Adenovirus-mediated expression of the catalytic subunit of glucose-6-phosphatase in INS-1 cells. Effects on glucose cycling, glucose usage, and insulin secretion.

Published

Journal Article

Glucose-6-phosphatase (Glu-6-Pase) catalyzes the terminal step of gluconeogenesis, the conversion of glucose 6-phosphate (Glu-6-P) to free glucose. This enzyme activity is thought to be conferred by a complex of proteins residing in the endoplasmic reticulum (ER), including a Glu-6-P translocase that transports Glu-6-P into the lumen of the ER, a phosphohydrolase catalytic subunit residing in the lumen, and putative glucose and inorganic phosphate transporters that allow exit of the products of the reaction. In this study, we have investigated the effect of adenovirus-mediated overexpression of the Glu-6-Pase catalytic subunit on glucose metabolism and insulin secretion, using a well differentiated insulinoma cell line, INS-1. We found that the overexpressed Glu-6-Pase catalytic subunit was normally glycosylated, correctly sorted to the ER, and caused a 10-fold increase in Glu-6-Pase enzymatic activity in in vitro assays. Consistent with these findings, a 4.2-fold increase in 3H2O incorporation into glucose was observed in INS-1 cells treated with the recombinant adenovirus containing the Glu-6-Pase catalytic subunit cDNA (AdCMV-Glu-6-Pase). 3-[3H]Glucose usage was decreased by 32% in AdCMV-Glu-6-Pase-treated cells relative to controls, resulting in a proportional 30% decrease in glucose-stimulated insulin secretion. Our findings indicate that overexpression of the Glu-6-Pase catalytic subunit significantly impacts glucose metabolism and insulin secretion in islet beta-cells. However, INS-1 cells treated with AdCMV-Glu-6-Pase do not exhibit the severe alterations of beta-cell function and metabolism associated with islets from rodent models of obesity and non-insulin-dependent diabetes mellitus, suggesting the involvement of genes in addition to the catalytic subunit of Glu-6-Pase in the etiology of such beta-cell dysfunction.

Full Text

Duke Authors

Cited Authors

  • Trinh, K; Minassian, C; Lange, AJ; O'Doherty, RM; Newgard, CB

Published Date

  • October 1997

Published In

Volume / Issue

  • 272 / 40

Start / End Page

  • 24837 - 24842

PubMed ID

  • 9312082

Pubmed Central ID

  • 9312082

Electronic International Standard Serial Number (EISSN)

  • 1083-351X

International Standard Serial Number (ISSN)

  • 0021-9258

Digital Object Identifier (DOI)

  • 10.1074/jbc.272.40.24837

Language

  • eng