Changing expression of GTPase activating proteins with differentiation in neuroblastoma.
p21ras is a membrane-associated guanine nucleotide-binding protein with intrinsic GTPase activity. Like other guanine nucleotide-binding proteins p21ras is active when GTP bound and inactive when GDP bound. Phosphorylation of p21ras is regulated by the GTPase activity of type I GAP120 and NF1-GRD. In this study we have identified type I GAP120 and two NF1-GRD mRNAs in three neuroblastoma cell lines, IMR-32, SK-N-SH and SK-N-MC. NF1-GRD mRNA was expressed in all cell lines at a similar level but type I GAP120 mRNA was more abundant in the IMR-32 cell line. Retinoic acid induced differentiation of all three cell lines, this effect was most marked in the SK-N-SH line. This differentiation was accompanied by an increase in both type I GAP120 and NF1-GRD mRNAs. Retinoic acid induced differentiation had no effect on the ratio of type I to type II NF1-GRD mRNA. In seven patient tumour samples examined type I GAP120 and NF1-GRD were coexpressed, type I GAP120 at a higher level than NF1-GRD in all tumour stages. Type I was the predominant NF1-GRD mRNA. The expression of type I GAP120 was similar in all tumour stages but the total level of NF1-GRD was higher in stage 2 and 3 tumours than in stage 4 tumours. In summary, these results suggest increased type I GAP120 and NF1-GRD mRNA are associated with differentiation in neuroblastoma cells.
Candlelighters Children's Research Laboratory, St. James University Hospital, Leeds, UK.
S A
SA
Burchill
P A
PA
Berry
I J
IJ
Lewis
D001483:Base Sequence; D002454:Cell Differentiation; D020690:GTPase-Activating Proteins; D006801:Humans; D007223:Infant; D015335:Molecular Probes / Q000235:genetics; D008969:Molecular Sequence Data; D009367:Neoplasm Staging; D009447:Neuroblastoma / Q000378:metabolism* / Q000473:pathology; D016133:Polymerase Chain Reaction; D011506:Proteins / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D014158:Transcription, Genetic; D014212:Tretinoin / Q000494:pharmacology; D014407:Tumor Cells, Cultured / Q000187:drug effects
D020690:GTPase-Activating Proteins; D015335:Molecular Probes; D011506:Proteins; D012333:RNA, Messenger; D014212:Tretinoin