GPR162 is a beta cell CART receptor [INS1_GPR162]

Cocaine and amphetamine-regulated transcript (CART) is expressed in pancreatic islet cells and neuronal elements. We have previously established insulinotropic actions of CART in human and rodent islets. The receptor for CART in the pancreatic beta cells is unidentified. We used RNA sequencing of Cartpt knock down (KD) INS-1 832/13 cells and identified GPR162 as the most Cartpt-regulated receptor. We therefore tested if GPR162 mediates the effects of CART in beta cells. Binding of CART to GPR162 was established using proximity ligation assay, radioactive binding and co-immunoprecipitation, and KD of Gpr162 mRNA caused reduced binding. Gpr162 KD cells had blunted CARTp-induced exocytosis, and reduced CARTp-induced insulin secretion. Furthermore, we identified a hitherto undescribed GPR162-dependent role of CART as a regulator of cytoskeletal arrangement. Thus, our findings provide mechanistic insight into the effect of CART on insulin secretion and show that GPR162 is the CART receptor in beta cells.可卡因-苯丙胺调节转录本（Cocaine and amphetamine-regulated transcript, CART）可在胰岛细胞与神经元组分中表达。我们此前已证实CART在人类及啮齿类胰岛中具有促胰岛素作用。目前胰腺β细胞中的CART受体仍未明确。我们通过对Cartpt敲低（KD）的INS-1 832/13细胞进行RNA测序，鉴定出GPR162是受Cartpt调控最为显著的受体。因此我们验证了GPR162是否介导CART在β细胞中的作用。通过邻近连接试验、放射性结合实验以及免疫共沉淀实验，我们证实了CART与GPR162的结合，且Gpr162 mRNA的敲低会导致结合能力下降。Gpr162敲低的细胞中，CART肽诱导的胞吐作用被削弱，且CART肽诱导的胰岛素分泌水平降低。此外，我们还发现了一种此前未被报道的、依赖GPR162的CART新功能：作为细胞骨架排布的调控因子。综上，本研究结果为CART调控胰岛素分泌的作用机制提供了深入阐释，并证实GPR162即为胰腺β细胞中的CART受体。