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Strategy for identification of novel glucose transporter family members by using internet-based genomic databases
J E Phay1, H B Hussain, J F Moley
1Washington University School of Medicine and the St Louis Veteran's Administration Medical Center, St Louis, MO, USA.
Background:
We previously reported that medullary thyroid carcinomas and pheochromocytomas avidly take up the glucose analog fluoro-deoxyglucose on positron emission tomography but do not express any of the known human facilitative 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 known 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 (GLUT8 and GLUT9) that are members of the facilitative glucose transporter family. The putative GLUT8 and GLUT9 proteins have 44% and 31% sequence identity to GLUT5 and GLUT3, respectively. Hydropathic analysis showed both have exofacial and transmembrane domains consistent with a hexose transporter.
Conclusions:
By using the Expressed Sequence Tags database, we identified novel members of the glucose transporter family. Further work will establish function and expression patterns in medullary thyroid carcinomas and pheochromocytomas. Internet-based genomic databases allow rapid screening and identification of candidate sequences of novel members of human gene families.