A, phosphorylation of ATM after treatment of primary cortical neurons with Aβ1-42 or etoposide. Primary cortical neurons were treated for 1 h with 10 μM Aβ1-42 or with 1 μM etoposide (Etop). The cells were lysed, and the protein expression levels of pATM, ATM, and actin were determined by Western blot analysis using the anti-pATM, anti-ATM, and anti-actin antibodies. B, ATBF1 interacts with pATM after treatment with Aβ1-42 or etoposide. Cultured cortical neurons were treated as described in A, cell lysates were immunoprecipitated with the anti-ATBF1 antibody. The immunoprecipitated complex was then subjected to immunoblotting with the anti-pATM at Ser1891 antibody. Typical bands representative of three independent experiments with similar results are shown.