Moss A L, Ward W F
Department of Physiology, University of Texas Health Science Center, San Antonio 78284-7756.
J Cell Physiol. 1991 Nov;149(2):313-8. doi: 10.1002/jcp.1041490219.
It has been suggested that there are multiple pathways for the cellular internalization of insulin. To investigate these pathways we have examined the effects of three perturbations of endocytosis on the insulin internalization process and have compared these effects with those obtained using an asialoglycoprotein, asialofetuin (Afet), and epidermal growth factor (EGF). Freshly isolated hepatocytes were incubated with radiolabeled ligands and internalization measured under conditions of anoxia to deplete cellular ATP, in the presence of phenylarsine oxide (PAO) to inhibit endocytosis, and in the presence of monensin to interfere with endosomal acidification. Afet internalization essentially was blocked by all three treatment processes, while insulin internalization was inhibited approximately 40% in the presence of anoxia, and 54% in the presence of PAO. Monensin exhibited differential effects on internalization of high and low insulin concentrations. The effects of the treatment processes on EGF internalization were intermediate to those seen with Afet and insulin. These results suggest that insulin and EGF utilize routes of internalization exhibiting different energy requirements that may correspond to coated pit, non-coated pit, and fluid-phase internalization pathways. The observations with Afet internalization remain consistent with utilization of the coated pit pathway.
有人提出，胰岛素的细胞内化存在多种途径。为了研究这些途径，我们检测了三种内吞作用扰动对胰岛素内化过程的影响，并将这些影响与使用去唾液酸糖蛋白、去唾液酸胎球蛋白（Afet）和表皮生长因子（EGF）所获得的影响进行了比较。将新鲜分离的肝细胞与放射性标记的配体一起孵育，并在缺氧条件下测量内化情况，以耗尽细胞内的ATP；在存在苯砷氧化物（PAO）的情况下抑制内吞作用；在存在莫能菌素的情况下干扰内体酸化。Afet的内化在所有三种处理过程中基本被阻断，而胰岛素内化在缺氧情况下约被抑制40%，在存在PAO的情况下被抑制54%。莫能菌素对高、低胰岛素浓度的内化表现出不同的影响。处理过程对EGF内化的影响介于Afet和胰岛素之间。这些结果表明，胰岛素和EGF利用了具有不同能量需求的内化途径，这些途径可能对应于有被小窝、无被小窝和液相内化途径。关于Afet内化的观察结果与有被小窝途径的利用情况仍然一致。
