Conditional expression of hepatocyte nuclear factor-1beta, the maturity-onset diabetes of the young-5 gene product, influences the viability and functional competence of pancreatic beta-cells.
Mutations in the gene encoding hepatocyte nuclear factor (HNF)1beta result in maturity-onset diabetes of the young-(MODY)5, by impairing insulin secretory responses and, possibly, by reducing beta-cell mass. The functional role of HNF1beta in normal beta-cells is poorly understood; therefore, in the present study, wild-type (WT) HNF1beta, or one of two naturally occurring MODY5 mutations (an activating mutation, P328L329del, or a dominant-negative form, A263insGG) were conditionally expressed in the pancreatic beta-cell line, insulin-1 (INS-1), and the functional consequences examined. Surprisingly, overexpression of the dominant-negative mutant did not modify any of the functional properties of the cells studied (including insulin secretion, cell growth and viability). By contrast, expression of WT HNF1beta was associated with a time- and dose-dependent inhibition of INS-1 cell proliferation and a marked increase in apoptosis. Induction of WT HNF1beta also inhibited the insulin secretory response to nutrient stimuli, membrane depolarisation or activation of protein kinases A and C and this correlated with a significant decrease in pancrease-duodenum homeobox-1 protein levels. The attenuation of insulin secretion was, however, dissociated from the inhibition of proliferation and loss of viability, since expression of the P328L329del mutant led to a reduced rate of cell proliferation, but failed to induce apoptosis or to alter insulin secretion. Taken together, the present results suggest that mature rodent beta-cells are sensitive to increased expression of WT HNF1beta and they imply that the levels of this protein are tightly regulated to maintain secretory competence and cell viability.
Welters
Hannah J
HJ
Institute of Biomedical and Clinical Science, Peninsula Medical School, Universities of Exeter and Plymouth, Research Way, Plymouth, Devon PL6 8BU, UK.
Senkel
Sabine
S
Klein-Hitpass
Ludger
L
Erdmann
Silke
S
Thomas
Heike
H
Harries
Lorna W
LW
Pearson
Ewan R
ER
Bingham
Coralie
C
Hattersley
Andrew T
AT
Ryffel
Gerhart U
GU
Morgan
Noel G
NG
D017209:Apoptosis / Q000235:genetics; D015153:Blotting, Western / Q000379:methods; D002460:Cell Line; D049109:Cell Proliferation; D003924:Diabetes Mellitus, Type 2 / Q000235:genetics / Q000378:metabolism*; D015870:Gene Expression; D051539:Hepatocyte Nuclear Factor 1-beta / Q000235:genetics* / Q000378:metabolism; D018398:Homeodomain Proteins / Q000235:genetics; D006801:Humans; D007328:Insulin / Q000378:metabolism; D000078790:Insulin Secretion; D050417:Insulin-Secreting Cells / Q000378:metabolism*; D009154:Mutation; D020411:Oligonucleotide Array Sequence Analysis; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015534:Trans-Activators / Q000235:genetics
D018398:Homeodomain Proteins; D007328:Insulin; D015534:Trans-Activators; C084010:pancreatic and duodenal homeobox 1 protein; D051539:Hepatocyte Nuclear Factor 1-beta