Figure 7.

α-Syn oligomer types A1 and A2 induced intracellular [Ca²⁺] increase via influx of extracellular [Ca²⁺] sources. A, Kinetic plots illustrating typical signal responses to application of 0.1 μg/μl α-syn oligomer types A1 and A2 and positive controls, 1.5 μm ionomycin, and 500 μg/ml gramicidin in [Ca²⁺]-free extracellular buffer. Each trace shows the mean fluorescence of 6000 mock-transfected SH-SY5Y cells expressing endogenous α-syn. Intracellular [Ca²⁺] signals evoked by oligomers type A1, A2, and gramicidin were completely abolished when cells were incubated in [Ca²⁺]-free extracellular buffer, whereas ionomycin-induced [Ca²⁺] signals were persistent. B, [Ca²⁺] signals evoked by oligomer types A1 and A2 are not reduced by cobalt, a nonspecific Ca²⁺ channel blocker. Each trace shows the typical mean fluorescence of 6000 mock-transfected SH-SY5Y cells after addition of type A1 oligomers in the presence and absence of cobalt. Type A oligomers showed a clear calcium channel-independent increase in intracellular [Ca²⁺]. This experiment was repeated two times and showed similar results.