AJP - Cell Physiology, Vol 252, Issue 2 C239-C243, Copyright © 1987 by American Physiological Society
Precursors of ribose 5-phosphate suppress expression of glucose-regulated proteins in LLC-PK1 cells
G. Gstraunthaler, H. W. Harris Jr and J. S. Handler
Withdrawal of glucose from the medium bathing mammalian cells in culture
results in cessation of growth and induces the synthesis of two stress
proteins (Mr approximately 94-100 kDa and 78-80 kDa) that have been termed
glucose-regulated proteins (GRPs). In LLC-PK1 cells, proteins of the same
molecular weights, assayed by sodium dodecyl sulfate polyacrylamide gel
electrophoresis and autoradiography, are fully induced by 24 h in
glucose-free medium. The GRPs from LLC-PK1 cells cross-react with
antibodies to GRPs of nonpolar cells, confirming their identification.
Since glucose is not essential for energy production in cultured cells, but
is essential for ribose 5-phosphate and nucleotide biosynthesis (Wice et
al. J. Biol. Chem. 256: 7812-7819, 1981), we tested the effect of several
precursors of ribose 5-phosphate on the induction of GRPs. The addition of
25 mM fructose or galactose to glucose-free medium suppressed the induction
of GRPs. The pyrimidine ribonucleosides uridine and cytidine also
suppressed GRP synthesis, ribose and the purine ribonucleosides guanosine
and adenosine suppressed partially. The results, coupled with indirect
evidence in the literature, lead to the suggestion that cell ribose
5-phosphate or a related metabolite regulates the expression of GRPs.
