Volume 272, Number 38,
Issue of September 19, 1997
pp. 23703-23706
©1997 by The American Society for Biochemistry and Molecular Biology, Inc.
Glucose Increases Both the Plasma Membrane Number and
Phosphorylation of Insulin-like Growth Factor II/Mannose
6-Phosphate Receptors
(Received for publication, July 8, 1997)
Qimin
Zhang
,
Per-Olof
Berggren
and
Michael
Tally
From the Department of Molecular Medicine, Endocrine and Diabetes
Unit, the Rolf Luft Center for Diabetes Research, Karolinska Institute,
S-171 76, Stockholm, Sweden
We have investigated the effect of glucose on
insulin-like growth factor II (IGF-II) binding to, and intracellular
phosphorylation of, the IGF-II/mannose 6-phosphate (M6P) receptor in
the insulin-secreting cell line RINm5F. Glucose, at a concentration of
3 mM, significantly increased binding of IGF-II to
the cells. A further increase of the binding was observed at a glucose
concentration of 10 mM. Scatchard analysis showed that the
increased binding was caused by an increased number of the receptors
rather than changes in affinity. This effect of glucose was also
demonstrated in another insulin-secreting cell line HIT as well as in
the human erythroleukemia cell line K562. Affinity cross-linking of the
RINm5F cells, using 125I-IGF-II, revealed increased binding
to the IGF-II/M6P receptor induced by glucose. The effect of glucose on
IGF-II binding was mimicked by fructose (10 mM), but not by
3-O-methylglucose (10 mM), and was abolished by
the protein kinase C (PKC) inhibitor calphostin C, or down-regulation
of PKC, but not by the protein phosphatase inhibitor, okadaic acid.
Glucose dose dependently stimulated phosphorylation of the IGF-II/M6P
receptor, an effect that was inhibited by down-regulation of PKC
activity. This study suggests that the distribution of the IGF-II/M6P
receptor in insulin-secreting cells can be regulated by glucose-induced
phosphorylation, a mechanism mediated by PKC.