Figure 2.

Verification of the endogenous interactome of GRP78 in the PM compartment of OECM1 and FaDu cells by immunoprecipitation and western blot analysis. (A) PM and non-PM fractionations were examined by western blot analysis using two membrane markers and one cytosolic marker. The input control for co-immunoprecipitation of GRP78 was also examined with 2 amounts of protein loading. A total of nine GRP78 interactome candidates from the PM compartment were chosen for verification with co-immunoprecipitation and western blot analysis. (B) Three interactome candidates co-immunoprecipitated with cell surface GRP78 in OECM cells, and (C) six in FaDu cells. (D) Progranulin also co-immunoprecipitated with cell surface GRP78 in BM2 and NPC076 cells. Protein bands of all of the blots were quantified using ImageJ software. The expression level of GRXCR2 in FaDu cells (C) was determined by quantifying potential isoform bands pointed by three solid arrows. The bar graphs in (B) and (C) were the mean ± SEM quantified from 3 Western Blots of 3 independent co-immunoprecipitation experiments, and that in (D) 3 Western Blots of 2 independent experiments. Full-length blots are presented in Supplementary Figures S5–S8. *p < 0.1, **p < 0.05, and ***p < 0.01; NS = not significant.