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 T ype 2 diabetes-linked region of human chromosome 20q12-13.1. The GLUT10 gen e 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 pro tein 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 m embers of the GLUT family. In addition, we have cloned the mouse cDNA homol og of GLUT10 that encodes a 537 amino acid protein that shares 77.3% identi ty with human GLUT10. The amino acid sequence probably has 12 predicted tra nsmembrane domains and shares characteristics of other mammalian glucose tr ansporters. Human and mouse GLUT10 retain several sequence motifs character istic of mammalian glucose transporters including VP(497)ETKG in the cytopl asmic C-terminus, G(73)R[K,R] between TMD2 and TMD3 (PROSITE PS00216), VD(9 2)RAGRR between TMD8 and TMD9 (PROSITE PS00216), Q(242)QLTG in TMD7, and tr yptophan residues W-430 (TMD10) and W-454 (TMD11), that correspond to tryto phan residues previously implicated in GLUT1 cytochalasin B binding and hex ose 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 sea rch also shows that GLUT10 has lost the SUGAR_TRANSPORT_2 pattern (PS00217) , a result of the substitution G113S in TMD4, while all other known human G LUTs retain the glycine and the pattern match. The significance of this sub stitution is unknown. Sites for N-linked glycosylation are predicted at N-3 34 ATG between TMD8 and TMD9 and N(526)STG in the cytoplasmic C-terminus. N orthern hybridization analysis identified a single 4.4-kb transcript for GL UT10 in human heart, lung, brain, liver, skeletal muscle, pancreas, placent a, and kidney. By RT-PCR analysis, GLUT10 mRNA was also detected in fetal b rain and liver. When expressed in Xenopus oocytes, human GLUT10 exhibited 2 -deoxy-D-glucose transport with an apparent K-m of similar to0.3 mM. D-Gluc ose and D-galactose competed with 2-deoxy-D-glucose and transport was inhib ited by phloretin. The gene localization and functional properties suggest a role for GLUT10 in glucose metabolism and Type 2 diabetes. (C) 2001 Acade mic Press.