Study On The Mechanism Of DUSP6 In The Degradation Of LDL Receptor By PCSK9

About 70% of human plasma cholesterol exists in the form of low-density lipoprotein(LDL).The increase of plasma low-density lipoprotein cholesterol(LDL-C)is considered to be the most important factor leading to the occurrence and development of coronary heart disease(CAD).LDL in the blood binds to the LDL receptor(LDLR)on the cell surface and enters the cell through vesicular endocytosis.In the endocytosis pathway,LDL and LDLR dissociate,LDL is transported to lysosome for degradation,and LDLR circulates to the surface of the cell membrane to perform its next function.Proprotein converting enzyme subtilisin 9(proprotein convertase subtilisin kexin type 9(PCSK9)is a liver secretory protein,and its mutation is closely related to the level of serum LDL-C.Our and other studies have found that PCSK9 directly interacts with LDLR to promote the degradation of LDLR in lysosomes,thereby regulating the level of blood LDL.Antibody inhibitors against PCSK9 have also been successfully used in clinic and achieved significant cholesterol-lowering effects.Although there is clear genetic evidence,the mechanism of PCSK9 promoting LDLR degradation is still unclear.In-depth revelation of the mechanism of PCSK9 degradation of LDLR is not only conducive to the establishment of cholesterol metabolism regulatory network,but also expected to provide theoretical guidance for the development of new PCSK9 inhibitors.In order to reveal the molecular mechanism of PCSK9 promoting LDLR degradation,the whole genome function screening was carried out by CRISPR-Cas9 technology in the early stage of the laboratory,and DUSP6 is one of the highly enriched genes.In order to further verify whether and how it regulates the activity of PCSK9,we carried out gene silencing and overexpression experiments on DUSP6 in cells,and systematically studied the role of DUSP6 in the process of LDLR degradation promoted by PCSK9.We found that DUSP6 can promote the process of LDLR degradation promoted by PCSK9,and DUSP6 itself can inhibit the expression of LDLR in hepatocytes.This discovery not only lays an important experimental foundation for revealing the mechanism of DUSP6 gene participating in the physiological process of PCSK9/LDLR,but also provides a good idea and experimental method for excavating other factors involved in the mechanism of PCSK9 degradation of LDLR.