Acidic clusters target transmembrane proteins to the contractile vacuole in Dictyostelium cells.
The mechanisms responsible for the targeting of transmembrane integral proteins to the contractile vacuole (CV) network in Dictyostelium discoideum are unknown. Here we show that the transfer of the cytoplasmic domain of a CV-resident protein (Rh50) to a reporter transmembrane protein (CsA) is sufficient to address the chimera (CsA-Rh50) to the CV. We identified two clusters of acidic residues responsible for this targeting, and these motifs interacted with the gamma-adaptin AP-1 subunit in a yeast protein-protein interaction assay. For the first time we report the existence of an indirect transport pathway from the plasma membrane to the CV via endosomes. Upon internalization, the small fraction of CsA-Rh50 present at the cell surface was first concentrated in endosomes distinct from early and late p80-positive endosomes and then slowly transported to the CV. Together our results suggest the existence of an AP-1-dependent selective transport to the contractile vacuole in Dictyostelium.
Université de Genève, Centre Médical Universitaire, Département de Physiologie Cellulaire et Métabolisme, CH-1211 Genève 4, Switzerland.
Valentina
V
Mercanti
Cédric
C
Blanc
Yaya
Y
Lefkir
Pierre
P
Cosson
François
F
Letourneur
D033982:Adaptor Protein Complex gamma Subunits / Q000502:physiology; D000595:Amino Acid Sequence; D000818:Animals; D015815:Cell Adhesion Molecules / Q000235:genetics / Q000502:physiology*; D002462:Cell Membrane / Q000502:physiology; D004023:Dictyostelium / Q000166:cytology* / Q000201:enzymology / Q000502:physiology*; D011992:Endosomes / Q000502:physiology; D008969:Molecular Sequence Data; D015800:Protozoan Proteins / Q000235:genetics / Q000502:physiology*; D016415:Sequence Alignment; D015398:Signal Transduction / Q000502:physiology; D014617:Vacuoles / Q000502:physiology*
D033982:Adaptor Protein Complex gamma Subunits; D015815:Cell Adhesion Molecules; D015800:Protozoan Proteins; C052291:cell cohesion molecule, Dictyostelium