Abstract

Facilitative glucose transporters (GLUTs) play crucial roles in glucose utilization and homeostasis. GLUT12 was initially isolated as a novel GLUT4-like transporter involved in insulin-dependent glucose transport. However, tissue distribution and biochemical properties of GLUT12 are not well understood. In this study, we investigated the basic kinetic properties and tissue distribution of GLUT12. Human GLUT12 and GLUT1 were overexpressed and purified using Ni-NTA column chromatography. Reconstituted proteoliposomes showed time-dependent d-glucose transport activity, which was inhibited by phloretin and dehydroascorbate. Dose dependence of glucose transport revealed a K_M and V_max values of 6.4 mM and 1.2 μmol/mg/min, respectively, indicating that GLUT12 is a high-affinity type GLUT. Glucose transport by GLUT12 was inhibited by ATP and glucose-1-phosphate, glucose-6-phosphate and disaccharides (properties similar to those of GLUT1). Indirect immunohistochemistry revealed the distribution of mouse GLUT12 in the apical region of distal tubules and collecting ducts in the kidney and epithelial cells of the jejunum. In addition to these cells, GLUT12 was present in chromaffin cells in the adrenal medulla, the anterior pituitary lobe, as well as the thyroid and pyloric glands. These tissue distributions suggest a unique function of GLUT12, besides that of an insulin-dependent glucose transport.

中文翻译：

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辅助葡萄糖转运蛋白GLUT12的功能表征和组织定位。

摘要

促进性葡萄糖转运蛋白（GLUT）在葡萄糖利用和体内平衡中起着至关重要的作用。GLUT12最初是作为涉及胰岛素依赖性葡萄糖转运的新型GLUT4样转运蛋白而分离的。但是，还没有很好地了解GLUT12的组织分布和生化特性。在这项研究中，我们研究了GLUT12的基本动力学特性和组织分布。使用Ni-NTA柱色谱法过表达和纯化了人GLUT12和GLUT1。重构的蛋白脂质体显示出随时间变化的d-葡萄糖转运活性，其被phreretin和脱氢抗坏血酸抑制。葡萄糖转运的剂量依赖性显示K _M和V _max值分别为6.4 mM和1.2μmol/ mg / min，表明GLUT12是高亲和力型GLUT。ATP和1-磷酸葡萄糖，6-磷酸葡萄糖和二糖（与GLUT1的性质相似）抑制了GLUT12的葡萄糖转运。间接免疫组化显示小鼠GLUT12在远端小管的顶端区域中分布，并在空肠的肾脏和上皮细胞中收集导管。除这些细胞外，GLUT12还存在于肾上腺髓质，垂体前叶以及甲状腺和幽门腺的嗜铬细胞中。这些组织分布表明，除了胰岛素依赖性葡萄糖转运功能外，GLUT12还具有独特的功能。