YKT6 as a second SNARE protein of mammalian autophagosomes

Mammalian autophagosomes possess the Qa-SNARE STX17 (syntaxin 17) for fusion with lysosomes. However, STX17 is not absolutely required for fusion because STX17 knockout cells partially retain autophagosome-lysosome fusion activity. We recently identified YKT6, an R-SNARE, as another autophagosomal SNARE protein that acts independently of STX17 in mammals. Here, we discuss the features and functions of autophagosomal SNARE proteins by comparing STX17 and YKT6. Abbreviations: SNARE, soluble N-ethylmaleimide-sensitive factor attachment protein receptor; STX17, syntaxin 17.