Affiliation:
1. Membrane Mechanisms Project, International Cooperative Research Project (ICORP), and Precursory Research for Embryonic Science and Technology (PRESTO), Japan Science and Technology Agency, Institute for Integrated Cell-Material Sciences (iCeMS), and Institute for Frontier Medical Sciences, Kyoto University, Shougoin, Kyoto 606-8507, Japan
2. Department of Cell Biology and Physiology, University of New Mexico Health Science Center, Albuquerque, NM 87131
Abstract
Receptor dimerization is important for many signaling pathways. However, the monomer–dimer equilibrium has never been fully characterized for any receptor with a 2D equilibrium constant as well as association/dissociation rate constants (termed super-quantification). Here, we determined the dynamic equilibrium for the N-formyl peptide receptor (FPR), a chemoattractant G protein–coupled receptor (GPCR), in live cells at 37°C by developing a single fluorescent-molecule imaging method. Both before and after liganding, the dimer–monomer 2D equilibrium is unchanged, giving an equilibrium constant of 3.6 copies/µm2, with a dissociation and 2D association rate constant of 11.0 s−1 and 3.1 copies/µm2s−1, respectively. At physiological expression levels of ∼2.1 receptor copies/µm2 (∼6,000 copies/cell), monomers continually convert into dimers every 150 ms, dimers dissociate into monomers in 91 ms, and at any moment, 2,500 and 3,500 receptor molecules participate in transient dimers and monomers, respectively. Not only do FPR dimers fall apart rapidly, but FPR monomers also convert into dimers very quickly.
Publisher
Rockefeller University Press
Cited by
310 articles.
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