Short amyloid fibrils induce the formation of phosphorylated α-syn aggregates over passages. (A) Presence of phosphorylated α-syn aggregates in SH-SY5Y overexpressing α-syn (SH-OE, top left panel). From left to right: neuroblastoma SH-SY5Y (SH), SH-SY5Y infected with human α-syn short amylod fibrils at passage 9 (SH-SFp9), SH-SY5Y overexpressing α-syn (SH-OE) and SH-SY5Y overexpressing α-syn-infected with human α-syn short amylod fibrils at passage 9 (SH-OE-SFp9). Cells were immunolabeled with anti-α-syn antibody (green, upper panel) or anti-phospho S129 α-syn Ab59264 (green, lower panel). Scale bars, 5 μm. Arrows point at α-syn aggregates. Images are representative of at least three independent experiments. (B) High percentage of phosphorylated α-syn aggregates in SH-SY5Y α-syn-infected cells. Bar diagram showing quantification of α-syn aggregates (left) and phospho S129 α-syn aggregates (right) in SH-SY5Y α-syn cells and SH-SY5Y α-syn-infected cells. ***p < 0.001 (Student t test, n > 150 cells counted for each condition per experiment). Error bars represent the SEM.