Effect Of Angiotensin ? Type 1 Receptor And Glucagon-like Peptide 1 Receptor Intracellular Phosphorylation Code On Its Function

G protein-coupled receptors can adopt G-protein-dependent or non-G-proteindependent pathways for signal transduction in different active conformations.In recent years,more and more attention has been paid to the signaling pathways by which GPCRs recruit inhibitory proteins.Many studies have shown that the intracellular end of GPCR is the key to its recruitment of inhibitory proteins,and the site where phosphorylation can occur at the end of the cell attracts positively charged inhibitory protein molecules,which form an interaction site by electrostatic attraction.Complete GPCR recruitment of inhibitory proteins,desensitization and internalization of receptors,thereby activating downstream signaling molecules.In previous studies,it was found that there are amino acid sequences with similar order in the end of each family of GPCRs.These sequences contain three sites(serine or threonine)that can be phosphorylated,called phosphorylation codes.However,the specific role of phosphorylation codes in GPCR recruitment inhibitory proteins or other signaling pathways has not been studied.In this paper,the phosphorylation codes of angiotensin II(Ang II)type 1 receptor(AT1-R)and the phosphorylation codes of glucagon-like peptide 1 receptor(GLP-1R)were knocked separately.In addition,it was observed that when the phosphorylation code failed to complete phosphorylation,the receptor-repressed protein recruitment was completely inhibited,demonstrating that the phosphorylation code is indeed the key to receptor-collecting inhibitory proteins.Next,we performed a single-point mutation and a two-point combination of double-point mutations on the two sets of phosphorylation codes of the AT1 receptor,and found that the different mutations caused the receptor to enhance the wild-type receptor in the recruitment-inhibited egg signaling pathway.The weakening trend reveals the role of each amino acid site in the phosphorylation codon.To explore the role of phosphorylation codes in other cellular signaling pathways,we examined the signal strength of all mutant G protein dissociation pathways.After comparing the effects of mutants on the two signaling pathways,we found that when mutations at certain sites in the receptor cause one of the signaling pathways to decrease in intensity,the receptor is biased to activate another signaling pathway.These phenomena confirm the role of the phosphorylation codon for receptors in the recruitment of inhibitory proteins and G-protein-dependent signaling pathways,and reveal a new biased signal transduction pattern of receptors by intensity changes between the two signaling pathways..