Abstract
The plasma membrane is inhomogeneously organized containing both highly ordered and disordered nanodomains. 7-Ketocholesterol (7KC), an oxysterol formed from the nonenzymatic oxidation of cholesterol, is a potent disruptor of membrane order. Importantly, 7KC is a component of oxidized low-density lipoprotein and accumulates in macrophage and foam cells found in arterial plaques. Using a murine macrophage cell line, J774, we report that both IgG-mediated and phosphatidylserine-mediated phagocytic pathways are inhibited by the accumulation of 7KC. Examination of the well-studied Fcγ receptor pathway revealed that the cell surface receptor abundance and ligand binding are unaltered while downstream signaling and activation of spleen tyrosine kinase is not affected. However, while the recruitment of phospholipase Cγ1 was unaffected its apparent enzymatic activity was compromised resulting in sustained phosphatidylinositol 4,5-bisphosphate [PtdIns(4,5)P 2 ] levels and polymerized actin at the base of the phagocytic cup. Additionally, we found that 7KC prevented the activation of PLCβ downstream of the P2Y 6 G-protein coupled receptor and that 7KC impaired PLCγ activity in response to a direct elevation of cytosolic calcium induced by ionomycin. Finally, we demonstrate that 7KC partly attenuates the activity of rapamycin recruitable constitutively active PLCβ3. Together, our results demonstrate that the accumulation of 7KC impairs macrophage function by altering PtdIns(4,5)P 2 catabolism and, thus, impairing actin depolymerization required for the completion of phagocytosis.
Original language | English |
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Pages (from-to) | 591-604 |
Number of pages | 14 |
Journal | Traffic |
Volume | 19 |
Issue number | 8 |
DOIs | |
Publication status | Published - Aug 2018 |
Externally published | Yes |
Bibliographical note
Funding Information:information St. Michael's Hospital New Investigator Start-up Fund and a Discovery; Natural Science and Engineering Research Council of Canada (NSERC)S.M.L. is a recipient of the Alexander Graham Bell Scholarship from the Natural Science and Engineering Research Council of Canada (NSERC) and Ontario Graduate Scholarship Award. This work was supported by an St. Michael's Hospital New Investigator Start-up Fund and a Discovery from NSERC to G.D.F. We thank Sergio Grinstein (Hospital for Sick Children, Toronto, Canada) for helpful discussions. The Editorial Process File is available in the online version of this article.
Funding Information:
S.M.L. is a recipient of the Alexander Graham Bell Scholarship from the Natural Science and Engineering Research Council of Canada (NSERC) and Ontario Graduate Scholarship Award. This work was supported by an St. Michael's Hospital New Investigator Start-up Fund and a Discovery from NSERC to G.D.F. We thank Sergio Grin-stein (Hospital for Sick Children, Toronto, Canada) for helpful discussions.
Publisher Copyright:
© 2018 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd
ASJC Scopus Subject Areas
- Structural Biology
- Biochemistry
- Molecular Biology
- Genetics
- Cell Biology
PubMed: MeSH publication types
- Journal Article
- Research Support, Non-U.S. Gov't