Identification and characterization of a new binding site for angiotensin II in mouse neuroblastoma neuro-2A cells

Specific binding site for 125I-angiotensin II (Ang II), with unique pharmacological properties uncommon to the hitherto recognized receptor subtypes, was observed in mouse neuroblastoma cells (Neuro-2A). Differentiation of the cells with 100 nM PGE1 resulted in a 10-fold increase in the number of Ang II binding sites without changing the binding affinity (Kd value: 12.0 nM). 125I-Ang II binding to membranes of differentiated Neuro-2A was inhibited by unlabeled Ang II with a Ki value of 7.06 +/- 1.09 nM but not by Ang III (1 microM). Both AT1 antagonist, Dup753, and AT2 antagonist, PD123319, failed to inhibit 125I-Ang II binding at 1 microM. 125I-Ang II binding was not affected by GTP analogs such as GTP gamma S and Gpp(NH)p. These results suggest that Neuro-2A cells possess a binding site for Ang II which is different from the presently known subtypes of Ang II receptors, and that the number of the binding site is regulated by cell differentiation.