Azuma M, Motegi K, Aota K, Yamashita T, Yoshida H, Sato M
Second Department of Oral and Maxillofacial Surgery, Tokushima University School of Dentistry, 3 Kuramoto-cho, Tokushima, 770-8504, Japan.
Exp Cell Res. 1999 Jul 10;250(1):213-22. doi: 10.1006/excr.1999.4503.
Transforming growth factor (TGF)-beta is the prototype of a large superfamily of signaling molecules involved in the inhibition of proliferation of multiple epithelial cell types. Although accumulated evidence indicates the mechanisms of the antimitogenic effect of TGF-beta in a variety of cell types, the signal transduction mechanism underlying the regulation of NF-kappaB transcription factor by TGF-beta is largely unknown. Because NF-kappaB is not only involved in inflammatory responses but also mediates cell growth, we have investigated the effect of TGF-beta1 on the activity of NF-kappaB and the role of the inhibitory IkappaB-alpha protein in the growth of the human salivary gland cell clones NS-SV-AC, HSGc, and cl-1. NF-kappaB, which is usually maintained in an inactive state by protein-protein interaction with IkappaB, was found to be constitutively active in salivary gland cell lines. Upon treatment of cell clones with TGF-beta1, the NF-kappaB activity in NS-SV-AC and HSGc, but not in cl-1, which lacks the expression of TGF-beta type II receptor, was suppressed. In NS-SV-AC and HSGc, this inhibition was mediated by the induction of IkappaB-alpha at the mRNA and protein levels. The blocking of NF-kappaB subunit with a specific antisense oligonucleotide reduced the growth rate of all of the cell clones, including cl-1. Introduction of a mutated form of IkappaB-alpha cDNA into NS-SV-AC suppressed the growth rate of this cell clone. These results indicate that TGF-beta1 downregulates NF-kappaB activity through the induction of IkappaB-alpha expression in human salivary gland cells and that inhibition of NF-kappaB activity suppresses the growth rate of these cells.
转化生长因子（TGF）-β是一大类信号分子超家族的原型，这些信号分子参与抑制多种上皮细胞类型的增殖。尽管越来越多的证据表明了TGF-β在多种细胞类型中抗有丝分裂作用的机制，但TGF-β调节核因子-κB（NF-κB）转录因子的信号转导机制仍 largely未知。由于NF-κB不仅参与炎症反应，还介导细胞生长，我们研究了TGF-β1对NF-κB活性的影响以及抑制性IkappaB-α蛋白在人唾液腺细胞克隆NS-SV-AC、HSGc和cl-1生长中的作用。通常通过与IkappaB的蛋白质-蛋白质相互作用维持在无活性状态的NF-κB，在唾液腺细胞系中被发现组成性激活。用TGF-β1处理细胞克隆后，NS-SV-AC和HSGc中的NF-κB活性受到抑制，但在缺乏TGF-β II型受体表达的cl-1中未受抑制。在NS-SV-AC和HSGc中，这种抑制是由mRNA和蛋白质水平上IkappaB-α的诱导介导的。用特异性反义寡核苷酸阻断NF-κB亚基降低了所有细胞克隆（包括cl-1）的生长速率。将突变形式的IkappaB-α cDNA导入NS-SV-AC抑制了该细胞克隆的生长速率。这些结果表明，TGF-β1通过诱导人唾液腺细胞中IkappaB-α的表达下调NF-κB活性，并且抑制NF-κB活性会抑制这些细胞的生长速率。
