ATG5 and infection: To decide whether autophagy is involved in the clearance of M1 GAS strain SF370 in Hep2 cells, we constructed an autophagy-defective cell line by knocking down Atg5 (a key protein for autophagy) (22) (Fig. 1B) and found that the number of viable intracellular bacteria in Atg5-deficient cells was much higher than that in autophagy-intact cells after M1 GAS strain SF370 infection (Fig. 1C).