Figure 1.

SNARE proteins in the fusion of autophagosomes with lytic compartments. In yeast, activity of the Atg14-containing Phosphatidylinositol (PI) 3-kinase complex I is required for the efficient recruitment of Ypt7 onto autophagosomal membranes. Vam3, Vti1 and Vam7 on the vacuolar membrane create a SNARE (Soluble N-ethylmaleimide sensitive factor attachment protein receptor) bundle with Ykt6 on the autophagosomal membrane, which is aided by Ypt7 on both membranes and the HOPS (homotypic fusion and protein sorting) tethering complex to allow fusion. In Drosophila, Ykt6 creates a fusion incompetent prefusion SNARE bundle with Stx17 and Snap29, which then is replaced by Vamp7 to form the fusion competent SNARE bundle. In mammalian cells, YKT6 and STX17 localize on autophagosomal membranes and create two separate SNARE bundles for autophagosome-lysosome fusion, with STX7 and SNAP29, and VAMP8 and SNAP29, respectively.