title: PNPLA3 mediates hepatocyte triacylglycerol remodeling.
abstract: The I148M substitution in patatin-like phospholipase domain containing 3 (PNPLA3(I148M)) determines a genetic form of nonalcoholic fatty liver disease. To elucidate the mode of PNPLA3 action in human hepatocytes, we studied effects of WT PNPLA3 (PNPLA3(WT)) and PNPLA3(I148M) on HuH7 cell lipidome after [(13)C]glycerol labeling, cellular turnover of oleic acid labeled with 17 deuterium atoms ([D17]oleic acid) in triacylglycerols (TAGs), and subcellular distribution of the protein variants. PNPLA3(I148M) induced a net accumulation of unlabeled TAGs, but not newly synthesized total [(13)C]TAGs. Principal component analysis (PCA) revealed that both PNPLA3(WT) and PNPLA3(I148M) induced a relative enrichment of TAGs with saturated FAs or MUFAs, with concurrent enrichment of polyunsaturated phosphatidylcholines. PNPLA3(WT) associated in PCA with newly synthesized [(13)C]TAGs, particularly 52:1 and 50:1, while PNPLA3(I148M) associated with similar preexisting TAGs. PNPLA3(WT) overexpression resulted in increased [D17]oleic acid labeling of TAGs during 24 h, and after longer incubations their turnover was accelerated, effects not detected with PNPLA3(I148M). PNPLA3(I148M) localized more extensively to lipid droplets (LDs) than PNPLA3(WT), suggesting that the substitution alters distribution of PNPLA3 between LDs and endoplasmic reticulum/cytosol. This study reveals a function of PNPLA3 in FA-selective TAG remodeling, resulting in increased TAG saturation. A defect in TAG remodeling activity likely contributes to the TAG accumulation observed in cells expressing PNPLA3(I148M).
authors: Minerva Foundation Institute for Medical Research, Biomedicum 2U, FI-00290 Helsinki, Finland.
authors: Hanna
authors: H
authors: Ruhanen
authors: Julia
authors: J
authors: Perttilä
authors: Maarit
authors: M
authors: Hölttä-Vuori
authors: You
authors: Y
authors: Zhou
authors: Hannele
authors: H
authors: Yki-Järvinen
authors: Elina
authors: E
authors: Ikonen
authors: Reijo
authors: R
authors: Käkelä
authors: Vesa M
authors: VM
authors: Olkkonen
mesh_terms: D045744:Cell Line, Tumor; D005227:Fatty Acids / Q000378:metabolism; D022781:Hepatocytes / Q000201:enzymology*; D006801:Humans; D008049:Lipase / Q000502:physiology*; D066292:Lipid Droplets / Q000201:enzymology; D050356:Lipid Metabolism; D008565:Membrane Proteins / Q000502:physiology*; D020125:Mutation, Missense; D010743:Phospholipids / Q000378:metabolism; D021381:Protein Transport; D014280:Triglycerides / Q000378:metabolism*; D000217:Acyltransferases; D054512:Phospholipases A2, Calcium-Independent
chemical_list: D005227:Fatty Acids; D008049:Lipase; D008565:Membrane Proteins; D010743:Phospholipids; D014280:Triglycerides; C533682:PNPLA3 protein, human; D000217:Acyltransferases; D054512:Phospholipases A2, Calcium-Independent
keywords: adiponutrin; lipase; lipid droplet; lipidomics; nonalcoholic fatty liver disease; patatin-like phospholipase domain containing 3