Overexpression of apoE4(1–272) results in the decreased level of complex III and IV activities. Enzymatic assays of respiratory chain complexes III (A) and IV (B) from Neuro2a cells overexpressing FLAG-apoE4(1–272 or 1–299) were determined as described in the Methods. The mitochondria levels in apoE4(1–272)- and apoE4(1–299)-overexpressing cells were determined by western blot analysis using the anti-UQCRC2 and the anti-cytochrome C1 antibodies (C). Data are the mean ± SEM of nine independent experiments. * P < 0.005, ** P < 0.0005 (t-distribution test).