Lamphere L, Lienhard G E
Department of Biochemistry, Dartmouth Medical School, Hanover, New Hampshire 03755-3844.
Endocrinology. 1992 Nov;131(5):2196-202. doi: 10.1210/endo.131.5.1385098.
To survey and compare the signaling pathways from the insulin and insulin-like growth factor-I (IGF-I) receptors in undifferentiated and differentiated muscle cells, we examined the phosphotyrosine (Ptyr)-containing polypeptides elicited in L6 and Sol8 myoblasts and myotubes by the combination of insulin and IGF-I. These polypeptides were detected by immunoblotting with antibodies against Ptyr. In the L6 myoblasts and myotubes and the Sol8 myoblasts, Ptyr polypeptides of approximately 240, 175, 115, 100, 41, and 37 kilodaltons (kDa) appeared in response to insulin-IGF-I. With the Sol8 myotubes, the 240-, 175-, and 37-kDa Ptyr polypeptides were detected in basal cells, and only the Ptyr content of the 175-kDa one increased in response to insulin-IGF-I. The polypeptides of 175, 41, and 37 kDa were tentatively identified as the insulin receptor substrate 1 (IRS1) and extracellular signal-regulated kinases 1 and 2 (ERK1 and -2), respectively, by immunoblotting with antibodies specific for these proteins, and the 115- and 100-kDa polypeptides are probably the beta-subunits of the insulin and IGF-I receptors. The amounts of IRS1, ERK1, and ERK2 were roughly the same in the L6 and Sol8 myoblasts and myotubes. Thus, differentiation of the myoblasts to myotubes was not accompanied by the detectable appearance of new insulin-IGF-I-elicited Ptyr polypeptides or marked changes in the amounts of known participants in their signaling pathways.
为了研究和比较未分化及分化的肌肉细胞中胰岛素和胰岛素样生长因子-I（IGF-I）受体的信号通路，我们检测了胰岛素和IGF-I共同作用下L6和Sol8成肌细胞及肌管中产生的含磷酸酪氨酸（Ptyr）的多肽。这些多肽通过用抗Ptyr抗体进行免疫印迹检测。在L6成肌细胞和肌管以及Sol8成肌细胞中，胰岛素-IGF-I刺激后出现了大约240、175、115、100、41和37千道尔顿（kDa）的Ptyr多肽。在Sol8肌管中，基础细胞中可检测到240 kDa、175 kDa和37 kDa的Ptyr多肽，而只有175 kDa的Ptyr含量在胰岛素-IGF-I刺激下增加。通过用针对这些蛋白质的特异性抗体进行免疫印迹，初步鉴定175 kDa、41 kDa和37 kDa的多肽分别为胰岛素受体底物1（IRS1）和细胞外信号调节激酶1和2（ERK1和ERK2），115 kDa和100 kDa的多肽可能是胰岛素和IGF-I受体的β亚基。L6和Sol8成肌细胞及肌管中IRS1、ERK%和ERK2的含量大致相同。因此，成肌细胞向肌管的分化并未伴随着新的胰岛素-IGF-I诱导的Ptyr多肽的可检测出现，也未伴随着其信号通路中已知参与成分含量的显著变化。
