Both PDGFR-β and PDGFR-α mediate the neuroprotective effect of PDGF-CC. (A) PDGFR-α and PDGFR-β were expressed in the retina, with the PDGFR-β expression level being more abundant as measured by real-time PCR. (B) Real-time PCR detected PDGFR-α and PDGFR-β expression at a similar level in primary cortical neurons. PDGF-CC protein up-regulated their expression. (C and D) Immunoprecipitation followed by immunoblotting (antiphosphotyrosine antibody [anti-pTyr]) detected PDGFR-β (C) and PDGFR-α (D) activation by PDGF-CC in RGC5 cells, primary cortical neurons, and SN using total PDGFR-α/β as controls (anti–tPDGFR-α/β). (E) Immunofluorescent staining using antibodies against phosphorylated PDGFR-β and PDGFR-α detected activated PDGFR-β and PDGFR-α (green) mainly in the RGC layer in the retina after PDGF-CC treatment. Bar, 50 µm. (F) PDGF-CC treatment inhibited expression of several proapoptotic genes in cortical neurons. The effect of PDGF-CC was largely abolished by both PDGFR-β and PDGFR-α neutralizing antibodies (n = 6 mice). (G) PDGF-CC treatment up-regulated the expression of many neurotrophic/survival genes in cortical neurons. This effect of PDGF-CC was abolished by both PDGFR-β and PDGFR-α neutralizing antibodies (n = 6 mice). (H and I) In the ONC model, both PDGFR-α and PDGFR-β neutralizing antibodies abolished the survival effect of PDGF-CC on RGCs (white; n = 8 eyes). Bar, 20 µm. *, P < 0.05; **, P < 0.01; ***, P < 0.001. The data are represented as means ± SEM of the number of determinations. All experiments were repeated independently once (A, B, and E–G) or twice (C, D, H, and I) with similar results. Representative images (C–E and I) and experiments are shown. IB, immunoblotting; IP, immunoprecipitation; IPL, inner plexiform layer; IS/OS, inner/outer segment; nab, neutralizing antibody.