TY - JOUR
T1 - A lipolytic lecithin:Cholesterol acyltransferase secreted by toxoplasma facilitates parasite replication and egress
AU - Pszenny, Viviana
AU - Ehrenman, Karen
AU - Romano, Julia D.
AU - Kennard, Andrea
AU - Schultz, Aric
AU - Roos, David S.
AU - Grigg, Michael E.
AU - Carruthers, Vern B.
AU - Coppens, Isabelle
N1 - Funding Information:
This work was supported by National Institutes of Health Grant AI060767 from NIAID (to I. C.) and in part by the Intramural Research Program Grant AI001018 from NIAID (to M. E. G.). The authors declare that they have no conflicts of interest with the contents of this article. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health.
PY - 2016/2/19
Y1 - 2016/2/19
N2 - The protozoan parasite Toxoplasma gondii develops within a parasitophorous vacuole (PV) in mammalian cells, where it scavenges cholesterol. When cholesterol is present in excess in its environment, the parasite expulses this lipid into the PV or esterifies it for storage in lipid bodies. Here, we characterized a unique T. gondii homologue of mammalian lecithin:cholesterol acyltransferase (LCAT), a key enzyme that produces cholesteryl esters via transfer of acyl groups from phospholipids to the 3-OH of free cholesterol, leading to the removal of excess cholesterol from tissues. TgLCAT contains a motif characteristic of serine lipases "AHSLG" and the catalytic triad consisting of serine, aspartate, and histidine (SDH) from LCAT enzymes. TgLCATis secreted by the parasite, but unlike other LCAT enzymes it is cleaved into two proteolytic fragments that share the residues of the catalytic triad and need to be reassembled to reconstitute enzymatic activity. TgLCAT uses phosphatidylcholine as substrate to form lysophosphatidylcholine that has the potential to disrupt membranes. The released fatty acid is transferred to cholesterol, but with a lower transesterification activity than mammalian LCAT. TgLCAT is stored in a subpopulation of dense granule secretory organelles, and following secretion, it localizes to the PV and parasite plasma membrane. LCAT-null parasites have impaired growth in vitro, reduced virulence in animals, and exhibit delays in egress from host cells. Parasites overexpressing LCAT show increased virulence and faster egress. These observations demonstrate that TgLCAT influences the outcome of an infection, presumably by facilitating replication and egress depending on the developmental stage of the parasite.
AB - The protozoan parasite Toxoplasma gondii develops within a parasitophorous vacuole (PV) in mammalian cells, where it scavenges cholesterol. When cholesterol is present in excess in its environment, the parasite expulses this lipid into the PV or esterifies it for storage in lipid bodies. Here, we characterized a unique T. gondii homologue of mammalian lecithin:cholesterol acyltransferase (LCAT), a key enzyme that produces cholesteryl esters via transfer of acyl groups from phospholipids to the 3-OH of free cholesterol, leading to the removal of excess cholesterol from tissues. TgLCAT contains a motif characteristic of serine lipases "AHSLG" and the catalytic triad consisting of serine, aspartate, and histidine (SDH) from LCAT enzymes. TgLCATis secreted by the parasite, but unlike other LCAT enzymes it is cleaved into two proteolytic fragments that share the residues of the catalytic triad and need to be reassembled to reconstitute enzymatic activity. TgLCAT uses phosphatidylcholine as substrate to form lysophosphatidylcholine that has the potential to disrupt membranes. The released fatty acid is transferred to cholesterol, but with a lower transesterification activity than mammalian LCAT. TgLCAT is stored in a subpopulation of dense granule secretory organelles, and following secretion, it localizes to the PV and parasite plasma membrane. LCAT-null parasites have impaired growth in vitro, reduced virulence in animals, and exhibit delays in egress from host cells. Parasites overexpressing LCAT show increased virulence and faster egress. These observations demonstrate that TgLCAT influences the outcome of an infection, presumably by facilitating replication and egress depending on the developmental stage of the parasite.
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U2 - 10.1074/jbc.M115.671974
DO - 10.1074/jbc.M115.671974
M3 - Article
C2 - 26694607
AN - SCOPUS:84969776689
SN - 0021-9258
VL - 291
SP - 3725
EP - 3746
JO - Journal of Biological Chemistry
JF - Journal of Biological Chemistry
IS - 8
ER -