CHCHD2 Thr61Ile mutation impairs F1F0-ATPase assembly in in vitro and in vivo models of Parkinson's disease

Mitochondrial dysfunction is a significant pathological alte ration that occurs in Parkinson's disease(PD),and the Thr61lle(T61I)mutation in coiled-coil helix coiled-coil helix domain containing 2(CHCHD2),a crucial mitochondrial protein,has been reported to cause Parkinson's disease.FIFO-ATPase participates in the synthesis of cellular adenosine triphosphate(ATP)and plays a central role in mitochondrial energy metabolism.However,the specific roles of wild-type(WT)CHCHD2 and T611-mutant CHCHD2 in regulating F1FO-ATPase activity in Parkinson's disease,as well as whether CHCHD2 or CHCHD2 T61I affects mitochondrial function through regulating F1FO-ATPase activity,remain unclea r.Therefore,in this study,we expressed WT CHCHD2 and T61l-mutant CHCHD2 in an MPP^(+)-induced SH-SY5Y cell model of PD.We found that CHCHD2 protected mitochondria from developing MPP^(+)-induced dysfunction.Under normal conditions,ove rexpression of WT CHCHD2 promoted F1FO-ATPase assembly,while T61I-mutant CHCHD2 appeared to have lost the ability to regulate F1FO-ATPase assembly.In addition,mass spectrometry and immunoprecipitation showed that there was an interaction between CHCHD2 and F1FO-ATPase.Three weeks after transfection with AAV-CHCHD2 T61I,we intraperitoneally injected 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine into mice to establish an animal model of chronic Parkinson's disease and found that exogenous expression of the mutant protein worsened the behavioral deficits and dopaminergic neurodegeneration seen in this model.These findings suggest that WT CHCHD2 can alleviate mitochondrial dysfunction in PD by maintaining F1F0-ATPase structure and function.

Chaperone-mediated Autophagy Regulates Cell Growth by Targeting SMAD3 in Glioma

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.