Cellular overexpression increases PKMζ above endogenous levels. A. Overexpression of PKMζ in primary cultures of hippocampal neurons increases PKMζ over endogenous PKMζ levels. Hippocampal neurons express endogenous PKMζ, but only trace amount of PKCζ (data not shown). Top, representative immunoblot; bottom, group data, mean ± SEM; *, p < 0.05, n = 4. B. Overexpression of PKMζ in 293T cells increases PKMζ ~40-fold over endogenous PKCζ levels (**, p < 0.01, n = 3). The 293T cells express endogenous PKCζ, but not PKMζ (data not shown).