Mutant HNF-1alpha and mutant HNF-1beta identified in MODY3 and MODY5 downregulate DPP-IV gene expression in Caco-2 cells.
Dipeptidylpeptidase IV (DPP-IV) is a well-documented drug target for the treatment of type 2 diabetes. Hepatocyte nuclear factors (HNF)-1alpha and HNF-1beta, known as the causal genes of MODY3 and MODY5, respectively, have been reported to be involved in regulation of DPP-IV gene expression. But, it is not completely clear (i) that they play roles in regulation of DPP-IV gene expression, and (ii) whether DPP-IV gene activity is changed by mutant HNF-1alpha and mutant HNF-1beta in MODY3 and MODY5. To explore these questions, we investigated transactivation effects of wild HNF-1alpha and 13 mutant HNF-1alpha, as well as wild HNF-1beta and 2 mutant HNF-1beta, on DPP-IV promoter luciferase gene in Caco-2 cells by means of a transient experiment. Both wild HNF-1alpha and wild HNF-1beta significantly transactivated DPP-IV promoter, but mutant HNF-1alpha and mutant HNF-1beta exhibited low transactivation activity. Moreover, to study whether mutant HNF-1alpha and mutant HNF-1beta change endogenous DPP-IV enzyme activity, we produced four stable cell lines from Caco-2 cells, in which wild HNF-1alpha or wild HNF-1beta, or else respective dominant-negative mutant HNF-1alphaT539fsdelC or dominant-negative mutant HNF-1betaR177X, was stably expressed. We found that DPP-IV gene expression and enzyme activity were significantly increased in wild HNF-1alpha cells and wild HNF-1beta cells, whereas they decreased in HNF-1alphaT539fsdelC cells and HNF-1betaR177X cells, compared with DPP-IV gene expression and enzyme activity in Caco-2 cells. These results suggest that both wild HNF-1alpha and wild HNF-1beta have a stimulatory effect on DPP-IV gene expression, but that mutant HNF-1alpha and mutant HNF-1beta attenuate the stimulatory effect.
Gu
Ning
N
Laboratory of Metabolism, Graduate School of Human and Environmental Studies, Kyoto University, Kyoto, Japan.
Adachi
Tetsuya
T
Matsunaga
Tetsuro
T
Takeda
Jun
J
Tsujimoto
Gozoh
G
Ishihara
Akihiko
A
Yasuda
Koichiro
K
Tsuda
Kinsuke
K
D018938:Caco-2 Cells; D003924:Diabetes Mellitus, Type 2 / Q000235:genetics*; D018819:Dipeptidyl Peptidase 4 / Q000235:genetics* / Q000378:metabolism; D015536:Down-Regulation; D015870:Gene Expression; D051538:Hepatocyte Nuclear Factor 1-alpha / Q000235:genetics* / Q000378:metabolism*; D051539:Hepatocyte Nuclear Factor 1-beta / Q000235:genetics* / Q000378:metabolism*; D006801:Humans; D009154:Mutation / Q000235:genetics; D011401:Promoter Regions, Genetic / Q000235:genetics; D011485:Protein Binding; D015533:Transcriptional Activation / Q000235:genetics
D051538:Hepatocyte Nuclear Factor 1-alpha; D051539:Hepatocyte Nuclear Factor 1-beta; D018819:Dipeptidyl Peptidase 4