标题：Identification of Serine 348 on the Apelin Receptor as a Novel Regulatory Phosphorylation Site in Apelin-13-induced G Protein-independent Biased Signaling
作者：Chen, Xiaoyu; Bai, Bo; Tian, Yanjun; Du, Hui; Chen, Jing
作者机构：[Chen, Xiaoyu] Shandong Univ Sch Med, Dept Physiol, Jinan 250012, Shandong, Peoples R China.; [Bai, Bo; Tian, Yanjun; Chen, Jing] Jining Med Univ, I 更多
通讯作者地址：[Bai, B]Jining Med Univ, Inst Neurobiol, Jining 272067, Shandong, Peoples R China.
来源：JOURNAL OF BIOLOGICAL CHEMISTRY
摘要：Phosphorylation plays vital roles in the regulation of G protein-coupled receptor (GPCR) functions. The apelin and apelin receptor (APJ) system is involved in the regulation of cardiovascular function and central control of body homeostasis. Here, using tandem mass spectrometry, we first identified phosphorylated serine residues in the C terminus of APJ. To determine the role of phosphorylation sites in APJ-mediated G protein-dependent and -independent signaling and function, we induced a mutation in the C-terminal serine residues and examined their effects on the interaction between APJ with G protein or GRK/beta-arrestin and their downstream signaling. Mutation of serine 348 led to an elimination of both GRK and beta-arrestin recruitment to APJ induced by apelin-13. Moreover, APJ internalization and G protein-independent ERK signaling were also abolished by point mutation at senile 348. In contrast, this mutant at serine residues had no demonstrable impact on apelin-13-induced G protein activation and its intracellular signaling. These findings suggest that mutation of serine 348 resulted in inactive GRK/beta-arrestin. However, there was no change in the active G protein thus, APJ conformation was biased. These results provide important information on the molecular interplay and impact of the APJ function, which may be extrapolated to design novel drugs for cardiac hypertrophy based on this biased signal pathway.