PCSK9 and Its Variants: An Unbiased Global Proteomic Study to Identify Interactors and Effects on Protein Trafficking

Proprotein convertase subtilisin/kexin type 9 (PCSK9) is a secreted glycoprotein that promotes degradation of low-density lipoprotein receptors. Gain- and loss-of-function variants of PCSK9 cause hypercholesterolemia and hypocholesterolemia, respectively. Although it has been a decade since the discovery of PCSK9, its effect in terms of global protein changes and interactions still require further understanding. This study provided a global outlook at the protein changes caused by PCSK9 and its variants in human hepatic HUH7 cell line. First, a proteomics-based method for protein subcellular distribution analysis has been developed. Second, through secretome analyses, six apolipoproteins and six proteins involved in the coagulation pathway were found with >2-fold changes between wild type PCSK9 and its variants. Third, through secreted interactome analyses, a list of 159 PCSK9 interactor candidates was identified. Two interacting proteins, FASN and PSMD2, were validated and demonstrated with dynamic interacting patterns between PCSK9 and its variants