Fig. 7: RACK1 competes with β-catenin for binding to the Armadillo-like helical domain of PSMD2.

A, B Molecular docking analysis of the binding pattern of RACK1 to PSMD2 (A) or β-catenin to PSMD2 (B). The protein backbone is rendered in tube and colored in green (β-catenin or RACK1) and red (PSMD2). The target proteins RACK1 (PDB ID: 4AOW), β-catenin (PDB ID: 7AR4) and PSMD2 (PDB ID:6MSD) were obtained from the RCSB database (https://www.rcsb.org/). C Schematic representation of HA-tagged full-length PSMD2 and its fragments containing different domains. D Co-IP analysis of the interaction pattern between RACK1 and the indicated PSMD2 mutants. HEK-293T cells were cotransfected with RACK-Flag and PSMD-HA or its mutants, then cell lysates were immunoprecipitated with anti-Flag antibodies and analyzed by Western blotting using anti-HA or Flag antibodies. E Co-IP analysis of the interaction pattern between β-catenin and the indicated PSMD2 mutants. HEK-293T cells were cotransfected with β-catenin-myc and PSMD-HA or its mutants, then cell lysates were immunoprecipitated with anti-myc antibodies and analyzed by Western blotting using anti-HA or myc antibodies. F Co-IP analysis of the interaction pattern between endogenous β-catenin and PSMD2 in the presence of elevated RACK1 expression. HEK-293T cells were transfected with increasing amounts of RACK1 plasmids, and the cell lysates were subjected to Co-IP with anti-PSMD2 antibodies and then analyzed with anti-PSMD2, RACK1 and β-catenin antibodies. G Co-IP analysis of the interaction pattern between exogenous β-catenin and PSMD2 in the presence of elevated RACK1 expression. H Knockdown of β-catenin increased the interaction between PSMD2 and RACK1 in MDA-231 cells. The protein levels of the IP products were quantified by gray scale analysis and the results are shown below the bands (F-H). All data are expressed as the mean ± SD; *p < 0.05 and ns p > 0.05 versus control, N = 3. I Diagram showing that RACK1 competes with β-catenin to bind PSMD2.