The membrane protein syntaxin 5 (STX5) is a key component of soluble N-ethylmaleimide-sensitive factor attachment protein (SNAP) receptor (SNARE) complexes that regulate cellular protein transport, vesicle docking, and membrane fusion. Syntaxin 5 protein is found as a 42 kDa ("long") protein localized to the Golgi complex and endoplasmic reticulum, and a “short” 35 kDa isoform localized primarily to the Golgi. Formation of the syntaxin 5 SNARE complex, which also includes proteins Sec22B, Bet1, GOSR1, GOSR2, and Ykt6, allows for regulation of ER-to-Golgi transport, intra-Golgi transport, and endosome-to-Golgi retrograde transport. Research studies indicate that the syntaxin 5 SNARE complex also plays an essential role in autophagy following autophagosome formation. Intracellular protein transport mediated by the syntaxin 5 complex is required for transport and localized activity of lysosomal proteases. The experimental reduction or deletion of syntaxin 5 complex components results in non-functional lysosomes and accumulation of autophagosomes.
