Role of the SNARE protein Ykt6 in crinophagy

Autophagy ensures the degradation of damaged and unnecessary macromolecules, complexes and organelles in eukaryotic cells. In the main pathway, cargo is engulfed into double-membrane autophagosomes that will then fuse with lysosomes. Interestingly, a subset of secretory vesicles also fuse with lysosomes for degradation in a process called crinophagy. We have recently identified the SNARE proteins involved in autophagic (Syx17, SNAP29, Vamp7 and Ykt6) and crinophagic (Syx13, SNAP29 and Vamp7) vesicle fusions. In our ongoing project, we investigate the role of Ykt6 in crinpohagy. Using confocal microscopy, we observe clear fusion defects in Drosophila melanogaster salivary glands upon loss of Ykt6 function. Furthermore, we find that Ykt6 binds strongly to Syx13 in pulldown assays. These data together indicate the existence of an alternative, Ykt6 containing SNARE complex that promotes the fusion of secretory granules and lysosomes. Our further goal is to solve the structures of the autophagic and crinophagic SNARE complexes via X-ray crystallography. Our results will give new insights into the molecular mechanisms of vesicle fusions in these lysosomal degradation pathways.

Gábor Juhász, László Nyitray

Result_May 2020