Sequence and functional analysis of GLUT10: a glucose transporter in the Type 2 diabetes-linked region of chromosome 20q12-13.1

We have carried out a detailed sequence and functional analysis of a novel human facilitative glucose transporter, designated GLUT10, located in the Type 2 diabetes-linked region of human chromosome 20q12–13.1. The GLUT10 gene is located between D20S888 and D20S891 and is encoded by 5 exons spanning 26.8 kb of genomic DNA. The human GLUT10 cDNA encodes a 541 amino acid protein that shares between 31 and 35% amino acid identity with human GLUT1–8. The predicted amino acid sequence of GLUT10 is nearly identical in length to the recently described GLUT9 homologue, but is longer than other known members of the GLUT family. In addition, we have cloned the mouse cDNA homologof GLUT10 that encodes a 537 amino acid protein that shares 77.3% identity with human GLUT10. The amino acid sequence probably has 12 predictedtransmembrane domains and shares characteristics of other mammalian glucose transporters. Human and mouse GLUT10 retain several sequence motifs characteristic of mammalian glucosetransporters including VP 497 ETKG in the cytoplasmic C-terminus, G 73 R[K,R] between TMD2 and TMD3 (PROSITE PS00216), VD 92 RAGRR between TMD8 and TMD9 (PROSITE PS00216), Q 242 QLTG in TMD7, and tryptophan residues W 430 (TMD10) and W 454 (TMD11), that correspond to trytophan residues previously implicated in GLUT1 cytochalasin B binding and hexose transport. Neither human nor mouse GLUT10 retains the full P[E,D,N]SPR motif after Loop6 but instead is replaced with P 186 AG[T,A]. A PROSITE search also shows that GLUT10 has lost the SUGARTRANSPORT2 pattern (PS00217), a result of the substitution G113S in TMD4, while all other known human GLUTs retain the glycine and the pattern match. The significance of this substitution is unknown. Sites for N-linked glycosylation are predicted at N 334 ATG between TMD8 and TMD9 and N 526 STG in the cytoplasmic C-terminus. Northern hybridization analysis identified a single 4.4-kb transcript for GLUT10 in human heart, lung, brain, liver, skeletal muscle, pancreas, placenta, and kidney. By RT-PCR analysis, GLUT10 mRNA was also detected in fetal brain and liver. When expressed in Xenopus oocytes, human GLUT10 exhibited 2-deoxy- d -glucose transport with an apparent K m of ∼0.3 mM. d -Glucose and d -galactose competed with 2-deoxy- d -glucose and transport was inhibited by phloretin. The gene localization and functional properties suggest a role for GLUT10 in glucose metabolism and Type 2 diabetes.