Endosome maturation

Endosomes are organelles that are localized at the branch point between the plasma membrane and the vacuole. Early endosomes fuse with endocytic vesicles and then mature into late endosomes. These then fuse with the vacuole in yeast (or lysosome in metazoan cells). At endosomes, some membrane proteins are sorted into intraluminal vesicles for subsequent degradation inside vacuole, whereas others are sorted into tubules and transported back to the plasma membrane. The time-course of such cargo transport to the vacuole is seen in the images below.

We study how the fusion machinery is recruited and activated to make this possible. In particular, we are interested in the involved Rab GTPases, Rab5 (or Vps21) and Rab7 (or Ypt7), their GEFs (in particular the Mon1-Ccz1 complex) and the tethering complexes HOPS and CORVET. We use both live-cell imaging and reconstitution in the test tube to dissect this process.