TY - JOUR
T1 - Multiple pathways for ligand internalization in rat hepatocytes I
T2 - Effects of anoxia, phenylarsine oxide and monensin
AU - Moss, Anita L.
AU - Ward, Walter F.
PY - 1991/11
Y1 - 1991/11
N2 - 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.
AB - 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.
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U2 - 10.1002/jcp.1041490219
DO - 10.1002/jcp.1041490219
M3 - Article
C2 - 1721073
AN - SCOPUS:0025951261
VL - 149
SP - 313
EP - 318
JO - Journal of Cellular Physiology
JF - Journal of Cellular Physiology
SN - 0021-9541
IS - 2
ER -