The glucagon like peptide 1 receptor (GLP 1R) plays an important role in regulating insulin secretion and reducing body weight, making it a prominent target in the treatment of type 2 diabetes and obesity. Extensive research on GLP 1R signaling has provided insights into the connection between receptor function and physiological outcomes, such as the correlation between Gs signaling and insulin secretion, yet the exact mechanisms regulating signaling remain unclear. Here, we explore the internalization pathway of GLP 1R, which is crucial for controlling insulin release and maintaining pancreatic beta cell function. Utilizing a reliable and sensitive time resolved fluorescence resonance energy transfer (TR FRET)... More
The glucagon like peptide 1 receptor (GLP 1R) plays an important role in regulating insulin secretion and reducing body weight, making it a prominent target in the treatment of type 2 diabetes and obesity. Extensive research on GLP 1R signaling has provided insights into the connection between receptor function and physiological outcomes, such as the correlation between Gs signaling and insulin secretion, yet the exact mechanisms regulating signaling remain unclear. Here, we explore the internalization pathway of GLP 1R, which is crucial for controlling insulin release and maintaining pancreatic beta cell function. Utilizing a reliable and sensitive time resolved fluorescence resonance energy transfer (TR FRET) internalization assay, combined with HEK293 derived knockout cell lines, we were able to directly compare the involvement of different endocytic machinery in GLP 1R internalization. Our findings indicate that the receptor internalizes independently of arrestin and is dependent on Gs and Gi/o activation and G protein coupled receptor kinase phosphorylation. Mechanistically, we observed that the receptor undergoes distinct clathrin and caveolae mediated internalization in HEK293 cells. This study also investigated the role of arrestins in GLP 1R function and regulation. These insights into key endocytic components that are involved in the GLP 1R internalization pathway could enhance the rational design of GLP 1R therapeutics for type 2 diabetes and other GLP 1R related diseases.The glucagon like peptide 1 (GLP 1) receptor is regulated by distinct agonist induced and constitutive internalization pathways. Upon agonist stimulation, GLP 1 receptor activates Gs and Gi/o, then recruits G protein coupled receptor kinase 2/3/5/6 to phosphorylate the intracellular loops and C tail of the receptor. AP2 and clathrin bind directly to the receptor and direct it to clathrin coated pits. Constitutive internalization occurs via arrestin and Gs related, clathrin and caveolae mediated pathways. The activated receptor can also be internalized via caveolae mediated signaling. Created with BioRender.com .
