Brant A M, McCoid S, Thomas H M, Baldwin S A, Davies A, Parker J C, Gibbs E M, Gould G W
Department of Biochemistry, University of Glasgow, Scotland, U.K.
Cell Signal. 1992 Nov;4(6):641-50. doi: 10.1016/0898-6568(92)90045-a.
Glucose transport across the plasma membrane of mammalian cells is mediated by a family of homologous proteins. Each glucose transporter isoform has a specific tissue distribution which relates to that tissue's demand for glucose. The beta-cells of pancreatic islets are known to express a distinct glucose transporter isoform, termed GLUT 2, which has a high Km for glucose. In this study, we examined the glucose transporter content of normal rat islets and three beta cell lines, beta-TC, HIT and RIN cells. We show that at the protein level, GLUT 2 is the only detectable transporter isoform in normal islets, and that all three cell lines also express detectable GLUT 2. In contrast, all three cell lines expressed high levels of GLUT 1, but this isoform was not detected in normal islets. Neither the native islets nor any of the cell lines expressed GLUT 3. The insulin-responsive glucose transporter GLUT 4 was detected at very low levels in beta-TC cells; to our knowledge, this is the only non-muscle or adipose cell line which expresses this isoform. We propose that the elevated level of GLUT 1 expression, together with a reduced expression of the high Km transporter GLUT 2, may account for the characteristic aberrant patterns of glucose-stimulated insulin release in cell lines derived from beta-cells.
葡萄糖跨哺乳动物细胞质膜的转运是由一族同源蛋白介导的。每种葡萄糖转运体同工型都有特定的组织分布，这与该组织对葡萄糖的需求有关。已知胰岛的β细胞表达一种独特的葡萄糖转运体同工型，称为GLUT 2，它对葡萄糖具有高Km值。在本研究中，我们检测了正常大鼠胰岛以及三种β细胞系（β-TC、HIT和RIN细胞）中的葡萄糖转运体含量。我们发现，在蛋白质水平上，GLUT 2是正常胰岛中唯一可检测到的转运体同工型，并且所有三种细胞系也都表达可检测到的GLUT 2。相比之下，所有三种细胞系都高水平表达GLUT 1，但在正常胰岛中未检测到这种同工型。天然胰岛和任何一种细胞系均未表达GLUT 3。胰岛素反应性葡萄糖转运体GLUT 4在β-TC细胞中以极低水平被检测到；据我们所知，这是唯一表达这种同工型的非肌肉或脂肪细胞系。我们提出，GLUT 1表达水平的升高，以及高Km转运体GLUT 2表达的降低，可能是导致源自β细胞的细胞系中葡萄糖刺激的胰岛素释放出现特征性异常模式的原因。
