Celic S, Chilco P J, Zajac J D, Martin T J, Findlay D M
St Vincent's Institute of Medical Research, Fitzroy, Victoria, Australia.
J Endocrinol. 1996 Aug;150(2):299-308. doi: 10.1677/joe.0.1500299.
We have previously shown that the response of osteoblasts to parathyroid hormone (PTH) can be influenced at the receptor level by growth on the physiological substrate, type I collagen, or by treatment with retinoic acid. We have also shown differential expression of genes when cells of the osteoblast lineage are grown on type I collagen. The aim of this study was therefore to examine the effect of retinoic acid and growth on type I collagen on PTH/PTH-related protein (PTHrP) receptor mRNA expression in the osteosarcoma osteoblast-like cell line UMR 106-06. PTH/PTHrP receptor mRNA levels, as assessed by Northern blot, of cells grown on collagen were increased up to 2-fold compared with cells on plastic and in a concentration-dependent manner with respect to collagen. An increase was seen as early as 6 h and was maintained over a 24 h period. This was not due to increased mRNA stability. Retinoic acid decreased the level of receptor mRNA on both plastic and collagen at each time but did not alter mRNA stability. For all treatments PTH/PTHrP receptor mRNA abundance, relative to glyceraldehyde-3-phosphate dehydrogenase, increased steadily over 24 h after subculture of cells. In contrast, PTHrP mRNA levels were reduced in cells on collagen, compared with plastic. PTH-stimulated cAMP levels of cells grown on collagen were increased compared with plastic at 24 h, but not earlier. Consistent with the mRNA data, retinoic acid decreased the amplitude of cAMP responses in cells on plastic and collagen. There was no evidence for changes in adenylate cyclase per se, since forskolin-induced cAMP levels did not change with either treatment. This study shows that known modulators of osteoblast maturation also affect signal transduction in these cells by regulating gene expression of the PTH/PTHrP receptor as well as the PTHrP ligand.
我们之前已经表明，成骨细胞对甲状旁腺激素（PTH）的反应在受体水平上可受到在生理底物I型胶原上生长的影响，或受到视黄酸处理的影响。我们还表明，当成骨细胞系细胞在I型胶原上生长时，基因存在差异表达。因此，本研究的目的是检测视黄酸和在I型胶原上生长对骨肉瘤成骨样细胞系UMR 106 - 06中PTH/PTH相关蛋白（PTHrP）受体mRNA表达的影响。通过Northern印迹法评估，在胶原上生长的细胞的PTH/PTHrP受体mRNA水平与在塑料上生长的细胞相比增加了2倍，并且相对于胶原呈浓度依赖性。早在6小时就观察到增加，并在24小时内保持。这不是由于mRNA稳定性增加所致。视黄酸在每次检测时均降低了在塑料和胶原上的受体mRNA水平，但未改变mRNA稳定性。对于所有处理，相对于甘油醛 - 3 - 磷酸脱氢酶，PTH/PTHrP受体mRNA丰度在细胞传代培养后24小时内稳步增加。相比之下，与在塑料上生长的细胞相比，在胶原上生长的细胞中PTHrP mRNA水平降低。在24小时时，与在塑料上生长的细胞相比，在胶原上生长的细胞经PTH刺激后的cAMP水平增加，但在更早时间无此现象。与mRNA数据一致，视黄酸降低了在塑料和胶原上生长的细胞中cAMP反应的幅度。没有证据表明腺苷酸环化酶本身发生了变化，因为佛司可林诱导的cAMP水平在两种处理下均未改变。本研究表明，已知的成骨细胞成熟调节剂还通过调节PTH/PTHrP受体以及PTHrP配体的基因表达来影响这些细胞中的信号转导。
