Regulation of membrane traffic between the ER and Golgi by SNARE-associated proteins, ZW10/RINT-1

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SNAREs (Soluble NSF attachment protein receptors) are involved in membrane fusion in the vesicular transport pathways in eukaryotic cells. We previously reported that syntaxin 18, a mammalian ER-localized SNARE, forms a complex with other SNAREs (BNIP1, p31, and Sec22b) and peripheral membrane proteins ZW10, and RINT-1). In the present study, we examined the function of a ZW10/RINT-1 complex in membrane traffic between the ER and the Golgi apparatus, and obtained the following results.1) Interaction between ZW10 and dynamitinProtein transport from the ER to the Golgi is mediated by the microtubule motor protein dynein-dynactin. We found that dynamitin, a subunit of the dynactin complex, and RINT-1 bind to the N-terminal region of ZW10 in a competitive manner. Evidence for the in vivo interaction of the N-terminal region of ZW10 with dynamitin was obtained by using nordihydroguaiaretic acid, a reagent that is known to stimulate dynein-dynactin-mediated processes. These results raise the possibility that ZW10 on the ER membrane is recruited to transport carriers through the interaction with dynamitin.2) Interaction of ZW10 with coatomer subunitsCOPI-coated vesicles are responsible for protein transport from the ER to the Golgi in mammalian cells. Binding experiments revealed that β,γ, and δ-COPI, weakly interact with ZW10, supporting the idea that ZW10 exists on COPI-coated vesicles and acts as a dynein-dynactin receptor.3) The NAG (Neuroblastoma amplified gene) product interacts with ZW10/RINT-1We discovered that NAG is a component of the syntaxin 18 complex. The N-terminal region of NAG interacts with the N-terminal region of p31, and the C-terminal region of NAG bind ZW10/RINT-1.