Chan S D, Strewler G J, King K L, Nissenson R A
Endocrine Unit, Veterans Administration Medical Center, San Francisco, California.
Mol Endocrinol. 1990 Apr;4(4):638-46. doi: 10.1210/mend-4-4-638.
Differentiation of mouse embryonal carcinoma cells to the parietal endoderm phenotype is associated with expression of PTH-responsive adenylate cyclase. A PTH-like protein (PLP), which binds to PTH receptors and activates adenylate cyclase in classical PTH target cells was recently isolated and cloned. We assessed whether the parietal endoderm phenotype is associated with the expression of PLP or its receptor. A 1.4-kilobase PLP transcript was detected in the mouse parietal endoderm cell line PYS-2. No hybridizing transcripts were evident in undifferentiated mouse embryonal carcinoma cells PSA-1 or F9. However, differentiation of these cells to parietal endoderm, either spontaneously (PSA-1) or by treatment with retinoic acid and dibutyryl cAMP (F9), resulted in expression of the 1.4-kilobase PLP message. Undifferentiated F9 cells displayed negligible specific binding of [125I]PLP-(1-34)amide. When F9 cells were induced to differentiate to parietal endoderm, specific binding sites for [125I]PLP-(1-34)amide were expressed in parallel with PLP-responsive adenylate cyclase. These receptors, like those in classical PTH target tissues, displayed identical affinity (Kd = 5.2 nM) for bPTH-(1-34) and hPLP-(1-34)amide; with binding capacity (Bmax) of 6.6 x 10(4) sites/cell. In the presence of retinoic acid, exogenous PLP substituted for dibutyryl cAMP in a concentration-dependent fashion in promoting the differentiation of F9 cells to parietal endoderm. Thus, both PLP mRNA and PLP receptors coupled to adenylate cyclase are expressed during the differentiation of mouse embryonal carcinoma cells. Increased cAMP levels produced by autocrine stimulation of PLP receptors by PLP may contribute to differentiation of embryonal carcinoma cells into parietal endoderm.
小鼠胚胎癌细胞向滋养层内胚层表型的分化与甲状旁腺激素（PTH）反应性腺苷酸环化酶的表达相关。最近分离并克隆出一种与PTH受体结合并在经典PTH靶细胞中激活腺苷酸环化酶的类PTH蛋白（PLP）。我们评估了滋养层内胚层表型是否与PLP或其受体的表达相关。在小鼠滋养层内胚层细胞系PYS - 2中检测到一个1.4千碱基的PLP转录本。在未分化的小鼠胚胎癌细胞PSA - 1或F9中未发现明显的杂交转录本。然而，这些细胞自发地（PSA - 1）或通过视黄酸和二丁酰环磷腺苷（dbcAMP）处理（F9）向滋养层内胚层分化，导致了1.4千碱基PLP信息的表达。未分化的F9细胞对[125I]PLP - (1 - 34)酰胺的特异性结合可忽略不计。当F9细胞被诱导分化为滋养层内胚层时，[125I]PLP - (1 - 34)酰胺的特异性结合位点与PLP反应性腺苷酸环化酶平行表达。这些受体与经典PTH靶组织中的受体一样，对bPTH - (1 - 34)和hPLP - (1 - 34)酰胺表现出相同的亲和力（Kd = 5.2 nM）；结合容量（Bmax）为6.6×10(4)个位点/细胞。在视黄酸存在的情况下，外源性PLP以浓度依赖的方式替代二丁酰环磷腺苷，促进F9细胞向滋养层内胚层分化。因此，在小鼠胚胎癌细胞分化过程中，PLP mRNA和与腺苷酸环化酶偶联的PLP受体均有表达。PLP通过自分泌刺激PLP受体产生的cAMP水平升高可能有助于胚胎癌细胞分化为滋养层内胚层。
