Shi D L, Savona C, Chambaz E M, Feige J J
Unité INSERM 244, Centre d'Etudes Nucléaires, Grenole, France.
J Cell Physiol. 1990 Oct;145(1):60-8. doi: 10.1002/jcp.1041450110.
We reported previously that transforming growth factor beta (TGF-beta) does not influence the proliferation of bovine adrenocortical cells but is a very potent inhibitor of their steroidogenic functions (Feige et al.: Journal of Biological Chemistry 262:13491-13495, 1987). In the present study, we addressed the question of whether these cells modify the synthesis of their extracellular matrix (in particular of fibronectin) in response to TGF-beta 1, similarly to the changes observed in cell types whose growth is modified by this factor (e.g., fibroblasts). Immunofluorescence studies using anti-fibronectin antibodies revealed that TGF-beta 1 treatment in serum-free medium induced the formation of fibronectin-containing fibrils associated with adrenocortical cells. Metabolic labeling of adrenocortical cells with [35S]-methionine showed that fibronectin synthesis and secretion were highly stimulated by low concentrations of TGF-beta 1. Half-maximal stimulation was observed for TGF-beta 1 concentrations in the range of 0.1 to 0.5 ng/ml and maximal stimulation reached 35-fold over control at the concentration of 2 ng/ml. The earlier detectable effect was observed after 8 h of treatment (6-fold stimulation) and the maximal increase was reached after 24 h of treatment. Stimulation of adrenocortical fibronectin synthesis by TGF-beta 1 appeared to imply a transcriptional event since it was no longer observed in the presence of DRB, a potent inhibitor of RNA polymerases, and because the level of fibronectin mRNA was stimulated under TGF-beta 1 treatment. Taken together, these results indicate that the increased expression of fibronectin is not closely related to growth-regulatory effects of TGF-beta 1 since it is also observed in adrenocortical cells, whose proliferation is unaffected by TGF-beta 1.
我们之前报道过，转化生长因子β（TGF-β）不影响牛肾上腺皮质细胞的增殖，但却是其类固醇生成功能的强效抑制剂（费格等人：《生物化学杂志》262:13491 - 13495，1987）。在本研究中，我们探讨了这些细胞是否会像在生长受该因子影响的细胞类型（如成纤维细胞）中观察到的变化那样，响应TGF-β1而改变其细胞外基质（特别是纤连蛋白）的合成。使用抗纤连蛋白抗体的免疫荧光研究表明，在无血清培养基中用TGF-β1处理可诱导与肾上腺皮质细胞相关的含纤连蛋白的纤维形成。用[35S] - 甲硫氨酸对肾上腺皮质细胞进行代谢标记显示，低浓度的TGF-β1能高度刺激纤连蛋白的合成和分泌。在TGF-β1浓度为0.1至0.5 ng/ml范围内观察到半数最大刺激，在2 ng/ml浓度时最大刺激比对照高35倍。在处理8小时后观察到最早可检测到的效应（刺激6倍），处理24小时后达到最大增加。TGF-β1对肾上腺皮质纤连蛋白合成的刺激似乎意味着一个转录事件，因为在存在RNA聚合酶的强效抑制剂DRB时不再观察到这种刺激，并且因为在TGF-β1处理下纤连蛋白mRNA水平受到刺激。综上所述，这些结果表明纤连蛋白表达的增加与TGF-β1的生长调节作用没有密切关系，因为在肾上腺皮质细胞中也观察到了这种增加，而肾上腺皮质细胞的增殖不受TGF-β1的影响。
