The ligand-mediated internalization of mGluR1 is Siah-1A-dependent.
A, Western blotting analyses confirming that the endogenous Siah-1A was efficiently knocked down by si-Siah-1A in primary neurons. B, representative images show that acute knockdown of endogenous Siah-1A had no effect on the surface expression of myc-mGluR1 in primary hippocampal neurons. C, quantitation of the effect of Siah-1A knockdown on the surface expression of myc-mGluR1. D, the effect of endogenous knockdown of Siah-1A on the internalization of myc-mGluR1. Representative images showing that knockdown of Siah-1A led to the inhibition of DHPG-mediated internalization of the receptor. E, quantitation also suggested that knockdown of Siah-1A resulted in the inhibition of myc-mGluR1 endocytosis. F, co-immunoprecipitation experiments suggest that knockdown of Siah-1A resulted in the inhibition of the ligand-induced increase in the ubiquitination of mGluR1. M, molecular weight markers; V, empty vector; IB, immunoblot; IP, immunoprecipitation. All the results are represented as means ± S.E., collected from three independent experiments. Scale bar, 10 μm. ***, p < 0.001; n.s, p > 0.05.