Functional Rescue of β1-Adrenoceptor Dimerization and Trafficking by Pharmacological Chaperones

Authors

  • Hiroyuki Kobayashi,

    1. Département de Biochimie, Groupe de Recherche Universitaire sur le Médicament and Institut de recherche en Immunologie et en Cancérologie, Université de Montréal, Montréal, Québec, H3C 3 J7 Canada
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  • Koji Ogawa,

    1. Département de Biochimie, Groupe de Recherche Universitaire sur le Médicament and Institut de recherche en Immunologie et en Cancérologie, Université de Montréal, Montréal, Québec, H3C 3 J7 Canada
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  • Rong Yao,

    1. Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA
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  • Olivier Lichtarge,

    1. Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA
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  • Michel Bouvier

    Corresponding author
    1. Département de Biochimie, Groupe de Recherche Universitaire sur le Médicament and Institut de recherche en Immunologie et en Cancérologie, Université de Montréal, Montréal, Québec, H3C 3 J7 Canada
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Michel Bouvier, michel.bouvier@umontreal.ca

Abstract

Site-directed mutagenesis guided by evolutionary trace analysis revealed that substitution of V179 and W183 within a cluster of evolutionarily important residues on the surface of the fourth transmembrane domain of the β1-adrenergic receptor (β1AR) significantly reduced the propensity of the receptor to self-assemble into homodimers as assessed by bioluminescence resonance energy transfer in living cells. These results suggest that mutation of V179 and W183 result in conformational changes that reduce homodimerization either directly by interfering with the dimerization interface or indirectly by causing local misfolding that result in reduced self-assembly. However, the mutations did not cause a general misfolding of the β1AR as they did not prevent heterodimerization with the β2AR. The homodimerization-compromised mutants were significantly retained in the endoplasmic reticulum (ER) and could not be properly matured and trafficked to the cell surface. Lipophilic β-adrenergic ligands acted as pharmacological chaperones by restoring both dimerization and plasma membrane trafficking of the ER-retained dimerization-compromised β1AR mutants. These results clearly indicate that homodimerization occurs early in the biosynthetic process in the ER and that pharmacological chaperones can promote both dimerization and cell surface targeting, most likely by stabilizing receptor conformations compatible with the two processes.

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