SNX1 regulates the resensitization of mGluR1. A, B, Western blot (A) and quantitation of the Western blots (B) showing that application of 100 μm R,S-DHPG for 5 min led to the phosphorylation of MAP kinases. Furthermore, the receptors recycled to the cell surface following normal recycling route in 2.5 h, also showed the ability to induce phosphorylation of MAP kinases on application of 100 μm R,S-DHPG for 5 min. C, D, Western blot (C) and quantitation (D) suggested that although in SNX1 knockdown cells, initial application of 100 μm R,S-DHPG for 5 min led to the phosphorylation of MAP kinases, but the receptors that recycled back in 30 min post-ligand application, following the rapid recycling route, were unable to induce the phosphorylation of MAP kinases on application of 100 μm R,S-DHPG for 5 min. E, F, Representative images (E) and quantitation of the mGluR-mediated AMPAR endocytosis (F) suggested that in control cells, the receptors that recycled back to the cell surface following normal recycling route in 2.5 h, were able to induce the endocytosis of GluA1-containing receptors when they were stimulated with 100 μm R,S-DHPG for 5 min. On the other hand, application of 100 μm R,S-DHPG did not cause endocytosis of GluA1-containing receptors when the mGluR recycling was inhibited with okadaic acid and FK-506. G, H, Representative images (G) and quantitation of the mGluR-mediated AMPAR endocytosis (H) showed that in shSNX1 transfected cells, although initial application of 100 μm R,S-DHPG for 5 min led to the endocytosis of GluA1-containing receptors, but the receptors that recycled back to the cell surface through rapid recycling route in 30 min post-ligand application, did not have the ability to induce the internalization of GluA1-containing receptors. Results are presented as mean ± SEM collected from three independent experiments. Scale bar, 10 μm. ***p < 0.001, *p < 0.05; n.s., p > 0.05.