Type beta transforming growth factor (TGF beta) regulation of alkaline phosphatase expression and other phenotype-related mRNAs in osteoblastic rat osteosarcoma cells.
TGF beta 1 from porcine platelets increased alkaline phosphatase (AP) activity in the rat osteoblastic cell line ROS 17/2.8 about three-fold. This effect was dose-dependent with an ED50 of about approximately 0.2 ng/ml and was larger during logarithmic growth than at confluence. TGF beta 1 inhibited cell growth by about 30% with similar dose dependence. Thirty min exposure to TGF beta 1 was sufficient to increase AP activity 3 days later by about two-fold but did not affect cell growth, suggesting dissociation between effects on proliferation and differentiation. The rise in AP activity started 6 h after TGF beta 1 addition and was blocked by cycloheximide and actinomycin D. TGF beta 1 also increased AP mRNA by two- to three-fold and this effect was not blocked by cycloheximide. The half-life of AP mRNA, estimated following the addition of 5,6-dichloro-1-beta-D-ribofuranosylbenzimidazole was about ten h in both control and TGF beta 1-treated cells. The mRNAs for type I procollagen and osteonectin were also increased by TGF beta 1 but fibronectin mRNA was decreased. TGF beta 2 effects on AP and cell growth were similar to those of TGF beta 1, except for lack of activity following transient exposure. At saturating concentrations, TGF beta 2 (2 ng/ml) or dexamethasone (10(-7) M), which has similar effects on these cells, did not further augment the effects of TGF beta 1 (at 2 ng/ml). Above findings suggest that TGF beta promotes osteoblastic differentiation in rat osteosarcoma cells at least in part by acting at the pretranslational level.
D000469:Alkaline Phosphatase / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D001792:Blood Platelets / Q000032:analysis; D002460:Cell Line; D003907:Dexamethasone / Q000494:pharmacology; D010006:Osteoblasts / Q000201:enzymology / Q000378:metabolism* / Q000473:pathology; D012516:Osteosarcoma / Q000201:enzymology / Q000378:metabolism* / Q000473:pathology; D010455:Peptides / Q000097:blood / Q000494:pharmacology*; D010641:Phenotype; D012333:RNA, Messenger / Q000378:metabolism*; D013552:Swine / Q000097:blood; D015291:Transforming Growth Factors
D010455:Peptides; D012333:RNA, Messenger; D015291:Transforming Growth Factors; D003907:Dexamethasone; D000469:Alkaline Phosphatase