Identification of a small chemical as a lysosomal calcium mobilizer and characterization of its ability to inhibit autophagy and viral infection.

We previously identified GAPDH as one of the cyclic adenosine diphosphoribose (cADPR)'s binding proteins and found that GAPDH participates in cADPR-mediated Ca 2+ release from ER via ryanodine receptors (RyRs). Here we aimed to chemically synthesize and pharmacologically characterize novel cADPR analogues. Based on the simulated cADPR-GAPDH complex structure, we performed the structure-based drug screening, identified several small chemicals with high docking scores to cADPR's binding pocket in GAPDH, and showed that two of these compounds, C244 and C346, are potential cADPR antagonists. We further synthesized several analogs of C346, and found that its analog, G42, also mobilized Ca 2+ release from lysosomes. G42 alkalized lysosomal pH, and inhibited autophagosome-lysosome fusion. Moreover, G42 markedly inhibited Zika virus (ZIKV, a flavivirus) or murine hepatitis virus (MHV, a β-coronavirus) infections of host cells. These results suggest that G42 inhibits virus infection, likely by triggering lysosomal Ca 2+ mobilization and inhibiting autophagy.