Civitelli R, Ziambaras K, Warlow P M, Lecanda F, Nelson T, Harley J, Atal N, Beyer E C, Steinberg T H
Division of Bone and Mineral Diseases, Washington University School of Medicine, St. Louis, Missouri 63110, USA.
J Cell Biochem. 1998 Jan 1;68(1):8-21. doi: 10.1002/(sici)1097-4644(19980101)68:1<8::aid-jcb2>3.0.co;2-#.
Connexin43 (Cx43) forms gap junctions that mediate intercellular communication between osteoblasts. We have examined the effects of prostaglandin E2 (PGE2) and parathyroid hormone (PTH) on gap junctional communication in the rat osteogenic sarcoma cells UMR 106-01. Incubation with either PGE2 or PTH rapidly (within 30 min) increased transfer of negatively charged dyes between UMR 106-01 cells. This stimulatory effect lasted for at least 4 h. Both PGE2 and PTH increased steady-state levels of Cx43 mRNA, but only after 2-4 h of incubation. Transfection with a Cx43 gene construct linked to luciferase showed that this effect of PTH was the result of transcriptional upregulation of Cx43 promoter. Stimulation of dye coupling and Cx43 gene transcription were reproduced by forskolin and 8Br-cAMP. Exposure to PGE2 for 30 min increased Cx43 abundance at appositional membranes in UMR 106-01, whereas total Cx43 protein levels increased only after 4-6 h of incubation with either PGE2 or PTH. Inhibition of protein synthesis by cycloheximide did not affect this early stimulation of dye coupling, but it significantly inhibited the sustained effect of PTH and forskolin on cell coupling. In summary, both PTH and PGE2, presumably through cAMP production, enhance gap junctional communication in osteoblastic cell cultures via two mechanisms: initial rapid redistribution of Cx43 to the cell membrane, and later stimulation of Cx43 gene expression. Modulation of intercellular communication represents a novel mechanism by which osteotropic factors regulate the activity of bone forming cells.
连接蛋白43（Cx43）形成间隙连接，介导成骨细胞之间的细胞间通讯。我们研究了前列腺素E2（PGE2）和甲状旁腺激素（PTH）对大鼠骨肉瘤细胞UMR 106-01中间隙连接通讯的影响。用PGE2或PTH孵育后，UMR 106-01细胞之间带负电荷染料的转移迅速（30分钟内）增加。这种刺激作用持续至少4小时。PGE2和PTH均增加了Cx43 mRNA的稳态水平，但仅在孵育2-4小时后。用与荧光素酶连接的Cx43基因构建体转染表明，PTH的这种作用是Cx43启动子转录上调的结果。福斯可林和8-溴环磷酸腺苷（8Br-cAMP）重现了对染料偶联和Cx43基因转录的刺激。用PGE2处理30分钟可增加UMR 106-01中相邻细胞膜上的Cx43丰度，而总Cx43蛋白水平仅在与PGE2或PTH孵育4-6小时后增加。放线菌酮抑制蛋白质合成并不影响这种早期对染料偶联的刺激，但它显著抑制了PTH和福斯可林对细胞偶联的持续作用。总之，PTH和PGE2可能通过产生环磷酸腺苷（cAMP），通过两种机制增强成骨细胞培养物中的间隙连接通讯：最初Cx43迅速重新分布到细胞膜，以及随后刺激Cx43基因表达。细胞间通讯的调节代表了促骨因子调节成骨细胞活性的一种新机制。
