The CORVET subunit Vps8 cooperates with the Rab5 homolog Vps21 to induce clustering of late endosomal compartments.
Membrane tethering, the process of mediating the first contact between membranes destined for fusion, requires specialized multisubunit protein complexes and Rab GTPases. In the yeast endolysosomal system, the hexameric HOPS tethering complex cooperates with the Rab7 homolog Ypt7 to promote homotypic fusion at the vacuole, whereas the recently identified homologous CORVET complex acts at the level of late endosomes. Here, we have further functionally characterized the CORVET-specific subunit Vps8 and its relationship to the remaining subunits using an in vivo approach that allows the monitoring of late endosome biogenesis. In particular, our results indicate that Vps8 interacts and cooperates with the activated Rab5 homolog Vps21 to induce the clustering of late endosomal membranes, indicating that Vps8 is the effector subunit of the CORVET complex. This clustering, however, requires Vps3, Vps16, and Vps33 but not the remaining CORVET subunits. These data thus suggest that the CORVET complex is built of subunits with distinct activities and potentially, their sequential assembly could regulate tethering and successive fusion at the late endosomes.
Markgraf
Daniel F
DF
University of Osnabrück, Department of Biology, Biochemistry Section, 49076 Osnabrück, Germany.
Ahnert
Franziska
F
Arlt
Henning
H
Mari
Muriel
M
Peplowska
Karolina
K
Epp
Nadine
N
Griffith
Janice
J
Reggiori
Fulvio
F
Ungermann
Christian
C
D001692:Biological Transport; D002451:Cell Compartmentation; D011992:Endosomes / Q000378:metabolism* / Q000648:ultrastructure; D006160:Guanosine Triphosphate / Q000378:metabolism; D007425:Intracellular Membranes / Q000378:metabolism; D057146:Multivesicular Bodies / Q000378:metabolism / Q000648:ultrastructure; D011485:Protein Binding; D021122:Protein Subunits / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000166:cytology / Q000378:metabolism* / Q000648:ultrastructure; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D033921:Vesicular Transport Proteins / Q000378:metabolism*; D020691:rab GTP-Binding Proteins / Q000378:metabolism*; D020696:rab5 GTP-Binding Proteins / Q000737:chemistry*
D021122:Protein Subunits; D029701:Saccharomyces cerevisiae Proteins; C103153:VPS8 protein, S cerevisiae; D033921:Vesicular Transport Proteins; D006160:Guanosine Triphosphate; C086866:VPS21 protein, S cerevisiae; D020691:rab GTP-Binding Proteins; D020696:rab5 GTP-Binding Proteins