Role of vesicle-associated syntaxin 5 in the assembly of pre-Golgi intermediates

Syntaxins are thought to function during vesicular transport as receptors on the target membrane and to contribute to the specificity of membrane docking and fusion by interacting with vesicle-associated receptors. Here, syntaxin 5 (Syn5) was shown to be an integral component of endoplasmic reticulum–derived transport vesicles. This pool, but not the target, Golgi-associated Syn5 pool, was essential for the assembly of vesicular-tubular pre-Golgi intermediates and the delivery of cargo to the Golgi. The requirement for vesicle-associated Syn5 in transport suggests a reevaluation of the basis for operation of the early secretory pathway. Syntaxin 5 is an essential membrane pro-tein that mediates transport between the endoplasmic reticulum (ER) and Golgi (1, 2). It belongs to the syntaxin family of SNAP-receptors (SNAREs), which are be-lieved to function as target membrane re-ceptors (t-SNAREs) that mediate dockin