G Protein–Coupled Receptor Kinase-5 Attenuates Atherosclerosis by Regulating Receptor Tyrosine Kinases and 7-Transmembrane Receptors

Objective— G protein–coupled receptor kinase-5 (GRK5) is a widely expressed Ser/Thr kinase that regulates several atherogenic receptors and may activate or inhibit nuclear factor-κB (NF-κB). This study sought to determine whether and by what mechanisms GRK5 affects atherosclerosis. Methods and Results— Grk5 −/− /Apoe −/− mice developed 50% greater aortic atherosclerosis thanApoe −/− mice and demonstrated greater proliferation of macrophages and smooth muscle cells (SMCs) in atherosclerotic lesions. InApoe −/− mice, carotid interposition grafts fromGrk5 −/− mice demonstrated greater upregulation of cell adhesion molecules than grafts from wild-type mice and, subsequently, more atherosclerosis. By comparingGrk5 −/− with wild-type cells, we found that GRK5 desensitized 2 key atherogenic receptor tyrosine kinases: the platelet-derived growth factor receptor-β in SMCs, by augmenting ubiquitination/degradation; and the colony-stimulating factor-1 receptor (CSF-1R) in macrophages, by reducing CSF-1-induced tyrosyl phosphorylation. GRK5 activity in monocytes also reduced migration promoted by the 7-transmembrane receptor for monocyte chemoattractant protein-1 CC chemokine receptor-2. Whereas GRK5 diminished NF-κB-dependent gene expression in SMCs and endothelial cells, it had no effect on NF-κB activity in macrophages.Conclusion— GRK5 attenuates atherosclerosis through multiple cell type-specific mechanisms, including reduction of SMC and endothelial cell NF-κB activity and desensitization of receptor-specific signaling through the monocyte CC chemokine receptor-2, macrophage CSF-1R, and the SMC platelet-derived growth factor receptor-β.