RESUMEN
Previous studies suggest that the reduction of SMAD3 (mothers against decapentaplegic homolog 3) has a great impact on tumor development, but its exact pathological function remains unclear. In this study, we found that the protein level of SMAD3 was greatly reduced in human-grade IV glioblastoma tissues, in which LAMP2A (lysosome-associated membrane protein type 2A) was significantly up-regulated. LAMP2A is a key rate-limiting protein of chaperone-mediated autophagy (CMA), a lysosome pathway of protein degradation that is activated in glioma. We carefully analyzed the amino-acid sequence of SMAD3 and found that it contained a pentapeptide motif biochemically related to KFERQ, which has been proposed to be a targeting sequence for CMA. In vitro, we confirmed that SMAD3 was degraded in either serum-free or KFERQ motif deleted condition, which was regulated by LAMP2A and interacted with HSC70 (heat shock cognate 71 kDa protein). Using isolated lysosomes, amino-acid residues 75 and 128 of SMAD3 were found to be of importance for this process, which affected the CMA pathway in which SMAD3 was involved. Similarly, down-regulating SMAD3 or up-regulating LAMP2A in cultured glioma cells enhanced their proliferation and invasion. Taken together, these results suggest that excessive activation of CMA regulates glioma cell growth by promoting the degradation of SMAD3. Therefore, targeting the SMAD3-LAMP2A-mediated CMA-lysosome pathway may be a promising approach in anti-cancer therapy.
RESUMEN
The outbreak of SARS-CoV-2 continues to pose a serious threat to human health and social and economic stability. In this study, we established an anti-coronavirus drug screening platform based on the Homogeneous Time Resolved Fluorescence (HTRF) technology and the interaction between the coronavirus S protein and its host receptor ACE2. This platform is a rapid, sensitive, specific, and high throughput system. With this platform, we screened two compound libraries of 2,864 molecules and identified three potential anti-coronavirus compounds: tannic acid (TA), TS-1276 (anthraquinone), and TS-984 (9-Methoxycanthin-6-one). Our in vitro validation experiments indicated that TS-984 strongly inhibits the interaction of the coronavirus S-protein and the human cell ACE2 receptor. This data suggests that TS-984 is a potent blocker of the interaction between the S-protein and ACE2, which might have the potential to be developed into an effective anti-coronavirus drug. SIGNIFICANCEThe ongoing pandemic of COVID-19 caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has made a serious threat to public health worldwide. Given the urgency of the situation, researchers are attempting to repurpose existing drugs for treating COVID-19. In this present study, we screened two compound libraries of 2,864 molecules and identified a potent inhibitor (TS-984) for blocking the coronavirus S-protein and the human cell ACE2 receptor. TS-984 might have the potential to be developed into an effective anti-coronavirus drug for treating COVID-19.
