Figure 1: Clathrin-mediated internalization of M3R induced by anti-muscarinic autoantibodies isolated from the sera of pSS patients. (A) Immunoprecipitation of M3R by clathrin in the cytosolic fraction after pre-incubation with pSS IgG as indicated times [13]. (B) Dual immunolabling of primary cultured hSMG cells with M3R (green) and clathrin (red) [13]. Prior to pSS IgG incubation, M3R was located predominantly at the cell membrane, while clathrin was in the cytosol. Incubation with control IgG had no effect on the localization of M3R and clathrin (C), but pSS IgG induced co-localization of M3R with clathrin (merged yellow color) from the membrane region (E) to the cytosol (F). (D) Internalization of M3R induced by carbachol.