Sopjani Mentor, Bhavsar Shefalee K, Fraser Scott, Kemp Bruce E, Föller Michael, Lang Florian
Department of Physiology, University of Tübingen, Tübingen, Germany.
Mol Membr Biol. 2010 Apr;27(2-3):137-44. doi: 10.3109/09687681003616870.
AMP-activated protein kinase (AMPK), a serine/threonine kinase activated upon energy depletion, stimulates energy production and limits energy utilization. It has previously been shown to enhance cellular glucose uptake through the GLUT family of facilitative glucose transporters. The present study explored the possibility that AMPK may regulate Na+-coupled glucose transport through SGLT1 (SLC5A1). To this end, SGLT1 was expressed in Xenopus oocytes with and without AMPK and electrogenic glucose transport determined by dual electrode voltage clamping experiments. In SGLT1-expressing oocytes but not in oocytes injected with water or expressing constitutively active (gammaR70Q)AMPK (alpha1beta1gamma1(R70Q)) alone, the addition of glucose to the extracellular bath generated a current (I(g)), which was half maximal (K(M)) at approximately 650 microM glucose concentration. Coexpression of (gammaR70Q)AMPK did not affect K(M) but significantly enhanced the maximal current (approximately 1.7 fold). Coexpression of wild type AMPK or the kinase dead (alphaK45R)AMPK mutant (alpha1(K45R)beta1gamma1) did not appreciably affect I(g). According to confocal microscopy and Western Blotting, AICAR (1 mM), phenformin (1 mM) and A-769662 (10 microM) enhanced the SGLT1 protein abundance in the cell membrane of Caco2 cells suggesting that AMPK activity may increase membrane translocation of SGLT1. These observations support a role for AMPK in the regulation of Na+-coupled glucose transport.
AMP激活的蛋白激酶（AMPK）是一种在能量耗竭时被激活的丝氨酸/苏氨酸激酶，可刺激能量产生并限制能量利用。此前已表明它可通过促进性葡萄糖转运蛋白的GLUT家族增强细胞对葡萄糖的摄取。本研究探讨了AMPK可能通过SGLT1（SLC5A1）调节钠偶联葡萄糖转运的可能性。为此，在有或没有AMPK的非洲爪蟾卵母细胞中表达SGLT1，并通过双电极电压钳实验测定电生性葡萄糖转运。在表达SGLT1的卵母细胞中，而非仅注射水或表达组成型活性（gammaR70Q）AMPK（alpha1beta1gamma1（R70Q））的卵母细胞中，向细胞外浴液中添加葡萄糖会产生电流（I(g)），在约650 microM葡萄糖浓度下达到半数最大电流（K(M)）。（gammaR70Q）AMPK的共表达不影响K(M)，但显著增强了最大电流（约1.7倍）。野生型AMPK或激酶失活的（alphaK45R）AMPK突变体（alpha1（K45R）beta1gamma1）的共表达对I(g)没有明显影响。根据共聚焦显微镜和蛋白质印迹法，AICAR（1 mM）、苯乙双胍（1 mM）和A - 769662（10 microM）增加了Caco2细胞膜中SGLT1蛋白的丰度，表明AMPK活性可能增加SGLT1的膜转位。这些观察结果支持AMPK在调节钠偶联葡萄糖转运中发挥作用。
