Strategy for identification of novel glucose transporter family members byusing Internet-based genomic databases

Background. We previously reported that medullary thyroid carcinomas and ph eochromocytomas avidly take up the glucose analog fluoro-deoxyglucose on po sitron emission tomography but do not express any of the known human facili tative glucose transporters. We therefore hypothesized that a novel glucose transporter is responsible for glucose uptake in these tumors. Methods. Internet-based Expressed Sequence Tags and high throughput genome sequence databases were screened for novel sequences homologous to the know n glucose transporters. Derived clones were used to screen cDNA libraries. Sequence comparison and hydropathic analysis of the putative proteins were performed. Results, We identified 2 novel genes (GLUTS and GLUT9) that ali-e members o f the facilitative glucose transporter family. The putative GLUT8 and GLUT9 proteins have 44% and 31% sequence identity 50 GLUT5 and GLUT3 respectivel y. Hydropathic analysis showed both have exofacial and transmembrame domain s consistent with a hexose transporter. Conclusions, By using the Expressed Sequence Tags database, we identified n ovel members of the glucose transporter family. Further work will establish function and expression patterns in medullary thyroid carcinomas and pheoc hromocytomas. Internet-based genomic databases allow rapid screening. and i dentification of candidate sequences of novel members of human gene familie s.