FITC-agonist was added for 30 min at 37 C to induce internalization, then removed and washed with cold HBSS to arrest further endocytosis, and cells treated with 500 mM ice-cold sodium 2-sulfanylethanesulfonate (MesNa), a membrane-impermeable reducing agent, in alkaline TNE buffer (100 mM NaCl, 50 mM Tris-HCl, pH 8.6) to cleave BG-SS-biotin specifically from cell surface receptors
Incretin-based multi-agonists, such as tirzepatide and retatrutide, target two or more receptors among GLP-1, GIP, and GCGR to enhance insulin secretion, improve fat metabolism, and increase energy expenditureultimately achieving greater weight loss and metabolic improvement
To create viable therapeutics, researchers had to engineer GLP-1 analogs that resist enzymatic breakdown and persist long enough to exert physiological effects
The EM structure of Tirzepatide bound to the complete GLP-1R and G-proteins (Figure 2, PDB ID 7rgp , Sun et al., 2022) shows some hydrophobic and some specific polar interactions between the peptidic drug and the GLP-1 receptor molecule
