['The transport of endoplasmic reticulum (ER)-derived COPII vesicles toward the ER-Golgi intermediate compartment (ERGIC) requires cytoplasmic dynein and is dependent on microtubules. p150(Glued), a subunit of dynactin, has been implicated in the transport of COPII vesicles via its interaction with COPII coat components Sec23 and Sec24. However, whether and how COPII vesicle tether, TRAPP (Transport protein particle), plays a role in the interaction between COPII vesicles and microtubules is currently unknown.', 'We address the functional relationship between COPII tether TRAPP and dynactin. Overexpressed TRAPP subunits interfered with microtubule architecture by competing p150(Glued) away from the MTOC. TRAPP subunit TRAPPC9 bound directly to p150(Glued) via the same carboxyl terminal domain of p150(Glued) that binds Sec23 and Sec24. TRAPPC9 also inhibited the interaction between p150(Glued) and Sec23/Sec24 both in vitro and in vivo, suggesting that TRAPPC9 serves to uncouple p150(Glued) from the COPII coat, and to relay the vesicle-dynactin interaction at the target membrane.'] Does tRAPPC9 mediate the interaction between p150 and COPII vesicles at the target membrane?