Lpcat3-dependent production of arachidonoyl phospholipids is a key determinant of triglyceride secretion

  1. Xin Rong
  2. Bo Wang
  3. Merlow M Dunham
  4. Per Niklas Hedde
  5. Jinny S Wong
  6. Enrico Gratton
  7. Stephen G Young
  8. David A Ford
  9. Peter Tontonoz  Is a corresponding author
  1. Howard Hughes Medical Institute, University of California, Los Angeles, United States
  2. Saint Louis University, United States
  3. University of California, Irvine, United States
  4. Gladstone Institute of Cardiovascular Disease, United States
  5. University of California, Los Angeles, United States

Abstract

The role of specific phospholipids in lipid transport has been difficult to assess due to an inability to selectively manipulate membrane composition in vivo. Here we show that the phospholipid remodeling enzyme lysophosphatidylcholine acyltransferase 3 (Lpcat3) is a critical determinant of triglyceride secretion due to its unique ability to catalyze the incorporation of arachidonate into membranes. Mice lacking Lpcat3 in the intestine fail to thrive during weaning and exhibit enterocyte lipid accumulation and reduced plasma triglycerides. Mice lacking Lpcat3 in the liver show reduced plasma triglycerides, hepatosteatosis, and secrete lipid-poor VLDL lacking arachidonoyl phospholipids. Mechanistic studies indicate that Lpcat3 activity impacts membrane lipid mobility in living cells, suggesting a biophysical basis for the requirement of arachidonoyl phospholipids in lipidating lipoprotein particles. These data identify Lpcat3 as a key factor in lipoprotein production and illustrate how manipulation of membrane composition can be used as a regulatory mechanism to control metabolic pathways.

Article and author information

Author details

  1. Xin Rong

    Department of Pathology and Laboratory Medicine, Howard Hughes Medical Institute, University of California, Los Angeles, Los Angeles, United States
    Competing interests
    No competing interests declared.
  2. Bo Wang

    Department of Pathology and Laboratory Medicine, Howard Hughes Medical Institute, University of California, Los Angeles, Los Angeles, United States
    Competing interests
    No competing interests declared.
  3. Merlow M Dunham

    Department of Biochemistry and Molecular Biology, Saint Louis University, St. Louis, United States
    Competing interests
    No competing interests declared.
  4. Per Niklas Hedde

    Laboratory of Fluorescence Dynamics, Biomedical Engineering Department, University of California, Irvine, Irvine, United States
    Competing interests
    No competing interests declared.
  5. Jinny S Wong

    Electron Microscopy Core, Gladstone Institute of Cardiovascular Disease, San Francisco, United States
    Competing interests
    No competing interests declared.
  6. Enrico Gratton

    Laboratory of Fluorescence Dynamics, Biomedical Engineering Department, University of California, Irvine, Irvine, United States
    Competing interests
    No competing interests declared.
  7. Stephen G Young

    Division of Cardiology, Department of Medicine, University of California, Los Angeles, Los Angeles, United States
    Competing interests
    Stephen G Young, Reviewing Editor, eLife.
  8. David A Ford

    Department of Biochemistry and Molecular Biology, Saint Louis University, St. Louis, United States
    Competing interests
    No competing interests declared.
  9. Peter Tontonoz

    Department of Pathology and Laboratory Medicine, Howard Hughes Medical Institute, University of California, Los Angeles, Los Angeles, United States
    For correspondence
    ptontonoz@mednet.ucla.edu
    Competing interests
    Peter Tontonoz, Reviewing editor, eLife.

Ethics

Animal experimentation: This study was performed in strict accordance with the recommendations in the Guide for the Care and Use of Laboratory Animals of the National Institutes of Health. All of the animals were handled according to approved institutional animal care and use committee (IACUC) protocols (99-131 and 2003-166) of the University of California Los Angeles

Copyright

© 2015, Rong et al.

This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.

Metrics

  • 4,804
    views
  • 1,386
    downloads
  • 167
    citations

Views, downloads and citations are aggregated across all versions of this paper published by eLife.

Download links

A two-part list of links to download the article, or parts of the article, in various formats.

Downloads (link to download the article as PDF)

Open citations (links to open the citations from this article in various online reference manager services)

Cite this article (links to download the citations from this article in formats compatible with various reference manager tools)

  1. Xin Rong
  2. Bo Wang
  3. Merlow M Dunham
  4. Per Niklas Hedde
  5. Jinny S Wong
  6. Enrico Gratton
  7. Stephen G Young
  8. David A Ford
  9. Peter Tontonoz
(2015)
Lpcat3-dependent production of arachidonoyl phospholipids is a key determinant of triglyceride secretion
eLife 4:e06557.
https://doi.org/10.7554/eLife.06557

Share this article

https://doi.org/10.7554/eLife.06557

Further reading

    1. Cell Biology
    2. Evolutionary Biology
    Paul Richard J Yulo, Nicolas Desprat ... Heather L Hendrickson
    Research Article

    Maintenance of rod-shape in bacterial cells depends on the actin-like protein MreB. Deletion of mreB from Pseudomonas fluorescens SBW25 results in viable spherical cells of variable volume and reduced fitness. Using a combination of time-resolved microscopy and biochemical assay of peptidoglycan synthesis, we show that reduced fitness is a consequence of perturbed cell size homeostasis that arises primarily from differential growth of daughter cells. A 1000-generation selection experiment resulted in rapid restoration of fitness with derived cells retaining spherical shape. Mutations in the peptidoglycan synthesis protein Pbp1A were identified as the main route for evolutionary rescue with genetic reconstructions demonstrating causality. Compensatory pbp1A mutations that targeted transpeptidase activity enhanced homogeneity of cell wall synthesis on lateral surfaces and restored cell size homeostasis. Mechanistic explanations require enhanced understanding of why deletion of mreB causes heterogeneity in cell wall synthesis. We conclude by presenting two testable hypotheses, one of which posits that heterogeneity stems from non-functional cell wall synthesis machinery, while the second posits that the machinery is functional, albeit stalled. Overall, our data provide support for the second hypothesis and draw attention to the importance of balance between transpeptidase and glycosyltransferase functions of peptidoglycan building enzymes for cell shape determination.

    1. Cell Biology
    Kaima Tsukada, Rikiya Imamura ... Mikio Shimada
    Research Article

    Polynucleotide kinase phosphatase (PNKP) has enzymatic activities as 3′-phosphatase and 5′-kinase of DNA ends to promote DNA ligation and repair. Here, we show that cyclin-dependent kinases (CDKs) regulate the phosphorylation of threonine 118 (T118) in PNKP. This phosphorylation allows recruitment to the gapped DNA structure found in single-strand DNA (ssDNA) nicks and/or gaps between Okazaki fragments (OFs) during DNA replication. T118A (alanine)-substituted PNKP-expressing cells exhibited an accumulation of ssDNA gaps in S phase and accelerated replication fork progression. Furthermore, PNKP is involved in poly (ADP-ribose) polymerase 1 (PARP1)-dependent replication gap filling as part of a backup pathway in the absence of OFs ligation. Altogether, our data suggest that CDK-mediated PNKP phosphorylation at T118 is important for its recruitment to ssDNA gaps to proceed with OFs ligation and its backup repairs via the gap-filling pathway to maintain genome stability.