Rapid release of bound glucose-6-phosphate dehydrogenase by growth factors. Correlation with increased enzymatic activity.
Epidermal growth factor (EGF), a mitogen for renal proximal tubule cells, activated the hexose monophosphate (HMP) shunt in renal proximal tubule cells (Stanton, R. C., and Seifter, J. L. (1988) Am. J. Physiol. 254, C267-C271). We therefore evaluated the effect of EGF on the HMP shunt enzymes glucose 6-phosphate dehydrogenase (G6PD, the rate-limiting enzyme) and 6-phosphogluconate dehydrogenase. Rat renal cortical cells (RCC) were incubated with either EGF or platelet-derived growth factor (PDGF) and then assayed for G6PD and 6-phosphogluconate dehydrogenase activities. EGF and PDGF increased G6PD activity by 25 and 27% respectively. Although phorbol myristate acetate (PMA), ionomycin, PMA + ionomycin, and 8-bromo-cyclic AMP had no significant effect on the activity, a 5-min preincubation with PMA potentiated the activation of G6PD by PDGF. Growth factor activation of G6PD was also seen in a fibroblast and epithelial cell line. None of the agents affected 6-phosphogluconate dehydrogenase activity in the RCC or in the cell lines. Further exploration into a possible mechanism for G6PD activation revealed that growth factors caused release of G6PD from a structural element within the cell. Streptolysin O permeabilization of RCC did not cause significant release of G6PD. However, within 1 min of addition of EGF or PDGF to permeabilized cells, G6PD was released into the cell supernatant. The nonhydrolyzable analog of GTP, guanosine 5'-O-(thiotriphosphate), caused a similar release of G6PD. Preincubation with pertussis toxin or guanyl-5'-yl thiophosphate inhibited the PDGF but not the EGF effect. Although the data do not establish a definitive proof linking G6PD release and G6PD activation, these results suggest that they are related. Thus, growth factor stimulation of the HMP shunt likely occurs by a novel mechanism associated with release of bound G6PD.
Stanton
R C
RC
Renal Division, New England Deaconess Hospital, Boston, Massachusetts.
Seifter
J L
JL
Boxer
D C
DC
Zimmerman
E
E
Cantley
L C
LC
D000818:Animals; D002478:Cells, Cultured; D003513:Cycloheximide / Q000494:pharmacology; D004789:Enzyme Activation; D004815:Epidermal Growth Factor / Q000494:pharmacology*; D005954:Glucosephosphate Dehydrogenase / Q000378:metabolism*; D006150:Guanine Nucleotides / Q000494:pharmacology; D007295:Inositol Phosphates / Q000494:pharmacology; D015759:Ionomycin / Q000494:pharmacology; D007687:Kidney Tubules, Proximal / Q000201:enzymology; D008297:Male; D010427:Pentose Phosphate Pathway; D037342:Pertussis Toxin; D010734:Phosphogluconate Dehydrogenase / Q000378:metabolism; D010982:Platelet-Derived Growth Factor / Q000494:pharmacology*; D051381:Rats; D011919:Rats, Inbred Strains; D013301:Streptolysins; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D010566:Virulence Factors, Bordetella / Q000494:pharmacology
D006150:Guanine Nucleotides; D007295:Inositol Phosphates; D010982:Platelet-Derived Growth Factor; D013301:Streptolysins; D010566:Virulence Factors, Bordetella; D015759:Ionomycin; D004815:Epidermal Growth Factor; D003513:Cycloheximide; D010734:Phosphogluconate Dehydrogenase; D005954:Glucosephosphate Dehydrogenase; D037342:Pertussis Toxin; D013755:Tetradecanoylphorbol Acetate