Expression of glut1 and glut3 glucose transporters and functional
role of hexokinase in glucose regulation of insulin biosynthesis in
mouse [beta]tc3 cells.
Nagamatsu, Shinya, Yoko Nakamichi, and Hiroki Sawa.
Department of Biochemistry and Neurosurgery* Kyorin University
School of Medicine, Mitaka, Tokyo, Japan 181
APStracts 2:0090C, 1995.
We previously reported that insulin biosynthesis in mouse [beta]TC3 cells
was regulated by glucose (Endocrinology 130:748-754, 1992). In the
present study, we have examined the effect of glucose on the glucose
transporter expression and hexokinase activities, and determined the
relationship between them and glucose-stimulated insulin biosynthesis
in [beta]TC3 cells . RT-PCR and Northern blot analysis revealed that [beta]TC3
cells expressed GLUT1 and GLUT3 glucose transporter mRNAs, but not
GLUT2. The levels of GLUT1 and GLUT3 mRNAs were not affected by
glucose (0 or 11mM) over a period of 48hr. Immunoprecipitation of
metabolically labeled [beta]TC3 cells with specific antibodies against
GLUT1 or GLUT3 proteins revealed no effect of glucose on the
biosynthesis of glucose transporters. Hexokinase (low Km hexokinase)
activity from cells incubated in 11mM glucose for 48hr increased
nealy 2 fold, compared to cells maintained in 0mM glucose, although
the amount of cellular hexokinase protein detected by immunoblot
analysis was unchanged between 0 and 11mM glucose conditions.
Glucokinase (high Km hexokinase) activity, by contrast, was not
affected by glucose. Preincubation of [beta]TC3 cells with 2-deoxyglucose
to inhibit hexokinase, thereby inhibiting all glycolysis, resulted in
the decrease of glucose-stimulated insulin biosynthesis. Thus, in
mouse [beta]TC3 cells which do not express GLUT2, there is a close
relationship between hexokinase activity and glucose-stimulated
insulin biosynthesis, but not between the glucose transporter and
glucose-stimulated insulin biosynthesis.
Received 20 July 1994; accepted in final form 20 January 1995.
APS Manuscript Number C409-4.
Article publication pending Am. J. Physiol. (Cell Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 28 February 1995.