A Sequence Variation (I148M) in PNPLA3 Associated with Nonalcoholic Fatty Liver Disease Disrupts Triglyceride Hydrolysis

Obesity and insulin resistance are associated with deposition of triglycerides in tissues other than adipose tissue. Previously, we showed that a missense mutation (I148M) in PNPLA3 (patatin-like phospholipase domain-containing 3 protein) is associated with increased hepatic triglyceride content in...

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Bibliographic Details
Published in:The Journal of biological chemistry 2010-02, Vol.285 (9), p.6706-6715
Main Authors: He, Shaoqing, McPhaul, Christopher, Li, John Zhong, Garuti, Rita, Kinch, Lisa, Grishin, Nick V., Cohen, Jonathan C., Hobbs, Helen H.
Format: Article
Language:English
Subjects:
Animals
Cell Line
Cell/Hepatocyte
Fatty Liver - genetics
Hepatocytes - metabolism
Humans
Hydrolysis
Lipase
Lipase - genetics
Lipid
Lipid/Lipase
Lipid/Triacylglycerol
Lipids
Lipolysis
Liver - metabolism
Membrane Proteins - genetics
Membrane/Lipids
Metabolism/Fatty Acid
Metabolism/Lipid
Metabolism/Lipogenesis
Mice
Mutation, Missense
Triglycerides - metabolism
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Summary:Obesity and insulin resistance are associated with deposition of triglycerides in tissues other than adipose tissue. Previously, we showed that a missense mutation (I148M) in PNPLA3 (patatin-like phospholipase domain-containing 3 protein) is associated with increased hepatic triglyceride content in humans. Here we examined the effect of the I148M substitution on the enzymatic activity and cellular location of PNPLA3. Structural modeling predicted that the substitution of methionine for isoleucine at residue 148 would restrict access of substrate to the catalytic serine at residue 47. In vitro assays using recombinant PNPLA3 partially purified from Sf9 cells confirmed that the wild type enzyme hydrolyzes emulsified triglyceride and that the I148M substitution abolishes this activity. Expression of PNPLA3-I148M, but not wild type PNPLA3, in cultured hepatocytes or in the livers of mice increased cellular triglyceride content. Cell fractionation studies revealed that ∼90% of wild type PNPLA3 partitioned between membranes and lipid droplets; substitution of isoleucine for methionine at position 148 did not alter the subcellular distribution of the protein. These data are consistent with PNPLA3-I148M promoting triglyceride accumulation by limiting triglyceride hydrolysis.
ISSN:0021-9258
1083-351X
DOI:10.1074/jbc.M109.064501