(A) Association of unmodified α-syn and the monomeric, dimeric, and oligomeric forms resulting from nitration of α-syn with isolated lysosomes untreated (binding [B]) or previously treated with proteinase inhibitors (association: binding + uptake [A]). Input (I): one-fifth of the amount of protein added to the incubation. Blots were developed with an antibody against α-syn (unmodified protein) or one that only recognizes the nitrated forms of α-syn (nitrated samples). (B) Percentage of each protein bound (upper panel) and translocated (lower panel) inside lysosomes, calculated from the densitometric quantification of immunoblots developed with both antibodies. n = 6. (C) Effect of a 2-molar excess of GAPDH on the association of monomers, dimers, and oligomers of nitrated α-syn (N) with lysosomes. Values are expressed as percentage of inhibition of the lysosomal association of each form of α-syn. n = 4–6. (D and E) Effect of equimolar amounts of unmodified monomers (unmodif) and nitrated (N) monomers (mon), dimers (dim), and oligomers (olig) of α-syn on the degradation of [¹⁴C]GAPDH by intact (D) or broken (E) lysosomes. Values are expressed as percentage of inhibition of the degradation of GAPDH (D) or as percentage of GAPDH degradation at the end of incubation (E) and are mean + SEM of 4–5 experiments with triplicate samples. *P < 0.05; **P < 0.01.