期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2019
卷号：116
期号：32
页码：15895-15900
DOI：10.1073/pnas.1818547116
出版社：The National Academy of Sciences of the United States of America
摘要：G protein-coupled receptor (GPCR) kinases (GRKs) are responsible for initiating desensitization of activated GPCRs. GRK5 is potently inhibited by the calcium-sensing protein calmodulin (CaM), which leads to nuclear translocation of GRK5 and promotion of cardiac hypertrophy. Herein, we report the architecture of the Ca2+·CaM–GRK5 complex determined by small-angle X-ray scattering and negative-stain electron microscopy. Ca2+·CaM binds primarily to the small lobe of the kinase domain of GRK5 near elements critical for receptor interaction and membrane association, thereby inhibiting receptor phosphorylation while activating the kinase for phosphorylation of soluble substrates. To define the role of each lobe of Ca2+·CaM, we utilized the natural product malbrancheamide as a chemical probe to show that the C-terminal lobe of Ca2+·CaM regulates membrane binding while the N-terminal lobe regulates receptor phosphorylation and kinase domain activation. In cells, malbrancheamide attenuated GRK5 nuclear translocation and effectively blocked the hypertrophic response, demonstrating the utility of this natural product and its derivatives in probing Ca2+·CaM-dependent hypertrophy.
