Constitutively active mutants of the β1‐adrenergic receptor

Abstract
We provide the first evidence that point mutations can constitutively activate the β1‐adrenergic receptor (AR). Leucine 322 of the β1‐AR in the C‐terminal portion of its third intracellular loop was replaced with seven amino acids (I, T, E, F, C, A and K) differing in their physico‐chemical properties. The β1‐AR mutants expressed in HEK‐293 cells displayed various levels of constitutive activity which could be partially inhibited by some beta‐blockers. The results of this study might have interesting implications for future studies aiming at elucidating the activation process of the β1‐AR as well as the mechanism of action of beta‐blockers.