The fatty liver disease-causing protein PNPLA3-I148M alters lipid droplet-Golgi dynamics

• 成果类型: Article
• 署名作者: Sherman, David J.; Liu, Lei; Mamrosh, Jennifer L.; Xie, Jiansong; Ferbas, John; Lomenick, Brett; Ladinsky, Mark S.; Verma, Rati; Rulifson, Ingrid C.; Deshaies, Raymond J.
• 署名单位: California Institute of Technology; California Institute of Technology; United States Department of Energy (DOE); Los Alamos National Laboratory
• 刊物名称: PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
• ISSN/ISSBN: 0027-9322
• DOI: 10.1073/pnas.2318619121
• 发表日期: 2024-04-30
• 关键词: triglyceride hydrolase activity; phosphatidylinositol 4; 5-bisphosphate; endoplasmic-reticulum; apolipoprotein-b; i148m variant; high-affinity; domain; triacylglycerol; adiponutrin; expression

摘要

Nonalcoholic fatty liver disease, recently renamed metabolic dysfunction - associated steatotic liver disease (MASLD), is a progressive metabolic disorder that begins with aberrant triglyceride accumulation in the liver and can lead to cirrhosis and cancer. A common variant in the gene PNPLA3 , encoding the protein PNPLA3 - I148M, is the strongest known genetic risk factor for MASLD. Despite its discovery 20 y ago, the function of PNPLA3, and now the role of PNPLA3 - I148M, remain unclear. In this study, we sought to dissect the biogenesis of PNPLA3 and PNPLA3 - I148M and characterize changes induced by endogenous expression of the disease - causing variant. Contrary to bioinformatic predictions and prior studies with overexpressed proteins, we demonstrate here that PNPLA3 and PNPLA3 - I148M are not endoplasmic reticulum - resident transmembrane proteins. To identify their intracellular associations, we generated a paired set of isogenic human hepatoma cells expressing PNPLA3 and PNPLA3 - I148M at endogenous levels. Both proteins were enriched in lipid droplet, Golgi, and endosomal fractions. Purified PNPLA3 and PNPLA3 - I148M proteins associated with phosphoinositides commonly found in these compartments. Despite a similar fractionation pattern as the wild - type variant, PNPLA3 - I148M induced morphological changes in the Golgi apparatus, including increased lipid droplet-Golgi contact sites, which were also observed in I148M - expressing primary human patient hepatocytes. In addition to lipid droplet accumulation, PNPLA3 - I148M expression caused significant proteomic and transcriptomic changes that resembled all stages of liver disease. Cumulatively, we validate an endogenous human cellular system for investigating PNPLA3 - I148M biology and identify the Golgi apparatus as a central hub of PNPLA3 - I148M - driven cellular change.