INIMEC - CONICET   05467
INSTITUTO DE INVESTIGACION MEDICA MERCEDES Y MARTIN FERREYRA
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
The Retromer Complex in the primitive parasite Giardia lamblia.
Autor/es:
MIRAS S.L.; RIVERO, MR.; ZAMPONI N.; RÓPOLO, A.S; TOUZ, MC
Lugar:
Ascochinga, Córdoba
Reunión:
Congreso; XXIV Reunión Anual de la Sociedad Argentina de Protozoología; 2010
Resumen:
Retromer is an evolutionary conserved multi-subunit
complex that mediates retrograde transport of transmembrane proteins from
endosomes to the trans-Golgi network
(TGN). The core of the retromer protein complex is associated with the
cytosolic face of endosomes and involves a large subcomplex comprised of Vps35,
Vps29, and Vps26 (Vacuolar protein sorting) along with a
smaller subcomplex form by SNX1 and SNX2 (Sorting Nexins). The
best characterized transmembrane proteins sorted by retromer are acid hydrolase
receptors like the vacuolar protein sorting 10 (Vps10) in the yeast Saccharomyces cerevisiae and the mannose 6-phosphate receptors (MPR) in mammals. Although
identified as an early-diverged protozoan, Giardialamblia shares many similarities with
higher eukaryotic cells including an internal membrane system, cytoskeleton, and
secretory pathways. However, because Giardia
does not contain a recognized Golgi apparatus or a typical endosome/lysosome
system, it is possible that this complex shows many particularities. By
searching the GiardiaDB, we found
genes that codify to the subcomplex gVps35, gVps29, and gVps26 but not SNX1 or
SNX2. Bioinformatic tools showed that these proteins exhibit structural
conservation with those of mammalian and yeast. Interestingly, a conserved
motif important for Vps35-Vps26 interaction was observed the Vps35 Giardias homologue. IFA and confocal
microscopy of stably transfected trophozoites over-expressing gVps-HA fusion
proteins, showed that the gVps localize mainly around the nuclei partially
colocalizing with the endoplasmic reticulum marker BIP (Immunoglobulin Binding
Protein). In addition, gVps35 and gVps 29 but not gVps26 also colocalized with
a lysosomal-like peripheral vacuoles marker. By yeast-two hybrid assays, we
found that gVps35 directly binds to Giardia
hydrolase receptor (gHR) and the gVps29 suggesting that the retrieval of the hydrolase
receptor is in charge of a retromer complex. The high degree of conservation of retromer implies
an early evolutionary appearance and functional indispensability. These results
will greatly increase our understanding of unique aspects of lysosomal
trafficking in Giardia and also shed
light on the mechanisms of protein targeting that have been acting over
hundreds of millions of years of eukaryotic evolution.