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Overexpression of CD36 and acyl-CoA synthetases FATP2, FATP4 and ACSL1 increases fatty acid uptake in human hepatoma cells.

Krammer J, Digel M, Ehehalt F, Stremmel W, Füllekrug J, Ehehalt R - Int J Med Sci (2011)

Bottom Line: FATP2 had the highest effect on B12 uptake of all proteins tested.Whereas [3H]-oleic acid uptake was increased after overexpression, CD36 had no effect on B12 uptake.Therefore these molecules are potential targets for treatment of nonalcoholic fatty liver disease (NAFLD) or steatohepatitis (NASH).

View Article: PubMed Central - PubMed

Affiliation: Department of Gastroenterology, Hepatology and Infectious Diseases, University Hospital Heidelberg, Im Neuenheimer Feld 410, 69120 Heidelberg, Germany.

ABSTRACT

Background: Understanding the mechanisms of long chain fatty acid (LCFA) uptake in hepatic cells is of high medical importance to treat and to prevent fatty liver disease (FLD). ACSs (Acyl-CoA synthetases) are a family of enzymes that catalyze the esterification of fatty acids (FA) with CoA. Recent studies suggest that ACS enzymes drive the uptake of LCFA indirectly by their enzymatic activity and could promote special metabolic pathways dependent on their localization.The only protein located at the plasma membrane which has consistently been shown to enhance FA uptake is CD36.

Aims: The current study investigated whether ACSs and CD36 could regulate hepatic LCFA uptake.

Methods and results: FATP2 and FATP4 were both localized to the ER of HuH7 and HepG2 cells as shown by double immunofluorescence in comparison to marker proteins. ACSL1 was located at mitochondria in both cell lines. Overexpression of FATP2, FATP4 and ACSL1 highly increased ACS activity as well as the uptake of [3H]-oleic acid and fluorescent Bodipy-C12 (B12) fatty acid. Quantitative FACS analysis showed a correlation between ACS expression levels and B12 uptake. FATP2 had the highest effect on B12 uptake of all proteins tested. CD36 was mainly localized at the plasma membrane. Whereas [3H]-oleic acid uptake was increased after overexpression, CD36 had no effect on B12 uptake.

Conclusion: Uptake of LCFA into hepatoma cells can be regulated by the expression levels of intracellular enzymes. We propose that ACS enzymes drive FA uptake indirectly by esterification. Therefore these molecules are potential targets for treatment of nonalcoholic fatty liver disease (NAFLD) or steatohepatitis (NASH).

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Related in: MedlinePlus

GFP-CD36 transiently cotransfected with PLAP in HepG2 cells and clustered with mouse anti PLAP. CD36 flags typical branches on the cell surface compatible with the plasma membrane (A). There was no matching of CD36 staining with ER (mRFP) (B) or lipid droplet (adipophilin-mRFP1) marker proteins (C). Results are representative for HuH7 cells as well. Bar: 10 µm.
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Figure 4: GFP-CD36 transiently cotransfected with PLAP in HepG2 cells and clustered with mouse anti PLAP. CD36 flags typical branches on the cell surface compatible with the plasma membrane (A). There was no matching of CD36 staining with ER (mRFP) (B) or lipid droplet (adipophilin-mRFP1) marker proteins (C). Results are representative for HuH7 cells as well. Bar: 10 µm.

Mentions: Figure 4 shows that CD36 could be co-localized with PLAP, a marker for plasma membrane. The staining presented the complete size of the cell and typical branches on the cell surface. This localization is in line with previous results in COS cells 19. No co-localization with mitochondria (mito-RFP), ER (mRFP-Sec61ß), lipid droplets (ADP-mRFP1) and peroxisomes (peroxisomal-mRFP1) could be detected.


Overexpression of CD36 and acyl-CoA synthetases FATP2, FATP4 and ACSL1 increases fatty acid uptake in human hepatoma cells.

Krammer J, Digel M, Ehehalt F, Stremmel W, Füllekrug J, Ehehalt R - Int J Med Sci (2011)

GFP-CD36 transiently cotransfected with PLAP in HepG2 cells and clustered with mouse anti PLAP. CD36 flags typical branches on the cell surface compatible with the plasma membrane (A). There was no matching of CD36 staining with ER (mRFP) (B) or lipid droplet (adipophilin-mRFP1) marker proteins (C). Results are representative for HuH7 cells as well. Bar: 10 µm.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3198256&req=5

Figure 4: GFP-CD36 transiently cotransfected with PLAP in HepG2 cells and clustered with mouse anti PLAP. CD36 flags typical branches on the cell surface compatible with the plasma membrane (A). There was no matching of CD36 staining with ER (mRFP) (B) or lipid droplet (adipophilin-mRFP1) marker proteins (C). Results are representative for HuH7 cells as well. Bar: 10 µm.
Mentions: Figure 4 shows that CD36 could be co-localized with PLAP, a marker for plasma membrane. The staining presented the complete size of the cell and typical branches on the cell surface. This localization is in line with previous results in COS cells 19. No co-localization with mitochondria (mito-RFP), ER (mRFP-Sec61ß), lipid droplets (ADP-mRFP1) and peroxisomes (peroxisomal-mRFP1) could be detected.

Bottom Line: FATP2 had the highest effect on B12 uptake of all proteins tested.Whereas [3H]-oleic acid uptake was increased after overexpression, CD36 had no effect on B12 uptake.Therefore these molecules are potential targets for treatment of nonalcoholic fatty liver disease (NAFLD) or steatohepatitis (NASH).

View Article: PubMed Central - PubMed

Affiliation: Department of Gastroenterology, Hepatology and Infectious Diseases, University Hospital Heidelberg, Im Neuenheimer Feld 410, 69120 Heidelberg, Germany.

ABSTRACT

Background: Understanding the mechanisms of long chain fatty acid (LCFA) uptake in hepatic cells is of high medical importance to treat and to prevent fatty liver disease (FLD). ACSs (Acyl-CoA synthetases) are a family of enzymes that catalyze the esterification of fatty acids (FA) with CoA. Recent studies suggest that ACS enzymes drive the uptake of LCFA indirectly by their enzymatic activity and could promote special metabolic pathways dependent on their localization.The only protein located at the plasma membrane which has consistently been shown to enhance FA uptake is CD36.

Aims: The current study investigated whether ACSs and CD36 could regulate hepatic LCFA uptake.

Methods and results: FATP2 and FATP4 were both localized to the ER of HuH7 and HepG2 cells as shown by double immunofluorescence in comparison to marker proteins. ACSL1 was located at mitochondria in both cell lines. Overexpression of FATP2, FATP4 and ACSL1 highly increased ACS activity as well as the uptake of [3H]-oleic acid and fluorescent Bodipy-C12 (B12) fatty acid. Quantitative FACS analysis showed a correlation between ACS expression levels and B12 uptake. FATP2 had the highest effect on B12 uptake of all proteins tested. CD36 was mainly localized at the plasma membrane. Whereas [3H]-oleic acid uptake was increased after overexpression, CD36 had no effect on B12 uptake.

Conclusion: Uptake of LCFA into hepatoma cells can be regulated by the expression levels of intracellular enzymes. We propose that ACS enzymes drive FA uptake indirectly by esterification. Therefore these molecules are potential targets for treatment of nonalcoholic fatty liver disease (NAFLD) or steatohepatitis (NASH).

Show MeSH
Related in: MedlinePlus