PNPLA2 influences secretion of triglyceride-rich lipoproteins by human hepatoma cells
Patatin-like phospholipase domain-containing proteins (PNPLAs) are involved in triglyceride hydrolysis and lipid-droplet homeostasis in mice, but the physiological significance of the PNPLAs for triglyceride metabolism in human hepatocytes is unclear. Here, we investigate the roles of PNPLA2, PNPLA3...
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doaj-8a0183fcdfb4473294b095f0b296a77a2021-04-29T04:35:18ZengElsevierJournal of Lipid Research0022-22752019-06-0160610691077PNPLA2 influences secretion of triglyceride-rich lipoproteins by human hepatoma cellsApostolos Taxiarchis0Hovsep Mahdessian1Angela Silveira2Rachel M. Fisher3Ferdinand M. van't Hooft4Division of Cardiovascular Medicine, Department of Medicine Solna, Karolinska Institutet, Stockholm, Sweden; Center for Molecular Medicine, Karolinska Institutet, Stockholm, SwedenDivision of Cardiovascular Medicine, Department of Medicine Solna, Karolinska Institutet, Stockholm, Sweden; Center for Molecular Medicine, Karolinska Institutet, Stockholm, SwedenDivision of Cardiovascular Medicine, Department of Medicine Solna, Karolinska Institutet, Stockholm, Sweden; Center for Molecular Medicine, Karolinska Institutet, Stockholm, SwedenDivision of Cardiovascular Medicine, Department of Medicine Solna, Karolinska Institutet, Stockholm, Sweden; Center for Molecular Medicine, Karolinska Institutet, Stockholm, SwedenTo whom correspondence should be addressed.; Division of Cardiovascular Medicine, Department of Medicine Solna, Karolinska Institutet, Stockholm, Sweden; Center for Molecular Medicine, Karolinska Institutet, Stockholm, SwedenPatatin-like phospholipase domain-containing proteins (PNPLAs) are involved in triglyceride hydrolysis and lipid-droplet homeostasis in mice, but the physiological significance of the PNPLAs for triglyceride metabolism in human hepatocytes is unclear. Here, we investigate the roles of PNPLA2, PNPLA3, and PNPLA4 in triglyceride metabolism of human Huh7 and HepG2 hepatoma cells using gene-specific inhibition methods. siRNA inhibition of PNPLA3 or PNPLA4 is not associated with changes in triglyceride hydrolysis, secretion of triglyceride-rich lipoproteins (TRLs), or triglyceride accumulation. However, PNPLA2 siRNA inhibition, both in the absence and presence of oleate-containing medium, or treatment with the PNPLA2 inhibitor Atglistatin reduced intracellular triglyceride hydrolysis and decreased TRL secretion. In contrast, PNPLA2 inhibition showed no effects on lipid-droplet homeostasis, which is the primary physiological function of PNPLA2 in nonhepatic tissues. Moreover, confocal microscopy analysis found no clear evidence for the localization of PNPLA2 around lipid droplets. However, significant colocalization of PNPLA2 with the endoplasmic reticulum marker protein disulfide-isomerase was found in HepG2 and Huh7 cells with Rcoloc values of 0.61 ± 0.06 and 0.81 ± 0.05, respectively. In conclusion, PNPLA2 influences TRL secretion, but is not involved in lipid-droplet homeostasis in human hepatoma cells, a physiological role that is quite distinct from the metabolic function of PNPLA2 in nonhepatic tissues.http://www.sciencedirect.com/science/article/pii/S0022227520322471endoplasmic reticulumlipid dropletslipolysis and fatty acid metabolismlivernonalcoholic fatty liver diseasetriglycerides/diacylglycerol |
collection |
DOAJ |
language |
English |
format |
Article |
sources |
DOAJ |
author |
Apostolos Taxiarchis Hovsep Mahdessian Angela Silveira Rachel M. Fisher Ferdinand M. van't Hooft |
spellingShingle |
Apostolos Taxiarchis Hovsep Mahdessian Angela Silveira Rachel M. Fisher Ferdinand M. van't Hooft PNPLA2 influences secretion of triglyceride-rich lipoproteins by human hepatoma cells Journal of Lipid Research endoplasmic reticulum lipid droplets lipolysis and fatty acid metabolism liver nonalcoholic fatty liver disease triglycerides/diacylglycerol |
author_facet |
Apostolos Taxiarchis Hovsep Mahdessian Angela Silveira Rachel M. Fisher Ferdinand M. van't Hooft |
author_sort |
Apostolos Taxiarchis |
title |
PNPLA2 influences secretion of triglyceride-rich lipoproteins by human hepatoma cells |
title_short |
PNPLA2 influences secretion of triglyceride-rich lipoproteins by human hepatoma cells |
title_full |
PNPLA2 influences secretion of triglyceride-rich lipoproteins by human hepatoma cells |
title_fullStr |
PNPLA2 influences secretion of triglyceride-rich lipoproteins by human hepatoma cells |
title_full_unstemmed |
PNPLA2 influences secretion of triglyceride-rich lipoproteins by human hepatoma cells |
title_sort |
pnpla2 influences secretion of triglyceride-rich lipoproteins by human hepatoma cells |
publisher |
Elsevier |
series |
Journal of Lipid Research |
issn |
0022-2275 |
publishDate |
2019-06-01 |
description |
Patatin-like phospholipase domain-containing proteins (PNPLAs) are involved in triglyceride hydrolysis and lipid-droplet homeostasis in mice, but the physiological significance of the PNPLAs for triglyceride metabolism in human hepatocytes is unclear. Here, we investigate the roles of PNPLA2, PNPLA3, and PNPLA4 in triglyceride metabolism of human Huh7 and HepG2 hepatoma cells using gene-specific inhibition methods. siRNA inhibition of PNPLA3 or PNPLA4 is not associated with changes in triglyceride hydrolysis, secretion of triglyceride-rich lipoproteins (TRLs), or triglyceride accumulation. However, PNPLA2 siRNA inhibition, both in the absence and presence of oleate-containing medium, or treatment with the PNPLA2 inhibitor Atglistatin reduced intracellular triglyceride hydrolysis and decreased TRL secretion. In contrast, PNPLA2 inhibition showed no effects on lipid-droplet homeostasis, which is the primary physiological function of PNPLA2 in nonhepatic tissues. Moreover, confocal microscopy analysis found no clear evidence for the localization of PNPLA2 around lipid droplets. However, significant colocalization of PNPLA2 with the endoplasmic reticulum marker protein disulfide-isomerase was found in HepG2 and Huh7 cells with Rcoloc values of 0.61 ± 0.06 and 0.81 ± 0.05, respectively. In conclusion, PNPLA2 influences TRL secretion, but is not involved in lipid-droplet homeostasis in human hepatoma cells, a physiological role that is quite distinct from the metabolic function of PNPLA2 in nonhepatic tissues. |
topic |
endoplasmic reticulum lipid droplets lipolysis and fatty acid metabolism liver nonalcoholic fatty liver disease triglycerides/diacylglycerol |
url |
http://www.sciencedirect.com/science/article/pii/S0022227520322471 |
work_keys_str_mv |
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