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International Journal of Experimental Diabetes Research
Volume 2 (2001), Issue 3, Pages 173-186
http://dx.doi.org/10.1155/EDR.2001.173

Substrate-induced Nuclear Export and Peripheral Compartmentalization of Hepatic Glucokinase Correlates with Glycogen Deposition

1Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, TN 37232-0615, USA
2C-349 Given Building, Department of Medicine, Division of Endocrinology, University of Vermont, Burlington, VT 05405, USA

Received 16 April 2001; Revised 11 July 2001; Accepted 20 July 2001

Copyright © 2001 Hindawi Publishing Corporation. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Hepatic glucokinase (GK) is acutely regulated by binding to its nuclear-anchored regulatory protein (GKRP). Although GK release by GKRP is tightly coupled to the rate of glycogen synthesis, the nature of this association is obscure. To gain insight into this coupling mechanism under physiological stimulating conditions in primary rat hepatocytes, we analyzed the subcellular distribution of GK and GKRP with immunofluorescence, and glycogen deposition with glycogen cytochemical fluorescence, using confocal microscopyand quantitative image analysis. Following stimulation, a fraction of the GK signal translocated from the nucleus to the cytoplasm. The reduction in the nuclear to cytoplasmic ratio of GK, an index of nuclear export, correlated with a >50% increase in glycogen cytochemical fluorescence over a 60min stimulation period. Furthermore, glycogen accumulation was initially deposited in a peripheral pattern in hepatocytes similar to that of GK. These data suggest that a compartmentalization exists of both active GK and the initial sites of glycogen deposition at the hepatocyte surface.