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 th...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 ratelimiting 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-LAMP2Amediated CMA-lysosome pathway may be a promising approach in anti-cancer therapy.展开更多
基金supported by the National Key R&D Program of China(2016YFC1306601 and 2017YFC1306002)the National Natural Science Foundation of China(82071416,81870992,81870856,U1603281,81903958,81901282,and 82004459)+3 种基金the Natural Science Foundation of Guangdong Province(2020A1515010986,2019A1515011189,and 2018A030310521)a Science and Technol-ogy Planning Project of Guangdong Province(A2018315)a Tech-nology Project of Guangzhou(2018-1202-SF-0019 and 2019ZD09)and a China Postdoctoral Science Foundation Grant(2019M662873)。
文摘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 ratelimiting 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-LAMP2Amediated CMA-lysosome pathway may be a promising approach in anti-cancer therapy.
