Figure 2. Azithromycin blocks autophagic clearance and autophagosome acidification.

(A) Azithromycin reduced basal (black) and rapamycin-induced (gray) clearance of mutant (A53T) α-synuclein in stable inducible PC12 cells. The A53T α-synuclein transgene was induced with doxycycline for 48 hours and then switched off (by antibiotic removal) before cells were treated with vehicle alone, rapamycin (200 nM), and/or azithromycin for a further 24 hours. (B) Azithromycin reduced clearance of mutant (Q74) huntingtin. Aggregates of GFP-Q74 huntingtin were reduced by rapamycin treatment, but increased when autophagy was blocked by either BafA₁ or azithromycin (4–16 μg/ml). Con, control. *P < 0.05; **P < 0.005. Scale bar: 10 μm.