(A) Association of unmodified and oxidized α-syn and of the S129E mutant of α-syn with isolated lysosomes untreated (binding [Bind]) or previously treated with proteinase inhibitors (association: binding + uptake [Assoc]). Lane 1 shows one-tenth of the amount of protein added to the incubation (Input). (B) Percentage of each protein bound and translocated (uptake = association – binding) inside lysosomes calculated from the densitometric quantification of 11–13 immunoblots such as the representative immunoblots shown in A. The right-hand bars show the percentage of α-syn bound to the lysosomal membrane that was translocated into lysosomes. (C) Effect of a 2-molar excess of GAPDH or ovalbumin (Ovalb) on the association of unmodified, oxidized, and S129E mutant α-syn with lysosomes. Left panel: representative immunoblot. Right panel: percentage of inhibition of the lysosomal association of each form of α-syn calculated from the densitometric quantification of 4–6 immunoblots such as those shown here. (D) Effect of adding these 3 forms of α-syn in equimolar ratio with [¹⁴C]GAPDH on the degradation of [¹⁴C]GAPDH by intact lysosomes. Values are expressed as percentage of inhibition of GAPDH degradation and are mean + SEM of 4–5 experiments with triplicate samples. *P < 0.05; **P < 0.01.