Interaction of Adrenal Cell Membrane Receptors with Dimers of Corticotropin Fragments and with Poly-L-Lysine

Abstract

Polycationic peptides are demonstrated to interact with the membrane receptors of the adrenal cell as judged from their effect on steroidogenesis. The corticotropin fragments ACTH_7-24 and ACTH_11-24, when covalently dimerized at their C-termini, strongly antagonize both corticotropin- and angiotensin II -induced steroidogenesis, while dimerized ACTH_1-24 behaves as a mixed agonist/antagonist. A quantitative analysis of the antagonistic potencies shows that the measured effects are consistent with the prediction that electrostatically controlled accumulation of the charged ligand at the cell surface is an important factor in the overall ligand/receptor interaction. Similar antagonizing effects of poly-L-lysine provide further support for this hypothesis.