聚合酶链反应（PCR）评估的GLUT4基因表达没有变化。Kir6.2基因敲除（-/-）K-ATP小鼠在12周龄时工作记忆表现受损，但在5周龄时未受损。在Kir6.2基因敲除小鼠中观察到轻度葡萄糖不耐受不太可能导致所观察到的记忆缺陷。相反，鉴于K-ATP通道调节剂对记忆的影响，Kir6.2基因敲除（-/-）K-ATP小鼠的记忆缺陷更可能是由于缺乏Kir6.2以及大脑中GLUT4活性可能受到破坏所致。
