INVESTIGADORES
TOUZ Maria carolina
artículos
Título:
A novel palmitoyl acyl transferase controls surface protein palmitoylation and cytotoxicity in Giardia lamblia.
Autor/es:
MARIA CAROLINA TOUZ; CONRAD JT; NASH TE
Revista:
MOLECULAR MICROBIOLOGY
Referencias:
Año: 2005 vol. 58 p. 999 - 1111
ISSN:
0950-382X
Resumen:
The intestinal protozoan parasite
Giardia lamblia
undergoes surface antigenic variation whereby one
of a family of structurally related variant-specific surface
proteins (VSPs) is replaced in a regulated process
by another antigenically distinct VSP. All VSPs
are type I membrane proteins that have a conserved
hydrophobic sequence terminated by the invariant
hydrophilic amino acids, CRGKA. Using transfected
Giardia
constitutively expressing HA-tagged VSPH7
and incubated with radioactive [
3
H]palmitate, we
demonstrate that the palmitate is attached to the Cys
in the conserved CRGKA tail. Surface location of
mutant VSPs lacking either the CRGKA tail or its Cys
is identical to that of wild-type VSPH7 but non-palmitoylated
mutants fail to undergo complement-independent
antibody specific cytotoxicity. In addition,
membrane localization of non-palmitoylated mutant
VSPH7 changes from a pattern similar to
rafts
to
nonraftsrafts
. Palmitoyl transferases (PAT), responsible
for protein palmitoylation in other organisms, often
possess a cysteine-rich domain containing a conserved
DHHC motif (DHHC-CRD). An open reading
frame corresponding to a putative 50 kDa
Giardia
PAT (gPAT) containing a DHHC-CRD motif was found
in the
Giardia
genome database. Expression of
epitope-tagged gPAT using a tetracycline inducible
vector localized gPAT to the plasma membrane, a
pattern similar to that of VSPs. Transfection with
gPAT antisense producing vectors inhibits gPAT
expression and palmitoylation of VSPs
in vitro
confirming
the function of gPAT. These results show that
VSPs are palmitoylated at the cysteine within the
conserved tail by gPAT and indicate an essential
function of palmitoylation in control of VSP-mediated
signalling and processing.