Bishop R, Martinez R, Weber M J, Blackshear P J, Beatty S, Lim R, Herschman H R
Mol Cell Biol. 1985 Sep;5(9):2231-7. doi: 10.1128/mcb.5.9.2231-2237.1985.
The 3T3-TNR9 cell line is a variant of Swiss 3T3 cells which does not respond mitogenically to tumor promoters, but does respond mitogenically to epidermal growth factor, fibroblast growth factor, and serum. To elucidate differences between tumor promoters and polypeptide mitogens in the pathway(s) of mitogenesis which might be responsible for the nonresponsiveness of the 3T3-TNR9 cells, we have examined in these cells the early protein phosphorylation events known to be associated with mitogenesis in the parental 3T3 cells. We find that the 3T3-TNR9 cells display levels of tetradecanoyl phorbol acetate binding and of a calcium- and phospholipid-dependent protein kinase activity which are at least the equal of those seen in the parental 3T3 cells, implicating some postreceptor event in the nonmitogenic phenotype. In addition, we find that phosphorylation of the epidermal growth factor receptor and of 80-kDa and 22-kDa proteins, as well as the tyrosine phosphorylation of a 42-kDa protein, all proceed normally in the nonmitogenic variant, even though these phosphorylations must depend on the activation of different kinases. Thus, all these early phosphorylation reactions are intact in the 3T3-TNR9 cells. Although these phosphorylations may be necessary, they clearly are insufficient to trigger mitogenesis.
3T3-TNR9细胞系是瑞士3T3细胞的一个变体，它对肿瘤启动子无促有丝分裂反应，但对表皮生长因子、成纤维细胞生长因子和血清有促有丝分裂反应。为了阐明在有丝分裂途径中肿瘤启动子和多肽有丝分裂原之间的差异，这些差异可能是3T3-TNR9细胞无反应性的原因，我们在这些细胞中研究了已知与亲代3T3细胞有丝分裂相关的早期蛋白质磷酸化事件。我们发现，3T3-TNR9细胞显示出十四烷酰佛波醇乙酸酯结合水平以及钙和磷脂依赖性蛋白激酶活性，这些水平至少与亲代3T3细胞中所见的水平相当，这表明在非促有丝分裂表型中存在一些受体后事件。此外，我们发现表皮生长因子受体、80 kDa和22 kDa蛋白质的磷酸化，以及42 kDa蛋白质的酪氨酸磷酸化，在非促有丝分裂变体中均正常进行，尽管这些磷酸化必须依赖于不同激酶的激活。因此，所有这些早期磷酸化反应在3T3-TNR9细胞中都是完整的。虽然这些磷酸化可能是必要的，但显然不足以触发有丝分裂。
