Figure 9.

BDNF stimulates MAP kinase-mediated m-calpain serine phosphorylation in HEK–TrkB cells and cortical neurons. A, HEK–TrkB cells were pretreated with vehicle or the MAP kinase inhibitor PD98059 (25 μm) for 15 min before being treated with BDNF (50 ng/ml) for 60 min. Cell lysates were processed for immunoprecipitation with m-calpain or μ-calpain antibodies, and immunoprecipitated proteins were immunoblotted with anti-m-calpain, anti-μ-calpain, or anti-phospho-serine antibodies. Levels of serine-phosphorylated m-calpain and serine phosphorylated μ-calpain were quantified, and results were expressed as percentage of control. Results are means ± SEM of four experiments. *p < 0.01 compared with control; ^†p < 0.05 compared with BDNF-treated samples. B, Cortical neurons were pretreated with vehicle or the MAP kinase inhibitor PD98059 (25 μm) for 15 min before being treated with BDNF (50 ng/ml) for 60 min. Cell lysates were processed for immunoprecipitation with m-calpain antibodies, and immunoprecipitated proteins were immunoblotted with anti-m-calpain or anti-phospho-serine antibodies. Levels of serine-phosphorylated m-calpain were quantified, and results were expressed as percentage of control. Results are means ± SEM of four experiments. *p < 0.01 compared with control; ^†p < 0.05 compared with BDNF-treated samples.