Dynamin-related protein 1 inhibition reduces hepatic PCSK9 secretion

Cardiovasc Res. 2021 Sep 28;117(11):2340-2353. doi: 10.1093/cvr/cvab034.

Abstract

Aims: Proteostasis maintains protein homeostasis and participates in regulating critical cardiometabolic disease risk factors including proprotein convertase subtilisin/kexin type 9 (PCSK9). Endoplasmic reticulum (ER) remodeling through release and incorporation of trafficking vesicles mediates protein secretion and degradation. We hypothesized that ER remodeling that drives mitochondrial fission participates in cardiometabolic proteostasis.

Methods and results: We used in vitro and in vivo hepatocyte inhibition of a protein involved in mitochondrial fission, dynamin-related protein 1 (DRP1). Here, we show that DRP1 promotes remodeling of select ER microdomains by tethering vesicles at ER. A DRP1 inhibitor, mitochondrial division inhibitor 1 (mdivi-1) reduced ER localization of a DRP1 receptor, mitochondrial fission factor, suppressing ER remodeling-driven mitochondrial fission, autophagy, and increased mitochondrial calcium buffering and PCSK9 proteasomal degradation. DRP1 inhibition by CRISPR/Cas9 deletion or mdivi-1 alone or in combination with statin incubation in human hepatocytes and hepatocyte-specific Drp1-deficiency in mice reduced PCSK9 secretion (-78.5%). In HepG2 cells, mdivi-1 increased low-density lipoprotein receptor via c-Jun transcription and reduced PCSK9 mRNA levels via suppressed sterol regulatory binding protein-1c. Additionally, mdivi-1 reduced macrophage burden, oxidative stress, and advanced calcified atherosclerotic plaque in aortic roots of diabetic Apoe-deficient mice and inflammatory cytokine production in human macrophages.

Conclusions: We propose a novel tethering function of DRP1 beyond its established fission function, with DRP1-mediated ER remodeling likely contributing to ER constriction of mitochondria that drives mitochondrial fission. We report that DRP1-driven remodeling of select ER micro-domains may critically regulate hepatic proteostasis and identify mdivi-1 as a novel small molecule PCSK9 inhibitor.

Keywords: Cardiometabolic; DRP1; Endoplasmic reticulum; Liver; Mitochondria; PCSK9; Proteostasis.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Atherosclerosis / drug therapy*
  • Atherosclerosis / enzymology
  • Atherosclerosis / genetics
  • Atherosclerosis / pathology
  • Disease Models, Animal
  • Dynamins / antagonists & inhibitors*
  • Dynamins / genetics
  • Dynamins / metabolism
  • Endoplasmic Reticulum / drug effects*
  • Endoplasmic Reticulum / enzymology
  • Endoplasmic Reticulum / genetics
  • Endoplasmic Reticulum / pathology
  • Hep G2 Cells
  • Humans
  • Liver / drug effects*
  • Liver / enzymology
  • Liver / pathology
  • Mice
  • Mice, Knockout, ApoE
  • Mitochondria, Liver / drug effects*
  • Mitochondria, Liver / enzymology
  • Mitochondria, Liver / genetics
  • Mitochondria, Liver / pathology
  • Mitochondrial Dynamics / drug effects
  • PCSK9 Inhibitors / pharmacology*
  • Proprotein Convertase 9 / genetics
  • Proprotein Convertase 9 / metabolism*
  • Proteasome Endopeptidase Complex
  • Protein Interaction Maps
  • Proteolysis
  • Proteostasis
  • Quinazolinones / pharmacology*
  • Secretory Pathway

Substances

  • 3-(2,4-dichloro-5-methoxyphenyl)-2-sulfanyl-4(3H)-quinazolinone
  • PCSK9 Inhibitors
  • Quinazolinones
  • PCSK9 protein, human
  • Pcsk9 protein, mouse
  • Proprotein Convertase 9
  • Proteasome Endopeptidase Complex
  • DNM1L protein, human
  • Dnm1l protein, mouse
  • Dynamins