STX17

STX17, or syntaxin-17, is a human protein encoded by the STX17 gene. It belongs to the syntaxin family of SNARE proteins that mediate vesicle fusion. STX17 localizes to autophagosomal membranes, where it is anchored by a C-terminal transmembrane domain and uses its cytosolic SNARE motif to participate in membrane fusion.

Functionally, STX17 is a key mediator of autophagosome–lysosome fusion. It forms a SNARE complex with SNAP29 and VAMP7 or VAMP8, enabling degradation of autophagic cargo. The protein is required for autophagosome maturation, and depletion of STX17 disrupts this fusion step, leading to the accumulation of unfused autophagosomes.

STX17 also participates in mitophagy, contributing to the selective autophagic clearance of damaged mitochondria by coordinating autophagosome formation and fusion events involved in mitochondrial turnover.

Clinical and research relevance is linked to the broader role of autophagy in cellular homeostasis. Dysregulation of autophagic flux has been associated with neurodegenerative diseases and cancer, and perturbations in STX17-dependent pathways may influence disease processes. As a result, STX17 is a focus in studies of vesicle trafficking and autophagy regulation.

Genetically and evolutionarily, STX17 is conserved across metazoans as part of the SNARE protein family involved in intracellular trafficking. In humans, it is one of several syntaxin family members that coordinate vesicle fusion events across different membranes. The discovery of STX17 highlighted its specific localization to autophagosomes and its essential role in autophagosome maturation.