Glucokinase (GK) plays a central role in glucose utilization by the liver and may couple the ambient glucose concentration to insulin secretion in the pancreatic beta-cell. These different functions require that GK be regulated independently in each tissue. GK activity in these two tissues is directly related to the rate of synthesis of the protein. Hepatic GK synthesis is increased by insulin and decreased by cAMP whereas glucose may regulate the beta-cell GK. Insulin increases hepatic GK transcription but similar studies have not been reported for the other effectors. There is no evidence of activity of the gene in tissues other than the liver and beta-cell, and we have evidence which shows that different promoters are used in these tissues. The studies in this proposal are designed to yield information about the hormonal regulation of the GK gene in the liver and beta cell, and about how the tissue specific expression of this gene is accomplished.
Three Specific Aims are proposed.
Aim 1 : """"""""How is the hepatic GK gene regulated?"""""""" concerns defining the cis-acting DNA elements and associated trans-acting proteins involved in basal and hormone regulated expression of GK in liver.
Aim 2 : """"""""How is the pancreatic beta-cell GK regulated"""""""" will address similar questions in these cells. In addition, we plan to compare the regulation of GK with that of the insulin gene, another beta-cell specific gene, to determine whether common DNA elements and factors are involved in their regulation.
Aim 3 : """"""""How is tissue specific regulation of the GK gene promoter accomplished"""""""" provides a complement to Aims 1 and 2.
This Aim will employ DNA transfection and transgenic techniques to address this fundamental question.
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