The Study Of The Mechanism That HBO1 Complex Regulates The Function Of Mitochondrion And The Process Of Autophagy

The mitochondrion is the“power plant”of cell and plays important role in cell function.Accumulating evidence demonstrates that many metabolic enzymes in mitochondria are subjected to acetylation.Acetylation can regulate cellular metabolic activity through modulating the enzymatic stability and activity of various acetylated metabolic enzymes.Whether the acetylation of mitochondrial proteins occurs in a passive manner via unique mitochondrial pH and high concentration of acetyl coenzyme A or depending on the catalysis of acetyltransferases located in mitochondria is still controversial.So far GCN5L1 is the only acetyltransferase reported to catalyze protein acetylation in mitochondria.In this thesis we show that JADE II,a subunit in the HBO1 acetyltransferase complex,primarily locates in mitochondria.Importantly,JADE ? recruits the HBOl complex to mitochondria and thus regulates mitochondrial protein acetylation.Our findings support the concept that mitochondrial protein acetylation can be catalyzed by specific acetyltransferase.In the first place,I identified JADE II as a mitochondria-associated protein that can target the HBOl complex to mitochondria to acetylate mitochondrial proteins.Through both immunostaining and subcellular fractionation via sucrose density gradient centrifugation,we demonstrated that unlike the JADE I protein,the JADE II protein resides primarily in mitochondria.Furthermore,JADE II is capable of recruiting various subunits of the HBOl complex to mitochondria.The mitochondria located HBOl acetylates various mitochondrial proteins and inhibits ATP generation.In addition,JADE II itself is Ssubjected to acetylation by HBOl and JADE II acetylation regulates its mitochondrial localization,with acetylated JADE II being associated preferentially with mitochondria.JADE II can be deacetylated by SIRT2,which facilitates its dissociation from mitochondria.Furthermore,I found that glucose starvation and serum deprivation substantially down-regulated the JADE II-mitochondria association.These data suggest that JADE II may serve as a metabolic sensor to respond to and regulate cellular energy metabolism.Secondly,I focused on how the JADE ?-HBOl complex regulates autophagy.I found that JADE II interacts with and can target HBOl to acetylate autophagy regulatory proteins Atg5,Atg7 and Atg8 and inhibits mitophagy.As a result,the copy number of mtDNA and the levels of mitochondrial transcripts increased upon ectopic JADE II and HBOl expression.Through observation with fluorescence microscope and transmission electron microscopy,I found that JADE II overexpression caused abnormal aggregation of mitochondria and led to cell apoptosis.To further investigate the physiological role of JADE II,a Jade II knockout mouse model was generated via CRISPR-Cas9 technology.The Jade//-/-mice are viable,fertile and exhibit no obvious phenotype at regular culture condition.However,our preliminary data demonstrated an increased level of autophagy in the liver tissues from Jade II-/-mice in comparison to that of the wild-type mice.Thus,both cellular and mouse model studies elucidate a role for JADE II in control of cell autophagy.Taken all together,my thesis work has identified JADE II as a potential energy sensor that confers the HBOl complex a role in regulation of mitochondrial function and the process of autophagy.