Leishmania mexicana mutants lacking glycosylphosphatidylinositol (GPI):protein transamidase provide insights into the biosynthesis and functions of GPI-anchored proteins.
The major surface proteins of the parasitic protozoon Leishmania mexicana are anchored to the plasma membrane by glycosylphosphatidylinositol (GPI) anchors. We have cloned the L. mexicana GPI8 gene that encodes the catalytic component of the GPI:protein transamidase complex that adds GPI anchors to nascent cell surface proteins in the endoplasmic reticulum. Mutants lacking GPI8 (DeltaGPI8) do not express detectable levels of GPI-anchored proteins and accumulate two putative protein-anchor precursors. However, the synthesis and cellular levels of other non-protein-linked GPIs, including lipophosphoglycan and a major class of free GPIs, are not affected in the DeltaGPI8 mutant. Significantly, the DeltaGPI8 mutant displays normal growth in liquid culture, is capable of differentiating into replicating amastigotes within macrophages in vitro, and is infective to mice. These data suggest that GPI-anchored surface proteins are not essential to L. mexicana for its entry into and survival within mammalian host cells in vitro or in vivo and provide further support for the notion that free GPIs are essential for parasite growth.
Hilley
J D
JD
Wellcome Centre for Molecular Parasitology, University of Glasgow, The Anderson College, Glasgow G11 6NU, Scotland, United Kingdom.
Zawadzki
J L
JL
McConville
M J
MJ
Coombs
G H
GH
Mottram
J C
JC
D000217:Acyltransferases / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D015139:Blotting, Southern; D015153:Blotting, Western; D020134:Catalytic Domain; D015815:Cell Adhesion Molecules / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism; D003001:Cloning, Molecular; D017261:Glycosylphosphatidylinositols / Q000378:metabolism*; D066298:In Vitro Techniques; D007274:Injections, Intraperitoneal; D007894:Leishmania mexicana / Q000235:genetics* / Q000378:metabolism / Q000472:pathogenicity; D017737:Macrophages, Peritoneal / Q000469:parasitology; D008565:Membrane Proteins / Q000096:biosynthesis / Q000378:metabolism; D051379:Mice; D008807:Mice, Inbred BALB C; D008969:Molecular Sequence Data; D016415:Sequence Alignment
D015815:Cell Adhesion Molecules; D017261:Glycosylphosphatidylinositols; D008565:Membrane Proteins; D000217:Acyltransferases; C081007:COOH-terminal signal transamidase