These effects were accompanied by a decreased capacity for exendin-4 to reduce GLP-1R plasma membrane diffusion (Figure 1—figure supplement 1D, E), a behaviour observed here and previously (Manchanda et al., 2023; Pickford et al., 2020) by Raster Image Correlation Spectroscopy (RICS) in rat insulinoma INS-1 832/3 cells without endogenous GLP-1R [INS-1 832/3 GLP-1R KO cells (Naylor et al., 2016)] stably expressing SNAP/FLAG-tagged human GLP-1R (SNAP/FLAG-hGLP-1R). Here, GLP1R is linked to pancreatic insulinoma.