Binding of enterostatin to the human neuroepithelioma cell line SK-N-MC

SK-N-MC cells were found to possess binding sites for enterostatin, a peptide with central effects on appetite and sympathetic activation of brown adipose tissue during high-fat feeding. Scatchard analyses of the binding indicated one high-affinity binding (Kd = 0.5-1.5 nM) and one low-affinity binding (Kd = 15-30 nM) for 3H-enterostatin (APGPR). 125I-YGGAPGPR showed similar binding parameters as for the low affinity binding of 3H-APGPR. Met-enkephalin and beta3-casomorphin1-5 were found to displace the binding of 3H-APGPR to the SK-N-MC cells. Affinity purification of solubilized cells revealed an APGPR-binding protein estimated to 53 kDa which may represent a distinct enterostatin receptor. Cross-linking of 125I-YGGAPGPR to intact cells labeled one major protein with the same molecular size. There was no binding of enterostatin to four other human neuroblastoma/neuroepithelioma cell lines, named IMR-92, LAN#5, NB-1 #14 and SH5-SY.