Proprotein convertase 7 (PCSK7) reduces apoA-V levels

Yahya Ashraf, Stéphanie Duval, Vatsal Sachan, Rachid Essalmani, Delia Susan-Resiga, Anna Roubtsova, Josée Hamelin, Stefan Gerhardy, Daniel Kirchhofer, Vincent S. Tagliabracci, Annik Prat, Robert Scott Kiss, Nabil G. Seidah

Research output: Contribution to journalArticle

1 Scopus citations

Abstract

The locus of the human proprotein convertase subtilisin–kexin type-7 (PC7) gene (PCSK7) is on chromosome 11q23.3 close to the gene cluster APOA5/APOA4/APOC3/APOA1, a region implicated in the regulation of lipoprotein metabolism. A GWAS reported the association of PCSK7 SNPs with plasma triglyceride (TG), and exome sequencing of African Americans revealed the association of a low-frequency coding variant of PC7 (R504H; SNP rs142953140) with a ~ 30% TG reduction. Another PCSK7 SNP rs508487 is in linkage disequilibrium with a promoter variant of the liver-derived apolipoprotein A-V (apoA-V), an indirect activator of the lipoprotein lipase (LpL), and is associated with elevated TG levels. We thus hypothesized that PC7 regulates the levels/activity of apoA-V. Studies in the human hepatic cell line HuH7 revealed that wild-type (WT) PC7 and its endoplasmic reticulum (ER)-retained forms bind to and enhance the degradation of human apoA-V in acidic lysosomes in a nonenzymatic fashion. PC7-induced degradation of apoA-V is inhibited by bafilomycin A1 and the alkalinizing agents: chloroquine and NH4Cl. Thus, the PC7-induced apoA-V degradation implicates an ER-lysosomal communication inhibited by bafilomycin A1. In vitro, the natural R504H mutant enhances PC7 Ser505 phosphorylation at the structurally exposed Ser-X-Glu507 motif recognized by the secretory kinase Fam20C. Co-expression of the phosphomimetic PC7-S505E with apoA-V resulted in lower degradation compared to WT, suggesting that Ser505 phosphorylation of PC7 lowers TG levels via reduced apoA-V degradation. In agreement, in Pcsk7−/− mice fed high-fat diet, plasma apoA-V levels and adipocyte LpL activity are increased, providing an in vivo mechanistic link for a role of liver PC7 in enhanced TG storage in adipocytes.

Original languageEnglish (US)
Pages (from-to)3565-3578
Number of pages14
JournalFEBS Journal
Volume287
Issue number16
DOIs
StatePublished - Aug 1 2020

Keywords

  • PC7
  • PCSK7
  • apolipoprotein A-V
  • lipoprotein lipase
  • triglycerol

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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    Ashraf, Y., Duval, S., Sachan, V., Essalmani, R., Susan-Resiga, D., Roubtsova, A., Hamelin, J., Gerhardy, S., Kirchhofer, D., Tagliabracci, V. S., Prat, A., Kiss, R. S., & Seidah, N. G. (2020). Proprotein convertase 7 (PCSK7) reduces apoA-V levels. FEBS Journal, 287(16), 3565-3578. https://doi.org/10.1111/febs.15212