Characterization of the distal promoter of the human pyruvate carboxylase gene in pancreatic beta cells.

Pyruvate carboxylase (PC) is an enzyme that plays a crucial role in many biosynthetic pathways in various tissues including glucose-stimulated insulin secretion. In the present study, we identify promoter usage of the human PC gene in pancreatic beta cells. The data show that in the human, two alternative promoters, proximal and distal, are responsible for the production of multiple mRNA isoforms as in the rat and mouse.

Functional characterization of the proximal promoter of the murine pyruvate carboxylase gene in hepatocytes: role of multiple gc boxes.

Pyruvate carboxylase (PC) catalyzes the first committed step in gluconeogenesis in the liver. The murine PC gene possesses two promoters, the proximal (P1) and the distal (P2) which mediate production of distinct tissue-specific mRNA isoforms. By comparing the luciferase activities of 5'-nested deletions of the P1-promoter in the AML12 mouse hepatocyte cell line, the critical cis-acting elements required for maintaining basal transcription were located within the 166 nucleotides proximal to the transcription start site.

Differences between human and rodent pancreatic islets: low pyruvate carboxylase, atp citrate lyase, and pyruvate carboxylation and high glucose-stimulated acetoacetate in human pancreatic islets.

Anaplerosis, the net synthesis in mitochondria of citric acid cycle intermediates, and cataplerosis, their export to the cytosol, have been shown to be important for insulin secretion in rodent beta cells. However, human islets may be different. We observed that the enzyme activity, protein level, and relative mRNA level of the key anaplerotic enzyme pyruvate carboxylase (PC) were 80-90% lower in human pancreatic islets compared with islets of rats and mice and the rat insulinoma cell line INS-1 832/13.

Identification of the cyclic AMP responsive element (CRE) that mediates transcriptional regulation of the pyruvate carboxylase gene in HepG2 cells.

Pyruvate carboxylase (PC) catalyzes the first committed step in gluconeogenesis. Here we investigated the effect of various hormones including cAMP, dexamethasone and insulin on the abundance of PC mRNA in the human hepatocyte cell line, HepG2. Treatment of HepG2 cells with 1 microM of glucagon increased the expression of PC mRNA threefold within 72 h.